DEPARTMENT OF THE INTERIOR

UNITED STATES GEOLOGICAL SURVEY " ~

GEORGE OTIS SMITH, DIRECTOR

BULLETIN 398

GEOLOGY AND OIL RESOURCES

OF THE

COALINGA DISTRICT

CALIFORNIA

BY

RALPH ARNOLD AND ROBERT ANDERSON

WITH A REPORT ON THE

CHEMICAL AND PHYSICAL PROPERTIES OF THE OILS

BY

IRVING C. ALLEN

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1910

CONTENTS.

Page.

Introduction............................................................... 11

General.............................................................. 11

Plan of the present work............................................... 12

Acknowledgments.................................................... 14

Advantage of cooperation among operators............................... 15

Previous knowledge of the geology ..................................... 16

Geography and topography................................................ 18

Definition of place names........................................ ......... 18

Location............................................................. 25

Climate, drainage, and vegetation...................................... 26

Relief............................... ............................... 26

General topographic features........................................ 26

Diablo Range ................. .................................. 27

General features................................................ 27

Distinction from foothills........................... ; ......:... 28

Outcrops and slopes............................................ 28

Constituent ridges............................................. 28

Joaquin Ridge.................................................. 29

Juniper Ridge and Curry Mountain................:........... 30

Reef Ridge................................................... 30

Castle Mountain............................................... 31

Avenal Ridge............................................. 1... 31

The foothills...................................................... 32

General description........................................... 32

Hills north and south of Los Gatos Creek ....................... 33

Hills around the end of Joaquin Ridge......................... 34

Alcalde Hills.................................................. 34

Jacalitos and Kreyenhagen hills............................... 35

Kettleman Hills............................................... 36

Hills around McLure Valley................................... 37

The broad valleys................................................. 38

Tulare Lake...................................................... 38

Drainage courses................................................... 39

Character of streams.......................................... 39

Los Gatos Creek............................................... 40

Waltham Creek............................................... 41

Jacalitos Creek................................................ 41

Avenal Creek. ...................... s.....'.................... 41

Other main streams........................................... 42

Minor drainage courses........................................ 42

Physiographic development............................................. 42

Factors influencing development................................... 42

History of physiographic development.............................. 43

3
4 CONTENTS.

Page.

Geology................... .....................^........................... 46

General statement..................................................... 46

Rocks important with relation to petroleum.............................. 49

Economic deposits other than petroleum................................. 49

Sedimentary formations ........ ..................../.................. 50

Franciscan formation (Jurassic?) .................................... 50

General description........................................... 50

Importance with relation to petroleum........................... 51

Knoxville-Chico rocks (Cretaceous)................................. 51

General description........................................... 51

Lower division................................................ 52

Distribution and character................................... 52

Evidence of age. ....... 1.................................. 53

Middle division............................................... 54

Distribution and character.................................. 54

Evidence of age........................................... 55

Upper division...................:.......:..................... 55

Distribution and character................................... 55

Evidence of age. .........................................v 60

Importance with relation to petroleum............................ 61

Tejon formation (Eocene)...... ; ................................... 62

General description........................................... 62

Distribution and local character................................. 64

Tejon north of Pleasant Valley............................... 64

Tejon south of Los Gatos Creek............................... 66

Tejon along Reef Ridge.....:.............................. 67

Fossils and age..............:..................-.............. 70

List of fossils............................................... 70

Other species collected.................................... 72

Faunal relations and age................................... 72

Importance with relation to petroleum........................... 74

General description of the post-Eocene formations ..................... 75

Introduction................................................. 75

Description of the series in the north............................ 76

Description of the series in the south............................ 76

Previous correlation........................................... 77

The McKittrick formation south of this district................... 79

Vaqueros sandstone (lower Miocene)................................. 80

General description........................................... 80

Distribution and local character................................. 80

General statement.......................................... 80

Vaqueros north of Pleasant Valley.......................... 81

Vaqueros in the Alcalde Hills............................... 82

Vaqueros in the Jacalitos Hills.............................. 83

Vaqueros on Reef Ridge................................... 83

Fossils and age.................................................. 84

List of fossils ............................................. 84

Other species collected.................................... 87

Faunal relations and age................................... 87

Importance with relation to petroleum........................... 88

Santa Margarita (?) formation (upper middle Miocene)............... 88

General description........................................... 88
CONTENTS. 0

'Geology Continued.

Sedimentary formations Continued.

Santa Margarita (?) formation Continued. Page.

Distribution and local character................................. 89

Santa Margarita (?) in the Coalinga field.................... 89

Santa Margarita (?) in the Rreyenhagen field................. 90

Fossils and age................................................... 94

List of fossils............................................... 94

Faunal relations and age................................... 95

Importance with relation to petroleum........................... 95

Jacalitos formation (early upper Miocene)............................. 96

Definition and general description.............................. 96

Means of recognition........................................... 96

Stratigraphic relations.......................................... 97

Distribution and local character................................. 98

Kreyenhagen Hills.......................................... 98

Region of McLure Valley................................... 104

Jacalitos Hills............................................. 105

Alcalde Hills............................................... 106

Area north of Pleasant Valley.............................. 107

Fossils and age................................................ 108

Fossils.........:.......................................... 108

Faunal zones............................................... Ill

Faunal'relations and age................................... Ill

Importance with relation to petroleum........................... 113

Etchegoin formation (uppermost Miocene)............................. 113

Definition.................................................... 113

Original description........................................ 113

Present definition......................................... 114

Base of the formation...................................... 114

Top of the formation........................................ 115

General description............................................. 116

Distribution and local character................................. 117

Etchegoin in the Coalinga field.............................. 117

Etchegoin in the White Creek baein......................... 117

Etchegoin in Waltham Valley .............................. 118

Etchegoin in the Kreyenhagen Hills......................... 118

Etchegoin in McLure Valley............................... 120

Etchegoin in the Kettleman Hills........................... 120

Fossils, origin, and age.......................................... 124

Fossils.................................................... 124

Faunal zones............................................... 136

Origin of the Etchegoin..................................... 137

Correlation and age......................................... 138

Importance with relation to petroleum........................... 140

Tulare formation (upper Pliocene-lower Pleistocene).................. 140

Definition and general description........................'...... 140

Previous descriptions.......................;.................. 141

Distribution and local character................................. 143

Tulare in the Kettleman Hills............................... 143

Tulare iu the Kreyenhagen and Jacalitos Hills............... 148

Tulare in the Guijarral Hills................................ 149

Origin of the formation.................... .....................: 149
6 CONTENTS.

Geology Continued.

Sedimentary formations Continued.

Tulare formation Continued. Page.

Fossils and age................................................ 153

Fossils.................................................... 153

Faunal relations and age................................... 153

Importance with relation to petroleum........................... 154

Terrace deposits and alluvium (Quaternary)......................... 154

Character and extent.......................................... 154

Valley alluvium................................................ 155

Loose soil...................................................... 156

Stream conglomerate on White Creek........................... 156

Igneous rocks. '. ....................................................... 157

Serpentine...... 1................................................. 157

Soda syenite from White Creek...................................... 158

Structure...........................................:.................. 160

Cross structures and their topographic influence..................... 160

Periods of movement and the effects on formations of different age..... 162

Thickness of-the sedimentary strata.................................. 163

Unconformities................. .^. ...........................*........ 164

Main lines of structure.............................................. 165

Coalinga anticline and syncline...:............................. 165

Structure in the basin of Los Gatos and White creeks............ 166

Zone of Alcalde Canyon........................................ 166

Structure in the Jacalitos Hills.................................. 167

Castle Mountain fault zone...................................... 167

Pyramid Hills anticline......................................... 167

Avenal syncline............................................... 168

Diablo anticline............................................... 168

Character of the folds and faults..................................... 168

Geologic history..............'.......................................... 169

General features................................................... 169

Jurassic (?) period.................................................. 169

Cretaceous period................................................. 170

Early Tertiary period.............................................. 171

Middle Tertiary period............................................ 173

Late Tertiary and early Quaternary period........................... 176

Late^Quaternary period.............................................. 179

The developed territory.................................................... 179

History of development in the Coalinga district .......................... 179

Areas discussed........................................................ 182

Occurrence of the petroleum. ........................................... 182

Formations in which petroleum occurs.............................. 182

Oil zones.......................................................... 183

General description............................................. 183

Chico oil zone................................................. 183

' Tejon oil zone.................................................. 183

Vaqueros oil 'zones.............................................. 184

Santa Margarita (?) oil zone..................................... ]84

Jacalitos oil zones, zones A and B.............................. 185

Factors influencing accumulation................................... 185

Factors influencing gravity.......................................... 186

 Relations of water to oil............................................ 187
CONTENTS. 7

The developed territory Continued. Page.

Origin of the petroleum................................................. 188

 Contour map of the Coalinga field ...................................... 189

Explanation....................................................... 189

Use of the map.................................................... 190

Basis of the contour map........................................... 192

Difficulties of preparation and degree of accuracy.................... 192

Details of the productive areas............................................ 193

Oil City field......:.........................:...................... 193

Location...................................................... 193

Geology and structure. ......................................... 193

Geology of the wells............................................ 194

Product...................................................... 195

Eastside field...................................................... 196

Peerless-British Consolidated-T. C. area ......................... 196

Location................................................... 196

,Geology of the wells...................................'..... 19G

Product.................................................. 198

Technology.......:.......J................................ 199

Standard-Caribou-British Consolidated area ..................... 199

Location.................................................. 199

Geology of the wells........................................ 199

Product.................................................. 200

Standard-California Oilfields (sec. 27) area....................... 201

Location................................................... 201

Geology of the wells........................................ 201

Product.................................................. 202

California Oilfields (sec. 34) Coalinga Mohawk area............. 203

Location................................................... 203

Geology of the wells........................................ 203

Product.................................................. 204

Standard-Stockholders area.................................... 205

Location.................................................. 205

Geology of the wells........................................ 205

Product.................................................. 206

Westside field...................................................... 206

Call-Confidence area............................................ 206

Location.................................................. 206

Geology of the wells........................................ 206

Product.................................................. 208

Mercantile Crude-S. W. & B. area.............................. 208

Location.................................................. 208

Geology of the wells........................................ 209

Product.................................................. 210

Zier-Porter & Scribner-M., K. & T. area.......................... 210

Location.................................................. 210

Geology of the wells............................:............. 211

Product.................................................. 213

Associated-Caledonian-Union area.............................. 213

Location.................................................. 213

Structure.................................................. 213

Geology of the wells........................................ 214

Product.................................................. ' 216
8 CONTENTS.

The developed territory Continued.

Details of the productive areas Continued.

Westside field Continued. Page.

Area between Waltham Creek and San Joaquin Valley coal mine.. 217

Location.. ................................................. 217

Geology.................................................. 217

Structure.................................................. 220

Geology of the wells........................................ 222'

Product...:.............................................. 226

Area embracing sec. 2, T. 21 S., R. 14 E....................... 226

Location.................................................. 226

Geology of the wells........................................ 226

Product.................................................. 227

Kreyenhagen field................................................... 227

Location................ 1...................................... 227

Contour map................................................... 228

General geology and occurrence of oil........................... 228

Groups of wells discussed....................................... 229

Geology of wells in the Tejon formation......................... 229

Geology 'of wells in formations above the Tejon................... 231

Kettleman Hills field............................................... 232

Location...................................................... 232

Geology and indications of oil................................... 232

Geology of the wells............................................ 232

Conclusions concerning future development.................................. 233

General statement...................................................... 233

Territory northwest of Eastside field..................................... 235

Region of the Eastside field............................................. 235

Region of Anticline Ridge and Guijarral Hills............................ 236

Region of the Westside field............................................. 237

Region of the Jacalitos anticline ........................................ 238

Region of Reef Ridge south to Dagany Gap............................. 239

Region of the Kettleman Hills......................................... 241

Areas classified as mineral land in the Coalinga district........................ 245

Production and estimated supply........................................... 246

Transportation facilities..................................................... 247

Oil companies and oil wells in the Coalinga district........................... 248

Chemical and physical examination of the petroleums of the Coalinga district,

by Irving C. Alien...................................................... 264

Index.................................................................... 345
ILLUSTRATIONS.

PLATE I. Geologic and structural map of the Coalinga district......... In pocket.

II. A, Arid foothill belt of .Tertiary formations; B, Monocline of Tertiary strata in Jacalitos Hills......................'............ 26

III. Oil City field and ridge of the Coalinga anticline.................. 32

IV. A, Stream terraces along Zapato Creek; B, Hard reddish-brown 

sandstone concretions weathering out of massive Upper Cretaceous sandstone. ........................---. - 40

V. A, Western face of Curry Mountain, formed by Cretaceous strata; 

B, Unconformity between Tejon formation and Vaqueros sandstone.. ........................................................ 54

VI. A, Sandstone dikes in petroliferous shale of the Tejon formation; 

B, Petroliferous shale and sandstone of Tejon formation broken 

by local fault................................................. 66

VII. A, "Reef beds" of Vaqueros sandstone overlying overturned

shales of the Tejon formation; 'B, Diagram of Plate VII, A ..... 80

VIII. " Reef beds" of Vaqueros sandstone forming scarp of Reef Ridge .. 80 

IX: A, View looking south down Avenal Creek; B, Bed of sand dollars

in pebbly sand of Etchegoin formation.......................... 82

X. Characteristic bluffs, with strike face and dip slope, formed by

varicolored Miocene sandstone, shale, and conglomerate........ 90

XI. A, Avenal Ridge and Tent Hills, seen from northeast across 

McLure Valley; B, Siliceous shale of Santa Margarita (?) formation at head of McLure Valley ................................ 92

XII. A, Arroyo cutting Pleistocene sand and clay that cover San Joaquin 

Valley; B, Fossil Pecten estrellanus bed in Santa Margarita (?) 

formation, 10 miles north of Coalinga.......................... 94

XIII. A, Overturned shales of Tejon formation in axis of Coalinga anticline; B, Diagram of Plate XIII, A. .......................... 162

XIV. Basal Vaqueros oil sands on axis of Coalinga anticline............ 162

XV. Geologic and topographic contour map of the Coalinga oil field,

Fresno County, Cal...................................... In pocket.

XVI. Hypothetical section along line B-BX on contour map, Plate XV.. 190 

XVII. Regularly dipping beds of Santa Margarita (?) and Jacalitos formation's on northeast flank of Coalinga anticline in Eastside field.... 190

XVIII. View looking southeast down plunging axis of Coalinga anticline

in Eastside field ............................................ 190

XIX. Hypothetical section along line C-C' on contour map, Plate XV... 192

XX. Hypothetical section along line D-DX on contour map, Plate XV.. 192

XXI. Hypothetical section along line E-EX on contour map, Plate XV.. 192

XXII. Contour map of the Kreyenhagen field.......................... 228

XXIII. Chico fossils.................................................... 274

XXIV. Tejou Pelecypoda.............................................. 276

9
10 ILLUSTRATIONS.

Page. 

PLATE XXV. Tejon Pelecypoda............................................. 280

XXVI. Tejon Gasteropoda and Echinodermata ....................... 284

XXVII. Vaqueros fossils..... r ........................................ 288

XXVIII. Vaqueros fossils.............................................. 290

XXIX. Vaqueros fossils................................................ 292

XXX. Vaqueros fossils................ ; ............................. 294

XXXI. Vaqueros fossils.....,..........'............................. 29G

XXXII. Santa Margarita fossils......................................... 298

XXXIII. Santa Margarita and Jacalitos fossils........................... 300

XXXIV. Santa Margarita and Jacalitos fossils........................... 302

XXXV. Jacalitos Echinodermata...................................... 304

XXXVI. Jacalitos fossils. ............................................. 306

XXXVII. Jacalitos fossils.............................................. 308

XXXVIII. Jacalitos Pelecypoda......................................... 310

XXXIX. Etchegoin fossils.............................................. 312

XL. Etchegoin fossils.............................................. 314

XLI. Etchegoin fossils................................:............. 316

XLII. Etchegoin fossils'. ........................................ .*... 318

XLIII. Jacalitos and Etchegoin fossils................................ 320

XLIV, Etchegoin fossils. ........................................... 322,

XLV. Etchegoin fossils. ..............:............................ 324'

XLVI. Etchegoin fossils............................................ 326

XLVII. Etchegoin and Tulare fossils.................................... 328

XLVIII. Etchegoin fossils............................................. 332

XLIX. Etchegoin fossils. ........................................... 334

L. Etchegoin Echinodermata.................................... 338

LI. Etchegoin fossils. ........................................... 340

LII. Tulare fossils................................................ 342

FIGURE 1. Index map of a part of southern California........................ 12

2. Generalized columnar geologic section of the sedimentary rocks of

the Coalinga district........................................... 47

3. Section of the Santa Margarita (?), Vaqueros, and Tejon formations

along the west side of Big Tar Canyon.......................... 68

4. Section of Etchegoin and Jacalitos formations in Kreyenhagen Hills

east of Zapato Creek, along line M-W on geologic map (PI. I)... 100

5. Section of Tulare and Etchegoin formations along road 6 miles from 

northwest end of Kettleman Hills on southwest flank of Coalinga 

anticline, along line N-N' on geologic map (PI. I).............. 122

6. Geologic sections across Coalinga district.......................... 161

7. Hypothetical section along line A-AX , Plate XV, from the Westside

to the Eastside field........................................... 190

8. Hypothetical section along line F-FX , Plate XV, from Anticline

Canyon to California Oil and Gas Company's well No. 1.......... 191

9. Small picnorneter. .................................. ^........... 264
GEOLOGY AND OIL RESOURCES OF THE COALINGA 

DISTRICT, CALIFORNIA.

By RALPH ARNOLD and ROBERT ANDERSON.

INTRODUCTION.

GENERAL.

The Coalinga oil district occupies a strip of land about 50 miles in 

length by 15 miles in width along the northeastern base of the Diablo 

Range, on the southwest side of the San Joaquin Valley, in western 

Fresno and Kings counties in central California. The region is 

accessible by rail from the main lines of both the Southern Pacific 

and the Atchison, Topeka and Santa Fe railroads by a branch line 

of the Southern Pacific running westerly from Goshen to Coalinga. 

The proved productive oil territory is comprised in a band 13 miles 

long by 3 miles wide in the foothills in the northern end of the district, within the Coalinga field proper, together with a narrow strip 

along the district's southwestern boundary in the Kreyenhagen field.

The rocks of this region are chiefly marine sedimentary strata of 

Cretaceous and Tertiary age. These have been subjected to much 

disturbance, but are in large part only slightly consolidated. There 

are two types of oil, a paraffin oil which appears to have originated 

in foraminiferal shales in the Upper Cretaceous, and an asphalt oil 

which is believed to have its original source in diatomaceous and 

foraminiferal shales of upper Eocene age. The former is accumulated 

in sandy zones interbedded with the shales that are supposed to have 

given rise to it; the latter, which is the chief product of the district, 

is accumulated to some extent in the Tejon formation, but chiefly in 

sands of the Vaqueros (lower Miocene), Santa Margarita(?) (upper 

middle Miocene), and Jacalitos -(upper Miocene) formations. The 

Vaquerosis the principal producer of the district. The oil wells vary 

in depth from 600 to over 4,000 feet and penetrate from 20 to over 

200 feet of productive sands. The product varies from a black oil 

of 14° or 15° Baume" to a greenish oil of 35° Baume or better. The 

yield ranges from 3 or 4 barrels per day for individual wells in the Oil 

City field to as much as 3,000 barrels per day for the deeper holes in

11
12 COALINGA OIL DISTRICT, CALIFORNIA.

the Eastside field. The total production for the district in 1907 was 

8,871,723 barrels, in 1908, 10,386,168 barrels, and it has probably 

reached over 15,200,000 barrels in 1909. It ranks first among the 

districts of the State in production.

The location of the Coalinga district and of the other oil districts 

of southern California is shown in figure 1.

turaf A NV» E 1 

.-bos'Angeles,

Area mapped and covered « e

inthisreport

Areas already mapped in 

reports

r principal oil-producing 

regions of the State .

Coalinga district 

McKittrick .. 

Midway 

Sunset » 

Santa Clara n. 

Santa Maria .. 

Bakersfield " 

Los Angeles 

Puente Hills " 

Summerland «

FIGURE 1. Index map showing position of the Coalinga district in central California. 

PLAN OF THE PRESENT ,WORK.

The purpose of this report is to treat of the general topography, 

geology, paleontology, and occurrence of petroleum in the Coalinga 

district, special importance being given in the discussion of the 

geology to those features bearing a direct relation to the problems 

of present and future development of the oil resources of the region.
INTRODUCTION. 13

The work is a continuation of the investigation of the California oil 

fields that is being carried on by the United States Geological Survey. 

During the last half of 1901 and the first half of 1902 George H. 

Eldridge began this investigation and made more or less detailed 

examinations of the various California oil districts, with the expectation of preparing a monograph on them. Upon his return from field 

work he wrote a brief resume of the results obtained, and this was 

published in "Contributions to economic geology for 1902. " a Later 

he began the preparation of detailed reports on each field, but unfortunately his death in June, 1905, cut short this work. In the fall 

of 1905 the senior author of the present report was assigned to the 

completion of the work begun by Mr. Eldridge, and by the middle 

of 1907 detailed reports on all of the oil districts in the counties 

bordering the coast had be.en made ready for the press. 6

The summer and fall of 1907 were spent by the writers in making 

a detailed geologic investigation of the Coalinga field proper and of 

the territory south of it as far as the line between Kings County 

and Kern County, near Dudley, and a reconnaissance of the surrounding regions. In order to make the economic results of this 

investigation available as soon as possible a preliminary report containing a portion of the matter here presented was published in the 

autumn of 1908.°

The present report includes a more complete discussion of the 

topography, geology, and paleontology, and gains in value by the 

addition of maps, sections, and other illustrations, and. in particular 

by the addition of the paper on the physical properties of the oils 

prepared by Irving C. Alien. The preliminary report may be considered as superseded by the present one.

In explanation of the plan of this and the other geologic reports 

bearing upon the California oil fields, it' must be stated that these 

publications are intended to be as thoroughly scientific discussions 

as possible within the limitations of time available for their preparation, and they assume upon the part of the reader a general knowledge of the fundamental facts and conceptions upon which any 

searching study qf the composition, mineral deposits, and history of

a Eldridge, George H., The petroleum fields of California: Contributions to economic geology for 

1902, Bull. U. S. Geol. Survey No. 213,1903, pp. 306-321. (That part relating particularly to the Coalinga 

district is on pp. 300-308.)

i> The editions of these reports that were issued for free distribution arc entirely exhausted. They are 

as follows:

Eldridge, G. H., and Arnold, Ralph, The Santa Clara Valley, Puente Hills and Los Angeles oil districts, 

southern California: Bull. U. S. Gcol. Survey No. 309, 1907, xi+266 pp., 17 figs., 41 pis.

Arnold, Ralph, and Anderson, Robert, Preliminary report on the Santa Maria oil district, Santa Bar 

bara County, California: Bull. U. S. Geol. Survey No. 317,1907, 69 pp., 1 fig., 2 pis.

Arnold, Ralph, Geology and oil resources of the Summerland district, Santa Barbara County, California: Bull. U. S. Geol. Survey No. 321, 1907, 93 pp., 3 figs., 17 pis.

Arnold, Ralph, and Anderson, Robert, Geology and oil resources of the Santa Maria'district, Santa 

Barbara County, California: Bull. U. S. Geol. Survey No. 322,1908,161 pp., 26 pis.

c Bull. U.S. Geol. Survey No. 357, 1908,142 pp., 1 fig., 2 pis.
14 COALINGA OIL DISTRICT, CALIFORNIA.

the earth must be based. The reports may be criticised as being 

too technical and as not easily comprehensible by the ordinary 

reader; but the form of discussion adopted is the only possible method 

of presentation because the treatment involves a certain amount of 

technical knowledge and the use of exact terms. For explanations 

of the principles of geology or the meaning of terms the reader is l 

referred to any one of the numerous text-books of geology." \

ACKNOWLEDGMENTS.

The writers wish to acknowledge their indebtedness to the late 

George H. Eldridge for the use. of the notes collected by him during 

his examination of the field. Acknowledgment is also due to other 

previous workers in the field, among whom are W. L. Watts, Frank 

M. Anderson, John H. Means, and H. R. Johnson. This paper benefits by the inclusion of chemical analyses of rocks furnished by ! 

W. F. Hillebrand and R. C. Wells, of the United States Geological 

Survey, and of a discussion of the petrographic character of the 

syenite from White Creek, by E. S. Larsen, jr., also of the Survey. 

S. G. Mason aided in the preparation of the fossil tables.

The economic value of a report like the present one, including as 

it does a discussion of the geology of developed territory, depends 

largely upon the amount and accuracy of the well data available for 

use in its preparation. Certain facts may be gleaned from a critical 

examination of the surface outcrops in any field, and many helpful 

conclusions may be deduced from a study of the facts thus obtained; 

also a comparison of the conditions met in a given territory with those 

in other better-known fields is often of great assistance; but for furnishing specific information regarding the occurrence of the oil in any 

particular area there is just one instrument, and that is the drill.

From the drilling of wells in the Coalinga field during the last ten 

years a large body of useful data concerning the underground conditions has been accumulated, and whatever of accuracy and value 

there is in the underground map and statements concerning the 

geology of the wells in this report is due almost entirely to the generosity of the operators in this field in supplying the. information. The 

writers therefore wish to acknowledge their indebtedness to the 

officers, managers, and other operators of the different oil companies 

for their hearty cooperation and support. Thanks are due more particularly to Messrs. James H. Pierce, W. W. Orcutt, S. A. Guiberson, 

jr., R. W. Dallas, W. R. ; Hamilton,/A. and H. Kreyenhagen, R. S. 

Peeler, A. M. Anderson, H. G. Anderson, J. M. Atwell, Charles Babtie, 

Gordon M. Baker, R. C. Baker, Orlando Barton, H. J. Bender, 

Scott Blair, S. R. Bowen, F. S. Brack, H. H. Brix,.C. A. Canfield,

<j Any of the following, besides various others, will be found useful: Dana, Text-book of geology; LeConte, 

Elements of geology; Chamberlin and Salisbury, Geology (3 parts); Geikie, Text-book of geology.
INTRODUCTION. 15

Frank Cleary, II. R. Crozier, F. P. Dagany, P. B. Daubenspeck, 

D. M. De Long, J. F. Ecbert, Andrew Ferguson, A. D. Ferguson, 

W. S. Fisher, A. D. Fram, Charles Fredeman, W. A. Gray, W. A. 

Greer, L. P. Guiberson, H. D. Guthrey, S. II. Ham, II. II. Hart, 

Thomas Hayes, R. S. Hazel tine, II. Henshaw, W. A. Hersey, Paul 

Iluntsch, W. A. Irwin, W. N. Kerr, W. P. Kerr, J. E. Kibele| Besley 

Lafever, J. L. Lennon, Walter Lewin, M. E. Lombardi, E. W. Mason, 

W. G. McCutcheon, R. P. McLaughlin, W. 0. Miles, J. II. Miller, 

S. E. Mills, R. B. Moran, T. A. O'Donnell, P. F. Page, Z. L. Phelps, 

J. II. Raney, Charles V. Reynolds, George D. Roberts, J. M. Robertson, C. N. Root, Guy II. Salisbury, George Schwinn, II. N. Seavers, 

Max Shafrrath, R. E. Shore, R. H. Smith, H. F. Stranahan, R. E. 

Thompson, T. H. Turner, P. S. Turnbull, J. Waley, J. L. D. Walp, 

Alex Wark, J. II. Webb, M. L. Woy, J. B. Wrenn, John M. Wright, 

and many Others who have contributed in one way or another to the 

 value of the report.

The writers also wish to express their gratitude-to Mr. R. B. Marshall, geographer in charge, and to Mr. E. P. Davis, topographer, for 

hearty cooperation during the course of the field season, when the 

topographic and geologic work were progressing simultaneously.

ADVANTAGE OF COOPERATION AMONG OPEKATOES.

The Coalinga oil field will continue to be the. greatest in California 

if every operator will conserve to the utmost the supply of oil stored 

within the boundaries of the district, and by wise management aid in 

keeping it available. An approximation of the amount of available 

oil in the territory covered by the underground-contour map (PI. XV) 

is 2,737,000,000 barrels. (See under the heading " Production," p. 247.) 

Some persons have the idea that underground resources of any kind 

are inexhaustible, but the notion is erroneous. When the oil in any 

field is once exhausted it will not be replaced within the limits of 

many centuries, if ever. It is not impossible that the processes of oil 

formation and migration are taking place constantly in some places, 

but such processes are so exceedingly slow when measured in years 

that they may be considered for practical purposes as nonexistent.

Fortunately the Coalinga field has had little of the serious trouble 

with water that is ruining certain parts of some of the other fields of 

California. This lack of trouble is probably due largely to the little-disturbed condition and the uniformity of the oil-bearing formations over 

most of the territory. But trouble from water is beginning to show 

its effects in certain parts of the field, and in more than one instance 

wells not yet abandoned are believed to be, either through accident 

or carelessness, letting water into sands that are productive in not 

far distant wells. In order to avoid the dangers incident to faulty 

drilling and handling of wells, the operators should meet and exchange
16 COALINGA OIL DISTRICT, CALIFORNIA.

information about the underground geology. It seems shortsighted 

for one operator to withhold his logs and other information about 

underground conditions from his neighbor, when this very withholding may be the cause of his neighbor's flooding a large area through 

lack of proper knowledge in shutting off the water. Furthermore, it 

is hoped that the legislature will recognize the needs of the petroleum 

interests in California, and, as has been done in other States, provide 

laws protecting the producers from negligent, shortsighted, or criminally careless methods.

PREVIOUS KNOWLEDGE OF THE GEOLOGY.

The mountains and plain along the western border of the interior 

valley of California have not received much attention from scientific 

investigators, owing to their isolation, the sparseness of the population, and the difficulties of travel. In recent years, however, the 

exploitation of its mineral resources has called attention to the region, 

and a small body of literature containing information of various 

kinds regarding it is gradually growing up. The early surveys of 

portions of California that were made in connection with the explorations for a railroad route to the Pacific Ocean by a number of 

engineers and scientists under the direction of the United States 

War Department, and in connection with the State Geological 

Survey under J. D. Whitney, did not include the region of the 

Coalinga district, so that until recent years little was known directly 

concerning its geology or physical features.

The State Geological Survey party carried its geologic reconnaissance no farther.south in the Diablo Range than the region of the New 

Idria quicksilver mine, which is about 25 miles northwest of Coalinga, 

but some general references to the topographic aspect of the more 

southerly mountains were made in the report published by Whitney 

and are quoted below in the discussion of place names. In 1888 the 

United States Geological Survey published a report by G. F. Becker a 

on the quicksilver deposits of the Pacific slope, which contains a 

chapter on the geology of the New Idria region. The features of 

that region are in many respects similar to those along the Diablo 

Range farther south.

The occurrence of coal, quicksilver, oil seepages, and gypsum in 

the region of the Coalinga district and the hope of finding other 

mineral deposits led a number of persons to prospect there in the early 

years, and the amount of investigation of this kind that has been 

conducted has increased more recently, with the result that an 

extremely productive oil region has been discovered and developed. 

But the first systematic geologic investigations that are known

oMon. U. S. Geol. Survey, vol. 13,1888.
INTRODUCTION. . 17

to have been carried on were those of W. L. Watts, who examined 

the oil fields along the border of the central valley of California for 

the California State Mining Bureau, and published a report on them 

in 1894.a The report contains valuable information concerning the 

geology of particular areas and gives a general outline of the succession of the geologic formations, the ages of which were determined 

roughly with the aid of paleontologic identifications by J. G. 

Cooper. The material of this report is reviewed in a later publication 

by the same writer. b

. In 1894 J. G. Cooper published a paper in which he describes the 

fresh-water fossils collected by Watts in the region of the Kettleman 

Hills, west of Tulare Lake. c

In the course of his investigations of the geology of the California 

oil fields George H. Eldridge, of the United States Geological Survey, 

spent much labor in studying out the intricacies of the geologic formations along the eastern flank of the Diablo Range, but unfortunately 

his death left the work uncompleted. A brief review of his knowledge 

of the petroleum fields of the State, in which he outlined some of 

the main facts in the geology of the Coalinga field and adjoining 

regions, appeared in 1903.d

Up to 1905 the notes published on the physical features of the 

Coalinga district had been scattering, but in that year Frank M. 

Anderson, who had been led by .his interest in the oil fields and in 

California geology in general to take up a study of this region, published a paper 6 in which a comprehensive review of the geology and 

paleontology of the Coalinga district and neighboring regions is 

'.ven. The paper has been of considerable service to the present 

writers and frequent reference to it will be noted in the text.

Shortly before the appearance of the authors' preliminary report 

(Bull. 357) Frank. M.. Anderson issued a paper/ supplementing the 

one just mentioned and. offering a revision of some of his first conclusions regarding the age of what he called the "Coalinga beds" and 

"Monterey shale." A brief summary of the principal paragraphs in 

his first paper is also given, this being made advisable by the destruction of the California Academy's stock of that paper during the fire 

of April, 1906.

a The gas and petroleum yielding formations of the central valley of California: California State Min. 

Bureau, Bull. 3; 1894.

6 Oil and gas yielding formations of California: California State Min. Bureau, Bull. 19,1900.

c On some Pliocene fresh-water fossils of California: Proc. California Acad. Sci., 2d ser., vol. 4, pt. 1,1894, 

p.166.

d Contributions to economic geology for 1902: Bull. U. S. Gcol. Survey No. 213,1903, pp. 306-321.

« A stratigraphic study in the Mount Diablo Range, California: Proc. California Acad. Sci., 3d ser., 

Geology, vol. 2, No. 2,1905, pp. 156-206, with plates.

/ A further stratigraphic study in the Mount Diablo Range of California: Proc. California Acad. Sci., 

4th ser., vol. 3, 1908, pp. 1-40.

88170 Bull. 398 10 2
r

18 COALINGA OIL DISTRICT, CALIFORNIA.

Owing to the rapid development of the oil resources of the Coalinga 

district and the demand for information regarding the region, a preliminary report, containing the major portion of the data of direct 

importance to the problems of oil occurrence that have been collected by the present writers, was published in November, 190S, as 

Bulletin 357 of the United States Geological Survey. A brief paper 

dealing with a portion of the district describes the occurrence of 

recently formed conglomerate on White Creek.®

Paleontology has played a prominent part in the working out of 

the various problems, both scientific and economic, connected with 

the Coalinga district, and in order to present this branch of geology 

more fully a bulletin entitled "Paleontology of the Coalinga district, 

Fresno and Kings counties, California," was prepared by the senior 

author and has just been issued as Bulletin 396 of the United States 

Geological Survey.

GEOGRAPHY AND TOPOGRAPHY.

DEFINITION OF PLACE NAMES.

a

For the sake of accuracy and convenience of reference a proper 

understanding must be reached regarding the names of the various 

places and features in the Coalinga district before a proper topographic 

and geologic description can be given. The region is one in which 

little detailed investigation has been made, and most of the natural 

features are unnamed, while to many others names are indefinitely 

applied. In the following pages are definitions of names that have 

been newly applied and names whose application has been made 

more definite. Almost all these names, including all the more important ones, have been submitted to the United States Geographic 

Board and have been approved and made permanent by that body. 

Most of these names appear on the map accompanying this report.

Coalinga district. The application of this name to the whole 

region included in the map accompanying this report is discussed on 

page 25. '

Coalinga field. The term "field" has been adopted as representing 

a subdivision of a "district," and the name "Coalinga field" is used 

in this report in its accepted sense as meaning the region of the developed oil field in the northern portion of the territory mapped, round 

about Pleasant Valley, in which Coalinga is situated. This region 

is in turn subdivided into the Eastside, the Westside, and the Oil 

City fields, terms which are in common usage and will be defined 

in the discussion of the developed territory.

Kreyenliagen field. Similarly the region of the hills west of Kettleman Plain is referred to as the Kreyenhagen field.

o Conglomerate formed by a mineral-laden stream in California,, by Ralph Arnold and Robert Anderson: 

Bull. Geol. Soc. America, vol. 19,1908, pp. 147-154.
GEOGRAPHY AND TOPOGEAPHY. 19

Kettleman Hills field. The possible future oil field east of the 

Kettleman Plain will be referred to as the Kettleman Hills field.

Diablo Range. The Diablo Range is the easternmost member 

of the California Coast Ranges south of San Francisco Bay. It 

extends southeastward from Carquinez Straits along the western 

border of the San Joaquin Valley. The name is taken from Mount 

Diablo, a prominent peak 15 miles southeast of Martinez on the Carquinez Straits, and.heretofore has been variously used for the small 

group of mountains centering around this peak, or for a part or all 

of the group of mountains extending southeastward from there and 

limiting the central valley of California on the west. The United 

States Geographic Board has fixed the southern limit of the range at 

Antelope Valley in the northwest part of Kern County just south 

of the region mapped as the Coalinga district, and has determined

that the correct name is " Diablo Range," instead of' 'Mount Diablo," 

"Monte Diablo," or "Sierra del Monte Diablo." The range is 

considered as terminating at this valley because it there sinks into 

low spurs, and the continuation of the mountain belt beyond the 

valley is a markedly individual range that is en e'chelon with the 

southernmost spur of the mountains to the north. This spur bringing 

the Diablo Range to an end is the one dividing Antelope and McLure 

valleys, later referred to as Avenal Ridge. San Benito River separates the Diablo and Gabilan ranges, farther north, but in the latitude 

of the Coalinga district the two ranges, owing to a complication of 

structures, coalesce into a high mountainous tract in which various 

component members run at angles oblique to the main trend of the 

Coast Ranges. In the portion south of the headwaters of San 

Benito River and Los Gatos Creek, the range may be considered as 

extending clear across to the drainage basin of Salinas River. In 

his chapter on the "Monte Diablo Range" ° J. D. Whitney devotes 

the opening paragraph to a definition of the range. He says:

In its northern extension the Monte Diablo Range is easily denned; but to the south 

it widens and inosculates with other ranges, or spurs, falling into it from the northwest, 

until finally, uniting with the extreme western members of the great group of the Coast 

. Eanges, it forms the broad region of high rolling hills, intersected by a labyrinth of 

narrow valleys, which lies between the parallels of 35° and 35° 30' and where distinctness of nomenclature for the different groups of elevations is almost entirely lost. For 

convenience, and as representing as nearly as possible a natural division of the Coast 

Ranges, the Monte Diablo Range may be considered as terminating to the south in the 

low ridges running out into the San Joaquin Plain at the head of Los Gatos Creek, in 

latitude 36° 20'.

Elsewhere,6 however, Whitney does not adhere to this limitation 

of the range, and describes as its most southerly division the mountains lying to the south between the "Estrella Pass," by which

oGeol. Survey California, Geology, vol. 1,1805, p. 8. 

t> Idem, pp. 9-10.
20 COALINGA OIL DISTRICT, CALIFORNIA.

he means the divide at the head of Los Gatos Creek, and the 

"Roble Pass," by which he means some divide across the range opposite the town of Paso Robles, most probably the pass now known as 

the Polonio Pass, which is at the head of Antelope Valley and which 

is here adopted as the southern termination of the Diablo Range. 

Whitney divided the range into several divisions, of which the 

above-mentioned division is the southernmost. He named it the 

"Estrella division," the group of mountains next to the north of it, 

between the head of Los Gatos Creek and the Panoche Pass, being 

named by him the "San Carlos division."

The explorations of the Geological Survey of California in the Diablo 

Range did not extend farther south than the region of the New Idria 

quicksilver mines, and therefore the knowledge obtained by them of 

the mountains to the south was not extensive. This is indicated by 

Whitney's impression, stated in the paragraph above quoted, that the 

southern continuation of the Diablo Range united with the westernmost members of the Coast Ranges between latitudes 35° and 35° 30'. 

As a matter of fact, the easternmost division of the Coast Ranges is 

isolated along most of this portion of its course, and may more properly 

be said to unite with the westemmost mountains south of latitude 35°. 

Other points in his description of the mountains are correct, however, 

and point to the appropriateness of including the "Estrella division" 

as a part of the Diablo Range. He characterizes the divide between 

the head of Los Gatos Creek and the San.Benito River as "not a low 

one," and states that the "Estrella division" to the south of this is of 

considerably less elevation than the "San Carlos division," and that 

it "sinks very low as we approach Paso Roble." The divide at the 

head of Los Gatos Creek is, in fact, high and does not form a pronounced break in the range, whereas the mountains do sink low in the

McLure, Antelope, and Cholame valleys, at the south end of the group 

named by Whitney the "Estrella division." It is therefore in harmony with Whitney's description of the Diablo Range, as well as 

with the features of the relief, to consider the range as terminating in 

the region of Antelope Valley.

Temblor Range. Southeast of Antelope Valley a range of distinct 

topographic and structural individuality forms the divide between 

the San Joaquin Valley on the northeast and the basin of San Juan 

Creek and the Carrizo Plain, on the southwest. It extends from 

Cholame Creek on the north to about latitude 35°, where it merges 

with the high mountain mass around Mount Pinos called the " Tejon 

Mountains." To this range the name "Temblor" is here applied.

The topographic and structural separation of this range from the 

Diablo Range is definitely marked on the north by Antelope Valley, 

but its northeastern termination must be more arbitrarily assigned. 

It may be considered as ending at Cholame, or as continuing to the
GEOGRAPHY AND TOPOGRAPHY. 21

northwest across the can};ron of Cholame Creek and following the western side of Cholame Valley to some point northwest of Parkfield. 

It seems more appropriate to consider it as so continuing and finally 

terminating gradually in the inclined plateau that slopes to Salinas 

River. The name Temblor is particularly suited to the range for two 

reasons: First, because the great California fault line, along which 

earthquakes have repeatedly originated, follows the range from one 

end to the other, being in the very heart of it throughout its northern 

part. A pronounced scarp and trough resulting from recent movements can be traced all along this line. Second, because the wellknown old Temblor ranch, west of McKittrick, is situated on its 

flanks.

Joaquin Ridge. A very prominent structural ridge runs southeast from the high mountains south of Idria to the San Joaquin 

Valley north of Coalinga, forming the divide between Los Gatos

Creek on the south and the tributaries of Salt Creek and Cantua 

Creek that run northeastward to the San Joaquin Valley. The 

ridge forks in its upper part, one branch heading in a mountain 

nearly 5,000 feet high situated in the northwest corner of the area 

mapped, and the other to the north, in the high region of San Benito 

Mountain. The summit of the ridge is serrated with picturesque 

rocks, one striking group of which is locally known as the "Joaquin 

Rocks." The name Joaquin Ridge is here applied to the ridge.

Anticline Ridge. The oil field north of Coalinga is on the nose of 

Joaquin Ridge, and immediately southeast of the main portion of the 

field is a depression in the ridge. Southeast of this point, which is in 

the southern part of sec. 34, T. 19 S., R. 15 E., a low, broad line of 

hills extends about 6 miles to the railroad line in the gap formed by 

Los Gatos Creek. (See PI. XV.) This ridge is formed by a perfect 

anticlinal nose, and is therefore referred to as "Anticline Ridge."

Juniper Ridge. A ridge approximately parallel with Juniper Ridge 

runs south of Los Gatos Creek from the divide between that stream 

and Lewis Creek as far as the canyon of Waltham Creek (Alcalde 

Canyon). It is a high, rugged ridge dividing the important Waltham 

Valley depression on the southwest from the Los Gatos Creek depression on the northeast and the low hills between Los Gatos and Waltham 

creeks (Alcalde Hills) on the east. This ridge is cut abruptly by Waltham Creek, south of which it is continued for about 2 miles in the 

isolated ridge known as " Curry Mountain." It is here called " Juniper 

Ridge" owing to its characteristic vegetation.

Castle Mountain. The name Castle Mountain has heretofore been 

indefinitely applied to a part or all of a high, sharp "ridge at the headwaters of Zapato, Canoas, and Big Tar creeks, which is visible from 

the valley on the east as the summit of the Diablo Range. The 

ridge is a very definite natural feature, presenting an abrupt escarp-
22 COALINGA OIL DISTRICT, CALIFORNIA.

ment to the northeast, and forms the western boundary of the southern corner of Fresno County. It extends from about the head of 

Zapato Creek to a point south of the head of Avenal Creek. The 

name may well be used for the whole ridge. This name has not been 

passed upon by the United States "Geographic Board.

Avenal Ridge. The name Avenal Ridge is here applied to the 

mountains separating Avenal Creek and McLure Valley from the 

Cholame and Antelope valleys. It is the southernmost of the spurs 

of the Diablo Range. The name, which means a "field of oats," 

is appropriate, because the hills forming the ridge are rounded and 

grass-grown, and afford a flourishing annual growth of volunteer 

oats. (See Pis. IX, A, and XI, A.)

Reef Ridge. A prominent ridge fa'ces the low hills that border 

Kettleman Plain, running southeast, between Castle Mountain and 

the foothills, from the south fork of Jacalitos Creek (Jasper Canyon) 

as far as Little Tar Canyon north of Dudley. A steep escarpment 

follows the northeast flank of this ridge, being formed by the prominent lower Miocene fossiliferous strata termed the "reef beds," 

which dip at a high angle and owing to their resistance rise high 

above the softer sand hills on the northeast. The name Reef 

Ridge, which is indicative of the most prominent one of its topographic features and of an important element of its geologic structure, is here applied to this ridge. (See PL VIII.)

Alcalde Hills. The foothills between Los Gatos and Waltham 

creeks, east of Juniper Ridge, northwest of Alcalde and west of 

Coalinga, are here called the Alcalde Hills.

Jacalitos Hills. The foothills between Waltham and Jacalitos 

creeks are here given the name Jacalitos Hills. Xacalli is an Aztec 

word adopted by the Mexicans, meaning "Indian hut" or "wigwam," and Jacalitos means a the little wigwams." The origin of 

tnis name is not known, but an observer can not fail to see in the 

symmetrical conical knolls a resemblance to tents or wigwams from 

which the name might have sprung. This descriptive suggestion 

makes the name particularly applicable to these hills. (See PI. II, B.)

KreyenJiagen Hills. The foothills southeast of Jacalitos Creek, 

between Reef Ridge and Kettleman Plain, may be named Kreyenhagen Hills. (See PL II, A.) The name is that of three families 

owning large tracts of land there. They are early settlers and 

almost the only inhabitants, and the region is generally known as 

the "Kreyenhagen country" or "Kreyenhagen's," or the "Kreyenhagen field." The last name is used in this report for the oil field 

of the vicinity.

Pyramid Hills. A long, narrow line of hills borders the eastern 

side of McLure Valley, extending from Little Tar Canyon, about 3 

miles north of Dudley, to the Dagany Gap, where the Avenal flows
GEOGRAPHY AND TOPOGRAPHY. 23

out of the valley, about 4 miles south of Dudle}7 . South of this gap 

they continue into the Devils Den region. They form a ridge 

capped with a succession of conical hills, which when viewed from'the 

east appear like isolated and similar pyramids. They are therefore 

 here called the Pyramid Hills.

Tent Hills. A somewhat similar line of hills of peculiar topographic and geologic structure extends along the Avenal at the. 

northeast foot of the high ridge (Avenal Ridge) west of McLure 

Valley. They begin about 4 miles west of Dudley and run 3$ miles 

northwest, being separated from Avenal Ridge by a marked depression. Owing to the resemblance of the individual hills to tents 

they are here called the Tent Hills. (See PL XI, A.)

Guijarrdl Hills. Immediately southeast of Anticline Ridge, on the 

opposite side of the railroad, is a small low group of gravelly hills 

referred to in the text under the designation Guijarral.. This is a

Spanish word meaning "a heap of pebbles" or u a place abounding 

in pebbles."

Dagany Gap. The name Dagany Gap is used for the gap at the 

lower end of McLure Valley, south of Dudley, through which Avenal 

Creek takes its outlet. It is named from an old settler of that region.

Avenal Gap. The Kettleman Hills are cut at latitude 35° 50' by 

a completely graded stream channel that is now followed by Avenal 

Creek. It will be referred to in the text as Avenal Gap.

Polvadero Gap. At their north end the Kettleman Hills are 

separated from the Guijarral Hills by a plain which is the drainage 

course of Zapato, Canoas, and Garza creeks. It is called Polvadero 

Gap because subject to dust storms. Certain of the early land maps 

have it "Pulvero/' but this is not correct.

Pleasant Valley. At least a portion of the valley at the mouth of 

Los Gatos Creek has been known as Pleasant Valley, the usage "not 

being definite. The name may well be applied to the whole basin in 

which Coalinga is situated.

Waltham Valley and Creek, and Alcalde Canyon. The creek at the 

mouth of which Alcalde is situated is variously known as "Wartham," "Warthan," "Waltham," and"Alcalde." The United States 

Geographic Board has decided that Waltham is the correct name. 

This stream heads in a broad structural valley having no relationship 

in geologic character with the lower portion of the stream course. 

(See PI. V, A.) The name Waltham Valley already in use for this 

upper valley should be definitely restricted to that part and not 

applied to the valley of the lower portion of the stream. It seems 

advisable to distinguish the canyon formed by Waltham Creek along 

its lower course under the name Alcalde Canyon, thus preserving a 

name which is already understood as referring only to the lower part.
24 COALINGA OIL DISTBICT, CALIFORNIA.

This name is therefore applied to the canyon extending from the 

edge' of Waltham Valley, where the stream cuts between Juniper 

Ridge and Curry Mountain, to Pleasant Valley.

McLure Volley. The valley in which Dudley is situated has long 

been known as McLure Valley,. after an early settler,- now dead. 

According to old inhabitants, that is the original and proper name. 

It is, however, widely known as "Sunflower Valley" by reason of the 

abundant growth of wild sunflowers. The United States Geographic 

Board has decided that the former is the correct usage. (See PI. 

XI, A) ^ -.

Kettleman Hills and Plain. The United States Geographic Board 

has decided that these names are properly written with an "e" and 

should not be spelled "Kittleman."

Various creeks and canyons. The Geographic Board has considered the various usages in regard to the names of the creeks in 

the Coalinga district, and the results of its decisions appear on the 

map.

For convenience of reference the present authors have applied 

names to the various marked canyons in the district. The canyon 

that runs north and south 7 to 10 miles due north of Coalinga, which 

is followed by the road to Oil City, is named Oil Canyon. (See PI. 

III.) The canyon in the Alcalde Hills which runs southeasterly 

across sees. 2, 11, 12, and 13, T. 21 S., R. 14 E., and which throughout 

its course across sees. 2, 11, and 12 is practically coincident with an 

anticline, is called Anticline Canyon. The application of the name 

Alcalde Canyon has been made above. The south fork of Jacalitos 

Creek may be appropriately named Jasper Creek, from the picturesque 

and brilliantly colored buttes of jasper that surround its upper portion. The name Jasper Canyon is therefore applied to the gorge 

that this stream forms across the northwest end of Reef Ridge. The

sharp canyon cut through Reef Ridge by Zapato Creek is called 

Zapato Canyon, and the similar one, formed through Reef Ridge by 

the south fork of Zapato Creek, 2 miles farther east, may be named 

Sulphur Spring Canyon from the abundance of sulphur water that 

issues in it. The similar canyon at the head of Canoas Creek is called 

Canoas Canyon. The names Big Tar Canyon and Little Tar Canyon 

are in common usage for the features to which these names are applied 

on the map.

Laval grade. The Laval grade is a name locally known for the 

road leading northeastward up a branch of Oil Canyon, starting in 

that canyon on the east side of the NW. £ sec. 29 and crossing the 

ridge at the head of this branch canyon in the center of the NW. £ 

sec. 21, T. 19 S., R. 15 E. This name will be frequently used for 

reference.
GEOGRAPHY AND TOPOGEAPHY. 25

Dudley-Lemoore road. The good road crossing the Kettleman 

Hills about 4 miles north of Avenal Gap will be referred to as the 

Dudley-Lemoore road.

LOCATION.

The region here mapped and referred to as the Coalinga district 

is situated in the southern part of Fresno County and the western 

part of Kings County, Cal., and is bounded on the south by the Kern 

County line. It forms a long strip of territory extending from 119° 

50' west longitude and 35° 47' north latitude at its southeast end to 

120° 37' west longitude and 36° 20' north latitude at its northwest 

end, along the foot of the Diablo Range. This is the easternmost 

member of the Coast Ranges, on the border of the Great Valley of 

California. The district as mapped is roughly 50 miles long and 15 

miles wide and extends over about 700 square miles. It covers the 

foothill belt along the valley and extends back into the high hills to 

the summits of the first surrounding mountain ridges, its northwest 

and southwest corners reaching the crest of the Diablo Range.

The developed oil territory commonly referred to as the Coalinga 

field is in the northern part of the district, in the foothill region 

around Pleasant Valley, where the town of Coalinga is situated. This 

is the only important settlement in the district or in the large surrounding region, the country being very sparsely inhabited. The 

names Oil City, Alcalde, and Dudley, which are marked on the map 

and often referred to in the text as if they represented places of importance, derive their chief importance from the scarcity of place names in 

the region and the necessity of having points of reference. Oil City 

is merely an area in which an oil camp is situated and in which 

development took place in an early part of the history of the field. 

Alcalde is the terminus of the Coalinga branch of the Southern Pacific 

Railroad near a farmhouse a few miles southwest of Coalinga, and 

Dudley is a stage station and post-office in McLure Valley. Oilfields 

is a post-office recently established in the field north of Coalinga.

The branch railroad mentioned joins Coalinga with the main lines 

of the Southern Pacific and Atchison, Topeka and Santa Fe railroads 

in the San Joaquin Valley, and wagon roads enter the district at 

several points from the valley on the east. Roads cross the Diablo 

Range from the west in the latitude of this district at four points (1) 

over the Benito Pass at the head of Los Gatos Creek, (2) over the 

divide between Priest Valley and the head of Waltham Creek, (3) 

across the range between Stone Canyon and Waltham Creek, and (4) 

over Cottonwood Pass. The first enters the Coalinga district along 

Los Gatos Creek, the second and third along Waltham Creek, and the 

fourth down Avenal Creek and McLure Valley.
26 COALINGA OIL DISTRICT, CALIFORNIA.

CLIMATE, DRAINAGE, AND VEGETATION.

The climate in the region of foothills and plain along the western 

borderof theSan Joaquin Valleyis arid. The rainfall is almost entirely 

limited to the "rainy season," chiefly from November to March, and 

is then slight. During the summer the days are hot and the atmosphere dry, the region becomes desiccated, and the streams dwindle 

and cease to flow on the surface before reaching .the valley. They 

continue, however, to have an underground flow and the plains thus 

receive underground much of the drainage of the Diablo Range. 

Water is obtainable in wells at most places in the district, but it is 

generally poor. Large quantities of it are pumped from beneath the 

plain at various points and it is likewise found abundant at various 

depths in the oil wells drilled in the hills. Owing to the large original 

content of salts of various kinds in the formations, and the aridity of. 

the climate, which allows this material to remain on and near the surface, the waters of the region are usually highly mineralized. Almost 

all water used for drinking, purposes is brought by train from farther 

out in the San Joaquin Valley.

The vegetation, as shown in the landscape views accompanying the 

text, is very sparse. The large plain and lower hills are naturally 

treeless and are overgrown with herbaceous ancl shrubby perennial 

vegetation, in most places scantily, as illustrated particularly by 

Plates II, A and B, III, and XVIII. The higher hills and the narrower valleys have in addition to such vegetation a scattering growth 

of small trees, principally oaks and junipers, as illustrated in Plates 

XVIII, IX, A, and XI, B. The mountain slopes are dotted with 

numerous, although rarely thickly set pine, juniper, and oak trees 

and present an attractive background to the valley border region.

Some of the trees attain a good size and are locally used on a small

scale for lumber. The growth on the higher slopes as shown in 

Plate XVIII is fairly typical of the mountainous region. The 

character of the underlying rocks exerts a marked influence on the 

vegetation, and belts occupied by different formations or lithologic 

zones may frequently be traced by the abundance or sparseness or 

character of the plants.

RELIEF. 

GENERAL TOPOGRAPHIC FEATURES.

The Coalinga district owes its broader topographic features to its 

position along the border between the Coast Ranges and the interior 

valley of .California. It is largely a region of foothills that rise on the 

west into the mountains and merge on the east with the wide level 

plain. The plain stretches thence with unbroken sweep to the foot 

of the high wall of the Sierra Nevada, the snowy summit of which is
U. S. GEOLOGICAL SURVEY 

A. ARID FOOTHILL BELT OF TERTIARY FORMA

Looking northeast from Zapato Creek across Kreyenhagen Hills toward the val

B, MONOCLINE OF TERTIARY STRATA IN JACALIT

Looking north from Jacalitos Creek, along the strike of the beds on the left, and across the str
GEOGRAPHY AND TOPOGRAPHY. 27

frequently part of the'landscape in the early morning or during the 

whole of clear days. The foothills form a continuous belt, in places 

narrow but more commonly miles in width, along the base of .the 

mountains, but are arranged in several groups along the base and 

around the ends of spurs descending southeastward from the Diablo 

Range, the groups being separated from each other by reentrant valleys that open out to the San Joaquin Valley.

Viewed from a distance across the dry, treeless plain the mountainous belt of the Diablo Range appears as a continuous, fairly eventopped ridge, covered with scattering vegetation and therefore blue 

in color, set back behind a broad belt of lighter-colored, grass-grown 

foothills that seem to form an inclined terrace sloping up gently 

toward the mountains. From nearer at hand broad valleys appear 

inclosed within outlying foothill spurs, the near-by hills assume great 

prominence and are seen to be sharply dissected, deep canyons appear

within the mountainous belt, and the horizon line is observed to be 

formed not by one continuous mountain ridge but by a series of discontinuous overlapping ridges running into the range toward the 

northwest at angles slightly oblique to the general direction followed 

by the edge of the valley and the range as a whole.

The area included in the accompanying map is not a well-rounded 

topographic province. None of the larger-stream courses are shown 

more than in part, and the area is bounded not by the main crest, of the 

mountains but by overlapping sections of the outlying high ridges 

that face the valley.

Some of the prominent features of the landscape have been outlined and briefly described in the preceding discussion of place names.

DIABLO RANGE.

General features. The Diablo Range in the latitude of the Coalinga district is a broad mountain group of moderate general profile 

but locally rugged character forming a continuous.barrier 2,500 to 

5,000 feet in height and 30 to 40 miles broad between the San Joaquin 

Valley on the northeast and the San Benito, Salinas, and Cholame 

valleys on the .west and southwest.

The summit altitudes of the crests of the range decline from the region 

north of Los Gatos Creek in the San Carlos division toward the south 

in the Estrella division '(these names being those applied by the Geological Survey of California under Whitney, as before mentioned), until 

finally declining along Avenal Ridge toward McLure and Antelope 

valleys, where the range comes to a stop and gives place on the southwest to the Temblor Range. Portions of the main watershed appear 

upon the accompanying map at only two points in the northwest 

corner, which is marked by a peak nearly 5,000 feet in height that 

stands at the head of Joaquin Ridge, and in the southwest corner,
28 COALINGA OIL DISTRICT, CALIFORNIA.

where the much lower Avenal Ridge, the southernmost spur of the 

range, appears. In the intermediate region the ridges that are represented on the western edge of the area are in general separated from 

the mam divide farther west by a region of lower relief determined 

by the presence of oblique structural valleys, of which Waltham Valley is the principal one.

Distinction from foothills. The mountainous region within the Coalinga district is marked off topographically from the foothill region 

both by its higher altitudes and steeper slopes, which in many cases 

begin abruptly along a line at the margin of the foothill belt, and by 

its somewhat different type of topographic development. The two 

regions are geologically distinct, for the reason that the mountain 

tract is one almost entirely of older and harder rocks, and the foothills mark the belt of softer Tertiary and Quaternary formations. 

In some portions of the region, however, a line of separation between 

the foothills and features more properly called "mountains" is not 

naturally traced.

Outcrops and slopes. The mountainous region affords abundant outcrops. It owes its topographic distinction from the foothill belt largely 

to the superior hardness of its constituent rocks, which stand out on 

ridge tops and canyon sides with bold relief. As examples may be cited 

the remarkable exposures of the sandstone strata on the flanks of 

Joaquin 'Ridge, along the face of Reef Ridge (see PI. VIII), and on the 

escarpment of Castle Mountain. The ridges are usually fairly eventopped, and have gentle summit slopes descending toward the larger 

drainage lines that follow the lines of structure and toward the valley; their flanks where cut by erosion have steep sides that drop 

abruptly into V-shaped transverse canyons. Steep slopes also border 

the broader structural valleys as effects of the structure for example, the 'southwest face of Jumper Ridge and Curry Mountain (PL V, 

A) and the northeast face of Castle Mountain, which are probably due to faulting, and the steep dip scarp of Reef Ridge (PI. VIII). 

As suggested above, the lines of drainage are principally of two kinds, 

those paralleling the structural lines and directly consequent upon the 

structure, which are the main lines, and those transverse to the structure, which are more strictly erosional in origin and are the principal 

lines of sharp dissection. These second lines of drainage have small 

tributary courses due to erosion that run either parallel with or oblique 

to the strike of the beds, and likewise cut deeply, exposing dip slopes 

and strike faces.

Constituent ridges. A peculiar feature of the Diablo Range, which 

has already been suggested, is the presence along its eastern flanks of 

numerous spurs running out toward the southeast and of reentrant 

valleys between these spurs. These ridges and valleys 'trend a little 

more nearly east and west than the range as a whole, which trends
GEOGRAPHY AND. TOPOGRAPHY. 29

about N. 35° to 40° W. They are primarily due to structural causes 

and not to erosion. The main salients of the Diablo Range that 

project toward the San Joaquin Valley in the Coalinga district are 

Joaquin Ridge and its structural continuation in Anticline Ridge and 

the Kettleman Hills, Juniper Ridge and Curry Mountain, Reef Ridge, 

the mountain northwest of McLure Valley, between the drainage of 

Big Tar Canyon and Avenal Creek, which forms the southern extension of Castle Mountain, and Avenal Ridge. These, as well as the 

yalleys or depressions separating them, are the topographic expression 

of folds and faults running obliquely to the main trend of the Diablo 

Range. These constituent ridges, which were mentioned under the 

subject of place names, will be described individually in the following 

paragraphs.

Joaquin Ridge. Joaquin Ridge is anticlinal and exposes on its 

lower flanks the oil-bearing formations, thus determining the position

of the oil field north of Coalinga. The ridge is structurally continued 

by the Kettleman Hills, which form a prominent isolated group rising 

over a thousand feet above the San Joaquin Valley. The spur 

formed by Joaquin Ridge and the Kettleman Hills is separated from 

the rest of the district by the synclinal and faulted depression of 

White and Los Gatos creeks and the synclinal Pleasant Valley and 

Kettleman Plain.

The ridge has a narrow but rounded crest that descends gradually 

from an altitude of nearly 5,000 feet in the northwest corner of the 

district toward the east and southeast, and then declines more steeply 

toward the head of Oil Canyon and the high foothills on which the 

Eastside oil field is situated. From a distance the summit appears 

smooth except for occasional notches and the sawtooth appearance 

presented by the outcrops of strata that dip down the ridge. One 

group of these outcrops forms the picturesque towers known as the 

Joaquin Rocks. On either side the ridge sends out long, smoothtopped, but steep-sided lateral ridges that decline by gentle stages 

toward the adjacent main lines of drainage and toward the valley. 

These ridges are separated by deeply trenched canyons transverse to 

the strike of the strata.

Toward its head Joaquin Ridge has a different topographic character, due to the different nature of the rocks. It assumes the gentle 

outlines everywhere characteristic of the areas occupied by the serpentine associated with the Franciscan'formation. The flank extending 

down to White Creek appears like an inclined plain notched by widely 

separated shallow troughs. This portion of the ridge is made visible 

from a long distance by the white deposits of serpentine lying on the 

surface, and from near at hand it is seen to be covered over great
30 COALINGA OIL DISTRICT, CALIFOKNIA.

areas by bare piles of white, .yellow, gray, and brownish-red comminuted serpentine.

The length of Joaquin Ridge is nearly 20 miles and the extent of 

its flanks from side to side, roughly speaking, 10 or 12 miles.

Jumper Ridge and Gurry Mountain. Juniper Ridge and Curry 

Mountain form the next spur to the southeast, beyond the Los Gatos 

Creek and Pleasant Valley depression, belonging together as a continuous structural feature due in part to faulting on the southwest side 

and in part to the hard strata that strike along it and form the summit 

(PI. V, A}. Within the district this feature has a length of about 14 

miles, and it extends much farther northwest. It gradually declines 

in altitude from elevations of about 4,000 feet at the northwest end to 

2,400 feet on the summit of Curry Mountain. The sharp gap of 

Alcalde Canyon, which begins at the point shown in Plate V, A, 

divides the spur into the two portions named. In the southeastern 

portion of its extent this spur presents a steep scarp on the southwest 

side, where it bounds Waltham Valley, and on the northeast a gradual 

monoclinal slope into the Alcalde Hills. The end of Curry Mountain 

drops abruptly into a depressed area of low, rolling hills (the Jacalitos 

Hills) that is the continuation southeastward of the Waltham Valley 

depression.

Reef Ridge. Beyond the low area last mentioned a prominent 

salient springs up along Jacalitos Creek and extends for about 23 

miles southeastward as a high divide between the foothills bordering 

the Kettleman Plain and a belt of low relief, not shown on the map, in 

which Jacalitos, Zapato, Canoas, and Big Tar creeks head. This 

divide is Reef Ridge, and all the streams named, as well as their forks, 

cut sharp gorges through it to a depth of 800 to 1,200 feet. The cliffs 

on its northeast face and some of the minor canyons crossing it are 

well shown in Plate VIII. The ridge has a general monoclinal structure, the component strata dipping steeply northeastward as a general 

rule. The ridge is due in part to the strike of the hard strata and 

in part to faulting along the southwest side. At its southeastern 

extremity it gives place to the minor ridge of the Pyramid Hills, which 

is en echelon with it.

The summit of Reef Ridge rises with smooth but fairly sharp crest 

from the northwest end toward the central portion, but there breaks 

into a belt of salient peaks and ridges, some of which rise considerably over 3,000 feet above sea level between the deep canyons that 

cut across the ridge and the branch canyons that follow along the 

strike of the softer zones. At the southeast end the ridge narrows 

into a single sharp crest with even summit and declines gradually to 

an elevation of less than 1,000 feet. The northeast flank of Reef 

Ridge is formed by the steeply tilted hard "reef beds" of the Vaqueros
GEOGRAPHY AND TOPOGRAPHY. 31

(lower Miocene) sandstone, as shown in Plate VIII. Its slope 

reflects the high angles of the strata and forms a wall against which 

the comparatively low foothill belt stands in marked contrast. 

The canyons that are deeply cut at short intervals down the northeast flank of the ridge or'Completely across it have carved the r^ef 

beds into a row of serrate peaks, and parallel zones of hard beds in 

the Eocene and Cretaceous formations below are similarly although 

less prominently affected. From near and far Reef Ridge is a picturesque feature of the landscape, and from each changing view point 

it assumes a different striking aspect.

Castle Mountain. The next salient of importance entering the 

area of the map is south of the head of Big Tar Canyon and the 

Castle Mountain fault zone. It is a high and prominent group of 

hills forming the southeastward continuation of the precipitous ridge 

of Castle Mountain. Castle Mountain itself is visible from almost 

all parts of the district as a high, sharp ridge with long, fairly even 

sky line and abrupt eastern face. It parallels Reef Ridge on the 

southwest and does not enter the area mapped. The hill group that 

continues the general line of relief toward the southwest juts out 

toward McLure Valley as a conically shaped mass reaching a height 

of over 2 ; 500 feet and sloping away at a medium angle on the north, 

east, south, and southwest. Around about its base there is a peculiar double row of hills and concentrically arranged depressions that 

give the group a unique appearance. These features are due to the 

geologic structure of the spur, which, broadly speaking, is domelike,, 

and to the curving strike around its base of the hard zones that have 

become weathered and eroded into relief.

Avenal Ridge. Reef Ridge and the last-mentioned spur are separated from the next salient to the south, Avenal Ridge, by the wide 

plain of McLure Valley and by the valley of Avenal Creek. Avenal 

Ridge is the main divide of the Diablo Range. Its extent within the 

district is less than 9 miles, but it continues beyond, northwestward. 

It is formed by an important closely folded anticline that plunges 

steeply southeastward and brings the range to an end. It is a high, 

bare ridge with gently curving contours and broadly spaced features. 

It has a fairly even sky line at altitudes between 2,000 and 2,700 feet, 

which is continuous except for three or four canyon notches. The 

northeast flank of the ridge descends with fairly steep slope to the 

foothills, at an elevation of about 1,000 feet, within 1 to a little over 

2 miles, but the slope is broken, and locally lessened and steepened, 

by benches that are due to the prominent relief of hard zones of strata 

forming longitudinal ridges and lines of hills. These benches are 

especially evident when seen in profile view, as in Plates IX, A, and 

XI, A.
32 COALIFGA OIL DISTRICT, CALIFORNIA.

THE FOOTHILLS.

GENERAL DESCRIPTION.

The foothills represent the eroded surface of the upturned Tertiary 

and early Quaternary formations along the edge of the valley. They 

form a belt, usually several miles wide, of rolling bare hills following 

the curving strike of the formations around the projecting ends of 

the mountain spurs and along the border of the intervening valleys. 

In the Guijarral and Kettleman hills they assume the character of 

isolated groups entirely disconnected from the mountainous tracts, 

around which those groups more properly called the foothills, form a 

fringe. A general similarity of elevation is characteristic of the foothill areas, and comparatively slight relative relief is the usual rule, 

the summits generally reaching higher and higher altitudes by degrees toward the mountainous belt. The majority of the summits 

range in altitude between 1,000 and 1,700 feet above sea, or usually 

between 400 and 1,100 feet above the neighboring valley surface, 

although a number of massive hills standing out above the general 

elevation or ridges rising toward the mountains reach as great a 

height as 2,100 feet. The hills gradually decline in general elevation 

toward the southern end of the district. The summits of the individual hills and ridges in the foothills belt appear to determine 

roughly a general plane that slopes upward gently toward the mountains and toward the major ridges, which coincide with the major 

axes of uplift, and to represent an old surface of erosional planation. 

This summit plane is in places sharply incised by narrow canyons 

that have left as much as half the original surface fairly intact or at 

least not greatly degraded. Instances of this are many in the 

northern part of the district. (See Pis. Ill, VII, A, and XIII, A.) 

Elsewhere remnants of the general summit are left only at isolated

points, as is more commonly the case in the southern part of the district. (See PI. II, A and B.) The soft formations of which the hills 

are largely composed lend themselves to minute, rapid, and fairly 

uniform sculpturing, which gives the hills the appearance of a wrinkled surface, especially when the obliquely falling rays of the sun 

have brought out. the intricate scattering of light and shade. The 

hills owe their form chiefly to three causes to the general reflection, 

on the surface, of the folds to which their uplift is due; to erosion 

along lines directed down the slope toward the valleys, at right angles 

to the structural lines, as a result of which a series of lateral ridges is 

formed; and to erosion along structural lines, particularly along 

bedding planes and lines of contact, as a result of which parallel longitudinal ridges and valleys and rows of hills are formed, and the 

lateral ridges are deformed or dissected into hills. Further detailed 

sculpturing is due to erosional wash along small channels tributary
U. S. GEOLOGICAL SURVEY 

OIL CITY FIELD AND RIDGE OF THE COALINGA AN
GEOGRAPHY AND TOPOGRAPHY. 33

and at right angles or oblique to the streams determined by these 

two main directions of erosion.

The gently sloping surfaces of the hills are ordinarily smooth, 

covered with soil or sand, and overgrown sparsely with herbaceous 

vegetation, sagebrush, and other low plants. The underlying formations form much of the surface, however, especially on the steeper 

slopes, and although the individual outcrops are not always in prominent relief the appearance of the strata on the surface and their 

effect on the topography is one of the most striking features of the 

hills. This effect is chiefly in evidence where differential erosion 

has brought out certain beds or rapid dissection has left lateral bluffs 

or steep strike faces of hills exposed. Typical effects of this sort are 

illustrated by Plates X and XVII. Where the soft formations are 

traversed by hard zones or beds the latter stand out as hills by 

virtue of the protection against erosion that they afford to the associated beds, as may be noted in the hills shown in Plates VII, A, and 

XVII. The structure and stratification are in places both broadly 

and in" detail reflected in the degree of relief, the slopes, and the 

vegetation of the hills. The gravelly and sandy beds, owing to their 

superior power of absorbing water and possibly also to other conditions, support vegetation where the clay beds do not, and the degree 

of coarseness of the beds is frequently to be made out by the varying 

abundance of vegetation, and by variable kinds as well. The result 

 is a marked parallelism and alternation of belts and lines of vegetation. Plates VII, A, and XIII, A, give a good illustration of the 

sharp lines of bedding that are brought out by the plant growth, x 

but in most other places the belts follow broader zones.

The foothills of the Coalinga district may be divided into several 

different groups according to their form, position, degree of distinctness from the mountains, and stage of degradation, although they 

all present similarities and each group merges in topographic character into the others. The hills toward the northern end of the district partake more of the character of the mountains than those to 

the south, whereas the latter are much more worn. The following 

descriptions of these groups will bring out some of their distinctive 

features.

HILLS NORTH AND SOUTH OP LOS GATOS CREEK.

The relief in the area of Cretaceous rocks northwest of Pleasant 

Valley partakes of the character of. both the mountainous and the 

foothill belts, and owes its distinctive features to this intermediate 

position. The region is one of long, high, narrow ridges running out 

at right angles to the structural lines, from the main ridges to the 

north and south which parallel these lines. The component strata 

dip down the ridges and tend to produce angular forms. They also 

88170 Bull. 398 10 3
34 COALINGA OIL DISTRICT, CALIFORNIA.

show their influence in giving rise to lateral extensions of the ridges 

and to high hills appearing along certain zones on successive ridges; 

and the manner in which the topography and the outcrops display 

the curving strike of the strata is remarkable. The ridges are separated by sharp V-shaped canyons at the bottoms of which the stream 

courses wind back and forth with short sharp turns. The summits 

exhibit a marked flattening and mutual equality in elevation, especially in the central portion of the Los Gatos Creek drainage basin. 

A region of rolling hills carved in the rilling of Tertiary deposits 

opens out toward the upper portion of White Creek, the relief here 

resembling somewhat that characteristic of the Waltham Valley.

HILLS AROUND THE END OF JOAQUIN RIDGE.

The hills north of Pleasant Valley are the continuation of those 

farther west and resemble them in that they are primarily formed 

by prominent ridges extending out from the higher tracts, across the 

strike of the beds. The ridges here, however, are more broken into 

individual hills, have broader and more rounded outlines, and-reflect 

the strong influence of the formations and structural lines in spurs 

that extend out on either side along resistant zones, in hills formed 

by prominent beds, and in contact valleys. The ridges are thus 

made irregular and in their higher portions may be said to be rugged, 

as, for instance, those in the Eastside field shown in Plate XVII. A 

peculiar feature of these ridges is the irregular crest line which results 

from the appearance at short intervals of eminences due to the outcrop of hard beds. The knolls so formed present steep slopes or 

bluffs up the ridge on the strike face and smooth dip slopes down the 

ridge. Such bluffs are especially numerous on the east flank of 

Joaquin Ridge. (See PI. X.) Long canyons that come down out of

the higher hills between sharp slopes and with steep gradient gradually open out and become almost lost between the low tongues that 

reach out toward the valley.

The longest of the ridges is Anticline Ridge, the extension of the 

anticlinal dome of Joaquin Ridge. It is a low, broad, even-topped line 

of elevation with shallow sweeping concavities due to erosion, and 

slopes gradually toward the gap formed by Los Gatos Creek. Southeast of that gap the same area of relief is continued in the Guijarral 

Hills. These present an abrupt slope where cut by the gap, but on 

the summit resume the gradual slope of the surface of Anticline Ridge, 

forming an inclined plain toward the southwest and south and finally 

merging with Pleasant Valley and the floor of Polvadero Gap.

ALCALDE HILLS.

South of the gap in the foothills formed by the debouchure of Los 

Gatos Creek upon Pleasant Valley the valley is bordered by hills that 

rise more sharply than those on other sides, the slope toward the valley
GEOGRAPHY AND TOPOGRAPHY. 35

being a dip slope but little less in angle than that of the beds. The 

same factors that are of importance in determining the form of the 

hills before mentioned, namely, the course of the drainage across the 

line of strike of the strata and the tendency of the strata to form lines 

of relief paralleling the structure, are here important, but the latter 

factor begins to assume the greater importance, and the Alcalde 

Hills are formed largely, especially in their southern part, by longitudinal ridges, gulches, and lines of hills. The southern portion of 

these hills appears like an inclined plane sloping down toward Alcalde 

Canyon on the south and up to Juniper Ridge on the west, and 

intricately and irregularly dissected by long, shallow canyons and 

steep gullies that trend in general down the slope of the plane, the 

drainage of the hills being chiefly toward Waltham Creek. Nowhere 

are the planed summits of the hills more clearly observable than in the

steeply inclined plateau-like surface that stretches northwest from

Alcalde Canyon up to the flat-topped ridges on the flank of Jumper 

Ridge.

JACALITOS AND KREYENHAGEN HILLS.

South of Waltham Creek the Jacalitos Hills continue the Alcalde 

Hills. A difference in character is noticeable, due to more advanced 

dissection, a more pronounced development of the features reflecting 

the structure of the strata, and a more distinct differentiation from 

the mountains. The change increases farther toward the south. 

The foothill belt from Waltham Creek south is not so apparently a 

continuous area of relief as in the north, but is composed of fragments 

of strike ridges separated by broad, smoothly concave longitudinal 

ravines. These features are illustrated in Plate II, B.

The Jacalitos Hills present an abrupt face toward Waltham Creek 

on the north side of a hill 1,900 feet high southeast of Alcalde, but from 

the summit of that hill and its spurs the hills decline gradually toward 

Jacalitos Creek on the southeast and the valley on the east. The 

drainage is predominantly toward Jacalitos Creek. On the west these 

hills extend widely and join the rolling area in the region of the 

Waltham Valley depression and the gentle, irregularly gullied slope 

of the serpentine area that extends behind Reef Ridge up toward the 

main crest of the Diablo Range. A prominent feature of the latter 

area is the group of picturesque buttes of jasper which are scattered 

over it and which are colored a brilliant vermilion by the growth of 

lichen.

The Kreyenhagen Hills (PL II, A) form a long foothill belt following 

the course of the soft formations between Reef Ridge and Kettleman 

Plain and are divided into several groups, each a few miles in extent, 

by streams crossing them at right angles. They abut upon the steep 

face of Reef Ridge, as shown in Plate VIII, and are distinctly sepa-
36 COALINGA OIL DISTBICT, CALIFORNIA.

rable from the mountainous belt which begins there., To the northeast the strata form ridge after ridge, paralleling each other, and 

extending the length of the separate divisions between the main 

stream valleys. These ridges, where regular, may be compared to a 

series of waves advancing, as on a smooth beach, toward Reef Ridge 

as the shore, and elsewhere to broken waves, as in a choppy sea. 

The ridges are slightly asymmetric, the northeast flank being a dip 

slope and fairly smooth, while the southwest flank is a steeper, strike 

face that is in many places eroded so as to leave sharp gullies and 

conical intermediate ridges extending outward. The groups of hillocks so produced bear some resemblance to an encampment of tents 

or wigwams, and, as elsewhere suggested, the name Jacalitos, meaning the little wigwams, may have been applied to the creek owing 

to this feature of the hills through which it flows. The greatest symmetry of the parallel ridges appears in the portion of the Kreyenhagen 

Hills between Jacalitos Creek and Big Tar Canyon, and there the 

long, straight, smooth troughs between the ridges doubtless gave rise 

to the name Canoas, meaning canoes, applied to the creek passing 

across the central portion of the hills.

Toward the south, the Kreyenhagen Hills become more and more 

worn, decline in elevation, and lose their relief. The prominent 

individual features are absent, and the foothill area is a rolling surface with low sweeping ridges and broad drains sloping gradually 

toward and merging imperceptibly with the Ke'ttleman Plain.

In the northern group of the Kreyenhagen Hills, as in the Jacalitos 

Hills, the locus of points of greatest elevation is asymmetric in position, the slope toward Jacalitos Creek on the northwest being steeper 

and shorter than that toward Zapato Creek on the southeast. The 

major part of the drainage flows in the latter direction. In the groups

of hills between the other streams farther south such a feature is not so 

clearly to be made out, but it is true that the course taken by the 

drainage is predominantly toward the southeast.

KETTLEMAN HILLS.

The Kettleman Hills form a small isolated range 30 miles long and 

5 to 6 miles broad, about 700 feet above the Kettleman Plain and 

1,100 feet above the San Joaquin Valley, extending from northwest to 

southeast and describing a broad curve toward the south in the 

southern half. The most striking features of the group are its 

isolated position in the midst of the surrounding plain, its long, narrow, regular extent, its almost horizontal summit line, which slopes 

gradually downward toward the two ends, its crescent shape, and 

its anticlinal origin. The topography is peculiar, and though in some 

ways similar to that of the hills in other parts of the district has 

various distinguishing features.
GEOGRAPHY AND TOPOGRAPHY. 37

As a result of the difference of elevation of the plains at the foot 

of the hills on the two sides the flanks are of different topographic 

character. The crest of the range is not in a central position, but 

considerably nearer the western side, and is formed by resistant zones 

of strata. The slope toward the Kettleman Plain is trenched by 

many sharp gulches, which with their tributary gullies give a minute 

sculpture to the soft hills. In consequence of the direct course of 

the drainage toward the valley the ridges are of the transverse type. 

The eastern flank is of greater extent, is, in general, more worn away, 

and lias more broadly developed topographic features. The drainage 

lines running to the valley are fewer in number, but of greater importance, and are more like the main streams crossing the Kreyenhagen 

Hills. The result, as in that case, is the development of tributary 

streams between strike ridges, these ridges assuming considerable

prominence where supported by resistant strata. The flanks of the

hills on the two sides and the gently declining elevations toward the 

two ends appear to determine smooth surfaces sloping away from 

the crest of the hills. These surfaces are broken, however, by almost 

level benches that are cut into them, especially at the foot of the 

main ridge on either side and over most of the eastern flank in the 

southern half of the hills. Toward the south end, as in the Kreyenhagen Hills, the range is much worn and" the relief becomes obscure.

HILLS AROUND M*LURE VALLEY.

The most prominent foothills around McLure Valley are those of 

the Pyramid Hills type, formed of the siliceous shale of the Santa 

Margarita (?) formation. This shale is very hard and resistant 

and stands out as a zone of relief along its outcrop as a result of 

differential erosion. McLure Valley is surrounded by a fringe of 

hills produced by this shale, the Pyramid Hills on the east, the Tent 

Hills on the west, and a prominent wall of knobs circling the base of 

the mountain spur on the north. As the names given to these hills 

imply, they are of 'conical shape. They form continuous ridges, 

along the summit of which symmetrical cones are left between the 

heads of the gullies. (See Pis. IX, A, andoXI, A.)

The hills at the head of McLure Valley between these lines of shale 

hills are very similar to those in the southeastern portion of the 

Kreyenhagen Hills. They are low and sweeping and merge with the 

valley floor. Prominent hills or buttes left by differential erosion 

occur here and there, and a belt of hills thus formed by a hard sandstone zone may be traced in front of the shale hill ridges. A terraced 

surface of the McLure Valley hills is well shown in Plate XI, A.
38 COALINGA OIL DISTRICT, CALIFORNIA.

THE BROAD VALLEYS.

The boundary between the hills and the valley bottom is not 

abrupt, because the plain has been alluvially built up along the 

border and the structural angle is obscured. There is, however, a 

usual change within a quarter to a half mile from an appreciable or 

steep slope in the hills to the angle of the plain, which appears almost 

level to the eye. The floors of the valleys of the foothill belt begin 

at an elevation between 800 and 600 feet and slope gradually toward 

the San Joaquin Valley. The floor of the large valley begins at the 

edge of the hills at an elevation of 500 or 600 to 300 feet, and slopes 

within a short distance to the general level surface of the plain, which 

lies between 400 and 200 feet above the sea. Within the district the 

surface of the San Joaquin Valley slopes almost imperceptibly 

southward to the basin of Tulare Lake.

The side valleys that branch out from the San Joaquin Valley 

between the inclosing ridges of foothills and mountains are Pleasant 

Valley and its continuation in the Kettleinan Plain, and McLure 

Valley. Just'outside of the district are the analogous basins of 

Waltham Valley on the west, which is almost entirely inclosed by hills, 

and Antelope Valley southwest of Avenal Ridge. All these valleys 

are structurally basin-like depressions whose streams have gained 

outlet to the plain through gaps either newly produced or deepened 

by erosion during the progress of formation of the basins.

TTILARE LAKE.

The only lake within the Coalinga district is Tulare Lake, which 

borders the southeastern portion of the district east of the Kettleman 

Hills. It is a broad, shallow body of water occupying a portion of

the almost level floor of the San Joaquin Valley and deriving its supply of water from several rivers that descend from the Sierra Nevada 

and spread numerous distributaries over the valley. Little or no 

surface water reaches the lake from the mountains on the west, 

although they are much nearer. The lake has no regular outlet, but 

in periods of high water Q the whole central portion of the valley to 

the north and south becomes flooded and marshy. Formerly the 

lake was one of the largest bodies of fresh water in California, but 

in late years it has been gradually declining in size, owing largely to 

the use of the water of its tributary streams for irrigation, to the construction of dikes, and to the reclamation of the land formerly covered by it. In 1880 it spread over an area about 27 miles long from 

northwest to southeast and 20 miles broad from northeast to southwest. Nine years later it was about 20 miles long from east to west 

and 15 miles broad from north to south. In still more recent years 

successive dikes had been constructed, the lake had almost dried up,
GEOGRAPHY AND TOPOGRAPHY. , 39

and most of the area formerly covered by it had been brought under 

cultivation. But the unusual precipitation of 1907 caused the whole 

central portion of the valley to be inundated, and extended the lake 

to approximately its old shore line of 1880, almost at the base of the 

Kettleman Hills. The accompanying topographic map (PI. I), 

which was made in the summer of 1907, shows the abnormally high 

mark reached by the lake at that time.

During the late Quaternary period Tulare Lake covered a much 

greater area than at present, as is shown by the presence of an old 

beach at an elevation of more than 100 feet above its present level, 

2 or 3 miles west of the northwestern corner of the lake as shown on 

the map, and also by marked shore lines at lower elevations. The 

old beach consists of a ridge of sand about 20 feet .wide and 6 to 8 

feet high, somewhat erpded and covered with low vegetation, which 

runs for a mile or so along the low slope flanking the Kettleman Hills. 

Its present elevation is probably due in part to the progress of recent 

relative uplift of the hill area. Benches marking other positions of 

the shore line are observable along the Dudley-Lemoore road between 

the lake and the Kettleman Hills, at an elevation of much less than 

100 feet above the lake.

Tulare Lake marks the lowest area in the Coalinga district and, 

in fact, in the whole southern end of the interior valley of California. 

Its surface lies a few feet less than 200 feet above the sea. North 

of the lake a broad zone of greater elevation crosses the San Joaquin 

Valley and forms a barrier diverting the drainage from the southern 

portion of the Sierra Nevada southwestward into the lake basin. 

To the south the valley floor on the side toward the Coast Ranges 

has a general elevation between 200 and 300 feet. A line of depression west of the middle of the valley connects Tulare Lake, by a low 

tract subject to marshy inundations, with Kern and Buena Vista 

lakes, which lie in the southern end of the valley at an elevation of 

a little less than 300 feet.

The origin of the basin occupied by Tulare Lake is probably due 

to the building up of alluvial fans across the San Joaquin Valley 

north of it by the rivers of the Sierra Nevada, especially Kings 

River, and by Los Gatos Creek and the other creeks of the northern 

part of the Coalinga district, which have formed an unusually large 

alluvial fan for the Coast Range streams.

DRAINAGE COURSES.

Character of streams. The main streams within the Coalinga 

district partake of the nature of all the streams flowing off the eastern 

flank of the Diablo Range. They are comparatively short mountain 

streams of medium gradient that flow from the mountains at short 

intervals in broad V-shaped valleys between the mountain spurs, 

and have many tributary streams a few miles in length with steeper
40 COALINGA OIL DISTRICT, CALIFORNIA.

gradient and sharper valleys.. Several terraces appear in many 

places along the sides of the stream courses within a few hundred 

feet above the present bottom, marking the position that the valley 

floor has occupied at different stages. (See PL IV, A.) The streams 

approach the plain through the lower hills with nearly graded or in 

places aggraded courses, emerge upon it over the gently sloping alluvial fans that they have built up, and form squarely cut, broad, 

shallow channels through the horizontal deposits of the valley floor 

or spread out and end as level washes. The dryness of the region 

does not allow them to reach any trunk stream, and the great valley 

is like a sea in bringing them to an end and forming a catchment 

basin. As before stated, none of the main streams in the Coalinga 

district heads within the area shown on the map. Owing to the 

slight rainfall and the prolonged drought in summer, none of these 

streams carries much water, and they all become nearly dry at the 

surface during that season.

The two most important streams of the district are Los Gatos 

Creek and Waltham Creek, which drain considerable tracts and flow 

'through deep, structurally important valleys, in their lower portion 

nearly graded. These streams join in Pleasant Valley and pass out 

to the San Joaquin plain through a narrow gap cut across the uplift 

of the Coalinga anticline.

The next most important streams are Jacalitos and Avenal creeks, 

and these with four others, Zapato, Canoas, Garza, and Big Tar 

creeks, complete the list of main streams. Of all of these much the 

same may be said. A common feature is that the main upper forks 

of these streams flow at an oblique angle to the range from northwest to southeast or from west to east, and that they change their 

course toward the northeast in the lower portion and flow directly 

away from the range across the structural lines.

Los Gatos Creek. Los Gatos Creek, the northernmost of the 

streams flowing off the Diablo Range in the Coalinga district, heads 

at Benito Pass, the divide between the San Joaquin Valley drainage 

and San Benito River, and flows southeastward with low gradient 

for about 30 miles to the plain. In the mountainous region it occupies a broad valley formed by well-worn ridges that slope gradually 

down into it from the flanks of the high ridges on the north and 

south. On reaching Pleasant Valley, like the other streams of this 

region, it forms a wide, shallow channel, with abrupt sides usually 

about 5 to 20 feet in height exposing the level deposits of the floor, 

and finally spreads itself out as a wash on the San Joaquin plain.

It is joined by an important tributary, White Creek, which heads 

on Joaquin Ridge, and after flowing off the flanks of this ridge follows 

the same general valley as Los Gatos Creek, the two streams being 

separated by a fairly sharp structural ridge 500 to 700 feet high 

above the valley bottom. The floor of the valley of Los Gatos
U. S. GEOLOGICAL SURVEY BULLETIN 393 PLATE IV

A. STREAM TERRACES ALONG ZAPATO CREEK. 

The upper terrace is an important one throughout the hills. Photograph by Robert Anderson.

II. HARD REDDISH-BROWN SANDSTONE CONCRETIONS WEATHERING OUT OF MASSIVE 

UPPER CRETACEOUS SANDSTONE.

On flank of Joaquin Ridge north of Los Gatos Creek. Photograph by Robert Anderson.
GEOGRAPHY AND TOPOGRAPHY. 41

. Creek, which is a few hundred feet wide at the widest, is crossed and 

recrossed by the meandering stream, and along its sides at the lower 

levels terraces representing former positions of the floor are evident. 

White Creek, owing to its mineral nature, has formed a hard cemented 

pavement of the stream gravel and has left terrace cappings of hard 

conglomerate along its sides. The low hills at the head of Pleasant 

Valley on either side of Los Gatos Creek are distinctly terraced at 

different levels and capped with coarse deposits of stream wash. 

Waltham Creek. Waltham Creek, a few miles south of Los Gatos 

Creek, enters Pleasant Valley near Coalinga. It rises in the heart of 

the Diablo Range as the main drainage feature of Waltham Valley, 

which is a broad structural depression with low interior relief between 

the two main spurs in this part of the range, namely, Juniper Ridge 

and the ridge farther west that forms the watershed between San 

Joaquin Valley and the area that drains directly to the ocean through

the Salinas Valley. The main forks in the upper portion of Waltham 

Creek run southeast. At the edge of the area shown on the map 

the -stream leaves the open Waltham Valley and enters Alcalde 

Canyon (at the point shown in PI. V, A) through a sharp gorge cut 

to a depth of 800 or 900 feet across the sandstone and shale strata 

forming Juniper Ridge and Curry Mountain. Thence for 3 or 4 

miles the canyon extends toward the west as a curving gorge with 

steep sides and graded floor, in places several hundred feet wide, and 

then turns abruptly northeast and opens out in the foothill belt into 

a straight, wider valley. The straight course of this lower portion 

of Alcalde Canyon is continued backward as a belt of low relief along 

the southeast end of Curry Mountain, but instead of coming from 

this apparent structural continuation of the lower part of its course 

the stream has cut the gorge already mentioned across the higher 

area to the north.

Jacalitos Creek. The next stream to the south is Jacalitos Creek, 

which is only a few miles from Waltham Creek and like it rises on 

the slopes surrounding the Waltham Valley line of depression, flows 

southeastward in that depression, cuts a canyon directly out into 

the foothill belt, and flows northeast to the plain in a broad, low, 

fairly graded valley. It joins Los Gatos and Waltham creeks in 

Pleasant Valley. A portion of its tributary, Salt Creek, is shown in 

the foreground in Plate II, B.

Avenal Creel:. The southernmost stream in the district is Avenal 

Creek; which flows southeastward in a canyon between Castle Mountain and Avenal Ridge and follows a well-graded course through the 

wide McLure Valley. Above the head of the valley it follows a 

ravine between Avenal Ridge on the southwest and a low ridge of 

knolls that forms a continuation northwestward of the Tent Hills, 

this ravine being along the contact between the Cretaceous beds and 

the middle Miocene (Santa Margarita?) white shale. (See PI. IX, A.)
42 coALiNGA OIL DISTRICT, CALIFORNIA.

The structural axis of the McLure Valley is farther east and marks 

the course of a minor stream. Avenal Creek breaks eastward across 

the row of hills mentioned, to enter McLure Valley, as may be seen 

in the middle distance in Plate IX, A. On the east side of McLure 

Valley it passes out through Dagany Gap, and thence its drainage 

course extends over Kettleman Plain and across the line of uplift 

of the Kettleman Hills through Avenal Gap, becoming lost on the 

floor of the great valley beyond. It is said that Avenal Creek has 

been known within comparatively recent years to drain around the 

southern end of the Kettleman Hills.

Other main streams. Zapato, Canoas, Garza, and Big Tar creeks 

are parallel and similar streams that cut V-shaped canyons through 

Reef Ridge and flow in fairly straight, low, open valleys across the 

foothills to Kettleman Plain. The canyons in Reef Ridge are sharp 

and deep and form marked features of the topography, as illustrated in Plate VIII. The drainage courses of the first three streams 

join and pass to the San Joaquin Valley through Polvadero Gap. 

Big Tar Creek drains southward down the Kettleman Plain and out 

through Avenal Gap. Stream terraces, as shown in Plate IV, A, 

have been formed along the courses of some of these streams.

Minor drainage courses. In addition to a number of main" forks 

toward the head of the streams already mentioned, which have 

courses similar to the main streams, there are a great number of 

minor drainage lines of different character that "either pursue independent courses to the edge of the plain or form tributaries at right 

or nearly right angles to the main streams. In places these in turn 

are entered at sharp angles by tributary gulches of considerable 

size, but ramifications of a higher order have rarely developed above 

the stage of swales or steep gullies. In the mountains and higher

hills the minor drainage courses are for the most part sharp V-shaped 

canyons and arroyos. In the more gently sloping hills they are open 

ravines with rounded contours. Oh entering the plain these streams 

cut sharp channels in the soft filling of the valley, as shown in Plate 

XII, A.

PHYSIOGRAPHIC DEVELOPMENT. 

FACTORS INFLUENCING DEVELOPMENT.

The most apparent feature of the topography on the eastern flank 

of the Diablo Range is its reflection of the structure of the formations, 

the controlling factor in the development of the physical features having been the folding and faulting of the strata. The broader features 

of the relief as well as a large proportion of the minor ones have been 

formed in accordance with the structure. A further factor, the 

differences in the rocks, especially in degree of induration, has played 

an important part in regulating the rate at which development has 

taken place and in modifying the forms due to structural features.
GEOGRAPHY AfrD TOPOGRAPHY. 43

The climate likewise has acted as a modifying factor in the weathering of the strata and as a cause of local variation in the processes of 

'erosion.

The chief processes by means of which physiographic change has 

been brought about have been orogenic movements, aqueous erosion, and aggradation. A further process of importance, sufficient to 

warrant mention, is gravitational degradation, especially by means 

of landslides, which are numerous in the somewhat incoherent strata 

of this region. Forces producing changes of elevation, both broadly 

and locally, have been continually active up to late geologic time 

and have left no areas unaffected, and the progress of every physiographic change begun within the late Tertiary and the Quaternary 

periods has been complicated by modifying movements.

HISTORY OF PHYSIOGRAPHIC DEVELOPMENT.

Some of the broad physiographic changes of early periods in this 

region will be outlined in the discussion of the geologic history. In 

the present connection the evolution of the topographic features 

during the period subsequent to the first great movements of the 

Quaternary will be taken up. These movements took place at the 

close of the period represented by the Tulare formation, which comprises the youngest strata of the region that are markedly displaced 

from their original horizontal attitude. The movements were proably contemporaneous with those occurring in the early Quaternary 

along the California coast and were long continued. They brought 

about the uplift and tilting of all the post-Eocene formations, which 

up to that time had probably not been severely disturbed, and caused 

the older strata to be upheaved in the axis of the mountainous 

belt, which had been previously determined and over which processes of degradation had been at work in earlier periods. The 

mountains were thus given pronounced relief and their topographic 

youth was renewed. The later Tertiary and early Quaternary 

deposits, as yet in large part incoherent strata, were raised on the 

flanks of the mountains and probably locally on the crest. With 

this uplift came acceleration of the erosional processes. The old 

streams began to flow with greater vigor, to cut their valleys deeper 

into the mountains, and to extend them farther and farther outward 

upon the strata that were being lifted up out of the plain. The 

uplift was so gradual that these streams, and the others which began 

forming down the slope of the blocks that were being tilted, planed 

off large portions of the lower areas almost as fast as they were lifted, 

and were able to keep their course across lines of relief that were 

raised beneath them. The rnainpreexistent streams probably followed 

the old structural lines that form the main valleys at present, such 

as those of Los Gatos and White creeks, Waltham Creek, and Avenal 

Creek.
44 COALINGA OIL DISTRICT, CALIFORNIA.

The streams that were formed subsequent to the first of these 

movements, tributary to the main streams that followed the structural lines, were consequent upon the structure, in that they took 

their course down the dip slopes determined by the new movements. 

They thus became fixed in courses at right angles to the main valleys, 

and in turn they themselves acquired tributaries at right angles 

that were determined by the strike of soft zones of strata. In this 

way the present topographic forms both in the mountains and foothills were eventually developed in accordance with the folds and 

the stratification.

It can not be stated whether the process of uplift was continuous 

or whether one or more periods of quiet intervened, allowing part of 

the planation to take place during periods when no movement was 

affecting the region. As the movements continued the partly 

planed surfaces were warped along the axes of disturbance and new 

cycles of erosion commenced to affect them. The appearance of the 

surfaces so tilted in the foothill region has been mentioned. They 

reflect the major anticlinal and synclinal folds and their plunges. 

It can not be said, however, that all such remnants of surfaces of 

planation are relics of the erosion that took place in the Pleistocene. 

There are many that are older, especially in the ' mountainous belt. 

The slopes that have been mentioned on the eastern flank of Juniper 

Ridge and extending down into the Alcalde Hills give a good illustration of the preservation of the pre-Miocene surface of the Cretaceous 

rocks, and of the early Miocene surface of the beds locally preserved 

as a little-disturbed capping over them.

During the latter part of the Quaternary, and perhaps during most 

of it, the main synclinal troughs in their more depressed portions 

have acted as basins for receiving much of the large amount of material worn from the higher regions. They have thus become aggraded into wide, almost level plains, such as Pleasant Valley, Kettleman Plain, McLure Valley, and the great San Joaquin Valley. The 

smaller valley bottoms have also been aggraded to some extent, as 

in the case of the lower portions of Alcalde Canyon, the valley of 

Los Gatos Creek, and some others of the larger streams, but the 

filling is not so deep as in the main valleys, and the majority of the 

small stream courses are not filled. The latter fact, taken with the 

occurrence of stream terraces at various levels (such as shown in 

Pis. IV, A; IX, A; and XI, A) and of bluffs due to undercutting along 

stream banks, indicates that most of the streams are actively engaged in eroding their valley bottoms, the cause probably being the 

continuance of upward movement along the already existent belt 

of topographic relief.

The general stage of development of the topography is youthful, 

although some areas, especially in the foothill belt, have reached
GEOGRAPHY AND TOPOGRAPHY. 45

an advanced stage of youth approaching maturity. The course of 

physiographic development in the mountains and in the foothills 

has been similar, and the resulting type of topographic features due 

to the reflection of the structure is much the same. But modifications of the type have been caused by other factors, especially the 

difference in hardness and compactness of the strata in the two 

regions. In the mountains the Cretaceous strata which cover most 

of the region are well indurated and fairly homogeneous. The 

development has therefore been retarded, has been more even, and 

is now in a youthful stage. In the foothills the formations are largely 

soft, but are of various degrees of induration. Erosion has been 

rapid and has been able to gain a strong foothold along certain 

zones. In consequence, the features of certain parts of the hills, 

especially in the southern portion of the Kettleman and Kreyenhaffen hills and along the soft zones elsewhere, are well worn and

'

have an old appearance. The reason for the greater amount 01 

wear to which the foothills in the southern portion of the Coalinga 

district have been subjected may be that the streams flowing off 

the Diablo Range were during much of the Quaternary period concentrated on that portion of the region by following a course southward along the synclinal depression of the present iCettleman Plain, 

being later directed into their modern channels by a warping across 

the northern portion of the Kettleman Plain determining the drainage divide in the plain and the rise of the anticline in the northcentral part of the Kettleman Hills. It may be supposed that the 

streams wore down the southern portion of these hills as they 

were being uplifted, and cut the present Avenal Gap. The other 

similar gaps in the Coalinga anticline uplift, however, must be explained, and it is difficult to see how the streams on the north could 

have formed these gaps otherwise than by following their original 

courses continuously throughout the period of uplift. A possible 

hypothesis in explanation of the progressively greater amount of 

degradation that has taken place southward within the district is 

that a general tilting took place after the main original movements, 

causing the whole region to slope southward as it does at present. 

The mountains decline in height from the San Carlos division toward 

Antelope Valley, as has been brought out elsewhere; the foothills 

and the plains do the same, and the drainage, even where not determined by the main structural axes that plunge toward the southeast, has a predominant southeasterly course. The movement producing such a regional tilting, either through progressively. greater 

depression toward the south or through uplift toward the north, 

might have been of similar nature to that occurring in former 

periods which caused the thickening and greater completeness of 

all the post-Eocene formations toward the south as compared with 

their continuation toward the north. , . . . ..
46 COALINGA OIL DISTRICT, CALIFORNIA.

GEOLOGY. 

GENERAL STATEMENT.

The eastern slope of the mountains bordering the San Joaquin 

Valley is formed by strata of great thickness dipping toward the valley. 

The oldest rocks exposed appear in the axis of the mountain range at 

the base of the monocline, and thence eastward successively younger 

formations appear as the edge of the valley is approached. The 

different formations that may be recognized as units in this series, 

with the time divisions to which they correspond, are as follows, 

from the oldest to the youngest: Franciscan (Jurassic?), Knoxville 

(Lower Cretaceous), Chico (Upper Cretaceous), Tejon (Eocene), 

Vaqueros (lower Miocene), Santa Margarita (?) (upper middle Miocene), 

Jacalitos (early upper Miocene), Etchegoin (uppermost Miocene), 

Tulare (Pliocene and early Pleistocene), and Quaternary alluvium and 

terrace deposits. These formations, with the exception of certain 

igneous and metamorphic rocks associated with the Franciscan, are 

of sedimentary origin. With the exception of the greater portion 

of the Pliocene and Quaternary and of minor amounts of the earlier 

Tertiary deposits, these sediments are marine. They indicate that 

the greater portion of the area included within the Coalinga district was beneath the sea during periods occupying probably the 

major portion of the time from the Jurassic to the end of the Miocene. 

Yet the unconformities separating all of these formations from one 

another show that intervals occurred during which no sediments were 

deposited, and that even with the enormous thickness of strata that 

is preserved the record is by no means complete. In general it is more 

complete in the southern than in the northern portion of the district, 

and most of the maximum thicknesses given are based upon the 

Occurrences there. The record generalized in the columnar section 

may be more complete than the number of unconformities would 

seem to indicate, since probably not all are present in all parts of the 

district.

The accompanying columnar section (fig. 2) gives a generalized 

resume of the lithologic character, relations, and maximum thickness 

of these formations as they appear in various parts of the Coalinga 

district. It can not, however, convey a conception of the variation 

of the formations in different parts of the district, which the descriptions of them that follow show to be a characteristic feature. Much 

detailed field work and paleontologic study have still to be accomplished before a final adjustment of the complex problems of correlation of the formations within the Coalinga district may be reached. 

The table on page 48 summarizes what is known of the age of the formations of the district and their time relation to the formations in 

other portions of the Coast Ranges.
GEOLOGY. 47

Alluvium and terrace do- _________ posits (Pleistocene and -,. _- 0 -_^-o -~^T-- 

Recent), 1-100+ feet. xh'»~.j'r-\I ~-^??

Tuiare formation (Pliocene-lower Pleistocene). 

3,000+ feet.

Etchcgoin formation (uppermost Miocene),3,500+ 

feet.

Jacnlitos formation(carly 

upper Miocene), 3,800=t

feet.

Santa Margarita (?) formation (upper middle 

Miocene). 900-1,000+ 

feet.

Vnqueros sandstone 

(lower Miocene), 900 

feet.

Tejon f ormatlon(Eocene), 

1,850+ feet.

Knoxvllle Chico rocks 

(Cretaceous), 12,800+ 

feet.

Franciscan formation 

(Jurassic).

Sand, clay, gravel, stream conglomerate, and soil.

Unconsolid'ated but locally hardened, unfossiliferous light-gray 

and yellowish sand, light and dark clay, coarse and flne'gravel, 

and thin layers of gray and purplish sandstone: In part of 

fresh-water and marine origin hut probably largely fiuviatile. 

At the base fresh-water sand, sandstone, gravel, shell deposits, 

and limestone.

Slightly consolidated, chiefly marine fossiliferous beds of gray 

and blue sand, black clay, light sandy clay, pebbly sand, and 

'gravel, with locally burdened bedsof sandstone and occasional 

layers of siliceous and calcareous shnle. The upper third is 

largely dark clay, the lower portion blue sand.

Slightly consolidated marine fosslllferons beds of light-gray, 

greenish-gray, blue, and brown sand, clay, and flue gravel, Interbedded'with similar deposits Indurated Into sandstone, 

shale, and conglomerate, with some siliceous shale.

A

B 

North of Waltham Creek: Marine fossiliferons sand, clay, gravel, 

and comminuted serpentine, in part Indurated. South of Waltham Creek: White, purple, andbrownsillceous.calcareous,and

B argillaceous shales. '

Marine fossiliferous gray sandstone and sand with mi nor amounts 

Q of conglomerate and gravel and diatomaceous and clay shale.

Marine white and brown diatomaceous and forumliiifcral shale.

Marine yellowish, brown, and gray fossil if erous and locally Wgill tic sandstone and dark clay, with a local basal conglomerate.

Upper division. In upper half: Purplish siliceous shale, dark 

clay shale, light-colored calcareous shale, white and yellow 

sandstone, and a minor zone of tawny concretionary sandstone. 

In lower half: Chieiiy massive drab concretionary sandstone. 

Marine fossils of Chico (Upper Cretaceous) sparingly throughout.

Alternating thin, sharply defined beds of dark clny shale, sandy 

shale, iron-gray and brownish-gray sandstone, and some beefs 

of conglomerate and pebbly sandstone; marine fossils of Chico 

(Upper Cretaceous) ago sparingly In upper portidn.

Coarse, massive conglomerate zone of locally variable thickness, 

with large bowlders of pro-Franciscan rocks. Probably basal 

conglomerate of the-Chico.

Thinly bedded dark shale and sandstone, similar to that above, 

but'withont fossils.

Massive Iron-gray sandstone..

Thinly bedded dark shale similar to that above, with some sandstone layers.

Similar shale and sandstone to that of lower portion of Knoxvllle, 

Chico, jasper, and glaucophane and other schists, with intimately associated serpentine.

2000 4000 GOOOTeet

FIGURE 2. Generalized columnar geologic section of the sedimentary rocks of the Coalinga district. Oil 

zones shown In solid black. Letters A, B, C, D at right of section indicate oU afiaes,, so d.e.sjgnated 

in text.
Tentative correlation of formations of the Coalinga district with the standard California C

 California.

Era.

' >. .- . ,;. Cenozolc.

Mesozoic.

System.

Quaternary.

 Tertiary.

Creta- ceous.

a£? D"O

i^'ta 

(?)

Series.

Recent.

Pleistocene.

Pliocene.

 Mio- 

- cene.

Oligocene.

Eocene.

Standard Coast Range 

section.; i.

Alluvium.

San Pedro.

TTl^ 1 " ""

Merced.

San Diego.

San Pablo.

Santa Margarita.

Monterey.

Vaqueros.

San Lorenzo.

Tejon.

Martinez.

Chico.

Horsetown.

Krioxville.

Franciscan.

Granitic rocks, schist, 

etc.

Schist; limestone.

Coalinga district section.

Stream conglomerate and 

alluvium.

Stream deposits, valley 

fillings, and raised 

beach.

Tulare.

Etchegoin.

Jacalitos.

Santa Margarita ( ?).

Lacking (with possible 

exception of a small 

part).

Vaqueros.

W anting (?). 

Tejon.

Chico. 

Knoxville.

Franciscan.

Santa Maria district 

section.

Alluvium.

Terrace deposits and 

dune.sand.

Fernando.

Monterey.

Vaqueros.

Sespe and Tejon, undifferentiated.

( ?) 

Knoxville.

Franciscan.

Santa Cla

tura Cou

Alluvium

Terrace d

and gra

Fernando

6 | Shale. 

® I Upper s

10 Shale. 

^ [Lower s

Vaqueros

<u [ Upper b

co < Red bed

02 I Lower b

Topatopa

Granitic 

etc.
GEOLOGY. 49 

ROCKS IMPORTANT WITH RELATION TO PETROLEUM.

The strata older than the upper part of the Cretaceous are of little 

importance in this district in connection with the occurrence of petroleum. The uppermost Chico (Upper Cretaceous), Tejon (Eocene), and 

Vaqueros (lower Miocene) are the principal sources or reservoirs of 

the oil, and therefore of prime importance. The.Santa Margarita (?) 

(upper middle Miocene) and Jacalitos (early upper Miocene) are 

petroliferous only at their base, and their higher beds together with 

those of the Etchegoin (uppermost Miocene) are the strata which 

overlie the oil sands and through which the wells are drilled, so that 

their relation, thickness, character, and structure have an important 

bearing upon the problem of accessibility of the oil and are worthy of 

detailed study. The Tulare (Pliocene-lower Pleistocene) is of less 

direct importance in this connection, but aids in throwing light upon 

the structure and the relation of the different formations.

 ECONOMIC DEPOSITS OTHER THAN PETROLEUM.

The present report does not aim to discuss fully any of the economic 

deposits except petroleum.

The vicinity of Coalinga was known for its coal deposits before its 

rich oil resources were discovered, and an attempt was made many 

years ago to mine the coal. Two mines were started on the west side 

of Pleasant Valley by the San Joaquin Valley Mining Company, but 

the enterprise proved unprofitable. The coal is lignitic and occurs 

in thin local beds varying in thickness up to a foot or two. The lignite is usually crumbly and grades into seams of carbonized wood. 

It is interbedded with extremely varied gypsiferous sand and clay in 

the Tejon formation (Eocene), which is characterized by coal deposits 

at various other points in California.

There is a large quantity of gypsum in the Coalinga district. All 

the Tertiary formations are extremely gypsiferous and local seams of 

gypsum are. present in the Cretaceous rocks as well. It usually 

occurs in the form of thin platy crystals filling joint cracks or occupying spaces along the bedding planes, or as crystal masses occupying 

irregular cavities. It is frequently so abundant that it permeates 

throughout certain beds, and either forms a hard cement for the 

original material or makes up almost the whole of the bed. Such 

deposits are of practically no economic value, owing to the impossibility of getting the material in a pure state. Gypsum likewise occurs 

locally in efflorescent surface deposits of soft white gypsite, as on the 

surface of the Tejon (Eocene) formation on a point of the hills at the 

edge of Pleasant Valley about 5 miles northwest of Coalinga and on 

the surface of the Vaqueros sandstone (lower Miocene) just east, of 

Oil Canyon, 8 miles due north of Coalinga. An analysis of material 

' 88170 Bull. 398 10 4
50 COALINGA OIL DISTRICT, CALIFORNIA.

from the former locality, made by R. C. Wells, of the United States 

Geological Survey, showed it to contain 71.6 per cent of calcium sulphate (equivalent to 42.2 per cent SO3) and 0.8 per cent of silica. 

These deposits have been mined on a very small scale, but they are 

not extensive. The gypsum of the Coallnga district and the surrounding regions is discussed in a paper by F. L. Hess on the 

gypsum deposits of California, issued as Bulletin 413 of the United 

States Geological Survey.

SEDIMENTARY FORMATIONS.

FRANCISCAN FORMATION (JURASSIC?).

GENERAL DESCRIPTION.

The central portion of the Diablo Range is occupied by an old and 

for the most part much altered formation that is in every way similar to the well-known Franciscan formation of other parts of the 

State. It comprises the oldest rocks here exposed, as it antedates the 

Knoxville (Lower Cretaceous), but further than this little can be said 

regarding its age. There is.no definite fossil evidence of the age of 

the Franciscan elsewhere, and in this region none has been found, .but 

from evidence obtained in various places in the Coast Ranges the 

formation is believed to be certainly pre-Cretaceous.

The areas covered by the Franciscan formation are easily recognizable, as they are characterized by typical rocks and topography. 

The most characteristic feature of these areas is the invariable presence of serpentine, which is associated with the formation and is usually classed and described with it owing to its intimate relationship, 

although it is in reality intrusive in the sedimentary rocks, and therefore later in age. The original sedimentary rocks, which are sandstone, shale, and jasper, occur in detached areas and are greatly disturbed. They are intermingled in a complex way with glaucophane, 

actinolite, and other schists, serpentine, and other metamorphic rocks, 

and one area of soda-bearing hornblende syenite is shown on the map. 

In the portion of the Coast Range within and bordering the Coalinga 

district the metamorphic rocks of the Franciscan formation greatly 

predominate over,the unaltered. In the small area of Franciscan 

rocks in the northwest corner of the region the alternating beds of 

sandstone and shale closely resemble the strata in the lower portion 

of the Knoxville-Chico and are difficult to separate from them. If a 

larger portion of the Franciscan are.as were covered by these unaltered rocks the formation would not be as easily'distinguishable as it 

is. stated to be at the beginning of this paragraph. In fact, the 

dividing line between the Franciscan and Knoxville-Chico has been 

drawn arbitrarily, and it will require further work to discover their 

true relations. It is possible that some of the dark shale and sandstone strata that appear at the base of the Knoxville-Chico in other
KNOXVILLE-CHICO EOCKS. 51

parts of the district, which have not been distinguished from that 

terrane owing to the absence of associated metamorphic rocks, may 

belong to the Franciscan, but the presence or absence of associated 

metamorphic rocks has been assumed as a basis of distinction between 

the formations.

The Franciscan beds in the northwestern corner of the district are 

chiefly sandstone. This rock is hard, gray, of medium coarseness, 

and somewhat thinly bedded and laminated so that it breaks into 

flat angular fragments. In places it appears to have undergone a 

process of alteration into a more quartzitic variety or. to have been 

given a banded or flaky texture, as the result of crushing and elongation of the grains. The sandstone is interbedded with dark, finegrained, thinly laminated clay shale, the laminse of which are in 

places curved and smoothed as if by crushing. These rocks are 

exactly similar to those of the Franciscan farther north, in the

mountains south of San Francisco Bay. Intimately associated with 

these beds are bluish glaucophane-bearing and micaceous schists in 

small patches. Jasper of green and variegated colors and both 

massive and banded structure is interbedded with the sandstone and 

shale in huge lentils. It was not observed within the area mapped, 

but forms striking outcrops farther west, especially in a group of 

picturesque buttes toward the head of Jacalitos Creek.

The serpentine covers a much larger area and extends far beyond 

the limits shown on the map, over a continuous stretch of high 

mountain country. The area that could be observed from the region 

at the head of Joaquin Ridge was estimated to be at least 40 square 

miles, and it is thought to be much more extensive. The Franciscanformation and associated rocks are considerably mineralized and 

contain deposits of cinnabar, asbestos, and the newly described gem 

mineral benitoite. 0

IMPORTANCE WITH RELATION TO PETROLEUM.

The rocks of the Franciscan are not known to contain any petroleum. The formation is of different character from the .formations 

in which the oil is found and has no direct relation to them. Even 

if it had once been a source of petroleum the disturbance that it 

has undergone could have allowed little to remain.

KNOXVILLE-CHICO ROCKS (CRETACEOUS).

GENERAL DESCRIPTION.

The next to the oldest terrane exposed in the Coalinga district is 

a thick series of strata of sandstone, shale, and conglomerate overlying the Franciscan formation and covering a wide belt for the

a Louderback, G. D., Benitoite, a new California gem mineral, with chemical analyses by W. C. Biasdale: Bull. Dept. Geology Univ. California, vol. 5, July, 1907, pp. 149-153. Also Arnold, Ralph, Notes 

on the occurrence of the recently described gem mineral benitoite; Science new sen, vol. 27, Feb. 21, 

1908, pp. 312-314.
52 COALINGA OIL DISTRICT, CALIFORNIA.

most part west of the foothill region. It forms the high ridges bordering the Coalinga district on the west and may be easily recognized 

by the dark, thinly bedded, compact shale and sandstsne of its lower 

portion and the massive drab concretionary sandstone of its upper 

portion. These strata are of Cretaceous age and comprise part or 

all of the two formations well known elsewhere on the west coast as 

Knoxville (Lower Cretaceous) and Chico (Upper Cretaceous). Owing 

to the insufficiency of fossil or stratigraphic evidence as yet obtained 

in the Coalinga district to form the basis for a separation between 

these two formations, they are mapped and described together for 

the present.

The Horsetown formation, which forms the middle portion of the 

Cretaceous in the standard Coast Range section, is not known to be 

represented in the Coalinga district, although it is not impossible 

that a portion of the great thickness of nonfossiliferous Cretaceous 

strata may be the equivalent of this formation. No evidence, however, has yet been found of its presence in this portion of the Coast 

Ranges.

A conservative estimate places the total thickness of the strata 

mapped as Knoxville-Chico at 12,800 feet. The maximum thickness is 

probably much greater. This succession of strata may be divided lithologically into three main divisions. The total thickness of the middle 

and upper divisions, which are probably to be referred together to the 

Chico formation, is at least 9,500 feet. A thickness.of 8,300 feet is measurable in single sections, and even greater thicknesses may be found 

in single sections of the Knoxville-Chico as a whole. It is likely that 

at least two unconformities separating the Knoxville-Chico beds into 

important stratigraphic groups will be made out on further study. 

Their relation likewise to the Franciscan below will in all probability 

be found to be an unconformable one. They are overlain unconformably by the Tejon (Eocene) and the later formations.

The, Knoxville-Chico' areas were not studied in detail, but it is 

thought best to record such partial information as has been obtained 

as a guide to future work. The line of separation of the lower 

and upper divisions that is, the line of the conglomerate zone to be 

mentioned is shown roughly on the geologic map (PL I) along the 

flank of Juniper Ridge and Curry Mountain. The line between the 

middle and upper divisions is shown on both arms of the White 

Creek syncline, being marked on the south arm by the Los Gatos 

Creek fault line.

LOWER DIVISION.

DISTRIBUTION AND CHARACTER.

A zone of coarse conglomerate varying in thickness from less 

than 100 to over 1,000 feet extends intermittently from the summit 

of Juniper Ridge south of Los Gatos Creek to a point south of
KNOXVILLE-CHICO BOCKS. 53

Reef Ridge in Big Tar Canyon. It is overlain and underlain, in 

appearance conformably, by the thin-bedded dark shale and sandstone of the lower half of the Knoxville-Chico. The portion of the 

terrane lying below this conglomerate is here classed by itself as the 

lower division. The strata of this division are well exposed in the 

upper portion of Alcalde Canyon and on Juniper Ridge to the north 

and Curry Mountain to the south. There a thickness of at least 2,000 

feet of alternating thin beds of grayish-black shale, shaly sandstone, 

and fine sandstone of a dark-gray color underlies the conglomerate. 

At the base of these predominantly shaly beds there is an abrupt 

change in the rocks to massively bedded sandstone which forms the 

prominent ridge of Curry Mountain and the southern end of Juniper 

Ridge at the western edge of the mapped area, as shown in Plate V, A. 

This sandstone is iron-gray, hard, homogeneous, of medium grain, 

and only rarely pebbly, jmd has a thickness of about 300 feet. Below 

it, on the west side of the ridges mentioned, on the steep flank represented in the center of Plate V,-A, outside of the mapped^area,similar 

shale beds to those above the sandstone begin abruptly and make up 

a thickness of at least 600 feet. How much more there may be is 

not known, as the series was not examined, but it is thought that the 

lowest beds in the Knoxville-Chico in this section can not be much 

more than 800 to 1,000 feet below the sandstone of the ridge. Thus 

the total thickness of the lower division as exposed in the Alcalde 

Canyon section is between 3,100 and 3,500 feet. The base of the 

lower division is not known to be exposed anywhere within the area 

shown on the map, nor is any portion of the division known elsewhere 

than in the vicinity referred to and in the region south of Reef Ridge 

below the conglomerate near the head of Big Tar and Garza creeks. 

In that region a complex mingling of rocks of doubtful ages occurs, 

among which some, such as dark-blue clays and red shales, are not 

similar to others known in the district. These rocks are supposedly 

of Cretaceous age, and are so mapped.

EVIDENCE OF AGE.

Fossils of Knoxville (Lower Cretaceous) age, such as Aucella 

crassicollis Keyserling and Belemnites impressus Gabb, have been 

found in beds of dark shale in the Devils Den region not many miles 

south of the Coalinga district, and there is little doubt that the 

lower division of the rocks here described as Knoxville-Chico is at 

least in part the equivalent of the Knoxville formation. It is possible 

that the great beds of conglomerate mark the base of the Chico or 

Upper Cretaceous and that the whole of the lower division below this 

line of'separation represents the Knoxville formation.
54 COALINGA OIL DISTRICT, CALIFORNIA. ;

MIDDLE DIVISION. 

DISTRIBUTION AND CHARACTER.

The middle one of the main divisions into which the KnoxvilleChico rocks are divisible upon lithologic grounds comprises a thick 

series of alternating thin beds of dark shale and sandstone with the 

above-mentioned heavy conglomerate at its base, and with the 

characteristic massive, concretionary sandstone beds that form the 

upper division overlying. Its thickness, including the conglomerate 

zone, measures at least 4,800 feet in the Alcalde. Canyon section and 

considerably more farther northwest on the flank of Juniper Ridge, 

because in the former section the upper portion is covered up by the 

overlapping Miocene and the full thickness can not be measured. 

The conglomerate is locally extremely variable and is not continuous. 

It may in places be traced directly into massive sandstone or even 

into thinly bedded sandstone and shale, as along Alcalde Canyon 

between 2 and 3 miles west of Alcalde. It represents throughout the 

district, however, an important stratigraphic horizon characterized 

by a coarsening of the sediments. On the northeast side of Alcalde 

Canyon and again about 4 miles south of the confluence of Los Gatos 

and White creeks it is a deposit of extremely coarse and well-hardened 

conglomerate 200 to 300 feet in thickness. Near the head of Big Tar 

Canyon, at the west edge of the mapped area, a thickness of 1,200 

feet or more of coarse, hard conglomerate occurs within the Cretaceous shale, probably at the same position in the series. In this 

vicinity it runs out of the area shown on the map and does not 

appear within it again south of Curry Mountain. The dark shale 

above it is continuous along the southwest side of Reef Ridge and the 

conglomerate probably continues likewise. The thin-bedded shale 

and sandstone of the middle division are well exposed in the lateral

ridges of Joaquin Ridge south and east of the serpentine area, and a 

heavy zone of massive conglomerate exposed near the head of White 

Creek may be the equivalent of the basal conglomerate elsewhere. 

The rocks of this division cover most of the north and northeast 

flanks of Juniper Ridge and Curry Mountain. South of Curry Mountain there is no evidence of the relations of the different members of 

the Knoxville-Chico such as is exposed farther north, the Cretaceous 

being covered up unconformably by the Miocene beds southward 

to Jasper Canyon. On Reef Ridge south of Jasper Canyon the upper 

portion of the Knoxville-Chico is lacking, and there is little direc't 

evidence to indicate how large a portion is absent. The dark thinbedded shale and sandstone of Reef Ridge may, however, be correlated with fair assurance with the middle member of the KnoxvilleChico farther north, because it is similar in lithologic character and 

because it is underlain in the region of Big Tar Canyon by the great
U. S. GEOLOGICAL SURVEY

A. WESTERN FACE OF CURRY MOUNTAIN, FORMED BY CRETACEOUS STRATA.

Probably a fault scarp. Looking south across Waltham Creek, which cuts through ridge on left; Waltham 

Valley on right and crest of Diablo Range in distance. Photograph by Ralph Arnold.

1',. UNCONFORMITY BETWEEN TEJON FORMATION AND VAQUEROS SANDSTONE

3 petroleum migrates from shales below and collects in sand and gravel above to form oil : canyon of Laval grade, 8£ miles north of Coalinga. Photograph by Ralph Arnold.
KNOXVILLE-CHICO ROCKS. 55

conglomerate zone before mentioned. The Cretaceous strata on 

Avenal Ridge are thought to belong chiefly to the middle division.

EVIDENCE OP AGE.

The beds of the middle division are for the most part nonfossilferous, but here and there a few fossil mollusks are to be found in 

thin beds of conglomerate or scattered through the shale and sandstone. The fossils that have been obtained from this division of the 

Knoxville-Chico are listed under localities 4, 5, 6, and 10 (p. 60). 

Locality 11 is probably also in this division and locality 9 is possibly 

so. Among the fossiliferous beds of which the horizon has been 

stratigraphically determined those of localities 5 and 6 are the lowest, 

being about 2,000 feet below the top of the division, and the fossils 

prove the Chico or Upper Cretaceous age of the beds at least as far

down in the terrane as this. As no break seems to occur in the

middle division the whole is probably referable to the Chico, and 

the basal conglomerate the indication of a great time break between 

these beds and those of earlier Cretaceous time.

UPPER DIVISION.

DISTRIBUTION AND CHARACTER.

The uppermost of the three divisions .of the Knoxville-Chico is 

predominantly concretionary sandstone in the lower part and shale 

in the upper part, and has a thickness of at least 4,700 feet. It is not 

known to be exposed in any but the northern portion of the district. 

It is separable into several members which show diversity of lithologic 

character, but no evidence points to any but a conformable relation 

between these members. On the contrary, the seeming intergradation between them and the recurrence at different horizons of peculiar 

types of deposits such, for instance, as the concretionary sandstone indicates continuity of deposition. Taken as a whole the 

upper division is strikingly distinct from other formations in the district and seems to represent a separate stratigraphic unit, although 

no unconformity has been made out at its base. 

1 The lower half of the upper division consists chiefly of massive 

sandstone beds, often weathering cavernous, that stand out prominently and display the structure on the sides and tops of the ridges 

north of Los Gatos Creek and west of Coalinga. The sandstone is 

usually drab, medium grained, and not very hard. The rocks of this 

division may be easily recognized by these characteristic outcrops 

and by the numerous large, hard reddish-brown concretions of which 

the sandstone is full and which weather out and remain in patches 

upon the surface as shown in Plate IV, B. These concretions are of 

various forms, oval, round, flat, and lens-shaped, and of various
56 COALINGA OIL DISTRICT, CALIFORNIA.

unsymmetric shapes, and have a tendency, as noted by F. M. Anderson, "to split horizontally or to fall apart in concentric shells or 

laminae." They vary from small sizes up to a thickness of 8 or 10 

feet. The prominent sandstone strata are separated by softer beds 

and zones of sand -and light-colored shale, which are poorly exposed. 

Thin seams of calcareous shale and sand are at some points interbedded with the softer beds. Locally the sandstone is conglomeratic. 

At the base of this member of the Knoxville-Chico the massive 

sandstone beds give place to thinner beds alternating with finergrained sandstone and shale, and these grade over into the thin-bedded 

series described as the middle division. The transition takes place 

within a few hundred feet and in places a fairly sharp line can be 

traced between the beds that are chiefly sandstone and those in 

which the thin layers of fine grain predominate.

Above the succession of concretionary sandstone beds, and forming the upper half of the upper division of the Knoxville-Chico, 

comes a less prominent and less uniform succession of beds in which 

shale is predominant. These beds form the uppermost Cretaceous 

exposed within the Coalinga district and are only with difficulty 

separable from the overlying Eocene beds. This upper half of the 

upper division consists of two main members predominantly of shale, 

each approximating 1,000 feet thick, separated by a much thinner 

but more prominent member of concretionary sandstone, in general 

similar to that lower down. Both of the shale members form belts 

of low topography, whereas the intermediary sandstone forms a row 

of hills separating them.

The lower of the two shale members has few exposures but is 

notable for the presence in it of different kinds of deposits, such as 

blackish, thinly-bedded clay shale and yellowish and whitish calcareous and arenaceous shale and sand, and for the presence of

Ammonites, Baculites, Inoceramus, and other fossils, which weather 

out m a fragmentary state on the surface of the clayey soil. According to a personal communication received from Mr. F. M. Anderson 

it is from this shale member that he obtained the fauna listed from 

"the yellow shales below the concretionary sandstones" in his paper 

on the Diablo Range.0 This fauna is given on page 61.

The sandstone separating the two shale members varies from 200 

to 300 or 400 feet in thickness and consists of yellowish-gray and 

brown sandstone full of large brown concretions. It is of the same 

type as the characteristic Chico concretionary sandstone farther 

down in the section, but differs slightly in that the outcrops have in 

general a more brownish aspect, and that the concretions are of 

larger average size and in many places have the character of elongated 

layers. This sandstone is without fossils so far as known. It occurs

oProc. California Acad. Sci., 3d ser., Geology, vol. 2,1905, .p. 161.
KNOXVILLE-CHICO ROCKS. 57

typically on the 2,500-foot hiH'l£ miles northwest of Oil City, whence 

it is traceable northward beyond the northern edge of the area 

mapped and southwestward nearly to Los Gatos Creek.

The uppermost member is one of particular interest owing to its 

individuality among the known types of Cretaceous deposits, its large 

content of organic material, its petroliferous nature, and its similarity 

to the Eocene beds. .It is at least 1,200 feet thick and consists principally of shale, but has a considerable admixture of sand and sandstone. 

For convenience it will be referred to as a whole as the purple-shale 

member. The most characteristic beds of this zone are of purplishbrown, fairly hard, thinly bedded, both siliceous and calcareous clay 

shale, in which the tests of Foraminifera are very abundant. This 

shale bears a resemblance to some of the less siliceous shale in the 

upper part of the overlying Tejon (Eocene), especially to that shale

as it occurs in the southern part of this district, and is not unlike

some argillaceous phases of the Monterey shale (middle Miocene) of 

the outer Coast Ranges and the shale mapped as Santa Margarita (?) 

(middle Miocene) along Reef Ridge and at other points in this district. It contains local thin, generally lenticular layers of grayish 

and yellowish calcareous shale and also large oval nodules of grayishwhite limestone. These nodules are usually several feet in dimensions, and one was observedjis much as 8 feet long and 2£ feet thick. 

Seams of sandy shale and lenses of sand occur sparingly.

Purple shale such as that described is especially characteristic of 

the upper half of the member and forms a well-marked belt of low 

topography, and locally bare purplish slopes dotted with dark-green 

juniper .and oak trees, at Oil City and both northeast and southwest 

of that place.

In the lower half of the member the shale is less markedly of the 

purplish type and ordinary grayish-black clay shale, like that below 

the underlying concretionary sandstone, is an important constituent. 

Most of the shale, however, has at least a trace of the purplish color 

and contains Foraminifera. Calcareous layers and lenses occur 

throughout. The beds are characteristically much crushed, filled 

with seams and veins of selenite along the small cracks, and traversed 

by irregular sandstone dikes. Somewhat irregular zones of whitish, 

yellowish, and grayish fine-grained sand and sandstone are interbedded with the shale in the lower part of the member. For the 

most part these are more varied than the sandstone characteristic 

of lower portions of the Chico, are more thinly bedded, and lack the 

large brown concretions. Some of the true concretionary sandstone 

is interbedded with the'shale, however, and no sharp line of separation is to be drawn between the purple-shale member and the underlying concretionary sandstone. The contact is shown on the map 

(PI. I) by the green line bounding the west side of the possible productive territory north of Los Gatos Creek.
58 COALINGA OIL DISTRICT, CALIFORNIA.

Above the purple shale of the uppermost Cretaceous lie dark clay 

and clay shale beds aggregating several hundred feet in thickness, 

which appear to form an upward continuation of the shale of the 

Chico, but which are mapped with the Tejon (Eocene). Fossils 

recently found near the northern edge of the Coalinga district show 

that the higher of these beds belong with the sandstone of the Tejon 

above; but there is reason to believe that 200-feet or so of beds at 

the base belong in the Chico. Their inclusion in the Chico would 

make no appreciable difference in the mapping and for the present 

the line is drawn at the top of the purple shale, which is the only line 

that could' be mapped with any approach to consistency. Whether 

the line of separation between the Cretaceous and Tertiary occurs at 

the top of the purple shale or somewhat higher, within the darker clay 

shale, it is noteworthy that it should occur within a zone of fine sediments and be marked by no break of evident stratigraphic importance.

However, in spite of the apparent transition between the shale of 

the Cretaceous and that of the Eocene in the northern part of the 

Coalinga district, it is believed that they are separated by an unconformity. The evidence of this is the progressive disappearance of 

the upper members of the Knoxville-Chico southward in the district, 

whereas the basal Tejon is believed to represent a fairly constant horizon. The upper half of the upper division of the Knoxville-Chico 

has been recognized only north of Los Gatos Creek, and south of 

Waltham Creek the whole of the thick concretionary sandstone terrane has disappeared likewise, the Tejon where next exposed south 

of Jacalitos Creek resting directly upon dark shales of a lower portion 

of the Knoxville-Chico. The beginning of the disappearance of the 

upper members of the Cretaceous is indicated by the gradual thinning of the purple-shale member at the top southwestward from Oil 

City until it is finally lost near Los Gatos Creek. This thinning and 

disappearance of the members is probably the effect of erosion upon 

them before the deposition of the Eocene.

In the preliminary report on the Coalinga district 0 the shale and 

interbedded sandstone here described as the uppermost member, of 

the Chico (Upper Cretaceous) was treated as part of the Tejon 

(Eocene) owing to its similarity to and striking appearance of continuity with the beds of that age. The line between the Cretaceous 

and Eocene was arbitrarily drawn at the top of the concretionary 

sandstone immediately underlying this member. During the course 

of work done north of the Coalinga district by the junior author of the 

present paper and R. W. Pack in 1909 it was discovered that this shale 

zone. is part of the Cretaceous, the fact being especially confirmed 

for the Coalinga district by the finding of Cretaceous fossils such as 

Baculites and Hamites in calcareous nodules in the purple shale

 : ! 

 oBull. U. S. Geol. Survey No. 357,1908.
KNOXVILLE-CHICO BOOKS. 59

within one-half mile northwest of Oil City (on the west side of the 

SW. J sec. 17, T. 19 S., R. 15 E.).. The stratigraphic relations and 

fauna of this shale will be further discussed in a report that is in 

preparation on the territory north of the Coalinga district.

The beds here referred to as the purple-shale member of the Chico 

(Upper Cretaceous) were mentioned by F. M. Anderson in his first 

paper on the Diablo Range. 0 He considered them to represent the 

middle portion of the Eocene of this region and correlated them with 

the shale on Reef Ridge in the southern part of the Coalinga district, 

which was termed by him the Kreyenhagen shales and which is described in the present paper as the upper member of the Eocene. In 

a paper published subsequently 6 the purple-shale member was described as the lower shales in a fourfold division of the Eocene, the 

underlying concretionary sandstone, which outcrops typically on the 

2,500-foot hill northwest of Oil City, being described as the lower

sandstone and considered as the base of the Eocene. Higher beds 

than any here referred to the purple-shale member were included in 

F. M. Anderson's description, as is shown by the fact that Eocene 

fossils were stated to occur in this division.

The upper division of the Knoxville-Chico presents approximately 

the following section on Joaquin Ridge:

Section of upper division of the Knoxville-Chico rocks 10 miles north of Coalinga.

Feet.

The purple-shale member: Petroliferous, purplish and blackish, foraminiferal, siliceous clay shale, with calcareous nodules; decidedly purple and 

siliceous in the upper part; more argillaceous and intermingled with whitish and yellowish sand and sandstone in lower part; overlain by clay and 

sand of Tejon (Eocene)................................................ 1,200

Hard golden-brown sandstone, largely made up of irregular elongated concretions, forms 2,500-foot hill northwest of Oil City......................... 200±

Soft zone of whitish-gray and yellowish-gray sand and dark clay shale,, with 

occasional thin layers of hard brown sandstone and hard calcareous shale; 

forms low topography, few outcrops, and loose, crumbly soil............... 1,000

Hard brown sandstone with large reddish-brown concretions of hard sandstone, 

interbedded with whitish and yellowish-gray sand full of small bullet-like 

concretions of gray sandstone........................................... 300

Light-colored calcareous shale............................................ 200

Hard brown sandstone with some large concretions, interbedded with much 

less prominent beds of yellow sand.. .................................... 300

Massive beds of fairly soft yellowish-gray sandstone full of large dark-brown 

concretions, forming outcrops such as that shown in Plate IV, B. Softer 

beds of sand and clay that do not outcrop are interbedded. This is the 

top of the typical massive concretionary sandstone of the lower portion 

of the upper division of the Knoxville-Chico............................. 200

Chiefly massive yellowish-gray sandstone like the last, with several zones in 

which the concretions are abundant and with some conglomerate zones; 

forms rocky pinnacles; overlies thinly bedded shale. and sandstone of 

middle division........................................................ 1, 300+

4, 700+

« Proc. California Acad.Sci., 3d ser., Geology vol.2 1905,p. 163. 

6 Idem, 4th ser., vol. 3,1908, pp. 13-14.
60 COALINGA OIL DISTRICT, CALIFORNIA.

EVIDENCE OF AGE.

Fossils of Chico (Upper Cretaceous) age have been found by the 

writers at various localities in sandstone, conglomerate, and shale in 

this upper division, of the rocks mapped as the Knoxville-Chico. 

Most of them are in a poor state of preservation. The following 

species, all believed to be characteristic of the Chico, have been 

found in the upper and middle divisions within the district: a

Chico ( Upper Cretaceous) fossils from the Coalinga district.

PELECYPODA.

Avicula lingUEeformis Evans and Shumard ..............

Inoceramussp..indet. ..................................

Meekia sella Gabb ......................................

Meekia sella? Gabb ....................................

Solen? sp ..............................................

Tellina? ooides Gabb. ..................................

GASTEROPODA.

Perissolax brevirostris Gabb ...........................

Volutoderma gabbi (White) ............................

CEPHALOPODA.

Baculites chicoensis TrasK. ..........................

Pachydiscus n. sp.o ................................... %

1 ?

y

X

3

X

y

y

y

4

y

y

y

5

v

0 7.

v

8. ft in,

y

y

11

X

a Fragments of indeterminate ammonoids have been found by several persons in the hills northwest of 

Coalinga.

1. Ten miles N. 27° W. of Coalinga, at elevation of 2,000 feet, on summit of long ridge north of Los Gatos 

Creek, in center of S W. J sec. 15, T. 19 S., R. 14 E. About 1,000 feet stratigraphically above base of Chico 

concretionary sandstone series in a bed of conglomerate and pebbly micaceous sandstone.

2. Hills north of Los Gatos Creek; probably same locality as I.

3. About one-fourth mile north of 1, on the same ridge. About 600 feet stratigraphically above base of

ChiCO Concretionary sandstone series in a conglomerate bed through massive sandstone.

4. On long ridge 3} miles north of junction of White and Los Gatos creeks, on north side of summit of 

2,054-foot hill. Several hundred feet stratigraphically below base of Chico concretionary sandstone series 

in a coarse conglomerate through sandstone and shale.

5! Two miles north of White Creek, at elevation of 3,100 feet, one-fourth mile southeast of summit of 

3,425-foot hill, southeast corner sec. 10, T. 19 S., R. 13 E. About 2,000 feet stratigraphically below base of 

concretionary sandstone series in a bed of pebbly sandstone through the shale series.

6. Two miles north of White Creek, at elevation of about 2,800 feet, on long ridge three-fourths mile 

south of 3,300-foot hill, east side of NE. J sec. 14, T. 19 S., R. 13 E. -About 2,000 feet stratigraphically 

below base of Chico concretionary sandstone series in a pebbly sandstone through shale series. Probably the same horizon as 5.

7. Hills northwest of Coalinga; locality indefinite. Specimens owned by J. H. Webb.

8. Float in creek 6 miles northwest of Coalinga, north of White Creek.

9. In Alcalde Hills, 3£ miles west-southwest of Coalinga in Anticline Canyon, central part of sec. 2, T. 21 

S., R. 14 E. At contact of Cretaceous and Miocene in a thin bed of pebbly sandstone through thinly bedded 

sandstone and shale.

10. Alcalde Canyon, one-half mile southwest of Alcalde. In shale. .

11. Head of Canoas Creek outside of the area mapped. About 1 to 2 miles east of the southeast end of 

Castle Mountain. In sandstone and shale.

The following additional species are reported by F. M. Anderson b 

from nodular limestone in the shales below one of the upper con-

<i The fossils mentioned on p. 58 as occurring in the purple-shale member were found too recently to admit 

of their being listed here.

6 Proc. California Acad. Sci., 3d ser., Geology, vol. 2, No. 2,1905, p. 161.
KNOXVILLE-CHICO ROCKS. 61

cretionary sandstone zones of the upper division of the KnoxvilleChico at different points in the Coalinga region.

PELECYPODA.

Glycymeris veatchii Gabb-j-Pectunculus

id. 

Inoceramus whitneyi Gabb.

GASTEROPODA.

CEPHALOPODA.

Baculites sp.

Desinoceras sp., related to D; hoffmanrii

Gabb. 

Lytoceras sacya Forbes.

Architectonica sp. 

Cinulia obliqua Gabb. 

Gyrodes sp.

The fossils prove the Chico age of the rocks throughout the upper 

division, leaving only a small thickness of strata at the summit, between the f ossilif erous Chico beds and those containing Tejon (Eocene)

fossils, of which the age is in doubt. These strata, which are at 

most a few hundred feet in thickness, might be either Chico or 

Tejon, or a transitional series corresponding in age to the Martinez 

formation in the vicinity of San Francisco Bay. A line of separation is drawn in the transitional portion on the basis of lithology, 

and it is believed that the beds below are with little doubt of Chico 

(Upper Cretaceous) age and those above, with the possible exception 

of 200 feet or so at the base, of Tejon (Eocene) age.

IMPORTANCE WITH RELATION TO PETROLEUM.

The purple-shale member of the Knoxville-Chico (Cretaceous) is 

of especial interest as the reservoir and presumably the source of the 

large amount of light oil that has been produced by the Oil City field. 

The wells obtain their oil from the sandy zones in the lower portion of 

the member and possibly in places also from the shale itself. The 

occurrence of petroleum in this formation affords the first instance 

known on the west coast of richly productive petroleum-bearing beds 

in the Cretaceous. The presence of oil may be detected in many 

places in the shale by the odor, especially in the calcareous layers and 

nodules, and it is not improbable that the purplish and chocolatebrown colors appearing throughout the member are due to petroleum staining. A seepage of light oil from the shale of this member 

within one-half mile northwest of the camp now called Oil City led to 

the first drilling for oil in the region and the consequent development 

of the Coalinga field. Another large seepage occurs near the forks 

of a canyon less than 2 miles northeast of Oil City (NW. I sec. 9, T. 

19 S., R. 15 E.).° There the oil is exuding from beds of dark clay in 

the middle of the clay zone already mentioned as overlying the purple-shale member. The beds at the horizon of the seepage are prob-

<* Owing to an error in the engraving this seepage is shown one-fourth mile too far east on the geologic map 

(PI. I).
62 COALINGA'OIL DISTRICT, CALIFORNIA.

ably in the Tejon (Eocene), but can not be far above the top of the 

Knoxville-Chico (Cretaceous), being, at most, within 400 feet stratigraphically above the top of the purple shale, from which the oil with 

little doubt comes. The seepage may be an indication of the horizon 

of the line of unconformity between the Cretaceous and Eocene.

No evidence of oil is known in the KnoxvillerChico strata at any 

horizon lower than the base of the purple-shale member. It is possible that traces of oil are to be found in them, as in most sedimentary 

rocks, but there is nothing to indicate that it will ever be discovered 

in this region in a quantity sufficient to make it of economic importance. No petroleum has been found by wells penetrating strata 

lower than the purple-shale member.

TEJON FORMATION (EOCENE}. 

GENERAL DESCRIPTION.

The formation mapped as the Tejon in the Coalinga district is made 

up entirely of sedimentary strata that dip toward the great valley in the 

monocline along the eastern flank of the mountains and are exposed 

on the surface in a narrow discontinuous belt between the Cretaceous 

beds which underlie them and those of the Miocene which overlie 

them. The beds so mapped have a thickness of 1,600 to 1,850 feet 

and are divisible into two main members of approximately equal 

thickness a lower one consisting of sandstone in the southern part 

of the district and of dark clay shale and sand in the northern part, 

which is certainly of Eocene age, with the possible exception of a 

small thickness at the base, and an upper one of light-colored organic 

shale which affords few species of fossils and no conclusive evidence 

as to its age. This upper member may represent either Eocene or

Oligocene time, but the facts tliat there seems to be a gradation from

the beds of the lower member into those of the upper and that the 

two invariably occur together in this region favor its assignment 

to the Eocene. It is made up of thin beds of whitish and purplish 

siliceous, argillaceous, and locally calcareous shale, which is easily 

recognizable and which lends individuality to the formation. The 

shale is very similar, especially in some places, as north of Coalinga, 

to the siliceous shale of the formation along Reef Ridge that is described later as the Santa Marg.arita (?) formation, and the two must 

not be confused. It is also somewhat similar to the purple shale of 

the upper Chico. Where the Tejon formation is thick, shale and clay 

form a greater proportion of the whole than the sandstone, but a 

great local variation in the thickness of this member is noteworthy 

because due to the great unconformity between it and the overlying 

Miocene beds. A large portion of the formation had been worn away 

before the Vaqueros (lower Miocene) sandstone was deposited on 

its upturned surface. It is possible that an unconformity occurs
TEJON FORMATION. ' 63

within the beds mapped as Tejon at the base of the upper shale, but. 

no discrepancy in dip between the beds of the two divisions has been 

found, and the succession of beds is seemingly continuous.

As already pointed out, an unconformity exists between the Chico 

(Upper Cretaceous) and Tejon (Eocene) beds, in spite of the facts, 

that no sharp line of demarcation is to be drawn between the Tejon 

and the underlying Chi«o in the. northernmost part of the district 

and that there appears to be a gradation from the beds of the former 

into those of the latter, as if they had been formed during a continuous period of sedimentation. In the southern portion of the district 

the Tejon overlies unconformably beds that belong to an earlier 

portion of the Cretaceous, either lower Chico or Knoxville, thus proving that a period of land' conditions and orogenic disturbances preceded the Tejon.

Tejon group was the name applied by J. D. Whitney to the fossiliferous strata in the vicinity of Fort Tejon, Kern County, and Martinez, Contra Costa County, which were included by Gabb under 

his Division B, or Upper Cretaceous.0 As the result of later studies 

the fossils of this formation are now considered to be of Eocene age. 

Strata of the same age occur extensively in the region of Carquinez 

Straits, east of Mount Diablo, and have been found at a number of 

different points along the western border of the San Joaquin Valley, 

notably at New Idria and in the region discussed in the present 

paper. It may therefore be said that in all probability an almost 

continuous belt of Tejon sedimentary*rocks extends near the valley 

edge between Martinez and the type locality in Kern County, this 

formation composing an important middle member, in the succession 

of terranes of which the easternmost mountain group of the Coast 

Ranges is built.

The rocks in this belt are chiefly of marine sedimentary origin and 

consist in the main of sandstone and shale. They are in many 

places such as to indicate a shallow-water or brackish-water origin, 

and lignitic seams are very characteristic.

The Eocene of the southern portion of the Diablo Range was 

described by F. M. Anderson, in his first paper 6 relating to this region, 

as made up of three members, namely, the Avenal sandstone at the 

base, the Kreyenhagen shales in the middle, and the Domijean sands 

at the top. The first two of these names were applied to the two 

members of the Eocene along Reef Ridge in the southern half of the 

Coalinga district. North of that region those members were correlated 

with the beds which have been above described as the upper concretionary sandstone and the overlying purple-shale member of the 

Chico (Upper Cretaceous). The third of these names was applied to

o Geol. Survey California, Paleontology, vol. 2,1869, preface, p. xiii. 

6 Proc. California Acad. Sci., 3d ser., Geology, vol. 2, pp. 162 et seq.
64 COALINGA OIL DISTKICT, CALIPOENIA.

the Eocene sandstone near the Domengine ranch, just north of the 

Coalinga district, this sandstone being considered to represent an 

upper sandstone zone. In the present paper this sandstone is 

treated as the upper portion of the lower member, which is regarded 

as the correlative of the lower member in the southern part of the 

district. Although it may prove advisable to retain one or two of 

these names in future, the name Tejon formation is used in the 

present paper to include the whole succession of beds, for the sake of 

simplicity and to avoid confusion.

DISTRIBUTION AND LOCAL CHARACTER.

There are three separated areas in which the Tejon is exposed, one 

in the oil field north of Pleasant Valley, one on the eastern border of 

the Alcalde Hills just west of Coalinga, and the other along Reef 

Ridge. Between the Alcalde Hills and Reef Ridge it is covered up, 

as is the Cretaceous below, by the overlapping Miocene beds.

TEJON NORTH OF PLEASANT VALLEY.

In the northern region the Tejon is typically exposed in the hills 

directly north of Coalinga, in the vicinity of the camp called Oil City. 

The formation has a thickness of at least 1,850 feet where most completely exposed on the flanks of Joaquin Ridge, comprising a lower 

sandy and clayey member'850 feet thick and an upper organic 

shale member at least 1,000 feet thick.

The beds are markedly unconformable with those of Miocene age 

above, the unconformity being well displayed in the hills 8£ miles north 

of Coalinga and near the point pictured in Plate V, B. There the 

low-dipping and comparatively little-disturbed Vaqueros (lower Miocene) sandstone rests on the highly tilted, overturned, and fractured

shale of the upper part of the Tejon. The unconformity, is likewise 

evident in other portions of the hills, yet in places there is little variation in 'dip between the two formations, and the relation might be 

mistaken for a conformity if the contact were only locally observed. 

This fact illustrates the local nature of .the phenomena in this region. 

Beds that were violently disturbed in one locality before the deposition of later sediments upon them may have been left comparatively 

little disturbed a short distance away, and little reliance is to be put 

in apparent conformities resulting from harmony in angle of dip 

between two foraiations.

The basal clay zone of the Tejon and its relation to the Cretaceous 

beds have already been mentioned in connection with the purpleshale member of the Chico. This zone comprises a thickness of 

about 700 feet and grades upward into a more sandy zone about 150 

feet thick, the two together composing the lower member of the 

Tejon. The clay zone consists of blackish-gray, fairly compact
TEJON FORMATION. 65

fine-grained material and forms a massive, homogeneous deposit 

with inconspicuous bedding planes. It is on the border line between 

clay and shale but partakes more of the nature of clay. Considerable fine sand is intermingled, giving much of the clay a gritty character, and there occur occasional layers and lenses of fine sandstone. 

Tests and impressions of Foraminifera are abundant in this clay, but 

not so abundant as to cause it to lose its predominantly clayeynature or approach in character the more organic shale in the upper 

member of the Chico or the upper member of the Tejon of this region. 

Eocene fossils have been found in the upper portion of the clay zone 

just north of this district,0 but as yet there is no certainty whether 

a small thickness at the base of the zone may not belong to the 

Cretaceous. At the top the clay grades almost imperceptibly into 

a very gypsiferous soft clayey sand which forms the upper 150 

feet of the lower member. This sandy zone comprises alternating layers of varied character light-gray sandy clay, dark clay, 

gray and yellowish sand locally hardened into sandstone, green 

sand, and hard white calcareous nodules. In places the beds are 

more hardened than elsewhere and calcareous sandstone predominates, giving the zone prominence. Tejon (Eocene) fossils have 

been found at a number of points in this zone, both in the sandstone 

and in the calcareous nodules.

The lower member of the Tejon is traceable southwestward nearly 

to Los Gatos Creek and is undoubtedly continuous beneath the 

alluvium with the belt exposed on the west side of Pleasant Valley. 

It becomes somewhat thinner in that direction and the lower clayey 

beds are not persistent as a distinct zone.'

The upper member of the Tejon as mapped forms a prominent 

white belt from the region north of Pleasant Valley to and beyond 

the north edge of the district. Throughout the belt it has an exposed 

thickness of 400 to 1,000 feet, commonly about 700 feet. The variation is due to the erosion that took place before the deposition of the 

Miocene. It is probable that the complete succession of beds as 

originally deposited is nowhere exposed within this region. This 

member consists chiefly of white, siliceous, hard and brittle, thinly 

bedded diatomaceous and foraminiferal shale, interbedded with finely 

fractured, roughly bedded purplish-brown clayey shale, some fine 

and coarse sand, and thin calcareous shale layers. The typical siliceous shale is exposed in the overturned fold shown in Plate XIII, A, 

on the right in Plate VII, A, and with interbedded argillaceous shale 

in Plate V, B. The shale is locally variable in color, assuming different yellowish and reddish tints as the result of staining by petroleum. 

It contains an abundance of crystallized gypsum, with minor amounts

a Owing to the recency of their discovery these have not been listed. , 

88170 Bull. 398 10 5
66 COALINGA OIL DISTRICT, CALIFORNIA.

of alkaline mineral matter and sulphur along the intricate fracture 

planes. Some of the beds are largely composed of gypsum. Dikes 

of sandstone traversing the beds in various directions are so common 

as to be characteristic of the formation. An exposure of the shale 

penetrated by irregular dikes of hard sandstone is shown in Plate 

VI, A.

 An analysis of a compact but comparatively soft and less siliceous 

specimen of chocolate-colored shale from the upper portion of the 

Tejon, near Oil Canyon, made by R. C. Wells, of the United States 

Geological Survey, showed the shale to contain approximately 78 per 

cent of silica. Under a lens it is seen to be composed largely of diatom remains with foraminiferal tests in minor number. The silica 

content is probably chiefly the product of the siliceous skeletons of 

the diatoms.

Southwest of Oil City the Miocene beds gradually overlap more and 

more upon the Eocene, leaving less of it exposed. Owing to lack of 

exposures of the rocks within 1 mile north of Los Gatos Creek, 

where it opens out to Pleasant Valley, the lines of contact drawn there 

are only approximately correct.

TEJON SOUTH OP LOS GATOS CREEK.

. The outcrops of Tejon appear again south of Los Gatos Creek in a 

belt along the base of the foothills facing Pleasant Valley. The formation is conformable in dip with the Chico, and the rocks near the 

contact are fairly well exposed. The line drawn at the top of the 

concretionary beds, which are supposed to be at the top of the Chico 

(Upper Cretaceous), marks the base of some beds of light-yellow and 

white, soft, gypsiferous sand that are taken.as the lowermost Tejon 

of this part of the area. Within 100 feet above this contact occurs

a bed of calcareous sandstone locally greatly hardened and full of 

typical Tejon fossils. At the two coal mines northwest of Coalinga 

the yellow sand at the base of the formation is exceedingly gypsiferous and variable in character, and appears to be a shallow brackish 

and perhaps in part fresh-water deposit. It contains seams of lignite 

and carbonized wood which in former years have been mined. 

Above this sand, which has a thickness of about 200 feet, occur thin 

beds of light-colored, somewhat siliceous hard shale and soft, purplish-brown, gypsum-bearing argillaceous shale composing the upper 

half of the formation. The latter beds are steeply tilted and fractured and their truncated edges are overlain by Miocene beds with 

low dip. The unconformity is well exposed in the canyon of the 

San Joaquin Valley coal mine. At.one place 4 miles northwest of 

Coalinga, .within 500 feet above the base of the Tejon, there is 

exposed a bed of soft diatomaceous shale which probably represents
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE VI

. v

.1. SANDSTONE DIKES IN PETROLIFEROUS SHALE OF THE TEJON FORMATION.

View 15 miles north of Coalinga. Similar dikes are characteristic of this formation. Photograph by

Ralph Arnold.

PETROLIFEROUS SHALE AND SANDSTONE OF TEJON FORMATION BROKEN BY LOCAL FAULT. 

Looking north in canyon of San Joaquin Valley coal mine. Photograph by Ralph Arnold.
TEJON FOBMATION. 67

part of the siliceous zone toward the top of the formation farther 

north, although it .is not impossible that it occurs within the Miocene beds. Owing to the covering of soil over the undulating ground 

at the edge of the plain northwest of Coalinga, the thickness and 

extent of this diatomaceous material, or of the formation as a whole, 

can not be determined. It may be said, however, that the shale portion of the formation has a thickness in this part of the field of at 

least 300 feet below the highest horizon that the unconformably 

overlying Miocene leaves exposed. The Miocene spreads more 

widely over the Tejon farther to the south until the strike of the Tejon 

carries it completely beneath the Miocene beds at a point about 3 

miles west of Coalinga.

TEJON ALONG KEEli1 BIDGE.

Beds of Tejon age appear again on Reef Ridge, where the same

broad lithologic characteristics may be noted a sandy, frequently 

yellowish lower portion and a purplish shaly upper portion although 

many minor differences are evident in the manner of occurrence north 

and. south of the Miocene overlap. The Tejon beds of Reef Ridge, 

as compared with those in the northern locality, are in general more 

indurated and more regular and steeply tilted. The sandstone is more 

massively and regularly bedded and coarser at the base, and the shale 

is of different character and more homogeneous. The formation rests 

uncoinformably on what is with little' doubt a lower portion of the 

Cretaceous. An angular unconformity between the Tejon and the 

Miocene beds above it on Reef Ridge has not been found plainly 

in evidence along the contact, as it is in the Coalinga field, but an 

unconformable relation exists between the two formations here as 

well as farther north, as is shown by the facts that the tilting of the 

shale beds is in general steeper and the disturbance greater than in the 

Miocene above; that the Vaqueros (lower Miocene) overlaps at the 

northwest end of Reef Ridge and rests directly upon the dark shale 

of the lower portion of the Knoxville-Chico; and that the thickness 

of the shale of the Tejon exposed along Reef Ridge is varied owing to 

the overlapping of the Miocene upon different horizons.

The Tejon is exposed typically in the gorges that cut Reef Ridge 

between Zapato Canyon and Big Tar Canyon. The section (fig. 3) 

affords a graphic representation of the succession of beds in the latter 

canyon. The Tejon along Reef Ridge is made up of a basal zone of 

conglomerate varying in thickness from a few feet to over 100 feet, 

of a succession of sandstone beds aggregating about 550 feet in thickness, and of an upper shale portion'of which a thickness as great as 

900 to 1,000 feet is in places exposed. The Tejon becomes thinner 

west of Zapato Canyon and is not known to outcrop in that direction
68 COAL1NGA OIL DISTRICT, CALIFOENIA.

west of Jasper Canyon. Toward the southeast the Tejon passes under 

the overlapping shale of the Santa Margarita (?) formation (upper Miocene) near the extremity of Reef Ridge and disappears entirely. In 

the region mapped around McLure Valley no evidence of it exists. It

PROBABLY KNOXVILLE TEJON 

(Lower Cretaceous) (Eocene)

VAQUEROS SANTA MARGARITA (») JACALITOS 

(lower Miocene) (uppermiddle Miocene) g (early upper Miocene)

"O SCO 1000 1500 2000 FEET

FIGUKE 3. Section of the Santa Margarita (?), Vaqueros, and Tejon formations along the west side of

Big Tar Canyon.

Feet.

a. Gray and brown sand of the Jacalitos formation.

6. Unfossiliferous brown sand and sandy clay, with occasional layers of hard yellowish-brown sandstone, apparently grading into the Jacalitos above and the Santa Margarita (?) below; of doubtful 

age, but mapped as Jacalitos.................................................................. 200

Santa Margarita (?).

c. Soft blue shale at top, grading below into soft brown shale; some brown sand at the top.......... 350

d. Prominent thinly bedded hard white and purplish siliceous shale............................... 100

e. Hard shale similar to that above, grading below into thinly bedded chocolate-colored shale...... 200

650 

Vaqueros. 

f. Soft gray sandstone and sandy shale..... .v...................................................... 200

g. Prominent massive bed of hard gray sandstone, the upper one of "reef beds".................... 10

ft. Less prominent gray sandstone................................................................... 75

i. Very prominent massive bed of hard gray sandstone,the lower one of the prominent "reef beds;"

this and the associated beds are locally fossiliferous (fossil locality 4627)........................ 10

j. Coarse gray and brownish sandstone ............................................................. 150

fc. Thinly bedded hard sandstone and shale, with 20 feet of reddish-brown shale ak the base........ 100

I. Massively bedded, fairly soft grayish-brown sandstone.......................................... 50

TO. Soft grayish-brown sandstone, permeated throughout by veins of petroleum, and with a spring

of heavy black oil at base forming tar......................................................... 200

795 

Tcjon. 

n. Thinly bedded purplish, dark grayish brown, and locally light-brown and yellowish siliceous,

calcareous, and argillaceous shale.............................................................. 700

o. Grayish-brown sandy clay shale............................................°..................... 125

p. Light-gray, yellowish, and brown, locally concretionary and fossiliferous sandstone impregnated

with oil.......................................................................................500

1,325 

Total Santa Margarita (?), Vaqueros, and Tejon ......................................... 2, 770

may have been deposited over much of this region and later removed 

by erosion before the deposition of the Santa Margarita (?), which rests 

directly on the Cretaceous beds. This subject is discussed in the section dealing with the geologic history (p. 174). Rocks of Eocene age
TEJON FORMATION. 69

reappear still farther south on the southwest flank of McLure Valley, 

in the Devils Den region and beyond.

The sandstone of the Tejon may be easily recognized by the prominent line of peaks that it forms along Reef Ridge a few hundred feet 

behind the abrupt frontal escarpment produced by the "reef beds." 

It is for the most part homogeneous, yellowish-gray, medium-grained, 

oil-stained massive sandstone, locally very hard, especially in the 

upper portion, but usually fairly soft. In places it is concretionary 

and weathers cavernous. A characteristic feature of it is that it supports a heavy growth of vegetation as compared with the shale 

above it. It attains its greatest development in the central portion 

of its extent and thins toward the two ends of Reef Ridge.

This sandstone contains typical Tejon (Eocene) invertebrate fossils, 

which place it definitely in this formation and allow its correlation

with the fossiliferous sandstone of the Tejon already described from 

the Coalinga field. At its base it grades into the locally varied conglomerate zone before mentioned, which is taken as marking the base 

of the formation for the reason that it rests unconformably upon the 

dark Cretaceous shale in the region of Big Tar Canyon and the head 

of Garza Creek. Farther west, however, in the vicinity of Canoas and 

Sulphur Spring canyons, the coarse beds at this horizon rest with 

apparent conformity and intergradationupon a great thickness of beds 

of sandstone and soft sandy shale and carbonaceous clay shale that are 

unlike Cretaceous strata of other parts of the district. It is possible 

that this underlying terrane is part of the Eocene that is lacking elsewhere along Reef Ridge, but it is mapped for the present with the 

Knoxville-Chico (Cretaceous). No fossils have been found in it and 

sufficient work has not been done upon it to determine its relations. 

The shale overlying the sandstone of the Tejon is less resistant to 

weathering and forms a belt of low topographic relief between 'the line 

of peaks formed by the lower sandstone and the sharp ridge of the 

Vaqueros (lower Miocene) "reef beds." This belt is marked by few 

outcrops and is almost entirely bare of vegetation, except grass and 

scattered small juniper and oak trees. It is only in the canyons that 

the rocks of this zone are well exposed, and there they are seen to be 

chiefly thin beds of purple shale, steeply tilted and considerably fractured and distorted. At the base the beds of this member are almost 

invariably poorly exposed, but they seem to be somewhat sandy 

through a thickness of about 200 feet, as if representing, a transition 

from the sandstone of the lower member. Above this transition zone 

the beds are fine-grained argillaceous and siliceous shale, of a peculiar 

dark purplish brown, and similar to some of the shale in the upper 

member of the formation north of Coalinga. Thin'laminae of fine 

sand are occasionally intercalated. The shale is usually comminuted 

into fine flakes or locally almost into a powder. It has a black car-
70 COALINGA OIL DISTRICT, CALIFORNIA.

bonaceous appearance in places, this and the purple color possibly 

being due to the impregnation with petroleum. The cracks in the 

shale are frequently lined with sulphur. Toward the top the shale 

becomes yellowish or whitish in places, for example, near and southeast of Big Tar Canyon, and both siliceous and calcareous, the latter 

variety containing innumerable foraminiferal remains. These beds 

bring out still more strikingly the resemblance to the shale member 

north of Coalinga, and indicate that the same horizon is represented in 

both localities. The thickness of beds exposed between the'sandstone of the Tejon and the Miocene varies from place to place along 

Reef Ridge. The maximum thickness that has been found is in the 

neighborhood of Canoas Creek, where it is about 1,000 feet.

FOSSILS AND AGE.

LIST OF FOSSILS.

As indicated by the' following list, the Tejon formation is well 

represented by fossils, and in several localities they are in a fairly 

good or even excellent state of preservation. Among the species 

collected by the writers within the Coalinga district are the following:

Tejon (Eocene) fossils from the Coalinga district.

Name.

FORAMINIFERA.

ECHINODERMATA.

PELECYPODA..

Barbatia morsel Gabb .............................

Corbula parilis Gabb. ..............................

Tellina hornii Gabb ................................

Venericardia st>. indet. ............................

CO 

0

V

X

 ^

CO

Y

10

co

V

v

Y

X

v

v

CO 

CO

v

hco

v

v

o>

co

X

v

v

v

V

v

§CO

V

v

V

<N

to

v

v

y

8CO

^

Y

^

V

o

CO

y

X

V

X

v

V

v

CO

o

v

Tt»

0
TEJON FORMATION. 71

Tejon (Eocene) fossils from the Coalinga district Continued.

Name.

GASTEROPODA.

Turritella paehecoensis Stanton ..............

Turritella u vasana Conrad .........................

CO

CD

 rf

co

V

irf

CO

X

CO

CO

r-1

CO

V

V

X

v

X

o>

o

V

X

X

X

X

1

V

CMCO

V

X

X

si CO

X

X

1

V

X

V

X

X

V

X

CO

S

^

rH

S

4013. About 11 miles north of Coalinga, on west side of sec. 4, T. 19 S., R. 15 E. Top of lower member.

4014. East flank of Alcalde Hills, 3 to 4 miles northwest of Coalinga, along ridge within three-fourths mile 

of San Joaquin Valley coal mine, in northwest corner of sec. 20 and SE. | sec. 22, T. 20 S., 11. 14 E. 

Prominent medium-grained sandstone bed about 200 feet above contact with concretionary sandstone 

beds mapped as Cretaceous.

4015. High point on Reef Ridge, about 1 mile south of sharp turn in Zapato Creek and 1 mile cast of Sulphur Spring Canyon, in sec. 25, T. 22 S., R. 15 E. Basal conglomerate of Tejon.

4010. Eight miles due north of Coalinga, one-half mile east of Oil Canyon road, and just north of Laval 

grade, near center of SE. J sec. 20, T. 19 S., R. 15 E. Siliceous shale in upper portion of Tejon.

4017. On southwest flank of Reef Ridge, north of McLure Valley, 2J miles south-southeast of El Cerrito 

well, in sec. 27, T. 23 S., 11.17 E. Lower member.

4019. Fifteen miles north of Coalinga, southwest of Domengine's ranch. Sandstone at top of lower 

member. ,

4020. Coal mine, 4£ miles northwest of Coalinga, about 1 mile north of San Joaquin mine, S W. J NE. J 

sec. 22, T. 20 S., R. 14 E. In very gypsiferous variable sand and clay overlying coal seams, 200 to 300 feet 

above base of formation.

4021. About 5 J miles northwest of Coalinga, on point of hills (elevation 1,100 feet) south of mouth of Los 

Gatos Creek, in center of NE. J sec. 15, T. 20 S., it. 14 E. In hard calcareous sandstone bed about 150 feet 

above contact with concretionary sandstone mapped as Cretaceous.

4022. Four miles west-northwest of Coalinga, on top of hill north of road and pne-half mile south of San 

Joaquin Valley coal mine, west of center of SW. J sec. 20, T. 22 S., R. 14 E. Prominent sandstone bed 

about 150 feet above concretionary sandstone mapped as Cretaceous.

4801. Three miles northwest of Coalinga, at San Joaquin Valley coal mine, in NW. J sec. 20, T. 20 S., 

R. 14 E. Lower member.

5013. Eight miles northwest of Coalinga, in white siliceous shale at top of Tejon formation, east of center 

of sec. 25, T. 19 S., R. 14 E.

5014. About 13 miles north of Coalinga, on cast side of sec. 29, T. 18 S., R. 15 E., in dark-colored shalo 

just under Miocene oil sand.
72 COALINGA OIL DISTRICT, CALIFOBNIA.

OTHER SPECIES COLLECTED.

To the above list of species should be added the following, among 

others collected by F. M. Anderson a in the same region:

FORAMINIFERA.

Cyclammina sp. 

Lagena? sp. 

Nodosaria p. 

Polymorphina sp. 

Pulvulina sp. 

Sagrina sp. 

Vagmulina sp.

ANTHOZOA.

Ellipsosmilia granulifera Gabb (4). 

Trochocyathus striatus Gabb + Trochosmilia id. (4).

PELECYPODA.

Gari texta ? Gabb (4). 

Modiola ornata Gabb (3).

GASTEROPODA.

Cancellaria elongata Gabb (1). 

Architectonica hornii Gabb (1). 

Fusus diaboli Gabb (1). 

Fusus martinez Gabb (1, 3). 

Morio tuberculatus Gabb (4). 

Neverita globosa Gabb (1, 3).

BRACHIOPODA.

Terebratella sp. (2).

1. Region southeast of Big Tar Canyon.

2. Conglomerate and coarse sandstone near base of Eocene at San Joaquin coal mine 

and northward to Los Gatos Creek.

3. Sandy beds associated with the carbonaceous strata above 2.

4. North of Los Gatos Creek.

FAUNAL RELATIONS AND AGE.

With the exception of the new Eocene species described by the 

senior author in Bulletin 396, certain species described by J. G. Cooper 

and F. M. Anderson from this region, and a few forms that occur in 

the Martinez or lower Eocene, the fauna of the Eocene of the Coalinga 

district consists of species heretofore known only from Tejon localities.

The new forms discovered by F. M. Anderson and the writers have 

so far escaped observation in other localities, but some of them, at 

least, may eventually be found elsewhere. The species occurring in 

the Coalinga district and also found at the type locality of the Martinez 6 are as follows:

Cardium cooperi Gabb. 

Cylichna costata Gabb. 

Dentalium cooperi Gabb. 

Leda gabbi Conrad. 

Lunatia hornii Gabb.

Morio tuberculatus Gabb. 

Tellina hornii Gabb. 

Turritella pachecoensis Stanton. 

Venericardia planicosta Lamarck 

hornii Gabb).i

(V.

According to Merriam6 Cardium cooperi is common in the Martinez 

and rarer in the Tejon; Cylichna costata is rare in the Martinez and

a Proc. California Acad. Sci., 3d ser., Geology, vol. 2, No. 2,1905, pp. 164-166. 

6 Merriam, J. C., Jour. Geology, vol. 5, 1897, p. 773.
TEJON FORMATION. 73

common in the Tejon; Dentalium cooperi is common in the Chico 

(Cretaceous), Martinez, and Tejon; Leda gabbi is common in both the 

Martinez and Tejon; Lunatia Jiornii is rare in the Martinez and common in the Tejon; the occurrence of Morio tuberculatus is questionable in the Martinez; Tellina Jiornii is common in both the Martinez 

and Tejon; and Venericardia planicosta is common throughout the 

Martinez and Tejon and all through the Eocene for that matter. The 

Turritella pachecoensis from the Coalinga district is much smaller than 

the typical form from the Martinez. Pecten peckhami Gabb extends 

to the Miocene or even higher.

Of a total fauna of 52 recognizable species in the Tejon of the 

Coalinga district 10 are species so far known only from the district, 

1 has heretofore been known only in the Martinez, 8 are found both 

in the Martinez and the Tejon (but all these except one are species 

of which the individuals are as common or commoner in the Tejon 

than in the Martinez), and 33 are known almost exclusively in the 

Tejon. It is obvious, therefore, that the bulk of the Eocene in 

the Coalinga district is of Tejon age, which probably represents a 

part of the middle Eocene. There is also evidence favoring the correlation of the fauna with that of the Jackson formation of Mississippi.

The faunas of all the localities in the Tejon in the Coalinga district, with the exception of those found associated with the carbonaceous beds west of Coalinga, indicate a'marine origin for the 

deposits. The fauna of the carbonaceous beds (locality 4801, etc.) 

indicates brackish water at this locality during a part of the Tejon. 

This agrees with evidence from other parts of the west coast where 

the middle Eocene is characterized by brackish and even fresh 

water deposits, usually containing more or less coal. The brackishwater deposits in the Coalinga district are characterized by such 

species as Barlatia morsei Gabb, Placunanomia inornata Gabb, Ostrea 

aviculiformis Anderson, and Potamides carbonicola Cooper.

The molluscan fauna of the white diatomaceous and foraminiferous 

shale at the top of the Tejon in the Coalinga district consists of 

Pecten interradiatus Gabb, Pecten peckhami Gabb, and Leda gabbi 

Conrad. Leda gabbi is a common Tejon species, while Pecten peckhami is so far known elsewhere only in the Oligocene, Miocene, and 

possibly Pliocene. Pecten interradiatus is known elsewhere only in 

shales occupying a similar stratigraphic position to the shales in 

which it occurs in the Coalinga district. The stratigraphic evidence 

is strongly in favor of the diatomaceous shales being a part of the 

Tejon; the faunal evidence is about equally divided; therefore itseems most logical that the rocks in question be assigned to the Tejon, 

at least until the securing of further and more definite evidence.

Owing to the close resemblance of the shales under discussion to 

the Monterey (lower middle Miocene) shale of other portions of the
74 COALltfGA OIL DISTRICT, CALIFORNIA.

Coast Ranges and to the occurrence in them of the then supposedly 

characteristic Miocene fossil Pecten peckJiami Gabb, the former were 

ascribed to that formation by Watts,0 Eldridge, b and F. M. Anderson. c 

Later/ F. M. Anderson withdrew this correlation, suggesting that 

"the definite assignment of these shales to either the Eocene or the 

Oligocene in the time scale of California geology * * * must be 

reserved for further study and for some future time."

IMPORTANCE WITH RELATION TO PETROLEUM.

The diatomaceous and foraminiferal shale forming the upper member of the Tejon is thought to be the original source of the petroleum 

found in the Tejon and later formations of the Coalinga district. 

This shale is petroliferous practically throughout its extent in the 

district, whereas the purple-shale member of the Chico, which is the 

only oil-bearing zone lower than the Tejon, is present only in the 

very northern part of the district. The post-Eocene beds are petroliferous where associated with the Tejon. Where it is absent they 

are dry. In the northern portion of the district the shale forming 

the upper member of the Tejon is stained with petroleum, but as far 

as known the formation there does not contain any reservoirs of 

oil. The oil has migrated upward and collected in vast quantities 

in the more suitable reservoirs afforded by the Miocene beds. In 

the southern portion of the district the sandstone of the lower half of 

the formation is saturated with oil, in places through its whole thickness. The sand has a strong odor, and when a fresh fracture surface 

is exposed the beds are found to be stained brown throughout. Included layers of shale are stained purple. The wells which are drilled 

through the shale to this sandstone strike oil in it everywhere in small 

amounts. The great thickness of the sandstone through which the 

oil has permeated lessens the- probability of its being found in large 

amounts locally. It is probable that this oil originated in the shale 

above and became absorbed in the sandstone both above and below. 

The occurrence of it in the overlying Miocene beds will be mentioned 

later.

The shale in the upper part of the Tejon contains a large proportion 

of material of organic origin. The calcareous facies is largely composed of foraminiferal remains, and the hard siliceous beds are very 

similar to the altered varieties of diatomaceous shale found in other 

formations in other parts of the State. In places in this district the 

shale is softer and less altered and may be seen to be composed largely

a Bull. California State Min. Bur. No. 3,1894, p. 65; Bull. No. 18,1900, p. 136. 

6 Bull. U. S. Geol. Survey No. 213,1903, p. 307.

e Proc. California Acad. Sci., 3d ser., Geology, vol. 2, No. 2,1905, p. 173. 

d Idem, 4th ser., vol. 3,1908, p. 16.
GENERAL DESCRIPTION OF POST-EOCENE FORMATIONS. 75

of diatom remains. In the opinion of the writers.it is probable that 

these small marine organisms have been the chief source of the oil. 

In other parts of California the origin of the petroleum is ascribed 

to formations of similar peculiar character, although of different age, 

and it is a striking fact that all the conditions point to the diatomaceous or foraminiferal nature of the deposits, rather than to the age or 

other characteristics of the formations, as the determining factor in 

the original occurrence of petroleum.

GENERAL DESCRIPTION OF THE POST-EOCENE FORMATIONS.

INTRODUCTION.

The Miocene, Pliocene, and early Pleistocene are represented in the 

Coalinga district by a series of formations that form a group by themselves distinct from the older formations. The first impression received upon viewing the field is that the later Tertiary beds form one 

continuous succession, and it is therefore natural to take up first a 

brief review of the whole series before passing to the more detailed 

descriptions of the different divisions of it, which on closer study are 

found to be separable from one another.

The periods following the Eocene are here represented by a great 

series of sandstone, shale, and conglomerate beds, all tilted at about 

the same angle, having usually similar characteristics, and presenting 

an appearance of conformity and intergradation. By means, however, of discontinuous fossil faunas, distinguishable lithologic groups, 

the absence in some places of formations or zones.known elsewhere, 

as a result of erosion and the overlapping of later beds, and the appearance of fragments of older formations within younger ones, 

several important breaks may be definitely made out, which prove 

the intervention of periods of time during which land conditions 

existed over wide areas or locally. The important post-Eocene 

formations that represent the epochs of submergence of the land in 

the area now occupied by the Coalinga district are the Vaqueros 

(lower Miocene), the Santa Margarita (?) (upper middle Miocene), 

the Jacalitos (early upper Miocene), the Etchegoin (late upper Miocene), and the Tulare (Pliocene and lower Pleistocene) formations. 

The Tulare formation is probably in large part of different origin 

from the others, but is similar to them in the general features of its 

appearance. These formations are all united into one series in the 

monocline dipping down the east flank of Joaquin Ridge in the 

northern part of the district, and again in the monocline dipping 

away from Reef Ridge in the southern portion, but the character 

of the series is not entirely the same in the two regions.
76 COALINGA OIL DISTRICT, CALIFORNIA. 

DESCRIPTION OF THE SERIES IN THE NORTH.

In the northern part of the district the base of the Miocene-Pliocene 

is formed of coarse and fine oil-impregnated sands unconformably 

overlying the whitish and purplish petroliferous Eocene (Tejon) 

shales, these sands being overlain, by prominent sandstone beds (the 

"reef beds"), a prominent zone of white siliceous shale (the "indicator"), and soft sand up to the base of a zone of bluish-gray and variegated clay, sand, gravel, and serpentine detritus locally known as the 

Big Blue. Up to this point the beds are f ossilif erous, have a thickness 

of about 550 feet, and are mapped as Vaqueros (lower Miocene). The 

Big Blue has a thickness of about 300 feet and is nonf ossilif erous. 

It corresponds in stratigraphic position to the Monterey shale (middle 

Miocene) of regions nearer the coast, but nothing has been discovered 

to indicate that it may belong to that formation. It is overlain by 

a thickness of about 175 feet of sand, sandstone, and conglomerate 

beds full of immense oysters, barnacles (Tamiosoma), scallop shells 

(Pecten), and other fossils. These f ossilif erous beds will be referred to 

as the Tamiosoma zone. They are overlain by 400 to 500 fee't of 

sand and gravel beds up to the base of a very prominent gravel zone 

full of petrified wood. The beds from the base of the Big Blue up 

to this point are mapped as the Santa Margarita (?) formation (upper 

middle Miocene). The gravel zone with fossil wood forms the base 

of .a succession of sand, sandstone, gravel, and clay beds extending 

up to the base of a prominent zone of bluish-gray sand beds having 

near their base a rich fossil bed, the Glycymeris zone. The succession 

of beds up from the base of 'the fossil-wood gravel zone to this point 

has a thickness of about 1,600 feet and is mapped as the Jacalitos 

formation (early upper Miocene). The fossil bed (Glycymeris zone) 

and bluish sands immediately overlying grade upward into sand and 

clay beds, the whole forming a thickness of about 1,700 feet, which 

is mapped as the Etchegoin formation (uppermost Miocene), and this 

finally is overlain by poorly exposed coarse gravel deposits, which 

are mapped as the Tulare formation (Pliocene-lower Pleistocene). 

The total thickness of the succession in the Coalinga field thus outlined is about 4,600 feet, exclusive of the Tulare formation, which 

can not be measured in this portion of the district.

DESCRIPTION OF THE SERIES IN THE SOUTH.

In the southern part of the district the basal-portion of the MiocenePliocene series consists of about 700 to 900 feet of steeply dipping 

hard sandstone and conglomerate beds forming the face of Reef 

Ridge. These overlie, with an important though usually not apparent 

unconformity, the shale of the Tejon (Eocene) and are locally, petroliferous. At the summit they grade into softer beds which are over-
GENERAL DESCRIPTION OF POST-EOCENE FORMATIONS. 77

lain by hard siliceous shale. Up to this shale the beds are fossiliferous and are mapped as the Vaqueros formation. The overlying 

shales are hard and whitish, form a prominent zone varying up to 

1,200 feet in thickness, and are mapped as Santa Margarita (?), 

although only tentatively referred to that formation. These shales 

are overlain by a great succession of beds of sandstone, shale, sand, 

clay, gravel, and conglomerate of many varieties, having a thickness 

as measured in a section south of Big Tar Canyon of about 9,500 feet. 

This succession is divided on the map, on the basis of criteria to be 

discussed later, into three approximately equal divisions corresponding 

to the formations in the north, namely, the Jacalitos (early upper 

Miocene), Etchegoin (uppermost Miocene), and the Tulare (Pliocenelower Pleistocene). The total thickness of the Miocene, Pliocene, 

and lower Pleistocene series measurable in the above-mentioned

single section is over 11,000 feet. 

PREVIOUS CORRELATION.

In his paper entitled "A stratigraphic study in the Mount Diablo 

Range of California/'*1 F. M. Anderson adopted a classification of 

the Tertiary rocks in the hills around about Pleasant Valley, where 

Coalinga is situated, which in the light of more detailed studies has 

required some modification. To avoid confusion, an outline will here 

be given of the changes that it has been found necessary to make'.

The white and brown shales in the Coalinga field that are in the present report mapped and described tentatively as the upper, portion of 

the Tejon (Eocene) were very naturally considered to be "Monterey " 

(middle Miocene) by F. M. Anderson, owing to their resemblance to the 

well-known shales of that formation, and they were so described. 

The lower Miocene beds were considered to be lacking. The series 

of strata unconformably overlying the shales and extending nearly 

up to the fossiliferous beds, here referred to as the GlycAjmeris zone, 

were described by him as a stratigraphic unit under the name "Coalinga beds," and as upper Miocene in age. The thickness of this 

series he gave as varying from 2,180 feet 10 miles north of Coalinga 

to 1,556 feet 10 miles farther north, and to 4,490 feet 3 miles west of 

Coalinga. As will be discussed more fully in connection with the different formations, this series of strata has been found to be divided 

'into several portions separated by unconformities and representing 

different periods of the Miocene. At least two of these portions 

correspond definitely to well-known formations in near-by portions 

of the State. The accompanying diagram will illustrate the classio Proc. California Acad. Sci., 3d ser., Geology, vol. 2,'No. 2, 1905, pp. 174 et seq.
78 COALINGA OIL DISTRICT, CALIFORNIA.

fications of the strata in the hills north of Goalinga adopted in the 

present report and by F. M. Anderson in the paper quoted:

Diagram of the middle Tertiary column north of Coalinga. 

(Not drawn to scale.)

Present report. Paper by F. M. Anderson.

Etchegoin (uppermost Miocene).

 Unconformity 

Jacalitos (upper Miocene).

 Unconformity 

Santa Margarita (?), including Big Blue (possibly 

Monterey) at base (middle Miocene).

 Unconformity 

Vaqueros (lower Miocene).

Etchegoin (Pliocene).

Unconformity

Coalinga (upper Miocene).

Unconformity --

Tejon (upper part) (Eocene).

Unconformity

Monterey (middle Miocene).

Temblor [= Vaqueros] (lower Miocene) absent here, 

but occurring in Kreyenhagen field.

The lower beds of the Miocene series, namely, those associated with 

the "reef beds," are equivalent to those described byF. M. Anderson in 

the Kreyenhagen'field as the " Temblor beds " (lower Miocene), which 

are themselves equivalent to the widespread Vaqueros sandstone 

(lower Miocene) of the California Coast Ranges. This portion of the 

series north of Coalinga contains at several different horizons good 

faunas characteristic of the lower Miocene.

The middle portion of the series is unconformable upon the lower 

portion and contains rich fossil beds which have been referred to as the 

Tamiosoma zone. The fauna of these beds is typical of the Santa 

Margarita (upper middle Miocene) formation, well known in the 

Salinas Valley region. The Big Blue, which occurs below- the Tamiosoma zone and which has been included at the base of the Santa 

Margarita (?) formation in the mapping, may possibly represent in 

part another well-known formation, the Monterey (middle Miocene), 

or may be part of the Vaqueros.

The upper portion of the series makes up an unconformably overlying, for the most part nonfossiliferous formation of upper Miocene 

age, the equivalent of a portion of an important succession of strata 

occurring well developed and with characteristic fauna in the southern 

portion of the Coalinga district, where the name Jacalitos formation 

has been assigned to it in the present report. The "Coalinga beds" 

were stated by F. M. Anderson to be lacking in the southern portion 

of the district. |

The series termed the "Coalinga beds" was characterized by four 

lists of fossil species in the original description. The fossils in three 

of these lists were stated to come from the "reef bed," which has been 

shown to be Vaqueros (lower Miocene) in age. Those in the fourth 

were obtained north of the Coalinga district, from a stratum 400 feet 

above the "reef bed," in the continuation of the beds here mapped
GENERAL DESCRIPTION OF POST-EOCENE FORMATIONS. 79

as Santa Margarita (?). As far as faunal characterization goes the 

" Coalinga beds" are therefore to be correlated with the "Temblor 

beds" described by Anderson that is, with the Vaqueros and with 

the Santa Margarita (?). In view of the fact that the series has been 

found divisible into distinct formations of different ages, for the most 

part equivalent to formations known elsewhere, \the name "Coalinga 

beds" can not be retained. 0

THE McKITTRICK FORMATION SOUTH OF THIS DISTRICT. .

At most localities along the flanks of the Diablo and Temblor ranges 

south of the Coalinga district it has not been found possible to separate thepost-SantaMargarita (?) Tertiary formations, owing to the facts 

that they are imperfectly exposed and that they are unusually poor 

in fossils. These beds are the continuation and at least the partial

equivalent of the succession of beds in the Coalinga district which is

divisible into the three formations Jacalitos, Etchegoin, and Tulare. 

The name McKittrick formation has been applied to these beds along 

the Temblor Range because of their importance as a cartographic 

and (in appearance) stratigraphic unit in and to the north and south 

of the McKittrick oil district. b

To the south of the Coalinga district the McKittrick formation is 

distributed over both sides of the Temblor Range along most of its 

length and forms the whole of the Buena Vista and Elk hills. It is 

particularly important economically, as its basal members are the 

productive beds for the McKittrick, Midway, and Sunset oil fields. 

On the east side of the Temblor Range the formation consists of 

coarse to fine conglomerates and coarse sands near its base, then a 

zone of bluish sandy clay, then medium to coarse sands and sandy 

shales, and at the top a succession of alternating coarse gravel and 

clay beds. The whole formation ranges from 1,300 to possibly 2,500 

feet in thickness. It overlies the Monterey and Santa Margarita (?) 

uncdnformably, and is in turn unconformably overlain by lateQuater-

"Sinco the preparation of this bulletin there has appeared a paper by Frank M. Anderson entitled "A 

further stratigraphic study in the Mount Diablo Range of California" (Proc. California Acad. Sci., 4th ser., 

vol. 3, Oct. 31,1908, pp. 1-40). In this paper the description of the section given in his former paper is considerably revised. The white shales south and east of Oil City are recognized to be Eocene or Oligocene 

instead of Monterey (middle Miocene), and the unconformably overlying formation, in which the "reef 

beds " occur, to be lower Miocene. The application of the term "Coalinga beds " is changed so as to leave out 

the lower Miocene, which was the most typical portion in the original description, and the Big Blue, which 

is recognized as possibly representing the Monterey. Two faunal lists characterizing the "Coalinga beds" 

arc given for the type locality north of Coalinga, the first being of the fossils of the Tamiosoma, zone, which arc 

typical of the previously named Santa Margarita formation, and the second being the same list of fossils 

given in the former paper as from 400 feet above the "reef bed." The thickness of the revised "Coalinga 

beds" is given as from 500 to 800 feet between Coalinga and Qantua Creek, which is 20 miles or so north. 

From this it appears that the intention is to restrict-the name to practically the same beds north of 

Coalinga which are mapped in the present report as Santa Margarita (?) exclusive of the Big Blue. 

South of Waltham Creek these beds are correlated with a portion of the terrane mapped as the Jacalitos 

formation in the present report. The thicknoss of the "Coalinga beds" is stated to be "from 1,000 to 1,500 

feet in the field between Waltham Creek and Tulare Lake."

b Arnold, Ralph, and Johnson, Harry R., Preliminary report on the McKittrick-Sunset oil region, 

California: Bull. U. S. Geol. Survey No. 406,1910.
80 COALINGA OIL DISTRICT, CALIFORNIA.

nary sand, gravel, and alluvial deposits. Evidence of an unconformity within, the formation was obtained at one or two points.

VAQUEROS SANDSTONE (LOWER MIOCENE).

GENERAL DESCRIPTION.

The unconformity at the top of the Tejon (Eocene) marks an important lapse of time before the beginning of the Miocene period. In the 

early Miocene a sedimentary formation was deposited in the Coalinga 

district that is the correlative of the formation known as the Vaqueros 

in the region nearer the coast.

The Vaqueros in the area under discussion forms an elongated belt 

east of the belt of Tejon in the hills bordering the great valley. It 

has a thickness ranging from about 550 feet in the Coalinga field to 

900 feet in the Kreyenhagen field of hard and soft sandstone, shale, 

and conglomerate, and may be easily distinguished from all the other 

formations by the protruding tendency of the hard sandstone beds, 

the "reef beds," in its central portion. These beds outcrop prominently in the northern portion of the district, as shown in Plate VII, 

A, and again in the southern portion assume such prominence as to 

dominate the landscape on the bold face of the long ridge that is 

named in the present report Reef Ridge. They are much more resistant to erosion than the soft associated beds, and dipping toward the 

valley on the northeast at an angle varying from 50° to 80° they form 

the scarp and double row of pinnacles of Reef Ridge fronting the foothills on that side, as shown in Plate VIII.

An important distinguishing feature of the Vaqueros is that the 

beds at its base are the chief oil sands of the Coalinga district. (See 

PI. V, B.} In many places they are saturated and discolored with 

petroleum. They rest upon the eroded surface of the shale of the

Tejon throughout most of their extent,'but overlap in the Alcalde and 

Jacalitos hills upon the Knoxville-Chico (Cretaceous) rocks, thus 

hiding the Tejon from view. Where such overlapping occurs, the 

basal beds lose their petroliferous character at a distance from the 

Tejon.

DISTRIBUTION AND LOCAL CHARACTER.

GENERAL STATEMENT.

There are three different areas along the belt of outcropping 

Vaqueros beds which deserve description separately owing to the 

diversity of character assumed by the formation in them. One of 

these is in the oil field north of Coalinga, a second extends from a 

point in the Alcalde Hills west of Coalinga to Waltham Creek, and the 

third is along Reef Ridge. The first two areas are separate. The 

second and third areas are'shown on the map as discontinuous, but
U. S. GEOLOGICAL SURVEY

A. "REEF BEDS" OF VAQUEROS SANDSTONE OVERLYING OVERTURNED SHALES OF 

THE TEJON FORMATION.

Looking northwest across foothills 8 miles north of Coalin^a. Taken from hill shown in middle of 

Plate XIV. Photograph by Ralph Arnold.

 00

(0

Vaqueros sandstone with gravel,sand clayand 

shale ; Basal beds form oil zone D

B. DIAGRAM OF PLATE VII, A,

Overturned shales 

of theTejon
U. S. GEOLOGICAL SURVEY 

"REEF BEDS" OF VAQUEROS SANDSTONE FORMING SCARP 

Looking south across upper portion of Zapato Creek. Photograph 
VAQUEROS SANDSTONE. 81

it' is possible that a narrow belt of Vaqueros is exposed south of 

Waltham Creek, and that this joins the belt on Reef Ridge in the 

territory southwest of that shown on the map.

VAQUEROS NORTH OF PLEASANT VALLEY.

In the hills north of Coalinga the formation includes all the beds 

overlying the Tejon at least as far up in the series as the base of 

the zone locally well known as the Big Blue, and possibly to the 

summit of this zone, which is at the base of the Tamiosoma zone. 

The Big Blue is not known to be fossiliferous and presents there-, 

fore no definite basis for correlating it, but it is mapped for the 

present as a portion of the overlying formation (the Santa Margarita?) and the summit of the Vaqueros is placed at its base. The 

term. Vaqueros as here used is thereby restricted to those beds which 

are known by their fossils as belonging to that formation. These

beds have a thickness of about 550 feet.

The lowest bed of the formation is coarse, irregular, pebbly sand 

truncating the eroded edges of the shale of the Tejon formation. A 

typical exposure of the basal zone is shown in Plate V, B. It is 

followed above by roughly bedded, hard and soft, both coarse and 

fine sandstone, sandy shale, and pure shale, with some thin white 

diatomaceous layers. These basal beds for 100 or 200 feet up 

are thoroughly impregnated with oil and have a dark-brown color 

due to staining, a strong odor, and a curious mode of fracturing characteristic of rock that is filled with bitumen. About 225 

feet above the base is a hard zone varying from 5 to .15 feet 

in thickness, made up of several calcareous sandstone layers and 

a rough mixture of ingredients of different kinds and textures. 

This zone of hard sandstone forms a prominent outcrop over the 

summit and down the sides of the hill shown in Plate VII, A, just 

east of the road leading up Oil Canyon, appearing from a distance 

like a portion of the periphery of a huge wheel. Owing to the tendency of this bed to jut out over the surface of the hills, it was referred 

to as the "reef bed" by F. M. Anderson in his paper above quoted, 

and the name is here retained for convenience of reference, but 

changed to the plural to include the various other hard beds just 

above and below it.

Similar hard and soft sandstone beds continue to about 425 feet 

above the base of the formation, where a bed some 10 to 20 feet 

thick of compact white, diatomaceous, and foraminiferal shale is 

sharply interbedded. This bed is prominent and so sharply marked 

off from the associated gray sand that it may be easily traced. It 

has been referred to throughout the field work as .the ''indicator," 

and the name was found so convenient that it may as well be used 

88170 Bull. 398 10 6
82 COALINGA OIL DISTRICT, CALIFORNIA,

here. A good exposure of it is shown as a white outcrop running 

up the ridge to the right of the center in Plate XIV. The bed is 

continuous, always in the same relative position, from Oil Canyon 

to the northern edge of the area shown on the map, beyond which 

no attempt was made to trace it. Southwest of Oil Canyon it is 

continuous for a mile or two at least. It preserves its strong individuality throughout in spite of the fact that it changes in character 

locally from a soft though compact earthy deposit, both massively 

bedded and finely laminated, as on the east side of Oil Canyon near 

the point shown in Plate XIV, to hard, thinly bedded white porcelaneous or flinty shale and yellowish calcareous shale, as south of 

the Laval grade on the hill (elevation 2,024 feet) 8$ miles north 

of Coalinga in the western half of sec. 21. This bed, -where not 

greatly indurated, may be seen with a lens to be £ull of diatom 

remains. It 'is strikingly similar to the siliceous shale characteristic 

of the upper Tejon, already described, and of the Santa Margarita(?) formation of Reef Ridge, to be described later. An analysis 

of a sample of the soft white variety from Oil Canyon made by 

R. C. Wells, of the United States Geological Survey, showed it to 

contain 48 per cent of silica.

Above the "indicator" bed soft gray and brown sandstone in 

thin layers makes up a variable zone about 125 feet thick. This 

sandstone has been found to contain typical Vaqueros (lower Miocene) fossils, and is the uppermost stratum in which they are found. 

In the central part of the Eastside field it is' overlain by soft, fine 

grayish-white sand that looks bluish from a distance and is well 

known to the drillers as the Big Blue. Farther north the highest 

fossiliferous beds of the Vaqueros are overlain by coarse detrital 

deposits marking the same zone as the Big Blue. The line for the

top of the Vaqueros formation is drawn at the base of the zone, 

which probably represents an important unconformity.

Southwest of Oil Canyon the Vaqueros beds become much thinner, 

and within about 2 miles they lose their prominence. In the hills 

for 2 miles north of the head of Pleasant Valley the beds are largely 

hidden by recent deposits of soil, alluvium, and gravel, but it is 

probable that a small thickness of beds, representing a part of the 

Vaqueros, is continuous. Their presence within a mile and a half 

north of Los Gatos Creek is doubtfully indicated by certain fossils 

that have been found (locality 4637).

VAQUEROS IN THE ALCALDE HILLS.

In the hills west of Coalinga the Vaqueros is absent north of the 

San Joaquin Valley coal mine, with the possible exception of a thin 

discontinuous zone locally exposed beneath the Santa Margarita (?)
BULLETIN 398 PLATE IX

A. VIEW LOOKING SOUTH DOWN AVENAL CREEK.

Showing Avenal Ridge, formed of Cretaceous beds, on the right and the hills of white Miocene shale on 

the left. Photograph by Ralph Arnold.

& 

Jl. BED OF SAND DOLLARS IN PEBBLY SAND OF ETCHEGOIN FORMATION, 

i Kreyenhagen Hills, between Garza Creek and Big Tar Canyon. Photograph by Ralph Arnold.
VAQUEROS SANDSTONE. 83

and Jacalitos formations. South of the coal mine incoherent fossiliferous beds of the Vaqueros formation overlap upon the Tejon and 

Chico (Upper Cretaceous) beds. They have a thickness of about 

500 feet, as they have in the Eastside field. The beds are extremely 

variable and consist for the most part of incoherent yellowish and 

gray sand, both coarse and -fine.. The sand is roughly bedded and 

has partings and lenses of hard sandstone and of gravel. Fossils 

are abundant in it, but they are poor and not certain as indicators. 

The section in figure 8 shows some of the features of the formation 

in this portion of the district. Westward a capping of low-dipping 

beds extends over the ridges formed of steeply dipping beds of the 

Knoxville-Chico. This capping is for the most part only slightly 

indurated sand, gravel, and clay in irregular deposits and variable 

colors, such as green, blue, red, etc. A few marine fossils were 

obtained that point to a lower Miocene age, though they do not prove 

it. Fossil wood occurs in certain places in these beds, notably on 

the summit of Juniper Ridge, a few miles north of Alcalde Canyon, 

and it is thought that they may be in part nonmarine.

VAQUEROS IN THE JACALITOS HILLS.

Between Waltham Creek and the north end of Reef Ridge the Vaqueros has not been recognized, but it may form a belt around the 

southeastern side of Curry Mountain, through the area tentatively 

mapped as covered by the Jacalitos formation, and thence continue 

southward beyond the limits of the mapped area, to join the belt on 

Reef Ridge.

VAQUEROS ON REEF RIDGE.

The Vaqueros sandstone overlies the shale of the Tejon on Reef 

Ridge and forms the steep face of the ridge. The beds show a thickening of the deposits of this period southward from, the region around 

Pleasant Valley. They also have undergone a greater amount of 

induration and form a more conspicuous part of the landscape than 

the contemporary beds farther north. Their relation to the underlying shale of the Tejon is one of unconformity, although no wide 

disparity in dip has been observed in the strata of the two formations. 

There is even an apparent gradation from the shale below to the 

sandstone above in some places and it is difficult to place the exact 

contact between the two formations. This difficulty is largely due 

to the lack of continuous exposures near the contact.

The Vaqueros sandstone is subject to considerable variation from, 

place to place, as will be shown in the accompanying tabulated sections. The formation may in general be divided into three zones, one 

of comparatively soft beds of sandstone and shaly sandstone at the 

base, comprising- about one-fourth of the total thickness; a second
84 COALINGA OIL DISTRICT, CALIFORNIA.

of hard, fossiliferous beds of sandstone with some conglomerate, 

making up about half of the formation and producing the prominent 

outcrops of Reef Ridge; and a third zone similar in thickness and 

character to the first and grading into soft, fine-grained beds that are 

poorly exposed and lead the observer to think there is a transition to 

the shales above, which are described, as Santa Margarita (?). Such, a 

transition is not supposable if the correlations that have been made 

are correct. The third zone is much thicker on Canoas Creek than 

elsewhere and there makes up half of the formation. The Vaqueros 

as a whole is thicker in the southeastern than in the northwestern 

half of Reef Ridge. The thickest section observed was on Canoas 

Creek, where the formation comprises a thickness of 900 feet. The 

middle zone is marked by three principal horizons of hard, fossiliferous sandstone and. conglomerate beds that stand out in strong relief. 

The lowest of these "reef beds" and the middle one are about 150 to 

200 feet apart, and the middle and uppermost beds 100 feet apart 

on the average. They vary in relative prominence from place to place, 

and the exact horizon at which the induration is most pronounced 

is variable.

The following section, together with figure 3, gives an idea of the 

character of the Vaqueros formation as it occurs typically exposed 

along Reef Ridge:

Section of Vaqueros sandstone in Canoas Canyon.

FeetSoft, fine sandstone with large oil seepages; "button beds" at base containing

Scutella, etc. (locality 4772); overlain by siliceous shale of Santa Margarita (?). 180 

Hard and soft, gray and brown stained sandstone with large oil seepages in upper

half. .................................................................... 300

Massive sandstone beds with thick, very prominent, hard beds at top and at base,

the "reef beds;" Pecten andersoni bed at base (locality 4771)................ 100

Sandstone with very prominent hard bed,, the Turritella ocoyana bed, at base

(locality 4770)............................................................ 200

Fairly hard, thin-bedded sandstone underlain by shale of the Tejon formation.. 120

900

FOSSILS AND AGE.

LIST OF FOSSILS.

Throughout the Coaluiga district the Vaqueros sandstone is at 

one horizon or another generally fossiliferous and yields a fauna of 

many species, sometimes in a fairly good state of preservation. The 

following species have been found by the writers in or immediately 

adjacent to the Coalinga district:
VAQUEROS SANDSTONE. 85

Vaqueros (lower Miocene) fossils from the Coalinga district, California.

Name.

ECHINODERMATA.

PELECYPODA.

Pecten andersoni Arnold. . .........................

Pecten miguelensis Arnold .........................

Septifer coalingensis Arnold ........................

Zirphaea dentata Gabb ............................

GASTEROPODA.

Agasoma kernianum Cooper .......................

Ficus pyriformis Gabb. . ...........................

Neventa callosa Gabb. . ............................

Trochita filosa Gabb ...............................

Trochita sp. indet. .................................

Trophon (Forreria) bartoni Arnold. . ...............

Trophon f Forreria) gabbianum F. M. Anderson. . . .

Trophon (Forreria) gabbianum F. M. Anderson var. 

cancelfarioides Arnold ...........................

Xylotrya sp. i .....................................

CIRBIPEDIA.

Balanus sp. ............: .....:.....................

CRUSTACEA.

Branchiolambrus altus Rathbun. ..................

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4024. Turrite.lla bed, or lower one of "reef beds," in Garza Creek gorge through Reef Ridge; southwest 

corner of the SB. J sec. 3, T. 23 S., R. 16 E. 

4625. Sulphur Spring Canyon, in " reef beds;" sec. 23, T. 22 S., R. 15 E.

4627. The " reef bed " just west of Big Tar Canyon; in north part of sec. 18, T. 23 S., R. 16 E.

4628. Oil sand series, in west fork of canyon west of well 3 miles southwest of Coalinga, sec. 12, T. 21 

S.,R. 14 E.

4620. Anticline Canyon about 3 miles southwest of Coalinga, in roughly bedded gypsiferous sand overlying fossiliferous Chico; in center of sec. 2, T. 21 S., R. 14 E.

4631. Tunitella bed on east Hank of high hill northeast of Oil City, in the SE. J NE. i sec. 16, T. 19 S., 

R. 15 E.

4633. Tunitella bed just about 11 miles north-northeast of Coalinga, below the Big Blue, on ridge in sec. 

10, T. 19 S., R. 15 E.

4634. Hill south of well sec. 12, T. 21 S., R. 14 E., about 3 miles southwest of Coalinga.

4635. Bed just below the Big Blue,H- miles northeast of Oil City, near the SE. J SE. J sec. 16, T. 19 S., 

R. 15 E. ,

4637. Six miles northwest of Coalinga, about 500 feet south of contact of Tejon and Miocene, in center of 

NE. i sec. 2, T. 20 S., R. 14 E.

4655. About 3J miles due west of Coalinga, from prominent sandstone bed about 100 feet stratigraphically 

above contact of concretionary sandstone (Chico) beds with Vaqueros.

4667. The " reef bed " on Reef Ridge, about 1J miles east of Jasper Canyon, one-half mile west of 2,700-foot 

hill 5J miles south-southwest of Alcalde; 125 feet above Cretaceous; in east-central part of sec. 18. T. 22 S.. 

R. 15 E. .
86 COALINGA OIL DISTRICT, CALIFORNIA.

Vaqueros (lower Miocene) fossils from the Coalinga district, California -Continued.

Name.

ECHINODEBMATA..

PELECYPODA.

GASTEROPODA.

Neverita callosa Gabb. .............................

Trophon (Forreria) bartoni Arnold .................

Trophon (Forreria) gabbianum F. M. Andersen . . .

Trophon (Forreria) gabbianum F. M. Anderson

CIRRIPED1A.

CRUSTACEA.

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4764. Stone Canyon coal mine, Monl;erey County, Cal., 40 feet stratigraphical'y above the coal.

4770. Turrilella ocoyana bed in Canoas Canyon, 1J miles southwest of Hugo Kreyenhagen's, NE. J SE. J 

sec. 32, T. 22 S., R. 16 E.

4771. Pecten andersoni bed in Canoas Canyon, 200 feet stratigraphically above 4770.

4772. Smtdla, merriami bed ("button bed") in Canoas Canyon, 600 feet stratigraphically above 4770.

4773. About Similes north of Coalinga, on Laval grade; " oyster bed "of variable sand, just above oil sand 

at base of Vaqueros.

4774. About 8£ miles north of Coalinga, on hill just east of Laval grade; " button bed" about 100 feet 

stratigraphically above 4773; NW. } sec. 21, T. 19 S., R. 15 E.

4775. Garza Creek gorge in Reef Ridge, hard sandstone "button bed " 225 feet stratigraphically above 4624; 

southeast corner of sec. 3, T. 23 S., R. 16 E.

4777. Jasper Canyon through Reef Ridge, 1J miles southwest of fork of Jacalitos Creek, in hard sandstone 

and conglomerate '' reef beds."

4803. About 8£ miles north of Coalinga, " button bed" 200± feet above Eocene unconformity on Laval 

grade; SW. \ sec. 21, T. 19 S., R. 15 E. (Practically the same as 4774.)

4859. Wagon Wheel Mountain, Devils Den district, Kern County, Cal., dark gypsum-bearing shale 50 

feet stratigraphically below " reef bed " or " button bed;" NW. \ sec. 36, T. 25 S., R. 18 E.

4860. Same locality as 4859; in hard sandstone " reef bed" or "button bed."

4861. Devils Den district, Kern County, Cal., " reef beds" one-fourth mile south and southeast of Barton's cabin, which is in the NW. J sec. 23, T. 25 S., R. 18 E.
VAQUEROS SANDSTONE. 87

OTHER SPECIES COLLECTED.

To the list of fossils given above should be added the following 

species, among others, collected by F. M. Anderson a from the 

Vaqueros in the Coalinga district: Agasoma gravida Gabb, Crepidula 

prxrupta Conrad.

KAUNAL 2ONES.

Three distinct fossiliferous zones are recognizable in the Vaqueros 

section north of Coalinga. The lower one is but a short distance 

above the base of the formation and is represented solely by Ostrea 

titan Conrad (loc. 4773). The middle zone, that of the "reef beds," 

is about 225 feet above the base and is characterized by Pecten 

andersoni Arnold, Area osmonti Dall, and Scutella merriami Anderson 

(loc. 4774 and 4803). The upper zone, which lies at the top of the 

Vaqueros and just below the Big Blue sandy shale, is characterized 

by a unique fauna, in which occur such forms as Agasoma SdntdCTUzana Arnold, Cancellaria vetusta Gabb, Turritella ocoyana Conrad, and 

several other species. The fauna at locality 4631 is characteristic 

of the last zone.

FAUNAL RELATldNS AND AGE.

In the Coalinga district the correlation of the sandstone formation, 

of which the "reef beds" are a part, with the Vaqueros formation 

of the outer Coast Ranges is based upon the large number of species 

common to the two. At one point in particular on the northeastern 

flank of the Temblor Range, near Antelope Valley, in sec. 36, T. 26 S., 

R. 17 E., a few miles south of the south line of the region under discussion, the "reef beds" contain a typical Vaqueros fauna with 

such forms as Pecten magnolia Conrad, Turritella inezana Conrad, 

Pecten bowersi Arnold, and many other typical Vaqueros species. 

The region from which this fauna comes is believed by the writers to 

mark an old lower Miocene strait joining the San. Joaquin lower 

Miocene sea with the lower Miocene sea which once covered much of 

the territory now occupied by the outer Coast Ranges.

The lower Miocene (Vaqueros) formation in the Kreyenhagen 

field was described under the name "Temblor beds" (lower Miocene) 

by F. M. Anderson, b from its characteristic occurrence farther south 

along the border of the Great Valley near the Temblor ranch. Owing 

to the possibility of correlating 0 it with the lower Miocene in the 

Coast Ranges to the west the name Vaqueros, previously adopted in 

the literature for the beds of that age, is here used.

The assignment of a lower Miocene age to the Vaqueros sandstone 

is based upon the general similarity of certain members of its fauna

a Proc. California Acad.'Sci., 3d ser., Geology, vol. 2, No. 2,1905, pp. 171-172. 

6 Idem, p. 170.

c In a later paper (Proc. California Acad. Sci., 4th ser., vol. 3, 1908, p. 39) F. M. Anderson recognizes the 

correlation of his "Temblor beds" of the San Joaquin Valley with the Vaqueros of the outer Coast Ranges.
8.8 COALINGA OIL DISTRICT, CALIFORNIA.

to species in the lower Miocene of the Atlantic States and upon its 

relative position in the geologic column of the Pacific coast. This correlation, first made by Conrad, has, so far as the writers are aware, 

never been questioned.

IMPORTANCE WITH RELATION TO PETROLEUM.

The Vaqueros beds constitute the principal reservoir for the 

petroleum in the Coalinga district. The oil enters the formation 

from the shales of the Tejon formation below and collects most 

abundantly in certain favorable zones within the formation, chiefly 

at its base, although permeating locally the whole formation in 

lesser amounts. The summit of the formation, as mapped, being 

overlain by the Big Blue, north of Coalinga, it is coincident with the 

top of the productive zone in the Eastside field. Similarly it is 

believed that the productive zone in the Kreyenhagen field does not 

reach higher than the Vaqueros, the formation being there overlain 

by the impervious shales of the Santa Margarita (?) formation. The 

relation of the formation to the occurrence of the petroleum is discussed more fully in the description of the developed territory.

SANTA MARGARITA (?) FORMATION (UPPER MIDDLE MIOCENE). 

GENERAL DESCRIPTION.

A zone of beds full of fossil oysters and barnacles of very large size 

runs through the midst of the developed oil territory north of 

Coalinga, and is well known by those familiar with the field. (See 

PI. XII, B.) Its fossils show it to belong in the same portion of the 

geologic column as the formation in the drainage basin of Salinas 

River, farther toward the coast, that has been named the Santa 

Margarita by H. W. Fairbanks.a This formation belongs in the 

upper part of the middle Miocene. No fossils have been found in

the beds immediately below or above the Tamiosoma zone, as the 

tossil beds referred to may be termed from the typical and restricted 

occurrence in them of the large barnacle of that genus. But the 

beds below and above, for a thickness of several hundred feet, are for 

'the present mapped in the same formation with the fossil beds because 

closely associated with them and because affording no sufficient 

basis for correlation with any other formation.

The basal portion of the formation so mapped is the zone known 

to the drillers as the Big Blue, the probable unconformaole relation of 

which to the underlying Vaqueros (lower Miocene) has been pointed 

out (p. 82). The possible Monterey (middle Miocene) age of the Big 

Blue has also been mentioned (p. 76). This zone in some portions of 

its extent presents a very striking lithologic contrast to the Tamiosoma zone, which fact, coupled with the fact that it is overlapped by

a San Luis folio (No. 101), Geol. Atlas U. S., U. S. Geol. Survey, 1904.
SANTA MARGARITA (?) FORMATION. 89

the Tamiosoma zone on the west side of Pleasant Valley, indicates 

that it is a distinct unit. Mapping it alone, however, would have led 

to too great complexity. If it did originate in Monterey time it can 

at most represent but a brief fraction of that period.

In the Kreyenhagcn field the portion of the series between the 

Vaqueros (lower Miocene) and Jacalitos (upper Miocene), corresponding to the portion occupied by the Santa Margarita (?) farther north, 

is made up of nonfossiliferous, hard, largely white siliceous shales, 

and it can not be stated definitely whether or not they are a continuation of the beds to the north. This shale is similar in lithologic character, mode of occurrence, and stratigraphic position to shale on the 

southwest side of Waltham Valley toward the head of Jacalitos 

Creek, a few miles west of the area of the map, and is believed to be a 

continuation of it. In that region the shale zone is underlain by 

sandstone beds containing fossils typical of the Santa Margarita, as 

listed under, fossil localities 4805, 4841, and 4842. A similar shale 

zone is present in a similar stratigraphic position over the typical 

fossiliferous sandstone beds of the Santa Margarita on the opposite 

side of the Diablo Range on the slope draining to Salinas River. The 

siliceous shale of Reef Ridge and McLure Valley is therefore tentatively correlated with the Santa Margarita. Inasmuch as the fossiliferous Santa Margarita (?) beds in the northern part of the district 

and those underlying the shale zone in Waltham Valley may belong 

to the same horizon in the formation, it is possible that the shale on 

Reef Ridge is of later age than the Tamiosoma zone in the northern 

part of the district. The period of geologic time between the Vaqueros (lower Miocene) and Jacalitos (upper Miocene) is thought to 

be represented only in its later part by the Tamiosoma zone and 

associated beds of the Coalinga field and the siliceous shale along 

Reef Ridge and McLure Valley, the Monterey formation (early middle Miocene) of the region nearer the coast being wholly or at least 

in large part lacking.

DISTRIBUTION AND LOCAL CHARACTER.

SANTA MARGARITA (?) IN THE COALINGA FIELD.

The basal part of the formation mapped as the Santa Margarita (?) 

formation is the zone known to the drillers as the Big Blue. This 

consists in the central part of the Eastside field of about 300 feet of 

light-gray fine sand and clay that appear to have a light-bluish tinge, 

especially when moistened. Farther north other materials enter 

into this portion of the series, causing it to be one of the most varied 

zones in the region. No fossils have been discovered in it, and its 

peculiar features show that it was formed under unusual conditions. 

(See geologic history, p. 175.) It is recognized in the oil wells as a 

zone of sticky and frequently tough sand and clay immediately over-
90 COALINGA OIL DISTRICT, CALIFORNIA.

lying the oil sands. Toward the northern edge of the area mapped 

it becomes coarser and is largely made up of fine-grained, coarsegrained, and bowlder beds composed of serpentine fragments, having 

evidently been derived from an area of serpentine that was in close 

proximity. Some of these serpentinous beds are extremely hard 

and they form prominent buttes colored by the decaying serpentine 

in a variety of shades of light blue, green, brown, and dark red. A 

typical row of these buttes is shown in Plate X. This zone of beds 

continues far northwest of the mapped area as a prominent feature 

of the hills.

The Big Blue is overlain by the Tamiosoma zone, which comprises 

a thickness of about 175 feet of fossiliferous, fine, medium-grained, 

and coarse, usually gray sand and minor amounts of conglomerate. 

This in turn is overlain by 400 to 500 feet of alternating beds of fine 

sand, sandy clay, coarser sand, and gravel up to the base of the 

prominent and thick gravel zone considered as marking the base of 

the Jacalitos. These upper beds are without fossils as far as examined and have little to characterize them. The succession of upperbeds of the Santa Margarita (?) formation and the lower Jacalitos 

beds is shown in Plate XVII.

Toward the southwest the SiSnta Margarita (?) formation disappears east of Oil Canyon, being overlapped by the Jacalitos. It is 

not known just where the overlap is, because the beds are poorly 

exposed and have no distinguishing characters there. Beds of the 

Tamiosoma zone underlie Pleasant Valley toward its head, as shown 

by fossils obtained at depth in wells near the course of Los Gatos 

Creek. On the west side of Pleasant Valley a remnant of the Tamiosoma zone appears, resting directly and with pronounced angular 

unconformity upon the Tejon (Eocene) at the San Joaquin Valley coal 

mine. The traceable area of it is not large enough to allow its separation from the later beds on the map. This is the southernmost point 

at which the fossils of this zone have been found within the district, 

and south of it the Tamiosoma zone is either absent or hidden by the 

overlapping beds of later age, which are mapped with the Jacalitos formation. There is present, however, beneath the fossiliferous Jacalitos 

beds, between the coal mine and Waltham Creek, a zone of bluish 

and grayish clay, about 250 feet thick, mapped with the Vaqueros of 

that area, that may possibly represent the same horizon as the Big 

Blue in the Eastside field, though this is doubtful.

SANTA MARGARITA (?) IN THE KREYENHAGEN FIELD.

The Vaqueros sandstone all along Reef Ridge and the Cretaceous 

in the Pyramid Hills and around McLure Valley is overlain by a 

formation of white, purplish, and brownish siliceous and argillaceous 

shale, having a thickness varying between 50 and 1,200 feet. The
U. S. GEOLOGICAL SURVEY 

CHARACTERISTIC BLUFFS, WITH STRIKE FACE AND DIP SLOPE, FORMED BY VARICOLORED M

Looking northeast at outcrops of Big Blue, 11 miles northeast of Coalinga. Note local fau
SANTA MAEGAEITA (?) FORMATION". 91

thin, sharp beds of shale dip away from .Reef Ridge on its northeast 

flank, and their upturned edges are exposed in a narrow belt which 

follows the face of the ridge. This belt is likewise a topographic feature, owing to the resistance of the beds, which produce a line of 

shoulders or knobs on the small lateral ridges descending toward the 

foothills. The zone occupied by these shales'is well shown in the 

foreground on the right and all along in front of Reef Ridge to the 

left in Plate VIII. Southeast of Little Tar Canyon the ridge of the 

Pyramid Hills, which is entirely composed of the shale, is a still more 

marked expression of this topographic influence, which is likewise 

characteristic of the formation elsewhere, as, for instance, along the 

Tent Hills west of McLure Valley, as shown in Plate XI, A; in the 

peculiar curving line of knolls that circles around the base of the 

mountain mass at the head of McLure Valley on the northwest; and 

also in the region of Antelope Valley, south of the area of the map,

and in the Waltham Valley, west of it. The features described make 

this shale formation easily recognizable as a lithologic unit with 

strong individuality, and -in the Coalinga district distinguish its main 

portion markedly from the. Vaqueros (lower Miocene) sandstone below and the soft sandstone beds of the Jacalitos (upper Miocene) 

above. This shale formation is tentatively correlated with the 

Santa Margarita. It may be a deep-water equivalent of the coarser 

sediments in the Coalinga field, which at the north end of the area 

mapped are of a strikingly littoral nature, or it may be of different age.

Lithologically this formation has strong affinities with the wellknown Monterey (middle Miocene) shale, which is widely distributed 

in the Coast Ranges farther west, and its stratigraphic position 

above lower Miocene and below upper Miocene in this district corresponds to that of the Monterey shale elsewhere. But no proof is 

known of the contemporaneity of the two formations, whereas the 

fossil evidence already discussed indicates a lesser age. The shale 

is likewise very similar to the shale in the upper portion of the Tejon 

north of Coalinga. This mutual similarity has led previous observers 

to class the two together and to correlate both with the Monterey.

Along the greater portion of Reef Ridge no unconformity at the 

base of the shale is apparent, all the formations being similar in dip. 

But an unconformity is indicated by the fact that the shale overlaps upon the Vaqueros and Tejon at the southeast end of the ridge 

and that in the region of McLure Valley it lies directly upon the Cretaceous beds, the Vaqueros and Tejon having either never been deposited 

or else been worn away. As regards the relation of the shale to the 

overlying formation (the Jacalitos, upper Miocene), it may be said that 

no definite line of separation has been found and that in appearance 

a conformable gradation exists along Reef Ridge, although the pinching out of the white shale and finally the overlap of the Jacalitos 

beds directly upon the Vaqueros farther to the north indicate that
92 COALINGA OIL DISTRICT, CALIFORNIA.

an unconformity exists. The shale is lithologically distinct from the 

greater part of the Jacalitos formation, but there is a nonfossiliferous 

transitional zone of alternating sandstone and shale beds having a 

thickness of several hundred feet, which may belong to either formation. This has been tentatively included with the Jacalitos in the 

mapping, the beds to which the name Santa Margarita (?) formation 

is applied being restricted for the present to the underlying shale. 

Near the southeast end of Reef Ridge and along the ridge of the 

Pyramid Hills northeast of Dudley the shale formation has a thickness of 1,050 to 1,200 feet. It is divided into two main portions, 

the lower of which consists of harder, more siliceous, and more 

thinly laminated purple and white shale and the upper of softer, more 

argillaceous brownish shale. The lower portion is the more conspicuous, constant, and typical; the upper is not so well exposed, is 

more variable in character and is not definitely separable from the 

soft sandstone and shale of the formation overlying. The following 

section is typical of the formation along the face of Reef Ridge at its 

southeast end, the different zones noted not being sharply separated 

from each other:

Section of Santa Margarita (?) formation 3% miles southeast of Big Tar Canyon.

Feet.

Soft brownish clay shale, poorly exposed, grading above into the fine sandy 

shale at the base of the Jacalitos formation and below into bluish-purple 

siliceous shale with occasional hard, more siliceous layers. ................... 400

Hard, siliceous, porcelaneous, thinly bedded, lavender-colored but whiteweathering shale, with angular and conchoidal fracture into elongated, 

sharp-edged pieces, and with prominent iron stain throughout along joints, 

interbedded with occasional soft laminse....'............................... 250

Fairly hard, purplish, siliceous and argillaceous shale, finely fractured into 

needle-like fragments with yellow calcareous concretionary lenses and interbedded porcelaneous layers; overlies the Vaqueros.......................... 400

1,050

The two lower of these three zones differ largely in the proportion 

of hard beds that they contain, and, as this proportion varies from 

place to place, they do not form continuous belts distinct from each 

other. Together they make up the lower portion of the formation 

according to the division above referred to. The siliceous shale of 

the lower portion varies in amount of induration from a dull opaque 

rock that maybe scratched with the finger nail to a sub vitreous flinty 

variety that will not be scratched by a knife. It resembles very 

strongly the altered varieties of the Monterey shale (middle Miocene), 

that occurs nearer the Pacific coast, and of the shale of the Tejon 

formation and "indicator" bed of the Vaqueros of this district. 

Like these its less altered varieties show traces of thickly embedded 

round dots and flakes that are'almost certainly the remains of diatoms, 

and the shale has the characteristic flaky texture of diatomaceous
BULLETIN 398 PLATE XI

X. AVENAL RIDGE AND TENT HILLS, SEEN FROM NORTHEAST ACROSS McLURE VALLEY.

Showing steeply dipping Cretaceous strata on Avenal Ridge, the conical hills of white Miocene shale extending 

into the distance and the terraced surface of the Jacalitos formation flanking the hills. Photograph by 

Ralph Arnold.

/>'. SILICEOUS SHALE OF SANTA MARGARITA I?) FORMATION (MIDDLE MIOCENE) AT HEAD

OF McLURE VALLEY.

Looking southeast along contact with underlying, less prominent Cretaceous shale on left. Note surficial 

overturn and typical vegetation of Miocene shale zone. Photograph by Ralph Arnold.
SANTA MARGAEITA (?) FORMATION. 93

material. The more siliceous shale seems to be almost entirely made 

up of the crushed diatom tests. A sample of shale from the middle zone in the locality of the above section contained 86 per cent of 

silica according to an analysis made by R. C. Wells, of the United 

States Geological Survey. The shale contains also fish scales and 

other particles of organic origin, but almost no molluscan remains. 

The laminae are locally yellowish and calcareous and similar to the 

foraminiferal shale of the Tejon.

Southeast of Little Tar Canyon the formation increases in thickness 

to about 1,200 feet, the increase being mostly in the brownish shale of 

 the upper portion. The base of the formation is approximately at the 

axis of the anticline of the Pyramid Hills. The shale appears on both 

sides of McLure Valley, with a general steep dip toward the valley 

and with little change in lithologic character or thickness.

The northernmost point at which the siliceous shale doubtfully

ascribed to the Santa Margarita (?) formation has been recognized in 

this district is at the northwest end of Reef Ridge. There the white 

shale forms a thin zone between the underlying and overlying sandstone formations. It has a thickness of only about 50 feet. On the 

west side of Jasper Canyon the Vaqueros is overlain by hard, brittle, 

yellowish-brown and black clay shale that may be a continuation of 

the Santa Margarita (?),but its relations have not been studied. A 

zone composed in large part of shale continues in the same position 

in the series at least as far as the main valley of Jacalitos Creek to the 

northwest. This zone is highly tilted and much broken up.

Southeastward along Reef Ridge the shale thickens gradually and 

continuously. Southwest of the head of Zapato Creek there is about 

200 feet of shale that is divided into two zones of about equal thickness. The lower one is of purplish, brownish, and white siliceous 

shale, similar to that forming the prominent outcrops of this formation elsewhere. The upper is of purplish and brownish, largely clay 

shale. This grades at the top into alternating beds of brown sandstone and dark clay shale, which make up a thickness of several hundred feet and which may or may not be a part of the same formation. 

It is possible that this sandstone and shale correspond to part of the 

thickness of shale found farther southeast, but, fossil evidence being 

lacking, the formation is restricted for the present to the beds that 

are purely shale. The most rapid thickening of the formation takes 

place between Zapato Canyon and Canoas Canyon. At the latter it 

is about 650 feet thick and comprises three almost equal zones; the 

lowest of these is of fine-grained purplish shale of medium hardness 

that is fractured into fine, needle-like, angular fragments; the middle 

one is hard, siliceous white shale; and the upper is soft brownish shale.

The same siliceous shale is found south of the Coalinga district, 

extending along the border of the Great Valley of California. The
94 COALIFGA. OIL DISTRICT, CALIFORNIA.

thickening of the shale terrane continues from the northwest end of 

Reef Ridge toward the south until at the Temblor ranch in western 

Kern County the strata of shale attain the remarkable thickness of 

5,400 feet. It is probable that a part of the formation there stands 

for a period of time not represented by deposits in the region of Reef 

Ridge and may coincide with a part or all of the Monterey shale 

(middle Miocene). The thickening of the shale southward probably 

takes place at its base, the beds in the Coalinga district representing an unconformable overlapping of the upper portion upon the 

Vaqueros.

FOSSILS AND AGE.

LIST OF FOSSILS.

The Santa Margarita (?) formation, from a point 8 miles north 

of Coalinga northwestward for a distance of at least 6 or 8 miles, is 

exceedingly fossiliferous, the principal species being the big oyster 

Ostrea titan Conrad, the big barnacle-like Tamiosoma gregaria Conrad, and the scallop shell Pecten estrellanus Conrad. The names 

Tamiosoma zone and "big oyster beds" have been locally applied 

to these fossiliferous strata. The species found in this bed by James 

H. Pierce and the writers are among the following, which comprise the 

fauna'for this formation in the district:

Santa Margarita (upper middle Miocene} fossils from the Coalinga district.

Name.

ECHINODEEMATA.

Astrodapsis whitneyi Remond.... ..........................

PELECYPODA.

Chione conradiana F. M. Andersen.. . ................

Cryptomya ovalis? Conrad .................................

Macoma nasuta Conrad. ....................................

Ostrea titan Conrad ........................................

Zirphaea dentata Gabb .....................................

GASTEROPODA.

Trophon (Forreria) carisaensis F.M. Anderson..............

CIRRIPEDIA.

4632.

y

Y

V

V

4G51.

v

Y

Y

4766.

X

Y

Y

' V

V

4805.

V

4841.

i

Y

V

4842.

Y

Y

4848.

Y

4632. At and northwest of San Joaquin Valley coal mine near Miocene-Eocene contact.

4651. Tamiosoma zone or "bigoyster bed " in canyon between old Standard Oil Company and California 

Oil Fields Limited camps, sec. 28, T. 19 S.. R. 15 E.; 8 miles north-northeast of Coalinga.

4766. Tamiosoma zone or "big oyster bed" above Big Blue, NE. } sec. 21, T. 19 S., R. 15 E., west of 

Peerless Oil property; 9 miles north of Coalinga.

4805. Waltham Valley, 13 miles southwest of Coalinga; oyster bed 2 miles west of Elmer Frame's house; 

sandstone under shale.

4841. Sandstone next to serpentine, at head of Bray and Secords Canyon, 3 miles south of Waltham 

Valley.

4842. Sandstone at mouth of Bray and Secords Canyon, south side of Waltham Valley. This sandstone 

underlies the shale in this vicinity.

4848. Nine miles north-northeast of Coalinga, just above Tamiosoma zone or "big oyster bed," one-fourth 

naile northwest of Peerless wells,
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XII

A. ARROYO CUTTING PLEISTOCENE SAND AND CLAY THAT COVER SAN JOAQUIN VALLEY. 

On plain east of Kettleman Hills, 2 miles southwest of Tulare Lake. Photograph by Ralph Arnold.

7}. FOSSIL PECTEN ESTRELLANUS BED IN SANTA MARGARITA (?) FORMAIIUN, lu MILES

NORTH OF COALINGA.

Part of Tamiosoma zone characteristic of tlie middle Santa Margarita (?) in the oil field. Note large Ostrea 

titan at the left. Photograph by Ralph Arnold.
SANTA MARGARITA (I) FORMATION. 95

FAUNAL-RELATIONS AND AGE.

The fauna of the Santa Margarita (?), though small, is one of the 

most characteristic that is found in the southern Coast Ranges. The 

association and abundance of certain unique species such as Tamiosoma gregaria Conrad, Trophon carisaensis F. M. Anderson, and Pecten estrellanus Conrad at once indicate its correlation with the Santa 

Margarita formation of the Salinas Valley and Carrizo Plain regions. 

The correlation of the siliceous shale in Reef Ridge with the Santa 

Margarita is based upon the similar stratigraphic position of these 

shales to beds on the western side of Waltham Valley, near the 

mouths of Bray and Secords Canyon, which overlie sandstones at 

locality 4842, containing the following Santa Margarita fauna:

Mytilus aff. mathewsonii Gabb. 

Ostrea titan Conrad. 

Pecten crassicardo Conrad.

Pecten estrellanus Conrad. 

Tamiosoma gregaria Conrad. 

Trophon carisaensis F. M. Anderson.

For a number of years the Santa Margarita formation was believed 

to be the equivalent of the San Pablo formation of the Mount Diablo 

region, but the stratigraphic work in the Coalinga district seems to 

show it to be older. At least it is quite evident that the Etchegoin 

formation represents at least a considerable part of the San Pablo, 

and as the Etchegoin lies well above the supposed Santa Margarita it 

seems likely that the latter is, at least in part, of greater age than the 

San Pablo.

With the Etchegoin and Jacalitos formations correlated as upper 

Miocene, it seems most logical to place the Santa Margarita in the 

upper part of the middle Miocene, thus confining the Monterey to 

the lower part of the middle Miocene. Such an arrangement would 

assign the far-reaching post-Monterey diastrophic period to the 

middle of the Miocene. This classification and correlation is of 

course more or less arbitrary and necessarily tentative, but it seems 

to best fit the information now in hand.

IMPORTANCE WITH RELATION TO PETROLEUM.

In the Coalinga field the Santa Margarita (?) formation has an 

important relation in different ways to the occurrence of the petroleum. In the Eastside field its base is taken as extending down 

through the Big Blue. This zone caps the Vaqueros formation, or 

productive zone, and although small amounts of oil and tar are 

found above its base there is none in commercial quantities. The 

Santa Margarita (?) is of chief importance there as forming an impervious capping which has held the oil in. In the Westside field 

the formations are thinner, ancj. sand becis of the Santa Margarita (?)
96 COALINGA OIL DISTRICT, CALIFOKNIA.

become part of the productive zone. In the Kreyenhagen0 field the 

Santa Margarita (?) formation acts, like the Big Blue, as an impervious capping that keeps the oil confined within the Vaqueros sandstone. The similarity of the shale so mapped to the organic shales 

that elsewhere have been considered the source of oil suggests the 

possibility that this formation has given rise to some petroleum, but 

no evidence has been found to bear out such a supposition.

JACAL1TOS FORMATION (EARLY UPPER MIOCENE}

DEFINITION AND GENERAL DESCRIPTION.

The formation overlying the shale mapped on Keef Ridge as Santa 

Margarita (?) consists of alternating beds and zones of both soft 

and indurated sand, gravel, and clay of many varieties which 

extend up to the base of the beds mapped as Etchegoin and which 

form a belt along the southwest side of the Jacalitos and Kreyenhagen Hills. This formation has a thickness that may be conservatively stated as being 3,500 feet. In places it is very fossiliferous, 

and on both sides of Jacalitos Creek especially there are characteristic 

exposures containing abundant well-preserved fossils. It forms a 

unit in the Tertiary series of the Coalinga district, and in'order that 

it may be conveniently so treated it will be referred to in this paper 

as the Jacalitos formation, owing to the occurrence in it of typical 

faunas along the creek of that name. The fossils indicate that it 

originated in upper Miocene time and that it is chiefly marine. In 

part, however, it is probably of fluviatile or lacustrine origin. It is 

represented in the northern portion of the district by similar beds 

aggregating a much smaller thickness. Its fauna gives it individuality, and in portions at least of the Coalinga district it is separated 

from the beds above and below by unconformities. It is probably

in part the equivalent of one or more of the upper Miocene formations 

known in other portions of the State, but until its definite relations 

to them have been worked out it is necessary to designate it by a 

local name.

MEANS OF RECOGNITION.

The most important features of the Jacalitos formation by which 

it may be recognized are its position in the series of Tertiary strata, 

as outlined on the geologic map and in the text, and the various 

fossils and fossiliferous zones that it contains. These are listed and 

discussed below. Owing to its lack of strong lithologic or topographic individuality, the fossils afford the only means which may 

be relied upon for separating it from the other sandy formations. 

The fossiliferous beds are frequently much indurated, and they occur 

at intervals on the surface as hard zones that project like saw teeth 

and by their resistance protect the beds immediately above and 

below them. Long parallel ridges are thus produced. The same
JACALITOS FORMATION". 97

featuro, however, is characteristic of other formations in this region. 

The occurrence in all parts of the formation of a great number of 

sand and pebble beds full of sand dollars is typical of it in the southern 

portion of the district, though this likewise is a characteristic of the 

formation above. The usual- character of the hills composed of beds 

of this formation is illustrated in Plates II, B, III, and XVII. In 

a rough way the formation may be distinguished as that portion of 

the series between the white shale of Reef Ridge below and the 

major beds of blue sand which throughout the district lie at the base 

of the formation (the Etchegoin) above it. This upper limit is 

indefinite, however, owing to the fact that through much of the district the Jacalitos includes a great thickness of blue sand beds in its 

upper portion.

The blue sand and pebble beds are a striking feature of the Jacalitos 

and Etchegoin formations in this district. The blue color is clue to 

a thin coating over the individual grains. An analysis of this coating 

made by R. C. Wells, of the United States Geological Survey, indicates that it is probably vivianite. Its appearance suggests that it 

might be of similar origin to the blue color frequently noticeable in 

tuffaceous sands, notably in andesite tuffs of Nevada, and that it 

might be a product of the decomposition of the minerals of a tuff, 

but it is believed that the color is of entirely different origin in these 

two types of deposits.

From its locality of typical occurrence in the Kreyenhagen and 

Jacalitos hills the Jacalitos formation extends southwestward into 

McLure 'Valley, where it has a similar position above the shale of the 

Santa Margarita (?) formation. Toward the northwest it rea.ches 

into the interior of the Diablo Range in the depression formed by 

the Waltham syncline and toward the north it extends across Alcalde 

Canyon and into the region around Pleasant Valley. North of 

Jacalitos Creek it no longer rests upon the shale of the Santa Margarita (?) formation, those beds being lacking, and north of Alcalde 

Canyon the Jacalitos ceases to be completely represented- The 

question of the relations of the beds of this age in the northern and 

southern portions of the district is complex and can be decided only 

on the basis of detailed paleontologic evidence, aided by study of the 

structure. Lithology fails almost entirely to be of service. The 

formation will be discussed separately for the areas lying to the 

south and to the north of Alcalde.

STRATIGRAPHIC RELATIONS. > !

The Jacalitos formation in the Kreyenhagen field is unconformable 

with the shale mapped as the Santa Margarita (?) formation, as maybe 

seen at the northwest end of Reef lUdge, where that shale becomes

88170 Bull. 398 10 7
98 COALINGA OIL DISTRICT, CALIFORNIA.

lost. Along the greater portion of Reef Ridge, however, a definite 

appearance of unconformity has not been found, and the line between 

the two formations is therefore drawn arbitrarily for the present 

where the beds that are predominantly shale give place above to 

sandy beds. Toward the head of Zapato Creek and thence westward is a succession of several hundred feet of alternating beds of 

brown sandstone and dark shale above the siliceous shale of the 

Santa Margarita (?) formation. These beds are mapped with the 

Jacalitos, tentatively, it being uncertain to which formation they 

properly belong.

In the northern part of the district the Santa Margarita (?) beds 

appear conformable with the beds above, but the overlap of the 

Jacalitos over the Santa Margarita (?) near Oil Canyon proves 

clearly that the relation is an .unconformable one. Owing to the 

lack of persistence in the lithologic peculiarities or outcrops of the 

beds and the scarcity of distinguishing characters, such as fossils for 

different beds in the series between the Tamiosoma zone and the 

Etchegoin formation, it would be a matter of great difficulty to 

.determine at what horizon the unconformity exists. The base of 

the Jacalitos formation in this part of the district is thought to be 

represented, however, by a prominent zone of gravel and conglomerate which contains an abundance of fossilized wood and which is 

fairly constant along the line mapped as the base north of Pleasant 

Valley. This zone has yielded a tooth of Pliohippus, an extinct 

horse. The writers are of the opinion that the zone represents a 

period of land in this area during which river or possibly lake gravels 

were deposited.

The relation of the Jacalitos to the overlying formation, the Etchegoin, is similar, in that the Etchegoin has the same dip and -an

appearance of conformity with it in most places, but overlaps upon 

it elsewhere. The line between these two formations is drawn at the 

base of the beds which overlapped the Jacalitos and were deposited 

upon the Cretaceous in the White Creek basin.

DISTRIBUTION AND LOCAL CHARACTER.

JACALITOS IN THE KREYENHAGEN HILLS.

From Jacalitos Creek southward the Jacalitos formation affords 

more complete exposures than elsewhere. The type locality for its 

fossils is along this creek, near which representative faunas have 

been collected from different horizons, as shown in the list of fossil 

localities (pp. 109-111). But the undisturbed monocline that continues the same beds immediately to the southeast in the Kreyenhagen Hills furnishes somewhat better sections of. the formation as 

a whole, which has suffered considerable disturbance along Jacalitos 

Creek and in the hills to the north. Moreover, in the latter region
JACALITOS FORMATION. 9.9

the base of the formation does not appear within the area shown on 

the map and has not been definitely traced.

The following tabulated sections will give the best description of 

the lithologic character of the Jacalitos formation and its zones. It 

must be borne in mind, however, that the formation varies from 

place to place; that any single description applies merely to a single 

locality; that the different zones noted are not sharply separable, 

but grade into one another, all containing elements in minor quantity 

common to the others; and that a great variety of sedimentary beds 

occur that would necessitate almost endless discussion to describe in 

detail. Although the formation is thus varied, part of the variation 

noticeable in the sections may be due to the fact that exposures are 

not complete and that beds and fossils apparent in one place are 

frequently hidden in others. It is especially difficult to determine 

the relative quantitative importance of clay or somewhat compacted 

shale, for the reasons that the firmer sand beds are better exposed 

and therefore appear to dominate and that it can not always be 

determined whether the softer unexposed beds are fine sand or clay.

The following is a section of the Jacalitos along the creek of that 

name, from the summit of the formation (at the north base of the 

1,220-foot hill in the eastern part of sec. 31, T. 21 S., R. 15 E.) to its 

contact with the prominent Vaqueros beds at a point not shown 

on the map, about 1£ miles west-northwest of the end of Reef Ridge 

(in the middle of sec. 11, T. 22 S., R. 14 E.).

Section of the Jacalitos formation on Jacalitos Creek.

Feet. 

Bluish to brownish-gray clay and clayey sand, alternating with light-gray and

olive-gray pebbly sand, with occasional hard fossil layers, and with Pecten 

estrellanus zone at base (fossil locality 4647); overlain by blue sand at the 

base of the Etchegoin.................................................. 750

Massive beds of buff and olive-gray sandstone and sandy clay interbedded 

with thin and thick beds of olive-gray pebbly sandstone and gravel, and 

 occasional sandstone layers. Sand dollars are numerous throughout, usually in the pebbly layers. (See fossil locality 4784.) At the base (at the 

forks of Jacalitos and Jasper creeks) is a bed of dark-brown sandstone containing a rich fauna; top of the big Trophon zone (fossil locality 4765)..... 1, 300

Alternating heavy beds of coarse gray and brown sandstone and thin beds of 

fine sandstone and sand of the same colors, with some beds of gritty olivegray sandstone and hard fossil layers. Two hundred feet above base is a 

bed with large Astrodapsis (fossil locality 4654), near the base of the big 

Trophon zone........................................................... 500

Alternating beds of grayish and brownish sand and sandstone with some sandy 

clay and fossil layers in the sandstone.................................... 750

Alternating beds of soft gray and brown shale and sandstone, much tilted

 and fractured and in part overturned.................................... 500±

3, 800±
100 COALINGA OIL DISTRICT, CALIFORNIA.

The basal portion of this 

section rests upon tt.e 

steeply tilted Vaqueros beds 

that are the continuation 

of the prominent strata on 

the face of Reef Ridge. 

Shale similar to the typical 

shale mapped as Santa Margarita( ?) is entirely lacking, 

but it is possible that the 

much disturbed basal zone 

of this section is unconf ormable with the Jacalitos 

and belongs with the Santa 

Margarita (?) formation. It 

may be the continuation of 

the similar thickness of 

alternating beds of brown 

sandstone and dark shale 

overlying the typical shale 

of the Santa Margarita (?) 

along Zapato Creek, at the 

base of the next section to 

be described.

The middle portion of the 

Jacalitos formation, in this 

locality especially, contains 

large unconsolidated accumulations of fine pebbles, 

sometimes in thick beds by 

themselves and sometimes 

interbedded in thin layers, 

in the sand beds or scattered throughout the sand. 

These coarse beds are frequently fossiliferous, and 

sand dollars are especially 

abundant in them.

The uppermost beds of 

the above section underlie 

the lowest one of a number 

of prominent blue sand beds 

that are a characteristic 

feature of the landscape in 

this district along the belt
JACALITOS FORMATION. 101

of Etchegoin beds. The line of contact between the Jacalitos and 

Etchegoin formations in the region of the above section is drawn 

on the basis of this lithologic break and of the characteristic fauna 

that occurs in a bed just above, at fossil locality 4761. The beds 

above and below the contact dip with apparent conformity at an 

angle of about 25°.

The section in figure 4a affords a summary description of the Jacalitos formation on Zapato Creek. The alternating sandstone and 

shale beds at the base of this section, as stated before, may belong 

more properly with the shale of the Santa Margarita (?) formation 

and represent a change that gradually takes place toward the northwest in the character of the sediments in the upper portion of that 

formation. Zone zb in the section (fig. 4) is well exposed for several

a The letters in figure 4 indicate the following beds:

T.ulare. 

a. Hill-forming incoherent sand and gravel at base of Tulare.

Etchegoin.

Feet. 

&. Gray sand, sandstone, and clay, with Mya bed at top and Ostrea bed at base (near localities 4722

and 4744); upper Mya zone..................................................................... 100

c. Largely clay and fine sand...................................................................... 150

d. Largely gray sand containing sand dollars and with Area bed near bass ......................... 100

e. Gray sand and pebbly gravel with locally harder beds of sandstone, forming a rich fossil zone

(locality4705); Pectencoalingaensis zone....................................................... 100

/. Olive-gray fine sand and pebbly sand with thin sandstone layers, interbedded with clay......... 300

g. Bed of .light-blue sand, the highest of the blue-sand zone......................................... 10

ft. Massive beds of gray sand and sandy clay with occasional thick beds of blue sand ............. 1 290

i. Prominent zone of pebbly sand with hard layers, Area abundant................................ 30

j. Massive gray, smooth-weathering sand like coarse beach sand, containing many inconstant lamina) of hard brownish-gray sandstone alternating with inconspicuous beds of clay, and with some 

blue sand...................................................................................... 800

fc. Prominent bed of massive, olive-gray, compact, irregularly bedded sand........................ 20

I. Minor gray sand and clay beds................................................................. 350

m. Prominent bed of cavernous-weathering blue sand.............................................. 50

n. Alternating thick beds of gray sand and bluish clay, with thin layers of brown sandy clay and with 

two prominent beds of blue sand in middle. This is about the equivalent of the upper Mulinia 

zone.......................................................................................... 200

o. Prominent blue-sand bed............. J......................................................... 25

p. Olive and light-gray sand and sandy clay....................................................... 425

q. Prominent group of blue-sand beds; three blue-sand beds close together forming a hill and associated with massive dark olive-gray sand, pebbly sand, and sandy clay with irregular bedding. 150 

r. Prominent bed of blue sand at base, with prominent massive beds of olive-gray medium-grained 

and pebbly sand and minor beds of clay and blue sand above; this is the base of the blue-sand 

zone and approximately that of the Etchegoin................................................. 375

3,475 

Jacalitos. : 

s. Soft, compact, massive, medium and fine-grained olive-gray and brownish sandstone, with some 

thin beds of clay shale and sandy shale, and with occasional pebbly beds. Overlain conformably by blue sandstone at the base of the Etchegoin........................................... 800

t. Calcareous sandstone with fossils, probably zone of Pecten cstrellanus............................ 10

M. Sandstone similar to that of s, with some hard layers of dark-brown sandstone.... .1............. 700

v. Fine-grained, gritty, white, ashlike shale........................................................ 15

w. Sandstone similar to that of s, with occasional thick beds of cross-bedded pebbly sandstone and

beds of sandy shale with flaky texture; at the top a hard bed containing Pecten............... 250

x. Similar sandstone and shale with concretions in sandstone near the top.......................... (150

y. Sandstone bed with Pecten, Panopea, sand dollars, barnacles, etc., the approximate equivalent

of the big Trophon bed on Jacalitos and Canoas creeks ........................................ 10

z. Soft, fine and medium grained, massive grayish and buff sandstone and sandy shale with occasional hard layers and pebbly beds; some coarse sandstone beds in upper part full of large fragments of petrified wood....................................................................... 740

za. Hard sandstone layers with poorly preserved fossils............................................ 50

zb. Alternating beds of fairly hard brown sandstone and dark clay shale, only doubtfully referable 

to the Jacalitos. It is underlain, to all appearance conformably, by the siliceous shale of the 

Santa Margarita (?) and may belong to that formation....................................... 000

3,825 

Total Etchegoin and Jacalitos............................................................ 7,300
102 COALINGA OIL DISTRICT, CALIFORNIA.

miles along the south side of the longitudinal valley of Zapato Creek, 

along that portion shown on the left in Plate VIII, the contact between 

this zone and the overlying soft sand zone being marked by the 

valley. Further work may show that the contact followed by this 

valley is an unconformable one. The abundant petrified wood in 

the beds above suggests their equivalence to the beds taken as the 

base of the Jacalitos north of Pleasant Valley and an origin other 

than marine. The big TropJion zone (y in fig. 4) above the fossil-wood 

beds forms a capping for a longitudinal ridge that extends in front 

of Reef Ridge on the north side of the valley. To the west of Zapato 

Canyon, where this longitudinal ridge coalesces with Reef Ridge, 

beds of the big TropJion zone continue to form prominent shoulders 

on the various lateral ridges that they cross.

Various other hard beds in the middle portion of the Jacalitos 

formation form similar lines of hills or partially continuous ridges 

along their strike and may thus be traced for a long distance, but 

most of them acquire greater induration only locally and give place 

to other beds as ridge formers after an extent of a few miles. In the 

hills between Jacalitos and Zapato creeks the middle portion of the 

formation is especially rich in sand-dollar beds, some of which are 

of fine gravel and form the most prominent hills. As the section 

explains, the top of the Jacalitos here as well as on Jacalitos Creek is 

marked by the overlying blue sands of the Etchegoin. In addition 

to this easy means of distinguishing between them an important 

fossil bed, the probable equivalent of the Glycymeris zone, may be 

traced most of the way between these two creeks near the base of 

the blue sand.

The following is a section along Canoas Creek from the top of the 

Jacalitos, which is immediately south of the house of Hugo Kreyenhagen, to its contact with the Santa Margarita(?) formation.

Section of the Jacalitos formation along Canoas Creek.

Feet.

Chiefly grayish sand and soft sandstone, with thick pebbly zone at base containing Pecten estrellanus (fossil locality 4767). Overlain by rich fossil bed 

of locality 4769, at base of Etchegoin....................................... 650

Chiefly massive, gray and buff, coarse-grained sand; a prominent bed of friable 

dark sandstone with Panopea, etc., at base................................. 1, 000

Similar sand with prominent ridge-forming bed at base........................ 350

 Similar sand with prominent bed, the big Trophon zone, at base............... 400

Similar sand with occasional sandstone layers and with prominent sandstone 

bed at base forming first hill northeast of Reef Ridge........................ 500

Similar sand grading below into sandy shale overlying the Santa Margarita (?) 

formation............................................................... 600

3,500
JACALIM FORMATION. 108

Between Zapato and Canoas creeks the beds follow low, gently rolling strike ridges and valleys, and although they are soft and not prominently exposed they may be traced by means of the topography and 

the belts of vegetation. A peculiar feature of the beds is that in several places those which form ridges west of Zapato Creek or part way 

across to Canoas Creek become transferred to strike valleys, and vice 

versa, the original tendency in some beds being reassumed farther 

along their course. This feature is equally characteristic of other 

portions of the Kreyenhagen and Jacalitos hills and of the overlying 

Etchegoin formation as well. This inconstancy frequently makes the 

task of tracing the beds a puzzling one.

The Jacalitos beds show every appearance of being conformable 

with the shale of the Santa Margarita (?) formation in the region of the 

foregoing section. The shale and sand 600 feet thick given at the base 

of the section are thought to be equivalent to the basal zone already 

discussed in connection with the previous sections. Northeast of the 

valley occupied by this zone there extends a prominent ridge formed 

by a succession of beds, containing numerous hard fossil layers and 

comprising a thickness of about 1,200 feet, that are the continuation 

of the similar beds found in the previous sections. In the central 

portion of this fossiliferous zone is the big Trophon zone.

The top of the Jacalitos here as elsewhere'is marked by a typical 

association of fossils in the summit beds, and the usual basal Etchegoin fauna, which is of somewhat different character, occurs in the 

beds just above. The line is marked here as in the previous instance 

by being at the base of the blue-sand beds of the Etchegoin.

Southeast of Canoas Creek the Jacalitos formation preserves a character and a thickness very similar to those given in the above sections. 

The fossiliferous sandstone beds become more indurated, so that they 

stand out like sawteeth on the summits of longitudinal ridges most of 

the way to Big Tar Canyon and form very pronounced features of the 

landscape. As this canyon is approached the beds assume steeper 

and steeper attitudes until they dip uniformly at angles varying 

between 50° and 60°. The chief new feature of the formation in tliis 

region is that some of the sand and pebble beds in its higher portion 

have the blue color characteristic of the basal beds of the Etchegoin. 

Confusion is thus introduced into the separation of the two formations, but the same paleontologic criteria used in distinguishing between them elsewhere still hold good here. In the neighborhood of 

Garza and Big Tar creeks the zone of blue sands extends down over 

800 feet into the Jacalitos, whereas farther southeast, as shown in the 

next section, it extends to a still lower horizon, the lowest at which it 

has been found anywhere. The exact similarity of the beds above 

and below the contact of this formation with the Etchegoin overlying, 

taken together with their perfect angular conformity, is almost con-
104 COALIHGA OIL DISTRICT, CALIFORNIA.

elusive evidence of their actual conformity and continuity. It is 

believed that here where these formations are so complete they form 

an unbroken sequence, whereas farther to the north, where the thicknesses are very much reduced, they are separated by an unconformity. 

Southeast of Big Tar Creek the beds begin to lose in prominence 

and to form nearly uniform rolling hills of soft sand with few large 

exposures. The dip in this region becomes uniformly about 60°. 

The following section shows the character of the formation at about 

the farthest point southeast in the Kreyenhagen Hills' at which 

a section of any completeness can be obtained from the surface 

exposures. Beyond this point the hills still preserve traces of their 

longitudinal strike structure, but much more faintly than farther 

northwest, and most of the beds are soft and weather out into 

surface sand that hides them. Fossils are only rarely to be found and 

there is next to no basis for separation between zones or formations.

Section of the Jacalitos formation on north side of Reef Ridge, 8\ miles' southeast of Big

Tar Canyon.

Feet.

Dark-gray sand, with about 20 feet of lightiblue sand at base.................. 120

Olive-gray sand, with light-blue sand at base; the basal portion is probably the 

main Pecten estrellanus zone found 1 mile northeast................:........ 350

Fine shaly yellowish-gray sand, with whitish-gray and dark-gray layers interbedded and some bluish pebbly sand; the lowest blue sand is at base....... 720

Compact medium-grained to coarse gray sand, like beach sand............... 275

Olive-gray speckled sand and soft sandstone, with appearance of a pepper-andsalt mixture............................................................. 275

Interbedded fine and medium grained grayish, whitish, and yellowish sand 

and speckled sand like the last, with some clay layers........................ 600

Fine and medium grained reddish, yellowish, and grayish sand and soft sandstone, with white sandy clay at top and coarse pebbly sand 300 feet below 

top; grading a.t base into soft whitish-gray sandy shale...................... 1, 200

3,540

JACALITOS IN THE REGION OF M'LURE VALLEY.

The Jacalitos is worn off over the summit of the Pyramid Hills 

anticline, but reappears on its southwestern flank in the northwestern 

portion of McLure Valley, dipping under the alluvium of the valley 

floor. The descriptions of the formation already given apply to it 

as it appears in this region. The exposures are in general poor.

Around McLure Valley the more siliceous beds of the Santa Margarita (?) grade upward into 500 to 600 feet of soft brown argillaceous shale and some sand that reach up to the base of a prominent 

bed of brown sandstone which is mapped as the base of the Jacalitos. 

Further investigation may prove the upper portion of the succession 

of beds here included in the' Santa Margarita('0 formation to be equivalent to the transitional shale and sandstone zone appearing at the 

base of the Jacalitos sections in the northern part of the Kreyenhagen Hills. Along the north side of McLure Valley and the valley
JACALITO& FORMATION. 105

of Avenal Creek the hard, prominent sandstone bed mentioned extends 

continuously with a dip toward the valley of about 50° and forms a 

succession of eminences. Along the southwest side it is not so 

easily traceable. Above this bed comes a succession of soft beds, 

chiefly of sand, aggregating about 2,600 feet in thickness up io the 

base of a prominent bed of soft, coarse blue sandstone like that 

in the upper portion of the Jacalitos and the lower portion of the 

Etchegoin, previously noted. This sandstone influences the topography by forming hills as much as 100 feet high. About 1,000 feet 

stratigraphically above it a similar blue bed makes its appearance 

in the axis of the plunging syncline near the head of McLure 

Valley, and continues to outcrop for 1 or 2 miles on either side of 

the fold along lines diverging from the axis. The lower of these 

two beds is the base of the blue-sand zone, and the strata between

are in part of inconspicuous blue-sand beds. The upper bed is

assumed as the approximate summit of the Jacalitos formation and 

is so mapped. The thickness of the formation so delimited is about 

3,600 feet, the same as in the Kreyenhagen Hills, and the blue-sand 

zone has about the same thickness as in the section last given.

JACALITOS IN THE JACALITOS HILLS.

Passing now back to the region .of the type locality for this formation, we may take up its occurrence from that locality northward. 

In the Jacalitos Hills a plunging anticlinal fold breaks up the regular 

monoclinal structure in the lower half of the formation, causing it to 

be folded at various angles and in various directions and to spread 

over a wider area toward the west. The base of the formation is not 

known to appear within the area mapped.

The regularity of dip of the upper half of the formation, however, 

is little disturbed and a continuous section is well exposed. This 

portion affords a great many excellent fossils, the principal zones of 

which are traceable directly into those south of Jacalitos Creek, 

and in general the formation here is similar to the occurrences already 

described. It preserves the general character of a great thickness 

of soft beds that are chiefly of sand and that vary rapidly both horizontally and vertically into all gradations of texture from that of 

clay to that of pebbly gravel. The beds are in places very gypsiferous, and yellow deposits of sulphur occur along the joint cracks. 

In the southern part of the Jacalitos Hills the lowest zone exposed 

in the axis of the anticline corresponds to the central portion of the 

zone of pebbles and sea urchins found on Jacalitos Creek.

In the central part of the hills, 700 to 800 feet below the top of the 

formation, there outcrops a prominent bed several feet thick of 

white, hard, gritty, very brittle, and much fractured shale somewhat 

similar to the hard variety of the "indicator" bed in the Vaqueros,
106 COALINGA OIL DISfMCf, CALifOMlA.-

north of Coalinga. It may be volcanic ash. It occurs at a horizon 

just above that of Pecten estrellanus in the uppermost zone in the 

section on Jacalitos Creek given above. The bed extends northward a little more than a mile from the northwest corner of sec. 31, 

T. 21 S., R. 15 E., following the east side of the road from Alcalde to 

Jacalitos Creek, and there becomes lost. It seems to be continued by 

a bed of white shale found at a similar horizon on the west side of 

the 1,900-foot hill southeast of Alcalde. It is underlain with fairly sharp 

contact by very fossiliferous fine clayey sand and medium-grained 

sand full of large pectens, cardiums, panopeas, etc., and overlain 

very sharply by gritty and gravelly sand full of sea urchins (fossil 

localities 4638 and 4639). This upper contact is wavy, the sand 

bending down a foot or two into concavities in the surface of the 

shale in places, but it is not thought that the contact represents an 

unconformity. The inequalities were more probably original variations of the surface of deposited material due to currents or other 

local causes.

The succession of be'ds exposed on the western flank of the 1,900- 

foot hill 1 mile southeast of Alcalde, east of the road leading southward from Alcalde toward Jacalitos Creek, comprises about 1,600 

feet of sand, clay, gravel, and fossiliferous sandstone up to the base 

of the blue beds which mark the Etchegoin formation. Locally 

on the flank of this hill the beds have a slight stain resembling that 

due to the presence of oil. West of the road above mentioned the 

Jacalitos beds are chiefly sand, with some clay and gravel and with 

fossils. They overlap upon the steeply tilted Cretaceous strata and 

are warped into a number of low plunging folds. Still farther west 

the Jacalitos overlaps over a wide extent of country in the Waltham 

syncline, along which it has been traced 6 miles west of the area 

shown on the map, along Jacalitos Creek as far as the road to Stone

Canyon.

JACALITOS IN THE ALCALDE HILLS.

North of Waltham Creek the Jacalitos formation has not the 

great thickness that characterizes it throughout its extent in the 

south, being only about 800 feet thick. This thinning northward 

is very rapid in the immediate vicinity of Waltham Creek as it is in 

the Etchegoin formation as well, indicating that the lower portion of 

Alcalde Canyon follows a line that has been an extremely important 

locus of erogenic movements. It has not been determined whether the 

change that takes place in the Jacalitos is a constant thinning affecting all the beds of the formation, or whether it is due to the absence 

of some large parts of the formation, owing either to their not having 

been deposited north of Waltham Creek or to their having been 

worn away. It may be that the zones full of fossil wood near the
JACALITOS FORMATION. 107

base of the Jacalitos in the Kreyenhagen Hills and north of Pleasant 

Valley are the same, but it is believed that the area north of Waltham 

Creek was land during the earlier part of Jacalitos time and that the 

lower portion of the formation was not deposited there.

The formation over the area of the Alcalde Hills retains the general character of the beds to the south. It is a varied formation 

of incoherent yellow, brown, and gray sand, sandstone, clay, and 

gravel, locally containing abundant fossils. The typical fauna of 

the lower part of the formation in the type locality along Jacalitos 

Creek is not present. The beds are evidently of near-shore origin, 

being in many places roughly bedded, cross-bedded, and varied. 

They are full of gypsum. The formation is described in connection 

with the section (fig. 4). The base, as mapped, is a fossiliferous bed 

containing Pecten estrellanus, etc., which is traceable southward 

from the San Joaquin Valley coal mine to Waltham Creek. It is

underlain, with an appearance of conformity, by a zone of clay and 

fine sand about 300 feet thick, which has been mentioned before 

as possibly belonging to the horizon of the Big Blue (Santa Margarita?), but which is mapped with the Vaqueros. The summit of the 

Jacalitos formation is at the base of the Glycymeris zone, which is the 

equivalent of the basal Etchegoin as found elsewhere. The beds 

along this contact do not give evidence of unconformity.

JACALITOS IN THE AREA NORTH OF PLEASANT VALLEY.

The beds in the northern part of the district that have been correlated with the Jacalitos constitute that part of the series on 

Joaquin Ridge which lies between a prominent basal zone of gravel 

that outcrops typically on the hill where the tanks are situated 

above the Standard Oil Company's wells (in the northeast corner of 

the NW. i sec. 28, T. 19 S., R. 15 E.) and the base of a zone of bluishgray sand and abundant fossils (the Glycymeris zone) outcropping 

typically on the hill where one tank stands in the northwest corner 

of the SW. i sec. 34, T. 19 S., R. 15 E. This portion of the series 

consists of about 1,600 feet of alternating fine gray sand and clay, 

pebbly and medium-grained sand and sandstone, and gravel. The 

basal pebbly zone -has a thickness of about 150 feet, of which the 

lower half is a solid layer of pebbly gravel locally hardened to conglomerate and the upper half thinly bedded brown, gray, and, 

in some places, pinkish sandstone and sand intermingled with pebbles and with occasional shaly layers. This zone contains a great 

abundance of petrified wood in large fragments and at one place 

(locality 5015) a tooth of an extinct species of horse was fo'und in it. 

An opinion as to the possible nonmarine origin of this zone has been 

expressed above. Owing to the great variety of constituents in these 

beds and the likelihood of their furnishing further fossils they would
108 COALINGA OIL DISTRICT, CALIFORNIA.

make an interesting subject for detailed study. The prominent 

basal beds are shown at the right of the center in Plate XVII. The 

rest of the formation is mostly soft sand, with which hard sandstone 

and conglomerate layers, pebbly sand, and sandy clay beds are frequently interbedded. The upper 700 feet consists of fine lightcolored powdery sandstone, sandy clay, and clay, usually forming a 

belt of low topography but interbedded with several locally prominent 10 to 40 foot zones of blue pebbly sandstone like that in the 

Kreyenhagen Hills and in the overlying Etchegoin. The lowest of 

these blue strata are very conglomeratic and full of large fragments 

of silicified tree trunks. Impressions of leaves of deciduous trees 

were found in one of the lenses of clay common in this conglomerate, 

about 650 feet below the base of the Etchegoin 1\ miles north of 

Coalinga, on the west side of the SE. \ sec. 28, T. 19 S., K. 15 E. No 

marine fossils have been found in place in the Jacalitos beds north of 

Pleasant Valley.

FOSSILS AND AGE.

FOSSILS.

Like the Etchegoin above it, with which it is closely allied, the 

Jacalitos is fossiliferous in many localities in the Coalinga district 

and adjacent regions, especially in the Waltham Valley, 13 miles 

southwest of Coalinga. In the upper part of the formation the 

fossils are usually in a very good state of preservation; in the lower 

part the original shell has usually been leached out and replaced by 

other material, and some of the fossils are simply casts.

The following species have been found in the Jacalitos formation 

in the Coalinga district or in the Waltham Valley:

Jacalitos (upper Miocene) fossils from the Coalinga district.

Name.

ECHINODEEMATA.

Astrodapsis jacalitosensls Arnold. 

Echinarachnius gibbsii R<5mond..

PELECYPODA.

Area trilineata Conrad ......................

Cardium meekianum Gabb..................

Cardium sp. a...............................

Cardium sp .................................

Chione securis Shumard.....................

Cryptomya ovalis? Conrad...................

Diplodonta harfordi? F. M. Anderson .......

Diplodonta parilis Conrad...................

Diplodonta sp. indet........................

Dosinia jacalitosana Arnold..................

Glycymeris sp. indet........................

Macoma secta Conrad........................

Macoma jacalitosana Arnold.................

Macoma vanvlecki Arnold...................

Macoma sp. a................................

Metis al ta? Conrad..........................

Metis sp....................................

Monia macroschisma Deshayes.............

Mulinia densata Conrad ....................

Mytilus (Mytiloconcha) coalingensis Arnold.
JACALITOS FORMATION. 109

Jacalitos (upper Miocene) fossils from the Coalinga district Continued.

Name.

PELECYPODA continued.

GASTEROPODA.

Lunatia lewisil? Gould. ................................

Margarita johnsoni Arnold. .............................

Thais kettlemanensis Arnold ...........................

C1RRIPEDIA.

PISCES.

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4030. Hill 4 miles N. 85° W. of'Coalinga, not far from contact with concretionary sandstone beds mapped 

as Cretaceous (Chico), on west side of sec. 35, T. 20 S., R. 14 E. Lower beds.

4038. Three hundred feet east of nose of 1,300-foot ridge, three-fourths mile southeast of Alcalde, in center 

of sec. 24, T. 21 S., R. 14 E. Olive-gray gypsiferous sand overlying white shale bed, about 700 or 800 feet 

stratigraphically below top of the Jacalitos formation as mapped. Upper beds.

4639. About 2 miles south of Alcalde on south side of 1.548-foot hill, in sand immediately above and below 

white shale bed, in sec. 25, T. 21 S., R. 14 E. Same horizon as 4638, upper beds.

4640. Near Commercial Petroleum well, 3 miles southwest of Coalinga. Upper beds.

4642. About 20 miles south of Coalinga, in Kreyenhagen Hills. Gray sand 500 feet southwest of top of 

1,053-foot hill, four-fifths mile southwest of El Cerrito well, in NW. i SW. i sec. 15, T. 23 S., 11. 17 E. 

Pecten estrellanus zone, or upper beds.

4644. Southeast base of 1,300-foot hill, on north side of Jacalitos Creek, just north of old adobe house 

 two-thirds mile above fork of Salt Creek, in center of south side of sec. 31, T.21 S., R. 15 E. Upper beds.

4645. One mile west of Garza Creek on top of ridge north of Clark's place, in the NW. J NE. \ sec. 3, T. 23 

S., R. 16 E.; big Trophon zone, about 900 or 1,000 feet stratigraphically above shale of Santa Margarita (?) 

formation. Lower beds.

464u About 3 miles west of Coalinga, just north of Commercial Petroleum well No. 1, in canyon. Middle or upper beds.

464V. On top of ridge between Salt Creek and Jacalitos Creek, about 5 miles south-southeast of Alcalde, at 

elevation of 1.300 feet, on north line of sec. 6, T. 22 S.,'R. 15 E., hard sandstone layer through pebbly olivegray sand. Pecten estrellanus zone about 700 to 800 feet stratigraphically below summit of formation. One 

of typical Jacalitos localities. Upper beds.

4649. West point of 1,308-foot ridge three-fourths mile southeast of Alcalde, S W. J NE. i sec. 24, T. 21 S., 

R. 14 E. Middle beds.

4650. Lowest fossil bed on west face of 1,900-foot hill southeast of Alcalde. Middle beds.
110 COALINGA OIL DISTRICT, CALIFORNIA.

Jacalitos (upper Miocene) fossils from the Coalinga district Continued.

Name.

ECHINODERMATA.

PELECYPODA.

Dlplodonta sp. indet. ..............................

Panopea estrellana Conrad .........................

Paphia stalevi? Gabb. . ............................

Pecten crassicardo Conrad ..........................

GASTEEOPODA.

Chrysodomus imperialis Dall. ......................

Lunatia lewisii? Gould.............................

Margarita johnsonl Arnold .........................

Melongenasp.o... .................................

CIRRIPEDIA.

PISCES.

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4652. Onpoint of ridge three-fourths mile south-southwest of Alcalde, one-fourth mile south of south bend 

inroad, SE. Jsec. 23, T. 21S..R. 14E. Middle beds.

4653. Nearly 4 miles southwest of Coalinga, one-third mile south of Commercial Petroleum well at point 

of hills on north side of Waltham Creek, just east of Anticline Canyon road, in the very southwest corner 

of sec. 7, T. 21 S., R. 15 E. Middle or upper beds.

4654. On Jacalitos Creek, one-half mile above confluence with Jasper Canyon, on south side of sec. 1, T. 22 

S.,R. 14 E. Lower beds.

4745. On ridge south of Garza Creek, 1 mile southeast of Mr. Clark's place, NE. £ SW. £ sec. 2, T. 23 S., 

R. 16 E.; big Trophon zone about 800 feet stratigraphically above shale of the Santa Margarita (?) formation. 

Lower beds.

4745o. Big Echinarachnius gibbsii zone about 800 feet stratigraphically above 4745, in NW. J SE. J sec. 2, 

T. 23 S., R. 16 E. Middle beds.

4746. Sixteen hundred feet stratigraphically above 4745, on ridge-east of Garza Creek, NE. 1 sec. 2, T. 23 S., 

R. 16 E. Upper beds.
JACALITOS FORMATION. Ill

4747. Same locality as 4746,150 feet stratigraphically higher. Pccten cstrcllanus zone, or upper beds.

4763. Southwest of Coalinga district, on little ridge 200 yards north of Stone Canyon and Waltham Creek 

road where it crosses a little stream before reaching Waltham Valley from the west. Lower zone.

4765.' Big Trophon zone on Jasper Creek just above fork of confluence with Jacalitos Creek, on west side 

of center of the SW. 4 sec. 6, T. 22 S., R. 15 E. About 2,000 feet stratigraphically below summit of formation. 

One of typical Jacalitos localities. Lower beds.

4767. On southeast side of Canoas Creek, three-eighths mile above Hugo Kreyenhagen's house, in the 

NW. i SW. £ sec. 27, T. 22 S., R. 16 E.. Pecten estrellanv* zone, or upper beds. Abundance of beautifully 

preserved specimens.

4784. On Jacalitos Creek, about 7 miles southwest of Coalinga, shaly sandstone a few hundred feet stratigraphically above big Trophon zone of 4765.

5015. Basal gravel bed or the Jacalitos, SE. J sec. 15, T. 19 S., R. 15 E., northeast of Octave oil wells.

FAUNAL ZONES.

Three rather easily distinguishable fossiliferous zones occur in the 

Jacalitos. The lowest one of these, sometimes called the' ' big Trophon 

zone, "is characterized by such forms as Trophon (Forreria] ponderosum Gabb, Macoma vanvlecki Arnold, Panopea estrellana Conrad. 

Dosinia jacalitosana Arnold, and Astrodapsis jacalitosensis Arnold, 

The fauna of this zone is typically developed at locality 4765. The 

same zone is also represented at the following localities: Nos. 4636, 

4645, 4654, 4745, 4763, 4765, and 5015 (?).

The middle zone has a less well characterized fauna, but usually 

yields very large specimens of Echinarachnius gibbsii Re"mond, also 

Panopea generosa Gould and Schizoihserus pajaroanus Conrad. It 

is represented by the localities Nos. 4646(3), 4649, 4650, 4652, 4653(?), 

and 4745a.

The upper zone, or Pecten estrellanus zone, as it is sometimes 

called, is characterized by large specimens of Pecten estrellanus 

Conrad, Pecten oweni Arnold, and large individuals of EchinaracJinius giblsii R6mond. The species common in this zone are beautifully preserved at locality 4767. The zone is also represented at 

localities 4638, 4639, 4640, 4642, 4644, 4646, 4647, 4653, 4746, 4747, 

and 4767.

FAUNAL RELATIONS AND AGE.

The fauna of the Jacalitos formation not only contains a considerable number of unique species, but the association in it of species 

known elsewhere in other formations is peculiar.

The species which are characteristic of or found more commonly 

in the Jacalitos than elsewhere, in.addition to the new species described 

from it in Bulletin 396, are Ohione securis Shumard; Echinaraclinius 

giblsii Re"mond, large variety; Melongena sp. a; Schizodesma abscissa 

Gabb; Tellinaaragonia Dall;and Trophon (Forreria) ponder osumGafob.

The species which are found in the Jacalitos and the underlying 

Santa Margarita(?) formation, but which it is believed do not extend 

into the overlying Etchegoin, except possibly in rare instances, 

are Pecten estrellanus Conrad, Pecten crassicardo Conrad, Tamiosoma 

gregaria? Conrad, and Zirplisea dentata Gabb. The forms noted as 

questionably Tamiosoma gregaria are different from the typical 

Tamiosoma and are possibly large specimens of Balanus, but the few 

examples found were too poor for identification.
112 COALINGA . OIL DISTRICT, CALIFORNIA.

Numerous fragments of Tamiosoma gregaria, Ostrea titan, and 

Pecten estrellanus are scattered over the surface of the fossil-wood 

bearing conglomerate beds of the upper Jacalitos in the low hills 

south of Oilfields and 7 miles north-northeast of Coalinga, in the 

SE. | sec. 34, T. 19 S., R. 15 E. They have the appearance of being 

in place in these beds, but it is believed to be more probable that they 

are either inclusions in the Jacalitos of fossils derived from the Santa 

Margarita(?) beds or recent float from the higher hills.

The species which are common to the Jacalitos and the overlying 

Etchegoin, but which do not extend below into the Santa Margarita (?) 

are Area trilineata Conrad, Cardium meekianum Gabb, Cryptomya 

ovalis? Conrad, Diplodonta Jiarfordi F. M. Anderson, Diplodonta 

parilis Conrad, Echinarachnius gibbsii Remond, Chrysodomus portolaensis Arnold, Macoma secta Conrad, Monia macroschisma Deshayes, 

Mytilus (Mytiloconcha) coalingensis Arnold, Ostrea atwoodi Gabb, 

Pecten oweni Arnold, Schizothderus pajarodnus Conrad, Paphia 

staleyi? Gabb, and Paphia tenerrima Carpenter.

Thais Jcettlemanensis Arnold properly belongs in the list of the 

species unique in the Jacalitos, as it occurs alone at the type locality 

of the species (locality 4680, which is included in the general locality 

4679), which is on the axis of the Coalinga anticline and in beds below 

the lowest fossiliferous horizon that is certainly Etchegoin. It is 

abundant toward the base of the Jacalitos.

All the determinable fossils that have been found in the Jacalitos 

in the southern portion of the district are of salt-water species, 

which indicate the marine origin of the greater part of the formation. 

The basin of deposition, however, appears to have been a shallow 

one, and it is not unlikely that portions of the great thickness of 

beds were deposited outside of the area occupied by the salt water 

at times when subsidence did not keep pace with deposition and the 

consequent encroachment of the land upon the sea. Beds formed at 

such times may be represented by the fossil-wood zones noted and 

possibly by some of the gravel and sand deposits in other parts of 

the formation.

The Jacalitos may be defined as a formation embracing about 

3,600 feet of sand, gravel, clay, and sandstone, lying between the 

Santa Margarita (?) formation below and the Etchegoin above, and 

containing in its fauna among others at least 15 species which are 

unique, 4 which are common to it and the Santa Margarita but do 

not extend up into the Etchegoin, and 15 which are common to it 

and to the Etchegoin but do not extend down into the Santa Margarita fauna. The age of the Jacalitos is believed to be the early 

part of the upper Miocene. It has a known range of about 75 miles 

along the Diablo and Temblor ranges, from Coalinga to the Elkhorn Plain. Whether it will be possible to recognize the fauna outside of this area is not known; for the present it seems advisable
ETCHEGOIN FORMATION. 113

to use the name only in a local way and in the general geologic column to place it tentatively as an equivalent for the upper part of the 

Santa Margarita and the lower part of the San Pablo.

IMPORTANCE WITH RELATION TO PETROLEUM.

The Jacalitos formation is not petroliferous in the Eastside field 

in the northern part of the district, but becomes very productive 

in the Westside field owing to the thinning out of the formations 

between it and the Tejon. In the Kreyenhagen field it is not known 

to be productive at any point, no oil appearing to have 'escaped from 

the Tejon and Vaqueros through the shales of the Santa Margarita (?). 

The thickness and character of the Jacalitos throughout the district 

have an important bearing on the question of the accessibility of the 

oil, owing to the fact that most of the wells have to penetrate it in 

order to reach the oil sands at depths at which they will be productive. 

A knowledge of its thickness has been especially useful in making 

calculations as to the depth at which the oil sands may be found in 

the Kreyenhagen and Kettleman hills.

ETCHEGOIN FORMATION (UPPERMOST MIOCENE}.

DEFINITION.

ORIGINAL DESCRIPTION.

The name Etchegoin series was applied by F. M. Anderson ° to a 

great thickness of beds of little-consolidated sand, gravel, and clay, 

characteristically blue at the base, extending a long distance both 

northwest and southeast from Coalinga along the border of the Diablo 

Range. The name of the formation was " derived from its characteristic development in the vicinity of the Etchegoin ranch, some 20 

miles northeast of Coalinga." This is an abandoned sheep ranch at 

the northern edge of the area mapped, 12£ miles northeast of Coalinga (NW. I sec. 1, T 19 S., E. 15 E.). A general description of the, 

formation was given. Its upper limit was stated to be at the base of 

the fresh-water deposits in the vicinity of Tulare Lake and the Kettleman Hills, .described as the Tulare formation.

Mr. Anderson states that "one or two fossil horizons are to be 

recognized in the Etchegoin sands, one near their bottom and another 

some distance above." The one near the bottom is stated to be the 

more characteristic horizon. It is the one that will be later described 

as the Glycymeris b zone and as the. base of the formation. The 

nearest locality to the Etchegoin ranch for which a description or 

section was given is 9 miles north of Coalinga, and this may therefore 

be taken as the type section. In this section the base of the formaa Anderson, F. M., A stratigraphic study in the Mount Diablo Range of California: Proc. California Acad. 

Sci.,3d scr., vol.2, 1905, No. 1. ...

<> To avoid confusion it should be stated that this same genus was referred to as Pectunculus in the paper 

quoted. That name has been replaced by the one here used owing to the fact that Gly'cymeria was the 

original designation of the genus.

88170 Bull. 398 10 8
114 COALINGA OIL DISTRICT, CALIFORNIA.

tion was shown considerably above the Tamiosoma zone, which is 

described in the present report as part of the Santa Margarita (?) formation. The position of the lower portion of the Etchegoin was further 

indicated by the statement in the general description that it was 

characteristically a zone of bluish sand. The-whole formation was 

referred to the Pliocene and was stated to be unconformable with 

the beds below.

PRESENT DEFINITION.

In accordance with the original description, and on the basis of the . 

reasons stated below, the Etchegoin formation is mapped and described in the present paper as the succession of beds of sand, gravel, 

and clay, in part indurated, occurring in the oil field northeast of 

Cpalinga above the base of the hill-forming sandstone beds referred to 

for convenience as the Glycymeris zone, and in the Kettleman Hills 

below the fresh-water beds described as the base of the Tulare formation. The upper limit is not defined for the hills north of Coalinga 

owing to the indefiniteness of the line between the Etchegoin and 

Tulare there. The base of the formation may be still more sharply 

defined as the lowest horizon of the Tertiary beds that rest directly 

upon the Cretaceous in the basin of the White Creek syncline, about 

15 miles northwest of Coalinga, for there no question can exist of the 

individuality of the Etchegoin as a stratigraphic unit or of its proper 

delimitations. Such a definition on the basis of the White Creek 

occurrence seems permissible, inasmuch as there can be little doubt 

that the fossiliferous beds at the base of the formation in the White 

Creek basin are equivalent to those north of Coalinga referred to as 

the Glycymeris zone. This fossil zone was probably at one time continuous between the two localities.

Strata in other portions of the Coalinga district are referred to the 

Etchegoin formation On the basis of paleontologic correlation with 

the basal beds on Anticline Ridge and in the White Creek basin and 

with the upper beds in the Kettleman Hills. The formation so 

described probably belongs as a whole in the Miocene, though its 

uppermost beds may 'reach into the Pliocene. It is very rich in 

marine fossils and is chiefly of marine origin, but evidence will be. 

mentioned later pointing to the origin of portions of it in bodies of 

nearly fresh water.

BASE OF THE FORMATION.

The Glycymeris zone is an extremely fossiliferous bed of somewhat 

indurated sand that forms the summit of the hill at the northwest end 

of Anticline Ridge (fossil localities 4656, 4658, and 4659) and extends 

continuously from that point along the line mapped as the base of the 

Etchegoin formation. The beds of this zone are shown on the right 

side of Plate XVIII, along the summit qf Anticline Ridge, in the 

middle distance in the picture. The zone is underlain at this locality 

by clay that.forms a belt of low relief in the topography and that is
ETCHEGOIN FORMATION. ' 115

classed in the Jacalitos formation. It is overlain by a thick succession 

of bluish-gray sand beds interbedded with dark-gray sand. The zone 

affords almost perfect specimens of many species of fossils that make 

up a distinctive fauna. It is called the Glycymeris zone for ease of 

reference, because it is an important datum line that may be repognized by the association of fossils contained in it. It could not be 

identified surely by the Glycymeris alone, for although the genus is 

perhaps more characteristic of this zone than of any other, its distribution at other horizons is wide. Approximately, if not exactly, the 

same horizon marks the base of the beds overlying the Cretaceous 

sandstone in the synclinal basin of White Creek, as shown by the 

typical association of fossils (fossil localities 4662, 4663, and 4664). 

Somewhere between Oil Canyon and the White Creek area an. overlap 

of the Etchegoin upon the Jacalitos and earlier Tertiary formations

must have taken place.

It is therefore appropriate to consider the beds above the base of 

the Glycymeris zone as a distinct formation, although on Anticline 

Ridge and in the greater portion of their extent in the region north of 

Coalinga, as well as to the south as far as they have been studied, they 

appear to rest conformably upon the beds below. The fact that the 

Glycymeris zone or fossil beds that are approximately equivalent to it 

are traceable throughout the district gives it great value in distinguishing the Etchegoin from the formation below.

TOP OF THE FORMATION.

In the section of this formation in the hills north and northwest of 

Coalinga the summit has not been found clearly marked, but it is 

overlain around the edge of the valley by gravel, sand, and clay 

deposits that are with little doubt the equivalent of part of the forma.- 

tion which has at its base a clearly marked bed of fresh-water fossils 

at the northern end of the Kettleman Hills, less than 10 miles to the 

south. That formation, the Tulare, is widespread along the border 

of the Diablo Range in contact with the Etchegoin. The occurrence 

of the Etchegoin, especially of the upper portion, is typical in the 

Kettleman Hills, and the contact is distinctly traceable between its 

uppermost beds, which are full of marine or estuarine fossils, and the 

fresh-water bed immediately overlying. There is reason to believe 

that if the beds of these formations were well exposed near their contact in the hills northeast of Coalinga the same fossil zone would be 

found and the summit of the Etchegoin would be well defined, as it is 

in the Kettleman Hills. An appearance of conformity and inter-- 

gradation between the Etchegoin and Tulare exists along the contact 

in the Kettleman Hills, although a time break may have intervened 

without leaving any marked evidence as yet observed. In the 

Kreyenhagen Hills there may be an unconformity, and that will, be 

discussed later.
116 COALINGA OIL DISTRICT, CALIFORNIA.

GENERAL DESCRIPTION.

In the description of the Jacalitos (early upper Miocene) frequent 

reference has been made to the overlying Etchegoin (uppermost Miocene). In fact, these formations are so closely related and so similar 

that, the one can not well be described without reference to the 

other. In the southern part of the district they seem to have 

originated as a chronologically continuous succession of deposits 

and are only arbitrarily separable on the basis of the associations of 

faunas, whereas in the northern part of the district they are not so 

completely represented, and movement of the land took place that 

caused the later deposits to spread more widely than those of the 

earlier period. Many of the features of structure, influence upon 

topography, and lithologic variation mentioned in connection with 

the Jacalitos are common to both.

The surface exposure of the upturned beds of the Etchegoin 

formation, as shown by the map, forms a belt along the foothills 

similar to that of the Jacalitos, the beds lying above those of the 

Jacalitos in the general monoclinal succession. Along the main 

belt where the beds of the Etchegoin lie they dip at all angles, varying 

from a few. degrees to the vertical, but generally with regularity at 

each locality. The formation attains its greatest thickness in the 

southern part of the district, in the Kreyenhagen Hills, where it is 

at least 3,500 feet thick. In the northern portion it is at most only 

half as thick.

The formation is made noticeable by the dominant grayish-blue 

color of the massive sand beds that are dispersed through several 

hundred feet of beds at its base, but an examination of its characteristic fossils, which abound at several different horizons, is the only 

means of distinguishing it accurately from the associated formations. 

The blue color of the sands has been mentioned above (p. 115). An 

exposure of soft sandstone and gravel beds in the middle of the 

formation is shown in Plate IX, B. The outcrops and general 

topography at the point where this picture was taken are characteristic, although the sand dollars are somewhat more numerous than 

in most places. t

One of the most important of the broad features of the formation in 

the Coalinga district is the usual predominance, of coarse material, 

such as sand and pebbly deposits, in its lower portion, and of finer 

material, such as extremely fine sand and clay, in its upper portion, 

but this feature is characteristic in various degrees according to the 

locality, and in some places is hardly noticeable. It can not be said 

of any locality that either portion is free from an admixture of the 

elements of the other, and, moreover, the uppermost beds of the 

formation are in large part composed of sand and sandstone wherever 

they have been found exposed.
ETCHEGOIN FORMATION. 117

F. M.. Anderson divided his Etchegoin series into the Etchegoin 

sands below and the San Joaquin clays above, corresponding to the 

rough divisions already outlined; but inasmuch as these names are 

not applicable throughout the area under discussion and do not 

represent a complete division of the formation they are not used in the 

present paper.

DISTRIBUTION AND LOCAL CHARACTER.

ETCHEGOIN IN THE COALING A FIELD.

In the oil field-north of Coalinga the Etchegoin has a maximum 

thickness of about 1,700 feet. The Glycymeris zone already described 

is at the base and a number of other fossiliferous beds lie within 

several hundred feet above this, affording altogether a rich fauna. 

(See fossil localities 4657, 4671, and 4688.) The lower portion of 

the formation is composed largely of beds of compact coarse and 

fine bluish-gray sand alternating with zones of pebbly sand, fine 

gray sand, and some clay, with occasional more hardened beds. 

The clay increases toward the upper part of the formation, being 

interbedded with unconsolidated light-gray sand that spreads over 

the surf ace,and obscures the structure. The formation occurs in the 

low hills bordering the valley and passes beneath the alluvium of 

the floor.

The Etchegoin forms a belt along the edge of the Alcalde Hills 

west of Coalinga and is overlapped by the recent valley deposits. 

The formation is described in connection with the section (fig. 4), 

which represents its exposures on the summit and east slope of the 

1,410-foot hill 2 miles southwest of Coalinga. The beds there are 

chiefly of yellowish and gray gypsiferous sand, sandstone, and 

gravel of various degrees of coarseness, and have an exposed thickness 

of about 750 feet. A fossil bed about equivalent to the Glycymens 

zone at the base of the formation farther northeast outcrops near 

the top of the hill, and a 20-foot fossil bed equivalent to the Pecten 

coalingaensis zone of the Kreyenhagen and Kettleman hills appears 

at the edge of the valley about 650 feet above the base of the formation as mapped (fossil locality 4714). As the uppermost beds that 

belong above the Pecten coalingaensis zone are hidden by the surface 

deposits of the valley, the whole formation here may have a thickness 

of 900 or 1,000 feet. Probably the formation is overlain beneath the 

valley by the Tulare.

ETCHEGOIN IN THE WHITE CHEEK BASIN.

A detached area of Etchegoin beds is preserved in the syncline 

near the head of White Creek, as before mentioned. At one time these 

beds were doubtless continuous with those of the same formation 

around Pleasant Valley. The lowest 100 feet of beds, immediately 

overlying the Cretaceous, are composed of coarse and pebbly, compact
118 COALINGA OIL DISTRICT, CALIFORNIA.

but soft yellowish-gray sandstone hardly distinguishable from the 

underlying Cretaceous sandstone. These beds do not contain very 

many fossils, but grade upward into beds largely composed of fossils, 

with a matrix of yellowish-gray sand. This basal fossil zone contains 

a fauna closely resembling that of the Glycymeris zone ,on Anticline 

Ridge and is correlated with it. (See fossil localities 4662, 4663, and 

4664.) The bulk of the formation in its middle portion consists of 

similar sand and sandstone resembling the massive upper Cretaceous 

sandstone and containing occasional fossil beds. Numerous layers of 

very hard sandstone and some concretions are present. The beds for a 

few hundred feet below the top of the formation are more variable, a 

thick zone of coarse pebbles being followed above by alternating 

beds of sandy shale, calcareous shale, and coarse and fine sand and 

sandstone, with a hard and prominent thin bed of dark-brownish 

sandstone full of small white fossils near the top. The total thickness 

of the beds here preserved is about 1,100 feet.

The basal beds of the Etchegoin are apparently conformable in dip 

with the Cretaceous in the White Creek syncline, although of course 

the break between the two periods was profound. The beds at the 

base dip at angles as high as 60° or more along parts of the syncline, 

but the dip decreases gradually to only a few degrees in the axis of 

the fold. The character of the sand forming the Etchegoin beds 

indicates that it was derived largely from the Upper Cretaceous 

sandstone beds.

ETCHEGOIN IN WALTHAM VALLEY.

The continuation of this basin deposit of Etchegoin forms a filling 

in the region of open hills toward the head of Los Gatos Creek, 

where it overlies both Cretaceous and Franciscan, and in the synclinal 

trough of Waltham Valley, which extends for many miles along the 

western side of Juniper Ridge outside of the area mapped.

ETCHEGOIN IN THE KREYENHAGEN HILLS.

The best and most complete sections of the Etchegoin may be 

found in the Kreyenhagen Hills, where the upturned northeastwarddipping beds of this formation are exposed as a belt between the 

Jacalitos and Tulare formations. It is not easily separable from 

these two formations. -The contact at the base of the Etchegoin is 

drawn below a fairly constant fossiliferous zone, which is supposed 

to be the equivalent of the Glycymeris zone north of Coalinga. 

The contact at the top. of the formation is marked by the usual occurrence above it of the gravelly beds of the Tulare, by a summit zone 

containing My as, oysters, etc., that may be called the upper Mya zone, 

and by other more local criteria.

The'zone of blue-sand beds at the base of the formation is constant 

throughout the Kreyenhagen Hills. Its thickness varies from place
ETCHECOIN FORMATION, .119

to place and its position is of little value except for rough correlations. 

The thickness of the blue-sand zone within the Etchegoin near Zapato 

Creek is over 2,500 feet, whereas at points south of Big Tar Canyon 

the beds characterized by this blue color have not been observed to 

extend as much as 800 feet above the base of the formation. The 

lower part of the formation is composed chiefly of sandy beds of all 

degrees of coarseness up to pebble beds, and of many varieties of blue, 

gray, and drab color, with minor amounts of clay. The upper part of 

the formation is composed of alternating thick zones of sand and clay, 

the clay being somewhat more in evidence than in the lower portion.

There are four main fossil zones in the Etchegoin of the Kreyenhagen Hills, corresponding to similar ones found in some other parts 

of the district. The lowest one is at the base of the formation and is 

the approximate equivalent of the Glycymeris zone farther north and 

of the lower Mulinia zone of the Kettleman Hills. About 800 feet 

above the base of the formation, roughly speaking, comes a zone that 

may be referred to here and in the Kettleman Hills as the upper 

Mulinia zone', as it is the uppermost bed in which large specimens of 

this genus are found. This zone is usually approximately coincident 

with the upper portion of the blue-sand zone. The third main zone 

may be called the Pecten coalingaensis zone owing to the nonoccurrence of this species at other horizons. It is within 300 to 400 feet 

below the top of the formation and contains a well-preserved and 

extremely varied fauna, including Pecten coalingaensis and Pecten 

wattsi as about the most typical forms, together with many sand 

dollars, sea urchins, brachiopods, etc. The fourth zone includes the 

summit beds of the formation, which contain My as, oysters, etc., and 

which are called the upper Mya zone. These four zones do not include 

all the important fossil beds in the formation, but are those that have 

been found most persistent and easily recognizable and therefore 

most valuable as datum zones.

The following sections of the formation in different parts of the 

Kreyenhagen Hills, together with the section in figure 4, give a tabulated description of the formation as it occurs typically and convey 

an idea of the variety of the beds.

Section of Etchegoin formation on Canoas Creek.

Fine gray sand and clay, with occasional hard layers, upper Mya zone (fossil 

localities 4744 and 4782); overlain by gravel of Tulare..................... ^ 450

Gray sand and clay in alternating beds of variable thickness.................. 1, 700

Top of blue sandstone; massive gray sand, both coarse and fine, interbedded 

with clay in lesser amounts and occasional heavy beds of blue.sand; contains 

numerous sand dollars (locality 4707) and a zone at the base with many 

fossils; the upper Mulinia zone........................................... 550

Similar beds to the base of the zone of blue sand. Beds at base containing many 

fossils (locality 4769), probable equivalent of the Glycymeris zone and of lower ' 

Mulinia zone of Kettleman Hills.......................................... 900

3,600
120 COALINGA OIL DISTRICT, CALIFORNIA.

Section of Etchegoin formation 8% miles southeast of Big Tar Canyon.

Feet.

Thinly bedded hard white porcelaneous shale, with whitish-gray fine sand, 

pebbly sand, and sandy clay, containing lenticular layers and nodules of porcelaneous shale and many bone fragments; summit of Etchegoin not defi-. 

nitely determinable, but this zone so mapped............................. 250

Alternating thick zones of whitish-gray sand and clay......................... 1,080

Solid zone of thin-bedded pebbly sandstone.................................. 45

Whitish-gray sand and clay with a 15-foot bed of coarse pebbly sand in middle.. 660 

Prominent beds of compact gray sand with softer sand and sandy clay between; 

whiiish-gray sand with black pebbles at base............................... 210

Compact fine gray sand streaked with layers of fine whitish sand and sandy clay. 420 

Compact, slightly gritty white shale somewhat similar to Santa Margarita (?)..-- 10 

Solid zone of gray sandstone, coarse pebbly sandstone, and hard calcareous shale. 40 

Fine gray sand............................................................ 50

Highest bed of blue sand, with a 10-foot layer of pebbles at base and a 3-foot layer 

full of sand dollars, barnacles, Areas, etc., 20 feet above base; probably upper 

Mulinia zone........................................................... 80

Interbedded blue sand and sandy clay with a prominent 20-foot bed of blue 

sand at base............................................................. 120

Minor beds of blue sand, with a thick zone of hard calcareous shale in middle... 90 

Prominent blue-sand bed, pebbly toward the base and containing many sand 

dollars..................................................................

Soft gray sand............... 1...............................................

Very prominent blue sand..................................................

A prominent 30-foot bed-of blue sand at base overlain by bluish and gray sand 

and three less prominent beds of blue sand................................ 250

3. 500

ETCHEGOIN IN' M'LURE VALLEY.

The Etchegoin probably outcrops over a small area in the Avenal 

syncline in McLure Valley above the Jacalitbs formation, but it can 

not be definitely recognized. The thickness of beds above the Santa 

Margarita(?) formation is-so great in this region that some Etchegoin 

must be present in addition to the Jacalitos. No fossils have been 

found and there is no direct evidence on which to base a separation 

between the two formations, so that the line of contact mapped is 

arbitrary. The highest beds appearing in the syncline, which are 

taken to be the basal beds of the Etchegoin, consist of blue sands. 

Above these everything is covered by the recent alluvial deposits of 

the valley.

ETCHEGOIN IN THE KETTLEMAN HILLS.

The Etchegoin is excellently exposed in the Kettleman Hills, where 

it is a thick formation similar in general character to the same terrane 

in other parts of the district. Its lower portion appears along the 

axis of the Coalinga anticline, but although the lowest beds that the 

plunging anticline brings to the surface are very nearly the basal beds 

of the formation no underlying formation is known to be exposed. 

The uppermost beds appear all around the Kettleman Hills and are 

everywhere overlain, with apparent conformity, by the fresh-water
ETCHEGOIN FOKMATION. 121

beds at the base of the Tulare. The greatest thickness that has been 

found exposed is in the south-central part of the hills, on the southwest flank of the anticline, where the beds below the fresh-water 

horizon measure over 3,000 feet.

Different horizons in the Etchegoin of the Kettleman Hills afford 

good datum lines that may be recognized by means of the characteristic faunas and the constancy of the beds containing them, and it is 

convenient to designate these briefly, beginning with the summit 

of the formation as a constant datum line and going .down. In addition to the main zones that will be here mentioned there occur other 

fossil beds which may assume local importance, but which were 

not found so constant., Complete lists of the fossils contained in 

these zones at different localities are given below. In this connection reference should be made to the section in figure 5 and the tabulated section on page 123. The summit of the formation is marked, as 

it is in portions of the Kreyenhagen Hills, by a constant fossiliferous 

zone of sand and sandstone interbedded with dark clay, which may 

be called here, like the same zone in the Kreyenhagen Hills, the 

upper My a zone, because of the great abundance of My as. It also 

contains many other fossils, especially common being small yellow 

Littorinas and small oysters. This zone has a thickness varying' 

between 200 and 300 feet and is prominent in the topography because it usually forms a line of hills. In the southern part of the 

Kettleman Hills it forms the main ridge. This zone and the transition between it and the overlying fresh-water beds is further discussed 

in connection with the Tulare formation. Below it comes a zone 

of unequal thickness, but usually about 700 feet thick, which in 

some portions of the hills is composed almost entirely of fine inkyblue clay, and in others of clay and sand interbedded in varying 

proportions. Toward the base of this zone, usually between 700 

and 900 feet below the top of the formation, there is a zone of fossiliferous sandstone beds that is the equivalent of the zone of Pecten 

coalingaensis in the Kreyenhagen Hills. These beds likewise show 

a tendency to form hills or knobs, but they are not as prominent as 

those of the upper Mya zone. Below the Pecten coalingaensis zone 

the formation is largely sand and clay, chiefly sand, down to the 

base, the lower portion being composed as elsewhere of alternating 

beds of ordinary sand and blue sand. The next prominent fossil 

bed to be mentioned is another one containing a great many Myas; 

and it will be referred to as the lower Mya bed. ~ It occurs between 

very prominent beds of blue sand on the summits of hills, and in the 

north-central portion of the Kettleman Hills forms the main ridge. 

Owing to the fact that the formation is thicker in the southern than 

in the northern portion of the hills and apparently thicker on the 

western than on the eastern flank of the anticline, the distance below
Alluviu

Sea- level

FIGURE 5. Section of Tulare and Etchegoin formations along road 6 miles from northwest end of Kettlem

 ' on geologic map (PI. I).

a. Alluvium.

Tulare.

Feet.

b. No good outcrops but probably alternating sand, coarse gravel, and clay;

highest Tulare exposed .................................................. 700+

c. Chiefly light-gray sand affording a light sandy soil, interbedded with strawcolored earthy clay, and with occasional beds of gravel and thin layers of 

hard sandstone.......................................................... 700

d. Gypsiferous dark clay, with thin beds of sand............................. 160

e. Incoherent gray sand and clay, with fresh-water fossils in lower portion; base

of Tulare................................................................ 260

Etchegoin.

1,820+

/. Yellowish-gray sand and clay, with some dark clay; many fragmentsof porcelain shale on surface, small oysters in sand at top, and yellow calcareous . 

shale lenses in bluish-black clay at base; upper Mya zone, top of Etchegoin. 125

g. Alternating beds of gypsiferous fine drab sand, sandy clay, and drab to 

bluish clay, with occasional sandstone layers, and with bed at base containing delicate fossils, Nucula, etc.. ..........1.......................... 250

ft. Similar beds, with layers of iron-stained sandstone at base ................ 115

i. Similar gypsife

Pecten coaling

j. Inky-blue clay w

limestone in m

k. Fine sand and s

and variegated 

sandstone with 

I. Highest blue-sa

m. Grayish-blue m

n. Thinly and ma

beds of blue s

the sand at b

o. Massive beds o

Mulinia zon

p. Less prominent 

nius, Ostrea, C

Total Tular

The base of the 
ETCHEGOltf FO&MATIOtf.

the summit of the formation at which this and other beds occur 

can not be stated as a constant. The variation of this zone is 

between about 1,900 and 2,400 feet below the summit. One of the 

fossils most in evidence in the Kettleman Hills is the large Mulinia, and a bed containing abundant specimens of this form 

lies about 100 feet below the lower My a bed. It marks the highest 

horizon at which the large specimens have been found and is, as far 

as can be told, the equivalent of the upper Mulinia zone in the 

Kreyenhagen Hills. In the northern portion of the Kettleman 

Hills it is near the base of the exposed series and is the lowermost 

easily recognizable zone, whereas in the central portion of the hills 

beds of considerable thickness' are exposed below. Inasmuch as the 

base of the Etchegoin can not be mapped in these hills the upper 

Mulinia bed is taken as a datum line in the lower portion of the 

formation and its summit is mapped. It can not be definitely

traced at all points along the line mapped, but its horizon has 

been approximated as nearly as possible where its fossils and those 

of the overlying lower Mya bed have not been found. Another 

zone in the Kettleman Hills in which Mulinia is very abundant is 

between 500 and 700 feet below the upper one, and may be referred 

to as the lower Mulinia zone. It is approximately the equivalent of 

the Glycymeris zone in the Coalinga field. It is about the lowest bed 

exposed and is approximately the base of the Etchegoin formation.

The following tabulated section and the section in figure 5 represent the lithologic character and variations of the Etchegoin in the 

Kettleman Hills. Variation is the rule and it would be difficult to 

find any two sections in which the same beds are exposed and the 

characteristics are constant. On the northeast flank of the anticline the. beds are repeated with approximately the same thickness, 

but the sections measured made it appear that there was possibly 

a slight thinning on that side.

The following section is on the southwest flank of the anticline 

in the south-central portion of the hills, beginning at the 1,030- 

foot hill on the main ridge 5 miles northwest of the 'Dudley-Lemoore 

road (in the center of sec. 3, T. 23 S., R. 18 E.), and extending northeastward across the strike of the beds to the anticlinal axis.

Section of Etchegoin formation on southwest flank of Coalinga anticline in central portion

of Kettleman Hills.

Feet. 

Inky-blue clay below fresh-water bed ...................................... 50

Yellow and gray sand full of fossils and of fragments or nodules of porcelain 

shale; the upper Mya zone (fossil locality 4730)........................... 200

Inky-blue clay zone; sandy beds at top containing innumerable small oysters; 

occasional layers of yellow calcareous shale; a thin bed, 15 feet above base, of 

coarse purple and yellow, iron-stained, and exceedingly gypsiferoua sandstone with many fossils (locality 4693), probably the Pecten coalingaensis zone. 725
124 COALINGA OIL DISTRICT, CALIFOKNIA.

Feet.

Mostly light-gray and drab sand, with beds of dark clay in minor amount; a 

pebbly sand layer 200 feet below top; pebbly sand and iron-hardened sandstone layers near base......................................................... 1, 400

Blue-sand zone, several massive beds of blue sand and pebbly sand interbedded 

with fine light-gray and drab sand, sandy shale, and pebbly sand and occasional iron-hardened beds; at top is probably the upper Mulinia zone; the 

basal sand is full of fossils and is the lower Mulinia zone (locality 4689)..... 675

3,050

The upper Mulinia zone occurs 2,000 feet below the summit of the 

Etchegoin in the section in figure 5, whereas the bed that has been 

correlated with it in the above tabulated section occurs over 300 

feet lower. It seems probable from this and similar instances in the 

case of other sections that there is a thickening of the formation 

toward the south between the top and this bed, similar to the thickening that takes place between the oil field north of Coalinga and the 

Kreyenhagen Hills. It may reasonably be assumed that a thickening 

takes place below the upper Mulinia zone as well, and that the base 

of the formation is not as far below this zone in the northern portion 

of the hills as farther south.

Toward the north end of the hills, as shown by the map, the Etchegoin plunges completely beneath the Tulare formation and does not 

appear again until brought up by the oppositely plunging anticline 

on Anticline Ridge. Toward the southern end of the hills the formation becomes covered more and more by surface sand and soil, and 

its zones and structure are obscured. At the south end of the hills 

it does not pass below the Tulare, but exposes its lower beds.

FOSSILS, ORIGIN, AND AGE.

FOSSILS.

Fossils are found more or less abundantly and usually in an excellent state of preservation throughout the Etchegoin formation in the 

Coalinga district. Several recognizable zones, each carrying a more 

or less distinctive fauna, occur between the base and top of the formation, but these faunas are closely related and have not been 

deemed worthy of recognition in the mapping. The following species 

have been found by the writers in and near the district under 

discussior 
Fossils from the Etchegoin formation (uppermost Miocene), 

Name.

ANTHOZOA.

ECHINODERMATA.

BRACHIOPODA.

Terebratalia occidentalis Dall . ..............

PELECYPODA.

Area trilineata Conrad ......................

Area sp. a. .................................

Cardium coosense Dall ......................

Cardium meekianum Gabb. ................

Cardium sp. indet ..........................

Chama peuucida Broderip ..................

-Clidiopnora punctata Conrad ............. .

Cryptomya quadrata Arnold ................

Cumingia californica Conrad .............

Diplodonta harfordi F. M. Anderson ........

Diplodonta parilis Conrad ..................

Glycymeris coalingensis Arnold ..........

Glycymeris septentrionalis Middendorf . . .

Macoma inquinata Deshayes. . ...........

Metis sp. indet. . .........................

Modiolusrectus Conrad .....................

Mulinia densata Conrad. ....................

Mya japonica Jay ........................

Mytilus (Mvtiloconcha) coalingensis Arnold .

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PELECYPODA continued.

Ostrea atwoodi Gabb .......................

Ostrea lurida Carpenter .....................

Ostrea vespertina Conrad var. sequens

Panopea generosa Gould ....................

Paphiastaleyi? Gabb. ......................

Paphia truncata? Gabb. ....................

Pecten nutteri Arnold ......................

Pecten wattsi Arnold .......................

Pecten wattsi Arnold var. etchegoini F. M.

Pholadidea ovoidea Gould ..................

Placunanomia californica Arnold. ...........

Schizothserus pajaroanus Conrad ............

Siliqua sp. indet ............................

Solen sicarius Gould ........................

Solen sp. indet. . ...................... I .....

Transennella californica Arnold .............

GASTEROPODA.

Astyris richthofeni Gabb ....................

Bathytoma carpenteriana Gabb var. fernandoana Arnold ............................

Calliostoma coalingensis Arnold .............

Calliostoma kerri Arnold ....................

Cancellaria tritonidea Gabb .................

Chrvsodomus imperialis Dall ...............

Chrysodomus portolaensis Arnold ...........

Crepidula princeps Conrad ..................

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Gpniobasis kettlemanensis Arnold..........

Littorina mariana Arnold and var. alta

Arnold...................................

Lunatia lewisii Gould.......................

Margarita sp................................

Nassa californiana Conrad...................

Nassa californiana Conrad var. coalingensis

Arnold...................................

Natica? ....................................

Neverita recluziana Petit...................

Neverita recluziana Petit var. alta Ball.....

Olivella biplicata Conrad...................

Olivella pedroana Conrad ...................

Opalia sp. indet............................

Pisania fortis Carpenter var. angulata Arnold. 

Pleurotoma coalingensis Arnold.......:.....

Sigaretus scopulosus Conrad................

Thais crispatus Chemnitz...................

Thais crispatus Chemnitz.nearlysmooth var. 

Thais etchegoinensis Arnold................

Thais kettlemanensis Arnold ..... ^. ........

Trochita fllosa Gabb........................

Trophon (Forreria) coalingense Arnold. 

Trophon (Forreria) ponderosum Gabb. 

Trophon (Boreotropnon) stuarti Smith......

Turritella vanvlecki Arnold.................

Xylotrya sp................................

CIBRIPEDIA.

Balanus sp.......................

Balanus large sp.................

Balanus concavus Bronn.........

Tamiosoma gregaria? Conrad.....

CRUSTACEA.

Cancer fissus Rathbun...........

Loxorhynchus grandis Stunpson.

PISCES.

Fish bones of various kinds......

Carcharodon arnoldi Jordan......

Fish, bulbous growths...........

Fish spines......................

Fish vertebra?...................

CETACEA.

Cetaceae (ven >,).
Fossils from the Etchegoin formation (uppermost Miocene), Coa

Name.

ANTHOZOA.

ECHINODERMATA.

BRACHIOPODA.

Terebratalia smith! Arnold. .................

PELECYPODA.

Area sp. a. ...... ...........................

Cryptomya ovalis Conrad ...................

Cryptomya guadrata Arnold ................

Diplodonta harfordi F. M. Anderson. .......

Diplodonta parilis Conrad. ..................

Glycvmeris coalingensis Arnold .............

Glycymeris septentrionalis Middendorf.. . . . .

Macoma secta Conrad .......................

Mactra albaria Conrad.................... ...

Mactra coalingensis Arnold.. . ...............

Modiolus directus Ball .... .................

Modiolus rectus Conrad .....................

Mvtilus (Mytiloconcha) coalingensis Arnold.

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ETCHEGOIN FORMATION. 129

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Margarita sp............. Nassa califomiana Conrad Nassa califomiana Conrac

Arnold ................ Natica?..................
Fossils from the Etchegoin formation (uppermost Miocene), Coal

Name.

GASTEROPODA continued.

Pisania fortis Carpenter var. angulata Arnold .

Thais crispatus Chemnitz, nearly smooth var.

CIRRIPEDIA.

CRUSTACEA.

PISCES.

Fish spines. .................................

CETACEA.

Cetaceae (vertebrae) .........................

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Name.

ANTHOZOA.

ECHINODERMATA.

BBACHIOPODA.

PELECTPODA.

Mvtilus (Mvtiloconcha) coalingensis Arnold.

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Name.

PELECYPODA continued.

Ostrea vespertina Conrad...... .............

Ostrea vespertina Conrad var. sequens 

Arnold ...................................

Paphia staleyi Gabb..... . ...................

Paphia truncata? Gabb. . ...................

Pecten nutteri Arnold. .......................

Pecten wattsi Arnold var. etchegoini F. M.

Pholadidea ovoidea Gould. .................

GASTEEOPODA.

Bathytomacarpenteriana Gabb var.fernanCalliostoma coalingensis Arnold. ............

Calliostoma kerri Arnold .................. .

Chrysodomus imperialis Dall. . ..............

Chrysodomus portolaensis Arnold. ..........

Crepidula princeps Conrad.. . ...............

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Nassa californiana Conrad var. coalingensis

Natica? .....................................

Pisania fortisCarpenter var. angulata Arnold .

Thais crispatus Chemnitz, nearly smooth var.

CIREIPEDIA.

Balanus sp .................................

Balanus concavus Bronn ...................

Tamiosoma gregaria? Conrad ................

CRUSTACEA.

PISCES.

Fish bones of various kinds .................

Fish spines. .................................

CETACEA.

Cetacese (vertebrse) .........................

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134 COALINGA OIL DISTRICT, CALIFORNIA.

3849. Point where road from Coalinga to Stone Canyon crosses the Waltham Creek sheep property. Spur 

of sandstone. Middle beds.

4643. Upper Mulinia zone on main ridge of Kettleman Hills 1 mile southeast of 1,370-foot hill, in the SE. i 

sec. 20, T, 22 S., R. 18 E. Lower middle beds.

4048. Seventy-five feet below summit on south side of 1,375-foot hill just west of Mr. Orr's house in Big 

Tar Canyon, in the NE. J NW. J sec. 8, T. 23 S., R. 17 E. Basal beds.

4656. At northwest end of Anticline Ridge, 6 miles north-northeast of Coalinga, SW. J sec. 34, T. 19 S., 

R. 15 E. Lowest Etchegoin bed or Glycymeris zone, just below bed of 4657.

4657. At northwest end of Anticline Ridge, 6 miles north-northeast of Coalinga; bed just above 4656; near 

south side of SW.i sec. 34, T. 19 S., R. 15 E. Basal beds.

4658. Near north west end of Anticline Ridge, at southeast end of long 1,200-foot hill, in NE. i sec. 3, T. 20 

S., R. 15 E. Near base of Etchegoin.

4659. At northwest end of Anticline Ridge on 1,200-foot hill and for 1 mile northwest of that hill along 

Glycymeris zone. Basal beds. See 4656.

4660. About 2$ miles southwest of Coalinga, northeast of West Coalinga well. Glycymeris zone or basal 

beds. See locality 4674.

4661. Eightmiles north of Coalinga, in the NW. J sec. 29, T. 19 S., R. 15 E. Glycymeris zone or basal beds.

4662. At north edge of Etchegoin area in White Creek basin, one-half mile east of road up White Creek and 

three-fourths mile southeast of Michigan well, center of NW. £ sec. 16, T. 19 S., R. 13 E. Glycymeris 

zone, 100 feet above base of Etchegoin.

4663. At north edge of Etchegoin area in White Creek basin, on summit of ridge one-half mile west of road 

up White Creek and three-fourths mile southwest of Michigan well, about 1 mile northwest of 4662. In basal 

sandstone of the Etchegoin.

4664. On north side of White Creek about 5 miles northwest of junction with Los Gatos Creek. In basal 

Etchegoin beds on south side of synclinal basin.

4665. On south side of White Creek about 6 miles northwest of junction with Los Gatos Creek. Basal 

beds.

4669. At south end of Kettleman Hills, on summit of 540-foot hill in the very southwest corner of area 

mapped, in center of sec. 2, T. 25 S., R. 19 E., and for 1 mile S. 15° E. of that hill. Probably about the 

lowest Etchegoin beds exposed south of Avenal Gap.

4670. At southernmost end of Kettleman Hills, 5i miles south-southeast of Light's house in Avenal Gap, 

on knob of vertical angle B. M. (elevation 505 feet), in center of sec. 10, T. 25 S., R. 19 E. Prominent bed 

of yellowish limestone in uppermost portion of Etchegoin. ' . 4671. On northeast flank of Anticline Ridge, about 6£ miles northeast of Coalinga and about 2 miles northnortheast of B. M. 947 feet. Several hundred feet above base of Etchegoin, in the lower middle beds.

4672. South of Waltham Creek, 3J miles southwest of Coalinga, on northeast nose of 1,200-foot ridge fourfifths mile north-northwest of 1,900-foot hill, center of SE.i sec. 13, T.21S.,R. 14 E. Basal beds.

4673. One mile southeast of Alcalde, atelevation of 1,600 feet on ridge west of 1,900-foot hill, center of NE. J 

sec. 24, T. 21 S., R. 14 E. Basal beds.

4674. Halfway between West Coalinga and Commercial Petroleum wells, about 3 miles southwest of 

Coalinga. Glycymeris zone or basal beds. See locality 4660.

4675. About 2| miles due west of Coalinga, at elevation of about 1,200 feet on road, north line of sec. 1, T. 21 

S., R. 14 E. Lower middle beds. '

4676. Six miles southeast of northwest end of Kettleman Hills, where old road crosses main ridge one-half 

mile east of 1,332-foot hill. Lower Mya zone, or lower middle beds.

4677. Ten miles southeast of northwest end of Kettleman Hills, on northeast side of summit of 1,370-foot 

hill, west side of NW. i sec. 20, T. 22 S., R. 18 E. Lower Mya zone, or lower middle beds.

4678. On road north of locality 4676, one-half mile east-northeast of 1,332-foot hill. Lower middle beds.

4679. Area about 10 to 12 miles southeast of northwestend of Kettleman Hills; Mulinia beds on both sides 

of anticline, between 1,370-foot and 1,277-foot hills on main ridge and within 1 mile northeast of those hills 

on opposite side of anticline. Lower middle and basal beds.

4681. On east side of Kettleman Hills 3 miles northeast of Light's place in Avenal Gap, on southwest side 

of long, low ridge near axis of anticline, middle of west side of NE. i sec. 4, T. 24 S., R. 19 E. Upper (?) 

Mulinia zone, or lower middle beds.

4682. One-third mile west of locality 4681, north-central part of NW. \ sec. 4, T. 24 S., R. 19 E. Upper 

Mulinia zone, or lower middle beds.

4683. South of Avenal Gap in Kettleman Hills; extremely fossiliferous sand on summit of 500-foot knob

just north of old house, 2| miles S. 45° E. of Light's place; northern part of NW. i sec. 27, T. 24 S., R. 19 E.

Upper Mulinia zone, or lower middle beds.

4684. South-central part of Kettleman Hills, about 5 miles northwest of Dudley-Lemoore road, in second 

main canyon 1J miles N. 45° E. of 1,030-foot hill, center of SW. \ sec. 35, T. 22 S., R. 18 E. Lower Mulinia 

zone, about 3,000 feet below top of Etchegoin; lower middle or basal beds.

4688. On Anticline Ridge, southwest of Turner well No. 2, middle of S. £ sec. 2,.T. 20 S., R. 15 E. 

Several hundred feet above base of Etchegoin, in the lower middle beds.

4690. Two miles southwest of Coalinga.sputh of Lucile well, S W. i sec. 6. Lower middle beds.

4693. South-central part of Kettleman Hills, about 9 miles northwest of Avenal Gap, 1,000 feet northeast 

of 1,030-foot hill, S W. J NE. i sec. 3, T. 23 S., R. 18 E.; 950 feet stratigraphically below summit of Etchegoin. 

About the same as Pecten coalingaensis zone, or upper middle beds.

4695. East side of Kettleman Hills south of Avenal Gap, from gravelly surface of ground, NE. J SE. J 

. sec. 27, T. 24 S., R. 19 E. Lower middle beds.

4696. About 2,000 feet east of main ridge of Kettleman Hills, 1 mile southeast of Light's place, S W. | N W. J 

sec. 21, T. 24 S., R. 19 E. In dark gypsiferous sand and clay about 750 feet stratigraphically below top 

of Etchegoin; probably the equivalent of the Pecten coalingaensis zone, or upper middle beds.

4697. Near south end of Kettleman Hills, along summit of ridge (elevation 592 feet) 4 miles S. about 20° 

E. of Light's place in Avenal Gap, on west side of sec. 3, T. 25 S., R. 19 E. Prominent pebble bed 1,600 to 

2,000 feet below summit of Etchegoin. Probably same horizon as 4695, in lower middle beds.

4698. North of White Creek syncline, about three-fourths mile north of White Creek and 3J miles northwest of junction with Los Gatos Creek, in center of sec. 23, T. 19 S., R. 13 E. Upper middle beds.

4699. Eastern border of southernmost group of Kettleman Hills, in gray and blue sand on northeastern 

side of knoll in western part of sec. 26, T. 24 S., R. 19 E. About same horizon as 4695 and 4697, in lower 

middle beds.

4700. Kettleman Hills. Float. Undiflerentiated lower or middle beds.

4701. East side of Kettleman Hills, at base of upper Mya zone or uppermost beds on Dudley-Lemoore 

road, in east-central part of sec. 17, T. 23 S., R. 19 E.

4702. South-central part of Kettleman Hills, on northwest side of 813-foot hill 4^ miles northwest of 

Avenal Gap, 400 feet east of main ridge where old road crosses, NW. £ NW ^ sec. 25, T. 23 S., R. 18 E. 

Gypsiferous sand and pebble bed about 900 feet stratigraphically below summit of Etchegoin. Probably 

equivalent to Pecten coalingaensis zone, or upper middle beds.
ETCHEGOLN FORMATION. 135

4703. Central part of Kettleman Hills, 10 miles northwest of Avenal Gap, three-fourths mile N. 30° W. 

of 1,030-fpot hill, SW. £ SW * sec. 34, T. 22 S., R. 18 E. About 900 feet stratigraphically below summit of 

Etchegoin. Probably equivalent of Pecten coalingaensis zone, or upper middle beds.

4704. Central part of Kettleman Hills, 11 miles northwest of Avenal Gap, on south base of 1,145-foot 

hill, in the very southeast corner of sec. 28, T. 22 S., R. 18 E. Just above upper Mulinia zone, in lower 

middle beds.

4705. One-third mile south of B. M. 923 feet on Zapato Creek, from hard layers in sand forming a ridge 

that runs along 1 mile from there on south side of road to Canoas Creek, on west side of NW. J sec. 17, T. 

22 S., R. 16 E. About 450 feet below summit of Etchegoin. Pecten coalingaensis zone, or upper middle 

beds.

4700. Just across the gully east of the Call well, 7 miles north-northwest from Coalinga, in the northwest 

corner of sec. 32, T. 19 S., R. 15 E. Lower middle beds (?).

4707. About one-fourth mile northeast of Hugo Kreyenhagen's house, between two roads that run east 

from Canoas Creek, center of sec. 27, T. 22 S., R. 16 E. Sea-urchin bed immediately above upper Mulinia 

zone, about 900 feet stratigraphically above base of Etchegoin, in lower middle beds.

4708. 1,245-foot hill 4 miles southeast of northwest end of Kettleman Hills, east side of sec. 32, T. 21 S., 

R. 17 E. Area bed In upper Mya zone, or uppermost beds.

4709. East side of Kettleman Hills, on summit of ridge in center of SE. J sec. 6, T. 22 S., R. 18 E. Drab 

sand with hard sandstone layers, 750 to 800 feet stratigraphically below summit of Etchegoin. Pecten 

coalingaensis zone, or upper middle beds.

4710. Three-fourths of a mile northwest of Zapato Creek B. M. 806 feet, on north side of ravine, west-central 

part of NE. £ sec. 5, T. 22 S., R. 16 E. Pecten coalingaensis zone, or upper middle beds.

4711. West side of 1,245-foot hill 4 miles southeast of northwest end of Kettleman Hills, central part of 

sec. 32, T. 21 S., R. 17 E. Oyster bed 50 feet above Area bed of locality 4708. Upper Mya zone, or uppermost beds.

4712. East of Zapato Creek, one-half mile south of Adolph Kreyenhagen's house, SW. J SE. } sec. 8, T. 

22 S., R. 10 E. Variable pebbly sand, with many fossils. Pecten coalingaensis zone, or upper middle beds.

4713. About 5J miles southeast of northwest end of Kettleman Hills, on top of 1,332-foot hill in southcentral part of SCC. 3, T. 22 S., R. 17 E. Sand-dollar bed of drab sand overlying blue and gray sand of 

lower Mya zone, both being in the lower middle beds.

4714. Two miles southwest of Coalinga, at elevation of 900 feet, near edge of Alcalde Hills, on ridge 

descending east from prominent hill (elevation 1,410 feet), just east of center of SW. ± sec. G, T. 21 S., K. 

15 E. Coarse sand and pebble conglomerate about 650 feet stratigraphically above base of Etchegoin. 

Pecten coalingaensis zone, or upper middle beds.

4715. South end of Kettleman Hills, sec. 10, T. 25 S., R. 19 E. Upper middle and uppermost Etchegoin 

beds.

4710. Near northwest end of Kettleman Hills, 2 miles north-northwest of 1,245-foot hill, east of center of 

SW.i sec. 20, T. 21 S., R. 17 E. In sand just below flinty white shale bed that marks top of Etchegoin. 

Just below 4740. Upper Mya zone, or uppermost beds.

4717. Near northwest end of Kettleman Hills, 1J miles northwest of 1,245-foot hill, just east of old house, 

northwest corner of sec. 29, T. 21 S., R. 17 E. Area sand below white shale at top of Etchegoin, upper 

Mya zone, or uppermost beds.

4718. Main ridge of Kettleman Hills, 4 miles north of Dudley-Lemoore road, on summit of 1,020-foot 

hill, east side of sec. 11, T. 23 S., R. 18 E. Upper Mya zone, or uppermost beds.

4720. One mile due north of Light's place in Avenal Gap, on south side of hill (elevation 555 feet) in center 

of SW. J sec. 8, T. 24 S., R. 19 E. Very gypsiferous sand at base of upper Mya zone, or uppermost beds.

4722. Three-fourths mile southeast of Adolph Kreyenhagen's on Zapato Creek, northwest corner of sec. 

10, T. 22 S., R. 16 E. Upper Mya zone, or uppermost beds.

4723. South group of Kettleman Hills, on point of main ridge facing Avenal Gap one-half mile east-southeast of Light's place, south side of SE. | sec. 17, T. 24 S., R. 19 E. Upper Mya zone, or uppermost beds.

4724. Main ridge of south group of Kettleman Hills, 1 mile south of Avenal Gap, NW. J SE. £ sec. 20, 

T. 24 S., R. 19 E. Upper Mya zone, or uppermost beds.

4725. East side of Kettleman Hills, on 500-foot ridge at contact of Etchegoin and- Tulare north of sharp 

turn in Dudley-Lemoore road, southwest corner of sec. 8, T. 23 S., R. 19 E. Upper Mya zone, or uppermost beds.

4728. On northeast border of Kettleman Hills, on southwest flankof 900-foot hill just east of old road, 

in north part of sec. 35, T. 21 S., R. 17 E. Upper Mya zone at top of Etchegoin immediately underlying 

Tulare fresh-water beds of 4731.

4729. About 1J miles east of Garza Creek, just north of road, at west foot of hill (elevation 1,174 feet), 

southeast corner of NE. Jsec. 36, T.22 S., R. 16 E. Upper Jtfyazone, or uppermost beds.

4730. Central part of Kettleman Hills, on summit of 1,030-foot hill on main ridge 9J miles northwest of 

Light's place in Avenal Gap, center of sec. 3, T. 23 S., R. 18 E. Upper Mya zone, or uppermost beds.

4736. East side of Kettleman Hills, east of Dudley-Lemoore road, NE.JSW. Jsec. 17, T. 23 S., R. 19 E. 

Upper Mya zone just below fresh-water bed (Tulare) of locality 4737, uppermost beds. 

4741. In Kettleman Hills, 3$ miles north of Dudley-Lemoore road on little hill (elevation 600+ feet), 

northeast corner of sec. 12, T. 23 S., R. 18 E. In lower middle beds just above lower Mya zone.

4744. West of Canoas Creek, north of road leading to Zapato Creek, SW. } NW. J sec. 22, T. 22 S., R. 

16 E. Upper Mya zone, uppermost beds.

4749. On ridge east of Garza Creek, in NE. J sec. 1, T. 23 S., R. 16 E. Lower Mulinia zone, basal beds 

of Etchegoin.

4750. On ridge east of Garza Creek, about 1,200 feet stratigraphically above 4749, SW. J sec. 36, T. 22 S., 

R. 16 E. Lower middle beds.

4751. On ridge east of Garza Creek and Immediately west of road from Garza Creek to Big Tar Canyon, 

NW. J sec. 36, T. 22 S., R. 16 E. About 1,000 feet stratigraphically above 4750, or In upper middle beds.

4752. On ridge east of Garza Creek and immediately northeast of road connecting Garza Creek and Big 

Tar Canyon, NE. } sec. 36, T. 22 S., R. 16 E. Upper Mya zone, about 1,000 feet stratigraphically above 

4751, uppermost beds.

4753. On Waltham Creek 13 miles southwest of Coalinga, 200 yards north of Elmer Frame's house. In 

gray sandstone well up in Etchegoin formation, probably in middle beds.

4754. Waltham Creek, 13 miles southwest of Coalinga, three-fourths mile east of Elmer Frame's 

place. Gray sandstone 200 feet stratigraphically below 3849; probably in middle beds.

4755. About 4 miles south of Coalinga in Jacahtos Hills, SW. J sec.21, T. 21 S., R. 15 E. Undlflerentlated 

lower or middle beds.

4756. Vicinity of Henry Spring, 4 miles south-southwest of Coalinga, on east side of 1,900-foot hill, S W. J 

sec. 18, T. 21 S., R. 15 E. Lower middle or basal beds.

4757. Same locality, but 150 feet stratigraphically above 4756. Lower middle or basal beds.

4758. Samelocality, but490feetstratigrapnicallyabove4756. Upper middle beds.

4759. Same locality, but 500 to 900 feet stratigraphically above 4756. Upper middle beds.
136 COALINGA OIL DISTRICT, CALIFORNIA.

4760. On old road crossing north end of Kettleman Hills, three-fourths mile northeast of 1,332-foot hill, 

SE. i N W. J sec. 2, T. 22 S., R. 17 E. In lower middle beds 1,900 feet stratigraphically below summit of 

Etchegoin. About equivalent oflower Mya zone.

4761. On ridge one-half mile south of junction of Jacalitos and Salt creeks, southeast corner sec. 31, T. 

21 S., E. 15 E. Cardium bed at base of Etchegoin; about equivalent of Olycymeris zone; basal beds.

4762. Southwest of Coalinga district, in Waltham Valley, three-fourths mile east of Elmer Frame's house. 

Area and Mactra bed, probably basal beds.

4763. Southwest of Coalinga district, on Stone Canyon-Waltham Creek road just west of Waltham Valley. 

Probably middle beds.

4769. On east side of Canoas Creek just south of Hugo Kreyenhagtsn's home, northwest corner of SW. \ 

sec. 27, T. 22 S., R. 16 E. Probable equivalent of the Olycymeris zone, or lower Mulinia zone, at contact 

between Etchegoin and Jacalitos.

4778. About three-fourths mile east of Adolph Kreyenhagen's house on Zapato Creek, west side of sec. 9, 

T. 22 S., R. 16 E. Small Ostrea bed, about 100 feet stratigraphically below Mya bed at top of Etchegoin 

formation in upper Mya zone.

4780. One-fourth mile west of locality 4778. Area bed about 350 feet below summit of Etchegoin, in 

upper beds.

4781. Areas from north-central part of Kettleman Hills. Basal Mulinia beds.

4782. On southwest flank of high hill (elevation 1,458 feet) east oflower part of Canoas Creek, at elevation 

of l,200feet, SW. J SW. J sec. 23, T. 22 S., R. 16 E. Upper Mya zone, or uppermost beds.

4783. On the northwest bank of Canoas Creek, three-fourths mile below H. Kreyenhagen's, 16 miles 

southeast of Coalinga, northeast comer of SW. J sec. 22, T. 22 S., R. 16 E. In Ostrea bed 125 feet stratigraphically below the top of the Etchegoin formation, in uppermost beds.

4799. Coalinga district; exact locality unknown.

4806. Two miles southeast of Coalinga, on north side of Alcalde Canyon, center of SW. J sec. 7, T. 21 S., 

R. 15 E. Olycymeris zone, near base of E tchegoin.

4857. Extreme southeast end of Kettleman Hills , in sees. 11 and 12, T. 25 S. ,R. 19 E. Pecten oweni 

bed, probably lowest Etchegoin.

FAUNAL ZONES.

The lowest fossiliferous bed in the Etchegoin is in a zone in which 

Gflycymeris coalingensis Arnold and G. septentrionalis Middendorf are 

exceedingly abundant; this zone is called the Gflycymeris zone. Above 

this are beds in which Mulinia densata Conrad is very abundant; this 

is the upper Mulinia zone. Still higher in certain parts of the field 

Echinarachnius gibbsii Re'mond is very common, but other fossils rare, 

and this is sometimes called the Echinarachnius zone. A few hundred 

feet below the top of the Etchegoin is an exceedingly fossiliferous zone 

in which Pecten coalingaensis Arnold is a common species, and this is 

called the Pecten coalingaensis zone; above it and -practically at the 

top of the Etchegoin is the upper Mya zone, characterized by numerous Mya japonica Jay. In the Kettleman Hills is another zone between the Mulinia and Pecten coalingaensis zones, in which Myd 

japonica Jay is practically the only fossil; this is called the lower 

Mya zone.

The Glycymeris zone, or zone of the basal beds, is characterized by 

the two species of this genus previously mentioned, Diplddonta Jiarfordi F. M. Anderson, D. parilis Conrad, Cardium meekianum Gabb, 

and Pecten oweni Arnold. Locality 4806 is typical of this zone. The 

localities representative of this zone are Nos. 4648, 4656, 4657, 4658, 

4659, 4660, 4661, 4662, 4663, 4664, 4665, 4669, 4672, 4673, 4674, 

4679 (in part), 4684, 4749, 4756, 4757, 4761, 4762, 4769, 4781, 4806, 

and 4857.

The upper Mulinia zone, or zone of the lower middle beds, contains 

numerous Mulinia densata Conrad, Ostrea atwoodi Gabb, and Area 

trilineata Conrad. It is represented by the following localities: 

Nos. 4643, 4671, 4675, 4676, 4677, 4678, 4679 (in part), 4681, 4682, 

4683, 4688, 4690 (?), 4695,4697, 4699,4704, 4706 (?), 4707, 4713, 4741, 

4750, and 4760.
ETCHEGOIN FORMATION. 137

The Pecten coalingaensis zone, or zone of the upper middle beds, is 

characterized by Pecten coalingaensis Arnold, P. wattsi Arnold and its 

variety etchegoini F. M. Anderson, Terebratalia smithi Arnold, and 

Ostrea vespertina Conrad. Locality 4712 yields a fauna typical of 

this horizon. It is also represented by the following localities: Nos. 

4693, 4696, 4698, 4702, 4703, 4705, 4709, 4710, 4712, 4714, 4715 (in 

part), 4751, 4758, and 4759.

The upper Mya zone, or zone of the uppermost Etchegoin beds, 

carries Mya japonica Jay, I/ittorina mariana Arnold and its variety 

alta Arnold, Trochita filosa Gabb, and Solen sicarius Gould. Just; 

above the upper Mya zone is usually found a bed in which are 

numerous Ostrea vespertina Conrad var. sequens Arnold. This zone 

is represented at the following fossiliferous localities: Nos. 4670, 4701, 

4708, 4711, 4715 (in part), 4716, 4717, 4718, 4720, 4722, 4723, 4724, 

4725, 4728,4729, 4730, 4736, 4744, 4752, 4778, 4780, 4782, and 4783.

The following localities are undifferentiated: Nos. 3849, 4700, 4753, 

4754, 4755, 4763, and 4799.

ORIGIN OP THE ETCHEGOIN.

A study of the faunas of the various zones of the Etchegoin leads to 

some interesting conclusions concerning the physical conditions under 

which the strata were deposited at various times throughout the 

Etchegoin epoch, and also to some important correlations, not only 

with formations in other parts of the Coast Range but with horizons 

of the Tertiary of the Eastern States.

The abundance of Area in the Glycymeris and Mulinia zones leads 

to the conclusion that the water in which the lower part of the Etchegoin was laid down was somewhat warmer than that now prevalent 

on the Pacific coast at the latitude of Coalinga.

Following the deposition of the two lower zones came a period in 

which estuarine conditions prevailed over at least a part of the 

Coalinga shore line, for in the Kettleman Hills is a bed in which are to 

be found large numbers of Mya japonica Jay, a noted cold-water 

species preferring mud flats. This Mya bed in turn is followed by 

strata in which is a fauna having many characteristics in common 

with the fauna of the Gulf of California province, a province that has 

been subject to tropical conditions at least since the beginning of 

Miocene time. It is therefore reasonable to suppose that a subsidence 

and change of conditions to those favoring the immigration of warmerwater species took place some time after the deposition of the middle 

Etchegoin. These conditions were suddenly altered near the close 

of the Etchegoin epoch, as is indicated by the fauna of the upper Mya 

zone, which contains Mya japonica, Macoma inguinata, and Littorina mariana (closely allied to the northern L. grandis Midd.), 

species supposed to have been best suited to cold-water and possibly
,138 COALINGA OIL DISTRICT, CALIFORNIA.

estuarine conditions. It is a noteworthy fact in connection with 

this late Etchegoin cold-water invasion that it exterminated most of 

the species found in the subjacent beds, at least for the local Coalinga 

province, and that Ostrea vespertine/, Conrad, the only important 

species of the preceding fauna which persisted into the last part of the 

Etchegoin, was so adversely influenced by the new conditions that it 

became a.dwarf of its former self and took up new characteristics at 

least of varietal importance. The uppermost Etchegoin representative of the beautiful well-developed Ostrea vespertina is the dwarfed, 

thin variety sequens.

Other evidence showing the varying conditions which prevailed 

during the latter half of the Etchegoin is to be found in the occurrence within the formation of curious bulbous growths of fishes, such 

as are later mentioned as occurring associated with the fresh-water 

fossils in the basal Tulare. The lowest horizon at which they were 

found is at locality 4697, from 1,600 to 2,000 feet below the summit of 

the formation. These occur alone, with marine fossils, or with freshwater fossils. At one horizon about 900 feet below the summit of the 

Etchegoin, along the eastern foot of the main ridge in the southern 

portion of the Kettleman Hills, abundant specimens of Goniobasis, a 

fresh-water genus, were found in gypsiferous beds associated with the 

curious fish bones. This horizon is represented by locality 4696, and 

is about equivalent to that of Pecten coalingaensis. These bones and 

shells indicate that a close connection existed between areas of salt 

water and nearly if not entirely fresh water during much of the Etchegoin period, and that, especialty in the later portion of the period, conditions were on the verge of becoming such as existed during early 

Tulare time. The great thickness of inky-blue fine clay in the upper 

portion of the Etchegoin of the Kettleman Hills below the sands of the 

Upper Mya Zone is believed to have originated as fine delta deposits, 

possibly subaerially and above the reach of the tide.

The presence of enormous quantities of Echinarachnius, accompanied by no other fossils, in some of the middle or upper middle 

Etchegoin sands and of somewhat similar deposits in the upper Jacalitos indicates that at various periods throughout the upper Miocene 

extensive shallow sand flats prevailed along the edge of the San 

Joaquin sea.

CORRELATION AND AGE.

F. M. Anderson 0 correlates the typical San Pablo beds of the Mount 

Diablo province with the lower portion of the Etchegoin, and this 

correlation agrees in general with that made by the writers. To be 

more exact, it is believed that the upper Jacalitos and lower Etchegoin are probably the equivalent of the typical San Pablo, and that

a Proc. California Acad. Sci., 3d ser., Geology, vol. 2, p. 180.
ETCHEGOIN FORMATION. 139

the upper Etchegoin is possibly younger than the latest San Pablo 

and agrees in age more nearly with the lower part of the fossiliferous 

Purisima formation on the southwestern flanks of the Santa Cruz 

Mountains. a

The similarity of the fauna of the upper Etchegoin to the fauna 

of the latest marine formation in the Carrizo Creek district of eastern 

San Diego County and similar beds at Santa Rosalia and other 

points in Lower California has led the writers to correlate the latter 

with the Etchegoin, and on the basis of this correlation to suppose 

that the upper Miocene sea occupied the upper end of the Gulf of 

California depression. This last correlation is in agreement with that 

of Gabb and Cooper, who considered the bed of Carrizo Creek to-be 

Pliocene (some of their Pliocene now being recognized as upper Miocene by the writers). The number of species common to the two 

faunas is not large, but the abundance of the individuals and the

uniqueness of the forms compensate for this. Among the forms common to the two faunas are Ostrea vespertina Conrad, Pecteri deserti 

Conrad, and Neverita recluziana Petit.

The similarity of Ostrea vespertina Conrad, Mytilus (Mytiloconcha) 

coalingensis Arnold, and Pecten deserti Conrad, of the Etchegoin 

fauna, to Ostrea sculpturata Conrad, Mytilus (Mytiloconcha) incurvus 

Conrad, and Pecten gibbus Linnaeus var. concentricus Say, of the 

Miocene and Pliocene of the Atlantic States, points strongly to a 

direct connection between the Atlantic and Pacific provinces during 

the Miocene. If such a connection existed it was possibly thro.ugh 

southern Arizona and New Mexico and thence along the course of the 

Rio Grande to the Gulf of Mexico, although it might have been 

farther south.

The age of the Etchegoin in terms of the standard time scale is now, 

and probably will be for some time to come, a question on which opinions differ. F. M. Anderson and the writers agree on the general 

correlation of the San Pablo and Etchegoin; about this there can be 

very little doubt. But when it comes to assigning the San Pablo and 

Etchegoin to the Pliocene, the writers differ with Andersonb and also 

with Weaver. c

According to the list found in this paper the Etchegoin is represented by 84 recognizable species. Of these, 55 species or varieties, 

or 65 per cent, are extinct, while but 29 species, or 35 per cent, are 

still living in the Pacific Ocean. According to LyelFs classification 

this would place the formation decidedly in the Miocene. Furthermore, of the fauna of 18 recognizable species at locality 4712, a fauna 

typical of the upper part of the Etchegoin, 16 species and varieties,

« Arnold, .Ralph, Proc. U. S. Nat. Mus., vol. 34,1908, p. 353. 

>> Proc. California Acad. Sci., Sdser., Geology, vol. 2, pp. 180 et seq.; idem, 4th sen, vol. 3, pp. 28 etsuq.

cBull. Dept. Geology Univ. California, vol. 5, p. 269. 
140 COALINGA OIL DISTRICT, CALIFORNIA.

or 89 per cent, are extinct and only 2 species, or 11 per cent, are now 

living.

In addition to the evidence presented above, which at best is 

largely dependent upon the personal interpretation of the meaning 

of species, there is the evidence of the position of the Etchegoin in 

the geologic series of California. An examination of its fauna indicates that its upper portion is equivalent to the lowest Purisima of the 

western side of the Santa Cruz Mountains, and there is no question 

that in places at least 4,000 or 5,000 feet a of strata separate this 

lower Purisima fauna from the lower Merced fauna, and that between 

3,000 and 5,000 feet of Merced (both Pliocene and Pleistocene) overlie the lower Merced fauna. Therefore it is evident that since the 

deposition of the Etchegoin enough time has elapsed for the deposition of between 7,000 and 10,000 feet of strata on the California 

coast. Taking 25,000 feet as a conservative estimate of the total 

maximum thickness of the Tertiary on the west coast, the 7,000 to 

10,000 "feet of strata above the Etchegoin would place the top of the 

Etchegoin at least a third of the way down toward the base of the 

Tertiary. Hence, by this line of reasoning also, it seems more consistent to place the Etchegoin in the Miocene than in the Pliocene.

IMPORTANCE WITH RELATION TO PETROLEUM.

"The Etchegoin formation is. nowhere within the Coalinga district 

known to contain any petroleum, but like the Jacalitos it has an 

important relation to the question of accessibility of the oil. Some 

wells in the Coalinga field pass through a considerable portion or 

the whole of this formation before reaching the Jacalitos or lower 

formations. All wells drilled around the edge of Pleasant Valley, 

or on Anticline Ridge, or in the Kettleman Hills will have to pass 

through this formation, and its thickness must be taken into account 

in calculating the depth of the oil sands. The great increase in 

thickness south of Waltham Creek, in this and the other postEocene formations, has an all-important bearing on such calculations.

'TULARE FORMATION (UPPER PLIOCENE-LOWER PLEISTOCENE).*

DEFINITION AND GENERAL DESCRIPTION.

The Etchegoin is overlain along the border of the valley by the 

Tulare formation, a thick terrane of bedded but little-consolidated 

gravel, sand, and clay, with occasional indurated layers throughout 

and with associated beds of fresh-water shells, marl, and limestone 

at the base. This terrane is the uppermost member of the series

 J See Santa Cruz folio (No. 163), Geol. Atlas U. S., U. S. Geol. Survey, 1909.

( Described In the preliminary report on this district, Bull. U. S. Geol. Survey No. 357, under the 

name Paso Robles formation.
TULABE FOKMATION. 141

of upturned formations exposed in the monocline on the eastern 

flank of the Diablo Range. It differs materially from the formations so far described in that the origin of its greater portion is 

doubtful, being in part fresh water, in part marine, and in part 

probably subaerial. In the Kettleman Hills, where these beds are 

best exposed, the basal sand, which appears to lie conformably 

upon the marine bed at the top of the Etchegoin, contains many 

fresh-water fossils. The beds above this have a thickness of several 

thousand feet, and as far as observed are nonfossiliferous except at 

one horizon near the summit, at which a few marine fossils have 

been found. (See fossil locality 4743.) Along the foothills west 

and northwest of the Kettleman Hills the basal fresh-water beds 

have not been recognized and may be lacking. There gravel and 

sand beds belonging to the same series overlie the Etchegoin with

local appearances of unconformity.

This whole series of tilted beds overlying the Etchegoin is here 

referred to and mapped as one formation for the reason that it appears 

to be a continuous succession and can not be consistently subdivided. It was formed under varying conditions of deposition, but 

the indications are that it represents a nearly continuous if not 

wholly uninterrupted period. Its accumulation began in the 

Pliocene epoch, probably in the earlier portion, and is thought to 

have continued pinto the Pleistocene. Its summit may be considered as the highest bed markedly displaced from its original attitude by the uplift' which threw the formation into folds. It is 

unconformably overlain by the more recent horizontal terrace 

deposits and alluvium.

The highest exposed portion of the formation appears near the 

edge of Kettleman Plain, in the south-central part of the Kettleman 

Hills, but the summit of the formation as above defined does not 

outcrop. It is probable, however, that the edge of the hills there 

marks the approximate summit of the tilted beds. The formation 

may be recognized most easily by the fresh-water fossils and strange 

bone beds at its base, to be described more fully below, by its marginal position along the valley, and by the prevalence in it of prominent beds of bowlder gravel, which is more coarse and abundant 

than in any of the other Tertiary formations. Otherwise this forma- . 

tion resembles some of the others closely, and it is in many places 

difficult to differentiate them.

PREVIOUS DESCRIPTIONS.

This formation was named Tulare by Frank M. Anderson in his 

paper entitled "A stratigraphic study in the Mount Diablo Range 

of California." 0 He stated that it is a fresh-water formation fully

a Proc. California Acad. Sci., Geology, vol. 2,1905, No. 2.
142 COALINGA OIL DISTRICT, CALIFORNIA.

1,000 feet thick lying conformably upon the Etchegoin formation 

in the Kettleman Hills. It was originally mentioned by W. L. Watts,0 

who gave a section of the beds and included a list of the fresh-water 

shells collected from them by him and identified by J. G. Cooper. 

He described the occurrence of similar fresh-water deposits in the 

region of McKittrick farther south, which are possibly to be correlated with these. In the same year Cooper described the fossils 

collected by Watts in these deposits and gave notes on their occurrence. 6

The formation here described as the Tulare was referred to in 

the preliminary report on the Coalinga district 0 as the "Paso 

Robles," owing to its supposed equivalence to that formation, which 

had been named d earlier than the Tulare. The correlation was based 

upon the similarity in stratigraphic position and lithology of the beds 

in the Coalinga district to those spreading over the summit region 

of the Temblor Range, between the Polonio and Palo Prieto passes, 

about 15 miles southwest of the southernmost exposures in the 

Kettleman Hills. These beds in the Temblor Range seemed to be 

continuous with and to answer the description given by Fairbanks 

of the Paso Robles formation in the Salinas Valley. The formation 

there was originally named from the town of Paso Robles, and 

described as a probably fresh-water Pliocene formation of unconsolidated beds at least 1,000 feet thick, spreading widely over the 

Salinas drainage area and extending nearly or quite to the divide 

(the Temblor Range) between Estrella River and the San Joaquin 

.Valley. It was stated by Fairbanks to lie unconformably upon the 

San Pablo formation, by which was meant the Santa Margarita.

Subsequent study of the Salinas Valley deposits, carried on by the 

junior author during the autumn of 1908, has shown that at least the 

lower portion of the beds there to which the name Paso Robles 

was applied are of marine origin and equivalent to a part of the 

upper Miocene succession in the Coalinga district described in the 

present paper as Jacalitos and Etchegoin. As yet no fossils have 

been found in the upper portion of the Paso Robles formation, and 

this portion may prove to be of fresh-water origin, as stated in 

Fairbanks's original description, but in view of the fact that no 

stratigraphic break in the succession of Paso Robles beds has been 

found, the discovery of the marine origin and the .approximately 

San Pablo age of the lower portion tends to cast doubt upon the 

propriety of the adoption of the name Paso Robles in the Coalinga 

field. It is not certain that the upper portion of the Paso Robles

a The gas and petroleum yielding formations of the central valley of California: Bull. California State 

Min. Bur. No. 3,1894, pp. 55, C7.

bProc. California Acad. Sci., 2d ser., vol. 4, 1894, pp. 1C7-1G9. 

cBull. U. S. Geol. Survey No. 357,1908. 

<J Fairbanks, H. W., San Luis folio (No. 101), Geol. Atlas U. S., U. S. Geol. Survey, 1904.
TULAEE FORMATION. 143

formation farther west is equivalent to any part of the post-Etchegoin 

formation in the Coalinga district; and at any rate this portion 

has a thickness of but a few hundred feet at most, so that it could 

hardly represent a great part of the important formation in the 

Coalinga district. Hence the designation of this formation as the 

Tulare is appropriate.

DISTRIBUTION AND LOCAL CHARACTER.

TULARE IN THE KETTLEMAN HILLS.

The area covered by the Kettleman Hills is the only one in which 

the Tulare is at all completely exposed. This area therefore forms 

the basis for most of the discussion of the formation given here and 

may be considered as the type locality. As shown on the map, 

the Tulare occupies an almost complete fringe around the hills., 

clipping steeply away on the flanks of the anticline which exposes

the Etchegoin beneath. Throughout the Kettleman Hills the Etche-- 

goin and Tulare formations are apparently conformable, and in 

places there are indications that a gradual change took place toward 

the end of the deposition of the former, that shallow-water marine 

conditions gave way to brackish water, and these in turn to freshwater conditions. In some places, at least, the estuarine upper Mya 

beds which are constant at the summit of the Etchegoin appear to 

grade into the fresh-water beds above.

As an example, a characteristic occurrence at the northern corner 

of the hills (at fossil localities 4716 and 4740) may be described. 

There a thickness of about 75 feet at the summit of the Etchegoin 

consists of unconsolidated fine gypsiferous sand containing at the 

base a great many Areas, etc., and at the top an abundance of delicate 

little oysters in fine grayish-white, ashlike sand and earthy, sandy 

clay full of gypsum. The oyster sand is overlain by and seems 

almost to grade into a bed a few feet thick of brittle, porcelaneous 

and opaline, black, brown, gray, and variously colored siliceous 

shale that weathers to a bluish-white tint and is locally soft and 

chalklike. It bears some resemblance to the "indicator" bed in 

the Vaqueros north of Coalinga and to the various other occurrences 

of diatomaceous and porcelaneous shale already cited, but it is not 

certain that it had a similar origin. This bed is overlain by a zone 

of sand and pebbles about 20 feet thick that is full of strangely 

shaped flinty fossil bones of purplish and black color. Three varieties of these are shown in Plate LII. Some of these bones have 

been recognized, with the aid of Mr. J. W. Gidley, of the United 

States National Museum, Dr. D. S. Jordan, of Stanford University, 

and Dr. J. C. Merriam, of the University of California, as being the 

bulbous growth from the anterior portion of the back or the anterior 

end of the ventral fin, and others as spines of some fish or different
144 COALINGA OIL DISTRICT; CALIFORNIA.

fishes. Not even the order to which these belong is determinable 

and they may by either marine or fresh-water fishes. Some associated petrified fragments resemble copralites, and there are likewise 

fragments closely resembling the teeth of mammals. Bones of the 

same character have been mentioned as associated with both marine 

and fresh-water fossils in the Etchegoin (fossil localities 4695, 4696, 

4697, 4699, and 4741). Associated with the bones in the locality 

that is being described are minute fresh-water gasteropods, and one 

small oyster similar to those in the beds below was found on the surface together with the other fossils. If oysters are in place in this 

bed they indicate an alternation of brackish and fresh water conditions. Just above the bed with bones and other fossils comes a 

zone of fine gray sand with scattered pebbles and some clay full of 

fresh-water shells, such as Anodonta, etc., and containing likewise 

specimens of the strange bones in smaller numbers than the bed 

below. Above this fresh-water zone, which is here altogether about 

100 feet thick, the formation is not fos.siliferous.

The preceding paragraph describes the contact zone between the 

Etchegoin and Tulare formations as it occurs at one place in the 

northern part of the Kettleman Hills, and although minor variations 

are to be found at every other locality the essential points are the 

same. As this description shows, the division is no sharp one and 

it is possible that a gradual change to fresh-water conditions took 

place and that the formations intergrade. The line of contact 

between the two formations is drawn at the top of the porcelaneous 

shale bed because that bed appears to be represented farther southeast by a bed of soft white sand containing oyster shells. In the 

central and southeastern portions of the Kettleman Hills this contact 

bed of shale has not been recognized definitely, but the upper 

Mya beds are at many places characterized by the inclusion of layers 

of white siliceous shale that may represent a similar process of deposition. The succession of fossils in the Mya beds is not everywhere 

as given in the paragraph above, the oysters in some localities, 

notably farther south in the Kettleman Hills, being absent at the 

top and more abundant below the beds with Mya, Area, Littorina, 

etc. It is also true that a fossil bed does not everywhere come 

within a few feet below the fresh-water beds, as for instance in the 

central and south-central part of the hills, where a zone of inkyblue clay over 50 feet in thickness intervenes between the beds with 

Mya, etc., and those with fresh-water shells. Nor does the bed 

full of strange bones generally come below the Anodonta bed. The 

latter is more commonly found immediately overlying the Mya and 

oyster beds, and the pebble beds with bones, in turn, lie above 

this. The contact zone is locally marked Jby thin hard beds of 

limestone and hardened sandstone formed of the fresh-water fossils,
TULARE FORMATION. 145

and an earthy rock with oolitic structure due to the small gasteropods that make up more than half its bulk. Beds of this character 

at the contact form the high ridge or line of hills that parallels the 

valley for much of the way along the northeast flank of the Kettleman Hills (fossil localities 4721 and 4731).

The thickness of the basal fossiliferous zone of the Tulare is usually 

no more than 60 to 100 feet, although it is as much as 300 feet on the 

southeast side of the Kettleman Hills a few miles northeast of Averial 

Gap. These variations from place to place indicate the variable 

shallow-water conditions of deposition that prevailed at the beginning 

of Tulare time; yet the constancy over at least the whole area 

occupied by the Kettleman Hills of the estuarine and perhaps brackish-water fauna at the top of the Etchegoin and of the fresh-water 

fauna just above it shows over what extent the continuous deposition 

of the material of each of these zones took place.

The only fossils found in the Tulare at a higher horizon than the 

basal zone are of marine origin and occur in the upper portion of the 

formation (fossil locality 4743). Their stratigraphic position is shown 

in the tabulated section given below (p. 147).

Above the basal zone the Tulare formation consists of a continuous unvaried succession of alternating zones and beds of uncon-- 

solidated light-gray and yellowish fine sand, sandy clay, light and 

dark clay, coarse darker-gray sand, gravel and bowlder beds, and 

occasionally interbedded layers of hard sandstone. The whole 

series is gypsiferous. The beds are usually fairly thick and massive 

and the bedding planes not very pronounced, although in some places 

the strata are sharp and square cut. Frequently the stratification 

and the dip appear more distinct from a distance than from near at 

hand. Many of the coarse sand and gravel deposits are roughly 

stratified and exhibit lenticular structure, grading within a short 

distance into finer deposits. In general, the formation resembles very 

closely the recent alluvial deposits and is almost indistinguishable 

from them except by the disturbed position of its beds.

A marked feature of the gravel is the predominance in it of subangular fragments of hard white siliceous shale derived presumably 

from the shale either of the Tejon or of the Santa Margarita (?) formation. This shale is very resistant and lends itself remarkably to 

preservation in younger deposits of gravel and debris.

The gravel deposits southwest of the Coalinga district, along the 

Temblor Range south and west of Antelope Valley, which are believed 

to be equivalent in age to the Tulare, are likewise characterized by 

the predominance of inclusions of similar shale. On the Temblor 

Range this shale comes from the formation that is continuous with 

the Santa Margarita (?) described along Reef Ridge, and it is there88170 Bull. 398 10 10
146 COALING A OIL DISTRICT, CALIFORNIA.

fore probable that the Tulare in the Coalinga district derives at least 

a large part of the shale pebbles from that formation. These pebbles 

have in general been subjected to only a moderate amount of erosion 

and resemble in this respect the similar fragments derived from the 

Santa Margarita (?) that are abundant in the recent alluvial deposits 

and are scattered over the surface of the country both near and far 

away from their source.

The other pebbles and bowlders in the gravel beds of the Tulare 

are of many different types of rock and were probably derived chiefly 

from the Coast Ranges. Many of them are angular and have been 

subjected to little wear before being deposited. Rocks of a granitic 

type are very common, and also serpentine, porphyries of different 

kinds, several varieties of basic igneous rocks, both fresh and considerably altered, jasper, sandstone, conglomerate, quartz, schist, etc.

On the summit of the most southwesterly ridge of the Kettleman 

Hills bowld.rs full of fossils characteristic of the Vaqueros beds on 

Reef Ridge, particularly Pecten andersoni, were found in the Tulare 

formation. Bowlders of exactly the same type are common in the 

upper Mya zone at the top of the Etchegoin, and this may be taken 

as a further indication of the close relationship between the summit 

beds of the Etchegoin and the Tulare, inasmuch as the materials were 

derived from the same source and, to judge by these bowlders, from 

almost exactly the same locality. These bowlders give a good illustra,tion qf the profound unconformity existing between the Vaqueros 

an^ these later Tertiary formations. The siliceous-shale fragments 

are, likewise common in the upper Etchegoin, although not present, 

as |ar as observation has gone, in the earlier beds, which proves that 

the. original shale formation, probably the Santa Margarita (?),was 

exposed to erosion during at least the later Etchegoin and the Tulare

periods.

The lower beds of the Tulare in the Kettleman Hills are, as a rule, 

not of very coarse material, although pebbles are scattered through 

them. The first important "zone of coarse gravel appears several 

hundred feet above the base. It is associated with several beds of 

hard sandstone and in consequence shows a marked influence on 

.the topography, forming a hill on each of the lateral ridges descending 

from the summit to the valley. These may be distinguished upon 

the topographic map. This zone probably occurs at a slightly variable horizon, ranging from about 500 to 800 feet above the base of the 

formation. It is in general higher toward the south and may thus 

indicate a thickening of the formation in that direction. Above 

this zone are various other prominent gravel zones.

The following tabular sections represent the character of the formation in that part of the Coalinga district in which it is most completely exposed. In each place the section was started at the edge
v . TULAEE FORMATION. 147

of the Kettleman Hills, but beds were not found exposed for about 

700 feet into the hills away from the edge. In this border area- the 

beds almost certainly have a fairly steep dip, and it would be conservative to add at least 150 feet to the total thickness given to 

represent the summit beds there.

The first section was made on the southwest side of the hills,.about 

9 miles northwest of Avenal Gap, and is as follows:

Section of Tulare formation 9 miles northwest of Avenal Gap.

Feet. 

Mostly fine, earthy, drab, and yellowish-gray, faintly bedded, massive sand,

with occasional roughly aggregated beds and lenses of pebbles and bowlders;

the stratification is very apparent from a distance,......................... 500

Similar beds of hard and compact straw-colored massive sandy clay, with partings of gypsiferous sandstone............................................. 300

Similar clay interbedded with pure sand, gravelly sand, and sandstone layers,

with a hard sandstone bed at base........................................ 75

Compact drab, gray, and straw-colored coarse and fine sand.................. 200

Thin layers of gravel and coarse sands with a bowlder bed several feet thick 

at base................................................................. 75

Pure fine sand similar to that above, with hard sandstone layers............... 125

Mostly gravel composed in large part of fragments of hard white siliceous shale, 

interbedded with sand and sandy clay, and with hard sandstone beds at top 

and base................................................................ 75

Alternating beds, from a few inches to 1 or 2 feet thick, of loose and compact 

fine sand, roughly bedded, slightly gritty clay, pebbly sand, gravel, and 

hard, usually purplish sandstone; some of the sand is speckled all over with 

inclusions of hard white siliceous shale and the gravel is largely composed 

of it..................................................................... 225

Pure clay and sandy clay................................................... 75

Fine clay and sand at top, grading down to coarse sand and pebble and bowlder 

beds at base; some fine drab sand forms hard, massive, roughly laminated 

beds......................:.............................................. 75

Drab sand with some pebbles and with gravel and hard sandstone beds at base.. 150' 

Sand and clay and a few hard sandstone beds............................... 375

Gravelly sand.............................................................. 100

Loose earthy sand full of pebbles, bowlders, and fragments of white siliceous 

shale and containing fresh-water shells and bones; at the base is a sharp 

change to the dark clay and upper Mya beds of the Etchegoin.............. 50

2, 400

The following section was made on the southwest flank of the Kettleman Hills along the Dudley-Lemoore road, which crosses about 

4 miles northwest of Avenal Gap:

Section of Tulare formation along Dudley-Lemoore road.

Feet. 

Massive 1 to 3 foot beds of well-compacted but not indurated fine sand, clayey

sand, clay, coarse sand, and gravelly sand, with several beds, many feet 

thick, of coarse gravels and bowlders in the middle and at the base. Much 

gypsum occurs in fine particles and as a filling in cracks, causing hardening 

in individual beds and in spots. Some sand and gravel beds are lenticular. 

One hundred feet below the top are two corpse sand beds 15 feet apart containing a few specimens of Ostrea and Littorinz, marine fossils (locality 4743)... 400
148 COALINGA OIL DISTRICT, CALIFORNIA.

Feet. 

Yellowish-gray earthy sand, sandy clay, and clay in well-defined massive beds,

with some pebbly sand................................................... 650

Dark clay.................................................................. 75

Thick zone of pebbly sand................................................. 150

Chiefly dark clay.......................................................... 150

Yellowish-gray fine sand yielding whitish surface sand........................ 75

Pebbly sand.................................f............................ 70

Sandy clay............................................................... 80

Chiefly fine gray sand, alternating with pebbly sand, sandy clay, and clay; a

thick zone of pebbles and bowlders occurs about 350 feet below the top..... 1,100 

Chiefly fine gypsiferous ashlike light-gray sand, with dark clay layers and

many large pebbles scattered through, but no prominent gravel beds; lower

portion is the fresh-water zone, but no fossils were here found; it overlies .

dark clay and Mya beds at the top of the Etchegoin....................... 350

3,100

The beds near the base of the Tulare are tilted as high as 40° and 

45° in the south-central part of the hills on the southwest flank of 

the anticline, but toward the edge of the hills the dip gradually 

decreases. On the northeast flank of the anticline and in the northern and southern parts of the hills the dip is not as steep as this. 

Furthermore, the belt of exposed beds is not as wide elsewhere as in 

the part of the hills "where the above sections were made and therefore no approach to the total thickness can be measured elsewhere. 

In the section in the northern part of the hills given in figure 5 the 

thickness is much less, the upper portion of the formation being 

presumably buried beneath the plain. Thence southward toward 

A venal Gap the exposed section grows constantly thicker. This fact 

may be due in part to a thickening of the formation southward in the 

same manner as the Etchegoin thickens, but no proof of such a change 

.can as yet be offered.

TULARE IN THE KREYENHAGEN AND JACALITOS HILLS.

The Tulare beds dip under the Kettleman Plain and reappear on 

the western arm of the syncline along the border of the Kreyenhagen 

and Jacalitos hills. As in the Kettleman Hills, the formation dips 

more steeply and exposes a much greater thickness toward the south, 

but here this difference is even more pronounced. The beds have a 

dip of only a few degrees northwest of Zapato Creek, and form a comparatively narrow belt to the point where they are overlapped by the 

alluvial deposits of Pleasant Valley. South of Canoas Creek they 

rise to extremely steep dips, appearing almost overturned in places, 

and cover a wide belt. They are, however, very poorly exposed. 

The formation here consists of deposits similar to those in the Kettleman Hills, but the basal fossiliferous beds have not been found. The 

formation is chiefly characterized by its heavy gravel deposits, 

which, contrary to the rule in the Kettleman Hills, in places rest
TULARE FORMATION. , 149

directly upon the Etchegoin, forming high hills fronting the valley. 

This occurrence of heavy bowlder deposits near the base has led to 

the theory that possibly the fresh-water basal zone is lacking and that 

a higher portion of the Tulare has overlapped upon the Etchegoin. 

North of Zapato Creek an unconformity between the Tulare and the 

Etchegoin is shown to exist by the fact that the gravel beds of the 

former overlap upon the Etchegoin and locally cover up some of the 

higher beds of that formation. Southeast of Big Tar Canyon the 

basal portion of the Tulare is sand and clay and is not strongly characterized. Its basal line is assumed to be at the top of a zone of 

white nodular shale beds interbedded with sand containing the 

strange bones mentioned before as occurring both in the Etchegoin 

and Tulare in the Kettleman Hills. This zone may be the equivalent of the white shale a.t the contact of the two formations in the 

northern part of the Kettleman Hills. The flinty nodules contained 

in this zone, which are similar in appearance to nodules and laminae 

occurring at about if not exactly the same horizon elsewhere in 

the Kreyenhagen and Kettleman hills, are made up of 88 to 89 per 

cent of silica, according to an analysis by R. C. Wells, of the United 

States Geological Survey. They contain only a trace of lime. The 

Etchegoin and Tulare appear conformable in the southern part of the 

Kreyenhagen Hills. The latter formation has a thickness of at least 

2,000 feet and probably much more.

TULARE IN THE GUIJARRAL HILLS.

In the northern part of the Coalinga district the Tulare is doubtless continuous beneath the valley floor but does not appear definitely 

exposed except in the Guijarral Hills, which are entirely covered by 

deposits of coarse gravel of this formation, the name of the hills being 

derived from this feature. The beds in these low hills are almost 

horizontal, but appear to dip slightly toward Pleasant Valley and 

Polvadero Gap, giving the surface the appearance of a plane inclined 

in those directions. The beds are exposed by the Coalinga anticline 

and probably belong in the lower middle portion of the formation. 

They may be traced northward on the east flank of Anticline Ridge, 

but are throughout this region poorly exposed. The contact with the 

underlying Etchegoin can not be definitely traced nor the relations of 

the two formations determined.

ORIGIN OP THE FORMATION.

The transition from salt to fresh water conditions that took place 

at the beginning of the Tulare period has been discussed, but it is 

uncertain what conditions prevailed during the subsequent period 

during which the great bulk of the formation was deposited. After 

the deposition of the fossiliferous fresh-water beds the process of
150 COALINGA OIL DISTRICT, CALIFORNIA.

change continued further and culminated in a fairly constant set of 

conditions that were prevalent during the greater part of Tulare time. 

The change may have brought about a deepening of the body of 

fresh water, or a return of the sea over the same area in which this 

formation was laid down, or, most probable of all, the transition may 

have simply reached its natural conclusion in the establishment of 

land conditions.

Lithologically, the Tulare is somewhat similar to the marine Tertiary formations in which uncoiisolidated strata are common, but the 

absence of fossils, which are so abundant in those marine formations, 

makes it doubtful whether any great part of it is of marine origin. Its 

constituent materials show that it was formed at no great distance 

from their source and that, if marine, it must have been littoral. It 

is hardly supposable that near-shore marine or lacustrine deposition 

could have continued throughout the long period represented by this 

formation, either of marine or fresh-water character, without fossil 

remains being left, as they were in the case of the earlier formations 

and of the basal fresh-water zone. The presence of the marine fossils 

noted in the second section above proves that the sea gained access to 

the basin in which the formation was laid down for a short time, at 

least, in the later portion of the period. It is not improbable that 

similar temporary incursions of the sea occurred at other times.

The Tulare beds exhibit still greater resemblance to the more 

recent horizontally stratified deposits of stream wash, wind-blown 

dust and sand, etc., forming the surface of the floor of the Great Valley 

and the various small valleys along the border of the Diablo Range. 

These deposits consist of earthy clay, sand, gravel, and fragmentary 

matter and find their counterpart in the beds of the Tulare. On the

basis of this analogy and the general absence of fossils in the main

part of the Tulare, it may be assumed that a large part of the formation was subaerial in origin, being the accumulation in the basin 

between the Sierra Nevada and Diablo ranges of the material worn 

from them during a long period of time.

The Great Valley of California is structurally a geosynclirial trough 

that must have been undergoing a process of filling during much of 

Tertiary and Quaternary time. A large part of all the material 

washed from the eastern flanks of the Coast Ranges and the broad 

western face of the Sierra Nevada during this period must have 

found lodgment in it. During the late Tertiary and the Pleistocene 

the valley was probably similar to that of to-day and the deposits 

were forming in it as now. When the movements took place during 

the Pleistocene the valley deposits were uplifted in places along the 

border and exposed as the formation here described under the name 

Tulare. During the period since that time aggradation in the large 

and small valleys of this region has continued, and if the border of
TULABfi FOBMAT10N, 151

the Great Valley and the filled synclinal basins along the present 

eastern side of the Diablo Range should now be subjected to uplift 

a thick subsequent formation resembling the Tulare would be brought 

to light. Such a formation would be in part made up of material 

derived from the Tulare and in some places would be decidedly 

unconformable, though in others perfectly conformable and continuous with it.

The occurrence of the mollusks and fish bones in such various associations and their final disappearance lend probability to the view 

that the later Etchegoin and early Tulare period was one of varying and 

possibly alternating estuarine, tide-marsh, ajad lake conditions, changing gradually to those of dry land. Such a change would be brought 

about by aggradation alone or by gradual uplift, whereas a theory 

of any other change would involve the assumption of complicated

movements.

The body of fresh water occupying the area of the present Kettleman Hills at the beginning of Tulare time, as indicated by the fossils, 

must have been shallow and must have extended over an almost 

level surface. It may have been very much such a lake as the present 

Tulare Lake, in which mollusks similar to those that inhabited the 

Pliocene lake are now living. W. L. Watts 0 gives a list-of freshwater shells obtained from beds at McKittrick, in Kern County, 

about 40 miles south of the south end of the Kettleman Hills. If 

these represent the same horizon as the basal beds of the Tulare 

they prove a great extent for the lake of that period. The absence 

of fresh-water fossils higher in the formation in the Coalinga district 

proves that this shallow lake did not persist as such. It either 

deepened or vanished. If it deepened to such a depth as to preclude 

the existence of organisms such as would be preserved in the sediments at its bottom, it is strange that the deposits should have been, 

so coarse, and it would be expected that fossils would be found 

somewhere along the belt that must have been nearer the shore, as 

for instance in the deposits that lap up over the Etchegoin west of 

the Kettleman Plain. And if such a great thickness of beds is considered as having been deposited in a deep lake it is necessary to 

postulate the existence of an unbroken barrier between it and the 

open ocean. The marine fossils noted in the second section above, 

in the upper part of the formation, represent an incursion of the sea 

that was probably brief. The beds above and below the zone of 

these fossils are similar and probably originated under the same 

conditions. If those below are supposed to be of deep-lake origin, 

it must be supposed, to be consistent, that the opposition to the 

entrance of the sea was temporarily overcome and then reestablished.

o Bull. California State Min. Bur. No. 3,1894, p. 49.
152 COALINGA OIL DISTRICT, CALIFORNIA.

The most natural conclusion regarding the Tulare period in the 

central valley is that it was for the most part one of land conditions 

somewhat similar to those prevailing to-day, and that the strata 

were formed subaerially as widespreading deposits of the streams 

descending the mountains on either side of the valley. There were 

probably various secondary transporting and sorting agencies, such 

as gravity, winds, floods, and temporary lakes.

Fairly constant subsidence probably went on, keeping the surface 

of the filling basin near the level of the sea, and at times allowing 

the sea to enter, as a result of a slight disturbance of the equilibrium 

maintained between aggradation and subsidence. There is no 

known reason for believing that at any time a structural barrier 

across the Great Valley determined a sharp line where land, lake, 

river, or tide-marsh conditions ended and sea began.

In the collection of Stanford University there are some marine 

fossils that were obtained at a depth of 1,058 feet in an artesian well 

at the east edge of Tulare Lake (in sec. 12, T. 22 S., R. 22 E.).° 

Among them are many good specimens of Ostrea lurida Carpenter, 

together with fragmentary shells, one a small shell resembling 

Mactra or Venus and another a piece of a coarse hinge resembling 

that of Mulinia. The matrix is medium-grained, .clay-colored, 

fairly well cemented sand, containing subangular fragments of 

white siliceous shale. W. L. Watts 6 cites a well boring near Tulare 

Lake in which fresh-water fossils were found at a depth of 1,058 

feet. It would appear to be the same instance, but his reference 

to the shells as fresh-water was probably not based on his own observation. F. L. Ransome 0 cites an instance at Stockton of freshwater shells found at a depth of 600 feet. Such occurrences are 

more in keeping with the theory of occasional encroachment of salt 

Water, and Of local fresh-water deposits formed in marshes or in 

temporary shallow lakes, like the present lakes in the southern end 

of San Joaquin Valley, than with the theory of the long-continued 

occupation of the basin by the sea or by a large, deep lake. It is not 

known whether the wells cited had reached the Tulare formation 

at these depths, for where the deposits forming the valley floor are 

undisturbed it would be impossible to distinguish between the beds 

limited by the arbitrary boundaries of the Tulare and the later 

sediments into which they must grade. But the question of origin 

is believed to be the same for the Tulare as for the subsequent deposits.

According to the theory of the origin of the Tulare above outlined 

the formation would grade seaward into an equivalent with more 

and more abundant estuarine elements and finally into a littoral

o They were sent in 1892 by Mr. Harvey G. Anderson through Mr. S. A. BIythe, and have been obtained 

for examination through the kindness of Prof. J. Perrin Smith. 

6 Bull. California State Min. Bur. No. 3,1894, p. 20. . 

c Bull. Dept. Geology Univ. California, vol. 1,1896, p. 381.
TULARE .FORMATION. 153

marine formation. It is believed that the latter is represented in 

the Merced formation on San Francisco Peninsula.

FOSSILS AND AGE.

Fossas.

The only important fossiliferous zone in the Tulare is that at the 

base, which may be called the Anodonta zone, because of the abundance in it of fresh-water mussels of this genus. The following species 

have been found in the Tulare formation in the Coalinga district:

Tulare (Pliocene-lower Pleistocene) fossils from the Coalinga district.

Name.

PELECYPODA.

GASTEROPODA.

PISCES.

10

t>.

V

V

V

Sr^

v

n i^

V

X

v

V

g

V

X

v

y

X

X

Y

X

Y

S(** 

V

X

1-^

f2

Y

g

8hV

§t-» 9* »

x

4715. South end of Kettleman Hills, sec. 10, T. 25 S., R. 19 E. The marine and fresh-water fossils at this 

locality are more or less mixed owing to their scattered occurrence over the surface of the eroded upturned 

beds.

4721. Northeast border of Kettleman Hills, 4miles west of Tulare Lake, on summit of 758-foothill, NE. 1 

sec. 15, T. 22 S., R. 18 E. Fresh-water zone at base of Tulare.

4731. Northeast border of Kettleman Hills, near northwest end, on top of hill (elevation 905 feet) just east 

of old road and cabin, NW. J NE. i sec. 35, T. 21 S., R. 17 E. Fresh-water zone just above oyster bed of 

locality 4728.'

4732. About 2 miles from northwest end of Kettleman Hills, on sputh side of main ridge, 1£ miles northwest of 1,245-foot hill, SW. JNE. J sec. 30, T. 21S.,R. 17 E. Fresh-water zone at base of Tulare.

4735. Central part of Kettleman Hills, on southwest side, 1 mile southwest of 1,370-foot hill and one-third 

mile northwest of oil derrick, in center of south line of SW.. J sec. 19, T. 22 S., 11.18 E. Fresh-water zone at 

base of Tulare.

4737. Eastside of Kettleman Hills, east of Dudley-Lemoore road, NE. \ SW. Jsec. 17, T. 23 S., R. 19 E. 

Fresh-water zone overlying upper Etchegoin bed of locality 4730.

4738. In Kreyenhagen Hills, 20 miles southeast of Coalinga, one-fourth mile east of B. M. 872 feet just 

south of El Cerrito well, SE. J NW. } sec. 14, T. 23 S., R. 17 E. In white shale zone at base of Tulare, as 

mapped.

4739. Same general locality as 4738, on point of 900-foot hill, nearly 1 mile northwest of B. M. 872 feet, SE. } 

sec. 10, T. 23S..R. 17E. Atcontact of Etchegoin and Tulare.

4740. Near northwest end of Kettleman Hills, 2 miles north-northwest of 1,245-foot hill, east of center of 

SW. i sec. 20, T. 21 S., R. 17 E. Fresh-water zone just above Etchegoin oyster beds and white shale of 

locality 4716.

4743. On west side of Kettleman Hills, along Dudley-Lemoore road, in steeply dipping beds of pebbly 

sand exposed in bed of arroyo, 1,000 feet up gully from edge of plain, in north part of SW. \ sec. $5, T. 23 S., 

R. 18 E. About 2,500 feet above fresh-water zone at base of formation.

FAUNAL RELATIONS AND AGE.

A comparison of the above list with the lists of species from the 

same locality prepared by J. G. Cooper 0 shows a marked discrepancy 

between the two. This is caused by. the different identifications of

a Proc. California Acad. Sci., 2d ser., vol. 4, May 26, 1894, p. 107;-' Bull. California State Min. Bur. No. 3, 

1894, p. 55; Proc. California Acad. Sci., 3d ser., Geology, vol. 2,1905, p. 180.
154 COALINGA OIL DISTRICT, CALIFORNIA.

Doctor Cooper arid the senior author of this report. Cooper identified 

the Kettleman Hill species, with the exception of two forms, as 

species now living, while Arnold, after a careful comparison of the 

fossils with the series of recent fresh-water mollusks in the United 

States National Museum, decided that with three exceptions the 

fossils were new, although in most cases allied to recent forms. A 

comparison of the two lists discloses the following relations:

" Cooper's identification. . Arnold's identification.

Aiiodonta decurtata Conrad.............. Anodonta kettlemanensis Arnold.

Anodonta nuttalliana Lea...............Probably same as above.

Amnicola turbiniformis Tryon ...........Amnicola andersoni Arnold.

Carinifex newberryi Lea ...............Carinifex marshalli Arnold.

Goniobasis occata Hinds.................Goniobasis kettlemanensis Arnold.

Goniobasis nigrina (?) Lea. 

Margaritana subangulata Cooper. ........Gonidea coalingensis Arnold.

Gonidea coalingensis var. cooperi Arnold. 

Physa costata Newcomb................Physa wattsi Arnold.

Physa humerosa Gould. 

Planorbis tumens Carpenter. ............Planorbis vanvlecki Arnold.

Sphserium dentatum Haldeman, ........Sphserium cooperi Arnold.

Sphserium kettlemanensis Arnold.

This fauna indicates that the basal Tulare in the Coalinga district 

is.possibly older than the lowest known fossiliferous beds in the 

Santa Clara formation of the Santa Cruz region and certainly very 

much older than the fresh-water fossils from the Colorado Desert of 

southern California. In fact, the basal Tulare is believed to be the 

fresh-water equivalent of the San Diego formation and lower Pliocene 

in age. About 2,500 feet above the base of the Tulare Ostrea lurida 

Carpenter, a species so far known only from Pleistocene and Recent

faunas, has been found, This fact is interpreted as indicating a

recurrence of marine or estuarine conditions during late Tulare time 

and the extension of the formation into the Pleistocene.

IMPORTANCE WITH RELATION TO PETROLEUM.

The Tulare formation does not come into contact with the oil-bearing 

formations and contains no traces of oil. Over most of the area in 

which it occurs it is separated by so great a thickness of deposits 

from the productive zones that its mere presence is usually sufficient 

to indicate the inaccessibility of the oil.

TERRACE DEPOSITS AND ALLUVIUM (QUATERNARY).

CHARACTER AND EXTENT.

The later Pleistocene and Recent periods are represented by a 

mantle of alluvium and terrace deposits covering the floor of the 

Great Valley and the large side valleys, extending over the bottoms of the smaller valleys and over the lower slopes of the foot-
TEBBACE DEPOSITS AND ALLUVIUM. 155

hills. The larger areas of these deposits are shown on the ma,p 

(PI. I), but the minor ones where the deposits form only a thin film 

over the earlier formations have not been shown. In fact, they 

would be very difficult to distinguish in many places. In the large 

valleys it is probable that these deposits have a thickness of several 

hundred feet at least, as the late period has been largely one of aggradation over these basins. Elsewhere the deposits are merely superficial and the smaller valleys and canyons are characterized rather 

by the absence than by the presence of recent fillings. The smaller 

valleys show evidences of several terraces along their sides, some of 

these being much better preserved than others. Along portions of 

Zapato Creek, as shown in Plate IV, A, six or seven terraces may be 

counted, including one at the summit of the foothills that is of widespread importance. These terraces are frequently covered with

stream gravel and sand, and such materials are widely scattered over 

the lower portions of the foothill belt, their presence tending to confuse the geology where it is not determinable whether they are of 

fluviatile origin or are derived from weathering of the underlying 

rocks. The greater portion of the whole region under discussion 

is covered by surface soil and residual sand derived from the soft 

formations. All of these comparatively recent deposits are similar 

in materials and appearance to the underlying formations and are not 

easily distinguishable from them. They have the effect of obscuring 

the main facts of the geology over large areas.

A small sand ridge, appearing to be the relic of an old beach line of 

Tulare Lake, has already been mentioned under the subject of topography. It owes its present position in part to the decrease in area 

and depth of the lake and in part to the relative uplift of the area of 

the Kettleman Hills.

VALLEY ALLUVIUM.

The nature of' the deposits covering the valley floors has been 

referred to in connection with the Tulare formation, to which they 

are similar. The exposures of these deposits afforded by the shallow 

channels of the streams flowing across the plain are limited to the 

uppermost layers, but it is probable that these give a fair representation of the .character of all of the post-Tulare beds. A typical 

exposure is pictured in Plate XII, A. A feature of the Quaternary 

deposits is that they are not predominantly coarse, but on the contrary are composed largely of fairly even grained sand and clay, often 

of an earthy appearance, horizontally stratified in intefgrading zones 

rather than beds. Lenses of gravel and gravelly sand are intercalated. Even near the hills in the gradually sloping alluvial fans 

the deposits are largely of fine materials, being in great part derived 

from soft formations. But masses of coarse de"bris containing 

bowlders, fragments, and concretions from the older formations are 

also common.
156 COALINGA OIL DISTRICT, CALIFORNIA.

LOOSE SOIL.

The soft surface sand and clay, whether originating through 

residual weathering or brought from a distance, or even where in 

place as a part of the underlying formation, is characteristically 

porous and crumbly. It is in many places and over large areas so 

soft that a horse can not step on it without sinking in over his hoofs 

or considerably deeper. This looseness of the soil is due to the complete desiccation to which it is subjected during most of the year. 

In the Kettleman Hills and Plain the difficulties of travel due to 

this cause are aggravated by the myriads of rodent burrows with 

which the surface is riddled. The ground caves in under a horse 

every little way.

STREAM CONGLOMERATE ON WHITE CREEK."

During late Quaternary time deposits of hard conglomerate have 

been in process of formation along the bed of White Creek and are 

still being formed. The creek flows from an area of serpentine and 

other metamorphic rocks and carries much mineral matter, which 

it deposits as the water evaporates, forming a white coating on the 

gravel of the stream bed and cementing it into a solid pavement. 

Through the pavement thus formed in a previous period the stream 

has carved a channel, leaving the conglomerate as a terrace deposit 

along the sides of the valley. The gravel is made up of pebbles and 

bowlders of many kinds of metamorphic and sedimentary rocks, 

but the cementing material is so hard that the stream in cutting the 

conglomerate forms clean cross sections through all the constituent 

materials.

At least three terraces appear along the sides of the valley of

White Creek. It is on the middle one of these terraces, which is

usually 20 to 40 feet above the stream, and on the lower one, which 

forms the present valley floor and stream pavement and which is 

in most places a few feet above the channel of the stream, that the 

conglomerate occurs. The conglomerate extends for about 5 miles 

along White Creek, beginning at a point some 2 miles below the edge 

of the serpentine area and terminating about a mile above the confluence of White Creek with Los Gatos Creek. The ledge forming 

the terrace capping or stream-bed pavement is in places 15 feet or more 

thick. The Cretaceous sandstone which underlies the capping is less 

indurated than the conglomerate and gives way more readily to weathering and erosion. As a result, the capping is undercut and large 

blocks of it break off. Thus erosion removes the deposit more 

rapidly than it would a formation of such hardness laid upon a more 

resistant foundation.

oThls subject was more fully treated in a paper by the present writers entitled "Conglomerate formed 

by a mineral-laden stream in California" (Bull. Geol. Soc. America, vol. 19, 1908, pp. 147-154).
IGNEOUS KOCKS. 157

An analysis by Dr. E. C. Sullivan shows that the cement deposited 

on White Creek is made up principally of calcium and magnesium 

carbonates, with minor amounts of silica and ferric oxide. There is 

little doubt that the source of this cement is in the area of serpentine and associated metamorphic rocks on Joaquin Ridge. Magnesium: carbonate and silica are only slightly soluble in water under 

surface conditions, so that when once deposited with the associated 

minerals as a hard cementing matrix between the pebbles and bowlders along the stream bed the resulting conglomerate is necessarily 

very resistant to erosion and permits cutting of the constituent 

bowlders rather than removal of these rocks from the matrix when 

attacked by running water.

IGNEOUS ROCKS.

The only igneous rocks occurring within the Coalinga. district are 

associated with the Franciscan formation. The Cretaceous, Tertiary, 

and Quaternary formations were not affected by igneous intrusions, 

and there is no evidence that there was volcanic activity in this or the 

adjacent regions during these periods.

SERPENTINE.

The serpentine that has already been described in connection with 

the Franciscan as covering such a wide region in the heart of the 

Diablo Range originated as an intrusion of basic igneous rock into 

the sedimentary Franciscan formation before the beginning of the 

period in which the Knoxville-Chico beds were laid down. There are 

many different varieties of the rock, varying from hard, little-altered 

dark-green and bronze-green peridotite', in which the constituent 

crystals are well displayed, to much metamorphosed and surficially 

altered serpentine, soft, smooth, green, white, and variously colored, 

and to related minerals. The varieties resemble those that are 

associated with the Franciscan formation throughout the Coast 

Ranges.

The hard streaks of rock form irregular outcrops and the softer 

portions weather over large areas into bare, soft heaps of comminuted 

serpentine in the shape of dust, sand, flakes, and nodules of many 

colors. The material has gathered much more rapidly than erosion 

could carry it away, and covers up the rocks to a depth of several feet 

in places. The streams flowing from the serpentine area, notably 

White Creek, carry much of the serpentine powder, and deposit it as a 

dustlike coating on the rocks along their course. It is made up chiefly 

of small flakes of an olive-gray, color and resembles bran in texture 

and consistency. Outcrops and weathering deposits of similar 

character were the source of the serpentinous shale of the Big Blue, 

described with the Santa Margarita (?) formation (middle Miocene).
158 COALINGA OIL DISTRICT, CALIFORNIA. 

SODA SYENITE FROM WHITE CREEK.

Toward the head of White Creek is a hill formed of a hard hornblende-bearing igneous rock that seems to have been formed as a boss 

intrusive in the serpentine. It is a beautiful soda-bearing syenite, 

mottled black and white and varying from an extremely fine grained 

facies to a porphyritic one, in which there are large, perfect needles 

and lath-shaped crystals of hornblende. The area of this rock as 

shown on the map is slightly exaggerated.

Several somewhat weathered specimens of this syenite showing 

variations in coarseness from the fine to the porphyritic texture were 

secured. One of these specimens was chemically analyzed by Dr. 

W. F. Hillebrand, of the United States Geological Survey, and they 

have been microscopically examined by Mr. E. S. Larsen, jr., of the 

Survey, who has kindly furnished the following description.

The specimens are all granitoid rocks of light-gray color composed' 

chiefly of dull white feldspar and its decomposition- products, but 

with numerous long prisms of a black lustrous hornblende. In addition, most specimens show secondary calcite, analcite, and green 

segirite. Drusy cavities are common containing crystals of feldspar, 

prisms of hornblende, and secondary segirite, calcite, zeolite, and 

analcite. One specimen of the rock shows both the fine and the 

coarse-grained types, separated by a sharp but irregular boundary.

A microscopic study shows that the specimens are very similar 

and that they are made up largely of plagioclase with considerable 

brown hornblende, a little biotite, accessory apatite, zircon, and 

black iron ore, and secondary .calcite, analcite, segirite, and white 

mica. No nephelite or orthoclase were found, though a few very fine 

intergrowths that were observed were thought to be possibly orthoclase and albite. The texture is granulitic. The feldspars generally

show very fine, irregular albite.twin lamellae which give a maximum 

extinction angle of 16°; the index of refraction is less than 1.540, 

and the extinction angle measured on cleavage pieces after 010 is 18° 

and after 001 is 5°. They are therefore albite. In one of the specimens 

there are numerous feldspar phenocrysts which show a core of andesine 

or andesine-labradorite grading into a broad band of albite. Alteration is always well advanced and gives rise to natrolite and white mica. 

The hornblende occurs in long, well-developed prisms without 

terminal planes. It is often twinned. Pleochroism is very marked 

in dark'brown and yellow, the birefringence is moderate, and the 

extinction angle (Z/\c) is 14°. It is probably barkevikite. Many of 

the ends and borders are altered to a very dark greenish blue amphibole, but otherwise they are very fresh even where the associated 

feldspar is completely decomposed.
IGNEOUS ROCKS. 159

^Egirite is rather, abundant in rough prisms or dendritic growths, 

which are usually collected in patches. It is strongly pleochroic in 

greens and yellows, is highly birefracting, and has X parallel to the 

length of the prisms. Analcite is not common in the fresher rock, but 

in one specimen it has almost completely replaced the feldspar. 

Megascopically the latter specimen is not very different from the 

fresher rock, but the thin section consists mainly of isotropic analcite 

with scattered grains of calcite, zeolite, segirite, and white mica, all 

inclosing fresh crystals of barkevikite.. In places a few feldspar 

crystals can be seen, but they are almost completely altered to natrolite, white mica, etc.

The following analysis was made by Dr. W. F. Hillebrand. The 

rock was of the fine-grained type and was fairly fresh. It consisted 

of albite, hornblende, some biotite, accessory apatite, zircon, and iron

ore, and secondary aegirite, calcite, zeolite, analcite, and white mica,

The analysis was made on powder of 100-mesh size and hence the 

results for H2 0 and FeO are probably very nearly right.

Analysis of soda syenite from the head of White Creek.

[By W. F. Hillebrand.]

SiOa ... .............

ZrO

A1203 .............

Cra03 ...............

FeO................

MnO...............

CaO.................

SrO................

BaO...............

............. 60.00

............. .42

............. .03

............. 16.88

............. None.

............. 1. 83

............. 3. 02

............. .12

.............. 3.16

............. .02

........I.... .06

MgO................

Na 0

Li20..............:.

H30+........ .......

p o

C02 ........... ......

s....................

.... 1. 40

............. .94

............. 9. 31

............. Tr.

............. .43

............. 1. 53

............. .14

............. .59

............. Tr.

99.88

. The norm computed from this analysis according to the method 

of the quantitative classification follows:

Norm computed for soda syenite from the head of White Creek.

Diopside. ................^........ 11. 04

Olivine.......................... 1. 28

H20............................. 1.96

C0a ............................. .59

100.19

Orthoclase....................... 5. 56

Albite............................ 69. 04

Anorthite........................ 1. 67

Nephelite........................ 5. 40

Ilmenite......................... .76

Apatite.......................... .34

Magnetite......................... 2. 55

This places the rock in Class II,.order 5, rang 1, subrang 5. 

appears to be the first rock of this division to be described, 

closely resembles the umptekite described by W. Ramsey.

To sum up, the rock has a granulitic texture and consists, when 

fresh, of albite and barkevikite with a little biotite, accessory zircon,
160 COALINGA OIL DISTRICT, CALIFORNIA.'

apatite, and iron ore. Alteration of the feldspar has produced zeolites, white mica, calcite, analcite, and aegirite. The chemical analysis is noteworthy on account of the high soda and low potash. The 

orthoclase and nephelite indicated by the analysis are probably not 

present.

STRUCTURE.

Some of the broad features of the structure of the Coalinga district have been briefly touched on in the preceding discussions of the 

topography and geology, and these as well as many of the minor 

features will be further treated in connection with the occurrence of 

petroleum in the description of the developed territory. The structural axes and the general attitude and succession of the strata are 

represented on the maps (Pis. I, XV, and XXII) and in the various 

profile sections (figs. 6, 7, 8; Pis. XVI, XIX, XX, XXI), and therefore merely a general review of the structural phenomena and the 

discussion of certain particular points are necessary here.

CEOSS STRUCTURES AND THEIR TOPOGRAPHIC INFLUENCE.

The structure of the Diablo Range is, broadly speaking, anticlinal, 

and its eastern flank is composed of a great monocline of sedimentary 

strata dipping toward the San Joaquin Valley. But the regularity 

of this monocline is broken by a series of waves and offsets into which 

it was thrown by various important as well as minor plunging anticlinal and synclinal folds, and by faults that run in various directions both parallel with and oblique to the main structural trend of 

the mountains. This main trend parallels the general course of the 

Sierra Nevada, the Coast Range, and the coast in this portion of 

California, and is approximately N. 35° to 40° W. The general

 orientation of the secondary structural axes is considerably more to 

the west of north than this. These show their influence prominently 

in the topography by producing the oblique spurs and valleys discussed under the subject of topography. The same features, both 

topographic and structural, may be observed south of the Coalinga 

district and also in the mountainous tracts west of it. It is owing to 

such structures that the Gtabilan Range converges with and joins the 

Diablo Range in the latitude of the Coalinga district; and the various 

discontinuous spurs of the high and complex portion of the Diablo 

Range, which are arranged in positions en Echelon with one another, 

may be explained on the same basis. It would appear therefore that 

the region has been subjected to two main sets of compressional forces, 

the one set acting on a line running roughly N. 50° E. (and S. 50° W.), 

and the other set along a line running N. 20° to 30° E., making a 

counter-clockwise angle' of about 20° to 30° with the former set.
STKUCTUBE. 161

:§r=> KnoxviUe-Chico 

.ft Serpentine

"a.

'flare

&K£

Santa Margarita

Etchegoin

Santa Margarita 

Knoxville-Chico

Santa Nfargarita 

Jocolitos

Etchegoin

Serpentino

Tejon 

Vaqueros 

Santa Margarito

I

88170 Bull. 398 10 11
162 COALINGA OIL DISTRICT, CALIFORNIA.

PERIODS OF MOVEMENT AND THE EFFECTS ON FORMATIONS OF

DIFFERENT AGE.

A large part if not. the major part of the movement that has resulted in the disturbance of the Tertiary beds in this region, and possibly of the Cretaceous beds over -considerable areas in which they 

were not previously greatly disturbed, took place in Pleistocene time 

after the deposition of the Tulare (Pliocene-Pleistocene) formation. 

This is indicated by the fact that the later Tertiary and early. Pleistocene formations have been disturbed almost as much as the older 

ones, and in some places as much as or even more than the Cretaceous 

beds. An example of this is found in the beds exposed in the Coalinga 

anticline, where the Cretaceous strata dip gently and appear to have 

been folded hardly at all before the Eocene and Miocene beds 

were tilted on the same anticline to the vertical position. One 

reason, however, for this comparatively little disturbed condition 

of the Cretaceous formations is their compactness and relative homogeneity, by which they resist stresses that would severely disturb the 

later, more loosely consolidated beds. Relative immunity from disturbing forces is characteristic of the Cretaceous formations in many 

parts of California. But in most parts of the Coalinga district the 

Cretaceous strata have been closely folded in spite of their resistance 

and intricately faulted partly as a result of it, showing that the disturbances that brought about these results were very severe. These 

disturbances are thought to have occurred for the most part before 

the Tertiary, or at least before the Miocene, for reasons stated in the 

discussion of the geologic history. It is certain that important 

movements took place during Cretaceous and Tertiary time, notably 

at the close of the Tejon (Eocene) period of deposition, when the

beds of that age were uplifted and greatly disturbed before the subsidence that allowed the deposition of the Vaqueros (lower Miocene) 

'sandstone on their eroded surface, and also at the close of the Vaqueros 

period. As regards the still later movements, the facts that all the 

formations from the Cretaceous to the lower Pleistocene are in places 

approximately conformable in dip, and that at least the Miocene, the 

Pliocene, and the later portion of the series almost invariably appear 

so, indicate that the whole series was affected as one during the 

Pleistocene epoch by extraordinarily severe disturbances.

In the Tertiary formations the land movements have resulted 

chiefly in folding rather than in faulting. The strata of these formations are everywhere tilted, at angles ranging from a few degrees to 

the vertical, and are locally overturned, but evidences of faulting are 

by no means as common. The only fault of importance that is definitely known to affect the Tertiary formations in this district is one 

shown on the maps (Pis. I and XV) in the Alcalde Hills southwest of
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XIII

A. OVERTURNED SHALES OF TEJON FORMATION IN AXIS OF COALINGA ANTICLINE.

Looking northwest across foothills, 8 miles north of Coalinga, Note base of overlying Vaqueros on left; the 

vegetation following lines of bedding in the fold; Joaquin Ridge in the distance. Taken from TejonVaqueros contact on ridge shown in Plate Vll. Photograph by Ralph Arnold.

Vagueros

Petroliferous gravel Siliceous shale of the Te ion

Ji. DIAGRAM OF PLATE XIII, A.
U. S. GEOLOGICAL SURVEY 

^ ^l^gparse: pi I-'.-sand

BASAL VAQUEROS OIL SANDS ON AXIS OF COALINGA A

Looking southeast along plunging axis, showing petroliferous beds dipping gently southeastward on the left, the overtu

shales of the Tejon formation in the foreground, and Pleasant Valley in the distance. Taken from Tejon-Vaqueros con
STEUCTUEE. 1()3

Coalinga. This fault has a downthrow of at least 200 feet on the 

northeast. It is discussed in the description of the geology of the 

Westside field (p. 222). A few small local faults, such as are shown 

in Plates VI, B, and X, have been noted. The displacement shown 

on the left in Plate X is due to collapse of the soft beds of the 

Big Blue, which is mapped with the Santa Margarita (?) formation 

(middle Miocene).

The older formations, on the other hand, are much faulted as well as 

folded, and many faults in them have not been mapped. The 

Knoxville-Chico (Cretaceous) beds exposed along Los Gatos Creek 

afford an excellent example of the great number of large and small 

faults that occur along a fault zone such as that which determines the 

position of this old valley.

THICKNESS OF THE SEDIMENTARY STRATA.

The great thickness of the sedimentary strata along the flank of 

the Diablo Range is proof of the greatness and comparative continuity of the movements to which the land has been subjected during 

the recorded geologic histon^. The total maximum thickness of the 

different formations, as given in the columnar section (fig. 2), is not 

measurable in any one locality, but the total is found in many sections 

to be as much as 12,000 to 15,000 feet or more.

Possibly a slight exaggeration of thickness may result from the 

spreading of the beds at the surface, where they are relieved from pressure, and from the related tendency on the part of tilted strata to assume 

steeper dips at the surface than the true dip at depths. The steeply 

dipping and locally almost overturned beds of loose, dry sand, gravel, 

and clay toward the south end of the Kreyenhagen Hills suggest the 

probability of their having expanded at the surface and thus augmented their apparent thickness. Superficial spreading, liptilting, 

and disturbance occur likewise in the more compact older rocks, 

especially in the shales of the Knoxville-Chico (Cretaceous), Tejon 

(Eocene), and Santa Margarita (?) (upper middle Miocene). The tendency toward steepening of the dip at the surface is aided by gravitational movement of the soil. A local overturn at the surface in the 

shales of the Santa Margarita (?) formation is shown in Plate XI, B. 

The exaggeration of thickness due to such surficial phenomena, however, is hardly appreciable in some portions of the district, as, for instance, in the developed oil field, where the thicknesses of formations 

as revealed in the oil wells agree closely with those measured on the 

surface; and it is not thought that it results anywhere in a large proportional increase over the true thickness. The measurements of 

formations given in this paper are intended to represent fairly* the 

thicknesses apparent in the surface outcrops, except in the discussion
164 COALINGA OIL DISTRICT, CALIFORNIA.

of the developed territory, in which many figures are given that are 

based on the measurements obtained in wells.

It has been pointed out in the description of the formations how 

they vary in thickness within short distances. This variation is characteristic of the region. In the post-Eocene formations it may be 

partly explained by the theory that the gradual subsidence which 

took place during the different periods progressed more rapidly toward 

the south than it did in the northern part of the Coalinga district, 

where the shore line must have been near, and that the periods of 

land conditions interrupting the progress of sedimentation were more 

prolonged in the northern region. A large part of the irregularity of 

thickness is doubtless due to the removal of portions during intervals 

of erosion. Furthermore, much irregularity is due to the local variations in the nature of the deposits and to the original manner and 

amount of their deposition.

UNCONFORMITIES.

The number of unconformities between formations in the Coalinga 

district gives further proof that the region underwent almost continuous movements, and that these were of various kinds. The 

unconformities are rarely clearly apparent at the contacts between the 

formations, and the unconformable relations are usually to be made 

out only from a detailed study of (1) the areal distribution of the 

formations, which gives a clue to the presence of overlap, and of (2) 

the fossils, which indicate time breaks. The evident a'ngular unconformities that have been discovered are between the Vaqueros (lower 

Miocene) and Tejon (Eocene) at various localities north of Coalinga; 

between the Tejon and older Cretaceous shales at points on Reef 

Ridge; between the Vaqueros and Cretaceous in the Alcalde Hills and

on Juniper Ridge; between the Santa Margarita (?) (upper middle 

Miocene) and Vaqueros where the Castle Mountain fault zone crosses 

Reef Ridge; between the Santa Margarita (?) and Tejon at the same 

point and also at the San Joaquin Valley coal mine; and between the 

Santa Margarita (?) and Cretaceous along the north and east sides of 

McLure Valley.

The unconformity between the Tulare (Pliocene-Pleistocene) and 

Etchegoin (upper Pliocene) north of Zapato Creek is less definitely to 

be made out. Elsewhere the formations, even those profoundly distinct in age, generally appear conformable in dip, and it is not improbable that overlaps and unconformities that have not been made 

out occur within the formations that are treated in this report as 

stratigraphic units. That little reliance is to be placed on an 

appearance of angular conformity is made clear at several- points 

north of Coalinga, where an appearance of such a relation between 

the Tejon (Eocene) and Vaqueros (lower Miocene) is to be found only
' STRUCTURE. 165

a short distance from points where the contact displays pronounced 

discordance in dip. Overlaps of all the Tertiary formations, except 

the Tulare, upon the Knoxville-Chico (Cretaceous) occur within the 

Coalinga district, thus proving their mutual unconformity. Except 

the overlap of the Etchegoin on White Creek, and that of the Vaqueros 

in the Alcalde Hills, over the sandstone of the Chico (Upper Cretaceous) 

these overlaps take place over the lower portion of the KnoxvilleChico. The variation of the formations in original areal extent and 

in thickness, lithologic character, and structure within small areas 

gives an indication of the local activity of the disturbing forces which 

have continued to act within this region.

MAIN LINES OF STRUCTURE.

Coalinga anticline and syncline. Among the individual features of 

the structure in the Coalinga district the Coalinga anticline is next in 

importance to the general monocline on the eastern face of the Diablo 

Kange. This anticline is one of the principal oblique structures of the 

range. It forms Joaquin Ridge and plunges toward the valley, exposing in turn the Franciscan rocks at the head of Joaquin Ridge and 

all the subsequent formations. The synclinal axis of its plunge is 

at Polvadero Gap, beyond which it is undoubtedly continued by the 

anticline plunging in the opposite direction, which causes the beds to 

dome up into the Kettleman Hills. At the south end of these hills, 

about a mile south of the mapped area, the anticline does not plunge 

beneath the surface of the valley again, as might be expected by 

analogy. On the contrary, it exposes a fairly low portion of the 

Etchegoin formation, beds several thousand feet stratigraphically 

lower than those exposed at the north end, and the hills are left 

incomplete, their termination being due to erosion rather than to 

structure as at the north end. The Lost Hills, which are within 10 

miles south of the area shown on the map, are due to a continuation of the Coalinga anticline. The length of this fold within the 

district is 60 miles. Its principal features are its alternating plunges 

in different directions, its curving course indicating a complexity 

in the forces which have acted upon it, its asymmetry, arid its 

broad summit and steep flanks. The plunges and arches of the 

anticline are indicated by symbols on the geologic map (PI. I). The 

steep dips on its southwestern flank north of Coalinga as compared 

with-the gently dipping summit and northeastern flank are very 

pronounced, these features being illustrated in Plates III, XIV, arid 

XVIII and on the map of the Coalinga field (PL XV). Similar 

asymmetry is observable in the northern part of the Kettleman 

Hills, although the divergence in dip on the two flanks is not so great, 

the usual maximum dip being 35° to 45° on the southwest and 25° to 

31° on the northeast. The Coalinga syncline is the parallel supple-
166 COALINGA OIL DISTRICT, CALIFORNIA.

mentary feature and forms the topographic depression of Pleasant 

Valley and Kettleman Plain. Like the anticline, it plunges southwestward from Joaquin Ridge and rises again opposite the Kettleman 

Hills. West of Oil City it dies out in low dips on the flank of the 

anticline.

The folds and faults forming the other main spurs of the Diablo 

Range in this district have already been mentioned in the discussion 

of the topography.

Structure in the basin of Los Gatos and White creeks. The structure 

in the. basin of Los Gatos and White creeks between Joaquin and 

Juniper ridges is peculiar and complicated. A broadly folded anticline of Cretaceous beds with a locally sharp axis plunges southwest 

and northeast off the flanks of these two ridges toward the lower part 

of Los Gatos Creek, where it is crossed by a broad syncline plunging 

both northwestward into the axis of the White Creek basin and southeastward into Pleasant Valley. The syncline becomes sharply defined 

and regular along White Creek, where it incloses a remnant of Etchegoin (upper Miocene). Toward Pleasant Valley it broadens out to 

form part of the general monocline dipping toward the axis of the 

Coalinga syncline. A complicated set of faults occurs along Los Gatos 

Creek, as illustrated on the map (PI. I). On the south side of the 

main line shown as the Los Gatos Creek fault zone the rocks are the 

thinly bedded dark shale and sandstone of the middle division of the 

Knoxville-Chico (Cretaceous). On the north side the massive sandstone beds of the upper division are faulted down into contact with 

them. The movement has been in the nature of a flattening out of 

the axis of the White Creek syncline toward its head, resulting in the 

formation of the main fault and of branch faults on the downthrow 

side, with greater and greater throw in the successive blocks toward 

the southeast. A great number of small faults are not of sufficient 

size to show on the map. Many of these may be seen in the exposures 

along the sides of Los Gatos Creek. Faulting of a somewhat similar 

character to that described has taken place likewise on the northeast 

arm of the syncline, but time did not allow a detailed study of the 

system. The basin of Los Gatos and White creeks has probably been 

an axis of movement along which successive disturbances have taken 

place during a long period. The southeastward continuation of this 

same line of disturbance probably accounts for the depression of 

the Coalinga anticline in the region of Polvadero Gap.

Zone of Alcalde Canyon. Another old zone of movement is represented by the southeast face of Curry Mountain and the lower part 

of Alcalde Canyon from Alcalde toward Pleasant Valley. Profound 

faulting probably took place along the zone at different times. The 

sharp northern face of the 1,900-foot hill southeast of Alcalde suggests 

faulting, but no evidence of displacement in the later Tertiary forma-
STRUCTURE. 167

tions has been obtained. The region north of Waltham Creek has 

had in some respects a different history from that to the south, and 

it is difficult to correlate the features of the geology in the regions so 

separated. To the south the formations have a far greater thickness, the sandstone portion or upper division of "the Knoxville-Chico 

(Cretaceous) is lacking, the siliceous shales of the Santa Margarita (?) 

formation (upper middle Miocene) appear and gradually thicken and 

are only doubtfully to be correlated with the Santa Margarita (?) 

formation to the north, and a great thickness of the Tulare (PliocenePleistocene) formation is steeply tilted and well exposed.

Structure in the Jacalitos Hills. Between Alcalde and Reef Ridge 

there is a depressed area occupied by comparatively low rolling hills 

that represents the structural continuation of the old synclinal basin 

of Waltham Valley. The syncline of that valley plunges toward the 

southeast and ends just within the area shown on the map on the general monocline dipping away from Reef Ridge. This monocline is 

regular except for some low, broad plunging folds northwest of 

Zapato Creek. A noteworthy feature of the Jacalitos anticline is 

that it plunges in both directions into the flank of the Jacalitos 

syncline.

Castle Mountain fault zone. The main structural features of the 

southwestern part of the territory mapped are the Castle Mountain 

fault zone and the Pyramid Hills anticline, the Avenal syncline, and 

the Diablo anticline. The first named is a very important and complicated zone of faulting that affected the Vaqueros and older formations. The downthrown side is on the northeast. Faulting along 

the same zone is the cause of the prominent scarp of Castle Mountain 

farther west. The fault is not exposed east of Reef Ridge because 

covered over by the later formations. The lowest of these, the Santa 

Margarita (?) formation, is only very slightly wrinkled at this point, 

showing that practically all movement along this part of the Castle 

Mountain fault ceased before the upper middle Miocene.

Pyramid Hills anticline. The Castle Mountain fault zone is the 

locus of an important anticlinal fold that was formed long after the 

cessation of fault movement along the eastern portion of the zone. 

The shale of the Santa Margarita (?) formation and the younger formations have been worn off over the summit of the fold, and the rocks 

exposed along this uncovered axis belong chiefly to the KnoxvilleChico. The disturbance of the pre-Miocene rocks has been so great 

that the axis of the anticline is not easily traceable within the faulted 

zone. To the southeast the general zone of faulting gives place along 

a divergent axis to an overturned anticline in the Knoxville-Chico 

beds, and this is traceable into a regular, sharp fold covered by the 

shale of the Santa Margarita (?). This is the anticline forming the 

prominent ridge of the Pyramid Hills and the northeastward-tilted
168 COALINGA OIL DISTRICT, CALIFORNIA.

monocline of the southern end of Reef Ridge and the Kreyenhagen 

Hills.

Avenal syncline. On the southwest the flank of the anticline just 

described dips down into the Avenal syncline, which determines the 

position of McLure Valley. North of Avenal Creek this syncline is an 

extremely sharp fold, overturned and much disturbed beyond the 

area of the map, but gradually plunging and becoming shallower 

toward McLure Valley.

Diablo anticline, Southwest of the valley the beds rise again 

steeply on the flank of the Diablo anticline, which is a steep fold 

plunging rapidly toward the southeast and forming Avenal Ridge, the 

end of the Diablo Range. Its axis was once overarched by the Santa 

Margarita (?) and later formations, but is now denuded of these formations and exposes greatly disturbed Knoxville-Chico beds. This anticline is one of the main axial folds of the Diablo Range.

CHAEACTER OF THE FOLDS AND FAULTS.

The folds and faults in this region are almost invariably plunging 

and curving. Most of them represent important and continuous 

structural lines along which movements of locally varying amount 

and direction have taken place. The anticlines are, as a rule, asymmetric elongated domes, with broad summits and dips increasingly 

steep away from the axis, but with varying limits of angle on the two 

sides and at different points along the longitudinal extent of the fold. 

The synclines have a reciprocal character. Several of the anticlines, 

notably the Coalinga, Jacalitos, and Pyramid Hills anticlines, are so 

formed that there may be traced on one or the other flank an axis 

along which the dip away from the summit of the fold steepens markedly. Such a structure indicates an inclined position for the main axis 

of the fold. The inclined axis of the Coalinga anticline is overturned 

at one point along Oil Canyon, and overturns occur likewise along the 

Pyramid Hills anticline, the Avenal syncline, and on the northeast 

flank of the Diablo anticline. An important feature of the structure 

of the district is that the northern portion of the axis of the Coalinga 

anticline and the axis of the Jacalitos anticline lean toward each other, 

the former toward the southwest and the latter toward the northeast, 

as if owing to a compressional force from the two sides toward the 

Coalinga syncline. The Pyramid Hills anticline is analogous in this 

respect to the Coalinga anticline northeast of Pleasant Valley and 

seems to be opposed in a similar way across McLure Valley by a contrary thrust in the Diablo anticline. The two latter folds have, however, not been studied in detail.

In regard to the character of the faults in this region little can be 

said, owing to the fact that the areas of older rocks in which they 

chiefly occur were examined only by way of reconnaissance. With
GEOLOGIC HISTOBY. 169

regard to the Los Gatos Creek and Castle Mountain fault zone, the 

planes of movement have been many and the resultant downthrow in 

each case is on the northeast.

GEOLOGIC HISTORY.o 

GENERAL FEATURES.

The portion of geologic time of which the rocks of this part of the 

Diablo Range afford a record is comparatively late. The oldest 

rocks that appear in the axis of the mountains and that form a 

basement on which the later ones rest probably go no further back 

than Jurassic time, but even in them the record is obscure. Traces 

of preexistent rocks are to be found as inclusions in the younger formations, but they tell nothing of the age and give only suggestions 

as to the character of the terranes that must have formed land surfaces somewhere within this region during pre-Jurassic time. The 

history of the later periods, however, is preserved in considerable 

detail in a great series of strata that represent probably the greater 

portion of the time from the beginning of the Cretaceous to the 

present. These have been periods of great activity during which 

earth movements affecting broad areas, but at the same time causing 

various effects locally, have resulted in continually changing conditions and produced a complicated record.

JURASSIC (?) PERIOD.

The earliest period of which there is definite record is that of the 

Franciscan formation, of which the age or extent in time is not 

known, but which is doubtfully referred to the Jurassic. The conditions that prevailed during this period were probably those of widespread marine deposition, although the absence of remains of 

organisms in the rocks leaves this origin in doubt. The Franciscan 

sediments were laid down to a great depth over a very extensive 

area covering much of the present Coast Range region, and are 

generally similar, fairly fine grained materials, consisting largely of 

fine sandstone, dark clay shale, and jasper. The natural conclusion 

to be drawn is that the open ocean occupied much of this region in 

the Franciscan period. The source of the materials is unknown.

At the close of or perhaps in part during the period when the 

sediments of the Franciscan were being laid in beds at the bottom of 

the basin of deposition, they were intruded by immense bodies of 

molten rock of a basic variety that has since been changed into the 

serpentine so abundant over the areas in which the rocks of this 

formation occur, and other igneous intrusions probably took place

a A brief discussion of the geologic history of the Diablo and .Temblor ranges is given by F. M. Anderson 

In his "Further stratigraphic study in the Mount Diablo Bange of California" (Proc. California Acad. 

Sci., 4th ser., vol. 3, 1908, p. 6).
170 COALINGA OIL DISTRICT, CALIFORNIA.

some time during the same general period. It is not possible to 

state the character of the further events or the length of time before 

the arrival of the period represented by the Cretaceous beds. There 

is no incontrovertible evidence that any of the intrusive or metamorphic activity took place after the latter period commenced.

CRETACEOUS PERIOD.

The oldest Knoxville-Chico beds probably represent an early part 

of Cretaceous time. The strata that began forming in this period 

were similar to those of the Franciscan formation, and the prevailing 

conditions were probably not greatly different in the two periods. 

The sea spread widely over the Coast Range region, probably covering much of it to a considerable depth, and coarse and fine sediments 

derived from a land area whose position and character are doubtful 

were alternatingly laid down to form the present interbedded shale 

and sandstone of the lower two-thirds of the group. Remains of 

organisms are rare in these beds, but where found indicate their 

marine origin and Cretaceous age. The general scarcity of fossils 

may indicate a fairly deep water origin for the beds. There is no 

evidence that many fossils once present have been obliterated by 

crushing or leaching. The beds contain little calcareous material 

and in many places remain without sign of great disturbance. In 

the higher portion of the Cretaceous coarser and probably more 

littoral beds predominate and fossils are somewhat more abundant.

The amount of information that has been obtained from the Cretaceous deposits of the Coalinga district does not warrant the formulation of a definite outline of theTiistory of that period. One or 

more epochs of uplift of the strata above the sea and prevalence- of 

land conditions probably intervened between long epochs during 

which the great depth of sediments was accumulated, but the length 

of these different epochs has not been determined. During the early 

portion of the Cretaceous fine materials were by far the most abundant, fine silt alternating rapidly with fairly fine sand. During the 

later portion sand was more abundant. The later portion of Cretaceous time is not everywhere represented in the district at the 

present day, owing either to the land having been above water or 

to the subsequent removal of the deposits. The conditions during 

those periods in which deposits were being formed were equable and 

resulted in the formation of homogeneous masses of strata of great 

thickness. The great zone of conglomerate that has been described 

as lying in the middle of the lower or predominantly fine-grained 

portion of the group represents a remarkable change of conditions. 

It means that a land area, of rocks in part dissimilar to those now 

outcropping in the Diablo Range, was in close proximity, and it
GEOLOGIC HISTOKY. 171

probably indicates a considerable break in time between its age and 

that of the beds below it.

The total thickness of the beds formed during the Cretaceous that 

are still within the district is at least 12,800 feet. They have become compacted since their deposition, and perhaps the original beds 

are not all present in the sections measured, so that this thickness is 

probably less than the amount of vertical subsidence that the land 

must have undergone to allow their deposition. The homogeneity 

of the successions of strata through great thicknesses shows that the 

source of the material and the general conditions did not greatly 

vary. The basin of deposition must have been subsiding gradually 

with reference to a fairly constant or rising area of land.

EARLY TERTIARY PERIOD.

The greatest diversity of movements and conditions that is 

recorded for a period in the Coast Ranges is that which throughout 

characterizes the Tertiary. In some places the era opened under 

conditions continuing those of the late Cretaceous, and in the very 

northern part of the Coalinga district the beds belonging to the 

period close to the line between these two great time divisions are 

as yet only with doubt referable to either the one or the other. 

There is, however, a great faunal hiatus between the uppermost Cretaceous fossiliferous bed (Chico) and the lowermost Eocene fossiliferous stratum (Tejon), which must represent a long period of,time. 

In contrast to the seeming intergradation of the Chico and Tejon in 

the region north of Alcalde Canyon is a profound unconformity 

between the Eocene and older Cretaceous beds farther south; and this 

overlap occurred within a small central portion of the Coalinga district. 

Either the interval of time that probably intervened throughout 

this region between the portions of Cretaceous and Eocene time here 

represented was occupied by the erosion of the upper portion of the 

Knoxville-Chico in the southern part of the field, or else the southern 

area of Cretaceous was continuously above water during the time 

occupied by the deposition of the Upper Cretaceous beds in the 

northern part of the district. Evidence was not gathered sufficient 

to decide which of these conditions was the more likely. Whereas 

the source of the sediments during Jurassic and at least earlier Cretaceous time is doubtful, the great land area and most important 

source of detritus having possibly been toward the east, the Coast 

Range belt of relief is known to have dominated the later formations, 

and the present Great Valley region, at least in later Tertiary time, is 

known to have played an active part as a basin of depression.

During the Eocene the region of the Coalinga district occupied a 

littoral belt east of the Coast Ranges and at least for a portion of the
172 COALINGA OIL DISTEICT, CALIFORNIA.

time shore-line and estuarine conditions prevailed in the vicinity of 

Coalinga. At the coal mines in the Alcalde Hills the beds that give 

evidence of such conditions are especially well exposed. They are 

roughly bedded, of varying coarseness, full of gypsum and alkaline 

salts, and interbedded with lignite, showing that the materials 

accumulated roughly not far distant from the shore in shallow, 

brackish water. Elsewhere, as along Reef Ridge, the shallow-water 

character of these beds is less pronounced. The fossil remains in the 

lower portion of the Tejon (Eocene) formation show that mollusks 

lived abundantly in the sea and that other forms, such as echinoderms, 

corals, and bryozoans, were likewise present.

It is possible that the marine conditions were exchanged during 

a long or short period for land conditions before the deposition of the 

shale beds in a later period of the Eocene, but little evidence on this 

point has been obtained. In that later period the land probably sank 

and the shore receded, the source.of supply of coarse materials being 

removed partly by this recession and partly by the base-leveling of 

the land. The deposits on the sea bottom were formed jointly by 

fine sediments and minute organisms such as diatoms and f oraminif ers 

that lived in the sea and dropped in great numbers to the bottom 

after death. In the mud that was thus formed on the sea floor the 

organic matter inside the shells of these little plants and animals 

must have become buried and been preserved. From this source 

the petroleum that seems to have originated in the Eocene shale is 

thought to have been derived. Other forms of life that inhabited 

the sea were delicate little mollusks, which probably lived in the mud 

at the bottom, and fishes, the scales of which are preserved.

The whole of the formation that was deposited during the Eocene 

is not preserved in the Coalinga district, owing to a great uplift of the 

land that brought the marine conditions to an end and subjected the 

formation to erosion. It is therefore impossible to state what length of 

time or how large a portion of the Eocene was occupied with deposition. 

There is no direct evidence whether or not the formation extended 

beyond the limit of the Eocene into the Oligocene. Trie greatest 

thickness of the beds belonging to the Tejon (Eocene) formation 

that has been preserved within the district is exposed on Joaquin 

Ridge north of Coalinga, where it amounts to at least 1,850 feet.

The land movement that caused the emergence of the area over 

which the Tejon formation was laid down during Eocene time was 

not merely of a local nature but is known to have affected a large 

portion of the coastal province. As a result of it the Eocene strata 

were upheaved and in places, notably near the axis of the Coalinga 

anticline south of Oil City and along the western border of what is 

now Pleasant Valley, were steeply tilted. Movements probably took 

place at that time along some of the lines of structure which have
GEOLOGIC HISTORY. 173

been the loci of more recent disturbances, and at that time also 

some of the features of the present Diablo Range were determined. 

During most and probably all of the Oligocene period the region of 

the Coalinga district, as well as a much greater portion of the southern 

Coast Ranges, was land and the Eocene and older beds were exposed 

to erosion. As a result large parts of the pre-Mocene formations were 

worn away and parts of the surface planed off.

MIDDLE TERTIARY PERIOD.

Early in the Miocene the area of the eastern flank of the present 

Diablo Range became pretty generally submerged to a slight depth 

below the sea, and the worn surface of the older formations became 

the floor upon which the marine deposits of sand, pebbles, clay, and 

shells were formed that have been described as the Vaqueros formation 

(lower Miocene). During this period land areas probably remained in 

the northwestern and southwestern portions of the region that is now 

the Coalinga district. In the northern part of the district coarse shore 

deposits were formed at the beginning of the period. In the southern 

part the deposits were littoral but less markedly so, the basal beds 

being in places more fine grained than those above them. The 

greater part of the period was taken up by deposition of mediumgrained sand materials within a littoral belt. Among the living 

organisms that flourished in this belt we know from the abundant 

remains that mollusks and echinoderms existed in great numbers. 

They were of species characteristic of the early portion of Miocene time 

throughout the coastal region of California. Remains of trees were 

abundantly preserved in the gravel and sand deposits, supposedly of 

lower Miocene age, that form a capping on the flanks of Juniper 

Ridge. These deposits were laid down upon a level surface that had 

been worn in the Cretaceous rocks and may have originated in part 

on a land area adjoining the shallow sea waters. At one stage in the 

middle portion of the period a peculiar change of conditions that is 

not easily explainable took place in the northern part of the district. 

Coarse materials ceased to be deposited, and practically the only 

materials that were laid down were the remains of diatoms and 

foraminifers mixed with extremely fine silt. As a result the 15 to 20 

foot "indicator" bed was formed. In the succeeding stage in the 

same area fairly coarse sand somewhat resembling beach sand was 

the chief material deposited, and the remains of a near-shore marine 

fauna, consisting chiefly of mollusks, were preserved. A rough 

measure of the Vaqueros (lower Miocene) period is afforded by the 

thickness of the strata laid down. The compact beds of Reef Ridge 

have a maximum known thickness of about 900 feet.

The relation of the formations on the two sides of the Castle 

Mountain fault has an important bearing on the questions involved
174 COALINGA OIL DISTRICT, CALIFORNIA.

in the history of the early Miocene as well as other periods. The 

Eocene and lower Miocene formations stop near the south end of 

Reef Ridge at this fault zone, and first appear again on the southwest 

side of this fault 7 miles south of Little Tar Canyon on the southwestern edge of McLure Valley.

The hypothesis that seems best to fit the conditions outlined 

above postulates that the region west of the fault must have been 

thrown up as a great block or series of faulted blocks during the 

period of movements following the lower Miocene, and that the 

Eocene and lower Miocene beds that had been formed over it were 

almost completely eroded away and the fault block completely reduced during the early middle Miocene land period.

No faulting has taken place along this portion of the fault line 

since the early middle Miocene, as is proved by the fact that the later 

beds are unaffected. The prominent fault scarp of Castle Mountain 

a few miles northwest may be due to more recent movement along 

the fault there while it has been stationary near Reef Ridge. Unless 

such a movement has taken place the prominence of this topographic 

and structural feature would tend to favor the latest possible date 

for movement along the fault zone as a whole, namely, the early 

middle Miocene.

The deposition of beds in the Vaqueros (lower Miocene) period was 

brought to an end by movements which, it is thought, left the land in 

this portion of California not far above the sea, so that in the succeeding middle Miocene period no great amount of sediment was removed 

from this region to the wide expanse of sea farther west, in the region 

now west of the Salinas Valley, in which the fine, largely nonterrigenous ooze of the Monterey shale, was laid down. As a consequence, 

the Vaqueros beds were locally well preserved, and when the time 

came for later sediments to be laid down upon them there Were 

preserved at the contact no striking evidences of the time that had 

elapsed. Good structural evidence, in addition to that of paleontology, that a time interval and erosion did occur, however, is afforded 

by the varying thickness and locally complete absence of the Vaqueros, 

the deposits of the upper middle Miocene (Santa Margarita (?) formation) overlapping upon different horizons and in places directly upon 

the pre-Miocene rocks. In the region of the Stone Canyon coal 

mine, near the summit of the Diablo Range, west of the Coalinga 

district, the shale of the Santa Margarita (?), which is supposed to be 

the equivalent of the shale referred to the same formation in Reef 

Ridge, lies with distinct unconformity upon the tilted and eroded 

lower Miocene beds, showing that there, too, a land period came 

between.

In the northern portion of the Coalinga district it is not impossible 

that there have been preserved in the Big Blue, in its sands and coarse
GEOLOGIC HISTOKY. 175

gravel and strange serpentine detritus, accumulations that took 

place during a portion of this interval between the marine invasions of 

the lower Miocene and later middle Miocene.

It will be a matter of considerable interest to determine to just 

what age the Big Blue belongs, both on account of its bearing on the 

history of the Monterey period and because it is the earliest zone 

giving indubitable evidence of the occurrence in it of fragments of 

the rocks associated with the Franciscan formation. On the northern 

flank of Joaquin Ridge this zone is composed almost entirely of serpentine fragments of all sizes derived from a near-by area in which 

the Franciscan was exposed. It is very probable that this area was 

in the same position as the present serpentine area on Joaquin Ridge 

and was brought to the surface by post-Eocene folding along the line 

determining the axis of the present Coalinga anticline and by erosion

over the area thus uplifted. There is no proof that the Franciscan 

formation or its metamorphic associates appeared at the surface 

in this district in any preceding period.

After the early portion of the middle Miocene period had elapsed 

a great subsidence took place and brought the whole southern part 

of the district below a deep sea. The subsidence there was probably 

progressive from south to north. In the region of the present Temblor Range south of the Coalinga district the Monterey (early middle 

Miocene) period is represented, and the subsidence there may have 

continued through most of middle Miocene time, allowing a very 

great thickness of shale beds to be formed. If such is the case, the 

area of subsidence widened toward the north until it affected the 

southern part of the Coalinga district in the latter portion of the 

middle Miocene period and caused the deposition of deep-water 

shale beds as a continuation of the upper portion of the series farther 

south.

The conditions that prevailed during the period of deposition of 

the shale of the Santa Margarita (?) formation must have' been similar 

to those of the later part of the Tejon (Eocene) period already discussed and to those prevailing during Monterey (niiddle Miocene) time 

over a considerable portion of the Coast Ranges.0 Organic remains 

are not well preserved in the shale of the Santa- Margarita (?) formation of the Coalinga district, but it is almost certainly largely composed of siliceous and in lesser amount calcareous remains, of diatoms 

and foraminifers, respectively.

In the northern portion of the district the subsidence during the 

Santa Margarita (?) period was not so great and coarse shallow-water 

sediments were laid down. For a portion of the time there thrived 

here a fauna of strong-shelled mollusks, barnacles, and echinoderms

a For an outline of the history of this period elsewhere see Fairbanks, San Luls folio (No. 101), Geol. 

Atlas U. S., U. S. Geol. Survey, 1904, p. 9; and Arnold and Anderson, Geology and oil resources of the 

Santa Maria oil district, California: Bull. U. S. Geol. Survey No. 322,1907, p. 67.
176 COALINGA OIL DISTRICT, CALIFORNIA.

(sand dollars), fitted to survive in troubled waters along shore. This 

subsidence may have immediately preceded or been contemporaneous 

with that in the area of the Kreyenhagen field.

The thickness of strata deposited during the Santa Margarita (?) 

period in the region around the modern Pleasant Valley was about 

600 feet (exclusive of the Big Blue). The shale in the southern part 

of the district was laid down to a thickness of as much as 1,200 feet.

LATE TERTIARY AND EARLY QUATERNARY PERIOD.

The close of the Santa Margarita (?) period witnessed an uplift of 

the land over the large region that its deposits covered, and the 

beginning of a long period, occupying most of the rest of Miocene time, 

during which shallow-water deposits were formed in arms of the 

sea that were separated from each other by land areas coincident in 

large measure with the more elevated portions of the present Diablo 

Range. Probably an interval succeeded the Santa Margarita (?) 

period during which the area of the Coalinga district was not submerged, but no measure of its length has been obtained and it can 

not have been as long as the previous interformational periods that 

have been made out. It is thought to have been longer in the northern than in the southern part of the Coalinga district. The great 

succession of littoral marine sand, gravel, and clay beds that followed 

mark a gradual subsidence during the Jacalitos and Etchegoin periods, 

which are the equivalent of upper Miocene time. This subsidence 

was probably effected by a gradual process of downfolding in basins 

of depression that crossed a belt of topographic relief corresponding 

to the present Diablo Range, and in the large basin of the San 

Joaquin Valley. The mountainous tracts of the older formations were 

probably at the same time subject to uplift that caused them to 

preserve a fairly uniform relation to the sea area and resulted in a 

comparatively stable position of the shore line. Roughly speaking, 

the Diablo Range may be said to have existed as a row of islands. 

The continued presence of these islands preserved the littoral character of the beds which were laid down along their shores and which 

were later upheaved to form the present fringe along the eastern base 

of the Diablo Range. The belt of lowland bordering the mountains 

must have been occupied for part of the time by arms of the sea in 

which estuarine conditions prevailed and in which large amounts of 

gypsum and alkaline salts were precipitated. The thickness of the 

deposits that were laid down under these conditions, in the Jacalitos 

and Etchegoin periods, amounts to over 7,000 feet, and may be taken 

as a rough measure of the time that elapsed and of the depth to which 

the basal platform of the basin or basins sank. The beds of this age 

are preserved in large part in their original incoherent state and their 

thickness does not represent as much deposition as a similar thickness would in the consolidated beds of some of the older formations.
GEOLOGIC HISTORY. 177

The conditions outlined above did not prevail uninterruptedly 

during the whole of the period represented by the Jacalitos and 

Etchegoin combined. There probably were many oscillations in the 

orogenic movements and complex variations in the areas and degrees 

of movement, in the land areas, and in the conditions of climate and 

supply of sediments. Such changes are attested by the variety of 

the beds and zones of deposits that were formed, and by the presence 

within the series of strata, that originated in fresh water or on land, 

but are far too complicated to be made out in detail. There was at 

least one period, the close of the Jacalitos, when a' marked disturbance 

took place. In the northern part of the region under discussion the 

sea spread much farther westward before the beginning of the Etchegoin, causing the beds of that period to overlap beyond the limits of 

the Jacalitos and to be laid down unconformably upon the Cretaceous and Franciscan. It is possible that an uplift had preceded the 

subsidence that caused this overlapping and had raised' the earlier 

upper Miocene beds above the sea, allowing them to be eroded; but 

somewhere within no great distance the marine conditipns and 

sedimentation must have been continuous, and the appearance of 

conformity between the Jacalitos and Etchegoin formations on 

Joaquin Ridge and in the Kreyenhagen Hills indicates that at 

this distance from the axis of the mountain belt to the west 

deposition went on without interruption. The much greater thick-- 

ness of the formations south of Waltham Creek than north of it points 

to episodes in the history of the northern region that have not been 

made out. Probably the progress of sedimentation was broken at 

different periods in the northern region when continuous in the southern, the line at present followed by the southern end of Curry 

Mountain and the lower portion of Alcalde Canyon havingT^een a locus 

of changes separating areas of different geologic history.

The kinds of organisms that lived in the upper Miocene period 

and left relics in the rocks were principally mollusks and echinoderms, the latter including both sea urchins and sand dollars. Cirripedia (barnacles), brachiopods, and corals were also common at 

certain times, and fishes and sea mammals (either cetaceans or sirenians) left a record in their teeth and bones. A great abundance of 

fossil wood is preserved in the near-shore gravel and sand beds that 

were formed during the Jacalitos (early upper Miocene) period, 

and in one place the tooth of an extinct species of horse is associated 

in the same zone. The conditions throughout most of the period 

were favorable to marine life and rich faunas were preserved.

The Etchegoin (late upper Miocene) "period was brought to a close 

by a gradual uplift of the land and transition from locally varying 

88170 Bull. 398 10 12
178 COALINGA OIL DISTRICT, CALIFORNIA.

open-sea and estuarine conditions to more generally prevalent estuarine and perhaps also brackish-water conditions. The faunas 

reflected this change and the sediments became thoroughly impregnated with and in places largely made up of salts, especially gypsum. 

The marine body of water gave place in turn either through a direct 

transition or after the intervention of a land period to fresh water 

at the beginning of the Tulare period, which includes most of Plio- 

. cene time and probably a part of the early Pleistocene. The origin 

of the deposits of this period and the conditions prevailing during it 

have been discussed above in the description of the formation. Suffice it to say" here that the character of the period is in doubt, but 

that the stage with which it opened was not of long duration; that the 

course of events following that stage probably did not differ greatly 

from present history; and that the period was probably largely taken 

up in deposition of sediments subaerially over the topographic 

basins, gradual subsidence of the basins, and temporary incursions 

of the sea into them. Deposits of various kinds, fresh-water, subaerial, and marine, were built up into one conformable succession of 

beds with a thickness of as much as 3,000 feet or more. The period 

ended in great orogenic movements that caused the greater part of 

the disturbance now visible in the post-Eocene formations. The 

Tulare beds and all those below them Were warped-into folds and 

tilted at high angles. Similar movement took place widely along 

the Pacific coast early in the Quaternary", and the disturbances here 

may be ascribed to the same general epoch of activity. It is partly 

on the basis of this correlation of movements that the Tulare period is 

considered as extending into Quaternary time. The previous greatest periods of movement of which record has been obtained in 

the Coalinga district were at some time in the later, half of the

Cretaceous and at the close of the Tejon (Eocene). The relative 

importance of these movements is hard to estimate. It would 

appear from the fact that all the post-Eocene beds up to the Quaternary have been so violently displaced, the youngest as much as 

the older ones, while the earliest formations are. not everywhere 

greatly disturbed, that the movements following the Tulare period

- were the most profound of all. But it must be borne in mind that

the compact older formations have acted as a buffer against which

... the late movements have crushed the little-consolidated and there-

-. fore,pliant.later strata, and that great disturbance in the Tertiary 

. and later beds does not necessarily represent as great a causal force 

as slighter displacements in the great homogeneous and compacted 

series of older rocks, such as those belonging to the Cretaceous. 

This principle being taken into consideration, and the great amount 

of disturbance in most places in the Cretaceous beds due to forces 

acting in a period preceding the Miocene being noted, it may be
HISTORY OP DEVELOPMENT. 179

conceded tentatively that the greatest erogenic movements were of 

pre-Miocene date. The strata on the flanks of Juniper Ridge may 

be cited as an example of the comparative amount of deformation 

produced in some places" by the different movements. The Cretaceous beds there were 'steeply tilted before the Miocene, and the 

Vaqueros (lower Miocene) strata that were laid down over their 

eroded edges have been uplifted with only gentle tilting in the subsequent periods, whereas only a couple of miles eastward, where not 

protected by the solid foundation of Cretaceous rocks, the Miocene 

beds have been sharply folded and faulted. The movements following 

the Tulare resulted both in broad tectonic uplift and in local warping 

along'the axes of upward movement that determine the present 

mountain and hill tracts. But these axes had already existed for a 

long time and the broad features of the mountain regions had been 

outlined in the previous epochs of movement.

LATE QUATERNARY PERIOD.

The processes that are taking place at the present time are a continuation of those that have been active since the end of Tulare time. 

During the later Quaternary .the great basin of the San Joaquin Valley 

was continually receiving the wash from the mountains, and approximately horizontal .deposits similar to those of the Tulare formation 

were being laid down over the valley floor. They must have accumulated to a depth of many hundred feet in this and the smaller 

vajleys as well. During this period- the mountainous tract was 

being worn down; but at the same time it underwent a gradual 

uplift that kept pace partly with the wasting away. It is not 

known how great a portion of Quaternary time the Tulare period may 

have occupied, but judging by the amount of movement along the 

structural axes, erosion of the mountains and hills, and aggradation 

of the valleys that has taken place since its close we may conclude 

that most of the Quaternary has been consumed in the subsequent 

events. Some other features of the geologic history are outlined 

in the sections dealing with the physiographic development and the 

faunas.

THE DEVELOPED TERRITORY.

HISTORY OF DEVELOPMENT IN THE COAHNGA DISTRICTS

The attention of oil men was early called to what is now known 

as the Coalinga oil district by a "live" oil seepage on the south line 

of sec. 17, T. 19 S., R. 15 E. of the Mount Diablo base and meridian, 

at a point about 1,000 feet east of the southwest corner of this section.

a Many of the data concerning the early developments in the Coalinga district have been obtained from 

written communications of W. W. Orcutt and from accounts given by W. L. Watts in bulletins 3 and 19 

of the California State Mining Bureau, published, respectively Jn 1894 and 1900. Thewprfeof G. H.EJdridge 

lias also brought to light some information which is here included.,
180 COALINGA OIL DISTRICT, CALIFORNIA.

At this point a considerable quantity of light oil of a greenish color 

came up through the shales. It is said that in the early seventies 

this oil was collected in pits and there refined in a small way.

The early prospectors believed that this seepage had its source in 

a productive oil sand, but they did not know its extent, its depth 

below the surface, nor in what direction the sand lay from the seepage, for at this point the strike of the shale swings abruptly from a 

nearly north and south line to an easterly and westerly direction.

The first successful development work in the Coalinga district 

took place in the Oil City field about 1890. At this time the Coast 

Range Oil Company, of Los Angeles, sunk a well'163 feet in the 

purple shale of the Chico formation in the northern part of sec. 20, 

T. 19 S., R. 15 E., from which gas and a little greenish oil of light 

specific gravity is said to have flowed. A windmill pump was 

attached to this well, and 10 barrels of oil was pumped from it 

daily for two days, after which the production fell gradually.

In 1891-92 four wells were drilled in the same vicinity by Messrs. 

Rowland and Lacy, of Los Angeles, but only one of these was successful. It was 400 feet deep and yielded 9 barrels of oil daily.

W. L. Watts visited the district in 1893, gathering material for 

his report on the San Joaquin Valley oil districts, 0 and reports that 

at that time he found five wells in the Oil City -region, three of which 

were plugged and in two of which oil or gas was rising. . The prospects for a great field were therefore not encouraging at that time.

In 1895 the Producers and Consumers Oil Company, of Selma, 

organized by J. C. McClurg and others, sank two wells a short distance southeast of the wells of Rowland and Lacy, which yielded 

15 and 20 barrels of 34° Baume oil per day.

In 1896 Chanslor & Canfield drilled three wells in the southern 

part of sec. 17, T. 19 S., R. 15 E., just north of the sites of the original 

Oil City wells, and were rewarded with small producers. They then 

took over the property of the Producers and Consumers Oil Company in the NW. | sec. 20 and drilled a well 300 feet east of the 

old wells and struck oil sand at 890 feet, which yielded 300 barrels 

of oil per day. This was the first big well of the district.

The Clear Field Oil Company, a branch of the Union Oil Company 

of California, drilled a well in the southeast corner of sec. 18, T. 19 S., 

R. 15 E., in 1897. This well was 1,100 feet deep and showed only 

a trace of oil.

In 1897 the Home Oil Company, of Selma, entered the field and 

began drilling still farther east or farther down the dip of the strata, 

and completed a 1,400-foot well (the famous Blue Goose), which is 

said to have flowed from 500 to 1,000 barrels of oil per day and to 

have maintained a production of 250 barrels per day as late as August,

o Bull. California State Min. Bur. No. 3,1894.
HISTORY OF DEVELOPMENT. 181

1900. Unsuccessful wells were drilled in the Westside field during 

this year, among them being that of the Sunnyside Oil Company, 

now the Henshaw water well.

In 1899, after the completion of the Blue Goose well, several other 

companies commenced operations in the Oil City field, but with indifferent success or failure. The most important event in development during this year was the drilling of water wells by J. A. McClurg 

in the SW. i sec. 16, T. 20 S., R. 15 E., the water thus obtained 

being piped to the Oil City field and the region to the west.

The development of the Eastside field began in 1900 with the 

 drilling operations of the Independence, Oil City Petroleum, Twentyeight, Caribou, and other companies. During the same year several 

prospect holes were put down in the Kettleman Hills and Kreyenhagen fields. In the latter field several more or less productive wells 

had been put down a short time previously. Between 1900 and 1907 

no developments of consequence took place in the Kettleman Hills 

and Kreyenhagen fields, but in 1907 and since then up to the present 

time more or less activity has been displayed in the region south of 

Waltham Creek, and such wells as the Golden Crest and El Cerrito 

have attempted to obtain oil in formations overlying the Santa Margarita (?), but so far without success.

Successful development work was begun in the north end of the 

Westside4 field in 1901, when the Mercantile Crude, Commercial, 

Call, Main State, and other companies started drilling. Exploitation was.gradually carried southward until the region as far as the 

Esperanza lease in the SW. £ sec. 6, T. 20 S., R. 15 E., was proved. 

The unsuccessful Blue Diamond hole in the NE. \ sec. 26, T. 20 S., 

R. 14 E., was also put down about this time, and tended to discourage development in the southern part of the western field.

In 1902 the California Oilfields (Limited) entered the Eastside 

field and soon began active operations in sees. 21 and 27, T. 19 S., 

R. 15 E. Development work was still carried on in the Westside 

field, but the decline in the price of oil was at this time beginning to 

show its effects on the development.

Notwithstanding the low price of oil, which reached as low as 15 

cents per barrel in 1905, drilling operations were carried on continuously'throughout certain parts of the field from 1902 to 1906. In 

the fall of 1906 the Lucile well was brought in as a strong producer, 

thus proving the south end of the present Westside field. Beginning 

with the impetus that this discovery gave to development and 

encouraged by the gradually bettering conditions of the oil market, 

exploitation throughout the Coalinga field went ahead rapidly until 

in the summer of 1908 about 100 wells were being drilled simultaneously in the district. Mention should be made of the influence of 

the operations in the northern part of sec. 34, T. 19 S., R. 15 E.,
182 COALINGA OIL DISTRICT, CALIFORNIA.

which were carried on in 1906 and 1907, by the late Mr. W. P. Kerr 

and associates. The wells brought in by these men are the most 

productive in the district. During the latter part of 1906 and the 

beginning of 1907 these and practically all the other independent 

wells in the Eastside field, with the exception of those in section 22, 

were absorbed by the California Oilfields (Limited) or by the Standard Oil Company, which had entered the field as a producer.

An important event in development in 1908 was the completion of 

the T. C. Oil Company's well in sec. 2, T. 19 S., R. 15 E., which 

extended the proved territory of the Eastside field 2 miles northward. 

Among the developments of importance in 1908 and 1909 were the 

series of exceptionally productive wells of the American Petroleum 

Company drilled along the eastern edge of the proved Westside field, 

and the wells of the Nevada Petroleum Company drilled still farther 

east, which showed zone B to be unproductive in that territory but 

which encountered productive beds in zone D. In September, 1909, 

the Silver Tip No. 1, in sec. 6, T. 21 S., B,. 15 E., came in as a gusher 

and produced at the rate of about 20,000 barrels a day for several 

hours. This well drew the attention of 'oil operators to the south end 

of the Westside field, and its completion was followed by renewed 

activity in sec. 12, T. 21 S., R. 14 E., and'sec. 18, T. 21 S:, R. 15 E.

AREAS DISCUSSED.'

' ' * ' -

For convenience of discussion the Coalinga district has .been roughly 

divided into five fields or regions, and these into lesser subdivisions 

or areas. The major subdivisions are as follows: (1) The Oil City 

field, lying in Oil Canyon near the north end of the district; (2) the 

Eastside field, embracing the territory northeast of Oil Canyon and 

including Anticline Ridge; (3) the Westside field, extending southeastward from Oil Canyon as far as Alcalde Canyon; (4)-the Kreyenhagen field, which includes the Jacalitos and Kreyenhagen hills, 

Reef Ridge, and the territory southward to the Kings County and 

Kern County boundary; and (5) the region of the Kettleman Hills, 

extending from, the Guijarral Hills southward.to the gap separating 

the Kettleman Hills from the Lost Hills.

OCCURRENCE OF THE PETROLEUM.

The following is a brief summary of the conditions of occurrence 

of petroleum in the Coalinga district, and is inserted here as introductory to, the detailed and necessarily more local discussion concerning each particular field, which follows.

FORMATIONS IN WHICH PETROLEUM OCCURS.

"^ .

Petroleum occurs in five different formations in this district the 

purple-shale member of the Chico -(Upper Cretaceous), the Tejon 

(Eocene), Vaqueros (lower Miocene), Santa Margarita (?) (upper
OCCURRENCE OF THE- PETROLEUM. 183

middle Miocene), and Jacalitos (upper Miocene)/, In the first two the 

oil is thought to be primary that is, it is 'believed to have originated 

in the formations; in all the others it is secondary that is, it has 

come into them from some outside source since their deposition.

OIL'ZONES.

General description. Within each' of * the formations mentioned 

are one or more oil-bearing zones-consisting either of more'or--less 

extensive layers of sand or gravel or of local lenses of the same materials, which can be traced in a general way over-large areas. , The,oil 

sands in the Chicq will be referred to collectively-as the Chico oil zone;, 

those in the Tejon as the Tejon oil zone; those in- the-lower part of 

theVaqueros as'the lowest Vaqueros zone;-or -zone-D; those in the 

middle Vaqueros (Eastside field light-oil sands)'-'as' the light-oil zone, 

or zone C; those in the upper-Vaqueros (first sand) .in the fields

northeast of Los Gatos Creek and in the Santa Margarita (?) and 

the lower Jacalitos in the Westside field south of. Los Gatos Creek 

as zone B; and those in the Jacalitos in the Westside field above 

the productive basal beds of that formation as zone A. The top of 

zone B is shown in contour in Plate XV. With the exception of those 

in the lowest zone in the Vaqueros (zone D) the oil sands are known 

to consist mostly of more or less local beds or lenses varying in thickness, composition, grain, and hardness from well to well and often 

showing a puzzling diversity in gravity of product within short distances. Zone D, as would be expected of the basal portion of a widespread formation, partakes of the same general characteristics 

throughout nearly its entire range within the district that is, it is 

generally coarse gravel at the base, with somewhat finer gravel or very 

coarse sand above this and finally medium-grained sand. The productive beds in the other" zones vary from medium fine-grained to 

coarse pebbly sand or even gravel.

Chico oil zone. The sandy-zones in the lower portion of the purpleshale member contain commercial quantities of oil on the Coalinga 

anticline in the Oil City field. It was the inducement offered by 

seepages from this member in the Oil City region that led to the drilling of the test wells from which the present district has been developed. The oil in the Chico oil zone is a paraffin oil, usually of light 

gravity, about 33 ° to 34° Baume, and is"greenish in color. The thickness of .the productive sands is ordinarily'between 15 and 60 feet, 

and the yields are ;light, 4 to 75 "barrels per well per day being the 

normal extremes of production, "although the initial flow of one of 

the Oil City wells is said to.have-be'en'700 barrels per day. 

Tejon oil zone.-, The Tejon is: knoWn to contain accumulations: of 

oil in commercial quantities only'in the' southern portion of the district, where the oil has gathered in 'tlie porous sandstone of the lower
184 COALINGA OIL DISTRICT, CALIFORNIA.

member, below the shales of the upper member, in which it is supposed to have originated. The productive sandstone outcrops in the 

steeply dipping monocline of Reef Ridge in the Kreyenhagen field. 

Wells have been put down at a number of places, but have obtained 

only small quantities of oil from this zone. An amber-colored oil of 

45° to 48° Baume" gravity occurs sparingly in the uppermost productive Tejon sands of the Oil City field. This is the lightest oil in the 

Coalinga district and among the lightest in the State.

Vaqueros oil zones. The principal oil-bearing formation in 'the 

Coalinga district is the Vaqueros or lower Miocene. It yields practically all of the oil in the,Eastside field and a considerable part of 

that in the Westside field and is thought to contain commercially 

important quantities in the Kreyenhagen field and in the region of 

the Kettleman Hills. The total distance penetrated through this 

formation by the wells in the Eastside field is about 700 feet, and in 

the Westside between 300 and 500 feet. The actual productive 

sands of course occupy only a relatively small space in this column, 

usually under 150 feet in the Eastside and under 100 feet in the 

Westside. Three zones are recognized in this formation, the lowest 

or zone D, the middle or zone C, productive only in certain parts of 

the Eastside field where it yields oil up to 31° Baume" in gravity; and 

zone B, recognized as Vaqueros in the Eastside field and the n'orthern 

part of the Westside field. The oil from the Vaqueros varies in 

gravity from 14° to 22° in the Westside and from 14° to 31° in the 

Eastside. It is black or dark brown and the production averages 

between 100 and 200 barrels per well per day. One well in the 

Eastside field is now flowing 3,000 barrels of oil per day and an 

initial yield of 7,000 barrels in 18 hours was recorded for another well 

in the same field, but these figures are unusual. The Silver Tip well,

in the south end of the Westside field, yielded at the rate of 20,000 

barrels a day for a few hours during its initial flow; this is the maximum rate for the district.

Santa Margarita (?) oil zone. A stratum of sand carrying characteristic fossils of the Santa Margarita (?) formation immediately overlies the Tejon (Eocene) in the region of the San Joaquin coal mine in 

the Westside field, but is so closely associated with lithologically 

similar beds of the Jacalitos in the same vicinity that it has been 

mapped and discussed wjth them as zone B. The persistent stratum 

of fine blue sandy shale found throughout the Eastside field and 

known locally as the Big Blue is arbitrarily placed in the Santa 

Margarita (?) formation. The Big Blue in the Eastside field immediately overlies the uppermost Vaqueros oil zone, zone B, the top of 

which is shown in contour on the map (PL XV).
OCCURRENCE 01? THE PETROLEUM. 185

Jacalitos oil zones, zones A and B. The Jacalitos (upper Miocene) 

formation is productive throughout the Westside field except at the 

extreme south and north ends and in those wells distant over a mile 

or so from the outcrop of the sands. In other words, the formation 

is commercially oil bearing wherever it rests upon or is relatively 

near the Tejon formation the source of the oil. .The line marking 

the area of productivity of zone B in the Westside field passes somewhere near the east line of the W. -| sec. 30, T. 20 S., K. 15 E., for in 

the American Petroleum wells along the west line of this section zone 

B is unusually productive, whereas half a mile to the east, in the 

Nevada Petroleum wells, zone B is practically barren; in the latter 

wells zone D is the productive zone.

Two oil zones are recognized in the Jacalitos formation, the lower 

or zone B, which is the productive zone over the southwestern part 

of the Westside field, and zone A, situated some 200 feet above zone 

B, which carries tar sands or poorly saturated oil sands. The two 

zones are generally separated by sulphur water, the "big sulphur," 

although the most persistent sulphur water in the northern end of the 

Westside field overlies zone A. Northward in the Westside field the 

productive sands of zone B are found lower and lower in the series of 

beds; until in the northern end and at least as far south as the M., K. 

& T. wells the oil is believed to come from beds in the uppermost 

portion of the Vaqueros.

FACTORS INFLUENCING ACCUMULATION.

The influence of structure upon the accumulation of the petroleum 

varies somewhat for different parts of the field, the variation being 

due, it is believed, to the presence or absence of water beneath the oil 

zones in the various areas. In general the oil in the purple-shale 

member of the Chico (Upper Cretaceous) is accompanied by water 

in the underlying beds, and possibly also in the oil sands far down on 

the dip; under these circumstances the anticlinal theory of accumulation seems to hold good. The anticlinal theory of oil accumulation 

assumes that the oil, being of less specific gravity, rises above the 

water in porous rocks and collects at the highest possible points in 

upward folds, being there confined by impervious strata arching over 

the folds. The presence of water, according to this theory, is necessary for the accumulation of oil in anticlines." A modified form of 

the same theory is apparently applicable to certain monoclines, in 

which water is associated with oil, such as those in the Westside and 

Kreyenhagen fields, where, instead of impervious beds overlying the 

porous sands, the residual or heavy hydrocarbons that are left upon

a For a fuller discussion of this subject see The geology and oil resources of the Santa Maria oil district, 

Santa Barbara County, California: Bull. U. S. Geol. Survey No. 322,1907, pp.. 71 et seq.
186 COALINGA OIL DISTRICT, CALIFORNIA.

evaporation of the lighter substances originally in the contained 

petroleum seal 'the outcrops and hinder or prevent the escape of the 

oil from below. ... 

Where no water exists in or is associated with an oil zone, Its, for 

instance, in the deeper portions of the Westside field and in by far the 

greater part of the Eastside field, the structure apparently plays but 

a minor part in the accumulation of the oil, the presence or absence 

of the petroleum in the porous strata of the zone apparently depending 

entirely upon the presence or absence of the oil-yielding shales of the 

Tejon (Eocene) below or near the beds in question. If the Tejon is 

present under any particular sand or zone, then the abundance or 

scarcity of the oil depends largely upon (1) the proximity of the particular sand to the Tejon; (2) the state of disturbance of the underlying 

shale of the Tejon, or its relative position (whether unconformable or 

conformable) to the overlying beds; (3) the degree of porosity and 

grain of the sands of the zone; and (4) the effectiveness of the barriers 

hindering the escape of the hydrocarbons (oil and gas) from the oil 

sands.

Within the tested territory of the Coalinga district it has been 

found that the areas of Miocene sediments (either Vaqueros, Santa 

Margarita(?), or Jacalitos.) immediately underlain by the shales of the 

Tejon are oil bearing; .that the productiveness of these beds varies 

roughly inversely with their distance from the shales of the Tejon; 

that the productiveness is greatest where the Tejon occupies a position 

of angular unconformity with the Miocene sands or is more or less 

disturbed, as near the axis of an anticline such as the Coalinga 

anticline.

FACTORS INFLUENCING GRAVITY. .

The gravity of the petroleum at any point in any particular bed is 

apparently influenced chiefly by (1.) the original composition of the 

oil; (2) the thickness and composition of the media through which it 

has migrated and in which it is detained; (3) its-present or past association with water; and (4) its present distance from the outcrop of the 

oil-bearing zone or its depth below the surface. Little definite information is now available concerning the effect of many of these factors. 

It seems in general, however, that the oil loses in gravity by migration either upward through various strata, or along a particular bed, 

or downward as in the supposed migration of the oil from the upper 

shales to the lower sandstones of the Tejon; that it loses on association with water; that within certain limits oil decreases in gravity up 

the dip, owing probably to proximity to the surface, with the accompanying facilities for the escape of certain of the hydrocarbons; and 

that, other things being equal, the finer the grain of the containing 

reservoir the better the oil will retain its original quality.
OCCURRENCE OF THE PETROLEUM. 187 

EELATIONS OF WATER TO OIL.

The most important question next to that of the actual occurrence 

of the petroleum in any field is the relation of the water sands to the 

sands containing the oil. One or more sands carrying water are 

almost invariably encountered above the Miocene oil zones in the 

wells of the Coalinga district. The continuity of these sands can 

seldom be traced far, and they are believed to be for the most part 

disconnected lenses rather than far-reaching beds. An examination 

of the surface outcrops leads to the same conclusion. The contents of 

these upper water sands are believed to be surface or secondary water; 

that is, water which has percolated into them since they were tilted 

into their present position and their edges were exposed. This 

secondary water is seldom under much head, although in a few wells 

it has been known to flow with considerable energy.

One of the most persistent layers or zones of water is the one termed 

the "big sulphur," a malodorous blackish fluid met with in or above 

zone A in the Westside field north of Los Gatos Creek, and between 

zones A and B south of Los Gatos Creek. No productive oil sands 

occur above this sulphur-water sand, though one or more tar sands 

are found over it in places; it may therefore be considered the limit of 

the upward migration of the oil, at least in commercial quantities. 

A similar and fully as persistent zone of sulphur water is encountered 

immediately above the second oil zone, zone C, over a large part of the 

Eastside field. The sulphur content of these waters probably bears 

an intimate relation to the oil, for in all of the seepages in this field 

where the oil is accompanied by water the latter is heavily charged 

with sulphur.. However, not all of the sulphur springs in the region 

contain oil, so there is a possibility that the sulphur even in this "particular sand had an origin independent of the petroleum.

In all of the wells in the Westside field in which the Jacalitos or 

upper Miocene oil zone (zone B) can be recognized that-zone is 

immediately underlain by a stratum of water. For various reasons it 

is thought that in this case also the water is secondary and has come 

into the formation since the passage of the oiLfrom the Tejon (Eocene) 

into the Miocene. Except in a very small 'area in the Eastside 

field no water has so far. been reported from below the lowest 

Vaqueros oil zone (zone D) 7 which indicates almost conclusively that 

water was not the elevating force for the oil of zone'B; it also strengthens the conclusion that the water in the higher zones is surface water 

that has percolated from the outcrops in the local catchment basin, 

rather than primary water that has been in the beds since their deposition or water that has come up from below under hydrostatic pressure. 

Small quantities of water are encountered between the base of the 

uppermost or fine-grained stratum, bearing light-gravity oil, and
188 COALINGA OIL DISTRICT, CALIFORNIA.

the coarser stratum, carrying heavier oil, which underlies it in zone 

D in the region of section 6, at the south end of the Westside field.

ORIGIN OF THE PETROLEUM. *b

The oils of the Coalinga district are believed to have been derived 

from two different sources, namety, the organic shales forming the 

uppermost member of the Chico (Upper Cretaceous) and those 

described as the -upper portion of the Tejon (Eocene). It is believed 

that the oil originated from the organic matter, both vegetable and 

animal, once contained in these beds. The shales are composed in 

large part of the tests of foraminifers and diatoms, and a smaller 

number of other organisms, in such abundance as fully to warrant 

the assumption that the animal and vegetable material that must - 

have been contained in them when deposited was adequate for furnishing a quantity of hydrocarbons and other compounds more than 

equivalent to the quantity of petroleum found in this field.

The purple-shale member of the Upper Cretaceous is saturated 

with petroleum, and its interbedded sands have proved to be productive reservoirs. Practically all the free oil of this member seems 

to have collected in the sandy zones in the lower portion, none passing 

below them and little or none entering the beds overlying this member. 

The overlying beds are of dark, compact clay, moist at least surficially 

and probably throughout, which it is believed would not allow the 

escape of much oil. Thus, owing to the presence in the shale of 

zones favorable for the absorption of the oil and of superjacent beds 

unfavorable to its escape, it has been retained within the purpleshale member where it is thought to have originated. Both for this 

reason and because the uppermost member of the0 Cretaceous is 

limited to a small area in the northern part of the district we must

look to some other source for the oil occurring in the Eocene and 

higher. Furthermore, the petroleum of the purple-shale member of 

the Cretaceous is of a very different character from that obtained 

from the later beds, as will be seen upon examination of the analyses 

made by Irving C. Alien (pp. 267-272). Samples numbered 21, 23, 

and 24 were obtained from wells of the Coast Range, Coalinga, and 

Home oil companies of the Oil City a*rea, which get their oil from the 

purple-shale member of the Upper Cretaceous. All the other samples 

were from wells that do not penetrate lower than the top of the 

Tejon (Eocene). The Cretaceous oil is greenish or brownish in color, 

of light gravity, and contains paraffin, a high percentage of naphtha, 

and a very low percentage of asphaltum. The other oil of the district is distinctly an asphalt oil and is lacking in paraffin. It is 

therefore evident that there are two distinct oils in the Coalinga 

district, to which different ages and origins are to be ascribed.
CONTOUR MAP. 189

The asphalt oil affords by far the most abundant supply of the 

district and is believed to have its source in the shales forming the 

upper member of the Tejon, which are petroliferous throughout the 

district. This oil is obtained by the wells from the Miocene beds, 

which are petroleum-bearing wherever they overlie the shales of the 

Tejon. Wherever they overlie some older formation, however, their 

relative productivity varies inversely with the distance from those 

shales.

If we were to suppose that the oils of this district had some deeperseated origin and that the shales of the'upper Chico and of the Tejon 

had acted merely as channels of migration for the oil from below 

we would expect to find the shales of the subjacent Knoxville-Chico 

(Cretaceous) also acting as channels of migration, for they are 

apparently of proper consistency (clayey shale) for migration by 

diffusion. We would also expect to find them charged with oil, 

their interbedded sandstones productive, and the Miocene formations 

overlying them containing at least as much oil as, if not more than, 1 

the same formations overlying the Tejon. But these postulated 

conditions concerning the Knoxville-Chico (Cretaceous) do not exist.. 

In all that part of the district in which the purple shale, the uppermost 

member of the Knoxville-Chico, is not present the Cretaceous shales 

and sands have been examined carefully in outcrop, and wells have 

been drilled, into them in several places, but no indications of 

petroleum were found. Beds of Miocene age do not occur in 

contact with the petroliferous member at the top of the Chico. 

Where Miocene (Vaqueros, Santa Margarita(?), Jacalitos, and Etchegoin) sands overlie the Cretaceous in a position analogous to that of 

the Miocene overlying the Tejon (Eocene) these sands yield oil only 

when situated comparatively near the Cretaceous-Eocene contact. 

This is most significant, indicating that the Cretacous did not yield 

the oil, but that, as would be expected, the oil, after passing from 

the Eocene into the Miocene, has migrated for a short distance along 

the strata of the Miocene out over Cretaceous beds. Further negative evidence pointing to the origin of the oil in. the upper members 

of the Chico and the Tejon is presented by the fact that there are no 

faults of consequence within the productive area along which migration from depths could have taken place.

CONTOUR MAP OF THE COALINGA FIELD. 

EXPLANATION.

The contour map of the Coalinga field (PI. XV) shows the topography, geologic structure, boundaries of the more important geologic 

formations, and certain details of culture, such as towns, section lines, 

property lines, a few roads, and oil wells. The structure in the pro-
190 COALINGA OIL DISTRICT, CALIFORNIA.

ductive territory is indicated by contours showing the distance above 

(marked +) or below (marked ) sea level of the base of the 

Big Blue or top of zone B in the Eastside field, and of the top of

. zone Bin the Westsidefield. The 

e ? contour "interval is 100 feet. By

a; f "

mean's of this map the direction 

and amount of dip of the strata in 

the oil-bearing formation may be 

calculated for any point in the 

field, and the depth to the various 

productive sands or zones may be 

approximated for most parts of the 

territory. (See also figs. 7, 8; Pis. 

XVI, XIX, XX, XXI.)

USE OF THE MAP.

Suppose it is desired to find the 

probable depth below the surface 

of the first productive sand at the 

middle of the north line of the 

SE. i sec. 24, T. 20 S., K. 14 E. 

Examination of the map will show 

that this point lies approximately 

on the underground contour line 

marked " 500;" that is, the top 

of zone B is about 500 feet below 

sea level here.

A close approximation of the elevation of the point may be had 

by looking up the elevation for 

the nearest derrick (see list, p. 248), 

which happens to be Claremont 

No. 4; elevation 792 feet, and calculating the difference in elevation, 

say 22 feet lower, either by the 

eye or with an aneroid barometer. 

The distance from the surface to 

the top of zone B is therefore 500 

feet plus 770 feet, or approximately 1,270 feet; and as zone B 

is the uppermost productive zone 

for this part of the field that distance is the one desired.

Again, suppose it is desired to find the depth to the main commercially productive zone at the center of sec. 5, T. 20 S., R. 15 E,
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XVI

Horizontal and vertical scale

200 400 600 600

HYPOTHETICAL SECJON ALONG LINE B-B' ON CONTOUR MAP, PLATE XV.
U. S. GEOLOGICAL SURVEY

REGULARLY DIPPING BEDS OF SANTA MARGARITA (?) AND JACALITOS FORMATIONS ON NORTHEAST 

Looking north from ric 3 on which the Standard Oil Company old camp is situated. Note steep slopes eroded in soft sed

attendant upon operations. Photograph by Ralph Arnold
U. S. GEOLOGICAL SURVEY 

Axis of Coahnga 

VIEW LOOKING SOUTHEAST DOWN PLUNGING AXIS OF COALINGA ANTICLIN

Note Pleasant Valley and Reef Ridge in distance on the right, the sky line of Kettleman Hills in the center, and low a

distance. Photograph by Ralph Arnold.
CONTOUR MAP. 191

Proceeding as before, it is found that the depth of the uppermost 

zone is about 1,460 feet below sea level and that the elevation of the

ico fossils ""

ITICLINE CANVON

Coarse sandstone 

Fossils

6. Soft gypsiferous 

sandstone

c. Soft sand, pebbly 

and hard layers

d. Soft bluish and 

grayish shale

, Pebbly sandstone

- Fossils

I/Tine, thin- bedded 

\ sandstone

Soft shale

ebbly sandstone 

Soft shale 

Pebbly sandstone

k. Soft blue shale 

I. Brown sandstone 

m. Soft blue shale

1410-foot hill '

n. Coarse brown and 

gray sandstone

Soft pebbly sandstone with 

harder sandstone above 

P- Soft blue shale

y. Pebbly gray sandstono

Etchegoln

point is about 950 feet above sea level, or that the top of the uppermost zone is about 2,410 feet below the surface. It will be found,
192 COALINGA OIL DISTRICT, CALIFORNIA.

however, by reading over the text referring to this part of the field 

that the most productive zone is zone D, which lies from 300 to 450 

feet below the top of the upper productive zone (zone B) in this 

region. Therefore the distance to the top of the commercially productive zone will be 2,410 feet plus 300 to 450 feet, or between 2,710 

and 2,860 feet.

Suppose it is desired to find the dip of the beds in the NW. J sec. 

23, T. 19 S., R. 15 E. An examination of the contours shows that 

the beds are dipping a little east of southeast (or striking a little 

north of northeast), and that the dip is about 850 feet for half a 

mile or about 32.5 feet per hundred feet at right angles to the strike. 

. The south and east components of this dip may be calculated by 

measuring in these directions instead of directly down the dip of the 

beds, which is always at right angles to the direction taken by the 

contours.

BASIS OF THE CONTOUIl MAP.

The section lines and other culture marks were determined by 

E. P. Davis, of the United States Geological Survey. The log of nearly 

every well in the field either finished or sunk any considerable distance 

on October 15, 1909, was used in the determination of the underground structure and the compilation of the data concerning the oil 

zones. All the obtainable surface evidence of dip, strike, and occur- 

. rence of petroleum was also used in the preparation of this map. 

Where the surface and the well-log evidence were at variance the 

latter was usually followed. In unsymmetrical features like the 

Coalinga anticline and Coalinga syncline the plane of the axis of the 

fold is not vertical, and therefore the anticline'as indicated by the 

contours showing the underground position of certain zones does not 

lie directly under the trace of the same anticline or syncline on the

surface.

DIFFICULTIES OF PREPARATION AND DEGREE OF ACCURACY.

After all the logs had been carefully plotted on a uniform scale 

it was found that the greatest obstacle to overcome in the preparation 

of the contour map was the difficulty of correlating the strata from 

one well to another and from one part of the field to another. The 

difficulties of such correlations are doubtless familiar to anyone who 

has tried to work out the underground structure of any of the California fields. It must be said, however, that the structure in the 

Coalinga district is more regular and the conditions more favorable 

for a successful study and mapping of the underground geology than 

they are in any of the other California fields so far examined by the 

senior author, not excepting the Santa Maria field, which was studied in 1906 and of which an underground contour map was prepared.*

a Bull. U. S. Geol. Survey No. 322, PI. X.
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XIX

Horizontal and vertical scale

ZOO O ZOO 4-00 6OO 800 1000 FEET

HYPOTHETICAL SECTION ALONG LINE C-C' ON CONTOUR MAP, PLATE XV.
U. S. GEOLOGICAL SURVEY

BULLETIN 398 PLATE XX

Tar, gas,and dry oil sand Water sand

Horizontal and vertical'scale

200 4OO 600 BOO

HYPOTHETICAL SECTION ALONG LINE D-D' ON CONTOUR MAP, PLATE XV.
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXI

Surface of ground

Horizontal and vertical scalezoo 400 -600 . 800

HYPOTHETICAL SECTION ALONG LINE E-E' ON COMTOUR MAP, PLATE XV.
OIL CITY FIELD. 193

The effort has been made to delineate on the present map all the 

details of structure consistent with the use of the well logs as confidential information, and to supplement these details by showing for 

the untested areas what seem to be most probably the conditions of 

underground structure. Within the untested areas the underground 

contours are of course only hypothetical and are shown by broken 

lines.

Regarding the degree of accuracy, it may be stated that the exact 

elevations of practically all the wells in the field were used in the 

preparation of the map. The well logs are assumed to be accurate 

to the usual degree that is, ordinarily to the length of one "screw," 

or about 5 feet. The factor of error for the developed territory is 

therefore small, but necessarily increases with th.e distance away 

from the drilled ground. Future development will add much to our

knowledge of this field and will show the inaccuracies of the contouring as here presented, but it is hoped that the benefits which 

may accrue to the operators from a knowledge of the general structure of the field will compensate in a measure for the errors in detail 

which are to be expected in a map based on incomplete data.

DETAILS OF THE PRODUCTIVE AREAS. 

OIL CITY FIELD.

LOCATION.

The Oil City field occupies the southern part of sec. 17 and the 

northern part of sec. 20, T. 19 S., R. 15 E. The conditions in the 

territory immediately south of Oil City, in the southern part of section 20, which lias been tested but found to be poorly productive, will 

also be discussed here with the Oil City field. The Coalinga Oil Company and the Home Oil Company are now the only producers in the 

Oil City field.

GEOLOGY AND STRUCTURE.

The Oil City field is situated along the east side of the belt of shale 

and interbedded sands of the uppermost member of the KnoxvilleChico (Cretaceous), which has been often referred to as the purpleshale member, the oil being obtained chiefly from the sandy zones in 

the lower portion. The proved productive ground occupies the 

same general relation to the plunging Coalinga anticline as the 

productive territory farther southeast in section 28 that is, it is 

on the more gently inclined or northeastern flank of the fold. 

Surface dips of 50° to 90° and even dips overturned past the vertical 

occur throughout the area along the southwestern limb of the anticline, while a surface clip of 32° is the maximum for the northeastern 

limb. The well logs indicate a relatively constant dip of about 26°

88170 Bull. 398 10 13
194 COALINGA OIL DISTRICT, CALIFORNIA.

(42 to 44 feet per hundred feet) southeastward down the axis of the 

anticline and relatively a somewhat steeper dip in the beds immediately north of it in the productive territory.

GEOLOGY OF THE WELLS.

The wells start either in the upper portion of the purple-shale 

member of the Cretaceous or in the lower portion of the Tejon (Eocene) and continue in brown, black, and blue shale to the bottoms, 

except where they pass through the oil sand. From one to three 

sands are penetrated. The first is from 4 to 15 feet thick and yields the 

lightest oil, which is amber-colored and which runs as high as 48° 

Baume in gravity; gas is also reported from the first sand in other 

wells, and in still others it is dry. The second and third sands comprise a zone 60 to 100 feet thick, which is petroliferous throughout 

almost its entire distance in some of the wells, while in others the 

two sands are separated, the upper usually running from 15 to 20 feet 

thick and the lower from 40 to 60 feet.

A section of the second and third sands in the productive area is as

follows:

Section of second and third oil sands, Oil City area.

Feet.

Hard sand .............................. '. .................................. 4

Soft pay sand................................................................ 15

Very hard sand.............................................................. 6

Alternating hard and pay sands.............................................. 47

72

All the s^nds are comparatively fine grained. The oil usually 

comes from the softer sands and the lower sand is generally the most 

productive, although it is entirely unproductive in some of the wells. 

The wells vary in depth from 300 feet up to nearly 1,700 feet, and the

productive zone is reached at depths varying from about 250 to 

1,500 feet. The southern part of sec. 20, T. 19 S., R. 15 E., has been 

pretty thoroughly tested and, though most of the wells have yielded 

more or less oil, they were not deemed profitable enough to warrant 

continuous operation. The following log of a typical well in the 

abandoned territory will show the general character of the Tejon 

formation for this part of the area:

Log of Phoenix Oil Company's well No. 3, in the SE. $ sec. 20, T. 19 S., R. 15 E.oFeet. 

Pink shale.................................................................. 300

Sand with water.............................................................. 330

Dark-colored shale........................................................... 420

Sand with sulphur water and oil............................................... 440

Dark-colored shale........................................................... 500

White clay shale............................................................. 520

"Watts, W. L., Oil and gas yielding formations of California; Bull. California State Min.' Bur. No. 19, 

1900,p. 140.
OIL CITY FIELD. 195

Feet. 

Oil sand..................................................................... 535

Shale....................................................................... 540

White shale.................................................................. 560

Oil sand...................................... ^............................. 575

This well is said to have yielded 50 to 60 barrels of black heavy oil 

(10° to 12° B.) for a short time. This low gravity is accounted for 

by the disturbed condition of the strata which the well penetrated, 

it being located directly on the anticline and just above an oil seepage 

in the canyon. . 

Well No. 2 of the Phoenix Oil Company, located about 300 feet 

west of No. 3, struck the sand at a less depth but yielded less oil. 

No. 1 went to 1,300 feet, but being southwest of the anticline never 

produced. The log given above and the conditions described are 

characteristic of most of the test wells put down in this area. The 

following are the companies that have operated here south of Oil City:

Blue Goose Oil Company, E. £ NE. -J sec. 20; well No. 1, depth, 2,200 feet, through 

brown and blue shale; no oil, but much water; abandoned.

California Oil and Gas Company, SE. \ sec. 19; well No. 1, formation principally 

shale; abandoned. Same company has a well in the SW. \ sec. 20, also abandoned.

Crescent Oil Company, SE. \ sec. 20; well No. 1, depth, 900 feet; little oil at 770 

feet; gravity, 11° Baurne".

Mutual Oil Company, SE. \ sec. 20; well No. 1, depth, 1,800 feet; abandoned.

New York Oil Company, SW. \ sec. 20. Well No. 1, depth, 1,000 feet, all in brown 

shale; no oil; abandoned. Well No. 2, depth, 2,200 feet, in brown shale with few hard 

sand layers; no oil; abandoned.

Selma-Oil Company, SE. £ sec. 20; well No. 1, depth, 1,742 feet; little oil sand.

Zenith Oil Company, SE. i sec. 20. Well No. 1, depth, 2,380 feet. A little oil 

sand at 1,735 feet yielded 10 barrels a day of amber-colored oil, 38° to 42° Bauni6 

gravity. Later it was drilled deeper and struck a large quantity of salt water which 

rose within 300 feet of the top of the hole. The oil sand in this well is probably the 

same as the uppermost sand in the productive Oil City area. The occurrence of salt 

water below this is suggestive of "bottom" or "edge" water for the lower sands of 

the Chico oil zone. Well No. 2, same as Selma No. 1 (?).

PRODUCT.

The production of the wells in the Oil City area varies from the 

initial output of one well said to have been 700 barrels of oil per day 

for a short time to the daily run of certain others, which now will 

average not more than 4 barrels per day. In several wells the oil is said 

to have flowed over the top of the derrick when the oil sand was first 

penetrated, as a result of gas pressure, which soon subsided. All the 

wells have to be pumped after a short initial period of spontaneous 

flow. The average daily production at present is about 20 barrels 

'per well. The average normal rate of decrease per well for the field, 

disregarding the rapid decrease from the initial production, has been 

between 15 and 20 per cent per year since 1900. The productiveness 

of the wells increases down the nose of the anticline toward the south-
196 COALINGA OIL DISTRICT, CALIFOKNIA.

east, especially near the axis of the flexure. This is shown by the 

fact that wells No. 3 of the Home Oil Company (the original Blue 

Goose well) and No. 7 of the Coalinga Oil Company have been among 

the best producers in the group.

.The gravity of the oil varies from as high as 42° to 48° Baume, of 

which grades there are only small amounts of oil, said to come from 

the uppermost sand in some of the wells (5 gallons of 48 ° oil from one 

well), to the usual run, which tests between 33° and 34° Baume. 

There is apparently little variation in gravity between the wells up 

or down the dip or along the strike. The oil is greenish to brownish 

in color and shows little viscosity. It is a paraffin oil and very different from the oil that occurs in the oil zones in the Miocene.

EASTSIDE FIELD. 

PEERLESS BRITISH CONSOLIDATED T. C. AREA.

LOCATION.

This area comprises that part of the Eastside field which includes 

the northeastern portion of section 21 and the northern part of 

sections 22, 23, and 24, extending to the line between Tps. 18 

and 19 S. at the north end of the area mapped. The companies operating in this area are the Coalinga Peerless, Camwell, Good Luck, 

British Consolidated (formerly California Diamond), Lorene, T. C., 

William Graham, Imperial, Bowling Green, and California Oilfields 

(Limited).

GEOLOGY OF THE WELLS.

All the wells in this area start down either in the Santa Margarita (?) 

(middle Miocene) or the Jacalitos (upper Miocene) formation between the top of the Big Blue and the base of the Etchegoin. They 

all penetrate to, and some of them entirely through) the VaqueiOS 

(lower Miocene) formation, which includes the oil-bearing zones, 

B, C, and D, of this < part of the field. The variation in the beds 

penetrated is rapid, as the logs indicate, and it is seldom possible to 

trace a single stratum except the Big Blue more than one-eighth or 

one-fourth mile.

The map (PI. XV) indicates by contours the distance of the base of 

the Big Blue above or below sea level. The Big Blue varies in thickness in the wells, if the distance penetrated be counted as equivalent 

to the thickness, from about 260 feet at the western edge of the area 

to over 350 feet in deeper wells toward the east. In fact, one of the 

deep wells disclosed a continuous shale formation for about 640 feet, 

but it is not believed that this entire thickness is included in the Big 

Blue farther west. In the region of section 2 the Big Blue and its included or equivalent red beds and sandy layers are penetrated for 

about 600 feet in the wells. One of the unique characteristics of the
EASTSIDE FIELD. 197

Big Blue for this area and also for nearly all of the Eastside field 

consists of the red-shale layers which are at various points interbedded 

with the blue variety. These red shales are well shown in outcrop in 

sees. 3 and 10, T. 19 S., R. 15 E., where, owing to their peculiar tints, 

they may be seen for a distance of several miles. The red shale consists almost entirely of comminuted serpentine, which is naturally 

green but is turned red by the oxidation of the iron, of which serpentine contains a relatively high percentage. The red shale appears 

prominently on the sumps, where it forms brilliant coatings as the 

material is dumped from the bailers.

Water sands from 20 to 175 feet thick are found just above the Big 

Blue from the western part of the NW. | sec. 22 eastward to the deepest wells. Lenses of water sand are also reported in the Big Blue 

from the middle of section 14 eastward.

Seashells are another characteristic of the logs of this part of the 

area. They occur from about 120 feet above the Big Blue in the 

Peerless area to 230 feet above it in the wells in section 12. Some of 

the-deeper wells also show a layer of seashells about 530 feet above 

the Big Blue.

A more or less persistent zone of sulphur sands lie from 20 to 180 

feet above the first productive zone, zone B, but is not reported in all 

the wells. In the region of section 2 sulphur water is usually encountered within 50 feet below the bottom of the Big Blue. Sulphur water 

also occurs below the productive sands in two of the wells only, while 

certain of the Peerless wells are said to yield no water whatever. These 

facts clearly indicate that the water occurs in more or less isolated 

lenses of sand, similar, in a general way, to the lenses carrying the oil.

Between the base of the Big Blue and the second productive oil zone 

(zone C) there is about 350 feet of dry sand, shells, and, just above the 

oil sand, some blue or brown clay or shale layers, the last sometimes 

carrying oyster shells. These last are often interbedded with dry or 

poorly saturated oil sands (zone B, in part). The thickness of the 

strata intervening between the Big Blue and the top of zone C reaches 

450 feet in the deeper wells farther east down the dip.

Very little regularity exists in the oil zones, as is shown by the well 

logs. The productive beds (zones C and D) consist of alternating 

coarse sands, fine gravels, blue and brown shale, and shells, with coarse 

gravel at the base of zone D. The productive measures are usually 

about 225 feet through that is, from the top of the first productive 

sand to the brown shale of the Tejon (Eocene) and, though they comprise both zones C and D, a ssparation. of the two is not possible in 

many of the wells. The total thickness in the wells from the base of 

the Big Blue to the brown shale of the Tejon is a little over 600 feet. 

Toward the northern part of the area under discussion the strata
\

198 COALINGA OIL DISTRICT, CALIFORNIA.

below the base of the Big Blue thin to about 500 feet in the wells, only 

the lower 150 feet of this being productive.

Various names have been applied to certain individual sands that 

have been traced for short distances throughout this area. Among 

these is the Sauer Dough sand, which is the uppermost sand in some 

of the wells along the western edge of section 22. It is usually about 

10 feet thick. About 40 feet below the Sauer Dough is a 40-foot sand 

known as the Pulaski sand. A careful comparison of the logs in the 

area shows that these two sands, and others also to which local names 

have been given, are not traceable for any great distance, although 

the names have been applied to various strata in wells over other 

parts of the Eastside field.

PRODUCT.

'Nearly all the wells in this area have been drilled since 1904, so 

that data concerning decrease in production are rather meager. The 

production of the wells varies from about 25 to something like 700 

barrels, the production increasing down the dip, other things being 

equal. The T. C. well in section 2 is said to have had an initial production of 400 barrels a day, but the yield has now fallen to 100 or 

150 barrels a day, which is believed to be a fair initial average of what 

would be encountered over most of the area in properly handled wells 

1,500 feet or more in depth. The average production for the wells in 

the area is about 125 barrels per day. The yield depends largely on 

the handling of the well, for holes going down under practically the 

same conditions give quite different results under various managements. One well which had an initial production of 200 barrels now 

yields only 20 to 25 barrels per day. This decrease is probably due not 

entirely to natural causes but to a sanding up of the hole. The gravity of the product from this area varies from 18° to 24° B. So many 

sands are perforated that it is usually impossible to tell the gravity of 

the oil from any particular one. However, the uppermost important 

productive zone (top of zone C) in the area is believed to yield oil of 

between 20° and 21° B. gravity. The next sand, say about 80 feet 

below the first, yields oil of 24° B. gravity, or possibly slightly better, 

while the lowest sand (base of zone D) which rests directly on the 

shales of the Tejon formation produces oil of 18° or 20° B. gravity.

Some of the wells yield a little water with the oil, and it is claimed 

by some drillers that this water comes from the oil sands, but it is the 

belief of the writers that in nearly every instance the water has leaked 

in from the surrounding water sands and is not obtained directly from 

the oil sands. Relatively little sand is yielded by the wells after the 

initial period of production, but much trouble has been encountered 

in some of the deeper wells owing to the gas pressure forcing the sand 

in from the bottom. Gas accompanies the oil in all the wells and is
EASTSIDE FIELD. 199

N

also encountered alone in isolated pockets, usually above the productive zones. Other conditions being the same the greater gas 

pressure occurs in the deeper wells.

TECHNOLOGY.

The best success in shutting off the water in this area has been in 

landing the casing in a blue shale just below the sulphur-sand zone. 

Surface waters are shut off above this with a larger casing, but the 

purity of the oil depends entirely upon the careful handling of the 

lower waters immediately overlying the oil sands.

STANDARD CARIBOU BRITISH CONSOLIDATED AREA.

LOCATION.

The area described in this section covers the northeastern portion 

of section 27, the southern part of sections 22, 23, and 24, all of sections 25 and 26, and the northern part of sections 35 and 36. The 

following companies operate in this area: California Oilfields (Limited), Standard, Caribou, Associated, Twenty-Two, Record, Pittsburg, 

Octave, Sauer Dough, Porter, British Consolidated, and Boston and 

California.

GEOLOGY OF.THE WELLS.

The wells in this area, as in the area farther north, start down in 

the Santa Margarita (?) and Jacalitos (upper Miocene) sands and 

shales between the' top of the Big Blue and the basal Etchegoin. In 

the area where sections 21, 22, 27, and 28 meet the Big Blue is 

about 220 feet thick in the wells, increasing toward the eastern limit 

of the productive territory to about 320 feet. Red shales are reported interbedded in the Big Blue in nearly all of the wells throughout the area. These red beds seem to thicken and become relatively 

more prominent in the deeper wells toward the east and north. Some 

white and light-blue shale layers also occur in the same zone, and in 

the western part of the area gray and brown dry sands are encountered above it. From a point a short distance west of the middle of 

the line separating sections 22 and 27 the same sands contain water 

at various distances above the shale.

All of the strata from the base of the Big Blue to the top of the 

Tejon (Eocene), embracing a distance in the wells of 620 to more 

than 800 feet, are more or less petroliferous throughout this area. 

Three oil zones may be defined within these limits. The first zone 

(zone B, the top of which is shown in PI. XV) begins immediately 

at the base of the Big Blue and is from 100 to 180 feet thick. The 

greater thickness occurs in the deeper wells. In the western part 

of the area zone B consists of dry sands, dry oil sands, or poorly 

saturated oil or tar sands; farther east it is commercially productive
200 COALINGA OIL DISTRICT, CALIFORNIA.

in some of the deeper wells but not in all. Where productive, as in 

the western part of section 26, the gravity of zone B oil is about 14° 

to 16° B. Below zone B and between it and zone C the strata are 

largely shale and dry sand.

The second and third zones (zones C and D) are closely related, 

the second being the uppermost important producer. over most of 

the area. Zone C consists of medium-grained sand yielding lightgravity oil (24° B. or better), is about 100 feet thick, and begins 

about 400 to 480 feet below the base of the Big Blue. There are 

usually from one to four productive sands in this zone. The lowest 

productive zone (zone D) rests directly on the shale of the Tejon 

(Eocene), is very coarse, consisting of pebbly sand or fine gravel, 

and is usually the best producer as regards, quantity, although the 

oil is of but 20° to 23° B. gravity.

Sulphur water overlies zone B in the area north of a line drawn 

south of Caribou Nos. 11 and 10. Fossil shells are rep'orted at the 

base of the Big Blue in some of the wells, while in others, as in the 

region farther north, they occur about 450 feet above the base of- the 

Big Blue. The seashells in some of the Caribou wells are found just 

above the oil sand and associated with it.

Water is now causing trouble in the region of the SE. £ sec. 22, T. 

19 S., R. 15 E.; the source is believed to be sands occurring in the 

Vaqueros between zones B and D. Some of the operators lean to the 

belief that this water has been let into the sand by faulty handling of 

the wells; others believe that the water was originally in these sands, 

and to this theory the writers are inclined.

PRODUCT.

Most of the wells in this area also have been begun since 1904, so 

that figures for decrease in production are meager. All of the productive sands are perforated in many of the wells, so that it is often 

impossible to tell the production or gravity of any one sand. However, the general features of variation are known and will be indicated. The initial production in the wells varies from about 150 to 

1,600 barrels per day. The average production at present is somewhere near 400- barrels. The best producers, as a rule, are among 

the deeper wells, although for one which is well up on the dip (SE. £ 

sec. 21) an initial yield of 1,500 to 1,600 barrels per day is reported. 

This well obtained 200 barrels per day from the upper sands, but 

was lowered into the deeper sands, where it made its phenomenal 

record. Besides the one mentioned, there are at least two other 

wells in the area that have produced more than 1,000 barrels a day. 

The average decrease in production for three years has varied from 

about 20 to 40 per cent, but some wells are said to have held out 

much better than this.
EASTSIDE FIELD. 201

The gravity of oil in this area varies from 16° to about 24° Baum6. 

The heavy oil comes from the upper sands (zone B), which are 

usually more productive in the deeper wells. A well in the W. % 

sec. 26 is said to have yielded 600 barrels of 15° or 16° oil from 

zone B when first drilled. The middle zone (zone C) produces oil of 

about 24°, while the lower, coarser, but generally more productive 

sands (zone D) yield oil of 21° to 22° B.

Gas occurs in.practically all of the wells. In some of them there 

is sulphur, but most of them yield a good gas free from this element. 

The influence of one well upon the gas pressure in another is often 

very marked. A certain well, for instance, dropped off more than 

25 per cent in production when another well within 300 feet of it 

was brought in.

STANDARD-CALIFORNIA OILFIELDS (SEC. 27) AREA. 

LOCATION.

This area includes the eastern part of section 28 and the western part 

of section 27, excluding the portion along the south line of section 27. 

The Standard and California Oilfields (Limited) are the only companies 

operating in this area.

GEOLOGY OP THE WELLS.

All of the wells start down in the Santa Margarita (?) (upper middle 

Miocene) and Jacalitos (upper Miocene) formations, above the top 

of the Big Blue and below the base of the Etchegoin, which usually 

include alternating sands and shales with occasional water sands. 

These water sands as a general rule are in the form of lenses and can 

seldom be traced in the wells for more than an eighth of a mile.

The Big Blue maintains a pretty uniform thickness of about 250 to 

300 feet throughout practically the whole of this territory. In the 

wells along the middle of the line between sections 27 and 28 there is 

a fairly persistent stratum of water sand immediately overlying the 

Big Blue. There are other water sands above this lowest one in some 

of the wells, but none that can be traced far. An interesting stratum, 

encountered in the wells beginning in the vicinity of the California 

Oilfields, section 27, No. 20, and extending down into the northern 

part of section 34, is known as the St. Paul sand. It lies about 830 

feet above the base of the Big Blue, or from about 150 to 600 feet' 

below the surface. It is about 30 feet thick and hard, but is believed 

by some of the operators to be capable of yielding 50 barrels of oil 

per day, though as far as known it has never been thoroughly tested. 

This occurrence is rather puzzling, as there are no other oil sands 

within several hundred feet of it and the origin of its petroleum is 

difficult to explain.

The oil-bearing formation in the area under discussion extends from 

the base of the Big Blue for about 655 feet as measured in the wells
202 COALINGA OIL DISTKICT, CALIFORNIA.

down to the top of the brown shale of the Tejon (Eocene). This 

distance between the base of the Big Blue and the brown shale is 

apparently regular over that part of the area which has been tested. 

The deepest wells have not penetrated the entire thickness of the oil 

sands, so that the exact thickness of the sands is not known for wells 

far down on the dip.

Three zones are recognizable in this series of productive beds. 

The first (zone B) occurs at the base of the Big Blue, is about 15 to 

20 feet thick, and yields from 30 -to 50 barrels of 21° B. oil in the 

shallower wells.

The second (zone C) is about 300 feet below the top of the Big 

Blue, has a thickness of 60 feet, and produces daily from 100 to over 

1,000 barrels of 22° to 24° B. oil per well. A group of wells in the 

middle of the western part of section 27 and in the eastern part of 

section "28 produce oil of 25° to 31 ° B., the initial production of 

the wells varying from 125 to 1,900 barrels per day. "The oil from 

zone C, in this local area of unusually light oil, is kept separate in 

most of the wells, but whether or not all of the yield from the big 

producers in this light-oil area comes from zone. C is not known. 

The sands in- this light-oil zone are finer grained than those in the 

zone above or the zone below. . -

The third oil zone (zone D) consists of coarse, pebbly sands and 

fine gravels and extends practically from the top of the brown shale 

of the Tejon upward for over 100 feet. Oil-bearing sands are found 

at practically all horizons in one well or another from the base of 

zone C to the top of zone D, so that a separation of the two is necessarily more or less arbitrary.

PRODUCT.

The wells in this area have all been drilled since 1902. The product of those wells deriving their supply from the upper sands (zone 

B) varies from 30 to 50 barrels per day of 21° B. oil. The middle 

zone (zone C) yields from 125 to 1,900 barrels per well per day, the 

gravity ranging from 24° to 31 °. One well which had an initial production of 1,900 barrels per day in 1904 dropped to 1,300 barrels per 

day after one and one-half years. Several of the wells yield on an 

average 300 to 400 barrels per day, while another group averages but 

125 barrels of 26 ° B'. oil. The third zone (zone D) yields oil of 22 ° to 

23 ° B. It is the best producer, as far as quantity goes, in this part of 

the field. The better gravity and greater production in this particular area are believed to be due to the position of the wells adjacent to 

the axis of the anticline, where the shales of the Tejon (Eocene), from 

which the oil is derived, are much more fractured and where, in consequence of this fracturing, the oil is permitted to migrate more 

easily and with less loss in quality into the overlying porous sands.
EASTSIDE FIELD. 203

The concentration of the oil within the Tejon, before its emigration, 

was also doubtless accentuated along the anticline by the action of 

the water which is associated with or immediately underlies the oil 

sands.

The presence of the light oil in the finer sediments is believed to be 

clue to the fact that the lighter hydrocarbons can escape more easily 

from coarser- reservoirs than from fine-grained ones, so that, when 

once charged with the oil, the finer-grained sands allow it to maintain 

its original quality more perfectly than a coarse sand would. As 

would be expected, the production under the same pressure is considerably less in finer sediments than it is in coarse sands, but the 

length of productivity is consequently greater in the former than in 

the latter.

CALIFORNIA OILFIELDS (SEC. 34)-COALINGA-MOHAWK AREA.

LOCATION.

This area comprises the whole of sees. 34 and 35, T. 19 S., R. 15 E., 

and sees. 1, 2, 3, 4, 11, and 12, T. 20 S., R. 15 E. The California 

Oilfields (Limited), Kern Trading and Oil (Southern Pacific), W. K. 

Turner, Claremont, Southeastern, and Coalinga-Mohawk are the companies operating in this territory.

GEOLOGY OF THE WELLS.

As in the other areas described, the base of the Big Blue is the 

horizon shown by the contours on the accompanying map. The 

wells in the northern part of the area start down in the Jacalitos 

(upper Miocene) beds immediately underlying the base of the 

Etchegoin.. Those south of the line marking the base of the Etchegqin 

start in the sands or clays of this formation. The Big Blue in the 

wells of this area varies from 250 feet in thickness in the northwestern 

portion to about 380 feet at the southwestern border. The peculiar 

red, green, and light-blue facies of the shale, which are characteristic 

of the Big Blue in the deeper wells farther north, are also to be found 

in the deep wells in this area, especially those farthest south. In 

the northwestern portion water sands appear to be interbedded at 

the base of the Big Blue, as are also some tar and dry oil sands with 

occasional gas pockets. There are also other water sands in the 

deeper wells, an especially persistent zone occupying a position about 

600 to 800 feet above the base of the Big Blue in the wells in the 

southern part of. the area. Some of the water in this zone is said 

to contain appreciable amounts of sulphur.

The St. Paul sand of the area last described .also occurs in the 

northern part of this territory, where it is encountered in practically all 

the wells, but in none of them, so far as the writers are aware, has 

it ever been tested. Those wells -which have been put down to the
204 COALINGA OIL DISTRICT, CALIFORNIA.

brown shale of the Tejon (Eocene) indicate that the formation between 

the base of the Big Blue and this shale has practically the same 

thickness of 650 feet or thereabouts that it has in the.region to the 

north. The whole of this distance is occupied by alternating sandstones and shales, which are more or less productive in the various 

wells. The relations between the various oil sands in this area are 

not well known, but it is believed that the sequence of zones, including B, C, and D, is similar to that in the area last described. A 

10-foot oil sand carrying 17° B. oil occurs at the base of the Big Blue, 

this sand probably corresponding to the one which yields a 16° B. 

or heavier oil in section 26 and which has been correlated with zone B. 

One hundred feet below the Big Blue the second sand, possibly zone 

C, is penetrated, this being productive through about 20 to 25 feet. 

About 400 feet still farther down is the third zone (zone D), which 

is believed to rest upon the shales of the Tejon (Eocene). A thin 

layer of sulphur water is reported in some of the wells just above 

this third zone, but enough blue or brown shale intervenes to allow 

complete shutting off of the water before reaching the productive 

zone.

PRODUCT.

The wells in this area are only four or five years old, but since their 

inception they have maintained a reputation as the biggest producers in the field. The oil in these wells is usually accompanied by 

large quantities of gas under strong pressure. As an instance of their 

unusual productiveness, it is said that one well in the northern part 

of section 34 yielded about 7,000 barrels of oil in eighteen hours. The 

casing was practically all torn out by the ejection of this large amount 

of .fluid from the hole. This well is now producing but 150 barrels

per day, which indicates that the great production was due to the 

extremely high gas pressure. Another well near the center of the 

southern part of section 27 is said to have yielded 4,500 barrels of oil 

per day for some little time. This well is now believed to yield about 

3,000 barrels per day. The gravity of the oil from these big producers 

is between 23° and 24° B.

Another well in the northern part of section 34 yielded on an 

average about 1,000 barrels per day for over ten months. Still others 

of these wells run from 600 to 800 barrels per day. The CoalingaMohawk well, which penetrates but half of the oil-bearing zone 

between the base of the Big Blue and the brown shale of the Tejon, 

is said to have produced at first at the rate of 150 to 200 barrels 

of 32° oil a day. One well, which yielded 26° B. oil as long as it 

flowed, now yields a mixture of 23° B. oil when it is pumped. This 

implies that the lighter oil is probably under the greater gas pressure, and when this pressure is removed the heavy oil either forces 

back the lighter fluid or allows only a small percentage of it to
EASTSIDE FIELD. 205

enter the well. The lower zones (zones C and D) in one well are 

said to yield a stratum of 29° B. oil at the top, 22° B. in the middle, and 26° B. at the base, with an average of about 28° B.

STANDARD-STOCKHOLDERS AREA.

LOCATION.

This area comprises all of section 28 except the extreme eastern 

edge, which is described in a previous section (p. 201). The Standard 

and Stockholders oil companies are the only operators.

GEOLOGY OP THE WELLS.

The Big Blue in this territory varies from about 200 to 230 feet thick 

in the wells. A layer of water sand is found just above it in the eastern 

part of the area, and one or two lenses of water sand have been 

reported as occurring'in the Big Blue itself. The oil strata extend 

intermittently from the base of the Big Blue for about 655 feet to 

the brown shale of the Tejon (Eocene). The first 400 feet of the productive measures consists of alternating gas sands, oil sands, dry 

sands, and tar sands interbedded with shales and clays and has been 

correlated with zone B, although it is believed to comprise not only 

the zone B of the areas toward the east but the strata to the top of 

zone C. In the northwestern part of the area this upper zone is 

more or less productive, some of the wells which produced from it 

alone yielding from 10 to 30 barrels per day of 20° B. oil.

One or two persistent layers of water sand occur from 50 to 100 

feet above the base of zone B, or above the top of the second or lightoil zone, zone C. Enough blue or brown shale intervenes between 

this water sand and the productive beds below to permit shutting off 

the water. Big oyster shells are reported in some of the wells just 

above the second zone, these probably coming from the same layer as 

that yielding the oysters in the Vaqueros formation on the Laval 

grade. Zone C consists largely of fine sand from 20 to 60 feet thick and 

yields oil of about 21° to 22° B. gravity. The third zone, or zone D, 

consists of coarse sand\o gravel and begins about 100 feet above 

the brown shale of the Tejon (Eocene). It is productive through its 

entire depth, and yields more than any other of the zones in this 

group of wells. The daily production varies from 40 to 300 barrels 

per well of 18° to 22° B. oil.

Toward the axis of the Coalinga anticline the strata are more or 

less irregular on account of the 'steep dips which are developed by 

this profound fold. The logs of the wells along the axis are irregular 

and indicate varying conditions in both the dip and the productiveness of the beds. Water is also-more troublesome in these wells, 

owing, it is believed, to the disturbed conditions of the elsewhere 

impervious beds that surround the water sands. There is very little 

gas in the sands toward the western edge of this area.
206 COALINGA OIL DISTRICT, CALIFORNIA.

PRODUCT.

The wells in the area under discussion are the oldest in the Coalinga 

district except those in the Oil City area, and many of them have produced continuously since their inception. The first zone (zone B) 

yields up to 30 barrels per day of 20° to 22° B. oil; the second (zone 

C) yields a somewhat lighter oil, from 21° to possibly 23° B., and 

the third (zone D) produces as high as 300 barrels of 18° to 22° oil. 

Some of the wells yield sand from the lower productive beds, and 

water is also mixed with the oil in some of the wells in the broken 

formation near the axis of the anticline. In none of the wells in 

this area is the water believed to come from the bottom of the oil 

zone.

WESTSIDE FIELD. 

CALL CONFIDENCE AREA.

LOCATION.

This area is in the southwest corner of T. 19 S., R. 15 E., and comprises the territory controlled by the following companies: The California Oilfields (Limited), Call, Keystone, Ajax, -ZEtna Petroleum, 

Commercial Petroleum, Maine State (formerly the Guthrey), Confidence, W. M. & M. (formerly California Diamond), Empire, American 

Petroleum, and Kern Trading and Oil. The wells are on the southeastward-dipping monocline of the Westside field at a point where 

the strike of the beds begins to bend from northeastward to eastward around the axis of the Coalinga syncline.

GEOLOGY OF THE WELLS.

All the wells start down in the soft shales, sandstones, or gravels of 

the basal Etchegoin, or in the upper Miocene beds immediately underlying this. Toward the western part of the area the wells apparently penetrate only through the upper Miocene formations. On the 

western side, that is, in the deeper wells of the Call, California Oilfields (Limited), and Commercial Petroleum, the wells apparently 

reach sands in the lower Miocene (zone D) that are lacking or have 

not been reached in the wells in the western part of the area. .

Zone B, the depth of which below the surface is indicated by contours on the map (PL XV), will first be described. Toward the 

western part of the area it contains the productive sands and is 

found from about 650 to 1,050 feet below the surface. The oil in this 

zone is apparently under considerable gas pressure, as in nearly all of 

the wells, even the shallower ones, the oil rises a considerable distance in the casing when the sand is first penetrated. The sand in 

the shallower wells varies from 10 to 20 feet in thickness, thickening 

toward the northeast from the region of the Kern Trading and Oil
WESTSIDE FIELD. . 207

territory. The sand is medium grained to coarse and soft, and the 

wells producing from it yield large quantities of sand with the oil, 

especially at first. Some of the shallower wells have been known to 

flow when first brought in. Farther east, in the vicinity of the 

eastern Confidence wells and those of the Maine State or Guthrey 

leases, the zone is apparently irregular and some- of the logs of the 

wells, although reporting a production from the horizon at which the 

sands are found farther up on the dip, do not mention the thickness 

of the sands within the zone. Guthrey No. 1, which was the biggest 

gusher of this part of the field, might be mentioned as an illustration 

of the irregularity. The behavior of this well was very unusual and 

the exact location of the sand producing the gas and oil which flowed 

so strongly at first is doubtful. Enough sand was ejected from this 

well to cover the derrick floor and the surrounding ground for over 6

feet in depth.

In the deeper wells zone B is apparently represented by two sands 

which are separated in some instances by a waxy clay. The total 

thickness of the sand in these wells runs as high as 50 feet. Still 

farther down the dip, or in the deepest wells in the area, zone B 

apparently becomes unproductive, although it yields evidences of gas 

and petroleum in small quantities. In one of the wells this zone was 

pumped for three weeks, but the operators concluded that there was 

water in it and abandoned their efforts.

About 200 to 300 feet above zone B is a zone of tar sands (zone A), 

which, as the name implies, are either dry or yield oil of heavy gravity. These sands vary in number and thickness from well to well, 

although the zone as a whole is fairly persistent over the entire area. 

Sulphur water occurs -within zone A, usually at the base of the first 

tar sand, and at some of the wells it is found at two horizons within 

the zone. The thickness of the tar sand varies from a minimum of 

10 feet in some of the moderately deep wells to nearly 100 feet or 

possibly more in those farthest up on the dip. Thicknesses also 

occasionally approach 100 feet in the deep-well area.

About 200 feet above the zone of the tar sands (zone A) is a very 

persistent stratum of water. This water is mineralized in all the 

wells and in some shows traces of sulphur. Above this water zone 

are usually one or two other water sands, the first being only about 5 

to 10 feet thick, but yielding considerable water. The second is less 

important and is apparently lacking in many of the wells.

In the deeper wells toward the eastern part of the area the most 

productive sands apparently lie below zone B and are believed to be 

in part the equivalents of the lower Miocene sands (zones C and D) 

which are the productive sands of the Eastside field. The exact relations of these zone D sands to the overlying ones are perplexing, but 

it is believed that zone D does not extend westward past the middle
COALINGA OIL DISTRICT, CALIFORNIA.

of the area under discussion, although to the knowledge of the writers 

no well has yet been put down which passes entirely through the strata 

overlying the Tejon (Eocene) in this part of the field. "Some of the 

wells have reached what they call the black or brown shale, but it 

seems likely that these brown shales may be simply petroliferous 

shales intercalated in the sands of the Vaqueros (lower Miocene). 

This lower Miocene sand zone (zone D) lies from 100 to 300 feet 

below zone B. Productive lenses are found at two or three points 

throughout the zone, but no continuous oil sands have been definitely traced between the wells.

Taken as a whole, the logs present the following features in passing 

downward from the surface: First the incoherent soil and gravel, 

then a thick series of dry gravels, sands, and shale or clay, with occasional hard sandstone shells. The first water is encountered usually 

between 240 and 500 feet. From this downward two and sometimes 

three other waters are penetrated before the tar-sand zone (zone A) 

is reached. The zone of the lower water sand or sands is often 

marked by numerous hard sand shells. After passing through zone 

A,, which varies from a few feet to over 300 feet in thickness, a 200- 

foot zone of blue shale is encountered. Below this lies zone B, which 

is characterized by medium-grained to pebbly sands, brown shales, 

and several well-defined shells. The shallower wells usually stop at 

the base of this zone, but the deeper ones penetrate some shale and 

sands from the bottom of zone B to the. top of the third zone, which 

includes zones C and D and is usually characterized by hard shells 

and medium-grained sands.

PKODUCT.

The production of the wells in this area varies from an initial output of 20 to 50 barrels in the shallower wells to 3,000 or 4,000 barrels 

in some of the deeper ones, such as Guthrey No. 1, which was a pronounced gusher when first brought in. The daily average for these 

wells runs somewhere between 100 and 200 barrels, but some of them 

average as high as 300 to 350 barrels over long periods.

The gravity of the oil runs from 14° to nearly 20°, the average for 

the shallower wells being about 16° and for the deeper wells about 

18°. The best oil apparently comes from the middle zone (zone B), 

which is believed to correspond in a general way with the light-oil 

sands farther south in the Westside field.

MERCANTILE CRUDE-S. W. & B. AREA.

LOCATION.

This area comprises the southern part of the Kern Trading and 

Oil, Confidence, Coalinga Aztec, and E. W. Risley leases in sec. 31, T. 

19 S., R. 15 E.; the Fresno-San Francisco and the northern parts of
WESTSIDE FIELD. 209.

the Cypress, Pennsylvania-Coalinga, and American Petroleum properties in the northeastern part of sec. 1, T. 20 S., R. 14 E.; and..the 

Mercantile Crude, York-Coalinga, S. W. & B., New San Francisco 

Crude, and the northern half of Esperanza in sec. 6, T. 20 S., R. 

15 E. The wells are on the southeastward-sloping monocline which 

dominates the structure of the whole Westside field.

GEOLOGY OP THE WELLS.

The wells in this area all start down in the basal Etchegoin (upper 

Miocene) clays, sands, gravels, etc., or in the Jacalitos (upper Miocene) 

beds immediately underlying these. Three more or less well-defined 

petroliferous zones are developed in this area. The top of the 

principal productive zone (zone B) is shown by contours upon the 

accompanying map (PI. XV). A description of this zone will first

be given. In the wells high up on the dip the character of the sand 

in zone B is coarse, and it usually contains pebbles the size of the 

thumb or sometimes even larger. Both immediately above and 

below the most productive part of the zone are sands in which the 

oil is heavier than that in the most productive part. The reason for 

this difference in gravity between sands so close together is not at 

present known, but it may be due, in part at least, to difference in 

grain of the sands. Farther down the dip the sand is somewhat 

thicker, but is still coarse, and in some of the wells contains shark's 

teeth. The coarseness of the sand and the gas pressure are conducive to godcl productions, and it is not unusual for wells at first to 

obtain as high as 300 or 400 barrels a day from this one sand. In 

the deeper wells the zone apparently contains but one sand, which 

is in most places underlain by a more or less persistent hard sandstone shell. The gravity of the oil in zone B runs about 17° B. and 

is apparently constant throughout the area. From 50 to 100 feet 

above zone B is a 100 to 200 foot zone (zone A) of tar sands similar 

to those encountered in the wells toward the north. This tar zone 

is thickest in the northwestern part of the area, and there it consists of one to three dry oil sands or tar sands which sometimes 

contain heavy oil and occasionally water associated with the oil. 

Eastward, or down the dip, the tar sand decreases rapidly in thickness, until in the deepest wells in the area the tar zone is represented 

by but one or two sands which never attain more than 10 or 20 feet 

in thickness. Immediately overlying zone A is a persistent stratum 

of sulphur water, which is encountered in practically all of the wells 

in 'this area and is known in general under the name "big sulphur," 

or "main sulphur." Beneath this sulphur water inmost of the 

wells is a hard sand shell, which is apparently more or less persistent 

88170 Bull. 398 10 14
210 COALINGA OIL DISTRICT, CALIFORNIA.

throughout the area. Still another sulphur water is encountered a 

little above the lower one in some of the wells, but does not appear 

to be as persistent as the "main sulphur."

Below zone B in the deeper wells is still a third petroliferous zone 

(zone D), which may correspond in part to the lowest zone in the 

area immediately north. It is penetrated by but two or three wells 

and its productiveness is more or less uncertain. In- one log this 

lower sand is mentioned as brown shale, although the same log 

shows that the casing was perforated at this point, thus indicating 

that the formation was oil bearing.

The water sands in the area are usually three or four in number, the 

uppermost being encountered at depths of 145 to about 375 feet. 

The first sand is apparently not so productive as the second, which 

yields plenty of water in many of the wells. Below the second sand 

is a third, and sometimes even a fourth, before the sulphur sand, 

immediately overlying the tar zone, is encountered.

Typical well log in Mercantile Crude-S. W. & B. area.

Feet.

Surface soil and incoherent sand and gravel, followed by harder shales, Bandstone, and gravels...................................................... 200

First water sand......................................................... 5-20

Shale.................................................................... 50+

Second water sand.

Shale, sometimes containing one or more water sands....................... 300

Gravel, more or less persistent, apparently carrying water in several of the 

wells, especially those nearest the outcrop.

Shale..................................................................... 100+

"Main sulphur" water.

The depths of the wells in this area vary from about 1,000 feet to

over 1,700 feet.

PRODUCT.

The production varies from 12 barrels in the wells farthest west to 

about 400 barrels in the deeper and more productive ones. Large 

quantities of sand usually accompany the oil, especially in those 

wells high up on the dip, and even in some of those which penetrate 

the sand at much greater depth. The gravity of the oil varies from 

13° to 17£° B., the average for the area probably being about 16°.

ZIER PORTER & SCRIBNER M., K. & T. AREA

LOCATION.

This area comprises the southern part of sec. 1, T. 20 S., R. 14 E., 

the southern part of the American Petroleum and Esperanza properties, 

sec. 6, T. 20 S., R. 15 E., and the region of sec. 12, T. 20 S., R. 14 E., 

and sees, 7 and 8, T. 20 S. ; R. 15 E. The companies operating in
WESTSIDE FIELD. 211

this area are the Zier, Ward, Seneca, Cypress, Pennsylvania-Coalinga, 

Esperanza, Shawmut, Section Seven, Coalinga Pacific, Arica (formerly 

Porter & Scribner), Brix & Buntin (B. & B.), Spinks, Coalinga Unity, 

St. Clair, Pilot, New Era, British Consolidated (formerly California 

and New York), Kern Trading and Oil (Southern Pacific), Coalinga 

National, Coalinga California, J. J. Cartner, American Petroleum 

(section 18), Nevada Petroleum (section 18), and M., K. & T. The 

wells are located on the flanks of the southeastward-dipping monocline 

which governs the structure in the Westside field.

GEOLOGY OV THE WELLS.

The wells start down in the basal Etchegoin or the soft Jacalitos 

beds immediately underlying this formation. Zone B, the one shown 

in contour on the map (PL XV), is at present the most important 

zone in this part of the field and yields the greater part of the production. In the western part of the area it varies from alternating 

sands and shales to a single bed of coarse sand 25 feet thick. The 

gravity of the oil from the zone in this part of the area varies from 

13° to 14° B. Farther east and lower down on the dip the gravity 

of the product from zone B is considerably higher, ranging from 17° 

to 18° B. The beds yielding this lighter oil may possibly not bo 

continuous with those farther west, which produce the oil of 14° B. 

gravity. On the contrary, the sands yielding the latter may possibly 

be represented in the eastern part of the area by the sands yielding 

14° B. oil which immediately underlie the 17° B. oil sand. The 

17° B. oil sand is not fine grained, but is fairly coarse, and in many of 

the wells contains shark's teeth, as it does in the area farther north. 

The zone, as indicated by logs, varies in thickness from 7 to 60 feet 

in the central part of the area. The production from a single sand 

in this zone ranges from 40 or 50 barrels up to the daily maximum of 

about 200 barrels per well. The light-oil sand appears to be missing 

in some of the wells, according to their logs, but it is believed that 

the formation is represented in the well but was overlooked by the 

driller while the hole was full of water. In the deeper wells, toward 

the eastern end of the area, zone B maintains the characteristics 

just described, varying in thickness from 8 to 30 feet, apparently 

being mixed with some shale in the thicker portion.

As in the areas farther north, zone B thickens rapidly toward the 

east until in the region of sec. 8, T. 20 S., R. 15 E., indications of 

petroleum are found throughout a vertical distance of over 1,100 

feet. Here zone B is believed to be represented by what is known as 

the third or light-oil sand of the M., K. & T. wells, which lies several 

hundred feet aboAre the most productive sands in those holes, is 

medium grained, nearly 100 feet thick, and is said to vjeld 22° B, oil,
212 COALINGA OIL DISTRICT, CALIFORNIA.

If zone B is continuous, wells between the Porter & Scribner and 

the M., K. & T. leases ought to show, a gradation in gravity from 

17° or 18° B. in the former to 22° B. in the latter, which is much 

farther down the dip. This decrease in specific gravity (increase in 

degrees Baume") down the dip agrees with the mode of variation 

found in most instances in the other California fields examined by the 

writers.

The same tar-sand zone (zone A) is encountered above zone B in 

this area, as is found in the same portion throughout most of the 

remainder of the Westside field. It varies in thickness from 20 or 

30 feet to over 100 feet, being exceedingly irregular as reported in 

the well logs, although it is on the whole believed to be thicker down 

the dip toward the east. The tar sands are usually intercalated with 

shale and are often dry, but in some wells yield a small production 

of heavy oil of about 14° B. gravity or heavier. Prominent sandstone shells are usually associated with the sands and shales of this 

zone, some of these shells being traceable from well to well, and 

one in particular, of considerable importance, has been called the 

"big shell."

Below zone B and closely associated with it is a zone of 14° or 15° 

B. oil. This zone (zone D) has been penetrated in some of the wells 

for over 300 feet and consists of alternating sands and blue and brown 

shales, the brown shales usually predominating. It is barely possible 

that this lowest shale in the deepest wells is Tejon (Eocene), but 

no proof is available. Zone D is probably equivalent in part to the 

lower Miocene sand of the Lucile well and the wells on the Eastside 

field. In the deepest wells, which obtain most of their oil from zone 

D, that zone is always more productive than zone B.

Three or more water sands are usually encountered in the wells in 

this area. In the shallower wells and even in some of the deeper 

ones the water sand is met at depths of less than 200 feet. Below 

this first layer and separated from it by about 400 feet of shale is 

usually the second sand, but in some of the wells within this distance minor beds carrying water are encountered. Below the second 

main water sand and immediately overlying the tar zone (zone A) 

is a rather persistent stratum of sulphur water reported in most 

but not all of the wells. It is more commonly found in the deeper 

holes and may be represented in the wells toward the western part 

of the area and higher up on the dip by certain members of the tarsand zone. If this is so it is interesting as showing that the hydrocarbons in the tar sand have been forced upward by the sulphur 

water which fills up this particular porous stratum, presumably 

under hydrostatic pressure.
WESTSIDE FIELD. 213

Typical well log in Zier-Porter & Scribner-M., K. & T. area.

Feet. 

Surface formation of clay and sand with a little gravel..................... 200

Water sand............................................................. 20-40

Blue shale............................................................... 350

Water sand or water gravel................................................ 40

Sulphur water sand, called the "main sulphur"............................ 30-50

Blue shale or shells, a few feet.

Alternating tar sands (zone A) and shale with 50 or more feet of shale and shell 

at the bottom......................................................... 200

Productive 17° or 18° B. oil sand (zone B) ................................. 10-60

Series of alternating oil sands and blue and brown shales, including zone D.. 300 +

PRODUCT.

The production of the individual wells in this area varies from 

40 or 50 barrels to a maximum of about 300 barrels per day. The 

gravity of the oil in those wells in the western part of the area well 

up on the dip is about 12° to 14° B., while in the deeper wells producing from the light-oil sand an average of about 17° or 18° B. 

oil is obtained. The deepest well in the area, the M., K. & T., is 

said to yield oil of about 16£° B. This oil is believed to come from 

zone D, in the Vaqueros (lower Miocene) formation.

ASSOCIATED-CALEDONIAN UNION AREA.

LOCATION.

The area described under this heading embraces the region from 

the Union lease in sec. 13, T. 20 S., R. 14 E., southward to the southern part of section 36 in the same township and range. It includes 

well No. 3A and. all other Associated wells north of this in section 36; 

also the properties of the Kern Trading and Oil (Southern Pacific 

Railroad), Caledonian, Ozark, Premier, Claremont, Wabash, Inca, 

St. Paul-Fresno, Coalinga Western, Coalinga Petroleum, Circle, 

Netherlands (formerly Valley Slope), San Juan (formerly Valley 

Slope), Coalinga Homestake (formerly Cawder), Traders (including 

what were formerly Angelus, Euclid, Marengo, and Norse), McQuigg 

& Wrenn (M. & W.) (formerly Blue Diamond), Arizona Petroleum 

(formery East Puente), St. Elmo (formerly New Home), Queen 

(formerly Coalinga Banner), S. A. Guiberson, Jr. (formerly Elgar 

Adams), American Petroleum (sections 18, 19, and 30), Nevada 

Petroleum (sections 18, 20, and 30), Valley, Coalinga, California 

(section 18), Maguire, Section One (formerly Coalinga Zenith), and 

Union oil companies.

STRUCTURE.

The wells in this area are located on the eastward-dipping monocline of the Westside field. Except for a local flexure, which is possibly the continuation of one of the lines of disturbance in the White
214 COALINGA OIL DISTRICT, CALIFORNIA.

Creek syncline, the general position of the beds is regular, and they 

have an easterly dip of 11° to 22°. The beds apparently flatten out 

in passing east from the steeper hills in the western and southwestern 

parts of the area to the valley floor.

GEOLOGY OF THE WELLS.

The wells start down in the soft beds of the Etchegoin formation 

or of the immediately underlying Jacalitos and Santa Margarita (?) 

formations. Zone B, the one shown in contour on the map (PI. XV), 

is the principal productive zone in this field, as in those farther 

north. In the northern part of the area the zone consists usually of 

a single medium to coarse grained sand varying in thickness from 20 

to 30 feet. This thickness is fairly uniform throughout the northern 

part of the area, except in that portion well down on the dip, where 

the zone apparently is thicker and is penetrated for nearly 40 feet in 

some of the wells. It is also thicker locally toward the western edge 

of the area, 50 feet of productive sand being recorded in one of the 

shallower wells. It is believed, however, that in this well a part of 

the thickness is made up of intercalated shale. ' The top of zone B, 

especially in the southern part of the area, is usually indicated by 

the presence of oyster shells and Tamiosoma fragments in the wells.

Southward the sand apparently becomes less and less productive, 

the southernmost well so far drilled which is believed to obtain 

oil in commercial quantities from this zone being Associated No. 3A. 

Here the productive sand is practically of the same thickness as theaverage farther north, but in the wells still farther south the productive sand pinches out or is practically dry. Toward the east the 

productivity of zone B ceases along a practically north-south line 

passing near the middle of sec. 30, T. 20 S., R. 15 E. This is indicated 

by the nonproductiveness of zone B in the Nevada Petroleum wells, 

although the same zone is unusually productive in the American 

Petroleum wells, half a mile to the west. The gravity of the oil 

varies from 13° to 17° B., apparently being heavier toward the outcrop of the beds and lighter down the dip. A variation in gravity 

between 14° to 15° along the strike is also noticeable, the southernmost wells producing the lighter oil.

Although zone B is the first productive zone encountered in the 

wells, there is above it a tar sand called the Big Gumbo, which is 

penetrated by nearly all the wells from the Union south to the line 

of Associated wells along the north side of section 36. This gumbo 

sand, as the name implies, carries a heavy oil or tar, which has so 

far not been utilized in any of the wells. In the region of the Caledonian wells at the western edge of the developed territory, and 

farther up on the dip, there is still a higher oil sand, but this also is 

nonproductive.
WESTSIDE FIELD. 215

Zone B consists of three well-defined oil sands throughout the 

region from the Union wells southward as far at least as the 

north edge of section 36. The uppermost of these sands varies 

from 10 to 50 feet in thickness, while the second is usually somewhat thinner. Hard shells are often associated with these lower 

sands, but in manyof the wells blue shale is apparently the only 

parting. In some instances the sands below zone B are divided 

into three or four minor layers which show little regularity in thickness between the different wells. Toward the east from the township 

line of wells the upper sand of zone B first becomes unproductive, 

then the second sand, and finally the third near the middle of section 

30 and the sections north and south of it.

The gravity of the oil in the lower beds of zone B is usually about 

the same as that in its upper beds, but in the Caledonian and Angelus 

regions an oil sand carrying 17° B. petroleum is found at the base of

zone B. It is barely possible that this may be the equivalent of 

the light-oil sand in the region of the Coalinga Pacific and other 

wells of that same area, but it is the opinion of the writers that there 

is no direct connection between beds carrying the light oil in this 

southern part and the beds carrying oil of the same gravity in the 

region north of Los Gates Creek.

In the region of the Wabash and Inca properties the oil sands 

are apparently the most regular of the Westside field, but on each 

side of this particularly regular area the variation in the sands is 

considerable from well to well, both along and across the strike 

of the beds.

A persistent stratum of sulphur-water sand is encountered in most 

of the wells between the Big Gumbo tar sand and zone B. This 

sulphur sand varies in thickness from about 10 to 20 feet, although 

in one of the Wabash wells it has apparently split up into two sands 

separated by shale, each sand member being somewhat less than 10 

feet thick. In certain wells of this area the sulphur sand contains 

traces of oil, especially in those wells along the north side of section 

36 and in some of the Union wells.

The formations above the zone of the Big Gumbo tar sand usually 

contain two or more water sands. In most of the wells the first sand 

is encountered at depths under 200 feet, but between this sand and the 

Big Gumbo the occurrence of water is irregular. In some of the 

wells water sand approximating 50 feet in thickness is encountered 

200 feet below the first water sand, whereas in wells near by the 

second water sand may be only 10 feet thick and may be separated 

from the first sand by one or two.other strata carrying Water: The 

water from all of these sands is considerably mineralized and is not 

fit for domestic uses.
216 COALINGA OIL DISTRICT, CALIFORNIA.

Typical well log, Associated-Caledonian- Union area.

Feet.

Shale.................................................................... 150

Water sand............................................................. 20-30

Shale, with some dry sand or gravel...................................... 200

Water sand............................................................. 20-50

Blue shale, with some dry sands and occasionally some water sand..........: 600

Tar zone (zone A)..:................................................... 8-50

Blue shale............................................................. 20-100

Sulphur-water sand..................................................... 20

Blue shale, with occasionally fine sand layers............................. 100-200

Zone B, consisting of various oil sands of more or less importance, the whole

being thinnest near the outcrop and thickening gradually down the dip .. 100-225

The water is generally shut off in the upper part of the blue-shale 

zone overlying zone B. Such a proceeding is doubtless flooding the 

Big Gumbo sand, but as this tar sand is not believed to be productive 

in any part of the field the flooding is doing no harm. In the Nevada 

Petroleum and Valley wells the water is shut off below the water sand 

which underlies zone B, but this proceeding, although flooding zone 

B, will simply tend to drive the oil upward and westward into the 

wells where zone B is productive.

One of the Caledonian wells was drilled to a depth of over 2,300 

feet, but from the depth of somewhat over 700 feet it passed through 

the usually unproductive brown and blue shales of the Tejon (Eocene), 

yielding warm salt-water of 110° F. near the bottom. Sulphur water 

was also encountered at about 1,600 feet in this well, and a little 

greenish oil of over 17° gravity was encountered near the 1,000-foot 

mark. The base of the productive measures in the western part of 

this area is believed to be marked by a persistent stratum of salt or 

brackish water, which is encountered in those wells which have 

been drilled into the underlying Tejon.

The product in the wells so far drilled in this area comes from zone 

B, the Jacalitos (upper Miocene) zone. The daily production of the 

individual wells varies from about 1,500 barrels in the deeper wells to 

50 or 60 barrels in the shallower. Many of the wells flow at first and 

some of the deeper ones continue to flow for two or three years, but 

most of the wells are pumped after the initial head of gas has blown 

off. Much sand accompanies the oil, the proportion being as high 

as 50 per cent at first in some of the wells. Large amounts of gas 

are produced by most of the wells. The gravity of the oil varies from 

12° B. in the shallow wells, those upon the dip, to 17° for the deeper 

holes. Three sands are recognized in the productive zone, the upper 

one yielding the lightest oil.
WESTSIDE FIELD. 217

AREA BETWEEN WALTHAM CREEK AND SAN JOAQUIN VALLEY COAL MINE.

LOCATION.

The area treated in the following paragraphs comprises the territory 

lying between the Cretaceous-Vaqueros (lower Miocene) contact, 

which extends northwestward from Alcalde, and the valley floor west 

of Coalinga, and between Waltham Creek and the region of the San 

Joaquin Valley coal mine in the NW. J sec. 26, T. 20 S., R. 14 E. A 

portion of this region, namely, that in which the wells of the Sunnyside and Westlake-Rommel oil companies are situated, will be considered separately, following the discussion of the major portion of 

the area. The oil companies in the region here discussed include the 

Mount Hamilton, Commercial Petroleum, Summit, Elaine, Lucile, 

Shreeve, Associated, Kerri Trading and Oil (formerly Southern Pacific 

Railroad), Yellowstone (formerly Coalinga Southern), Sauer Dough, 

Jefferson (formerly Section Six), California Gas and Oil (formerly T. 

C.), De Lux, Amy, Silver Tip, Red Top, Aladdin, Muriel (formerly St. 

Francis), Waratah, Marion (formerly St. Clair), Los Angeles-Coalinga 

Oil Syndicate, Section One (formerly Coalinga Zenith), Coalinga 

Great Western (formerly West Coalinga), Smith & Porter (formerly 

Summit), and some others not yet prosecuting development work.

GEOLOGY.

The formations involved in the geology of this area comprise 

the Cretaceous (Knoxville-Chico) sandstone and shale, the Eocene 

(Tejon) sandstone and shale, a series of sandstones overlain by soft 

shale, which are believed to be largely of Vaqueros (lower Miocene) 

age, the sandstone, conglomerate, and shale of the Jacalitos (early 

upper Miocene) formation, and sand and clay shale of the Etchegoin 

(late upper Miocene).

The Knoxville-Chico (Cretaceous) consists of dark thin-bedded 

shale with some sandstone, the latter in places carrying the characteristic brown concretions. It outcrops west of the area, under discussion and extends in a northwesterly direction into the hills south 

of Los Gatos Creek. In the main the Cretaceous beds are steeply 

tilted, forming a monocline with an approximate dip of 60° SE. 

They carry no oil, but are believed to yield the water in the Henshaw 

and West Coalinga wells.

The Tej on (Eocene) consists largely of medium-grained sandstone 

with some intercalated shales at the base and a considerable thickness of shale at the top. The Tej on occupies a small area in the 

SW. J sec. 26, T. 20 S., R. 14 E., immediately south of the San Joaquin Valley coal mine. Except this small outcrop the Tej on in this 

area is entirely covered up by the later beds, which overlap it from 

the east and south. The basal Tej on overlies the Cretaceous, appar-
218 COALINGA OIL DISTRICT, CALIFORNIA.

ently conformably, and clips northeastward at an angle of about 30° 

and is itself in turn overlain unconformably by the Miocene beds.

Unconformably overlying the Knoxville-Chico (Cretaceous) and 

the Tejon (Eocene) just described, is a series of beds consisting of 

about 250 feet of sandstones and over 100 feet of soft dark-blue 

shale. These beds are known to be Vaqueros at the base, but the 

age of the uppermost member, the shale, is unknown. However,- 

it may possibly be the equivalent of the Big Blue in the north end 

of the Coalinga field, although in the area under discussion it has 

been mapped with the Vaqueros, and in the Eastside field it is included 

in the Santa Margarita (?) formation. The basal sandstone of the 

Vaqueros formation may be traced from a short distance south of 

the San Joaquin Valley coal mine southward across the northwest 

corner of sec. 35, T. 20 S., R. 14 E., along the western edge of the 

same section, into the middle of the NW. J sec. 2, T. 21 S., R. 14 E., 

thence southeasterly to the bottom of the canyon near the middle 

of the south line of the SE. £ sec. 2. Thence it passes westward 

below and north of the summit of the big ridge which extends several 

miles northwestward from Alcalde. Near the San Joaquin Valley coal 

mine the Vaqueros overlies the Tejon (Eocene), but near the northwest corner of section 35 it crosses the contact between the Knoxville-Chico (Cretaceous) and the Tejon, and thence southwestward 

it overlies the Knoxville-Chico. The contact between the Knoxville-Chico and the Tejon is believed to extend southeastward underneath the Vaqueros diagonally through sec. 35, T. 20 S., R. 14 E., 

and diagonally through sec. 1,T.21S.,R. 14E. Its course from the 

latter region is not definitely known, but can be surmised as stated 

on pages 238-239. The tracing of this contact beneath the Vaqueros 

is important, because the oil is derived from the Eocene shale, and 

it is believed that wherever the Vaqueros or other formations overlie 

the Tejon they will be found more or less petroliferous, while in the 

areas where the same formations overlie the Knoxville-Chico they 

will be found barren or to contain only such petroleum as has migrated 

along the strata from areas underlain by the Tejon. It is worthy 

of note in this connection that along practically the whole extent of 

the outcrop of the base of the Vaqueros from the San Joaquin Valley 

coal mine southward to the southern part of sec. 2, T. 21 S., R. 14 E., 

the basal beds are more or less petroliferous. The indications are 

so strong in certain places, notably in the SE. J sec. 2, that tunnels 

have been run into the base of the Vaqueros sands with the expectation of obtaining petroleum in commercial quantities.

Westward from.1 the southeastern part of section 2 the basal sands 

of the Vaqueros become less and less petroliferous, until on the flanks 

of the ridge spoken of as extending northwestward from Alcalde the 

beds show no, indications of petroleum.
WESTSIDE FIELD. 219

The description of the geologic section exposed on the surface 

along a line extending from the middle of the south line of sec. 2, T. 

21 S., R. 14 E., in Anticline Canyon, to the top of Flag Hill, in the 

SE. J sec. 1, T. 21 S., R. 14 E. (shown as the triangulation station 

on the topographic map), and thence in a direct line to the Lucile 

well, epitomizes the formations of the area under discussion. This 

section is based upon a detailed surface traverse and in a general 

way upon the well logs of sections 6 and 36 to the northeast.

Explanation of hypothetical section (fig. 8) along line F-F/ on contour map (PL XV), 

from Anticline Canyon to California Oil and Gas Company's well No. 1, beginning 

with lower strata.

[Dip approximately 20° NE.]

Vaqueros (lower Miocene), beds a, ft, c, and d.

a. Much discolored and rusty-yellowish sand and soft sandstone, highly charged

with petroleum in the immediate vicinity of Anticline Canyon, and about 

150 feet thick. Not yet pierced by any of the wells in the section 6 area, 

but believed to be a rich oil-bearing sand throughout its thickness. Represents the basal part of zone D of the developed territory.

6. Largely gypsiferous sand, with a hard fossiliferous layer at the base. The 

fossils, which are abundant in Anticline Canyon a short distance below the 

south line of section 2, are believed to be from the same bed as the fossil 

"clam" shells thrown out in the sand from the bottom of Lucile well No. 1. 

About 150 feet thick; probably represents parts of oil zones C and D in the 

Eastside field.

c. Soft sand with pebbly layers and occasional hard, coarse, rusty sandstone 

strata which would be called "sandstone shell" if encountered in the wells. 

About 200 feet thick, and also a part of zones C and D. Beds b and c apparently thin out slightly toward the valley, as the thickness disclosed by the 

well logs is somewhat less than that obtained by calculation from the surface 

outcrops.

d. Largely clay, about 250 feet thick; may be the equivalent of the Big Blue in

the Eastside field. 

Jacalitos (early upper Miocene), beds e,f, g, h, i, j, and k.

e. Largely pebbly gravel overlain by thin-bedded sand and soft sandstone. Bed 

of fossils, largely Zirphxa, at top; believed to be the ones reported in both 

the Shreeve and Lucile logs. These are an important tie line, not only in 

this particular area, but also throughout the Coalinga district. Bed believed 

to be the same as that which rests upon or near the shales of the Tejon west 

of that part of the Westside field lying north of the San Joaquin Valley coal 

mine, and believed to be of upper Miocene age. It is zone B in the wells 

of the south and central parts of the Westside field, and is between 100 and 

200 feet in thickness.

/. Above the fossil bed are some coarse gray sand layers. Well in northeast 

corner of the SW. J sec. 12, T. 21 S., R. 14 E., begins in this zone of sand.

g. Consists of clay shale and apparently thickens somewhat toward the valley, 

especially between the Shreeve and Lucile wells.

h. A persistent layer of soft, pebbly sandstone, recognized in both the Shreeve 

and Lucile well logs.

i. Ten-foot layer of clay.

j. Another pebbly sandstone layer, apparently not so persistent as bed h.

k. An important and widespread blue clay.
220 COALINOA OIL DISTRICT, CALIFORNIA.

Etchegoin (uppermost Miocene), beds I, m, n, o, p, and q.

I. This sand zone consists of brown sand at the base, 10 feet of hard sandstone 

above it, then a layer of sand, another layer of sandstone, and finally a soft 

sandstone at the top.

m. Soft blue shale, 15 to 200 feet thick.

n. Coarse brown to greenish pebbly sand at the base, overlain by coarse brown 

sand containing numerous large fossil sand dollars, Echinarachniiis yibbsii 

Esmond. About 125 feet thick.

o. Sand and soft sandstone, pebbly at the bottom, with numerous fossils. Known 

as a fossil bed in the wells in some parts of the field; contains such species 

as Pecten oweni Arnold, Glycymeris, etc. It is the Gtycymeris zone, not far 

above the base of the Etchegoin formation.

p. Bluish clay about 100 feet thick.

q. From bed q down to the detritus-covered valley floor in the vicinity of the 

Lucile well No. 1 the beds exposed are largely coarse sands with occasional 

pebbly layers. Toward the edge of the hills some of the beds contain cobbles 

of considerable size and fossils indicating the same horizon as the Pecten 

coalingaensis zone, near the top of the Etchegoin in the Kreyenhagen Hills. 

Usually spoken of by the drillers as "surface formation," as they appear to 

be largely incoherent and of heterogeneous character. Total thickness of 

the Etchegoin exposed is about 750 feet. Uppermost beds in the wells 

possibly represent a part of the Tulare formation.

STRUCTURE.

The main structural feature governing the area under discussion 

is of course the great southeastward - dipping monocline which 

extends from the top of Curry Mountain and Juniper Ridge to the 

middle of Pleasant Valley. There are, however, one or two local 

lines of disturbance within the area which are worthy of mention. 

The most important begins in the Knoxville-Chico (Cretaceous) 

somewhere northwest of sec. 2, T. 21 S., R. 14 E., and passes southeastward, apparently almost coincident with the bed of Anticline 

Canyon. From the south line of section 2 to the middle of the E. $

SW. £ sec. 12, this line of disturbance has the character of a southeastward-plungirig anticline. The dips to the east are apparently 

about 20°, while those toward the south vary from 8° or 10° in the 

region immediately south of section 2 to 30° or 40° in the southern 

part of the SW. J sec. 12. At a point a short distance west of the 

east line of the SW. J sec. 12 the line of disturbance bends abruptly 

and passes almost due east for nearly three-fourths of a mile. Along 

this east-west portion the disturbance takes the form of a fault at 

the surface, although the beds in a general way dip away on both 

sides of the fault line. The line of fracture may be traced from the 

dome of the anticline in the east wall of Anticline Canyon, in the 

eastern part of the SW. i sec. 12, to a point less than one-fourth mile, 

northeast of the Commercial Petroleum Company's well No. 1, in 

the SE. J sec. 12. The beds on the south side of the fault are inclined in a southerly direction, with dips varying from 60° or 70°
WESTSIDE FIELD. 221

near the fracture to 35° or 40° some distance south of it. North of 

the fracture the beds dip about 20° NE. and abut sharply against 

the steep southward-dipping beds. From the east line of the SE. £ 

sec. 12 the line of fracture apparently bends abruptly toward the 

southeast and either dies out beneath the superficial deposits of 

Alcalde Canyon or is connected in some way with the Jacalitos 

anticline.

A minor disturbance, probably intimately connected with the 

one just described, is developed in an east-west ridge in the NE. J 

sec. 7, T. 21 S., R. 15 E. An examination of the surface geology 

of this region, beginning at the railroad cut in the NW. | sec. 8, T. 

21 S.,R. 15 E., discloses, first, coarse sandstone beds dipping 10° 

to 50° N. 35° E.; thence westward along the crest of the ridge 

dips of 16° N. 25° W. are first encountered, then dips of 20° a little 

farther west, and finally, where the strike of the beds swings around

northwest, the dip is as high as 40°. Northwestward from this 

maximum dip the beds drop to 30° NE. and finally to the prevailing 

dip of 18° to 20° along the western side of section 6.

A third line of disturbance is visible in the small bluff on the 

northwest side of Alcalde Canyon, immediately north of Alcalde 

station. This is a sharp anticlinal fold in gray and brown shale 

with a dip of 20° S. 53° W. on the one side and 70° N. 55° E. on the 

other. Mount Hamilton well No. 1 is drilled practically on the axis 

of this anticline, less than one-fourth mile from the bluff mentioned. 

An examination of the territory northwest of the Mount Hamilton 

well, embracing the territory along the contact between the Knoxville-Chico and the Tejon, discloses dips that apparently indicate 

a northwestward continuation of the anticline as far as the SE. $ 

sec. 10, T. 21 S., R: 14 E. The beds in this region lie so nearly horizontal and have been so affected by landslides that it is impossible 

to determine definitely the course of the line of disturbance. This 

structural feature, however, has no apparent influence whatever 

upon the oil-bearing beds, but is described simply to indicate where 

the forces produced folding in the beds.

Still a fourth line of disturbance enters the area under discussion in 

the southwestern part of sec. 7,T. 21 S., R. 15 E. This is the Jacalitos 

syncline, which is prominently developed farther south and will be 

described in the discussion of the area south of Waltham Creek. In 

the southwest corner of section 7 this syncline produces dips of 40° 

S. 20° W.; a short distance south the same bed dips 30° nearly due 

east, a little farther south 25° in the same direction, and still farther 

south 20°. This syncline is apparently associated with the Anticline 

Canyon flexure, but the relations between the two are obscured 

by the detrital material of Waltham Creek at the critical point 

along the south line of section 7,
222 COALINGA OIL DISTRICT, CALIFORNIA.

In connection with the folding and faulting which has taken place 

in section 12, it might be well to discuss the geology in the vicinity 

of the Commercial Petroleum well No. 1, in the southeast corner of 

the SE. 1 sec. 12, T. 21 S., R. 14 E. A section along the surface of 

the ridge northward from this well shows the following strata, all 

dipping about 60° approximately due south.

Section in Miocene north from Commercial Petroleum Company's well No. 1, sec. 12,

T. 21 S.. R. 14 E.

Feet. 

Soft sand.................................................................. 30

Pebbly sand.............................................................. 40

Soft sand................................................................ 180

Coarse sand with hard dark layers ("shells")............................... 240

Fine pebbly sand (the dip here is 60° due south).......................... 255

Alternating coarse sandstone and pebbly sandstone beds with a particularly

hard brown sand layer at the base...................................... 320

Soft blue shale and sandy shale........................................... 620

Coarse pebbly sand, the last half hard and containing silicified wood fragments

(dip is 50° S.).....'..................................................... 710

Gray sand with one or two hard streaks.................................... 7GO

Soft blue gypsiferous shale. . .............................................. 790

Medium to coarse gray sandstone ............. .^........................... 820

At 820 feet is the fault line extending S. 80° E. The downthrow 

is on the north and is probably at least 200 feet. The beds along the 

trace of the fault are of a purplish and pink tint, this discoloration 

probably being due to petroleum which has seeped up along the fault. 

A comparison of the surface section and the log of the Commercial 

Petroleum well indicates the reason for the discrepancy between this 

well log and those of the wells in the section 6 area. In the Commercial Petroleum well the beds penetrated dip 60° or so, while the beds 

in the section 6 area dip less than 20°. The water in the Commercial

Petroleum well is probably local, and is to be associated with the 

fault line which the well apparently cuts near the junction of the well 

with the oil sand. It is the belief of the writers that it would be 

impossible to put down wells in this faulted area and obtain the same 

or even approximate results in any two. The region about the corners of sees. 12 and 13, T. 21 S., R. 14 E., and sees. 7 and 18, T. 21 S., 

R. 15 E., is the center of a number of complex disturbances, which 

are believed so to complicate the underground geology locally as to 

make the exploitation of the oil sands difficult if not impossible.

GEOLOGY OF THE WELLS.

The wells in this area a lie for the most part on the south-southeastward continuation of the great eastward-dipping monocline

a Wells drilled in this district since the publication of the writers' preliminary report (Bull. U. S. Geol. 

Survey Nc. 357, Nov. 23,1908) have shown that certain of the conclusions drawn regarding sec. 6, T. 21 S., 

R. 15 E., were erroneous. These, together with Plate III of that report, have therefore been revised, to 

agree with the latest data obtainable October 15,1909.
WESTSIDE FIELD. 223

which controls the oil-bearing formation of the Westside field. Somewhere south of sec. 6, T. 21 S., R. 15 E., probably in section 7 or 18, 

the strike changes to an easterly direction as the result of movements 

along the Jacalitos anticline and associated structural lines. It will 

be noticed by an examination of the contour map (PI. XV) that the 

formations have a practically uniform dip of about 18° or 20° down 

to the edge of the more pronounced hills. At the edge of the hills the 

dip flattens out considerably. It should be observed in this connection 

that the topography in a general way reflects this change in dip. This 

is an important item to remember, as in other parts of the field where 

there are no wells and in which surface outcrops are lacking it may be 

possible to judge in a general way of the position of the underground 

formations by a critical examination of the topography of the region 

under observation. As a result of the bowing of the strata the dips 

are apparently steepest in section 36, but flatten out and become

more regular north of this area. In the southern part of section 6 and 

also the northern part of section 7 the dips are very steep at the surface outcrop. The locus of the steep dip apparently extends from the 

surface underground in a northerly direction and has its maximum 

effect on the oil sands in the NW. \ sec. 6 and in the SE. \ sec. 36. 

Details of the change in dips and strike are indicated by contours on 

the map (PI. XV), and will not be discussed further here.

All of the wells within this area start down in the soft surface.sands 

and clays, which, below the uppermost superficial stratum, are 

believed to belong to the Etchegoin or possibly to the Tulare formation. Before reaching the uppermost oil zone (zone B) the 

wells pass through four or five well-defined zones of sandstone with 

as many interbedded layers of soft blue shale. Many of the sands 

carry pebbles up to the size of a marble, and some of the blue shales 

are also pebbly. Water sands are encountered at various depths, 

some of them producing large quantities of more or less mineralized 

water. The Lucile well No. 1 and the West Coalinga well No. 1 

produce a great deal of water, but from entirely different formations, 

the first from the Jacalitos (upper Miocene), the latter probably from 

the Knoxville-Chico (Cretaceous). Water is usually encountered 

between zones B and D, one sand in the base of or just below zone B 

carrying sulphur in some of the wells, and another persistent layer 

occurring just above zone D. Water is also encountered between 

the uppermost or fine-grained light-oil sand and the next sand (heavyoil sand) below in zone D. This last-mentioned water stratum is 

believed to yield the water produced with the oil in the Lucile No. 1, 

Aladdin, and near-by wells which have penetrated the heavy-oil beds. 

Where the heavy-oil strata of zone D are lacking, as in certain of the 

wells in the western part of section 6, water marks the base of the 

productive zone, which here consists only of the uppermost strata of
224 COALINGA OIL DISTRICT, CALIFORNIA.

zone D. Some very hard sandstone shell layers are encountered in 

the wells, and in one or two places these appear to be rather persistent laterally. The hard layer reported as the "big shell" in some 

of the wells is apparently not the same stratum that is designated 

by that name in certain others.

The first oil zone (zone B) varies in thickness from about 60 to 150 

feet. In some of the wells it is reported as nearly solid sand, while 

in others it is a zone of alternating sandstone and shale. Oil or gas 

or both are reported from it in a few of the deeper wells, but in most 

the zone is apparently dry. It is believed that indications of petroleum must have been found in this well and overlooked by the driller, 

or else they were not considered of enough importance to record in 

the log. So far as known no well in this area produces from this 

zone. The individual sands of zone B vary from fine-grained thinbedded layers intercalated with sandy shale to coarse conglomeratic 

sand carrying small cobbles. As previously mentioned, this zone 

may be studied in the east wall of the canyon running up to the Henshaw water well (SW. f sec. 35, T. 20 S., R. 14 E.), about half a mile 

southeast of this well.

Oil zone B is underlain by a persistent stratum of mineralized 

water, either salt or sulphur or both, in nearly all the wells. In some 

this flow of water was encountered at the base of a hard sandstone shell 

underlying the oil strata, but in others it is reported in the lowest oil 

sand of the zone. Oil zone B is separated from the lower or zone D 

by between 150 and 200 feet of shale and .shell. Some water sands 

and tar sands are reported in the space between zones B and D in 

some of the wells, but these do not appear to be very persistent. 

Most of the wells have penetrated zone D, but touch only its uppermost sands. The reason for this is generally that the gas pressure 

is great enough either to make the well flow or to fill it up with 

sand. The uppermost beds of zone D are fine grained and carry 

oil of-fairly light gravity. Oil of 32° B. has been reported in one of 

the wells, and the gravity of all the upper bed's seems to range 

from this down to 22° B.

Below the zone of light-oil sands is a coarser sand carrying fossil 

shells and believed to be the same as the bed at the base of bed 6 in 

the section given on page 191. The oil from this lower zone is much 

heavier than that from the upper and averages somewhere near 16° 

or 17° B. in gravity; the lower sand also is very much more productive than the finer sands and is therefore tapped wherever possible. It is the belief of the writers that this lower oil sand will 

furnish long-lived wells, for the holes which simply tap its uppermost layers are very productive, and the 150 or 200 feet of sands 

which are believed to underlie the upper beds in the deeper wells 

are doubtless heavily impregnated with oil.
WESTSIDE FIELD. 225

The following is a log characteristic of the wells in this area:

Log of Aladdin Oil Company's well No. 1, sec. 6, T. 21 S., R. 15 E.

Feet 

Brown sandy formation..................................................... 320

Dark water sand........................................................... 395

Brown shale. ......................... ..................:................. 500

Sand and gravel............................................................ 515

Blue shale................................................................. 560

Brown shale................................................................ 605

Blue shale................................................................. 685

Dark sand................................................................. 705

Blue shale................................................................. 728

Water sand............................................................... 750

Blue shale................................................................. 810

Shale and shells............................................................ 900

Blue shale................................................................. 1,000

Shale and shells. ................................... ...- - - - 1,055

Sand..................:.................................................. 1,070

Shale and shells.............................................................. l, 150

Dark sand................................................................. 1,190

Shale and shells............................................................ 1,240

Sand..................................................................... 1,258

Shells and shale............................................................ 1,330

Hard sandstone (underreamed)............................................. 1,350

Sticky blue............................................................... 1, 370

Sandy shale.............................................................. 1,410

Hard blue clay............................................................ 1, 425

Blue shell and shales...................................................... 1,460

Sandy shale.............................................................. 1,475

Hard sandstone........................................................... 1, 490

Sticky blue!..........................................................."... 1,515

Sandy shale.............................................................. 1,520

Shell....................................................................... 1,522

Sticky blue............................................................... 1, 590

Sandy shale.............................................................. 1, 660

Gray shale. ................................................................ ls 700

Blue shale................................................................. 1, 750

Sand and gravel........................................................... 1, 780

Hard conglomerate........................................................ 1, 815

Sand..................................................................... 1, 840

Blue shale................................................................. 1,875

Blue and sandy shale. ...................................................... 2,012

Sand and broken shale.................................................... 2,060

Sticky blue shale......................................................... 2,115

Pebbles and sand.......................................................... 2,118

Shale (underreamed)....................................................... 2,168

Shell (underreamed)...................................................... 2,170

Shale (underreamed)....................................................... 2,205

Sandy shale.............................................................. 2, 218

Sand and shells (underreamed).............................................. 2, 290

.Sticky blue clay.......................................................... 2,360

88170 Bull. 398 10 15
226 COALINGA OIL DISTRICT, CALIFORNIA.

 Feet..

Blue shale and shells.................................;.................... 2,440

Shale.....................................................................'2,485

Dark.sand................................................................. 2, 505

Oil sand, white.............................................................. 2, 530

Hard oil sand.............................................................. 2, 533

Coarse oil sand............'................................................. 2,543

Hard shell................................................................. 2,558

Oil sand and oyster shell................................................... 2, 585

PRODUCT.

The daily yield of the individual productive wells in the area under 

discussion varies from about 100 barrels for those up on the dip to 

about 800 barrels in the deeper holes. An initial production of over 

1,500 barrels per day is said to have come from one of the wells. Oil 

of 26° B. gravity is yielded by sands at the top of the lower zone 

(zone D), and as high as 175 barrels of oil per day is said to have been 

produced by one well from these sands alone. Below the light-oil 

sands are coarser and more productive layers which yield the bulk of 

the oil for this territory. The gravity of the petroleum from this last 

horizon is between 16° and 17 ° B. The oil in light-oil sands is brown; 

that in the zone of heavier oil black.

The most phenomenal well in this area is the Silver Tip, which 

gushed gas, sand, and oil when zone D was first penetrated, then 

sanded up, and finally, when it was cleaned out, gushed a second 

time at the rate of 20,000 barrels a day for a few hours. For the 

first few days of its productiveness it flowed and sanded intermittently; after two months it is now (November 1, 1909) yielding 2,500 

barrels a day.

AREA EMBRACING SEC. 2, T. 21 S., R. 14 E.

LOCATION.

Under this heading will be discussed the underground geology in 

the E. £ sec. 2, T. 21 S., R. 14 E., and the southern part of sec. 32, 

T. 20 S., R. 14 E., which has been tested by the wells of the Sunnyside Oil Company (Henshaw water well) and Westlake-Rommel 

Oil Company. .

GEOLOGY OF THE WELLS.

The wells in this area penetrate the northeastward-clipping beds 

of the Vaqueros (lower Miocene), which overlie the steeply tilted 

Knoxville-Chico (Cretaceous) strata expqsed at the surface toward the 

west. The oil in this area is believed to have percolated along the 

basal or zone D sands from the territory toward the east, where these 

sands overlie the shales of the Tejon (Eocene) formation. Only four 

wells have so far been put 49w:B ifi ^n^s area- Three of these were
KREYENHAGEK FIELD, 227

sunk several years ago by the Westlake-Rommel Company and the 

other is the Henshaw water well, which was put down by Captain 

McClurg for the Sunnyside Oil Company in 1897. The logs of these 

wells indicate that the petroliferous zone is from 100 to 120 feet 

thick and consists of medium-grained sands interbedded, especially 

toward the middle of the zone, with fine clays and harder sand layers. 

The s'and carries a little heavy oil and in the Westlake-Rommel wells 

is said to have yielded no gas. This lack of gas would be expected in 

an area so close to the outcrop of the oil sands, where the gas would 

have an opportunity to escape from them. Water is found associated 

with the oil in the uppermost layer of this zone in one of the wells and 

. is found abundantly in the sands just beneath the oil zone. In addition to the four wells mentioned, tunnels have been run in on the 

outcrop of the oil sands in the E. £ sec. 2, but not enough oil was 

obtained from them to pay for their operation.

It is believed that the Henshaw well obtains its water supply from 

a sand in the Knoxville-Chico (Cretaceous), as the depth at which the 

sand is penetrated is considerably lower than the base of the Vaqueros 

formation. As the Knoxville-Chico beds in this region are highly 

tilted, there is probably but a narrow band along which wells put 

down with the expectation of tapping the Henshaw water sand will 

be able to reach it. The strike of the Knoxville-Chico is here about 

east-northeast, so that it is believed that this band strikes in a direction north-northwest or south-southeast of the Henshaw well.

PKOD'UCT.

The discussion of the product accompanying the preceding area 

(p. 226) applies to the whole region between Waltham Creek and the 

San Joaquin Valley coal mine.

KllEYENHAGEN FIELD.

LOCATION.

The region south of Coalinga as far as Dudley, Kings County, including the Kettleman and Kreyenhagen hills and Reef Ridge, has been 

known for many years as the Kreyenhagen oil district. For the sake 

of brevity of discussion in the present report this territory has been 

included as a part of the Coalinga district and has been divided into 

two fields, the Kreyenhagen field and the Kettleman Hills field.

The area discussed as the Kreyenhagen field lies on the southeastern 

flanks of Reef Ridge and extends from the general region of Jacalitos 

Creek to Dagany Gap, 3£ miles southeast of Dudley. The area in 

which oil development has been carried on is a narrow band between 

Canoas Creek and the region of Big Tar Canyon.
CQALttfGA OIL DISTRICT, CALtfQRHlA,

MAl3 .

The contour map of the Kreyenhagen field (PL XXII) is intended 

primarily to give a generalized representation of the monocline on 

the northeastern flanks of Reef Ridge and the rate at which the 

formations pitch below the surface. The underground contour lines 

indicate the approximate depth above (marked -f) and below 

(marked ) sea level of the upper portion of the Vaqueros sandstone or the lower portion of the hard white shales mapped as Santa 

Margarita(?) formation; in other words, the distance below sea level 

of the horizon that is supposed to be the highest one at which oil 

may be found.

The structural lines on this map were drawn solely on the basis 

of the apparent dip of the beds on the surface and without the aid 

of any underground data such as are afforded by the oil wells in the 

Coalinga field. The contours are entirely hypothetical.

GENERAL GEOLOGY AND OCCURRENCE OF OIL.

Reef Ridge and the region immediately adjacent to it, both southwest and northeast, are a part of the great monocline of rocks which 

forms the east flank of the main Diablo Range. The formations 

involved in the geology are the conglomerates, sandstones, and 

shales of the Knoxville-Chico (Cretaceous); the sandstones and 

shales of the Tejon (Eocene); the sandstone and shale of the Vaqueros (lower Miocene) ; the shale of the Santa Margarita (?) (upper middle 

Miocene); and the sandstone, shale, and gravel of the Jacalitos formation (upper Miocene) . The oil, as in the Coalinga field proper, is 

believed to have originated in the shales of the Tej on formation, but 

has migrated to the sandstones of. the Tejon that underlie the shales

of that formation, to sands interbedded with those shales, and to 

the overlying Vaqueros sandstone. Numerous tar springs that rise 

from the Tejon and Vaqueros within the area under discussion show 

that those formations contain oil. Among the principal springs of 

this kind may be mentioned those in Canoas Creek, which come from 

the upper part of the Vaqueros; those on or near the Clark ranch 

farther south, in the vicinity of Garza Creek, also in the Vaqueros ; 

the famous tar spring in Big Tar Canyon, which comes from the 

upper part of the Tejon; and the springs in Little Tar Canyon and 

north of it, which come from the upper part of the shales of the 

Tejon. Numerous other seepages and springs are found along the 

outcrop of the Tejon and Vaqueros, but within the area mapped 

none, to the knowledge of the writers, are found farther north than 

Canoas Creek or farther south than the head of Little Tar Canyon.

Indications of petroleum are found in the basal shale layers in the 

Tent Hills anticline 2 miles southeast of Dudley, but no true seep-
U. S. GEOLOGICAL SURVEY

17

BULLETIN 398 PLATE XXII

CONTOUR MAP OF THE KREYENHAGEN FIELD.

Contour lines show position of top of Vaqueros oil-bearing formation relative to sea level. (For surface contours see Pi. 1.)
KREYENHAGEN FIELD. 229

ages are known between the one in Little Tar Canyon and Sulphur 

Spring, in the Devils Den district. The Castle Mountain fault, 

which cuts off. the Tejon and Vaqueros formations near the head of 

Little Tar Canyon, is believed also to eliminate these same formations below the Santa Margarita (?) formation southward for a considerable distance below the head of Little Tar Canyon. Owing to 

the steep dip in the formations along Reef Ridge the petroliferous 

zone is necessarily very narrow. The extent of the zone in which it 

seems possible that productive wells may be put down is shown on 

the map (PI. I). Water accompanies the oil in all the seepages 

along this belt and has caused the failure of many test holes, which 

will be described later.

GROUPS OF WELLS DISCUSSED.

The wells in the Kreyenhagen field may be divided into two groups, 

those which have been sunk in the Tejon (Eocene) formation and 

those which start in strata above or younger than the Tejon. The 

wells in the first group, enumerated from north to south, include 

those of the Kreyenhagen Oil Company, Kings County Oil Company, 

Consolidated Oil and Development Company, Baby King Oil Company, and Avenal Land and Oil Company. The wells in the second 

group, enumerated in the same direction, include those of the Black 

Mountain Oil Company, Kings County Oil Company, St. Lawrence 

Oil Company, and El Cerrito Oil Company (formerly known as the 

Anderson well).

GEOLOGY OF WELLS IN THE TEJON FORMATION.

The two wells of the Kreyenhagen Oil Company are located on 

Canoas Creek, in the SE. I sec. 32, T. 22 S., R. 16 E. Both wells 

start in the shale in the upper part of the Tejon, the southernmost, 

well No. 1, beginning lowest in the formation. This well (No. 1) 

penetrated 650 feet of dark-colored shale, finding water at 125 and 

at 400 feet, and ended in 10 feet of oil sand.

An examination of the geology immediately south of this well 

indicates that the oil sand is very much thicker than is indicated by 

this log; just how far below the shale the sand is impregnated it was 

not possible to determine accurately, but on the surface the sand 

showed signs of petroleum for a thickness of over 100 feet. Well No. 

1 is said to have yielded about 15 barrels per day at the start, soon 

falling to 5 or 6 barrels. The product is said to be a light-green 

oil, with gravity between 37° and 38° B. No water accompanied it. 

Well No. 2 of the same company is located north of well No. 1 and 

higher in the formation. It is said to have struck traces of oil at 

1,000 and 1,100 feet and to have attained a depth of about 1,200 

feet, at which point water was encountered. This well (No. 2) 

never produced commercial quantities of oil.
230 COALINGA OIL DISTRICT, CALIFORNIA.

The Kings County Oil Company sunk a well in the SW. £ SW. i 

sec. 3, T. 23 S., R. 16 E. This location implies that the well started 

at about the middle of the band of the Tejon formation that covers 

that vicinity. The well is said to have passed through black shale, 

blue sandstone, and brown sandstone containing oil, but was abandoned on account of water.

The Consolidated Oil and Development Company sunk two wells 

in the Tejon (Eocene) formation iii the NE. £ sec. 10, T. 23 S., R. 

16 E. One of the wells reached a depth of 1,100 feet and is said to 

have obtained a good showing of 20° B. amber-colored oil at a depth 

of 1,050 feet. The difference in. gravity between this oil and that 

obtained from the same formation in the Kreyenhagen well is not 

easily explained.

The well of the Baby King Oil Company is located immediately 

behind Reef Ridge, in the NE. i sec. 11, T. 23 S., R. 16 E., in the 

canyon of the first stream west of Big Tar Canyon. It starts down 

in strata lying near the contact between the Tejon (Eocene) and 

Vaqueros (lower Miocene) formations. It is said to have struck oil 

of 30° B. gravity at 400 feet and oil of 18° B. gravity at 1,110 feet; 

a short distance below this last point flowing water was encountered. 

At the time of the writers' visit in September, 1907, the well was 

flowing about one-half miner's inch of water, accompanied by occasional blebs of black heavy oil and some gas.

The Avenal Land and Oil Company has two wells in the E. % E. § 

sec. 18, T. 23 S., R. 17 E., not far from the famous tar spring inBig Tar Canyon. Well No. 1, the western of the two, starts down 

in the soft oil-stained sand beds of the Tejon (Eocene) or possibly 

Vaqueros (lower Miocene) immediately underlying the lowest hard 

sandstone bed of the Vaqueros. The log of this well is as follows:

Log of well No. 1, Avenal Land and Oil Company, E. } E. \ sec. 18, T. 23 S., R. 17 E.

Feet. 

Adobe...................................................:.......,........... 20

Oil sand with water. ......................................................... 70

Blue water sand............................................................. 140

Clay......................................................................... 235

Shale............:.......................................................... 521

Oil sand.. .................................................. ..^................ 555

Shale. ...........; ....:.................................................... 590

Sand showing traces of oil.................................................... 635

Shale....................................................................... 802

Blue clay.................................................................... 900

Sand with traces of oil (not finished)...........:............................. 984

This well is said to have yielded less than 2 barrels 'per day of 

dark-colored 28° B. oil. Well No. 2 starts well down in the Tejon 

and is said to have gone through soft sand to 1,045 feet, where a 

productive sand was encountered. It yielded some oil when bailed.
KREYENHAGEN FIELD. 231

GEOLOGY OF WELLS IN FORMATIONS ABOVE THE TEJON.

The Black Mountain Oil Company sank two wells in the SW. £ 

NW. i sec. 33, T. 22 S., R. 16 E. These wells both start down in the 

dark shale of the Santa Margarita (?) formation and obtain their oil 

from the top of the Vaqueros sandstone. The log of well No. 1 of 

this company is as follows:

Log of well No. 1,Black Mountain Oil Company, SW. £ NW. \ sec. S3, T. 22 S., R. 16 E.

Feet.

Dark-colored shale............................................................. 80

White sand................................................................... 85

Dark-colored shale............................................................ 400

Light-colored shale........................................................... 550

Shale and sand with oil........................................................ 570

Light-colored shale............................................................ 640

Oil sand............................-.----.------ ------------------------ <?60

Shale. ........................ ^.....................................:....... 700

Oil sand........................J............................................ 720

This well is said to have produced 5 or 6 barrels of black, 18° B. 

oil.. The second well is located 600 feet north of No. 1, but no data 

concerning it are available.

The Kings County Oil Company sank a well in the SW. £ NE. J 

sec. 3, T. 23 S., R. 16 E., which is believed to start toward the bottom 

of the Santa Margarita (?) formation (upper middle Miocene) and to 

obtain its oil from the Vaqueros (lower Miocene). The log of this 

well is as follows:

Log of well of Kings County Oil Company inSW. \ NE. \ sec. ,?, T. 23 S., R. 16 E.

	Feet. 

Clay and soil.............................................................. 12

White shale................................................................ 29

Black shale................................................................ 65

Black sand................................................................ 67

Black shale................................................................ 90

Hard gravel................................................................ 120

Black shale (heavy oil at 240 feet)..............'.............................. 275

Gravel........./........................................................... 285

Black shale................................................................ 410

Blue sand rock............................................................. 450

Water sand................................................................. 490

Blue sand rock............................J............................... 540

Sand..................................................................... 556

Clayey sandstone....................................................*...... 600

Black shale................................................................ 660

Clayey sandstones......................................................... 696

Hard shale............................................................:... 720

Hard rock, sandstone predominating.............;........... % ............... 950

Another well was started by the same company but never finished.

The St. Lawrence Oil Company is said to have sunk a well in the

SE. J NE. i sec. 12, T. 23 S., R. 16 E., which encountered oil near
232 COALINGA OIL DISTRICT, CALIFORNIA.

the bottom. This well doubtless began in the Santa Margarita (?) 

and penetrated the oil sands at the top of the Vaqueros (lower Miocene).

A. M. Anderson and associates (El Cerrito Oil Company) were 

drilling in the summer of 1908 on a well in the NWV J sec. 14, T. 23 S., 

R. 17 E. The well starts down near the contact between the Etchegoin (upper Miocene) and Tulare (Pliocene-Pleistocene) formations, 

and is said to have been located on the evidence of a supposed oilsand outcrop a few hundred feet south of the well site.

KETTLEMAN HILLS FIELD. 

LOCATION.

Development work within the Kettleman Hills has been confined 

to their northern portion, all the wells started having been put down 

on the flanks of the hills at some distance from the axis of the Coalinga anticline, which runs parallel with and east of the topographic 

axis of the hills.

GEOLOGY AND INDICATIONS OF OIL.

The formations which rise to the surface in the anticline are the 

Etchegoin and Tulare, described fully under "Geology." The structure 

of the hills is that of a simple arched anticline, with low dips near 

the axis and steeper ones toward the flanks. The maximum dip on 

the northeast flank is about 31°; that on the southwest -45°. The 

late W. P. Kerr informed the senior author that he was told by one 

of the government land surveyors who visited the Kettleman Hills 

over twenty years ago that at that time the surveyor saw what he 

supposed was an oil seepage on the southeastern flank of the hills, in 

the Southeastern part of T. 21 S., R. 17 E., or the northeastern part 

of T. 22 S. ; R. 17 E. Neither Mr. Kerr nor the senior author, who 

visited this locality in 1907 and made a careful examination, was able 

to find any traces of an oil seepage in this region, although several 

places were noted where mineral waters have oozed from the rocks 

in the rainy season. It is believed that the Kettleman Hills offer 

no direct surface evidence of petroliferous deposits.

GEOLOGY OF THE WELLS.

Seven or more wells have been put down in the hills and none have 

been successful; but owing to their position and relatively slight 

depth they afford no adequate test of the territory. (See pp. 241-245 

for conclusions concerning future development.) Two wells, the 

Gibbs and Oceanic, are on the northeastern flank of the anticline; 

the others are on the southwestern flank. None are within the area 

outlined on the accompanying map as possibly productive.
CONCLUSIONS CONCERNING FUTURE DEVELOPMENT. 233

The Gibbs Oil Company's well is in the eastern part of the NW. } 

sec. 28, T. 21 S., R. 17 E., and is the farthest north of all the wells 

in the Kettleman Hills. It is about 1 mile east of the axis of the 

Coalinga anticline and starts down in beds near the top of the Etchegoin 

(upper Miocene) formation.

The Oceanic Oil Company's well is located on the northeastern 

flank of the Coalinga anticline, on one of the spur ridges running 

northeast from the main Kettleman Hills divide, in the NW. £ sec. 1, 

T. 22 S., R. 17 E. The well is 950 feet deep, starts in the uppermost 

blue-gray sands of the Etchegoin, and is said to have penetrated blue 

sands and shales and to have yielded large quantities of water.

The Stanislaus Oil Company's well in the NW. J sec. 4, T. 22 S., 

R. 17 E., is located a little less than a mile southwest of the Coalinga 

anticline and starts in beds well up in the Etchegoin formation. It 

is said to have attained a depth of about 1,000 feet without encountering any oil.

The Iowa Oil Company's well is situated in the SW. J sec. 4, T. 22 S., 

R. 17 E., not far distant from and on the same ridge as that of the 

Stanislaus Oil Company. The conditions in the two wells are practically the same, and the results obtained by both were similar.

The Florence Oil Company has two wells in the NW. \ sec. 15, 

T. 22 S., R. 17 E. They are on the southwest flank of the Coalinga 

anticline, about a mile from the axis, and near the surface penetrate 

strata at the bottom of the Tulare formation. They are said to have 

attained a depth of 720 feet and to have encountered considerable 

gas, but no oil. ,

The Esperanza Oil Company bored two wells in the SW. £ sec. 14, 

T. 22 S., R. 17 E. One was 1,100 feet deep, but was abandoned on 

account of water; the other reached 840 feet, when drilling was suspended. The wells lie on the southwestern flank of the anticline, 

over a mile from the axis, and start in the uppermost beds of the 

Etchegoin formation.

The well of the Stockton Oil Company in the NW. £ sec. 30, 

T. 22 S., R. 18 E., the farthest south of all the test wells in the hills, 

lies on the southwestern flank of the anticline about 2 miles distant 

from the axis. The well starts down in beds near the contact between 

the Etchegoin and Tulare formations, and is said to have gone to a 

depth of 670 feet with no results in the way of gas or oil.

CONCLUSIONS CONCERNING FUTURE DEVELOPMENT.

GENERAL STATEMENT.

The conclusions here to be discussed as to the course that future 

development will take in the Coalinga district are based on the belief 

that the asphalt oil, which forms the bulk of the product of the dis-
234 COALtSTGA OIL DISTRICT, CALIFORNIA.

trict, is originally derived from the shales of the Tejon (Eocene) formation and that upon migration it collects both in the sands interbeddecl 

with these shales and in the porous portions of the overlying Miocene 

formations. All the conditions indicate that this belief is well 

founded. The purple-shale member of the Chico (Upper Cretaceous), 

in which the paraffin oil is supposed to have originated, was probably 

eroded away in the central and southern portions of the district before 

the deposition of the Tejon. It is, therefore, not supposed to have 

any bearing on the future developments except in the very northern 

portion of the district.

Several factors are requisite for the accumulation of the petroleum 

and its extraction in commercial quantities. Among these are the 

following, briefly stated:

(a) An adequate thickness of the shales of the Tejon (Eocene) to 

yield commercial quantities of oil.

(&) A cause for the migration of the oil from its source in the 

organic shales. This force is believed to be supplied by the tendency 

of oil to migrate by diffusion through certain media, such as dry 

shales, and this cause may be (and doubtless is in certain instances) 

augmented by hydrostatic pressure wherever water has come in 

contact with the petroleum.

(c) Associated porous beds occupying such a position relative to 

the source of the oil and to impervious barriers as to permit the 

petroleum to pass from the source into the final reservoir and there 

to be confined by impervious strata. Wet shale or clay and certain 

fine-grained water-impregnated sands are believed to be among the 

effective barriers to the migration of the oil.

(d) Occurrence of the accumulations far enough below the surface 

and distant enough from outcrops to preclude the escape of the lighter 

hydrocarbons, and still at depths which may be profitably reached by 

the drill. The areas within the lines shown on the map as bounding 

the possibly productive territory are those in which the top of the supposed oil zone has been calculated as possibly within a vertical distance 

of 4,500 feet from the surface. A depth of 4,500 feet below the surface has been arbitrarily taken as the maximum to which it is possible 

to drill by present methods in the region under discussion, although 

it is not the maximum depth of holes in California that have been 

drilled with a Standard rig. It may be possible to go deeper than 

this, but for the present this limit seems sufficient. Whether or not 

a well can be'' profitably drilled " depends upon so many factors such 

as quantity of oil produced compared with cost of drilling and price 

of oil that local conditions must determine the result in each specific case.

It seems very unlikely that oil even in small amounts will be found 

in any of the rocks underlying the Tejon (Eocene) that is, in the
CONCLUSIONS CONCERNING EUtURE DEVELOPMENT. 235

Cretaceous or Franciscan formations (see PI. I) while it will very 

likely be found in the Tejon and in the formations immediately over-1 

lying it, whether in paying quantities depending 6n the factors 

mentioned above. In the following paragraphs it is the intention 

of the writers to give their personal opinion as to the probabilities of 

the occurrence of petroleum in those regions not yet thoroughly tested 

by the drill. It must be borne in mind, however, that absolute determination, by work on the surface, of the occurrence or nonoccurrence 

of oil in any one locality is not possible. The best that can be done is 

to calculate the degree of probability on the basis of surface indications 

and structural conditions.

TERRITORY NORTHWEST OF EASTSIDE FIELD.

The well of the T. C. Oil Company in sec. 2, T. 19 S., R. 15 E., has 

proved the productivity of the east flank of the Coalillga anticline 

almost as far north as the northern edge of the area shown on the map 

accompanying this report. Near there the beds bend from a strike 

almost due north to one N. 30° or 40° W., the dip at the same time 

steepening to 30° or more in sees. 34 and 35, T. 18 S., R. 15 E. A 

number of wells have been recently drilled near the northern edge of 

the territory mapped and have reached the top of the Eocene shale 

without obtaining petroleum in commercial quantity. The absence 

of any large quantity of oil is probably to be explained by the steepening of the dip, with the consequent decreasingly favorable conditions 

for the entrance of the oil into the Miocene sand and its accumulation 

there. The conclusion to be drawn is that the northern limit of 

productive area for the Miocene in the Eastside field has very nearly 

been reached. The untested possibility, however, still remains that 

oil may be obtained by wells sunk below the Miocene, through the 

Tejon, and into the paraffin-oil zone of the Chico.

REGION OF THE EASTSIDE FIELD.

Little need be said concerning the probable development in the 

already well-proved areas of the Eastside field, as their future may 

be inferred from the discussion of the geology of their wells. It 

should be borne in mind, however, that the lower part (and what in 

sec. 28 and the western part of sees. 22 and 27 is the richest part) of 

the oil measures has not been tested in those wells farthest down the 

dip, and should yield good returns for the extra cost of deepening if 

water is not encountered at the great depth. There is no evidence 

at present indicating that water exists at the base of the oil in this 

area. It is believed that oil in commercial quantities will never 

be found above the Big Blue in the Eastside field (a possible exception to this may be the St. Paul sand in section 34), so that wells
236 COALINGA OIL DISTRICT, CALIFORNIA.

put down where the bottom of the Big Blue would be penetrated at 

more than 4,500 feet will probably not pay.

Two factors militate against the successful exploitation of the 

southwestern flank of the Coalinga anticline immediately southwest of the developed Eastside territory. These are (a) the steep 

dip (almost perpendicular in places) of the beds, which carries the oil 

zone rapidly downward to great depths toward the southwest, and (&) 

the more locally disturbed condition of the various beds throughout 

this zone of steep dip. It is believed that at least the lower part of 

the oil zone along this flank will be found more or less productive 

wherever it can be reached; but it is also believed, and this belief 

is strengthened by the experience of those who have drilled in the 

territory, that the disturbed conditions of the beds will make shutting off the water difficult or sometimes impossible, thus hindering 

the most successful manipulation of the wells. Toward the southeast 

the dips lessen in degree, and so the conditions are somewhat more 

favorable for successful wells.

Within the area of shale and interbedded sandstone of the uppermost 

member of the Chico (Upper Cretaceous), extending from Oil City 

northward beyond sees. 29 and 30, T. 18 S., R. 15 E., locations favorable for productive wells 'are believed to remain yet undeveloped. 

Surface indications lead to the .belief that wherever in this area the 

sands interbedded with the purple-shale member of the Chico are porous they contain appreciable and in some places probably commer- | 

cial quantities of petroleum at available depths. As the quality of \ 

the oil obtained from the Chico oil zone is usually considerably higher \ 

than that found in the Miocene, small producers in the Chico area 

should pay where the same production would involve a loss elsewhere. 

It is believed that a well site so chosen that the prospective sand would 

be encountered at 600 feet or more below the surface would be the 

most favorable for exploiting this territory. Furthermore, it-is believed that productive sands in the' Tejon may be tapped by wells 

which start in overlying formations, but predictions as to favorable 

locations for such tests would be unreliable, owing to the unconformable relation of the overlying beds to the Chico.

REGION OF ANTICLINE RIDGE AND GUIJARRAL HILLS.

Along the southwestern edge of the developed territory in the 

Eastside field the axis of the Coalinga anticline pitches southeast at 

about 9 ° at least as far southeast as the northwest corner of section 

12 and probably as far as the southeast corner of the same section. 

From section 12 toward the southeast the anticline is believed to 

flatten to the region of the Guijarral Hills, where it rises toward the 

Kettleman Hills. The productive territory will be limited to that
CONCLUSIONS CONCERNING FUTURE DEVELOPMENT. 237

portion of the anticline where the productive sands lie at a depth to> 

be profitably reached by the drill.

In drawing conclusions as to just how far southeastward along the> 

axis of the anticline this limit will be, two factors have to be taken, 

into consideration (a) pitch of the anticline and (6) thickening of 

the formations, toward the southeast.

With regard to the first factor (a), evidence furnished by wells indicates a pitch of about 9°, or 1,000± feet to the mile.

With regard to the second factor (&), a conservative estimate indicates that at its nearest point to the surface in the northern portion 

of the Kettleman Hills the top of the oil-bearing zone may lie within 

3,500 feet of the surface. This estimate assumes that the formations 

above the oil-bearing Vaqueros are considerably thicker than the; 

same formations in the Eastside field. Just where this thickening;

of the beds begins it is not possible to find out, but it is believed to be 

toward the lower end of Anticline Ridge that is, along the Coalinga 

anticline a little north of the railroad. All the evidence considered,, 

it seems probable that the pitch indicated by the contours on themap that is, 9°, or 1,000 ± feet to the mile along the anticline is the 

average as far southeastward as the southeast corner of sec. 12, T. 20 

S., R.15 E., and probably much less in the region of the Guijarral 

Hills. Owing to the much steeper dip on the southwest flank of 

the anticline than on the northeast, the productive ground will 

be found to extend much farther away from the axis on the latter 

flank than on the former, as indicated by the contour map.

REGIQN OF THE WESTSIDE FIELD.

Owing to the rapid thinning and even entire pinching out of the 

Vaqueros or lower Miocene oil-bearing formation toward the western 

edge of the Westside field, predictions as to the exact depths at which 

the top of this formation will be encountered at any particular point 

are unusually hazardous. For this reason the top of the lowest 

petroliferous zone (zone B) of the Santa Margarita (?) and Jacalitos 

(upper Miocene) was chosen for contouring, as it extends over the whole 

region, although at both the north and the south ends of the field it is 

not commercially productive. No reasons are known at present for 

believing that any of the territory is unproductive in the main portion 

of the Westside field under which the productive measures lie at a 

greater depth than 500 feet. Local conditions, such as the extreme 

thinness of the shale or clay separating water from oil sands, may 

make the manipulation of certain wells more or less difficult or possibly 

unsuccessful, but there is no evidence of " bottom" or "edge" water in 

any of the wells so far drilled that condemns any of the territory generally considered as proved. On the contrary, evidence is available 

indicating that in many of the wells which have penetrated but a short
238 COALINGA OIL DISTRICT, CALIFORNIA.

distance into the oil-bearing zone there are underlying and untouched 

sands even more productive than those already developed. It is the 

belief of the writers that in this field, as in the Eastside, the sands are 

more productive the nearer they lie to the brown shale of the Tejon. 

It seems worth while, therefore, in those areas where conditions are 

such that water could be plugged off, if encountered below the already 

tested productive sands, to deepen to the beds immediately overlying 

the brown shale. Such a procedure, however, will require great care 

to avoid the flooding of the upper productive beds, if water should 

happen to be encountered in the oil-bearing series of beds.

It is believed that considerable commercially productive territory 

is yet untested in the southwestern portion of the Westside field, 

especially north and northeast of the fault (see map, PI. XV), which 

extends east and west through the middle of the SW. J sec. 12, T. 21 

S., R. 14 E. The extent of this productive area is believed to depend 

on whether the various Miocene sands are underlain by the Tejon 

(Eocene) formation or the Knoxville-Chico (Cretaceous). It is believed that if they are underlain by the Tejon, the beds will be 

found commercially productive; if by the Knoxville-Chico, except 

within half a mile or so of the contact between the Tejon and the 

Knoxville-Chico, that the oil sands will be dry or only poorly saturated. Direct evidence of the trend of the contact between the 

Knoxville-Chico and Tejon ends in the southwest corner of sec. 26, 

T. 20 S., R. 14 E., because farther south it is entirely covered by the 

later formations. At that locality its direction is about S. 25° E., 

but this strike is believed to swing eastward, so that the contact 

passes north of the corner of-sections 1, 12, 6, and 7. The partial 

failure of the well in the SE. \ sec. 12 is believed to be due entirely 

to local conditions accompanying the fault north of the well, while the

water in the well in the same quarter section comes from beds believed 

to be Knoxville-Chico.

REGION OF THE JAGALITOS ANTICLINE.

The first locality south of the southwest corner of sec. 26, T. 20 S., 

R. 14 E., where the Tejon (Eocene) formation is definitely known is 

in Sulphur Spring Canyon, in the southern part of sec. 23, T. 22 S., 

R. 15 E. As mentioned above, there is evidence that the contact 

between the Knoxville-Chico and the Tejon passes north of the corner 

of sees. 1 and 12, T. 21 S., R. 14 E., and sees. 6 and 7, T. 21 S., R. 15 E. 

Just how the contact trends between this corner and the Sulphur 

Spring Canyon locality is not definitely known, but it is the belief of 

the writers, after a study of the intervening region, that the contact 

soon bends south after passing into the northern part of sec. 7, T. 21 

S., R. 15 E., and swings around to a southwesterly trend, continuing 

down to Sulphur Spring Canyon, in a way somewhat similar to that
CONCLUSIONS CONCERNING FUTURE DEVELOPMENT. 239

followed by the later beds, now exposed over the area. The relation 

of the whereabouts of this contact between the Knoxville-Chico and 

Tejon to the future development of the region is obvious when it is 

remembered that only those portions of the Miocene sands which 

overlie the Tejon (Eocene) are believed to be productive! It is the 

opinion of the writers, therefore, that the basal Miocene sands are 

likely to be commercially oil bearing only in the area northeast of a 

line which passes in a general way southwestward from the eastern 

part of sec. 7, T. 21 S., R. 15 E., to sec. 23, T. 22 S., R. 15 E. Southward from Alcalde Canyon the formations which overlie the oil-bearing Vaqueros thicken rapidly until, in the region of Jacalitos Creek, the 

Jacalitos formation (upper Miocene) alone is 3,500 feet thick, whereas 

in the Alcalde Canyon region it is less than 1,500 feet. This great 

thickening of the beds above the oil zone toward the south necessitates much deeper wells than would be required if the formations

were uniform." It is estimated that at the axis of the Jacalitos anticline on Jacalitos Creek, where the supposedly productive zone 

approaches nearest the surface, the top of the Vaqueros is about 

3,600 feet below the surface. As the axis plunges northward north 

of the creek and southward along the anticline from the high 

hill immediately south of the creek, it is obvious that the territory of 

possible development is very limited. The northeast flank of the 

Jacalitos anticline dips much more steeply than the southwest flank, 

so that the band of productive ground on the northeast will be much 

narrower than that on the southwest. Owing to the uncertainties 

incident to the complicated structure at the north end of the Jacalitos anticline, in sec. 18, T. 21 S., R. 15 E., and the rapid rate of 

thickening of the beds southward, quantitative statements concerning the depth of the oil zone below the surface at any one point will 

not be attempted for the region south of Alcalde Canyon. A suggestion as to the probable depth at which the oil zone lies may be gathered from the statement that it is struck at about 700 feet below sea 

level (1,600 feet below the surface) in the NW. J sec. 18, T. 21 S., R. 

15 E., and as before stated is probably some 2,800 feet below sea 

level (3,600 feet below the surface) on the axis of the anticline on 

Jacalitos Creek. This great increase in depth exists despite the fact 

that the axis of the anticline pitches northwest, near its northwest 

end as much as 15°.

REGION OF REEF RIDGE SOUTH TO DAGANY GAP.

The great monocline of Tertiary beds which flanks Reef Ridge on 

the east and forms the Kreyenhagen Hills is underlain by the Tejon 

formation from a point at least as far north as Sulphur Spring Canyon 

(in sec. 23, T. 22 S., R. 15 E.) to the head of Little Tar Canyon (in 

sec. 35, T. 23 S., R, 17 E.). Nearly throughout the extent of this
240 COALINGA OIL DISTRICT, CALIFORNIA.

Tejon band it shows unmistakable signs of petroleum contents. Oil 

also seeps in many places from the Vaqueros sands overlying the 

Eocene, so that there is no doubt of the presence of petroleum 

practically throughout the length of the region under discussion. 

Furthermore, productive wells on Canoas Creek, in Big Tar Canyon 

and elsewhere (see pp. 227-232), have proved the presence of oil in 

commercial quantities in at least certain localities. Although the 

territory does not promise large individual productions the writers 

believe that productive wells may be put down along practically 

the whole strip from the region between Jacalitos and Canoas 

creeks to Little Tar Canyon. West of Jacalitos Creek the Tejon is 

apparently lacking or else is thin and insignificant; southeast of the 

head of Little Tar Canyon the Tejon is cut off by the Castle Mountain 

fault. It is therefore not likely that the productive sands extend 

far either northwest of Sulphur Spring Canyon or southeast of the 

head of Little Tar Canyon. There are indications of petroleum in 

the axis of the Pyramid Hills anticline, southeast of Dudley, and 

still farther southeastward toward the Devils Den country, so that 

the extension of the productive belt in a southeasterly direction 

from Little Tar Canyon is probably only locally affected by the fault. 

It is to be expected that the lighter oil will be found in the Tejon 

formation, but the best production will doubtless be found in the 

sand of the Vaqueros (lower Miocene). The production in either ^ 

case will probably not be large, for the steep dip of the beds pre- j 

eludes the conditions necessary for great accumulations of oil. The \ 

steep dip, however, so increases the distance through which the wells j 

may penetrate the sand that the lack of complete saturation may be \ 

partly compensated for by increased exposure of sand in the well. \ 

An item that should not be overlooked in drawing conclusions con- N 

ceming this strip of territory is the probable occurrence of water in 

or closely associated with the oil sands. Nearly all the oil seepages 

in the region are accompanied by water, and many of the test wells 

have been abandoned on account of it, so that trouble from this 

source should not surprise those who may undertake to exploit the 

region. The depth to which the oil sands along Reef Ridge may be 

exploited is limited by the cost of drilling plus operation, in relation 

to the production and value of the oil; and also by the source of the 

water that is apparently associated with the oil-bearing beds 

whether it is "bottom" or "edge" water. These factors are determinable only by actual test. The area outlined on the map (PL I) 

as probably productive embraces all of the territory along Reef 

Ridge in which it is thought that the top of the sands of the Vaqueros 

(lower Miocene) will be encountered at a depth less than 4,500 feet. 

At some localities seepages indicate that the productive zone is near 

the base of the formation; at other localities the evidence favors the
CONCLUSIONS CONCERNING FUTURE DEVELOPMENT. 241

theory that the top will be found the most productive. All the 

evidence seen by the writers leads to the conclusion that the productive bodies of petroleum will not be encountered in or above the 

shale of the Santa Margarita (?) formation, that is, above the top 

of the Vaqueros (lower Miocene) zone.

REGION OF THE KETTLEMAN HILLS.

The Kettleman Hills were formed by an uplift of the sedimentary 

formations of this region along the Coalinga anticline. It is an 

interesting and important problem to consider whether this great 

arch, the summit of which has subsequently been in large part worn 

away by erosion, has brought within reach of the surface the beds 

which are oil bearing a few miles away. The conditions for the 

accumulation and preservation of oil in this broad, regular, unbroken 

fold would appear to be good, and the question as to the occurrence

of valuable deposits resolves itself principally into two problems 

(1) whether the hills are underlain by the Tejon, so that oil is probably 

present, and (2) whether the oil-bearing beds are brought so near the 

surface by the anticline as to be accessible. Direct evidence can be 

obtained upon either of these questions only by the drill, owing to 

the complete hiding of the oil-bearing formations, if such there be, 

by a great thickness of overlying formations; but the geologic facts 

observed in the hills and in other parts of the district afford indirect 

evidence of considerable importance favoring the theory that the 

necessary conditions mentioned above exist.

As regards the first condition, it may be reasonably supposed that 

the Tejon formation underlies the whole of the foothill and valley 

region within at least a few miles east and southeast of its outcrop in 

the hills around Pleasant Valley and along Reef Ridge. No reason is 

known for supposing otherwise. The Great Valley has been during 

long periods of geologic time a basin of depression in which deposition of sediments and subsidence has gone on, and there is evidence 

that during the Eocene, when the Tejon formation was being deposited in the sea that covered part of the area under discussion, the present Diablo Range was, at least in part, a belt of land that stood out 

with considerable relief and formed the shore line. The sea extended 

thence eastward, and unless a belt of land rose where the present Kettleman Hills stand the formation must have been deposited over their 

area. It is possible that the Coalinga anticline is an old axis of uplift 

that determined an area of relief in previous epochs, but it is not probable. The fact that the Cretaceous beds on Joaquin Ridge are not 

more disturbed than the younger ones lapping over the anticline 

farther east indicates that no great uplift occurred along this anticline 

88170 Bull. 398 10 16
242 - COALINGA OIL DISTRICT, CALIFORNIA.

before the latest period of movements, during which all the formations were affected at the same time.

The same reasoning applies to the question whether the Tejon formation when once deposited over the area now occupied by the Kettleman Hills was worn away by erosion before the deposition of the 

younger Tertiary formations and the preservation in them of the 

petroleum. If no uplift of magnitude occurred it is not likely that the 

formation was worn away. In fact, it was probably less eroded than 

in the region farther west where it is now exposed, a region that was 

nearer the shore line and more .subject to disturbances. It may therefore be assumed as a good working hypothesis that the Tejon was originally deposited and still exists beneath the formations covering the 

surface of the Kettleman Hills. Similarly, it is to be supposed that 

the whole succession of Tertiary formations is the same beneath these 

hills as in other parts of the district. Whether or not the Tejon is oil 

bearing can not be told, but being so near the extensive area in which 

it is petroliferous the chances are good that it is likewise so beneath 

these hills.

As regards the second condition, the evidence afforded by the thickness of the formations in various parts of the district must be brought 

to bear in order to determine at what depth the oil-bearing beds lie. 

The anticline exposes along its axis a low portion of the Etchegoin (uppermost Miocene) formation, and therefore the drill will have to pierce 

the base of this formation and the whole of the Jacalitos (early upper 

Miocene) and Santa Margarita(?) (upper middle Miocene) formations in 

order to reach the petroliferous beds of theVaqueros (lower Miocene), 

provided these formations are present, as they have been assumed to 

be. The formations here probably bear a closer similarity in occurrence and thickness to the same formations on the western side of the 

Syndme along the Kettleman Plain than they do to the formations 

in the Coalinga field. The oil probably collects, as it does along Reef 

Ridge, in theVaqueros sandstone overlying the Tejon (Eocene) and is 

retarded from further upward migration by the compact shales of the 

Santa Margarita(?) formation.

The question of the thickness of each formation may be taken up 

separately, beginning with the exposed Etchegoin. This formation 

has a thickness of approximately 3,500 feet throughout the Kreyenhagen Hills, of which about 2,700 is below and 800 above the upper 

Mulinia zone. On Anticline Ridge the formation has a thickness, 

only roughly measurable, of about 1,700 feet. In the Kettleman 

Hills, inasmuch as the base is not certainly exposed, the whole formation can not be measured. The maximum thickness exposed is about 

3,000 feet, in the south-central part of the hills, along that part of the 

anticline where it pitches in both directions. Fossil beds are there 

exposed which may be close to the base of the formation. If they are,
CONCLUSIONS CONCERNING FUTUEE DEVELOPMENT. 243

the whole formation is thinner than in the Kreyenhagen Hills. In 

other parts of the Kettleman Hills, where the lowest beds exposed are 

considerably above the base, the only means of determining the comparative thickness of the formation there and elsewhere is to compare 

the thickness from the summit down to the upper Mulinia zone, which 

has been correlated with the similar zone in the Kreyenhagen Hills. 

The position of this zone in the Kettleman Hills is shown by a line on 

the geologic map (PL I). The thickness of the formation down to it 

is about 1,900 to 2,000 feet in the northern part of the Kettleman Hills, 

but is 2,300 or 2,400 feet, if not more, in the southern half, on the 

southwest flank of the anticline. Here again, therefore, there is indicated a thinning of the formation in the Kettleman Hills as compared 

with the Kreyenhagen Hills, and this gradual decrease appears to continue on the northeast side of the Kettleman Hills. On the other 

hand, there is a very decided thickening southeastward from Anticline

Ridge along the anticline. In conclusion, all that may be said is that 

the Etchegoin is at least 2,000 feet and probably more nearly 2,500 

feet thick in the northern part of the Kettleman Hills, and at least 

3,000 feet thick in the southern part. The thickness of it that must be 

pierced along the axis o°f the anticline in order to reach the underlying 

Jacalitos decreases gradually southward toward the central portion of 

the hills. At the south side of sec. 34, T. 21 S., R. 17 E., the upper 

Mulinia zone 'arches over the 'anticline and pitches northwestward 

beneath higher beds. At this point the beds are practically horizontal 

on the very axis of the fold, and the depth to the top of the Jacalitos 

is probably only a few hundred feet, possibly about 500 feet. Thence 

southeastward to sec. 1, T. 23 S., R. 18 E., the .thickening of the formation is more than offset by the pitch of the anticline in the opposite 

direction, and the depth to the Jacalitos gradually decreases. Thence 

southward the depth is probably nowhere more than a few hundred 

feet and is, in general, less than in the northern part of the hills.

In both the Kreyenhagen Hills and the Coalinga field the Jacalitos 

formation has a thickness similar to that of the Etchegoin. The 

question of the accessibility of the oil sand in the Kettleman Hills 

hinges in large measure on the question whether this similarity in 

thickness between the two formations holds good there. Does the 

Jacalitos become thinner eastward from the Kreyenhagen Hills, as 

the Etchegoin seems to? It is very probable that it does.

The shale of the Santa Margarita (?) formation increases in thickness 

from Zapato Creek to Dagany Gap from about 200 feet to over 1,000 

feet. It probably underlies the Kettleman Hills with some such 

thickness and with a probable similar thickening southward. There 

is no way of telling whether it thickens or thins eastward from the 

Kreyenhagen Hills, and it may therefore be assumed as constant.
244 COALINGA OIL DISTRICT, CALIFORNIA.

On the basis of the probable conditions outlined above the combined thickness of the lower part of the Etchegoin below the upper 

Mulinia zone and of the Jacalitos and Santa Margarita (?) formations 

may be arbitrarily assumed to be 3,500 feet in the northern part of 

the Kettleman Hills and 4,500 in the south-central part. The lines 

on the map over the Kettleman Hills showing the possible limits of 

the productive territory are drawn on the basis of such an assumption.

These figures are thought to be moderate estimates. It must be 

borne in mind, however, that they are at best only guesses based on a 

balance of probabilities. If these figures are true the top of the 

Vaqueros formation, the supposed oil sand, lies between 3,500 and 

4,000 feet immediately below the axis of the anticline throughout the 

hills southeast of the Big Tar Canyon7Lemoore road; Away from 

the axis on either side the bed begins to dip away and the depth to 

the Vaqueros increases rapidly. The lines bounding the supposed 

oil territory represent the limits of the area in which the top of the 

Vaqueros would be reached within 4,500 feet vertically down if the 

assumed thicknesses were true. On the other hand, "if the formations 

are as thick as they are in the Kreyenhagen Hills the top of the 

Vaqueros would be considerably below 4,500 feet even along the axis 

of the anticline. In the southern part of the Kettleman Hills, for a 

few miles north of Avenal Gap and in the group south of it, the 

structure is poorly displayed. Little' definite information has been 

obtained further than that the horizon exposed along the axis is in 

the lower portion of the Etchegoin. Owing to the removal of the 

Eocene by faulting near Little Tar Canyon and farther south it is 

possible that the Tejon is not present beneath the southern portion 

of the Kettleman Hills.

No surface indications of oil are known to exist in the Kettleman 

Hills, but it is not likely that oil would have been allowed to escape 

through the great thickness of overlying beds forming the regularly 

arching anticline. It is supposed also that the oil is retained by the 

overarching shale of the Santa Margarita (?) formation. Accumulations of a brownish substance resembling oxidized asphaltum have 

been observed in the Lost Hills several miles south of the southern 

end of the Kettleman Hills. The Lost Hills are clue to an extension of the Coalinga anticline southward, and it may be that the 

fold pitches northward and exposes a low portion of the series, into 

which the possible hydrocarbons have had access. Whether or not 

such a supposition is founded in fact, the presence of the oxidized 

asphaltum in the Lost Hills favors the theory that oil will be found 

in the Kettleman Hills.

In conclusion, it may be said that the Kettleman Hills offer a 

fair chance for the discovery of oil at a depth of 3,000 to 4,500 feet
AREAS CLASSIFIED AS MINERAL LAND. 245

along the axis of the anticline, and that the conditions favor a wellpreserved supply. The only possible means of gaining any definite 

knowledge of the oil-bearing formations beneath these hills is by 

drilling. In order to test the.possibilities of the region satisfactorily 

wells should be sunk on the very axis of the anticline. The most 

favorable location for a test well would probably be between the 

northernmost road crossing the hills and a point 13 miles southeast 

of the northwest end of the hills.

AREAS CLASSIFIED AS MINERAL LAND IN THE COALINGA

DISTRICT.

The following areas within the Coalinga district have been classified 

as mineral land, and such of these as yet belong to the Government 

have been withdrawn from all kinds of entry. The lands classified 

as mineral include all those lying between the outcrop of the base

of the lowest oil-bearing beds and a line marking the limits of the 

area in which the uppermost productive oil zone (zone B in the 

Coalinga field) can be reached by a well less than 4,500 feet in depth. 

The lines bounding the area so included are shown on the geologic 

map (PL I). (See pp. 233-245 for relative probability of productiveness of these lands.)

List of mineral lands in Coalinga district.

T. 18 S., R. 15 E.:

W. 4 and SE. £ sec. 36, and sees. 35, 34, and 33. 

T. 19 S., R. 14 E.:

S. i and NE. \ sec. 25, S. $ sec. 35, and sec. 36. 

T. 19 S., R. 15 E.:

Sees. 1 to 4, 8 to 17, SE. J sec. 18, and sees. 19 to 36, except NW. { sec. 19. 

T. 19 S., R. 16 E.:

W. 4 sees. 7, 18, 19, 30, and 31. 

T. 20 S., R. 14 E.:

Sees. 1 to 3, 10 to 15, 22 to 26, 35 and 36. 

T. 20 S., E. 15 E.:

All of township except sees. 14, 23, 24, 25, 26, 27, 34, 35, and 36, S. 4 sec. 13,

SE. | sec. 15, and E. £ sec. 22. 

T. 20S., E. 16E.:

W. } sees. 6 and 7, NW. } sec. 18. 

T. 21 S., R. .1.4 E.:

Sec. 1, E. 4 sec. 2, sec. 12, and N. \ and SE. \ sec. 13. 

T, 21 S., R. 15 E.:

Sees. 4 to 9, W. \ sec. 3, NW. J sec. 10, S. £ sec. 16, sees. 1.7, 18, 21, 22, NW. \ 

and S. \sec. 23, sees. 26, 27, E. £sec. 28, N. £and SE. i-sec. 34, and W. \ sec. 35. 

T.. 21 S., R. 17 E.:

Sees. 33, 34, and NW. J and S. \ sec. 35. 

T. 22 S., R. 15 E.:

SW. i sec. 5, S. \ sec. 6, sees. 7 and 8, NW. \ and S. \ sec, 9, SW. \ see. 10, 

SW. J sec. 13, NW. \ and S. \ sec. 14, sees. 15, 16, N. \ sec. 17, N. \ sec. 18, 

NW. \ sec. 22, NW. \ and E. \ sec. 23, sees- 24 and 25, and NE. \ sec. 26.
246 COALINGA OIL DISTEICT, CALIFORNIA.

T. 22 S., K. 16 E.:

NW. i and S. £ sec. 19, SW. £ sec. 20, SW. J sec. 27, NW. i and S. £ sec. 28, sees.

29 and 30, N. } sec. 31, sees. 32 to 34, and SW. J sec.-35. 

T. 22 S., R. 17 E.:

NW. I and S. } sec. 1, sees. 2 and 3, E. } sec. 4, NW. \ and E. \ sec. 10, sees. 11

and 12, NW. \ and E. \ sec. 13, and NE. \ sec. 14. 

T. 22 S., R. 18 E.:

Sec. 7, NW. .\ and S. } sec. 8, NW. J and S. } sec. 16, sees. 17 and 18, N. $ sec. 

19, sees. 20, 21, and 22, SW. J sec. 25, sees. 26, 27, and 28, NE. \ sec. 29, NE. £ 

sec. 33, and sees. 34, 35, and 36. 

T. 23 S., R. 16 E.:

S. £ sec. 1, sees. 2, 3, and 4, N. £ sec. 10, sees. 11 and ]2, and N. £ sec. 13. 

T. 23 S., R. 17 E.:

Sec. 7, S. ^ sec. 8, SW. £ sec. 15, NW. J and S. } sec. 16, sec. 17, NW. J and 

E. £ sec. 18, N. $ sec. 20, sees. 21 and 22, SW. \ sec. 23, SW. J sec. 25, sec. 

26, N. ^ and SE. £ sec. 27, NE. i sec. 35, and sec. 36. 

T. 23.S., R. 18 E.:

Sees. 1, 2, NE. \ sec. 3, E. } sec. 11, sees. 12, 13, N. \ and SE. \ sec. 24, NE. \

sec. 25, SW. J sec. 31. . T. 23 S., R. 19 E.:

W. \ sec. 6, sees. 7, 18, and 19, W. \ sec. 20, SW. \ sec. 28, sec. 29 and 30, E. $

sec. 31, sees. 32 and 33, and SW. \ sec. 34. 

T. 24 S., R. 18 E.:

SW. 1 sec. 5, sees.'6 and 7, NW..J and S. i sec. 9, SW. \ sec. 15, sec. 16, N. \ and 

SE. I sec. 17, N. } and SE. J sec. 21, NW. i>and S. } sec. 22, sec. 27, E. } sec. 

28, sec. 34, and W. £ sec. 35. 

T. 24 S., R. 19 E.:

Sees. 3 and 4, N. £ and SE. i sec. 5, sees. 9, 10, 15, 16, 21, and 22, SW. \ sec. 26, 

sees. 27 and 28, N. £ and SE. i sec. 33, sec. 34, and NW. £ and S. $ sec. 35.

PRODUCTION AND ESTIMATED SUPPLY.

The following table of production of the'Coalinga district by calendar years from 1897 to 1908 was compiled by Miss Belle Hill, under 

the direction of Dr. David T. Day, of the United States Geological Survey. The production for 1909 has probably been about 15,200,000 

barrels, which, with the greatly increased price, has brought the value 

of the product for the year close to $9,000,000.

Production of petroleum in Coalinga district, 1897 to 1908. 

[In barrels of 42 gallons each.]

Year.

1897.......................

1898.......................

1899

1900.......................

1901 .......................

1902.......................

Production.

70,140

154,000

439,372

532,000

780,650

572,498

Value.

$532,000

390,325

257,629

Year.

1903......................

1904......................

1905.....................

1906......................

1907...........:.........;

1908 ......................

Production.

2,138,058

5,114,958

10,967,015

7,991,039

8,871,723

10, 386, 168

Value.

$705,559

1,520,847

2,657,009

1,848,300

3,091,934

5,392,916

By a rough estimate, based on the data in the hands of the writerrj, 

the amount of available oil contained before exploitation began 

in that part of the Coalinga district shown on the contour map
TKANSPORTATIOF FACILITIES. 247

(PL XV) was 2,800,000,000 barrels of 42 gallons each. Of this 

amount about 2,000,000,000 barrels was contained in the territory 

west of the Coalinga syncline and 800,000,000° barrels east of the 

syncline. The total amount that has been taken from the ground 

up to the present time, including an estimated production of 15,200,000 

barrels for 1909, approaches 63,000,000 barrels, which leaves 2,737,- 

000,000 barrels available after 1909. At the present rate of production this supply would last over two hundred years, but with the 

rapid rate at which the increase in production is now taking place the 

time during which the supply will hold out promises to be far less. 

Moreover, it is not possible to state whether all the oil present can 

ever be obtained.

The estimate is, of course, merely an approximation. It was 

reached by assuming a 10 per cent impregnation of the oil.sands and 

calculating from all the data available the probable thickness of sand 

under each quarter section.

TRANSPORTATION FACILITIES.

One railroad and three pipe lines constitute the transportation 

facilities for the oil produced in-the Coalinga district.

A branch of the Southern Pacific Kailroad joins Coalinga with the 

main line at Goshen Junction, and also with the main lines of the 

Atchison, Topeka and Santa Fe Railway at Hanford and Visalia. 

The storage tanks and loading racks for the district are at Ora station, 

1£ miles northeast of Coalinga.

A 6-inch pipe line of the Coalinga Oil Transportation Company, a 

subsidiary of the Associated Oil Company, joins Coalinga with the 

seaboard at Monterey, 110 miles northwest. This line was first constructed in 1904 as an independent project and was generally known, 

from the name of its projector, as the Matson pipe line. The route 

traversed is through Alcalde Canyon, Waltham Valley, Priest Valley, 

Lewis Creek, and the Salinas Valley. Several pumping stations are 

situated along the line between Coalinga and Monterey, the main 

station being in the SW. J sec. 18, T. 20 S., R. 15 E.; it is joined 

by minor lines with various parts of the Eastside and Westside fields.

An 8-inch branch pipe line 28 miles long joins the Coalinga field with 

the main Kern River and Point Richmond line of the Standard Oil 

Company at Mendota. The total distance from Coalinga to tide 

water by this line is 198 miles. The main pumping station of this 

company for the Coalinga field is in the NW. \ sec. 36, T. 19 S., R. 15 E.

The Producers' Transportation Company, a subsidiary of the 

Union Oil Company, is now constructing an 8-inch line between

o Recent developments in the Eastside field have tended to reduce the estimate of the probable productive area so much that the original estimate of 875,000,000 barrels for this field has been cut to 800,000,000 

barrels.
248 COALINGA OIL DISTRICT, CALIFORNIA.

Coalinga and the Antelope Valley, 45 miles to the southeast, where 

it will join the main 8-inch line to the coast at Port Harford. This 

is part of a system of lines which are to join the Kern River, Sunset, 

Midway, and McKittrick districts with tide water. The distance 

from Coalinga to Port Harford by this route is a little over 100 miles, 

the line traversing Polonio, Cholame, and Cuesta passes and passing 

Dudley, Cholame, Santa Margarita, and San Luis Obispo.

The Associated Oil Company is now laying a new 8-inch line from 

Sunset through the Midway, McKittrick, and Coalinga districts via 

Mendota to tide water at San Francisco Bay. This line will be completed early in 1910.

Numerous local lines transport the oil from various parts of the field 

to the shipping stations. Among these lines are those of the Union 

Oil Company from sec. 13, T. 20 S., R. 14 E., to Ora; the California 

Oilfields (Limited), from the Eastside field to Ora; the Coalinga Oil 

Company, from the Oil City field to Ora; the Westside line, from the 

Westside field to Ora; and the Associated Oil Company, from the 

Westside field to Ora.

OIL COMPANIES AND OIL WELLS IN THE COALINGA

DISTRICT.

The following is a practically complete list of all of the oil companies and the wells which they had drilled or were drilling in the 

Coalinga district up to October 15, 1909. The locations of the wells 

are indicated wherever known, and the elevations of most wells are 

given, having been obtained by instrument survey by E. P. Davis, 

topographer. A table following this one' shows the narhes of companies and. the number of wells in the Coalinga district April 30, 1909.

Oil companies and oil wells in Coalinga district.

[Location by Mount Diablo meridian.]

Name of oil company.

.Etna. (See California Oilfields, Ltd.)

Aladdin. (See Coalinga Aladdin.)

Do........................

Do........................

Do........................

Do........................

Do..........'..............

Do........................

Do........................

Do........................

Do

Name of well.

a Abandoned.

No. of 

well.

ol

1 

2 

3

4

6 

7 

8 

632 

1

Location.

SW. isec.32,T.19S.,R.15E. 

SW. isec. 18, T.20S./R. 15E.

.....do........................

.....do........................

.....do........................

NW.' J sec. 18, T. 20 S., R. 15 E.

.....do.. ......................

.....do........................

.....do........................

.....do........................

S W. i sec. 19, T. 20 S., R. 15 E . 

6 Drilling.

Elevation 

above 

mean sea 

level.

Feet.
OIL COMPANIES AND OIL WELLS. 249 

Oil companies and oil wells in Coalingu district Continued.

Name of oil company.

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do... ...... ...............

Do........................

Do........................

Angelas. (See Traders.)

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

'Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........\.. .............

Do........................

Do..............'..........

Do........................

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do. .......................

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do.........................

Do........................

Do........................

Avon. (See California Oilfields, Ltd.) 

B. and B .....................

Do........................

Do........................

Name of well.

North Thirty.........

.....do................

.....do................

.....do................

Porter & Scribner.....

......do................

.....do................

.....do................

.....do................

.....do................

.....do................

.....do................

.....do................

.....do................

Old No. 1.............

Old No. 2.............

Old No. 4.............

Old No. 3.............

Old No. 5. ............

0

Old No. U. ...........

Old No. 13............

Old" No. 15............

Old No. 45............

Old No. 43............

Old No. 41............

Old No. 17. ...........

Old No. 19............

Old No. 21............

Old No. 23............

Old No. 39............

Old No. 37............

Old No. 25............

Old No. 27............

Old No. 29............

Old No. 31............

Old No. 32............

Brix and Buntin.. . . . .

No. of 

well.

2

3

4

ofc

a 12

a 16

1

2

3

4

6

07

"13

a I

02

a 3

1

1

&2

3

4

5

6

7

1

2

3

04

1

2

3

4

1A

IB

1C

2A

3A

4 A

4B

4C

5A

SB

5C

6A

6B

CC

7A

7B

7C

7D

8ASB"

8C

8D

9A

9B

9C

9D

8E

8F

9E

9P

9G

9H

91

62

1

2

3

Location.

SW. Jsec. 19, T. 20 S.,R. 15 E. .

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

SW. J sec. 30, T. 20 S., R. 15 12.

.....do........................

.....do........................

.....do........................

N W. J sec. 30, T. 20 S., R. 15 K .

.....do........................

SW. \ sec. 30, T. 20 S., R. 15 E .

.....do........................

NW. J sec. 30, T.20S.,R.15E.

.....do........................

.....do........................

.....do................... ....

SE. i sec. 0, T. 21 S., R. 15 E. .

NW.Jsec.7, T.20S..K.15E..

.....do........................

.....do........................

.....do........................

N E. J sec. 7, T. 20 S., R. 15 E . .

.....do........................

S E. J sec. 14, T. 20 S., R. 14 E . .

.....do.......:................

.....do........................

.....do........................

S W. isec. 22, T. 19 S., R. 15 E . .

.....do........................

....do........................

.....do........................

.....do........................

SE. Jsec. 30, T. 20S., R. HE...

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

NE. \ sec. 30, T. 20 S., R. 14 E .

.....do........................

.....do........................

.....do........................

.....do........................

.....do............. ...........

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do.........................

.....do........................

.....do........................

NW. \ sec. 36, T. 20 S., R. 14 E .

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

Sec. 18, T.23S., R. 17 E......

SE. Jsec. 12, T. 20 S., R.HE.

.....do........................

.....do........................

Elevation 

above 

mean sea 

level.

Feet.

873

868

848

i,255

1,235

1,223

1,208

1,144

835

875

C34

831

828

800

814

828

843

858

848

852

a Drilling. Abandoned.
250 COALINGA OIL DlsJTEICT, CALIFORNIA.

Oil companies and oil wells in Coalinga district Continued.

Name of oil company.

Do........................

Do......... :..............

Do........................

Best Yet........ ...............

BlueDiamond. (SeeMcQuigg 

& Wren.)

Do........................

Do........................

Do.........:..............

Do........................

Do.......................

Do........................

Do........................

Do... .....................

Do........................

Buena Vista. (SeeKettleman 

Hills.) 

Buntin. (See British Consolidated.)

Do........................

Do........................

Do........................

Californiaand New York (See 

British Consolidated.) 

California Diamond. (See 

British Consolidated; also 

W. M. & M.) 

California Monarch. (See 

British Consolidated.) 

California Oil and Gas .........

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do................/.......

Do........................

Do........................

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Name of well.

Brix and Buntin .....

.......................

California Diamond 

No. 5. 

California Monarch 

No. 1. 

California Monarch 

No. 2. 

California-New York . . 

.....do................

.....do. ...............

.....do................

.....do................

.....do................

California Diamond 

Buntin No. 1.

T P

Avon, No. 2...........

Arline, No. 2 .........

Northeastern, No. 1 ...

.....do................

.....do................

No. of 

well.

4 

5 

6 

8 «1

ol

""a 2'

61 

ol

1

ol 

61

61 

1 

62

1 

2 

3 

4 

5 

6 

al

1

a2 

3 

4

al 

i 621

2 

3 

4 

5 

1 

2 

3 

4 

5 

6 

7 

8 

9 

1 

2 

3 

4 

1 

2 

3 

1 

2 

3 

4 

5 

6 

7

Location.

SE. lsec.l2,T.20S.,R.14E..

....do........................

....do........................

....do........................

NE. J sec. 11, T. 23 S., R. 16 E . .

Sec. 1, T. 21 S., R. 14 E.......

NW. Jsec. 18, T. 21 S., R. 15E . . 

N W. i sec. 33, T. 22 S., R. 16 E . 

NW. Jsec. 14, T. 21 S., R. 15 E .

NE. J sec. 20, T. 19 S., R. 15 E . .

SE.Jsec.,6 T.19S.,R.15E... 

S W. J sec. 10, T. 19 S., R. 15 E. .

SE. J sec. 24, T. 19 S., R. 15 E.. .

NE. Jsec. 18, T. 21 S., R. 15 E . .

SW.Jsec.l2,T.19S.,R.15E. T 

SE.Jsec.26,T.19S.,R.15E... 

.....do........................

SE.Jsec'.12,T.20S.,R.14E... 

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

NW. J sec. 24, T. 21 S., R. 15 E .

NE. J sec. 26, T. 20 S., R. 14 E . . 

.....do........................

.....do........................

.....do........................

SE.}sec.l9,T.19S.,R.15E...

NE.Jsec.6, T.21S..R.15E... 

.....do........................

SW.Jsec.14, T. 19 S.,R. 15 E.. 

N W.J sec. 14, T. 19 S., R. 15 E.. 

NE. J sec. 14, T. 19 S., R. 15 E . . 

.SE. J sec. 14, T. 19 S., R. 15 E.. . 

NW. J sec. 14, T. 19 S., R. 15 E..

SE. i sec. 21, T. 19 S., R. 15 E.. . 

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

NE. J sec. 21, T. 19 S., R. 15 E . . 

SW. Jsec. 26, T. 19 S., R. 15 E.. 

N W. J sec. 26, T. 19 S., R. 15 E. 

NE. Jsec. 26, T. 19 S., R. 15 E. 

S W. J sec. 26, T. 19 S., R. 15 E . .

NE. J sec. 10, T. 19 S., R. 15 E . .

SE. J sec. 10, T. 19 S., R. 15 E . .

NE. J sec. 10, T. 19 S., R. 15 E. 

N W. J sec. 27, T. 19 S., R. 15 E. 

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

Elevation 

above 

mean sea 

level.

Feet.

847

802 

954 

889

834 

848 

829 

835 

843

882 

880 

847

842

759

1,101 

1,035 

877 

950 

856 

1,451 

1,322 

1,444 

1,340 

' 1,429 

1,461 

1,377 

1,383 

1,368 

1,007 

1,028 

956

1,387 

1,363 

1,349 

1,353 

1,380 

1,214 

1,331

a Abandoned. 6 Drilling.
OIL COMPANIES AND OIL WELLS.

Oil companies and oil wells in Coalinga district Continued.

251

Name of oil company.

California Oilfields, Ltd. ......

Do........................

Do........................

Do........................

Do. .......................

Do........................

Do........................

Do........................

Do......'..................

Do........................

Do........................

Do........................

Do........................

Do................:.......

Do........................

DO.. .............. ........

Do........................

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do. .......................

Do........................

Do........................

Do..,........'.............

Do........................

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

DO..:.............,.......

Do.... 1....................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do. ...:...................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Call...........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Name of well.

:

.flStna, No. 1..........

Forty, No!.......'....

Missouri Coalinga, No. 1

Westmoreland, No. 3..

Forty, No. 3... ........

No. 1. '

Octave, No. 2.........

No. of 

 well.

10

11

13

14

15

16

17

18

19

9fl

21

99

23

?Aoc

20

627

28

29

on

31

QO

oq

634

35

36

37

00

39

41

42

43

AK

46

47

48

49

V\

51

52

53

54

655

650

657

658

659

660

62

664

9

2

3

4

5

6

7

1

2

63

1

2

3

64

65

Location. 

NW. i sec. 27, T. 19 S., R. 15 E.

.....do........................

.....do........................

.....do........................

SW. Jsec. 27, T. 19 S., R. 15 E.

N W. i sec. 27, T. 19 S., R. 15 E .

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

SW. \ sec. 27, T. 19 S., R. 15 E.

.....do........................

.....do........................

SE. fsec. 27, T. 19 S., R. 15 E.

SW.Jsec.27,T.19S.,IU5E.

NW. i sec. 27, T. 19 S., R. 15 E .

SE.Jsec. 27, T. 19S.,R. 15 E.

NW.isec.27, T. 19 S., R. 15 E.

.....do........................

SW.lsec.27, T. 19 S.,R. 15 E.

.....do........................

.....do........................

NE. i sec. 27, T. 19 S., R. 15 E.

NW. J sec. 27, T. 19 S., R. 15 E.

NE.isec.27, T. 19 S., R. 15 E.

SW. j sec. 27, T. 19 S., R. 15 E.

.....do........................

.....do........................

N W. J sec. 27, T. 19 S., R. 15 E .

NW. Jsec. 27, T. 19 S., R. 15 E.

S W. J sec. 27, T. 19 S., R. 15 E .

.....do........................

.....do........................

NW. i sec. 27, T. 19 S., R. 15 E.

.....do.......................'.

NE.-tsec. 27, T.19S..R. 15 E.

SW. J sec. 27, T. 19 S.', R. 15 E.

SE. Jsec. 27, T. 19S..R. 15E..

NW.}sec,27,T. 19S.,R. 15 E.

NE. Jsec. 27, T. 19 S.. R. 15 E.

SE. Jsec. 27, T. 19S..R. 15 E..

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

NE.Jsec.27,T. 19S..R. .15 E..

.....do........................

.....do........................

SW.isec.29, T. 19 S., R. 15 E.

.....do........................

SE. -1- sec. 30, T. 19 S., R. 15 E.

NW. i sec. 34, T. 19 S., R. 15 E.

NE. J sec. 34, T. 19 S., R. 15 E.

NW. Jsec. 34, T. 19 S., R. 15E. .

.....do........................

NE.$sec.34,T.19S.,R.15E...

NW. Jsec. 32, T. 19S.,R.15E.

....do........................

....do........................

NE. }sec.22,T. 198..R.15E.

....do........................

....do........................

....do........................

Elevation 

above 

mean sea 

level.

Feet. 

1,305

« 1,080

"1,340

"1,284

a I 130

a 1,270

a 1,225

"1,229

1,332

1,340

1,250

1,307

1,117

1,144

1,105

1,238

1,246

983

1,257

1,188

1,194

1, 160

1,260

1,022

1,168

"1,180

1,271

1,225

"1,350

1,217

i ocf:

1,225

1,118

l.,096

1,109

1, 150

1,085

1,061

1,080

1,213

1 212

1,208

" Approximate. 6 Drilling.
252 COALINGA OIL DISTRICT, CALIFORNIA.

Oil companies and oil wells in Coalinga district Continued.

Name of oil company.

Call.!.........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Carmelita. .................... 

Circle.........................

Do........................

Do.:......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do.............:..........

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Coalinga Aztec ................

Coalinga Crystal .............. 

Coalinga Gem. ................ 

Coalinga Great, Western. ......

Do........................

Do........................

Coalinga Pacific. ..............

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do.......................

Name of well.

suraers, No. 1.

sumers, No. 2.

sumers, No. 3.

E. W. Risley.........

Z.L.Phdps. .........

.....do................

"

No. of 

well.

1

1

2

3

4

5

6

7

8

9

10

11

12

13

a 1 

1

1

2

3

4

5

6

10

11

12

13

14

1

al

2

«2

3

3

4

5

6

7

9

1

<a

cl

Vi

9

2

c3

cl

1

2

3

4

5

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

cl6

1

2

Location.

NW. t sec. 32, T. 19 S., R. 15 E .

SW. Jsec. 22, T. 19 S., R. 15 E. .

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do. .....................

.....do...V...................

.....do........................

.....do........................

.....do........................

.....do.. ......................

SE. Jsec. 3, T.20S.,R. 15 E.... 

N E. Jsec. 35, T. 20 S., R. 14 E . .

NE. Jsec. 24, T.20S., R.14E..

.....do........................

.....do........................

.....do.:......................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

NE. Jsec. 4,T.20S.,R.15E..

NW. Jsec. 20, T. 19 S., R. 15 E .

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

NE. J sec. 6, T. 21 S., R. 15 E . .

SE. Jsec.31,T. 19S.,R. 15 E.. 

NW. i sec. 8, T. 20 S., R. 15 E .

NW.|sec.l2,T.21S.,R.14E. 

E.*sec.l8,T.21S.,R.15E...

NE'. J sec. 12 T. 21 S., R. 14 E .

.....do........................

NE. J sec. 26, T. 20 S., R. 14 E.

.....do........................

N W.i sec. 12, T. 20S..R. 15 E.

N. Jsec. 8, T. 20 S., R. 15 E . .

NW.Jsec.7,T.20S.,R.15E...

.....do........................

.....do........................

.....do........................ .....do..........:.............

N W. Jsec. 22, T. 19 S., R. 15 E .

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do.........................

.....do..:.....................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

NE. J,sec. 14, T.20S., R.14E..

.....do........................

Elevation 

above 

mean sea 

level.

Feet. . 

1,213

1,399

1,356

1,357

1,417

1,391

. 1, 400

1,297

1,234

1,204

1,233

1,313

1,116

1,309

6810

&814

"80S

792

1,022

» 1, 405

. 1,453

<> 1, 410

1,453

1,421

1,449

1,465

1,435

1,579

1,499

787

"850

880

883

910

873

1,362

1,284

1,363

1,360

1,260

1,259

1,261

1,212

1,224

1,168

1,259

1,150

870

878

o Abandoned. Approximate. : Drilling. d Water well.
OIL COMPANIES AND OIL WELLS. 

Oil companies and oil wells in Coalinga district Continued.

253

Name of oil company.

Do........................

Do........................

Do........................

Do........................

Do........................

Coalinga Southern. (See Yellowstone.)

Do........................

Do........................ DO......;....;............

Do........................

DO........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Confidence. ...................

Do........................

Do........................

Do........................

Do........................

Do........................

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Consolidated Oil and Development.

Crescent......................

Do........................

Do........................

Do........................

Domengine. .................. 

El Capitan (now Kern Trading 

and Oil).

Elk........................... 

Ellis. (See W. M. & M.)

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do

Name of well.

KandC, No. 5........

'R.'H'.HerronVNo.'i'.".; 

R. H. Herron, No. 2...

R.H. Herron, No. 4...

a Drilling. & Approximate.

No. of 

well.

3 

4 

5 

G 

7 

a 8

n i

1 

2

4 

5 

0

7

i

2 

3 

4 

5 

6

1 

1 

2 

3

5 

6

7 

8

n

10 

a H 

12

2 

4 

5 

6

7

Location.

NE.J-sec.l4,T.20S.,R.14E.. 

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

SE. J sec. 18,T. 21 S., R. In E . . . NE. Jsec. 12. T. 20 S., R.ME..

NE.Jsec.23,T.20S.,R.14E..

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

SW. J sec. 17, T. 19 S., R. 15 E . .

.....do........................

SE.Jsec. 17, T.19S..R.15E.. 

SW. Jsec. 17, T. 19 S., R. 15 E. . 

.....do... .....................

SE. Jsec. 12, T.21S., R.14E..

.....do.. ......................

NE.Jsec.31,T. 19S..R.15E..

.....do. .....'..................

.....do.........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

do

Elevation 

above 

mean sea 

level.

Feel.

887 

883

968 

977 

960 

910 

887 

960 

809

l> 1 . 450 

b 1 , 450 

1,451 

1 , 469 

1,485 

1,533

869 

1,236 

1,243 

1.242 

1,253 

1,244

I, '259 

1,254 

1,239 

1,220

do ' N W. Jsec. 31, T. 19 S., R. 15 E. 

.....do........................

SW. Jsec.31,T.19S.,R.15 E.. 

N W. Jsec. 31, T. 19 S., R. 15 E. 

... .do........................

8 SW. Jsec.31,T.19S., R.15E.. 

9 .. do...... ...............

10 

11 

12 

a 13

a 14

c 1

1 

2 

3 

4 

1

"""2" 

n\

1 

2 

3

4 

5 

6

7 

8

9 

e Aba

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

NE. jsec. 10,T.23S., R. 16 E..

NW.isec.18, T.21 S..R.15 E. 

SE. Jsec.20,T.19S.,R.15E.. 

SE.Jsec.l,T.20S.,R.14E...

.....do........................

.....do........................

SE. Jsec.6,T.21S.,R.15E... 

NE. Jsec. 35, T. 18 S., R. 15 E . . 

NW.Jsec.31,T.19S.,R.15E.

NW.Jsec. 14. T.23S.,R.17E . 

NE.Jsec.22,T.19S.,R.15E..

NE. t sec. 32. T. 13 S., R. 15 E. 

SW.Jsec.(i,T.20S.,R.15E... 

.....do........................

.....do.........................

.....do........................

.....do........................

.....do........................

.....do........................

SW. 1 sec. 14, T. 22 S., R. 17 E . .

b 1 . 280 

1- 1 , 275 

1,101 

1,240 

1,236 

1,251 

1, 190 

1 , 227 

1,171 

1 , 203 

1,205 

1.243

""""917 

911 

941 

738

777

 -,jgj

989 

972 

956 

981 

943 

936

916

SW. J sec. 6, T. 20 S., R. 15 E ............

ndoned. d Water well.
254 COALIFGA OIL DISTRICT, CALIFORNIA.

Oil companies and oil wells in Coalinga district Continued.

Name of oil company.

Do........................

Euclid. (See Traders.)

Forty. (See California Oilfields, Ltd.)

.Do........................

Do........................

Do........................

Do........................

. Do........................

Do.........................

nia Oilfields, Ltd.)

Do........................

Do.................-...:..

Do........................

Guthrey. (See Saner Dough.)

Henshaw. (SeeSunnyside.) 

Herron, R.H. (SeeCypress.)

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

DO.......................:

Do........................

Do........................

Do........................

Do.....-.--.-......--.....

Do........................

Do........................

Do........................

Do.........................

Do........................

Independence. (See Standard.)

Investment. ..................

Do........................

K. and C. (See Confidence.) 

Kaweah. (See California Oilfields, Ltd.)

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do................'........

Do........................

Name of well.

Octave.............. .

No. of 

well.

10

11

0.1

62

1

2

3

4

5

6

7

61

al

61

1

61

1

2

3

3

62

62

 1

2

3

4

K

. 6

7

8

1

o

3

4

5

6

7

8

9

11

12

61

62

63

64

61

61. 

61

al

1

a2

a 22

a 25

1

4

1

2

65

66

 7

8

Location.

SW.Jsec.6,T.20S.,R.15E...

Sec. 30, T. 21 S..R.15E. ......

NW.lsec.l5,T.22S.,R.17E .

NE.Jsec.l,T.20S.,R.14E...

.....do........................

.....do........................

.....do........................

.....do.l......................

.....do.............:..........

.....do................:.......

NW.Jsec.28,T.21S.,R.17E.

NE.isec.l2,T.22S.,R.15E..

SE.isec.30,T.19S.,R.15E..

NE. £ sec. 22, T. 19 S., R. 15 E.

SW. i sec. 26, T. 19 S., R. 15 E. .

NE.Jsec.31,T.19S.,R.15E..

.....do........................

.....do........................

.....do........................

Sec. 6, T. 21? S.,R. 15? E......

SW.Jsec.20,T.19 S..R.15E...

NE.lsec.20,T.19S.,R.15E..

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

NW.Jsec.24,T.20S.,R.14E.

.....do........................

.....do........................

.....do........................

.....do........................

.....do..................

.....do.............. ..

.....do........................

.....do........................

.....do........................

.....do........................

NE.Jsec.2,T.19S.,R.15E...

.....do. .......................

.....do........................

.....do........................

NE. Jsec. 17, T. 19 S., R. 15 E . .

SE.Jsec.l6,T.19S.,R.15E... 

SW.Jsec.4,T.22S.,R.17E...

Sec.30,T.21S.,R.15E.......

N W. J sec. 6, T. 21 S., R. 15 E . .

SE. \ sec. 3, T. 19 S., R. 15 E . . . .

.....do........................

NW. J sec. 11, T. 19 S., R. 15 E .

.....do. .......................

NW. i sec. 31, T. 19 S., R. 15 E. .

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

Elevation 

above 

mean sea 

level.

Feet.

1,140.

1,128.

1,072

1,114

1,267

1,263

1,227

1,242

cl,490

1 491

1,567

l',528

1,597

,1,519

1,585

1,593

801

811

816

799

814

805

7Q7

805

814

818

834

870

802

832

c 1,210

1,234

1,222

1,270

1,242

a Drilling. 6 Abandoned. c Approximate.
OIL COMPANIES AND OIL WELLS. 

Oil companies 'and oil wells in Coalinga district Continued.

255

Name of oil company.

Kern Trading and Oil (K. T. 

&0.)- 

Do.......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do............/...........

DO........................

Do........................

Do.....:..................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do..:.....................

Do........................

Do........................

Kreyenhagen. (See Golden 

Crest.)

Los Angeles-Coalinga Oil Syndicate.

Do........................

Do........................

Do........................

Maguire. ......................

McCreary. (See Calilbrnia 

Oilfields, Ltd.)

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Marengo. (See Traders.) 

o Drilling.

Name of well.

b Abandon?

No. of 

well.

 1 

02

all 

013

o!5

1

2 

3 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

ol6 

"20

a 22

1 

2. 

3 

4 

9 

10 

11 

15 

18 

20 

22 

24 

25 

35 

37 

39 

41 

43 

45 

47 

49 

51 

53 

54 

ol 

a3 

o5 

al 

61 

61 

61 

62

61 

ol

1 

2 

3 

04

1 

62 

3 

4

(i 

7 

8 '9 

61

d.

Location.

NW. 1 sec. 35, T. 19 S., R. 15 E..

.....do........................

SVV. J sec. 35, T. 19 S., R. 15 E. .

.....do........................

.....do........................

S W. J-sec. 13, T. 20 S., R. 14 E . .

.....do........................

.....do....:...................

.....do........................

.....do........................

SE. i sec. 13, T. 20 S., R. 14 E. . .

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do......................;. .....do..............:.........

.....do........................

S W. t sec. 25, T. 20 S., R. 14 E . . 

.....do........................

.....do........................

.....do....!...................

N W. J sec. 25, T. 20 S., R. 14 E . .

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

NE.isec.25,T.20 S..R.14 E..

.....do........................

....'.do.-.-..... .................

.....do........................

.....do........................

.....do........................

SE. J sec. 25, T.20 S., R. 14 E . . .

.....do........................

.....do........................

.....do........................

NW. i sec. 19, T. 20 S., R. 15 E. .

.....do ........................

.....do........................

NW.isec.31,T.20S.,R.15E..

NW. 1 sec. 32, T. 19 S., R. 15 E.

NE. Jsec. 3, T. 23 S., R. 16 E. 

SW.|sec.3,T.23S.,R.16E... 

SE. 1 sec. 32, T. 22 S., R. 16 E.

NW. 1 sec. 12, T. 19 S., R. 15 E. 

N W. i sec. 6, T. 21 S..R.15E...

NE. 1 sec. 6, T. 21 S., R. 15 E. 

.....do.........................

.....do........................

.....do........................

N W. i sec. 30, T. 20 S., R. 15 E. .

NE.Jsec.31,T.19S., R.15E.. 

....do.........................

.....do.........................

....do.........................

....do.........................

SE. i sec. 31, T. 19 S., R. 15 E. 

....do. ........................

....do.........................

....do.........................

SW. Jsec. 18, T. 21 S., R. 15 E. 

c Approximate .

Elevation 

above 

mean sea 

level.

Feet.

811 

803

0

c825

770 

761

787

1,256 

c 1,300 

1,274 

1,237 

c 1,250 

1,089 

1,119 

1,119 

1,154 

900
256 COALINGA OIL DISTRICT, CALIFORNIA.

Oil companies and oil wells in Coalinga district Continued.

Name of oil company.

Do........................

Do........................

Do........................

Do........................

 Do........................

Michigan Oil and Development. 

Minnesota (now. Southern Pacific R. R.) 

Missouri-Coalinga. (See California Oilfields, Ltd.) 

M.,K.andT.. ................

Do............ ............

Mount Hamilton Land and. 

Oil.

Nathan. (See Arica.)

Do. ........................

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do........................

New Home. (See St. Elmo.)

Do........................

Do.........................

Do........................

Do.........................

Do........................

Do........................

Do........................

New York. (See Highland.) 

Norse. (See Traders.) 

Northeastern. (See California 

o Oilfields, Ltd.). 

Oceanic.......................

Octave. (See Cam well.) 

Oil City Petroleum. (See 

Standard.) 

Old Keystone. ................

Oyama. (See California Oilfields, Ltd.)

Do........................

Do.................. ......

Do........'...............-

Do.......................

Do.......................

Do.......................

Do........................

Do........................

Philadelphia and San Francisco. 

Do.......................

Do.......................

Pilot.........................

Do........................

Do........................

Do.. ......................

Do....... .................

Pittsburg-Coalinga. (SeeCalifornia Oilfields, Ltd.) 

a Drilling.

Name of well.

St. Clair....... ........

6 Abandon

No. of 

well.

ol

1 

M 

1 

2 

3 

4 

5 ol

62

1 

2 

61 

61

1 

61

1 

a2

ol

ol 

1 

a2

0.4

aS

1 

2

1

9

3 

4 

5 

6 

7 

8

41

61

1 

2 

3 

4 

t>l 

a\ 

1 

2 

3 

4 

5 

6 

1

2 

3 

63

1

2 

3

4 

5 

1

3d.

Location.

SW.Jsec.6,T.21S.,R.15E...

NE.lsec.14, T.20S.,R.14E.. 

....do........................

SE. I sec. 14, T. 20 S., R. 14 E. 

NW.isec. 6,T.20S.,R. 15 E.

....do.........................

.....do.........................

.....do........................

Sec. 17?, T. 19. S., R. 13 E.....

NE. 1 sec. 33, T. 19 S., R. 15 E. 

SW. isec. 8, T. 20 S.', R. 15 E.

NW. isec.22, T. 19 S., R. 15 E. 

SE. i sec. 14, T. 21 S,|, R. 14 E.

SW. i sec. 6, T. 21 S., R. 15 E.'. . 

SE. i sec. 20, T. 19 S., R. 15 E.

SE.Jsec.26, T. 21 S., R. 14 E...

.....do........................

NE.Jsec.18, T. 20 S..R. 15 E . W. J sec. 20, T. 20 S., R. 15 E . . .

SE. i sec. 30, T. 20 S., R. 15 E...

.....do........................

NE.Jsec.30,T.20S.,R.15E..

SE. isec. 12, T. 20 S., R. 14 E. 

.....ao. .......................

NW. J'sec. 6, T. 20 S., R. 15 E.. 

.....do.........................

.....do.........................

.....do.........................

.....do.........................

.....do. .......................

.....do........................

.....do........................

NW. Jsec. 1.T.22S..R. 17 E..

SE.Jsec.8, T. 19S..R. 15E..

NE. 1 sec. 26, T. 20 S. , R. 14 E . . 

.....do.........................

.....do........................

.....do........................

NE.Jsec. 10,T.20S.,R.15E.. 

Sec. 24, T. 20S..R. 14 E......

NE. i sec. 24, T. 20 S., R. 14 E . . 

SE. J sec. 24, T. 20 S., R. 14 E . .

.....do.........................

.....do........................

.....do........................

SE. } sec. 30, T. 19 S., R. 14 E . 

.....do........................

.....do........................

SE. } sec. 20, T. 19 S., R. 15 E .

S W. J sec. 12, T. 20 S., R. 14 E . 

.....do.........................

.....do.........................

.....do.. .......................

.....do.........................

SW.Jsec.24,T. 19S..R. 15 E. 

c Approximate.

Elevation 

above 

mean sea 

level.

Feet.

920

1,097 

c 1,120 

1,006 

1,002

868 

866

1,002 

939

1,135 

1,105 

1,068 

1,098 

1,079

'850 

c845

815

1,056 

976 

923 

975

1,121

1,107

830
OIL COMPANIES AND OIL WELLS. 

Oil companies and oil wells in Coalinga district Continued.

257

Name of oil company.

Porter & Scribner. (See Arica.)

DO..........:.............

Producers and Consumers. 

(See Coalinga.)

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do.........'...............

Do........................

Riverside. (Neai Alcalde.) 

Roanoke. ....................'. 

Rock..........................

Do

Do........................

St. Elmo... ...................

Do........................

Do........................

Do........................

Do........................

St. Francis. (See Muriel.)

Do........................

Do........................

Do........................

Do................:.......

Do.......... 1;.............

Do........................

Do........................

Do........................

Santa Clara. ..................

Do........................

Do........................

Do. .......................

Do. .......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do. .......................

Do........................

Do........................

Do........................

Do... ......i. ...... '.......

Do........................

Section Six. (See Jefferson.)

Selma. (See Section One.)

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Sliver Tip....... ..............

Do........................

Southeastern. .................

Name o'f well.

.....do.................

.....do.................

.....do.................

.....do.................

.....do.................

.No. of 

well.

1

2

1

2

1

2

3

4

65

66

67

61

cl 

Cl

1

5

6

1

2

4

5

cl

1

2

3

4

5

6

7

8

9

cl 

1

2

3

4

c

e

7

8

9

10

1

1

q

4

65

60

cl

1

2

4

E

1

3

4

5

1

1

62

cl

61

Location.

SE.lsec.24, T. 20 S.,R. 14 E..

.....do.........................

 SE.Jsec.l4,T.20S.,R.14E...

.....do.........................

SE. J sec. 22, T. 19 S., R. 15 E . .

.....do......................... .....do.........................

.....do.........................

.....do.........................

.....do.........................

.....do.........................

NE.isec.6,T.21S.,R.15E...

SE.isec.36,T. 19S..R. 14 E.. 

SW.frsec.28,T.19S.,K.15E..

SE.Jsec. 12,T.20S.,R.14E..

SW. i sec. 12,T. 20 S., R. 14 E . .

SE.}sec.l4,T.20S.,R.14E...

.....do.........................

.....do.........................

.....do.........................

.....do.........................

NE. } sec. 12, T. 23 S., R. 16 E . .

NE. \ sec. 23, T. 20 S., R. 14 E . .

.....do.........................

.....do.........................

.....do.........................

.....do.........................

.....do.........................

.....do.........................

.....do.........................

.....do.........................

SW.Jsec.30,T.19S.,R.15E..

.....do.........................

.....do.........................

.....do.........................

.....do.........................

.....do.........................

.....do.........................

.....do.........................

.....do.........................

.....do.........................

NW.isec.6,T.21S.,R.15E..

Sec.35,T.20S.,R.14E........

Sec.l,T.21S.,R.14E.........

NW.isec. 7, T.20S.,R. 15 E.

.....do........................

.....do........................

.....do........................

.....do.........................

SW. Jsec. 10, T. 19 S., R. 15 E.

NW. J sec. 12, T. 20 S., R. 14 E.

.....do.........................

.....do.........................

.....do.........................

NE. J sec. 12, T. 20 S., R. 14 E.

.....do........................

.....do........................

.....do........................

NW.isec.6, T.21S., R. 15 E.

SE.isec.6,T.21 S..R.15E....

S W. i Sec. 12. T. 21 S., R. 14 E. .

N W. i sec. 18, T. 20 S., R. 16 E .

Elevation 

above 

mean sea 

level.

Feet. a790

1,189

1,177

812

o950

970

920

906

910

"""i,'435

1,304

1,313

1,388

1,435

1,283

1,340

^

911

915

916

908

«880

878

882

892

o910

879

853

822

o Approximate.

88170 Bull. 398 10 17

ft Drilling. c Abandoned.
258 COALINGA OIL DISTRICT, CALIFORNIA.

Oil companies and oil wells in Coalinga district Continued.

Name of oil company.

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

, DO.....................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do.......................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do................'........

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Jx.. .....................

Name of well.

Independence, No. 8. .

Oil City Petroleum,

No. 1. 

Oil City Petroleum,

No. 2. 

Oil City Petroleum,

No. 3. 

Oil City Petroleum,

No. 4. 

Oil City Petroleum,

No. 5.

No. 6. 

Oil City Petroleum,

No. 7. 

Oil City Petroleum,

No. 8. 

Oil City Petroleum,

No. 9. 

Oil City Petroleum,

No. 10. 

Oil City Petroleum,

No. 11 

Oil City Petroleum,

No. 12. 

Oil City Petroleum,

No. 13. 

Oil City Petroleum,

No. 14.

No. 15. 

Twenty-eight, No. 14..

Twenty-eight, No. 13..

Twenty-eight, No. 12..

Twenty-eight, No. 10. .

Twenty-eight, No. 11..

Twenty-eight, No. 8..

Twenty-eight, No. 6..

Twenty-eight, No. 5..

Twenty-eight, No. 2..

Twenty-eight, No. 15.

Twenty-eight, No. 16.

Hanford, No. 2........

Hanford, No. 3. .......

Hanford, No. 4. .......

No. of 

well.

1

2

3

1

3

4

6

7

8

9

10

11

12

13

14

15

 17

18

19

20

21

22

23

24

25

26

27

28

29

30

32

33

34

35

36

37

38

39

40

41

42

49

44

45

46

48

49

50

51

52

54

55

56

57

58

59

00

61

62

Location.

NE. J sec. 12, T. 20 S., R. 14 E . .

... .do.....'............ .......

NE. £ sec. 28, T. 19 S., R. 15 E.

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

SE. £ sec. 28, T. 19 S., R. 15 E.

....Ao..... ...................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do.........................

.....do........................

.....do........................

.....do........................

......do........................

.....do........................

.....do.......................'.

.....do........................

NE. > sec. 28, T. 19 S., R. 15 E.

...v..do...........'.............

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do.. ; .....................

.....do.........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do.........................

.....do.........................

.....do.........................

.....do.........:...............

SE. £ sec. 28, T. 19 S., R. 15 E.

NE. J sec. 28, T. 19 S., R. 15 E.

.....do.........................

.....do.........................

.....do.....................'....

NW. i sec. 28, T. 19 S., R. 15 E. .

.....do.........................

.....do.........................

.....do.........................

SW. £ sec. 28, T. 19 S., R. 15 E . .

NW. i sec. 28, T. 19 S., R. 15 E..

.....do.........................

SW. £ sec. 28, T. 19 S., R. 15 E . .

NE *.. .......................

Elevation 

above 

mean sea 

level.

Feet.

1 407

1,440

1,374

« 1, 450

 1, 458

1,484

1,536

1,538

1,371

1,404

1,372

1, 376

1 Q7Q

1,340

1,361

1,321

1 OOO

1,262

1,211

1 9^3

1 97^

1 31d

1,395

i ^SP;

1 941

1 070

1,420

1,402

1 9V>

1,342

1 049

« 1,380

1,364

1,428

i d^fi

i cnc

1 3ftt

1 370

1 S8";

1,376

1 QR7

1,469 i "idi

a Approximate.
OIL COMPANIES AND OIL WELLS.

Oil companies and oil ivells in Coalinga district Continued.

259

Name or oil company.

Do........................

Do........................

Do........................

Do. .......................

Do........................

Do........................

- Do........................

Do........................

Do........................

Do........................

Do........................

Do. .......................

Do........................

Do........................

Do........................

Standard.....................

Do........................

Do........................

Do........................

- Do........................

S. W. and B. .................

Do........................

Do........................

Do........................

Do. .......................

T.C. .........................

X r&clors

Do........................

Do. .......................

Do........................

Do. .......................

Do........................

Do........................

Do. .......................

Do. .......................

Do........................

Do. .......................

Do. .......................

Do. .......................

Do........................

Do........................

Do. ......................

Do........................

Do. .......................

Do........................

Do. .......................

Do.......................

Do. ......................

Do.......................

Do.......................

Do........................

Twenty-eight. (See Standard.)

Do. ......................

Do. .......................

Do........................

Do........................

Do............. ..........

Do. .......................

Do........................

Do. .......................

Do.......:................

Do. .......................

Do........................

Do.......................

Do........................

Do........................

Name of well.

Fauna, No. 1... .......

Norse No 4

Norse No 1

Traders, Old, No. 4...

Traders, Old, No. 5. ..

Euclid, No.2.........

Traders, Old, No. 3...

Traders, Old, No.2...

No. of 

well.

63

64

65

66

67

68

69

»70

o71

o72

073

074

a 75

o76

o77

o78

(")

H

61

1

2

3

4

5

f>2

d

1

2

3

4

c5

61

1

1

2

4

5

6

7

8

9

a 10

all

12

13

22

23

24

25

26

27

32

33

34

39

40

43

1

a2

al

"2

1

2

4

(i

7

8

9

10

11

12

13

Location.

NW. £ sec. 28, T. 19 S., R. 15 E.

SE. 1 sec. 28, T. 19 S., R. 15 E .

.....do........................

NE. ± sec. 28, T. 19 S., R. 15 E.

SE. £ sec. 28, T. 19 S., R. 15 E .

NE. ±sec. 28, T. 19 S., R. 15 E.

.....do........ ................

.....do........................

.....do........................

.....do........................

NW.isec.28, T. 19 S., 11.15 E.

SW. i sec. 28, T. 19 S., R. 15 E.

SE. 4- sec. 28, T. 19 S., R. 15 E.

NW.'sec. 28, T. 19S.,R.15 E.

SW. £ sec. 28, T. 19 S., R. 15 E.

NW.Jsec.28, T. 19 S., R. 15 E.

NW.£sec.4,T.22S., B. 17 E.

NW. J sec. 34, T. 19 S., R. 15 E .

NE. £ sec. 28, T. 19 S., R. 15 E.

.....do........................

.....do........................

.....do.. ......................

.....do........................

NW. J sec. 30, T. 22 S., R. 18 E.

SE.Jsec. 35, T. 20 S., R. 14 E.

NW. 1 sec. 6, T. 20 S.. R. 15 E.

.....do........................

.....do........................

.....do........................

Sec. 34, T. 18 S., R. 15 E......

SW. Jsec. 2, T. 19 S., R. 35 E.

SW. i sec. 24, T. 20 S., R. 14 E.

.....do........................

.....do..................:.....

.....do........................

.....do........................

.....da... .....................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

NE. } sec. 26, T. 20 S., R. 14 E.

.....do........................

SE. Jsec. 22, T. 19 S., R. 15 E.

SW..} sec. 2, T. 20 S., R. 15 E.

NW.Jsec.l3,T.20S.,R.14E.

NE.Jsec.l3,T.20S.,R.14E.

NW. Jsec. 13, T. 20 S., R. 14 E.

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

Elevation 

above 

mean sea 

level.

Feet.

1, 486

1,385

1,394

1, 407

1,454

.1,061

1 038

1,031

982

958

<*790

d800

d795

d795

833

o"843

824

814

845

818

810

1,143

dl,075

d975

812

811

810

817

808

824

817

837

835

o Drilling. 6 Abandoned. Water well. d Approximate,
260 COALINGA OIL DISTRICT, CALIFORNIA.

Oil companies and oil wells in Coalinga district Continued.

Name of oil company.

Do........................

Do........................

Do........................

Do........................

Do........................

Valley........................

Venus

Do.........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do.........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do........................

Do.r. .....................

Do........................

Waratah ...................... 

Ward.........................

Do........................

Do........................

Do........................

Do........................

Do........................

Westlake-Rommel ............

Westmoreland. (See California Oilfields, Ltd.) 

Whale........................

W.K. ........................

Do........................

Do........................

W. M. & M. (formerly California Diamond, No. 3). 

Do........................

Wright Association ...........

Do........................

Zenith. (See Section One.) 

Zier..... '...............-.......

Do........................

Do........................

Do........................

Do........................

Do.......:................

D'O... .....................

DO..................:.....

Do........................

Do........................

Do........................

Do........................

. Name of well.

King.................

Ellis, No. 1.... .......

No. 4.

No. of 

well.

14

T»

16

17

18

19

1

2

0

4

5- 6

7

8

10

' 11

12

is

14

15

16

17

2

0

4

5

«3

a]

63

1

2

ol

61

2

2

Q

4

5

6

7

9

10

11

12

Location.

NE. i sec. 13,'T. 20 S., R. 14 E.

.....do.......................

.....do.......................

.....do........................

.....do........................

SW. J sec. 32, T. 20 S., R. 15 E .

N W. i sec. 5, T. 22 S., R. 14 E .

NE. J sec. 24, T. 20 S., R. 14 E.

.....do........................

.....do...................'.....

.....do........................

.....do.. ......................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do.........................

.....do... .....................

.....do........................

.....do........................

.....do........................

SW. i sec. 6, T. 21 S., R. 15 E. 

NW.Jsec.12, T. 20 S.,R. 14 E.

.....do........................

.....do....... .................

.....do........................

.....do........................

NE. } sec. 12, T. 21 S., R. 14 E.

NE. J sec. 2, T. 21 S., R. 14 E .

Sec. 4, T. 22 S., R. 14 E.......

NW.Jsec.26, T.20S., R. 14 E.

NE. J sec. 32, T. 19 S., R. 15 E .

NW. Jsec. 2, T. 20 S., R. 15 E.

 NE. J sec. 2, T. 20 S., R. 15 E.

NE. J sec. 31, T. 19 S., R. 15 E .

.....do........................

NW. 1 sec. 26, T. 20 S., R. 14 E .

NW. Jsec.6, T.20S..R. 1.5E.

SW. J sec. 1, T. 20 S., R. 14 E.

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

.....do........................

SE.Jsec. 1.T.20S., R.14E..

.....do........................

.....do........................

.....'do... .....................

Elevation 

above 

mean sea 

level.

Feet.

806

QAO

798

7QO

789

787

7SO

79G

783

77Q

777

775

QOO

934

1,052

920

1 19f»

c960

1,192

1,196

917

1 19**

i;085

QOQ

QOQ

964

970

Q4C

939

QVi

Abandoned. b Drilling. c Approximate.
OIL COMPANIES AND OIL WELLS. 261

The following table, showing the number of wells owned by the 

several companies in each land section in the Coalinga district October 31, 1909, excluding permanently abandoned wells, was compiled from reliable sources in the field by R. W. Pallas and Guy H. 

Salisbury.

Oil companies and number of wells in-Coalinga district October 31, 1909.

Company.

OIL CITY FIELD.

Coast Range Oil Co.. ...............

Home Oil Co.......................

EASTSIDE FIELD.-

Big Shell Petroleum Oil Co. ........

North Limited Oil Co ..............

Imperial Oil Co. (Coalinga) ........

Win. Graham (T. C. Oil Co.) ......

Chas. Wilcox .......................

Kern Trading and Oil Co ...........

California Oilfields, Ltd .....:......

Kern Trading and Oil Co. ..........

Lorene 0 il Co ......................

British Cons. Oil Corp., Ltd ........

California Oilfields, Ltd..... ........

California Oilfields, Ltd ............

Cam well Oil Syndicate. ............

Coalinga Peerless Oil Co ............

Saner Dough Oil Co ..'..............

Caribou Oil Mining Co... ...........

Twenty-two Oil Co. ................

Record Oil Co ......................

Good Luck Oil Co. .................

Montana Oil Co...... ................

Plttsburg Oil Co. ...................

British Cons. Oil Corp., Ltd........ 

Porter Oil Co. .......................

California Oilfields, Ltd ............

Do.............................

Standard Oil Co ....................

Stockholders' Oil Co. ..............

California Oilfields, Ltd ............

Kern Trading and Oil Co. .......... 

Medara Oil Co .....................:

Turner Oil Co. .....................

W. K. Oil Co.......................

Coaliuga Mohawk Oil Co ..... i ..... 

ElectraOilCo......................

Southeastern Limited Oil Co. ...... 

Light Oil Extension Oil Co. ........

WESTSIDE FIELD.

California Oilfields, Ltd ............ 

jEtna Petroleum Oil Co............

Kern Trading and Oil Co. ..........

Confidence Oil Co. .................

Maine State Oil Co. ... . ; ...........

Guthrey OilCo. ...................

Empire Oil Co. ....................

Call Oil Co............. .............

Location.

Sec. 17, T,19'S.,R. 15 E...

Sec.20,T.19S.,B.15E...

.....do....................

Sec. 20, T. 18 S., R. 15 E...

Sec. 29, T.18S..R. 15 E...

Sec, 3d, T. 18 S., R. 15 E...

Sec. 2, T.19S..R.15E....

.....do....................

.....do....................

Sec. 3, T. 19 S., 11.15 E....

Sec. 10, T. 19S.,R. 15 E...

Sec. 11, T. 19S..R. 15 E...

Sec. 12, T. 19S..R. 15 E...

....do....................

Sec. 14, T. 19S..R. ]5E...

Sec. 21, T. 19S.,R. 15E...

Scc.22, T. 19S..R. 1'5E...

.....do....................

.....do....................

.....do....................

.....do....................

.....do....................

.....do....................

.....do....................

.....do....................

Sec. 24, T. 19 S., R. 15 E...

.....do....................

.....do....................

.....do....................

Sec. 26, T. 19S..R. 15 E... 

.....do....................

.....do....................

Sec. 27, T. 19S..R.15E...

Sec. 28, T. 19S..R.15E...

.....do....................

Sec. 34, T. 19S.,R. 15 E,..

Sec. 35, T. 19S.,R. 15 E... 

Sec. 30, T. 19 S., R. 15 E...

Sec. 2, T. 20 S., R.15E....

.....do....................

Sec. 12, T. 20S.,R. 15 E... 

Sec. 0, T. 20 S., R. 15 E....

Sec. 18, T. 208., R. 16 E... 

See. 6, T. 208., R. 16 E....

Sec. 29, T. 19S.,R. 15 E... 

Sec. 30, T. 198., R. 15 E...

Sec. 31, T. 198., R. 15 E...

....do....................

....do.....................

....do....................

....do....................

.....do....................

Sec. 32, T. 19S..R.15E...

.....do....................

Drilling 

wells

1

2

2

1

1

1

2

3

1

1

1

1

2

1

1

3

4

9

3

4

1

2

1

1

Drilling 

wells 

suspended.

1

4

1

1

1

1

1

1

1 1 ....!.

i

3

2

......

2

1

1

Produe^ 

ing 

wells 

suspended.

1

1

1

1

10

1

*. . . .

1

1

2

1

Producing 

wells

2

8

8'

1

3

5

9

2

13

5

10

19

4

1

82

53

5

12

1

2

2

10

4

2

7

2

Number of derricks, 

old 

and 

new.

1

2

J

1

......

2

1

1

2 

1

" i"

Date."

1897

1897

1897

1908

1900

1908

1908

1907

1907

1909

1908

1908

1908

1907

1904

1904

1900

1905

1907

1900

1900

1907

1908

1907

1909

1907

1907

1906

1900 

1909

1900

1903

1903

1899

1900

1908 

1909

1907

1907

1907 

1909

1909 

1909

1903 

1901

IQftO

1901

1901

1907

1901

1905

1909

1906

a Date original company began work drilling for oil. The absenpe of date Indicates that no actual work 

other than assessment work has been done.
262 COALINGA OIL DISTRICT, CALIFORNIA.

Oil companies and number of wells in Coalinga district October 31, 1909 Continued.

Company. 

WESTSIDE FIELD continued.

Zier Oil Co. ........................

Shawmut Oil Co ................... 

Ward Oil Co.. ......................

St. Clair Oil Co. ....................

Pilot Oil Co ........................

D. & 0.). 

Union Oil Co. ....................... 

Kern Trading and Oil Co. ..........

Coalinga Petroleum Co ............. 

Queen Oil Co. ......................

St. Elmo Oil Co. (Home Oil Co.). ...

Inca Oil Co. ........................

Traders' Oil Co ....................

Claremont Oil Co. ..................

Premier Oil Co .....................

Kern Trading and Oil Co. ..........

Traders Oil Co .....................

Netherlands Oil Co .................

Circle Oil Co. ......................

Associated Oil Co .................. 

Claremont Oil Co........... ... ...

Mercantile Grade Oil Co ............

S. W. and B. Oil Co. ...............

New San Francisco Crude Oil Co. . .

Esperama Oil and Gas Co. .........

Arica Oil Co. (Porter & Scrihner) ....

M.,K. andT. Oil Co...............

Peerless Consolidated Oil Co. .......

Nevada Petroleum Co .............. 

American Petroleum Co ............ 

Nevada Petroleum Co .............. 

Kern Trading and Oil Co. .......... 

 Valley Oil Co. ...........'.......... 

Elaine Oil Co .......................

Fifty-seven Oil Co. .................

California Oil and Gas Co. .......... 

Lucile Oil Co. ......................

'Shreeves Oil Co..... ................

Jefferson Oil Co..... ................

Location.

Sec. 32, T. 19 S., R. 15 E..

Sec. 1,T. 20S.,R.14E....

.....do....................

.....do....................

.....do....................

Sec. 2,T. 20S.,R.14E....

.....do....................

Sec. 12,T.20S..R.14E... 

.....do....................

.....do....................

.....do....................

.....do....................

.....do....................

.....do....................

.....do....................

Sec. 13,T.20S.,R.14E... 

.....do....................

Sec. 14, T. 20S..R.14E... 

.....do....................

.....do....................

.....do....................

Sec. 23, T. 20 S.. R.HE...

.....do....................

.....do...........:........

Sec. 24,T.20S.,R.14E...

.....do....................

.....do....................

.....do....................

.....do....................

Sec. 25,T.20S.,R.14E...

.....do....................

.....do....................

.....do....................

.....do....................

.....do....................

.....do....................

Sec. 35,T.20S.,R.14E... 

Sec. S6, T. 20 S., R. 14 E . . . 

Sec. 4,T.20S.,R.15E....

Sec. 6,T.20R.,R.15E....

.....do....................

.....do....................

.....do....................

.....do....................

Sec. 7,T.20S.,R.15E....

.....do....................

.....do....................

Sec. 8,T.20S.,R.15E.... 

.....do....................

.....do....................

Sec. 10,T.20S.,R.15E... 

Sec. 18,T.20S..R.15E...

.....do....................

Sec. 19. T.20S.,R. 15E....

Sec. 19,T.20S.,R.15E...

Sec.20,T.20S.,R.15E... 

Sec. 30,T.20S.,R.15E... 

Sec. 30,T.20S.,R.15E... 

Sec.31,T.20S.,R.15E... 

Sec. 32,T.20S.,R.15E... 

Sec. 12, T. 21S.,R.14E...

Sec. 12,T.21S.,R.15E... 

.....do....................

.....do....................

.....do....................

Sec. 6, T.21S.,R.15E.... 

.....do.....................

.....do.....................

.....do.....................

.....do.....................

Drilling 

wells.

1

1

1

1

1

3 

5

1

1

1

1

2

6

2

....... 

1

1

1

1

1 

1

1

0

1

3

4

1 

6 

3 

1 

1

1 

1

1 

1

1

1

Drilling 

wells 

suspended.

1

1

""2

1

1

1

Producing 

wells 

suspended.

1

1

1

1

2

......

. 3

2

2

' 2

3 

1

3

""2"

0

2

2

2

1

3

1

......

1 

1

Producing 

wells.

4

4

4

12

4 

6

5

2

5

1

3

5

15 

9

4 

2

5

3

7

3

21

13

13

9

8

13 

3

4

1

3

1 

21

3

3

4

6

9

3

4

1

.......

4

 y 

l

l

2

1

Number of derricks, 

old 

and 

new.

1

1

1 

2

1

2

2

1

1

1

...... 

7,

1

1

1

1

""5"

'" i

i

i

i

Date.

1908

1903

1902

1903

1902

1909

1905 

1907

1908

1908

1908

1908

1906

1904

1903 

1908

1905 

1908

1907

1909

1906

1901

1908

1903

1907

1902

1907

1907

1904 

1907

1907

1909

1902

1908

1909

1909

1908 

1907 

1907

1902

1902

1906

1906

1900

1903

1904

1903

1901 

1909

1909

1907 

1908

1909

1909

' i908 

1909

""1909 

1909

"."1909

1909

1909

1907 

1906

1907

1907

1908
OIL COMPANIES AND OIL WELLS. ' 263 

Oil companies and number of ivells in Coalinga district October 31, 1909 Continued.

Company.

WESTSIDE FIELD continued. 

Saner Dough Oil Co.................

De Luxe Oil Co.. ...................

Coalinga Aladdin Oil Co ............

Silver Tip Oil Co.. ..................

Blue Moon Oil Co........... ........

Marion Oil Co......................

KREYENHAGEN FIELD.

Coalinga Hub Oil Co........ ........ 

Coalinga Alpha Oil Co. .............

Azores Oil Co. '. .....................

People's Associated Oil Co. .........

Golden Crest Oil Co.. ............... 

Robertson Oil Co. .....:............

Black Mountain Oil Co. ............. 

Smith & Byrner. ...................

Lake View Oil Co. ..................

Esperanza Land and Oil Co. ........

Blair Oil Co......... ................

Cornelius Oil Co .................... 

El Cerri to Oil Co.. ................. 

Art Anderson et al. ................ 

Uno Oil Co.. ....................... 

Normandie Oil Co .................. 

Etsenhausen Oil Co. ............... 

Best Yet Oil Co....................

Baird Oil Co... ....................

PortolaOilCo......................

NORTHWEST FIELD.

Michigan Oil and Development Co. . Wartham Oil Co....................

SUMMARY OF FIELDS.

Oil City field...... . .................

Eastside field .......................

Westside field ..............:.......

Location.

Sec. G,T.21S.,R.15E..... 

.....do......................

.....do.....................

.....do.....................

.....do.....................

.....do.....................

.....do.....................

.....do.....................

.....do.....................

Sec.l8,T.21S,,E.15E...

Sec. 22,T.21S.,R. 15 E... 

.....do.....................

Sec. 26, T. 21 S..R.15E... 

.....do.....................

Sec.32,T.21S.,R.15E... 

Sec.24,T.21S.,R.15E...

Sec. 12,T.22S.,R.15E... 

Sec.6,T.22S.,R.l6E.... 

.....do.....................

.....do.....................

Sec. 20,T.22S.,R.16E...

Sec. 33,T.22S.,R.16E... 

.....do.....................

Sec. 26, T. 21 S..R.17E...

Sec.30,T.21 S.,R.15E... 

.....do.....................

Sec. 14,T.21 S.,R.14E...

Sec. 14,T.21 S..R. 15 E...

Sec. 4,T.23S.,R.16E.... 

Sec.l4,T.23S.,R.17E... 

Sec. 22,T.23S.,R.17E... 

Sec. 26, T,23S.,R.17E... 

Sec. 30,T.23S.,R. 18E... 

Sec. 27,T.24S.,R.18E...

Sec. 8, T. 198., R. 13 E.... 

Sec. 33,T.20S.,R.13E...

Drill 

ing 

wells

1

1

1

1

1 

1

1

1 

1

1

" i

i

i

""i" 

......

i

i

i

48

80

15

143

Drilling 

wells 

suspended.

1

1

1

1 

1

19

13

3

2

37

Producing 

wells 

suspended.

""'i'

i

2

15 55-

2

72

Producing 

wells

i

i

18

228

304

550

Number of derricks, 

old 

and 

new.

1

l

""'i'

""i"

i

i

" Y 

i

i

i

17

ffl

10

56

Date.

1908 

1909

1909

1909

1909

1909

1909

1909

1909

1909

1909 

1QOQ

1909 

1909

1908

1907 

1909 

1909

1909

1909

1900 

1909

1908

1905 

1907

1903

1908

'i907 

1909

""i909

1909

1909

1909

1907 

1908
264 - COALINGA OIL DISTRICT, CALIFORNIA.

CHEMICAL AND PHYSICAL EXAMINATION OF THE 

PETROLEUMS OF THE COALINGA DISTRICT.

By IRVING C. ALLEN. 

METHODS OF EXAMINATION.

B

Specific gravity. The specific gravity was determined by means of a 

Westphal balance when the quantity of the oil was more than. 9 

cubic centimeters, and by means of a Nicoll picnometer when the 

quantity was less. The Westphal balance is well knb.wn, and no 

description is necessary.

As the Nicoll picnometer is of special though simple construction, 

it is probably less well known, and a brief description is here given. 

Its accuracy with the lighter oils is unquestioned; with the more 

viscous oils some difficulty is encountered in drying the end tubes 

before the final weighings, but with care accurate results to the 

fourth decimal place can be attained. Its. value lies in the ease with 

which it can be made and in the facility with 

which it can be used to determine the specific 

gravity of small quantities of liquids, even as 

little as 0.2 to 0.3 gram.

It is made as follows: A quarter to sixteenth 

inch tube of soft glass, depending on the size 

of the picnometer desired, is drawn out in 

two places with an interval, of about one inch 

into two tubes of capillary diameter. It will 

almost always occur that one of these capillary tubes, will be of slightly greater diameter

than the other, and this capillary (A) is bent through an angle of 

90°. The other or smaller capillary (B) is bent through 180°'back 

along the body of the tube to a point opposite the. first, then again 

through 90° away from the first, as shown in figure 9. The ends of 

A and B are cut off at about equal distances from the body of the 

tube and carefully smoothed off in a flame. A mark is etched on 

the larger tube (A) about midway between the bend and the end. 

The whole is fitted with a fine platinum wire so that it,,can be suspended from the balance arm. A rubber cap is made for tube A.

Now the tube with cap is weighed empty (WJ. The cap is removed 

and the tube is then drawn full of distilled water at a temperature of 

15° C., and the water, with the aid of a bit of filter paper applied to 

B, is drawn accurately to the mark on A. The cap is replaced and 

the tube and contents weighed (W2 ). W2 Wx gives the water 

content of the picnometer at 15° C.

FIGURE 9. Srdall picnometer.
CHEMICAL AND 'PHYSICAL EXAMINATION OF PETROLEUMS. 265

The same procedure with an oil- gives W3 , and W3 Wx gives the

W W oil content at 15°C; and w3' * gives the specific gravity of the

**2~"1

oil at 15° C.

Because the Baume" scale for indicating gravity, in the writer's 

opinion a deplorable system, is. in common use, and for the convenience of those unfamiliar with the specific gravity, the corresponding Baum6 degree is set opposite each specific-gravity degree.

Flash point. The flash point was determined in an Abel or a 

Pensky closed tester, the instrument being carefully screened to 

avoid air currents.

Calorific value. The calorific value was determined in a Berthelot 

combustion bomb (Dinsmore-Atwater model) that is, by burning 

a small quantity of the oil in pure oxygen under a pressure of 30 

atmospheres. This, method is rapid and accurate and is in general 

use.

Sulphur. The sulphupw.as determined by-carefully washing out the 

contents of the bomb, after the combustion, with distilled, water, 

precipitating the sulphuric acid therein with barium chloride in the 

usual way, and calculating the percentage of sulphur.

Fractional distillation. ^For the proximate analysis or fractional 

distillation the form and size of retort recommended by Engler 

(Redwood on Petroleum) was adopted, with the change, however, 

that the side tube turns upward instead of downward at an angle of 

75° with the neck for a length of 4 centimeters, and is then bent 

downward to the original angle of 75°. This, with care in adjusting 

the flame, prevents the bumping over of the retort contents and 

insures a cleaner distillate. First the oil is distilled under normal 

pressure to 200° to 250° C. (Cracking begins at about 330° C.) 

The receiver is then replaced with a fresh one and the distillation 

continued under a vacuum approaching 40 centimeters of mercury 

pressure, the best attainable with the water vacuum pump at hand, 

to a temperature of 330° to 350 °C. that is, until practically all liquid 

is over and only a hard brittle mass of asphaltum remains when 

cooled. From 330° up cracking sometimes occurs, though not 

always, the oils differing markedly in this respect from the Pennsylvania oils, and as a result practically all available "oils" are 

separated from the asphaltum and sediment.

These distillations are united and carefully fractioned in the ordinary Engler retort, taking -fractions every 25° C. according to the 

procedure of Engler. The specific gravity of these fractions is also 

determined. The distillations are done by weight, retorts and all 

receivers being weighed empty and with contents, thus reducing the 

loss to a minimum that is, from 1 per cent to 4 and 5 per cent- with 

the more volatile oils.
266 COALINGA OIL DISTRICT, CALIFORNIA.

This interrupted or intermittent Engler method of distillation 

leaves much to be desired. Mixtures of bodies so closely resembling 

one another in all their properties as those constituting crude 

petroleum are very difficult of separation, and the values given in 

the accompanying tables can not be considered as absolute, but will 

give a very fair idea of the technological constituents of these 

petroleums, and will aid in the more elaborate separations to be 

carried on later.

The method of continuous or uninterrupted distillation now considered to yield the most uniform results will be adopted in the 

bulletins to follow.

RESULTS OF EXAMINATION.

The table that follows shows in detail the results of the examination of these oils. In the columns under the headings "Naphtha," 

"Burning oil," "Lubricating oil," "Asphaltum," and "Paraffin wax," 

the results of the fractional distillation are summarized in order to 

give an idea of the bodies of economic importance to be found in the 

distillates.

The sulphur and water content of these oils is low, comparing most 

favorably with that of other California oils, and the calorific value is 

uniform and good.
CHEMICAL AND PHYSICAL EXAMINATION OF PETBOLEUMS.

Results of chemical and physical examination of the petroleums of the Coalinga district.

No. Laboratory I

1

?

3

4

5

7

8

in

1?

14

16 

17

19

21 

?3

24

25

28

31 

3?

33

35

3fi

3ft

40

41

4?

43

4f»

47

48

50

53

55

56

58

60 

61

fifl

64 

fi5

fifi '68 

7?

Lease.

fields, Ltd.

Do.............

A. O. National 30..

California Oilfields, Ltd. 

Do.............

Callforn ia Monarch . 

California Oi!-

- fields, Ltd. 

W.K..............

Coast Range (Old 

Home).

Commercial Petroleum. 

Do.............

Guthrey 3.

(Maine State).

Kern Trading......

 Do. ............

New San Francisco 

Crude.

Zier................

Do.............

R. H. Herron......

linga.

Coalinga Pacific....

Union.............. 

Do.............

Do.............

Coal inga Petroleum. 

New Home........

Do.............

Coalinga Western . . 

St. Paul Fresno....

WellNo.

1

7

11

5

1

1

1

J27

\28 

13

31

1

8

1

3

7

5

7

11

1 

9

3

8

11

3

1

4

?:

5

6

4

5

1

3

fl

4

1

2 

4

q

4 

1

?,

3 

4

Location.

Sec. 14, T. 19 S., R. 15 E .

Sec. 22, T. 19S..R. 15 E .

.....do...................

.....do...................

.....do...................

.....do...................

.....do...................

}Sec. 28, T. 19S.,R. 15 E..

Sec.27,T.19S.,R.15E...

.....do...................

Sec.26,T.19S.,R.15E... 

Sec.34,T.19S.,R.15E...

Sec.2,T.20S.,R.15E....

Sec.l7,T.19S.,R.15E... 

Sec.20,T.19S.,R.15E...

.....do...................

Sec.28,T.19S.,R.15E...

.....do...................

Sec.31,T.19S.,R.15E... 

.....do....................

.....do...................

....do...................

.....do...................

.....do...................

Sec.6,T.20S.,R.15E....

.....do...................

.....do...................

.....do................... 

.....do...................

Sec.l,T.20S.,R.14E....

.....do...................

.....do...................

.....do...................

Sec.l2,T.20S.,R.14E...

Sec.7,T.20S.,R.15E....

.....do...................

Sec.'13,T.20S.,R.14E... 

.....do...................

.....do...................

Sec.l4,T.20S.,R.14E... 

.....do...................

.....do...................

Sec.23,T.20S.,R.14E... 

.....do...................

Geologic zone.

Top of D......

.....do........

D.............

D ............

Top of D .....

Bottom of D . .

C and D ......

C. ............

D.............

TopofD...... 

B. ............

TopofD......

Chico. ........ 

.....do........

.....do........

C and D ......

.....do........

B. ........:... 

B. ............

TopofB......

B. ............

B. ............

in B. 

B. ............

B. ............

B. ............

B. ............

B.... .........

B. ............

Top of B ......

B. ............

B. ............ 

B. ............

B..... ........

B..... ........ 

B..... ........

Date of 

sampling 

(1907).

Oct. 31

...do.....

...do.....

...do.....

...do.....

...do.....

Oct. 30

...do.....

...do.....

Oct. 31

...do....

...do.....

...do.....

Oct. 10 

...do.....

...do.....

...do.....

...do.....

...do..... 

...do.....

...do.....

...do.....

...do.....

...do.....

...do.....

...do....

...do....

...do..... 

...do....

Oct. 9

...do....

...do....

Oct. 10

Oct. 9

Oct. 9

...do.... 

...do....

...do....

...do.... 

...do....

...do....

...do.... 

...do....

>> £ 

'? . 

£°tic,

12o ^ 

M

0. 9320

0. 9335

0. 9493

0. 9220

0.9291

0. 9215

0. 9393

0. 9243

0. 8718

0.9097

0.9324

0. 9299

0.9305

0.8533 

0. 8519

0.8570

0. 9439

0.9416

0. 9341 

0. 9401

0. 9568

0. 9451

0. 9615

0. 9457

0.9559

0. 9706

0.9672

0.9738 

0.9472

0 9760

0. 9662

0.9771

0.9503

0 9499

n QWI

0.9526

0.9750 

0.9655

0.9715

0.9810 

0.9783

0.9777

0.9820 

0.9833

Baumeat60°F.

°J5.

20.2

20.0

17.6

22.0

20.8

22.1

19.2

21.6

30.7

24.2

20.3 

20.7

20.6

34.2 

34.5

33. 5

18.4

18.8

20.0- 

19.0

16.4

18.2

15.7

18.2

16.5

14.3

14.8

13.8

17 0

13.5

15.0

13.3

17.4

17.5

17 ^

17.1

13.6 

15.0

14.1

12.7 

11 i

11 9

12.6. 

12.4

Flash point.

°F.

92

72

128

63

87

60

121

75

53 

Below

53 

111

66

' 87

Below 

53

53 

Below

53 

115

Below

65 

92

96

+167

150

167 

131

167

167

167 

Above 

167

IDA

167

167

167

1 *vl

155

146

145

Above 

167

167

167 

Above 

167

167

Above 

167

167
268 COALINGA OIL DISTRICT, CALIFORNIA.

Results of'chemical and physical examination of the petroleums of the Coalinga districtContinued.

d

fc

t?

12

5

73

75

77

78

79

80

81

82

83

Lease.

Inca...............

Do.............

Wabash............

Do.............

Do.............

Cal. and N. Y. or

P. M. & D. Co.

Do.............

Fresno and San

Francisco.

Lucile .............

d

fc

1

5

7

8

10

fi

1

4

4

1

,

Location.

Sec.24,T.20S.,R.14E

.....do...................

.....do...................

.....do...................

.....do...................

Sec.l2,T.20S.,R.14E...

.....do...................

Sec.l,T.20S.,R.14E

Sec.6,T.21S.,R.15E....

Geologic zone.

B....... ......

B............

B... ..........

B.............

B..... ........

B and- possibly

top. of D.

B. ............

B... ..........

Lower part of;

upper section of D.

Date of

sampling

(1907).

Oct. 9

...do....

...do....

...do....

...do....

...do....

...do....

Oct. 10

...do....

i?

C8Q

o2

"3 03

02

0. 9581

0.9601

0.9583

0.9585

0.9581

0. 9517

0.9670

0.9729

0.9533

fc

o

s

te .

 03

OJ 

ffl

16.2

15;9-

16. 2

16'. 2

16.2.

17.2

14.8

14.0

17.0

'S

a.

a

1

PR

+167

Above

167

Above

167

Above

167

+ 167

148

Above

167

Above

167
CHEMICAL AND PHYSICAL EXAMINATION OF PETROLEUMS. 269

Results of chemical and physical examination of the petroleums of the Coalinga district 

Continued.

Laboratory No.

1

2 

3 

4 

5 

7 

8

10 

12

14 

16 

17

19 

21

23

24 

25 

28 

31

32 

33

35

36 

39 

40 

41 

42 

43

45 

47 

48 

50 

53

55

56 

58 

60 

61 

62 

64 '65 

66 

68 

72 

73 

75 

77 

78 

79 

80

81 

82

83

Lease.

California Oilfields Ltd......

Do............

Sauer Dough(A.O.) 

A. 0. National 30.

California Oilfields, Ltd.......

Do............

California Monarch. 

California Oilfields, Ltd......

W. K.. ............

Coast Range (Old 

Home) .........

Commercial PetroDo. ...........

Maine State or

California Monarch 

'(Maine State)....

Kern Trading..... 

Mercantile Crude.. 

Do............

York Coalinga..... 

New San Francisco

Zier. ..............

Do............

R. H. Herron ...... 

Pennsylvania CoaSection Seven ..... 

Coalinga Pacific. . .

Do............

Do............

Coalinga Petroleum

Do............

Coalinga Western.. 

St. Paul Fresno . . .

Do............

Do............

Do............

Cal. and N. Y. or 

P. M. &D. Co... 

Do............

Fresno and San

Well No.

i:

<

1

/27 

\28

13 

.31

8 

1

i

i

7 

11

1 

r

t

8 

11 

j

1 

4

2

6 

4 

5 

1

3 

2 

4 

1 

2 

4 

9 

4 

1 

2 

3 

4 

5 

7 

8 

10 

6

1

4

4

1

Calorific value.

10,601

10,584 

10,592 

10,608 

10,656 

10,632

10,596

[ 10,599

10,685 

10,619 

10,576

10,581

10,605

10,657 

10,748 

10,683 

10,577 

10,515

10,563 

10,633

10,502

10,514 

10,493 

10,517 

10, 495 

10,432 

10, 456

10,305

10,523 

10,242 

10,448 

10,365

10,545 

10,539 

10,508 

10,478 

10,422 

10,408 

10,446 

10,402 

10,369 

10,361. 

9,887 

10,356 

10, 491 

10,505 

10,497 

10,480 

10,463

10,548 

10,432

10,415 

10,416

Sulphur.

P.ct. 

0.40

0.40 

0.60 

0.37 

0.39 

0.39

0.53

'0.37

0.35 

0.35 

0.38

0 44

0.40

"o.'os

0.05 

0.51 

0.50

0.47 

0.50

0.48

0.48 

0.55 

0.60 

0.63 

0.71 

0.70

0.70

0.51 

0.72 

0.64 

0.73

0.51 

0.54 

0.54 

0.57 

0.72 

0.72 

0.71 

0.69 

0.70 

0.71 

0.70 

0.76 

0.60 

0.59 

0.59 

0.59 

0.60

0.54 

0.68

0.77 

0.54

Water.

P.ct. 

0.05

0.00 

0.05 

0.00 

0.12 

0.00

0.12

0.00

0.00 

0.00 

0.00

0.12 

0.00

0.00 

0.00 

0.00 

0.00 

0.00

0.00 

0.00

0.10

0.60 

0.09 

0.00 

0.00 

0.00

0.87

. 0.00 

0.00 

Trace. 

0.00

0.00 

0.00 

Trace. 

0.00 

0.00 

0.00 

?race. 

0.11 

0.82 

0.75 

5.36 

0.30 

0.00 

0.00 

0.09 

0.06 

0.32

0.06 

0.12

0.05 

0.74

Fractional distillation (not refined).

75°-100°.

Sp. g.

'6."8652

0.6860

0.7412

0.7719 

0.7522 

0. 7308

0.7441

0.7165

0.7176

0. 7060

P.ct.

"6.'25

0.30 

2.97

0.73

0.67 

1.83 

0.63

0.36

0.95

0.38

0.11

0.32

100"-125°!

Sp.g.

" '07347

0.7406

0.7268

0.7173 

0. 7231

0.7518 

0.7604

0.7742 

0.7768 

0.7688 

0.7536 

0.7143

0.7424

0.7510

0.7463

0.7790

0. 7369

0.7800

P.ct.

" '6.' 88 

0.36 

0.39

0.75

4.22 

0.40 

0.47

0.65 

0.51

10. 64 

5.35 

3.97 

0.45 

0.58

0.16 

0.78

0.14

1.74

0.38

0.47

0.37

,

0.40

125°-150°.

Sp.g.

0.7454

"6.'7755 

0. 7615 

0.7590

0.7682

0.7526 

0.7467 

0.7513

0.7702 

0.7764

0.8075 

0. 8100 

0. 8032 

0.7769 

0.7566

0.7726 

0.7753

0.7632

0.7823

0.8022

0. 7979 

0. 7870

0.7641

0. 7951 

0. 8036

0.7886

P.ct.

0.33

2. 60 

1.23 

1.39 

0.23

1.80

C.16 

1.66 

0.87

0.73 

0.25

18.53 

18.01 

21.72 

0.67 

0.90

0.48 

0.73

0.29

2.45

0.33

0.29

0.27 

0.65

0.48

0.41 

0.12

0.45

150°-175°.

Sp.g.

0.7800 

0. 7994 

0. 7824 

0. 7943 

0. 7908 

0. 7933 

0. 8252

0.7903

0.7814 

0. 7846 

0.7861

0.7869 

0.7963

0.8290 

0.8309 

0.8294 

0. 7960 

0. 7785

0. 7991 

0.7929

0.8025 

0. 7924

0. 7981 

0. 8016 

0.7889

0.8150 

0.8294

0. 8023 

0.7980 

0.8158

0. 8268

0.7853

0. 7879

0. 8087

0. 8046 

0.8036

0.7716

0.7872 

0. 7986

P.ct.

0.95 

5.65 

0.36 

3.67 

2.52 

5.15 

0.76

5.27

5.56 

4.67 

2.14

2.54 

3.08

15.85 

15.51 

16.92 

0.97 

1.68

1.23 

0.95

0.72 

0.74

2.84 

0.59 

0.22 

0.32

1.06 

0.46

1.39 

0.60 

0.86

0.54

0.37

0.28

0.35

0.37 

0.34

0.45

0.17 

0.59
270 COALINGA OIL DISTKICT, CALIFORNIA.

Results of chemical and physical examination of the petroleums of the Coalinga district 

Continued.

6

fc

!f! 

C8 

Hi

1

2 

3

4 

5

7 

8

10 

12

14 

16 

17

19 

21

23 

24 

25 

28 

31

32 

33

35

36 

39 

40 

41 

42 

43

45 

47 

48 

50 

53

55 

56 

58 

60 

61 

62 

64 

65 

66 

68 

72 

73 

75 

77 

78 

79 

80

81 

82

83

Lease.

CaliforniaOilflelds, Ltd........

Do.............

Sauer Dough(A.O.) 

A. O. National 30..

California Oilfields, Ltd........

Do.............

California Monarch. 

California Oilfields, Ltd........

W. K..............

Coast Range (Old

Commercial PetroDo.............

Maine State or

California Monarch 

(Maine State)....

Mercantile Crude. . . 

Do.............

New San Francisco

Do.............

Pennsylvania CoaShawmut..........

Section Seven......

Coalinga Pacific. . . .

Do.............

Do.............

Coalinga Petroleum

Do.............

Do.............

Do.............

Do.............

Cal. and N. Y. or 

P. M. &D.CO... 

Do......'.......

Fresno and San

6

fc

? 

£

1 

7 

11 

5 

1 

1 

1

/27 

\28

13 

31 

1

8 

1

3

7 

5 

7 

11

1 

9

3

8 

11 

3 

1 

4 

2

5 

6 

4 

5 

1

3 

2 

4 

1 

2 

4 

9 

4 

1

2 

3

4

5

7 

8 

10 

6

1 

4

4 

1

Fractional distillation (not refined) Continued.

175°-200°.

Sp.g.

0. 8152 

0. 8269 

0. 8104 

0.8229 

0. 8105 

0. 8202

JO. 8215

0.8053 

0.8067 

0. 8159

0.8079 

0.8305

0. 8469 

0.8537 

0. 8473 

0. 8216 

0.8159

0. 8233 

0.8154

0. 8130

0.8180 

0.8123 

0. 8266 

0.8208 

0. 8225 

0.8314

0. 8646 

0. 8443 

0.8388 

0. 8207

0.8297 

0.8253 

0.8365 

0. 8181 

0.8093 

0. 8292 

0.8352 

0,8326

0.8064

6. 82i8 

0. 8234 

0.8271 

0. 8335 

0.8235

0.8076

0. 8277 

0.8191

P.ct.

3.81 

1.59 

1.75 

5.03 

4.62 

4.57 

1.83

3.99

5.02 

3.92 

3.96

2.54 

3.97

8.56 

9.35 

9.33 

2.60 

2.91

3.05 

2.40

1.37

1.73 

0.47 

3.47 

1.23 

1.14 

0.53

0.41 

1.53 

0.87 

0.36

1.51 

2.33 

2.16 

1.72 

0.47 

1.12 

0.50 

0.96 

Trace. 

0.42

1.05 

1.32 

0.42 

0.46 

0.53

1.23

0.30 

0.89

2000-225°.

Sp.g.

0.8400 

0.8386 

0.8284 

0.8428 

0.8404 

0.8449 

0. 8492

0. 9045

0. 8249 

0. 8302 

0.8398

0.8365 

0. 8495

0.8704 

0. 8747 

0.8727 

0. 8546 

0. 8449

0.8509 

0. 8410

0.8418

0. 8352 

0. 8370 

0. 8462 

0. 8456 

0.8504 

0. 8645

0. 8602 

0.8501 

0. 8612 

0. 8519 

0.8505

0.8503 

0.8488

0. 8553 

0. 8438 

0. 8522 

0.8504 

0.8544 

0.8611 

0. 8166 

0.8412 

0.8553 

0. 8445 

0. 8491 

0.8478 

0. 8444 

0. 8475 

0.8481

0. 8404 

0.8522

0. 8496 

0. 8443

P.ct.

4.38 

5.00 

2.07 

5.45 

6.05 

4.76 

4.48

5.27

4.22 

3.36 

5.30

5.52 

4.54

9.83 

7.79 

9.89 

2.38 

2.97

5.40 

4.47

3.66

2.91 

1.36 

4.74 

2.45 

1.31 

2.65

1.02 

3.00 

0.93 

1.19 

0.40

3.25 

3.35 

3.07 

3.11 

0.99 

1.21 

0.90 

1.23 

0.36 

0.51 

0.54 

0.74 

2.10 

1.45 

2.02 

1.94 

2.33

2.63 

0.90

0.50 

2.33

225°-250°.

Sp.g.

0. 8606 

0. 8630 

0.8536 

0.8650 

0. 8633 

0. 8647 

0. 8679

0.8656

0. 8444 

0. 8527 

0.8682

0.8585 

0: 8678

0.8983 

0. 8987 

0. 9004 

0. 8693 

0.8652

0.8682 

0. 8636

0. 8646

0.8584 

0. 8606 

0. 8648 

0. 8671 

0. 8632 

0. 8730

0. 8731 

0.8689 

0. 8749 

0.8713 

0.8725.

0.8696 

0.8635 

0. 8754 

0. 8669 

0.8688 

0.8589 

0. 8675 

0.8755 

0.8598 

0. 8674 

0. 8786 

0.8752 

0.8685 

0. 8662 

0. 8634 

0. 8635 

0.8634

0.8590 

0. 8614

0. 8691 

0.8683

P.ct.

5.86 

5.58 

4.85 

6.87 

6.77 

5.28 

6.30

8.13

5.24 

5.42

7.74

6.17 

8.96

9.57 

9.21 

12.05 

7.07 

.5.29

5.94 

6.21

6.54

3.90 

3.46 

6.87 

4.15 

3.43 

3.02

3.46 

6.23 

2.15 

4.97 

1.48

6.21 

3.95 

6.68 

5.32 

2.10 

3.88 

3.19 

2.56 

0.72 

2.25 

2.03 

1.08 

4.90 

4.15 

5.06 

2.79 

3.75

4.15 

2.08

2.03 

4.71-

250°-275°.

Sp.g.

0. 8754 

0. 8801 

0. 8726 

0.8808 

0. 8788 

0.8809 

0. 8825

0. 8833

0. 8626 

0. 8703 

0.8824

0. 8756 

0. 8860

0. 9145 

0. 9192 

0. 9178 

0. 8899 

0. 8859

0. 8867 

0.8795

0. 8822

0. 8774 

0. 8759 

0. 8851 

0. 8828 

0. 8811 

0. 8864

0. 8882 

0.8902 

0. 8865 

0. 8866- 

0.8863

0.8868 

0.8844 

0. 8919 

0. 8853 

0.8853 

0.8857 

0. 8852 

0.8884 

0. 8793 

0. 8865 

0. 8877 

 0.8865 

0.8884 

0. 8822 

0.8828 

0. 8821 

0. 8802

0.8811 

0. 8797

0. 8811 

0. 8817

P.ct.

6.29 

7.32 

6.87 

8.58 

7.06 

7.60 

6.98

8.96

5.89 

6.83 

9.64

8.21 

8.58

8.69 

9.00 

7.45 

6.32 

7.10

8.23 

7.16

5.97

6.51 

4.65 

9.24 

6.07 

6.26 

5.50

3. 51' 

7.76 

5.57 

5.03 

4.51

5.80 

7.41 

6.52 

5.89 

5.49 

5.88 

4.98 

4.59 

4.31 

3.55 

3.62 

4.52 

7.23 

5.77 

5.85 

5.54 

5.07

7.40 

5.78

5.58 

4.76

275°-300°.

Sp.g.

0. 8904 

0. 8962 

0.8897 

0. 9002 

0. 8958 

0. 8945 

0. 8990

0. 8971

0.8791 

0.8841 

0. 8978

0. 8918 

0.9002

0. 9223 

0.9288 

0. 9272 

0. 9047 

0. 9119

0. 9026 

0. 8967

0. 8985

0. 8945 

0. 8946 

0. 9018 

0. 8986 

0.8978 

0. 9032

0. 9039 

0. 9046 

0. 9030 

0. 9015 

0. 8965

0.9037 

0.9042 

0. 9084 

0. 9014 

0. 9027 

0. 9031 

0. 9029 

0. 9042 

0. 8985 

0.8089 

0. 9007 

0. 9014 

0. 9052 

0.9007 

0. 8992 

0. 8984 

0. 8973

0.8984 

0. 8981

0. 8968 

0. 8967

P.ct.

8.81 

10.67 

6.30 

11.25 

10.52 

6.35 

9.80

8.50

5.37 

8.28 

8.69

9.15 

10.23

5.22 

4.26 

4.66 

7.89 

7.94

8.66 

9.61

9.64

7.50 

7.65 

8.06 

6.55 

8.71 

6.09

9.15 

7.52 

7.48 

6.40 

5.99

8.07 

8.70 

7.60 

8.39 

6.89 

6.69 

7.95 

7.68 

6.21 

6.32 

5.74 

4.37 

7.12 

6.81 

7.96 

8.16 

6.97

7.12 

7.46

6.38 

6.35
CHEMICAL AND PHYSICAL EXAMINATION OF PETROLEUMS. 271

Results of chemical and physical examination of the petroleums of the Coalinga distnct-~-

Continued.

Laboratory No.

1

2 

3 

4 

5 

7 

8

10 

12

14 

16 

17

19 

21

23 

24 

25 

28 

31

32 

33

35

36 

39 

40 

41 

42 

43

45 

47 

48 

50 

53

55 

56 

58 

60 

61 

62 

64 

65 

66 

68 

72 

73 

75 

77 

78 

79 

80

81 

82

83

Lease.

California Oilflelds, Ltd.......

Do.............

SauerDough(A.O.). 

A. 0. National 30..

Standard...........

California Oilfields, Ltd........

Do.............

California Monarch.

California Oil- fields, Ltd........

W.K. .............

Coast Range (Old 

Home)...........

Coalinga...........

Hanford ...........

Standard...........

Commercial PetroDo..............

Maine State or 

Guthrey 3 .......

California Monarch 

(Maine State)....

Mercantile Crude. . . 

Do.............

York Coalinga......

New San Francisco

Zier. ...............

Do.............

R. H.Herron......

Pennsylvania CoaCoalinga Pacific. . . .

Do.............

Do.............

Coalinga Petroleum

Do.............

Coalinga Western . . 

St. PaulFresno....

Do.............

Wabash............

Do.............

Do.............

Cal. and N. Y. or 

P. M. &D.Co... 

Do.............

Fresno and San 

Francisco ........

1

I

1

7 

11 

5 

1 

1 

1 

/27 

\28

13 

31

1

8 

1

3

7 

5 

7 

11

1 

9

3

8 

11 

3 

1 

4 

2

5 

6 

4 

5 

1

3 

2 

4 

1 

2 

4 

9 

4 

1 

2 

3 

4 

5 

7 

8 

10 

6

1 

4

4 

1

Fractional distillation (not refined) Continued.

300°-325°.

Sp.g.

0.9050 

0.9097 

0.9040 

0.9123 

0.9104 

0.9062 

0.9118

} 0.9120

0.8926 

0.8947 

0.9103

0.9034 

0.9112

0.9323 

0.9384 

0.9334 

0.9186 

0.9164

0.9186 

0.9100

0.9148

0.9092 

0.9117 

0.9175 

0.9126 

0.9133 

0.9160

0.9200 

0.9204 

0.9184 

0.9170 

0.9108

0. 9206 

0.9202 

0.9229 

0. 9182 

0.9188 

0. 9190 

0.9191 

0.9201 

0.9112 

0. 9129 

0.9147 

0.9162 

0. 9219 

0.9168 

0.9149 

0. 9159 

0.9121

0. 9128 

0.9129

0.9115 

0. 9088 .

P.ct.

8.05 

8.69 

8.22 

8.23 

9.22 

6.39 

8.65

8.43

4.97 

7.03 

8.38

9.08 

8.38

2.34 

2.30 

3.20 

10.12 

7.56

10.91 

7.49

'9.42

7.65 

7.35 

10.27 

7.98 

11.00 

7.57

11.29 

9.23 

8.93

7.78 

7.37

7.08 

7.79 

8.35 

8.92 

7.88 

7.84 

6.88 

9.07 

6.47 

10.48 

5.61 

7.08 

9.74 

8.83 

9.71 

. 9.13 

7.45

8.02 

6.83

6.72 

6.45

325°-350°.

Sp.g.

0.9147 

0. 9212 

0.9189 

0.9214 

0.9180 

0.9183 

0.9154

0.9176

0.9063 

0.9083 

0.9157

0.9078 

0.9184

0.9522

0.9419 

0.9303 

0.9298

0.9226 

0.9084

0.9234

0.9233 

0. 9250 

0. 9265 

0.9270 

0.9172 

0.9330

0.9300 

0.9302 

0. 9335 

0. 9336 

0.9254

0.9330 

0.9333 

0.9350 

0.9280 

0.9348 

0. 9294 

0.9329 

0.9335 

0.9261 

0.9285 

0. 9289 

0.9291 

0.9362 

0.9285 

0. 9251 

0.9299 

0. 9264

0.9268 

0.9261

0. 9254 

0. 9229

P.ct.

7.53 

36.06 

9.20 

8.00 

18.66 

7.98 

10.71

19.80

7.67. 

9.34 

15.41

14.89 

17.53

1.34

1.19 

9.08 

9.69

' 13.96 

30.18

20.78

8.59 

7.79 

20.78 

6.97 

26.89 

8.84

20.65 

11.52 

11.14 

9.75 

10.34

10.10 

9.57 

5.93 

10.21 

10.28 

11.49 

7.62 

12.06 

7.59 

9.31 

8.14 

8.90 

7.53 

11.60 

12.10 

7.42 

9.67

8.91 

7.86

8.62

7.78

350°-375°.

Sp.g.

0.9217

0.9282 

0.9303 

0. 9375 

0. 9138 

0.9090

0.9331

0.9141 

0. 9145 

0.9233

0.9160 

0.9421

0. 9386 

0.9371

0.9308 

0.9469

0.9442

0. 9313 

0.9363 

0.9557 

0. 9358 

0. 9469 

0.9433

6.9700 

0.9381 

0.9439 

0. 9386 

0. 9323

0. 9360 

0.9366 

0:9424 

0.9367 

0.9469 

0. 9441 

0.9447 

0. 9486 

0.9367 

0. 9365 

0. 9405 

0.9381 

0. 9449 

0.9390 

0.9384 

0.9394 

0. 9356

0.9352 

0.9395

0.9331 

0. 9349

P.ct.

19.82

11.93 

17.35 

15.78 

15.38 

11.09

9.90

11.84 

11.90 

18.50

15.32 

11.32

(a)

8

17.18 

8.97

5.46 

7.60

16.03

9.08 

15.26 

7.50 

8.41 

4.35 

7.04

5.64 

12.57 

14.67 

11.00 

7.66

11.32 

11.35 

12.34 

12.70 

10.21 

14.66 

6.38 

14.41 

9.85 

19.60 

7.46 

9.39 

7.06 

13.39 

21.08 

10.79 

12.68

12.95 

9.42

14.58 

9.82

375°-400°.

Sp. g.

0.9382

0. 9387

0.9332 

0.9563

0.9230

0.9632

0.9513

0.9442 

0.9483

0.9492

0.9680

0. 9580 

0.9454

0. 9543

0.9593

0.9528 

0.9862 

0.9509 

0. 9844 

0. 9523 

0.9680 

0. 9567 

0. 9649

0.9524 

0.9543

0.9436 

0.9461

0.9558 

0. 9452

P.ct.

3.76

9.61

3.80 

4.94

6.32

5.38

(°) 

a 

(a)

4.97

7.21 

8.59

4.25

2.94

4.66 

5.83

4.06

4.36

2.80 

1.28 

5.75 

1.26 

4.97 

4.18 

2.80 

1.09

4.16 

6.50

11.88 

8.33

6.17 

6.19

See column headed ' ' Paraffin wax.'
272 COALINGA OIL DISTRICT, CALIFORNIA.

Results of chemical and physical examination of the petroleums of the Coalinga district r

ContiMu'e'd.

Laboratory No.

1

?,

3

4

5

7

8

10

12

14

16

17

10

21

97

24

01

38

71

09

33

35

36

30

40

41

49

43

45

47

<1S

en

<v?

55

56

58

firt

61

fi9

64

65

66

68

17,

73

75

77

78

80

81

82

83

Lease.

California Oilfields, 

Ltd.................

Do................

Sauer Dough (A. 0.)...

A. 0. National 30......

California Oilfields, 

Ltd.................

Do................

California Oilfields, 

Ltd.................

W.K... ..............

Coast Range (Old

Do................

Maine State or Guthrey 3 ................

California Monarch

Do................

New San Francisco

Zier...................

Do................

Section Seven.........

Coalinga Pacific.......

Do................

Do................

Coalinga Petroleum ....

Do................

St. Paul Fresno.......

Do................

Wabash...............

Do................

Do................

California and N. Y. or 

P. M. &D.Co......

Do................

Fresno and San FranWeU No.

1

7

11

5

1

1

1

/27

V*> 

13

31

1

8

1

3

7

5

7

11

1

9

3

8

11

3

1

A

?,

5

6

4

5

1

3'

?,

4

1

4

1

4

5

7

8

10

6

1

4

4

1

Naphthao 

(below 

150° C.).

Per cent. 

0.33

. 0.00

0.00

3.73

1.59

1.78

0.23

} 2.85

13.35

106

1.34

2.11

0.76

29.84

25.19

26.32

1.12

1.48

0.64

1.51

0.79

0.00

0.00

5.14

0.00

1.09

0.00

0.00

0.87

 o.oo

0.00

0.00

. 0.00

0.27

0.65

0.00

0.00

0.00

0.00

1.17

0.00

0.00

0.00

0.00

0.00

0.00

0.41

0.12

0.00

0.00

0.00

0.00

0.85

Burning oila (150*- 

300° C.).

Per cent. 

30. 10 . 35. 71

22.20

40.85

37.54

33.71

30.15

40.12

31.30

32.38

37.47

34.13

39.36

57.72

55.12

60.30

27.23

27.89

32.51

30.80

27.90

23.29

17.59

35.22

21.04

21.07

18.11

17.55

27.10

17.46

17.95

12.38

26.23

26.34

26.89

24.43

15.94

19.32

17.52

17.39

11.60

13.33

11.93

10.71

22.75

19.50

21.68

19.23

18.65

22.98

16.22

14.96

19.63

Lubricating oila (300°- 

400° C.).

Per cent. 

39.16

44.75

38.96

33.58

43.66

33. 55

35.39

38.13

24.48

34.59

42.29

44.67

37.23

3.68

2.30

4.39

36.38

31.19

30.33

45.27

46.23

32.53

38.99

38.55

27.61

42.24

23.45

37.58

36.26

34.74

33.19

31.20

28.50

32.77

26.62

36.19

28.37

33.99

23.68

36.82

29.66

40.65

26.18

29.55

27.13

34.91

42.89

31.50

36.30

41.76

32.44

36.09

30.24

Asphaltum 

(above 

400° C.).

Per cent. 

25.30

8.83

31.97

16. 22

8.07

24.62

28.24

10.09

20.31

25.10

12.65

12.92

17.02

 2.68

8.12

 1.89

30.65

36.15

28.45

14.87

17.83

41.07

40.68

14.30

48.75

27.33

55.95

38.71

32.19

43.16

45.16

49. 46

39.35

37.43

42.35

36.13

53.77

42.36

56.78

40. 13

54.64

41.53

54.54

57.42

48.43

40.34

30.33

45.78

41.99

31.62

49.31

46.75

Paraffin 

wax.

Per cent.

3.54

4.47

4.18

Kesidue'.

Per cent. 

3.57

5 CM

5.58

2.54

5.33

3.86

5.27

6.89

4 97

3

09

9 95

1 Q9

1.20

1.62

1.60

1 79

1.42

6.04

4.03

3.59

1 <a

1.84

3.00

1.86

1.75

3.05

2.23

2.55

1 97

5

AQ

4.82

2.38

2.26

1 79

1 19

1.87

2.31

1.82

1 97

0.59

1.05

3.46

2.53

9 34

1 69

2.30

1 in

2 79

1.09

%

Loss.

Per cent. 

1 49

4.77

1.24

3.08

A KK

1.01

2 fi1

7 ^±

3.67

1.60

2

QQ

3 92

3 71

1.34

O 1 Q

1.32

9 fi7

1.87

2

AO

S

CO

3.66

0.98

O

Q-1

3 7Q

0.74

1 V7

0.74

2.24

1 1%

9 no

1 77

1.48

1.10

O ftl

1 97

1 *3

1.83

O QA

9 ^1

O Q7

1 Q9

0 79

1 47

0.64

1 79

9 07

n Q?

1.05

1.28

0.41

1.27

0.70

o These values represent the unrefined fractions.
PLATE XXIII.

88170 Bull. 398 10 18 273
PLATE XXIII.

CHICO (UPPER CRETACEOUS) FOSSILS.

VOLUTODERMA GABBI White.

Figure 1. Natural size. Catalogue No. 20112, U.S.N.M.; copied from Bull. 

U. S. Geol. Survey No. 51, pi. 3, fig. 1. Found at locality 3 

in the Coalinga district; also occurs as far north as Puget Sound 

region...................................................... 60

PERISSOLAX BREVIROSTRIS Gabb.

Figure 2. Natural size. Copied from Whiteaves, Geol. Survey Canada, Mes. 

Foss., vol. 1, pt. 5, pi. 43, fig. 3,1903. Found at locality 4 in the 

Coalinga district; a not uncommon species in the Chico of the 

Pacific coast................................................. 60

TELLINA? OOIDES Gabb.

Figure 3. Exterior of imperfect left valve, showing a little of the original shell 

material, altitude 43 mm., natural size. Catalogue No. 31075, 

U.S.N.M. Found at locality 3 in the Coalinga district, and 

at other Chico localities on the west coast...................... 60

MACTRA ASHBURNERI Gabb.

Figure 4. Exterior of small right valve, longitude 28 mm., X 2. Catalogue

No. 31074, U.S.N.M. Found at locality 3 in the Coalinga 

district; also common at most Chico localities................. 60

MEEKIA BELLA Gabb.

Figure 5. Exterior of cast of right valve, altitude 18 mm., X 2. Catalogue 

No. 31073, U.S.N.M. Locality 3 in Coalinga district; also 

common at other Chico localities on the Pacific coast.......... 60

AVICULA LINGUJEFORMIS Evans and Shumard.

Figure 6. Exterior of cast of small left valve, altitude 14 mm., X 2. Catalogue

No. 31076, U.S.N.M. Locality 11............................. 60

BACULITES CHICOENSIS Trask.

Figure 7. Natural size. Copied from Gabb, Pal. California, vol. 1, pi. 17, figs.

27, 27a, 1864.

7a. Cross section. Idem, figure 27a. 

7b. Septum. Idem, plate 14, figure 28b.

274
U. S. GEOLOGICAL SURVEY , BULLETIN 398 PLATE XXIII

CHICO FOSSILS.
PLATE XXIV.

275
PLATE XXIV.

TEJON (EOCENE) PELECYPODA.

VENERICARDIA PLANICOSTA Lamarck.

Page.

Figure 1. Left valve; longitude 84 mm. Eocene; Little Falls, Wash. Catalogue No. 164973, U.S.N.M. This is the most widespread and 

characteristic Eocene species in the world.

CORBTJLA PARILIS Gabb.

Figure 2. Exterior of right valve restored, longitude 6 mm., X 2. Catalogue

No. 165621, U.S.N.M. Locality 4801.......................... 70

SEPTIFER DICHOTOMUS Gabb.

Figure 3. Exterior of right valve restored, longitude 22 mm., X 2. Catalogue

No. 165623, U.S.N.M. Locality 4801.......................... 70

OSTREA IDRIAENSIS Gabb.

Figure 4. Exterior of right valve, longitude 27 mm.', natural size. Catalogue

No. 165674, U.S.N.M. Locality 4801............".............. 70

Figure 5. Exterior of left valve, longitude 35.5 mm., natural size. Catalogue 

No. 165674, U.S.N.M. Locality 4801. A common species in 

certain'California Eocene localities........................... 70

SPONDYLUS CARLOSENSIS F. M. Anclerson.

Figure 6. Exterior of imperfect specimen, altitude 20 mm., natural size. 

Catalogue No. 165628, U.S.N.M. Locality- 4617. So far unknown outside the Coalinga district........................... 70

Figure 7. Type of species, natural size. Copied from Proc. California Acad. 

Sci., 3d ser., Geology, vol. 2, no. 2, pi. 13, fig. 1.

LED A GABBI Conrad.

Figure 8. Exterior of cast of left valve, longitude 13 mm., X 2. Catalogue 

No. 165662, U.S.N.M. Locality 5014. A common species in 

the Tejon.................................................. 70

TELLINA HORNII Gabb.

Figure 9. Exterior of left valve of slightly imperfect specimen, longitude 

42 mm., natural size. Catalogue No. 165656, U.S.N.M. Locality 4617. A species found at many Tejon localities............ 70

276
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXIV

2 1 

TEJON PELECYPODA.
COALINGA OIL DISTRICT, CALIFORNIA. 277

CRASSATELLITES GRANDIS Gabb.

Page. 

Figure 10. Exterior of imperfect right valve, altitude 50 mm., natural size.

Catalogue No. 165638, U.S.N.M. Locality 4613. A common 

Tejon specie3 .............................................. 70

lOa. Interior of same specimen.

TELLINA JOAQUINENSIS Arnold.

Figure 11. Exterior of left valve, longitude 22 mm., natural size'. Type, catalogue No. 165619, U.S.N.M. Locality 4801.,................. 70

OSTREA AvicuLiFORMis F. M/Anclerson.

Figure 12. Exterior of left valve, longitude, 16^ mm., X 2. Catalogue No.

165627, U.S.N.M. Locality 4801.............................. 70
PLATE XXV.

279
PLATE XXV.

TEJON (EOCENE) PELECYPODA.

PLACUNANOMIA INORNATA Gabb.

Page.

Figure 1. Exterior of upper or convex valve, longitude 20 mm., X 2. Catalogue No. 165632, U.S.N.M. Locality 4801. A common form 

in the supposed brackish-water facies of the Tejon.............. 70

PECTEN PECKHAMI Gabb.

Figure 2. Exterior of gutta-percha cast of right valve, altitude 13 mm., natural 

size. Catalogue No. 165642, U.S.N.M. Locality 4616. Ranges 

from the Eocene to the Miocene............................... 70

2a. Exterior of left valve. Altitude 13.5 mm., natural size.

CARDIUM COOPERI Gabb.

Figure 3. Exterior of slightly broken right valve, altitude 21.5 mm., X 2. Catalogue No. 165637, U.S.N.M. Locality 4617. A species found 

most abundantly in the lower Eocene, but sometimes also in the 

Tejon....................................................... 70

MERETRIX GABBI n. sp.

Figure 4. Exterior of right valve, longitude 29 mm., natural size. Type, Catalogue No. 165640, U.S.N.M. Locality 4801.................... 70

MERETRIX OVALIS Gabb.

Figure 5. Exterior of left valve, longitude 13 mm., X 2. Catalogue No. 165629,

U.S.N.M. Locality 4801. A rather rare species................ 70

ORBITOLITES sp. a.

Figure 6. Top, maximum diameter 7.5 mm., X 3. Catalogue No. 165625, 

U.S.N.M. Locality 4617. A species of foraminifer common in 

the Tejon................................................... 70

PECTEN INTERRADIATUS Gabb.

Figure 7. Exterior of cast of right valve, altitude 9 mm., X 3. Catalogue No. 

.165667, U.S.N.M. Locality 5013. Also known in the shales of 

the Tejon at New Idria ...................................... 70

BARBATIA MORSEI Gabb.

Figure 8. Exterior of slightly imperfect left valve, longitude 16.5 mm., X 2. 

Catalogue No. 165635, U.S.N.M. 'Locality 4801. A common 

species in the Eocene........................................ 70

280
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXV

TEJON PELECYPODA.
COALINGA OIL DISTRICT, CALIFORNIA. 281

MERETRIX IIORNII Gabb.

Page. 

Figure 9. Exterior of right valve, longitude 20 mm., X 2. Catalogue No. 165641,

U.S.N.M. Locality 4617. A common Eocene species......... 70

PLACUNANOMIA INORNATA Gabb.

Figure 10. Exterior of lower or flatvalve, longitude 20 mm., X 2. Catalogue No.

165633, U.S.N.M. Locality 4609.............................. 70

PECTEN INTERRADIATUS Gabb.

Figure 11. Exterior of gutta-percha cast, showing external surface somewhat distorted, altitude 7 mm., X 4. Catalogue No. 165634, U.S.N.M. 

Locality 4616............................................... 70

VENERICARDIA ALTICOSTA Gabb.

Figure 12. Exterior of slightly imperfect specimen, longitude 41 mm., natural 

size. Catalogue No. 165626, U.S.N.M. Locality 4621. Much 

rarer than V. planicosla Lamarck.............................. 70

MERETRIX TJVASANA Conrad.

Figure 13. Exterior of lower or flat valve, longitude 20 mm., X 2. Catalogue

No. 165633, U.S.N.M. Locality 4619. A common Tejon species. 70

CRASSATELLITES GRANDIS Gabb.

Figure 14. Exterior of left valve, altitude 38 mm., natural size. Catalogue

No. 165639, U.S.N.M. Locality 4619...............'............ 70

PLATE XXVI.

88170 Bull. 398 10 19 283
PLATE XXVI.

TEJON (EOCENE) GASTEROPODA AND ECHINODERMATA.

CASSIDULUS CALIFOENICUS F. M. Anderson.

Page.

Figure 1. Top view of imperfect specimen, longitude 21 mm., X 2. Catalogue 

No. 165664, U.S.N.M. Locality 4622. So far known only from 

this locality..........'....................................... 70

la. Bottom of same specimen.

POTAMIDES CARBONICOLA Cooper.

Figure 2. Back of imperfect specimen, longitude 19 mm., X 2. Catalogue No. 

165651, U.S.N.M. Locality 4801. So far known only from the 

type locality................................................ 71

3. Back of another specimen, longitude 16 mm., X 2. Catalogue No. 

165651, U.S.N.M. Same locality as figure 2.

TRITONIUM CALIFORNICTJM Gabb.

Figure 4. Front of young and imperfect specimen, longitude 8 mm., X 4. Catalogue No. 165644, U.S.N.M. Locality 4619. A rather rare species; grows to much larger size than the figured specimen...... 71

SERPULORBIS sp. a.

Figure 5. Top, maximum diameter of specimen 15 mm., X 2. Catalogue No. 

165659, U.S.N.M. Locality 4617. A common form at some

localities of the Tejon......................................... 71

RlMELLA CANALIFERA Gabb.

Figure 6. Front of imperfect specimen, longitude 15 mm., X 2. Catalogue No. 

165646, U.S.N.M. Locality 4618. This species has an expanded lip which is produced upward along the body and penultimate whorls. A common and characteristic Eocene form.... 71

AMAUROPSIS OVIFORMIS? Gabb.

Figure 7. Front of imperfect specimen, altitude 29 mm., natural size. Catalogue No. 165654, U.S.N.M. Locality 4617................... 71

GALERUS EXCENTRICUS Gabb.

Figure 8. Side view, altitude 12 mm., natural size. Catalogue No. 165643, 

U.S.N.M. Locality 4801. A very common and characteristic 

Eocene species.............................................. 71

284
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXVI

20 21 22

TEJON GASTEROPODA AND ECHINODERMATA.
GOALINGA OIL DISTRICT, CALIFORNIA. 285

LUNATIA HORNII Gabb.

Page.

Figure 9. Front view, altitude 13.3 mm., natural size. Catalogue No. 165620, 

U.S.N.M. Locality 4801. Often grows much larger than the 

specimen figured............................................. 71

TRITONIDEA KREYENHAGENI Arnold.

Figure 10. Front of de"collet6 and slightly imperfect specimen, longitude 16 

mm., X 2. Type, catalogue No. 165657, U.S.N.M. Locality 

4801......................................................... 71

TURRITELLA UVASANA Conrad.

Figure 11. Side of a decollete specimen, longitude 31 mm., X 2. Catalogue 

No. 165653, U.S.N.M. Locality 4617. A common and characteristic Eocene species, showing considerable variation as 

regards sculpture............................................ 71

NERITA TRIANGTJLATA Gabb.

Figure 12. Back and part of top, maximum diameter 12 mm., natural size. 

Catalogue No. 165700, U.S.N.M. Locality 4801. A characteristic Eocene species......................................... 71

12a. Top of same specimen.

LUNATIA sp. a.

Figure 13. Front of imperfect specimen, altitude 27 mm., natural size. Catalogue No. 165652, U.S.N.M. Locality 4801.................... 71

TURRITELLA PACHECOENSIS Stanton.

Figure 14. Exterior of imperfect young specimen, longitude 44.5 mm., X 2. 

Catalogue No. 165636, U.S.N.M. Locality 4617. Usually more 

common in the lower Eocene, but also found in the Tejon..... 71

DENTALIUM COOPERI Gabb.

Figure 15. Side, longitude 9 mm., X 2. Catalogue No. 165622, U.S.N.M.

Locality 4619. A common and long-lived species.............. 71

PLEUROTOMA DOMENGINEI Arnold.

Figure 16. Side of imperfect specimen, longitude 11 mm., X 3. Type, catalogue

 No. 165647, U.S.N.M. Locality 4619.......................... 71

LOXOTRP:MA TURRITA Gabb.

Figure 17. Back of imperfect specimen, longitude 20 mm., natural size. Catalogue No. 165649, U.S.N.M. Locality 4801. A peculiar and 

characteristic Tejon species................................... 71

SPIROGLYPHUS? TEJONENSIS Arnold.

Figure 18. Top of coil, maximum diameter 7.5 mm., X 2. Type, catalogue

No. 165658, U.S.N.M. Locality 4617.......................... 71
286 COALINGA OIL DISTRICT, CALIFORNIA.

CYLICHNA COSTATA Gabb.

Page.

Figure 19. Front view of imperfect specimen, longitude 13 mm., X 2. Catalogue No. 165655, U.S.N.M. Locality 4617. A common Eocene 

form very much like some later species of the same genus...... 71

PLEUROTOMA GUIBERSONI Arnold.

Figure 20. Rear view of imperfect specimen, longitude 13.5 mm., X 3. Type,

catalogue No. 165648, U.S.N.M. Locality 4619................ 71

AMAUROPSIS ALVEATA Conrad.

Figure 21. Front view of specimen with slightly broken lip, altitude 43 mm., 

natural size. Catalogue No. 165650, U.S.N.M. Locality 4619. 

An exceedingly widespread and characteristic species in the 

Eocene...................................................... 71

CANCELLARIA IRELANIANA Cooper.

Figure 22. Front view of imperfect specimen, longitude 39 mm., natural size.

Catalogue No. 165645, U.S.N.M. Locality 4619............... 71

PLEUROTOMA FRESNOENSIS Arnold.

Figure 23. Front view of specimen from which the canal is missing, longitude 21 

mm., X 2. Type, catalogue No. 165631, U.S.N.M. Locality 

4619......................................................... 71
PLATE XXVII.

287
PLATE XXVII. 

VAQUEROS (LOWER MIOCENE) FOSSILS: LOWER HORIZON.

OSTEEA TITAN Conrad.

Page.

Figure 1. Exterior of left valve, longitude 90 mm., natural size. Catalogue 

No. 165565, U.S.N.M. Lower Vaqueros formation; locality 

4773. This rather diminutive variety is found abundantly 

below the "reef bed" on Laval grade, 9 miles north of Coalinga. 86

DOSINIA MATHEWSONII Gabb.

Figure 2. Exterior of right valve, altitude 56 mm., natural size. Catalogue No. 

165596, U.S.N.M.. Vaqueros formation; locality 4803. This 

species is believed to be characteristic of the lower and middle 

Miocene.................................................... 86

MYTILUS MATIIEWSONII Gabb var. EXPANSUS Arnold.

Figure 3. Exterior of nearly perfect right valve, longitude 157 mm., natural 

size. Catalogue No. 165661, U.S.N.M. Vaqueros formation; 

locality 4803. This species is believed to be characteristic of the 

Vaqueros; the typical form is usually found in the upper half of 

the Miocene................................................ 86

SEPTIFEE COALINGENSIS Arnold.

Figure 4. Exterior of left valve, longitude 45 mm., natural size. Type, catalogue No. 165580, U.S.N.M. Supposed Vaqueros formation; 

locality 4634................................................ 85

TROPHON (FORRERIA) GABBIANUM F. M. Aiiderson.

Figure 5. Back of imperfect specimen, altitude 44 mm., natural size. Catalogue No. 165572, U.S.N.M. Vaqueros formation; locality 

4860. (SeePl. XXVIII, fig. 5)............................. 86

i ' MULINIA DENSATA Conrad var. MINOR Arnold.

Figure 6. Exterior of slightly imperfect right valve. Type, catalogue No.

165601, U.S.N.M. Vaqueros formation; locality 4777......... 86

288
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXVII

VAQUEROS FOSSILS.
PLATE XXVIII.

289
PLATE XXVIII.

VAQUEROS (LOWER MIOCENE) FOSSILS: LOWER HORIZON.

METIS aff. ALTA Conrad.

Page.

Figure 1. Exteriorof right valve, longitude32 mm., X 2. Catalogue No. 165567, 

U.S.N.M. Vaqueros formation; locality 4627. This lower 

Miocene Metis may be different from the Recent M. alta, but 

the state of preservation of the fossils precludes a definite determination .................................................. 85

2. Left valve of same specimen.

CONUS HAYESI Arnold.

Figure 3. Back of slightly imperfect specimen, longitude 60 mm., natural 

size. Type, catalogue No. 165566, U.S.N.M. Vaqueros formation; locality 4861. ......................................... 86

SCUTELLA MEiiiiiAMi F. M. Anderson.

Figure 4. Top, maximum diameter 21 mm., natural size.- Catalogue No. 

165584, U.S.N.M. Vaqueros formation; locality 4775. This 

little echinoid from which the "button bed" in the Vaqueros 

derives its name is found at many localities in the Coalinga 

district, and is believed to be characteristic of the Vaqueros or 

lower Miocene............................................... 86

TROPHON (FOEREEIA) GABBIANUM F. M. Anderson var. CANCELL ARIOIDES Arnold.

Figure 5. Back of imperfect specimen, longitude 56 mm., natural size. Type, 

catalogue No. 165605, U.S.N.M. Vaqueros formation; locality 

4861. (SeePl. XXVII, fig. 5)............................... 86

PHACOIDES (MILTHA) SANCT^CRUCIS Arnold.

Figure 6. Exterior of nearly perfect right valve, longitude 75 mm., natural 

size. Type, catalogue No. 165569, U.S.N.M. Vaqueros formation; locality 4861.......................................... 86

290
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXVIII

VAQUEROS FOSSILS.
PLATE XXIX.

291
PLATE XXIX.

VAQUEROS (LOWER MIOCENE) FOSSILS: LOWER AND 

UPPER HORIZONS.

ARCA OSMONTI Dall.

Page.

Figure 1. Exterior of left valve, longitude 49 mm., natural size. Catalogue 

No. 165563, U.S.N.M. Vaqueros formation; locality 4859. 

This species is believed to be characteristic of the lower Miocene. 

The specimen figured is from the type locality. Found also 

in Santa Monica Mountains, near Los Angeles.................. 86

la. Umbones of same specimen.

2. Exterior of left valve of a broader specimen, longitude 39 mm., 

natural size. Catalogue No. 165563, U.S.N.M.

TROPHON (FORRERIA) BARTONI Arnold.

Figure 3. Imperfect specimen, altitude 33 mm., natural size. Type, catalogue No. 165571, U.S.N.M. Vaqueros formation; locality 

4861....................................................... 86

PECTEN ANDERSONI Arnold.

Figure 4. Exterior of right valve, longitude 3.7 mm., natural size. Catalogue 

No. 165583, U.S.N.M. Vaqueros formation; locality 4803. 

This species is believed to be characteristic of the Miocene. It 

is found abundantly in certain layers of the " reef beds," where 

it makes up the entire rock for small thicknesses.............. 86

ZlKPILEA DENTATA Gabb.

Figure 5. Exterior of left valve, longitude 73 mm., natural size. Catalogue 

No. 165573, U.S.N.M. Vaqueros' formation; locality 4803. 

This species is believed to be characteristic of the Miocene. ... 86

MACOMA PIERCEI Arnold.

Figure 6. Exterior of left valve of imperfect specimen, longitude 75 mm., 

natural size. Type, catalogue No. 165595, U.S.N.M. Upper 

Vaqueros formation; locality 4631............................ 85

SAXIDOMUS VAQUEROSENSIS Arnold.

Figure 7. Exterior of left valve, longitude 69 mm., natural size. Type, catalogue No. 165570, U.S.N.M. Upper Vaqueros formation; locality 4631.............:....................................... 85

292
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXIX

88170 Bull. 398 10 20

VAQUEROS FOSSILS.
PLATE XXX.

293
PLATE XXX. 

VAQUEROS (LOWER MIOCENE) FOSSILS: UPPER HORIZON.

TUKRITELLA ocoYANA Conrad.

Page.

Figure 1. Back of imperfect specimen, longitude 50 mm., natural size. Catalogue No. 165593, U.S.N.M. Vaqueros formation; locality 4631. 

This is one of the most characteristic fossils of the Vaqueros, 

especially in the San Joaquin Valley and in southern California. 85 

2. Back of two whorls of an exceedingly large specimen, altitude 42 mm., 

natural size. Catalogue No. 165574, U.S.N.M. Upper Vaqueros formation; locality 4631.

VENUS PEETENUIS G.abb.

Figure 3. Exteri r of right valve, longitude 88 mm., natural size. Catalogue 

No. 165597, U.S.N.M. Upper Vaqueros formation; locality 4631. 

This species is believed to be characteristic of the Miocene..... 85

PHACOIDES ACUTILINEATUS Conrad.

Figure 4. Exterior of left valve, altitude 35.5 mm., natural size. Catalogue 

No. 165564, U.S.N.M. Upper Vaqueros formation; locality 

4803. This species ranges from the lower Miocene to the lower 

Pliocene fauna. Formerly called Lutina acutilineata.......... 86

AGASOMA SANTACRUZANA Arnold.

Figure 5. Front of imperfect specimen, consisting of spire and part of body 

whorl, latitude 19 mm., natural size. Catalogue No. 165609,

U.S.N.M. Vaqueros formation; locality 4631. This species is

believed to be characteristic of the Vaqueros.................. 85

CORBICULA DUMBLEI F. M. Anderson.

Figure 6. Exterior of right valve, longitude 28 mm., natural size. Catalogue 

No. 165581, U.S.N.M. Vaqueros formation; locality 4628. 

This species is found abundantly in the Vaqueros oil sand where 

it outcrops in Anticline Canyon southwest of Coalinga......... 85

CHIONE TEMBLORENSIS F. M. Anderson.

Figure 7. Exterior of imperfect and decorticated left valve, longitude 92 mm., 

natural size. Catalogue No. 165612, U.S.N.M. Upper Vaqueros formation; locality 4631. This species, which is characterized by its central beaks and narrow form, is believed to be 

characteristic of th e Vaqueros formation........................ 85

294
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXX

VAQUEROS FOSSILS.
PLATE XXXI.

295
PLATE XXXI. 

VAQUEROS (LOWER MIOCENE) FOSSILS: UPPER HORIZON.

DOSINIA PONDEEOSA Gray.

Page.

Figure 1. Exterior of left valve, altitude 78 mm., natural size. Catalogue 

No. 165660, U.S.N.M. Upper Vaqueros formation; locality 

4631. This species ranges from the lower Miocene to the Recent 

fauna....................................................... 85

CAEDIUM (TKACHYCARDIUM) VAQUEEOSENSIS Arnold.

Figure 2. Exterior of imperfect right valve, altitude 98 mm., natural size. 

Catalogue No. 165598, U.S.N.M. Upper Vaqueros formation; 

locality 4631................................................ '85

CONUS OWENIANUS F. M. Anderson.

Figure 3. Front, altitude 16 mm., natural size. Catalogue No. 165606, U.S.N.M. 

Upper Vaqueros formation; locality 4631. This species, 

which is characterized by spiral striations, is believed to be 

characteristic of the Vaqueros................................ 85

OdNEBEA TOPANGENSIS Arnold.

Figure 4. Back, longitude 25 mm., natural size. Catalogue No. 165608, 

U.S.N.M. Upper Vaqueros formation; locality 4631. This 

species, which is also found in the Santa Monica Mountains, is 

believed to be characteristic of the Vaqueros formation........ 85

CANCELLARIA ANDERSONI Arnold.

Figure 5. Back, longitude 21 mm., X 2. Type, catalogue No. 165607, U.S.N.M.

Upper Vaqueros formation; locality 4631....................... 85

CANCELLARIA VETUSTA Gabb.

Figure 6. Back, longitude 51 mm., natural size. Catalogue No. 165600, 

U.S.N.M. Upper Vaqueros formation; locality 4631. This 

species is believed to be characteristic of the Vaqueros........ 85

PLEUROTOMA (BATHYTOMA) PIEECEI Arnold.

Figure 7. Back of imperfect specimen, altitude 39.5 mm., natural size. Type, 

catalogue No. 165578, U.S.N.M. Upper Vaqueros formation; 

locality 4631........................ ....................... 85

296
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXXI

VAQUEROS FOSSILS.
PLATE XXXII.

297
PLATE XXXII.

SANTA MARGARITA (UPPER MIDDLE MIOCENE) FOSSILS.

TAMIOSOMA GREGARIA Conrad.

Page.

Figure 1. Side, group of individuals, maximum altitude 187 mm., one-half natural size. Catalogue No. 165618, U.S.N.M. Santa Margarita (?) 

formation; locality 4766. This unique form, Avhich is closely 

related to the barnacles, is believed to be characteristic of the 

upper Miocene and is usually found abundantly in the fossiliferous portions of the Santa Margarita (?) formation............. 94

HINNITES GIGANTEUS Gray.

Figure 2. Exterior of right valve, longitude 52 mm., natural size. Catalogue 

No. 165586, U.S.N.M. Santa Margarita (?) formation; locality 

4651. This species ranges from the middle Miocene to the 

Recent fauna. The specimen figured is an immature, fair-sized 

individual................................................... 94

PECTEN ESTRELLANUS Conrad.

Figure 3. Exterior of right valve, altitude 111 mm., one-half natural size. 

Catalogue No. 165616, U.S.N.M. Santa Margarita (?) formation; 

locality 4766. This species is exceedingly common in the Santa 

Margarita (?) and Jacalitos formations, but may extend into the 

Vaqueros.................................................... 94

TROPHON (FORRERIA) CARISAENSIS F. M. Anclerson.

Figure 4. Front, longitude 41 mm., natural size. Type, catalogue No. 165591, 

U.S.N.M. Santa Margarita (?) formation; locality 4766. This 

species is characterized by its moderate size and the spines which 

are locatecl°in the middle of the whorl. It is believed to be 

characteristic of the Santa Margarita (?) formation.............. 94

OSTREA TITAN Conrad.

Figure 5. Exterior of right valve; longitude 174 mm., one-half natural size. 

Catalogue No. 165617, U.S.N.M. Santa Margarita (?) formation; locality 4766............................................. 9-1

298
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXXII

SANTA MARGARITA FOSSILS.
PLATE XXXIII.

299
PLATE XXXIII.

SANTA MARGARITA (UPPER MIDDLE MIOCENE) AND 

JACALITOS (UPPER MIOCENE) FOSSILS.

ASTKODAPSIS WHITNEYI Remond.

Page.

Figure 1. Top of back'of imperfect specimen, maximum diameter 76 mm., natural size. Catalogue No. 165594, U.S.N.M. Santa Margarita (?) 

formation; locality 4766. This species is believed to be characteristic of the Santa Margarita (?) formation in the Coalinga 

district..................................................... 94

OSTREA TITAN Conrad.

Figure 2. Exterior of left valve, altitude 290 mm., one-half natural size. Catalogue No. 165617, U.S.N.M. Santa Margarita (?) formation; locality 4766. This magnificent Oslrea is found abundantly throughout the Miocene, especially in the upper half of the middle Miocene; it sometimes attains a .length of 20 inches and a weight of 

over 20 pounds............................................. 94

PLIOHIPPUS sp. a.

Figure 3.-- Side, longitude49 mm., natural size. Catalogue No. 165665, U.S.N.M. 

Jacalitos formation; NW. I sec. 22, T. 19 S., R. 15 E. The extinct horse, of which this tooth is all that was found, is believed 

to be characteristic of the upper Miocene..................... 98

3a. Crown of same specimen.

THAIS CRISPATUS Chemnitz.

Figure 4. Front of decollet6 and otherwise slightly imperfect specimen, longic tude 44 mm., natural size. Catalogue No. 165532, U.S.N.M. 

Upper Jacalitos formation; locality 4763. This species ranges 

from the upper Miocene to the Recent fauna and is an exceedingly variable species, some specimens being almost smooth, 

others strongly sculptured. The genus Thais has heretofore 

been commonly known as Purpura. ......................... ] 10

300
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXXIII

SANTA MARGARITA AND JACALITOS FOSSILS. 

88170 Bull. 398 10 21
PLATE XXXIY.

301
PLATE XXXIV.

SANTA MARGARITA (UPPER MIDDLE MIOCENE) AND 

JACALITOS (UPPER MIOCENE) FOSSILS.

PECTEN CRASSICAEDO Conrad.

Page.

Figure 1. Exterior of right valve, altitude 165 mm., one-half natural size. Catalogue No. 165615, U.S.N.M. Santa Margarita (?) formation; locality No. 4766. This species is characterized by its large size, fine 

radial striations, and lack of prominent intercalary rib. Ranges 

throughout the Miocene. Is usually more abundant in the middle and upper portions...................................... 94

MACOMA VANVLECKI Arnold.

Figure 2. Exterior of right valve, longitude 54 mm., natural size. Type, catalogue No. 165576, U.S.N.M. Jacalitos formation; locality 4763. 

(See PI. XXXIX, fig. 1)................................... 110

SCHIZODESMA ABSCISSA Gabb.

Figure 3. Exterior of right valve, longitude 100 mm., natural size. Catalogue 

No. 165604, U.S.N.M. Jacalitos formation; locality 4765. This 

species is believed to be characteristic of the upper Miocene.... ]10 

302
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXXIV

SANTA MARGARITA AND JACALITOS FOSSILS.
808

'AXXX
PLATE XXXV.

JACALITOS (UPPER MIOCENE) ECHINODERMATA.

ECHINARACIINIUS GIBBSII

Page.

Figure 1. Top, longitude 81 mm., natural size. Catalogue No. 165611, U.S. N.M. 

Jacalitos formation; locality 4747. This large variety is believed to be characteristic of the lower part of the Jacalitos. .... 110 

2. Bottom of another specimen, longitude 87 mm., natural size. Same

locality. 

304
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXXV

JACALITOS ECHINODERMATA.
PLATE XXXVI.

305
PLATE XXXVI.

JACALITOS (UPPER MIOCENE) FOSSILS.

MONIA MACROSCHISMA Deshayes.

Figure 1. Exterior of left valve, longitude 66 mm., natural size. Catalogue No. 

165602, U.S.N.M. Jacalitos formation; locality 4767. This species 

ranges from upper Miocene to the Recent fauna. Erroneously 

called Placunanomia macroschisma ........................... 110

TELLINA ARAGONIA Dall.

Figure 2. Exterior of right valve, longitude 48 mm., natural size. Catalogue No. 

165577, TJ.S.N.M. Jacalitos formation; locality 4765. This 

species, which was originally described from the Empire formation at Coos Bay, Oregon, is believed to be characteristic of the 

upper Miocene............................................. 110

TROPHON (FORRERIA) PONDEROSUM Gabb.

Figure 3. Back of young specimen, longitude 43 mm., natural size. Catalogue 

No. 165590, U.S.N.M. Etchegoin formation; locality 4642. 

This species is common in the Jacalitos formation and rare in 

the Etchegoin .............................................. 109

CHRYSODOMUS IMPERIALIS Dall.

Figure 4. Back of nearly perfect specimen, longitude 57 mm., natural size. 

Catalogue No. 165582, U.S.N.M. Upper Jacalitos formation; 

locality 4767. This species, which is characterized by its broad

outline and peculiar reflexed varices, is believed to be characteristic of the upper Miocene. It is found in Oregon, in Santa 

Cruz County, Cal., and at one or two localities in the Coalinga 

district .................................................... 110

TROPHON (FORRERIA) PONDEROSUM Gabb.

Figure 5. Side of imperfect specimen, altitude 86 mm., natural size. Catalogue No. 165562, U.S.N.M. Jacalitos formation; locality 4784.. 110 

6. Front of imperfect specimen, altitude 72 mm., natural size. Catalogue No. 165555, U.S.N.M. Jacalitos formation; locality 4765.. 110 

-306
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXXVI

JACAL1TOS FOSSILS.
PLATE XXXVII.

307
PLATE XXXVII. 

JACALITOS (UPPER MIOCENE) FOSSILS.

PANOPEA ESTEELLANA Conrad.

 Page.

Figure 1. Exterior of imperfect right valve, longitude 80 mm., natural size. 

Catalogue No. 165568, U.S.N.M. Jacalitos formation; locality 

4765. ......................:......................:........ 110

CHIONE SECUEIS Shumard.

Figure 2. Exterior of slightly imperfect left valve, longitude 87 mm., natural 

size. Catalogue No. 165599, U.S.N.M. Jacalitos formation; 

locality 4763. This species, which is more inequilateral than 

Chione temblorensis F. M. Anderson, is believed to be characteristic of the upper Miocene................................... 110

MACOMA sp. a.

Figure 3. Exterior of left valve, altitude 29 mm., natural size. Catalogue No.

165588, U.S.N.M. Jacalitos formation; locality 4763........... 110

THAIS KETTLEMANENSJS Arnold.

Figure 4. Back of a decollete and otherwise imperfect specimen, longitude 53 

mm., natural size. Paratype, catalogue No. 165614, U.S.N.M.

Jacalitos formation; .locality 4763. This genus was formerly 

known as Purpura .......................................... 110

° ASTRODAPSIS JACALITOSENSTS Arnold.

Figure 5. Top, longitude 79 mm., natural size. Type, catalogue No. 165610,

U.S.N.M. Jacalitos formation; locality 4745................. 130

MARGARITA JOI-INSONI Arnold.

Figure 6. Front, altitude 6 mm., X 3. Type, catalogue No. 105663, U.S.N.M.

Jacalitos formation; locality 4765............................ 110

308
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXXVII

88170 Bull. 398 10 22 JACALITOS FOSSILS.
PLATE XXXVIII.

309
PLATE XXXVIII.

JACALITOS (UPPER MIOCENE) PELECYPODA.

MACOMA VANVLECKI Arnold.

Tagc.

Figure 1. Exterior of left valve, longitude 54 mm. Type, catalogue No. 165576, 

U.S.N.M. Jacalitos formation; locality 4763. (See PI. XXXIV, 

fig. 2)....................................................... 110

MACOMA JACALITOSANA Arnold.

Figure 2. Exterior of right valve, longitude 70 mm., natural size. Type, catalogue No. 165613, U.S.N.M. Jacalitos formation; locality 4765.. 110

PAPHIA JACALITOSENSIS Arnold.

Figure 3. Exterior of right valve, altitude 57 mm., natural size. Type, catalogue No. 165587, U.S.N.M. Jacalitos formation; locality 4765. 110

THRACIA JACALITOSANA Arnold.

Figure 4. Exterior of cast of left valve, longitude 51 mm., natural size. Type, 

catalogue No. 165579, U.S.N.M. Jacalitos formation; locality 

4763......................................................... no

DOSINIA JACALITOSANA Arnold.

Figure 5. Exterior of right valve, longitude 95 mm., natural size. Type, catalogue No. 165575, U.S.N.M. Jacalitos formation; locality 4763. 110 

310
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXXVIII

JACALITOS PELECYPODA.
PLATE XXXIX.
PLATE XXXIX. 

ETCHEGOIN (UPPER MIOCENE) FOSSILS: LOWER HORIZON.

OSTREA ATWOODI Gabb.

Page.

Figure 1. Exterior of left valve, longitude 59 mm., natural size. Catalogue No. 

165531, U.S.N.M. Lower Etchegoin formation; locality 4678. 

This species is believed to be characteristic of the upper Jacalitos and lower Etchegoin formations, or middle portion of upper 

Miocene.................................................... 126

2. Exterior of right valve, longitude 48 mm. Same locality.

MULINTA DENSATA Conrad.

Figure 3. Exterior of right valve, longitude 65 mm., natural size. Catalogue 

No. 165559, U.S.N.M. Lower Etchegoin formation; locality 

4682. This species ranges throughout the Miocene, but is more 

commonly found in the upper Miocene. It is sometimes known 

as Pseudocardium gabbi Remond ............................. 125

4. Interior of left valve, longitude 75 mm., natural size. Catalogue No.

165559, U.S.N.M. Lower Etchegoin formation; locality 4679... 125

DIPLODONTA PARILIS Conrad.

Figure 5. Exterior of right valve, longitude 31 mm., natural size. Catalogue 

No. 165484, U.S.N.M. Lower Etchegoin formation; locality 

4806. This species is'believed to be characteristic of the upper 

Miocene. It is also known from Oregon ...................... 131

DIPLODONTA HARFORDI F. M. Anderson.

Figure 6. Exterior of right valve, longitude 28 mm., natural size. Catalogue 

No. 165485, U.S.N.M. Lower Etchegoin formation; locality 

4806. This species is believed to be characteristic of the upper 

Miocene and has so far been recognized only in the Coalinga 

district............................................:........ 131

CARDIUM MEEKIANUM Gabb.

Figure 7. Exterior of decorticated left valve, altitude 70 mm., natural size. 

Catalogue No. 165542, U.S.N.M. Lower Etchegoin formation; 

locality 4806. The external surface of this fossil is almost always 

gone. It is an abundant species in one or two of the layers of 

the lower Etchegoin, but has a range elsewhere from the upper 

Miocene to the lower Pliocene............................... 131

312
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XXXIX

ETCHEGOIN FOSSILS.
PLATE XL.

3.13
PLATE XL.

ETCHEGOIN (UPPER MIOCENE) FOSSILS: LOWER

HORIZON.

ARC A TRILINEATA Conrad.

Page.

Figure 1. Exterior of left valve, longitude 61 mm., natural size. Catalogue 

No. 165534, U.S.N.M. Lower Etchegoin formation; locality 

4665. This species, which is variable both in outline and 

number and sculpture of ribs, ranges from the upper Miocene 

to the Pliocene. It is abundant in the upper Miocene and 

later marine faunas in the Coalinga district.................... 125

la. Umbones of same specimen.

THAIS ETCIIEGOINENSIS Arnold.

Figure 2. Front of slightly decollete" specimen, longitude 38 mm., natural 

size. Type, catalogue No. 165533, U.S.N.M. Lower Etchegoin formation; locality No. 4697. The genus Thais was formerly 

known as Purpura. ........................................... 130

PAPHIA TENERRIMA Carpenter.

Figure 3. Exterior of left valve, longitude 83 mm., natural size. Catalogue 

No. 165544, U.S.N.M. Middle Etchegoin formation; locality 

4664. This Species is abundant in the middle Etchegoin beds 

on White Creek and Anticline Ridge. It ranges from the upper 

Miocene to the Recent fauna.................................. 126

PANOPEA GENEROSA Gould.

Figure 4. Exterior of right valve, longitude 104 mm., natural size. Catalogue 

No. 165556, U.S.N.M. Upper Etchegoin formation; locality 

4658. This species ranges from the lower Miocene to the Recent 

fauna....................................................... 126

314 .
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XL

ETCHEGOIN FOSSILS.
PLATE XLI.

315
PLATE XLI.

ETCHEGOIN (UPPER MIOCENE) FOSSILS: LOWER

HORIZON.

ECHINARACHNITIS GiBBSii Remond var. ASHLEYI Arnold.

Page.

Figure 1. Top, longitude 60 mm., natural size. Catalogue No. 165548, U.S.N.M. 

Upper Jacalitos formation; locality 4767. An abundant form 

at this locality; also abundant in the Santa Maria district...... 110

ECHINARACHNIUS GIBBSII Remond.

Figure 2. Top, longitude 54 mm. Catalogue No. 165547, U.S.N.M. Locality 

4661. A relatively narrower specimen than that shown in 

Plate XLII, figure 7.....'................................... 125

GLYCYMERIS COALINGENSIS Arnold.

Figure 3. Exterior of decorticated fight valve, longitude 42 mm., natural size. 

Type, catalogue No. 165526, U.S.N.M. Lower Etchegoin formation; locality 4806. This genus was formerly known as Pectunculus. ........................................................ 131

MACTRA ALBARIA Conrad.

Figure 4. Exterior of an imperfect right valve from which a portion of the 

anterior extremity has been eroded; altitude 63 mm., natural

size. Catalogue No. 165552, U.S.N.M. Lower Etchegoin

formation; locality 4665. This species, which is believed to 

be characteristic of the upper Miocene, is found abundantly 

in Oregon, but only a few specimens were obtained in the 

Coalinga district.............................................. 125

MYTILUS (MYTILOCONCHA) COALINGENSIS Arnold.

Figure 5. Exterior of imperfect left valve, altitude 100 mm., natural size. 

Paratype, catalogue No. 165557, U.S.N.M. Lower Etchegoin 

formation; locality 4658....................................... 125

316
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XLI

ETCHEGOIN FOSSILS.

88170 Bull. 398 10 23
PLATE XLII.

3.1.7
PLATE XLII.

ETCHEGOIN (UPPER MIOCENE) FOSSILS: LOWER

HORIZON.

MACOMA SECT A Conrad.

 -'Page.

Figure 1. Exterior of left valve, longitude 75 mm., natural size. Catalogue 

No. 165592, U.S.N.M. Etchegoin formation; locality 4806. 

This species ranges from the upper Miocene to the Recent fauna. 131

NEVERITA RECLUZIANA Petit.

Figure 2. Front view of decorticated and slightly imperfect specimen, altitude 

36 mm., natural size. Catalogue No. 165486, U.S.N.M. Upper 

Etchegoin formation; locality 4710. This species ranges 

from the upper Miocene to the Recent fauna................... 130

GLYCYMEEIS SEPTENTEIONALIS Middendorf.

Figure 3. Exterior of left valve, longitude 24 mm. Catalogue No. 165527, 

U.S.N.M. Lower part of the Etchegoin formation; locality 

4806. This genus was formerly known as Pectunculus.......... 131

3a. Interior view of same specimen.

MODIOLUS RECTUS Conrad.

Figure 4. Exterior of right valve from which the outer surface of the shell has 

been removed, longitude 86 mm., natural size. Catalogue No. 

165535, U.S.N.M. Lower Etchegoin formation; locality 4698. 

This species ranges from the upper Miocene to the Recent and is 

characterized by its angular posterior outline.................. 128

NEVERITA RECLUZIANA Petit var. ALTA Dall.

Figure 5. Front of slightly imperfect specimen, altitude 28 mm., natural size. 

Catalogue No. 165489, U.S.N.M. Upper Etchegoin formation; locality 4709. This variety ranges from the upper Miocene 

to the Recent fauna.......................................... 130

5a. Back of same specimen.

MACOMA NASUTA Conrad.

Figure 6. Exterior of slightly imperfect right valve, longitude 70 mm., natural 

size. Catalogue No. 165514, U.S.N.M. Lower part of the 

Etchegoin formation; locality 4756. This species ranges from 

the lower Miocene to the Recent fauna......................... 131

ECHINARACHNIUS GiBBSii Remond.

Figure 7. Top, longitude 61 mm., natural size. Catalogue No. 165547, U.S.N.M. 

Lower Etchegoin formation; locality 4661. This figure illustrates a typical undistorted specimen. The specimens found 

in this district are usually more or less distorted. The species 

ranges through the Jacalitos and Etchegoin formations. (See 

PI. XLI,fig.2)............................................. 125

318
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XLII

ETCHEGOIN FOSSILS.
PLATE XLIII.

319
PLATE XLIII.

JACALITOS (EARLY UPPER MIOCENE) AND ETCHEGOIN 

(UPPER MIOCENE) FOSSILS: LOWER HORIZON.

THAIS KETTLEMANENSIS Arnold.

Page.

Figure 1. Front of decorticated and slightly imperfect specimen, altitude 82 

mm., natural size. Type, catalogue No. 165585, U.S.N.M. 

Jacalitos formation; locality 4763............................. 110

la. Back of same specimen.

CRYPTOMYA QUADRAT A Arnold.

Figure 2. Exterior of right valve, longitude 35 mm., natural size. Type, catalogue No. 165525, U.S.N.M. Lower Etchegoin formation; 

locality 4665................................................ 125

2a. Exterior of left valve of same specimen.

MULINIA DEN SAT A Conrad.

Figure 3. Front of both valves, altitude 50 mm., natural size. Catalogue No. 

165554, U.S.N.M. Lower Etchegoin formation; locality 4754. 

This species is usually confined to the upper Miocene, although 

it is known to extend down into the Vaqueros. This species is

sometimes listed as Pseudocardium gabbi Remond............. 131

SAXIDOMUS NUTTALLI Conrad.

Figure 4. Exterior of right valve 105 mm., two-thirds natural size. Catalogue 

No. 165529, U.S.N.M. Upper part of Jacalitos formation; 

locality 4656. This species ranges from the upper Miocene to 

the Recent fauna............................................ 126

320
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XL1II

JACALITOS AND ETCHEGOIN FOSSILS.
PLATE XLIV.

321
PLATE XLIV.

ETCHEGOIN (UPPER MIOCENE) FOSSILS: LOWER

HORIZON.

LUNATIA LEWISII Gould.

Page. 

Figure 1. Front of slightly imperfect internal cast which, however, shows the

general outline of the shell; altitude 90 mm., natural size. 

Catalogue No. 165541, U.S.N.M. Upper Etchegoin formation; 

locality 4665. This species ranges from the upper Miocene to the 

Recent fauna................................................. 127

PLEUEOTOMA COALINGENSIS Arnold.

Figure 2. Front, longitude 20mm., X 2. Type, catalogue No. 165509, U.S.N.M.

Upper Etchegoin formation; locality 4806...................... 133

TUREITELLA VANVLECKI Arnold.

Figure 3. Back of decollete and otherwise somewhat imperfect specimen; 

longitude 57 mm., natural size. Type, catalogue No. 165496, 

U.S.N.M. Middle Etchegoin formation; locality 4658.......... 127

TROPHON (FORRERIA) COALINGENSE Arnold.

Figure 4. Back of imperfect specimen, longitude 65 mm., natural size. Type 

catalogue No. 165540, U.S.N.M. Upper Etchegoin formation; 

locality 4857................................................ 133

CRYPTOMYA OVALIS Conrad.

Figure 5. Exterior of left valve, longitude 37 mm., natural size. Catalogue 

No. 165589, U.S.N.M. Etchegoin formation; locality 4758. 

This specimen appears to be intermediate between the typical 

Cryptomya ovalis Conrad and Cryptomya quadrata Arnold........ 131

MYTILUS (MYTILOCONCHA) COALINGENSIS Arnold.

Figure 6. Exterior of umbonal region of a moderate-sized right valve, longitude 105 mm., natural size. Type, catalogue No. 165551, 

U.S.N.M. Lower Etchegoin formation; locality 4656.......... 125

322
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XLIV

ETCHEGOIN FOSSILS.
PLATE XLV.

323
PLATE XLV.

ETCHEGOIN (UPPER MIOCENE) FOSSILS.

PECTEN (PATTNOPECTEN) OWENI Arnold.

Page. 

Figure 1. Exterior of right valve, anterior ear slightly broken, altitude 85 mm.,

slightly reduced. Type; Coll. Univ. California. Foxin's 

ranch, Santa Barbara County. A characteristic species in the 

upper Miocene.

CREPIDULA PRINCEPS Conrad.

Figure 2. View of interior; longitude 106 mm., slightly reduced. Catalogue 

No. 165315, U.S.N.M. Packard's Hill, Santa Barbara. Found 

throughout the Miocene and Pliocene in California.

ASTRANGIA COALINGENSIS Vaughan. 

Figure 3. View of top of group of specimens, maximum altitude 20 mm., X 3.

Type, catalogue No. 165666, U.S.N.M. Upper Etchegoin 

formation; locality 4710. This species is believed to be characteristic of the upper Miocene................................. 128

324
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XLV

88170 Bull. 398 10 24 ETCHEGOIN FOSSILS.
PLATE XLVI.

325
PLATE XLVI.

ETCHEGOIN UPPER MIOCENE) FOSSILS: UPPER HORIZON.

SIGARETTJS SCOPULOSUS Conrad.

Page. 

Figure 1. Top, maximum diameter 36 mm., natural size. Catalogue No.

165524, U.S.N.M. Upper Etchegoin formation; locality 4662. 

This species ranges from the Oligocene to the lower Pliocene.... 127

PLACUNANOMIA CALIFORNICA Arnold.

Figure 2. Exterior of right valve, altitude 66 mm., natural size. Type, catalogue No. 165546, U.S.N.M. Upper Etchegoin formation; 

locality 4715.................................................. 129

2a. Interior of same specimen.

3. Interior of left valve, paratype, altitude 67 mm., natural size.

OSTREA VESPERTINA Conrad.

Figure 4. Exterior of left valve, longitude 57 mm., natural size. Catalogue No.

165536, U.S.N.M. 'Upper Etchegoin formation; locality 4715.. 129 

5. Right valve, longitude 67 mm. Same locality.

326
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XLVI

ETCHEGOIN FOSSILS.
PLATE XLVII.

327
PLATE XLVIL

ETCHEGOIN (UPPER MIOCENE) FOSSILS, UPPER HORIZON, 

AND TULARE (FRESH-WATER PLIOCENE) FOSSILS.

ASTYRIS RICHTHOFENI Gabb.

Page.

Figure 1. Front of a rather poorly preserved specimen, altitude 11 mm., X 2. 

Catalogue No. 165510, U.S.N.M. Upper Etchegoin formation; 

locality 4806. This species ranges from the upper Miocene to 

the Pliocene................................................ 132

TllOPHON (BOREOTROPHON) STUARTI Smith.

Figure 2. Back of body whorl and portion of penultimate whorl, longitude 25 

mm., natural size. Catalogue No. 165492, U.S.N.M. Upper 

Etchegoin formation; locality 4712. This species ranges from 

the upper Miocene to the Recent and is a boreal type......... 130

SEMELE RUBROPICTA Dall.

Figure 3. Slightly imperfect right valve, longitude 31 mm., natural size. Catalogue No. 165517, U.S.N.M. Upper Etchegoin formation; 

locality 4758. This species ranges from the upper Miocene to 

the Recent fauna............................................ 132

MACTRA COALINGENSIS Arnold.

Figure 4. Exterior of imperfect left valve, altitude 52 mm., natural size. 

Type, Catalogue No. 165513, U.S.N.M. 'Upper Etchegoin formation; locality 4806......................................... 131

MACOMA NASUTA Conrad.

Figure 5. Imperfect left valve, longitude 69 mm., natural size. Catalogue No.

165515, U.S.N.M. Upper-Etchegoin formation; locality 4758.. 131

BULBOUS GROWTH ON FISH SKELETON.

f Figure 6. Top, longitude 52 mm., natural size. Catalogue No. 165495, U.S.N.M.

: Upper Etchegoin formation; locality 4740..................... 153

6a. Bottom of same specimen.

6b. Side of same specimen.

FISH SPINE.

Figure 7. Side, longitude 49 mm., naturalsize. Catalogue No. 165493, U.S.N.M.

Tulare formation; locality 4740............................... 153

- 7a. Base of same specimen.

328
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XLVII

ETCHEGOIN AND TULARE FOSSILS.
COALINGA OIL DISTBICT, CALIFORNIA. 329 

BULBOUS GEOWTH ON FISH SKELETON.

Page. 

Figures. Grooved base, longitude 40 mm., natural size. Catalogue No.

165494, U.S.N.M. Tulare formation; locality 4.731............ 153

CAECHAEODON AENOLDI Jordan.

Figure 9. Back, longitude 50 mm., natural size. Catalogue No. 165488, U.S.N.M. 

Upper Etchegoin formation; locality 4709. This extinct species of shark is believed to be characteristic of the upper Miocene 

and lower Pliocene........................................... 130

PLATE XLVIII.

331
PLATE XLVIII. 

ETCHEGOIN (UPPER MIOCENE) FOSSILS: UPPER HORIZON.

PECTEN COALINGAENSIS Arnold.

Page.

Figure 1. Exteriorof right valve, longitude 58 mm., natural size. CatalogueNo. 

165530, TJ.S.N.M. Upper part of Etchegoin formation; locality 

4710. This species is believed to be characteristic of the upper 

part of the Etchegoin formation at the top of the Miocene...... 132

2. Left valve, longitude 55 mm., natural size. Same locality.

PECTEN (PLAGIOCTENIUM) DESERTI Conrad.

Figure 3. Exteriorof right valve, altitude 43 rnm., natural size. CatalogueNo.

165518, U.S.N.M. Upper Etchegoin formation; locality 4715.. 132 

4. Exterior of left valve, longitude 37 mm., naturalsize. Samelocality.

CHAMA PELLUCIDA Sowerby.

Figure 5. Exteriorof left valve, altitude 42 mm., naturalsize. CatalogueNo. 

165482 U.S.N.M. Upper Etchegoin formation; locality 4710. 

This species ranges from the upper Miocene to Recent, but is 

found in the Coalinga district only in the upper Etchegoin..... 131 

6. Exterior of right valve; altitude 24 mm., natural size. CatalogueNo. 

165482, U.S.N.M. Locality same as last.

TRANSENNELLA CALIFORNICA Arnold.

Figure 7. Exterior of right valve, longitude 5.5 mm., X 5. Type, catalogue No.

165553, U.S.N.M. Upper Etchegoin formation; locality 4715.. 132 

7a. Interior of same specimen.

PAPHIA STALEYI? Gabb.

Figure' 8. Right valve of young specimen, longitude 8.5 mm., X 3. Catalogue 

No. 165516, U.S.N.M. Upper Etchegoin formation; locality 

4715. This species is believed to be characteristic of the upper 

Miocene and Pliocene. Formerly called Tapes staleyi. ........ 132

CHRYSODOMUS PORTOLAENSIS Arnold.

Figure 9. Front, longitude 64 mm., natural size. Type, catalogue No. 165473, 

U.S.N.M. Etchegoin formation; locality 4665. This species 

is believed to be characteristic of the upper Miocene, and is 

found abundantly in the lower Purisima formation near Portola 

in San Mateo County and in several localities farther south .... 126

CANCELLARIA TRITONIDEA Gabb.

Figure 10. Front, longitude 78 mm., natural size. Catalogue No. 165561, 

U.S.N.M. Upper San Pedro formation, San Pedro, California. 

This species is believed to range from the upper Miocene to the 

Pleistocene. The specimen figured is from the type locality. 

332
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XLVIII

ETCHEGOIN FOSSILS.
PLATE XLIX.

333 

88170 Bull. 398 10 25
PLATE XLIX.

ETCHEGOIN (UPPER MIOCENE) FOSSILS: UPPER HORIZON.

PECTEN (CHLAMYS) WATTSI Arnold.

Page.

Figure 1. Exterior of right valve, altitude 61 mm., natural size. Catalogue 

No. 165550, U.S.N.M. Upper Etchegoin formation; locality 

4712. This specimen is also from the type locality. The species 

ranges from the upper Miocene to the lower Pliocene and is found 

in the Coalinga district onlyin the upper Etchegoin........... ' 132

2. Exterior of left valve, altitude 76 mm., natural size. Same locality.

PECTEN NUTTERI Arnold.

Figure 3. Exterior of right valve, altitude 67 mm., natural size. Catalogue 

No. 165549, U.S.N.M. Upper Etchegoin formation; locality 

4712. This specimen is from the type locality of the species, 

where it is moderately abundant. It is believed to be characteristic of the upper Miocene and possibly lower Pliocene........ 132

4. Exterior of left valve, altitude 63 mm. Same locality.

TEREBRATALIA SMITHI Arnold.

Figure 5. Exterior of dorsal valve showing beak of ventral valve, altitude of 

former 22 mm., natural size. Catalogue No. 165512, U.S.N.M. 

Upper Etchegoin formation; locality 4758. This brachiopod is 

very abundant in the Pecten coalingaensis horizon.............. 131

5a. Ventral valve of same specimen. Longitude 27.5 mm., natural size.

CALLIOSTOMA KERRI Arnold.

Figure 6. Front of slightly distorted specimen, altitude 18.5 mm., natural 

size. Type, catalogue No. 165500, U.S.N.M. Upper Etchegoin formation; locality 4758................................... 132

CALLIOSTOMA COALINGENSIS Arnold.

Figure 7. Front view of slightly distorted specimen, altitude 21 mm., natural 

size. Type, catalogue No. 165499, U.S.N.M. Upper Etchegoin formation; locality 4758................................... 132

NASSA CALIFORNIANA Conrad.

Figure 8. Front of a slightly imperfect young and unusually nodose specimen, 

altitude 13.5 mm., X 2. Catalogue No. 165508, U.S.N.M. 

Upper Etchegoin formation; locality 4806. This species ranges 

from the upper Miocene to the Pleistocene and may possibly 

have living representatives. This nodose form is apparently 

characteristic of the upper Miocene........................... 133

334
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE XLIX

3 10

ETCHEGOIN FOSSILS
COALINGA OIL DISTRICT, CALIFORNIA. 335

NASSA CALIFORNIANA Conrad var. COALINGENSIS Arnold.

Page. 

Figure 9. Front, altitude 32 mm./ natural size. Type, catalogue No. 165511,

U.S.N.M. Upper Etchegoin formation; locality 4758.......... 133

CLIBIOPHORA PUNCTATA Conrad.

Figure 10. Exterior of left valve, longitude 28 mm., natural size. Catalogue 

No. 165497, U.S.N.M. Upper Etchegoin formation; locality 

4806. This species, in which the right valve is somewhat flatter 

than the left, ranges from the upper Miocene to Recent fauna.... 131

PLATE L.

337
PLATE L.

ETCHEGOIN (UPPER MIOCENE) ECHINODERMATA: UPPER

HORIZON.

SCUTELLA PERRINI Weaver.

Figure 1. Top, longitude 46 mm., natural size. Catalogue No. 165560, U.S.N.M.

Upper Etchegoin formation; locality 4712. This species is 

'-"r '- believed-to be characteristic of the uppermost Miocene and

possibly lower Pliocene...................................... 128

2. Bottom, longitude 45 mm., natural size. Catalogue No. 165560,

U.S.N.M. Same locality.

ASTRODAPSIS? sp. a.

Figures. Top, longitude 28-mm., X 2. Catalogue- No. 165701, U.S.N.M. 

Upper Etchegoin formation; locality 4712. A common form at 

this horizon.................................................. 128

3a. Bottom of same specimen.

-_ . _ . ECHINARACHNIUS GiBBSii Remond.

Figure 4. Top of young specimen, longitude 33 mm., X 2. Catalogue No.

165537. U.S.N.M. Upper Etchegoin formation; locality 4710. 

This is the most abundant sand dollar in the district and is 

found throughout the Jacalitos and Etchegoin formations....... 128

4a. Bottom of same specimen.

ASTRODAPSIS sp. indet.

Figure 5. Top of young specimen, longitude 10.5 mm., X 2. Catalogue No.

165538. U.S.N.M. Upper Etchegoin formation; locality 4708. 128 

5a. Bottom of same specimen.

338
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE L

ETCHEGOIN ECH1NODERMATA.
PLATE LI.

339
PLATE LI.

ETCHEGOIN (UPPER MIOCENE) FOSSILS: UPPERMOST

FOSSIL BED.

LlTTORINA MARIANA Arnold.

Page. 

Figure 1. Front, longitude 14.5 mm., X 2. Type, catalogue No. 165481,

U.S.N.M. Upper Etchegoin formation; locality 4718.......... 129

LITTORINA MARIANA var. ALT A Arnold.

Figure 2. Front, longitude 17 mm., X 2. Type, catalogue No. 165487,

U.S.N.M. Upper Etchegoin formation; locality 4730.......... 129

MACOMA INQUINATA Deshayes.

Figure 3. Exterior of left valve, longitude 46 mm., natural size. Catalogue 

No. 165483, U.S.N.M. Upper Etchegoin formation; locality 

4736. This species ranges from the upper Miocene to the Recent 

fauna....................................................... 131

SOLEN SICARIUS Gould.

Figure 4. Exterior of imperfect left valve, longitude 45 mm., natural size. 

Catalogue No. 165491, U.S.N.M. Upper Etchegoin formation; 

locality 4728. This species ranges from the Miocene to the 

Recent fauna, and is particularly abundant in the Coalinga district in the upper Mya zone.................................... 132

OSTREA VESPERTINA Conrad var. SEQUENS Arnold.

FigllFG 5. Exterior of left valve, longitude 42 mm., natural size. Type, catalogue No. 165545, U.S.N.M. Uppermost Etchegoin formation; 

locality 4728................................................ 132

6. Exterior of right valve, longitude 41 mm. Same locality.

MYA JAPONIC A Jay.

Figure 7. Interior of left valve, longitude 56 mm., natural size. Catalogue No, 

165479, U.S.N.M. (Perry's voyage). Upper Etchegoin formation; locality 4736. This species is intermediate between M. 

inmcataLinn. and M. arenaria Linn. and extends from the upper 

Miocene to the Recent fauna; it is a cold-water form.......... 131

8. Exterior of left valve, longitude 66 mm., natural size. Catalogue 

No. 165480, U.S.N.M. Upper Etchegoin formation; same 

locality. 

340
U. S. GEOLOQICAL SURVEY BULLETIN 398 PLATE LI

ETCHEGOIN FOSSILS.
PLATE LII.

341
PLATE LII.

TULARE (FRESH AND BRACKISH WATER PLIOCENE)

FOSSILS.

SPILERIUM KETTLEMANENSIS Arnold.

Page. 

Figure 1. Exterior of left valve; longitude 8 mm., X 4. Type, catalogue No.

165519. Tulare formation; locality 4731....................... 153

la. Interior of same specimen.

SPILERIUM COOPERI Arnold.

Figure 2. Exterior of right valve; longitude 9.5 mm., X 2. Type, catalogue

No. 165528, U.S.N.M. Tulare formation; locality 4732........ 153

2a. Interior of same specimen.

CARINIFEX MARSHALLI Arnold.

Figure 3. Front, maximum diameter 3.7 mm., X 5. Type, catalogue No.

165507, U.S.N.M. Tulare formation; locality 4732............ 153

3a. Top of same specimen. 

3b. Bottom of same specimen.

PLANORBIS VANVLECKI Arnold.

Figure 4. Top, maximum diameter 4.5 mm., X 5. Type, catalogue No. 165506,

U.S.N.M. Tulare formation; locality 4731.................... 153

4a. Bottom of same specimen.

PHYSA IIUMEROSA Gould.

Figure 5. Front, longitude 8.5 mm., X 3. Catalogue No. 165502, U.S.N.M. 

Tulare formation; locality 4732. This species ranges from the 

Pliocene to the Recent fauna.................................. 153

PHYSA WATTSI Arnold.

Figure 6. Back, longitude 6 mm., X 3. Type, catalogue No. 165503, U.S.N.M.

Tulare formation; locality 4732................................ 153

GONIOBASIS KETTLEMANENSIS Arnold.

Figure 7. Front of a rather large specimen, altitude 22.5 mm., X 2. Type, catalogue No. 165501, U.S.N.M. Tulare formation; locality 4715. 

« Also found in the Etchegoin formation........................ 153

342
U. S. GEOLOGICAL SURVEY BULLETIN 398 PLATE Lll

TUL.ARE FOSSILS.,

88170 Bull. 398 10 26
COALING A OIL DISTRICT, CALIFORNIA. 343

GONIOBASIS NIGRINA? Lea.

Page.

Figure 8. Front of somewhat imperfect specimen, longitude 6 mm., X 5. Catalogue No. 165504, U.S.N.M. Tulare formation; locality 4732. 

This species is rather rare in the Tulare. It extends to the 

Recent fauna............................................... 153

AMNICOLA ANDERSONI Arnold.

Figure 9. Front, longitude 4 mm., X 5. Type, catalogue No. 165505, U.S.N.M.

Tulare formation; locality 4732 .................:............. 153

ANODONTA KETTLEMANENSIS Arnold.

Figure 10. Exterior of left valve, longitude 59 mm., natural size. Type, catalogue No. 165522, U.S.N.M. Tulare formation; locality 4731.. 153

GONIDEA COALINGENSIS Arnold.

Figure 11. Exterior of left valve, longitude 73 mm., natural size. Type, catalogue No. 165521, U.S.N.M. Tulare formation; locality 4739.. 153

OSTREA LURIDA Carpenter.

Figure 1.2. Exterior of left valve, altitude 36.5 mm., natural size. Catalogue 

No. ]65520, U.S.N.M. Tulare formation; locality 4743. This 

species, which is much less prominently corrugated than Oslrea 

vespcrtina Conrad, ranges from the uppermost Etchegoin (upper 

Miocene) to the Recent fauna................................ 153

GENERAL INDEX.

A- Page.. 

Acknowledgments to those aiding........... 14-15

Aggradation, effect's of...................... 44-45

Aladdin Oil Co.'s well, log of.............. 225-226

Alcalde, character of......................... 25

rocks near....,.......................;.. 10C

structure near........................... 166

Alcalde Canyon, location of.................. 23-24

rocks in...................... 53-54,97,171,239

structure in....................... 166-167,221

Alcalde Hills, definition of.................... 22

description of. ............................ 34-35

fault in.'............................... 162-163

rocks of.............. 80,82-83,106-107,117,172

Alien, I. C., work of......................... 13

on quality of oils...................... 264-273

Alluvium, character and extent........... 154-157

American Petroleum Co., wells of............ 182

Anderson, F. M., on Coalinga region......... , 17,

56,59,61,63,72,74,77-78,81,87,113^ 117 

on Mount Diablo Range................ 79,141

Anodonta zone, position of................... 153

Antelope Valley, location of................. 19,20

rocks in.and near.................... 87,91,145

Anticline Canyon, location of................ 24 

section in.............................. 219-220

Anticline Ridge, definition of................. 21

description of............................ 34

future development on................ 236-237

rocks of........................... 114,149,242

 Asphalt oil, source of........................ 189

Associated area, location of.................. 213

oil of.................................... 216

structure of............................ 213-214

wells of, geology of.................... 214-216

log of................................ 216

Associated Oil Co., pipe lines of .......... 247-248

Avenal Creek, description of................. 41-42,

rocks near .............................4.. 105

. view on................................. 82

Avenal Gap, definition of.................... 23

origin of................................. 45

rocks near.......................... 145,147-148

section near............................. 147

Avenal Land and Water Co., wells of......... 230

wells of, log of........................... 230

Avenal Ridge, definition of.................. 19,22

description of......................'...... 31

rocks on................................. 55

view of.................................. 92

Avenal sandstone, correlation of............. 63

Avenal synclinc, structure of................ 108

B.

Baby King Oil Co., well of................

Becker, G. F., investigations of............

Benitoite, occurrence and nature of........

§8170 Bull, 398 10 27

230

16

51

Page. 

Big Blue, correlation of.......'............... 81

deposition of........................... 174-175

occurrence and character of.............. 76,

78,82,88-89,196-205 

origin of................................. 157

Big Gumbo sand, occurrence of........... 214-215

Big Tar Creek, description of................ 42

rocks on and near.... 53,54,68,69,70,93,119,149

sections in and near................ 92,104,120

figure showing...................... 68

Black Mountain Oil Co., wells of............ 231

wells of, log of............'............... 231

Blue Goose Oil Co., wells of................. 195

British Consolidated area, gas in ............ 201

location of............................. 196,199

oil of.......................... 198-199,200-201

 wells of, geology of............ 196-198,199-200

Buena Vista Hills, rocks of. ............... 79

C.

Caledonian area, location of................. 213

oilof.................................... 216

structure of........................... 213-214

wells of, geology of.................... 214-216

logof................................ 216

California Oil and Gas Co., wells of.......... 195

wells of, section near.................. 219-220

California Oilfields area, location of........ 201,203

oil of...:...................... 202-203,204-205

wells of, geology of............ 201-202,203-204

California Oilfields Co., development by... 181-182 

Call area, location of......................... 206

oil of.................................... 208

wells of, geology of.................... 20f>-208

Canoas Creek, description of................ 42

rocks on............... 69,70,84,93,102-103,148

sections on......................... 84,102,119

Caribou area, gas in......................... 201

location of............................... 199

oil of.................................. 200-201

wells in, geology of.................... 199-200

Castle Mountain, definition of............... 21-22

description of...'........................ 31

faults in............................... .1.67,174

Chanslor & Canfield, wells of................ 180

Chico formation, fossils in....... 53,56,56, .58,60-61

fossils in, plate showing................. 274

oil in........ 61-62,182,189,183,188-189,234,236

See also Knoxville-Chico. 

Cholame Creek, location of.................. 21

Clear Field Oil Co., well of.................. 180

Climate, character of......................... 26

Coal, deposits of............................. 49

Coalinga, character and location of........... 25

rocks near............................... 55

Coalinga anticline, description of...... 165-166,168

345
346 GENERAL INDEX.

Page. 

Coalinga anticline, views of............. 32,162,190

Coalinga beds. See Glycymeris zone.

Coalinga district, definition of............... 18

location of............................... 25

 sections across, figure showing........... 161

Coalinga field, definition of.................. 18

rocks of..............................89-90,117

Coalinga Oil Transportation Co., pipe lines of. 247 

Coalinga syncline, description of........... 165-166

Coast Range Oil Co:, well of.................. 180

Columnar section, figure showing.'........... 47'

Commercial Petroleum Co.'s well, section 

near....................................... 222

Confidence area, location of.................. 206

oil of.................................... 208

wells of, geology of..................... 206-208

Conglomerate, occurrence and character of... 156 

Consolidated Oil and Development Co., 

wells of..................................:. 230

Cooper, J. G., paleontology by...... 17,142,153-154

Cooperation, advantages of.................. 15-16

Crescent Oil Co., wells of.................... 195

Cretaceous rocks, concretions in, view of..... 40

oilfrom...............?"............ 11,188-189

views of................................. 40,54

Sec also Khoxville-Chico. 

Cretaceous time, events in................. 170-171

Curry Mountain, description of.............. 30

rocks of.............................. 52-54,83

structure of............................ 166,220

view of........................'.......... 54

D.

Dagany Gap, definition of................... 23

future development near.....:........ 239-241

Davis, E. P., work of....................... 15,192

Development, description of................. 233

future of............... 1............... 233-245

Diablo anticline, structure of................ 168

Diablo Range, definition of................... 19-20

description of............................ 27-31

ridges of................................. 28-29

roads across............................. 25

rocks of...................... 28,50,113,141,163

Dikes, view of............................... 66

Domijean sands, correlation of............... 63-64

Drainage, changes in........................ 43-45

description of............................ 39-42

Drilling, profitable depth of................. 234

Dudley, character of. ........................ 25

Dudley-Lemoore road, definition of.......... 25

section near.......................... 147-148

E.

Eastside field, definition of.................. 182

description of.......................... 196-206

development in......................... 181

future of............................... 235-236

oil of.................................... 184

territory northwest of, future of.......... 235

wells in.....................:.;....... 261,263

See also particular areas. 

Echinarachnius zone, position of............. 136

EICerrito Oil Co., well of.................... 232

Eldridge, G. H., work of................. 13,14,17

Elk Hills, rocks of........................... 79

Page. 

Eocene rocks, subdivision oi................. 63

oil from......... '........................ 11

See also Tejon formation. 

Eocene time, events in.................... 171-172

Erosion, changes due to..................... 43-45

Esperanza Oil Co., well of................... 233

Etchegoin formation, age of............... 139-140

character of................ 76,113-124,242-243

contact of, with Tulare formation....... 144

correlation of................ 48,95,138-139,140

deposition of.......................... 177-178

distribution of......................... 117-124

fossils in...............'............. 76,124-137

plates showing.................... 312-340

zones of....................... 113,136-137

view of.......................... 82

oil in.......... i..!...................... 140

origin of............................... 137-138

sections of..................... 119-120,123-124

figures showing.................... 101,122

F.

Fairbanks, H. W., on Santa Margarita formation.......................... 88

on Paso Robles formation .......'........ 142

Faulting and folding, changes due to. 43-45,162-163 

character of........................... 168-169

occurrence of............................ 174

Field work, extent of......................... 13

Florence Oil Co., well of..................... 233

Folding. See Faulting and folding.

Foothills, description of..................... 32-37

view of.................................. 26

rocks of................................. 28,32

separation of............................ 28

Formations, correlation of................... 48

succession of............ 1................ 46

figures showing..................... 47,191

Fossils. See particular formations; also Index of 

fossils.

Franciscan formation, character of....... 50-51,175

correlation of............................ 48

deposition of............................ 169

distribution of........................... 51

igneous rocks in......................... 157

relation of, to oil........................ 51

G.

.Garza Creek, description of.................. 42

rocks of................................. 53,69

Geologic history, account of............... 169-179

Geology, character of.......................'. 11

columnar section showing............... 47

description of........................... 45-179

early knowledge of...................... 16-18

Gibbs Oil Co., well of....................... 233

Glycymeris zone, character of.......... 76,114-115

correlation of............................ 77

fossils of................................. 78

position of............................. 76,136

Guijarral Hills, definition'of................. 23

description of........................... 34

future development of................. 236-237

rocks of................................. 149

Gypsum, deposits of........................ 49-50
GENERAL INDEX.

Henshaw well, water of..................... . 227

Hess, F. L., on gypsum..................... 50

Hillebrand, W. F., analyses by......... 14,158,159

Home Oil Co., well of..................... 180-181

Horsetown formation, absence of............ 52

I.

Igneous rocks, description of.............. 157-160

Indicator stratum, nature and use of........ 81-82

Iowa Oil Co., well of......................... 233

J.

Jacalitos anticline, future development at.. 238-239

Jacalitos Creek, description of............... 41

rocks near......... 51,89,96,98,100-102,106,239

section on............................... 99

figures showing.......................... 100

Jacalitos formation, age of:................ 111-113

character of.......... 76,78,96-108,112-113,243

correlation of................... 48,78,91-92,95

deposition of.......................... 176-177

distribution of................... 97,98-108,112

fossils of............................... 108-113

plates showing..... 300,302,304,306,308,310

zones of............................. Ill

oil in....................... 11,113,182,183,185

recognition of........................... 96-97

 relations of.............................. 97-98

sections of.......................... 99,102,104

figure showing...................... 100

view of.................................. 190

Jacalitos Hills, definition of.................. 22

description of............................ 35-36

rocks in................. 80,83,105-106,148-149

structure in........................... 167,168

view in.................................. 26

Jasper Canyon, location of................... 24

rocks of................................. 93

Joaquin Ridge, definition of................. 21

description of............................ 29-30

hills near................................ 34

rocks of..................... 75,172,175,177,241

section on............................... 59

structure of.............................. 165

Juniper Ridge, definition of.................. 21

description of............................ 30

rocks of........;..................... 52-54,173

structure of.............................. 220

Jurassic rocks. See Franciscan formation.

Jurassic time, events in.................... 169-170

K.

Kerr, W. P., development by J............ 181-182

Kettleman Hills, definition of............... 24

description of............................ 36-37

future development In................. 241-245

oil wells in............................. 181,184

rocks of........ 113-116,120-124,141-148,241-244

section in............................... 123-124

soil of.................................... 156

structure of............................ 165,241

Kettleman Hills field, definition of..... 19,182,232

geology of............................... 232

ofl of..................................... 232

wells of, geology of..................... 232-233

Kettleman Plain, definition of............... 24

Kettleman Plain, rocks of................... 141

soil of.................................... 156

structure of.............................. 166

Kings County Oil Co., wells of............. 230,231

wells of, log of........................... 231

Knoxville-Chico rocks, age of.......... 53,55,60-61

character of.............................. 51-60

correlation of............................ 48

deposition of........................... 170-171

distribution of............................ 52-53

fossils in..................... 53,55,56,58,60-61

plate showing....................... 274

See also Chico.

Kreyenhagen field, geology of.............. 228-229

location of.......................... 18,182,227

map of .....:................... ......... 228

oil of.............................. 184,228-229

rocks of............................... 89,90-94

structure of............................... 228

wells Of................................ 229,263

wells of, geology of... ................... 229-232

logs of............................. 230,231

Kreyenhagen Hills, definition of............. 22

description of. ........................... 35-36

future development of................. 239-241

oil wells of............................... 181

rocks of................................ 98-104,

115,116,118-120,148-149,163,177 

Kreyenhagen Oil Co., wells of............... 229

Kreyenhagen shales, correlation of........... 63

L.

Larsen, E. S., jr., on syenite................ 14,158

Laval grade, definition of.................... 24

Location of area............................. 11,25

map showing............................ 12

Los Gatos Creek, description of.............. 40-41

faults on................................ 163

hills near................................ 33-34

rocks near............ 55,57-58,65,66-67,90,118

structure near........................... 166

Lost Hills, Structure of........?........... 165,244

Lucile well, opening of...................... 181

M.

McClurg, J. A., wells of...................... 181

McKittrick formation, occurrence and character of.......................... 79-80

McLure Valley, definition of.....:........... 24

hills near................................ 37

rocks of and near.. 89,90-91,93,97,104-105,120 

structure of.............................. 168

view in................................... 92

Map, index, of southern California........... 12

Map, structural, of Coalinga district.......Pocket.

Maps, contour, of Coalinga field....... 228, pocket.

accuracy of............................ 192-193

explanation of......................... 189-190

Maps, geologic.of Coalinga field and district. Pocket, 

preparation of......................... 192-193

sections of, plates showing............. 190,192

use of................................. 190-192

Marshall, K. B., work of..................... 15

Mason, S. G., aid of......................... 14

Mercantile Crude area, location of.......... 208-209
348 GENERAL INDEX.

Page. 

Mercantile Crude area, oil of ................ 210

wells of, geology of.................... 209-210

log of................................ 210

Mineral lands, classification of............. 245-246

Mineral water, prevalence of................. 26

Miocene rocks, bluffs of, view of............. 90

correlation of............................ 77-79

description of............................ 75-77

See also Vaqueros; Santa Margarita;

McKittrick; Etchegoin. 

Miocene time, events in................... 173-176.

M., K. & T. area, location of.............. 210-211

act of.................................... 213

wells of, geology of.................... 211-213

logof................................ 213

Movement, periods of....................... 162

Mulinia zone, position of..................... 136

Mutual OilCo.,wellsof..................l.. 195

Mya zones, position of....................... 136

N.

Nevada Petroleum Co., wells of............. 182

New York Oil Co., wells of.................. 195

Northwest field, wells in.................... 263

O. 

Oceanic Oil Co., well of...................... 233

Oil, accumulation of............... 185-186,234-235

calorific value of................... 265,269-270

examination of, results of.............. 267-272

. flash pointof...................... 265,267-268

fractionation of................ 265-266,269-272

origin of............................... 188-189

production of.......................... 246-247

quality of.......................... 11,264-272

rocks carrying.................. 49-154,182-183

See also particular formations. 

specific gravity of......... 186,264-265,267-268

sulphur in......................... 265,269-270

total resources of........................ 15

types of................................. 11

water in............................... 269-270

zones of............................... 183-185

relations of, figure showing.......... 190

See also particular areas, fields, etc. 

Oil Canyon, gypsum near................... 49

location of............................... 24

rocks at and near.................... 82,98,115

, analysis of........................... 66,82

Oil City, character of........................ 25

oil near.................................. 61-62

rocks near.................. 57-59,64-66,79,172

Oil City field, location of.................. 182,193

oil of.............................. 183,195-196

rocks of................................ 193-194

sands of, section of....................... 194

view in................................. 32

wellsin................................ 261,263

geology of............................... 194

log of...:.......................... 194-195

Oil companies, list of...................... 248-263

Oil fields, character of....................... 25

Oil lands, area of........................... 11,182

development of........................ 179-182

Oil wells, lists of........................... 248-263

Oil zones, location of, section showing....... 46

Qrcutt, W. W., work of. ....... ? ..... s ...... 179

p- Page. 

Pack, K. W., work of........................ 58

Paleontology, aid of......................... 17,18

Paso Robles formation, correlation of........ 142

Pecten coalingaensis zone, position of....... 136

Pecten estrellanus bed, view of............. 94

Peerless area, location of......'............... 196

oil of .................................... 198-199

wells of, geology of................. 196-498,199

Petroleum. See Oil.

Phoenix Oil Co., well of, log of............. 194-195

Physiography, development of.............. 43-46

factors influencing................... 42-43,160

Picnometers, description of................ 264-265

figure showing........................... 264

Pierce, J. H., fossils collected by............. 94

Pipe lines, routes of....................... 247-248

Place names, definition of.................... 18

Plains, origin of............................. 44

Pleasant Valley, coal in...................... 49

definitionof............................. 23

gypsum in............................... 49

rocks in and near....................... 64-66,

81-82,90,97,107-108,117,148,149

structure of............................ 166,220

Pleistocene rocks, correlation of.............. 77-79

description of............................ 75-77

view of.................................. 94

Sec also Tulare formation. 

Pleistocene time, movement in.............. 162

Pliocene rocks, correlation of................. 77-79

description of............................ 75-77

See also Tulare formation. 

Polonio Pass, location of..................... 20

Polvadero Gap, definition of................. 23

rocks near............................... 149

Porter & Scribner area, location of......... 210-211

. oilof.................................... 213

wells of, geology of..................... 211-213

logof................................ 213

Post-Eocene rocks, description of............ 75r77

See also Miocene; Pliocene; Pleistocene. 

Producers and Consumers Oil Co., wells of... 180 

Producers Transportation Co., pipe line of... 248 

Pulaski sand, occurrence of.................. 198

Pyramid Hills, definition of.................. 22-23

rocks of.................................. 90-92

structure of............................ 167-168

Q.

Quaternary time, events in.................. 179

Quicksilver, investigation of................. 16

R. 

Railroads, access by..:..................... 11,247

Rainfall, amountof........................... 26

Ransome, F. L., on California fossils......... 152

Reef beds, name of.......................... 81

view of.................................. 80

See also Vaqueros. 

Reef Ridge, definition of..................... 22

description of............................ 30-31

future development near................ 239-241

rocks of............ 54,57,59,67-70,75,80,83-84,

SO, 90-94, 97-98,145-140,172,173-174, 228 

figure showing........................... 68

streams crossing......................... 4g
GENERAL INDEX. 349

Page. 

Relief, description of........................ 26-42

Roads, access by............................ 25

Rocks. See Formations.

Rowland & Lacy, wells of................... 180

S.

St. Lawrence Oil Co., well of.............. 231-232

St. Paul sand, occurrence of............ 201,203,235

Salina Valley, rocks of....................... 142

San Joaquin Valley, view in................. 94

San Joaquin Valley coal mine area, geology

of............................. 217-220

. location of..:............................ 217

oil of.................................. 220,227

sections in........."................ 219-220,222

structure of............................ 220-222

wells of, geology of.................... 222-226

logof..............................'-. 225

Santa Margarita(?) formation, age of........ . 95

character of................ 70,77,78,88-94,243

correlation of...................... 48,78,79,95

deposition of........................... 174-176

fossils.in...................!....... 76,79,94-95

. bed of, view of....................... 94

plates showing................ 298,300,302

oilin......................... 95-96,182,183,184

section in................................ 92

views of................................ 92,190

Sauer Dough sand, occurrence of............ 198

Scope of paper. ............................... 12-14

Selma Oil Co., wells of....................... 195

Serpentine, occurrence of................ 50-51,157

Silver Tip well, yield of................... 180,226

Soda syenite, analyses of.................... 159

occurrence and character of............ 158-160

Soil, character and extent of................. 156

Standard area, gas in........................ 201

location of......................... 199,201,205

oil of...................... 200-201,202-203,206

wells in, geology of........ 199-200,201-202,205

Standard Oil Co., development by.......... 182

pipe lines of............................. 247

Stanislaus Oil Co., well'of................... 233

Stockholders area, location of................ 205

oil of..................................... 206

wells of, geology of...................... 205

Stockton Oil Co., well of..................... 233

Stratigraphy, description of................. 47-48

section showing........................ ^ 191

Structure, description of................... 160-169

relation of, to physiography......... 42-43,160

Sullivan, E. C., on White Creek cement..... 157

Sulp'hur Spring Canyon, location of.......... 24

rocks of............................ 69,238-239

Sulphur water, occurrence of.............. 187,209

Sunnyside Oil Co.'s wells, location of........ 226

oil of.................................... 227

wells of, geology of.................... 226-227

S. W. & B. area, location of............... 208-209

oil of.................................... 210

wells of, geology of.................... 209-210

log of..............................:. 210

Syenite, analyses of......................... 159

occurrence and character of............ 158-160

T. 

Tamiosonia zone, character of...... 76,78,88,90,96

position of............................... 76,90

Sec also Santa Margarita formation. 

Tar springs, occurrence of................... 228

T. C. area,location of........................ 190

oil of.................................. 198,199

wells of, geology of................ 196-198,199

T. C. OilCo.,wellof...................... 182,235

Tejon formation, age of...................... 70-74

character of............................. 62,76

contact of, with Vaqueros............... 62,86

view of.............................. 54

correlation of......................... 48,77-78

deposition of.......................... 172-173

distribution of........................... 64-70

fault in, view of......................... 66

fossils in.............................. 69,70-74

plates showing................ 276,280,284

oil in.. 11,74-75,182,183,184,186,188-189,229-230 

view of.'......... , ....................... 66,162

Temblor beds. See Vaqueros sandstone. 

Temblor Range, definition of..............:. 20-21

rocks of............................ 79,142,145

Tent Hills, definition of..................... 23

rocks of................................. 91

view of.................................. 92

Terrace deposits, character and extent..... 154-157

Tertiary rocks, deposition of............... 171-179

movement in...................... 162-163,176

oil of.................................. 188-189

views of................................. 26

Tilting, effects of............................ 43-45

Topography, description of.................. 26-42

relation of, to structure.............. 42-43,160

Transportation, facilities for............... 247-248

Tulare formation, age of................... 153-154

character of..................... 75-76,140-149

contact of, with Etchegoin............ 144-145

correlation of............................ 48

deposition of.......................... 178-179

distribution of..................... 115,143-149

fossils of....................... 143-144,153-154

plates showing.................... 328,342

oil and, relation of....................... 154

origin of............................... 149-153

sections of............................. 147-148

figure showing....................... 122

Tulare Lake, description of.............. 38-39,155

rocks near............................. 113,152

TJ.

Unconformities, description of............. 164-165

Union area, location of...................... 213

oil of.................................... 216

structure of........................... 213-214

wells of, geology of.................... 214-216

log of................................ 216

Uplift, effects of..........................^.. 43-45

V.

Valleys, description of....................... 38,44

Vaqueros sandstone, age of.................. 87-88

characterof.................... 76,77,80-81,244

contact of, with Tejon................... 62,80

view of.............................. 54

correlation of...................... 48,78-79,87
350 GENERAL INDEX.

Page. 

Vaqueros sandstone, deposition of........... 173

distribution of........................... 80-84

fossils in........................... 82,83,84-88

plates showing......... 288,290,292,294,296

oil in..................... 11,80,88,182,183,184

views of.....:.................. 1....... 80,162

Vegetation, character of..................... 26

Vivianite, occurrence of...................... 97

Volcanic ash, occurrence of................ 105-106

W.

Waltham Creek, description of............... 40,41

location of............................ 21,23-24

oil wells near............................ 181

See also Waltham Creek area, 

rocks near...... 80-81,89,91,95,106-107,118,177

structure near......................... 167,221

Waltham Creek area, geology of........... 217-220

location of............................... 217

oil of.................................. 226,227

sections in......................... 219-220,222

structure of............................ 220-222

wells of, geology of..................... 222-226

logof................................ 225

Water, effect of, on oil..................... 185-186

relation of, to oil....................... 187-188

trouble with..................... 15-16,229,240

Water, underground flow of.................. 26

Watts, W. L., investigations by............ 16-17,

142,151,179-180

Wells, oil, profitable depth of............... 11,234

yield of............:..................... 11-12

See also particular fields, areas, etc.

Page.

Wells, R. C., analyses by....... 14,50,66,93,97,149

Westlake-Rommel Oil Co., location of....... 226'

oil of.................................... 227

wells of, geology of..................... 226-227

Westside field, definition of.................. 182

description of......................... 206-227

development of!................... 181,182,184

future of............................... 237-238

water in............................... 237-238

wells in................................ 261-263

See also particular areas.

White Creek, rocks on....................... 18,

114,115,117-118,156-157,158-160 

structure near................"........... 166

terraces on............................... 186

Whitney, J. D., explorations by............. 16,63

on Mount Diablo........................ 19-20

Z.

Za^ato Creek, description of................. 42

rocks on....... 67,68,93,98,100-103,119,148-149

terraces on....'.......................... 156

view of.............................. 40

Zenith Oil Co.:

wells of.................................. 195

Zier area, location of....................... 210-211

oil of.................................... 213

wells of, geology of.................... 211-213

logof................................ 213

Zones, oil, distinction between.............. 186
INDEX OF FOSSILS.

[Figures In italic denote position of illustrations.]

A- Page. 

Actaeon sp.................................. 71

Agasoma gravida Gabb..................... 87

kernianum Cooper ...................... 85,86

santacruzana Arnold............. 85,86,87,294

Amauropsis alveata Conrad................ 71, 286

oviformisGabb........................ 71,884

Ammonites................................. 53,60

Amnicola andersoni Arnold............... 153, 84$

turbiniformis Tryon..................... 154

sp........................................ 153

Anodonta decurtata Conrad................ 144,154

kettlemanensis Arnold................. 153, S4S

nuttalliana Lea.......................... 154

Anomia lineata Gabb....................... 60

Anthozoa .......................... 72,125,128,131

Area obispoana Conrad.......... 85,86,101,137,144

osmonti Dall..................... 85,86,87,292

trilineata Conrad..................... 108,110,

112,125,128,131,136,3/4 

vancouverensis Meek.................... 60

sp....................................... 131

Architectonica hornii Gabb.................. 72

sp....................................... 61

Astrangia coalingensis Vaughan....... 128,131, 384

Astrodapsis................................. 99

jacalitosensis Arnold.............. 110, 111, SOS

tumidus R&nond....................... 131

whitneyi R&nond...................... 94,300

sp..................................... 128,355

Astyris richtofeni Gabb ................... 132, $28

Aucella crassicollis Keyserling............... 53

Avicula lingucefonnis Evans and Shumard. 60,274

B.

Baculites.................................... 53,58

chicoensis Trask. ....................... 60, 274

sp....................................... 61

Balanus concavus Bronn.................. 127,130

sp....................... 85,86,110,111,130,133

Barbatiamorsel Gabb................... 70,73,250

Bathytoma carpentariana Gabb var. fernandoana Arnold................. 129,132

piercei Arnold....................... 85,86, £96

Belemnites impressus Gabb................. 53

Boreotrophon stuarti Smith............... 130, 388

Brachiopoda...................:... 72,125,128,131

BranchiolambrusaltusRathbun............. 85,86

C.,

Calliostoma coalingensis Arnold....... 129,132, 3S4

kerri Arnold ...................... 129,132, SS4

Cancellaria andersoni Arnold............ 85,86, 296

elongata Gabb........................... 72

irelaniana Cooper....................... 71, 286

trifonidea Gabb............... 126,129,132, 332

vetusta Gabb.................... 85,86,87,296

Page. 

Cancer fissus Rathbun...................... 133

Carcharodon arnoldi Jordan .............. 130, 329

Cardium.................................... 122

breweri Gabb........................... 70

cooperi Gabb........................ 70,72, 280

coosense Dall...................... 125,128,131

meekianum Gabb..... 110,112,125,131,136, 312

(Trachycardium) vaquerosesis F. M. Anderson..............!....... 85,86,296

sp.................................. 70,108,131

Carinifex marshalli Arnold ................ 153, 342

newberryi Lea.......................... 154

Cassidulus californicus F. M. Ahderson..... 70,0&£

Cephalopoda................................ 60

Cetacea...................................... 130

Chama pellucida Broderip................. 128, 332

ChioneconradianaP.M. Anderson....... 85,86,94

securis Shumard............... 108,110, 111, 308

temblorensis F. M. Anderson.... 85,86, £94, 308

Chlamys \vattsl Arnold...................... 884

Chrysodomus imperialis Dall.......... 110,132, 806

portolfensis Arnold............ 110,112,126, SS2

Cinuliaobliqua Gabb........................ 61

Cirripedia........................ 85,86,94,109,110

Clidiophora punctata Conrad.............. 131, S36

Conus hayesi Arnold.................... 85,86,290

owenianus F. M. Anderson.......... 85,86,296

Corbicula dumblei F. M. Anderson...... 85,86, 294

Corbula parilis Gabb....................... 70,270

Crassatellites grandis G abb............. 70, 277,281

Crepidula prserupta Conrad.................. 87

princeps Conrad........... 110,126,129,132, 324

sp....................................... 85,86

Crustacea....................... 85,86,127,130,133

Cryptomya ovalis Conrad... 94,108,112,128,131, 322 

quadrata Arnold.................. 125,320,322

Cumingia californica Arnold............... 125,131

Cyclammina sp............................. 72

Cylichna costata Gabb................... 71,72, 286

D.

Dentalium cooperi Gabb............. 71,72,73,285

Desmoceras hoffmannl Gabb................ 61

Diplodonta harfordi F. M. Anderson......... 110,

112,131,136,3/2 

parilis Conrad.................. 110,131,136, 312

sp....................................... 108

Dosiniajacalitosana Arnold........... 110,111,3/0

mathewsoni Gabb................... 85,86,255

ponderosa Gray.................. 85,86,94,20ff

E. 

Echinarachnius............................ 122,138

gibbsi Remond........................ 108,110,

111, 112,125,128,131,136,220, 304, 316,318,338 

var. ashleyi Arnold.................. 316

351
352 INDEX OF FOSSILS.

Page. 

Echlnodennata.............................. 85,

86,94,108,110,125,128,131, 284-288 

Ellipsosmilia granullfera Gabb............... 72

F. 

Ficuspyritiformis Gabb..................... 85,86

Foraminifera................................ 72

Forreria barton! Arnold................. 85,86, 292

carisensis F. M. Anderson.............. 94, 298

coalingense Arnold..................... 133, 328.

gabbianum F. M. Anderson..... 85,86, 288,2PO

var. cancellarioides Arnold.......... 85,86

ponde ros iim Gabb... 109,110, 111, 127,133, 306 

Fusus diaboli Gabb......................... 72

martinez Gabb.......................... 72

remondii Gabb.......................... 71

G.

Galerus excentricus Gabb................... 71, 284

Garitexta Gabb............................. 72

Gasteropoda....................... 60,72,85,86,94,

109,110,126-127,129-130,132-133,153, 284-288

Glycymeris.................................. 219

coalingensis Arnold............ 125,131,136, 316

septentrionalisMiddendorf. 125,128,131,136,3/8 

veatchi Gabb............................ 61

sp..................................... 108,125

Gonidea coalingensis Arnold............... 153, 848

coalingensis Arnold var. cooperi Arnold . 153

Goniobasis................................... 138

Kettlemanensis Arnold............ 129,153, 842

nigrina Lea............................ 153, 343

occata Hinds............................ 154

Gyrodes sp.................................. 61

H. 

Hinnites.................................... 58

Hinnites giganteus Gray.................... 94, 298

I. 

Inoceramus.................................. 53,60

whitneyi Gabb.......................... 61

L. 

Lagena sp................................... 72

Leda gabbi Conrad.................:. 70,72,73, 276

Littorina.................................... 144

grandis Middendorf...................... 137

mariana Arnold............ 129,133,137,153, 840

var. alta Arnold .......... 129,133,137,'840

Loxorhynchus grandis Stimpson............ 133

Loxotrema turrita Gabb.................... 71, 285

Lunatia hornii Gabb...'.............. 71,72,73,285

lewisii Gould.......... 109,110,127,129,133,S£2

sp................................... 60,71, 285

Lytoceras sacya Forbes...................... 61

M.

Macoma inquinata Deshoyes.. 125,128,131,137, 840 

jacalitosana Arnold.................... 110, 310

nasuta Conrad.......... 94,125,128,131, 818,828

piercei Arnold!....................... 85, 86,292

secta Conrad ............ 85,86,110,112,131, 318

vanvlecki Arnold............. 110, 111, 302,810

sp................................. 110,131,308

Mactra albaria Conrad..................... 125,816

ashburneri Gabb........................ 60,074

coalingensis Arnold................ 125,131,3.85

Page. 

Mammalia................................. 109,110

Margarita johnsoni Arnold................. 110, 308

' sp ...................................... 133

Margaritana subangulata Cooper............ 154

Meekia sella Gabb.......................... 60, 274

Melongena sp............................. 110, 111

Meretrix gabbi Arnold..................... 10,280

hornii Gabb............................ 70,281

ovalis Gabb. ..../....................... 70,280

uvasanaConrad........................' 70,281

Metis alta Conrad............... 85,86,108,110,250

sp................................. 110,125,131 . Miltha sancttecrucis Arnold................ 85, 290

Modiola ornata Gabb........................ 72

Modiolus directus Dall...................... 131

rectus Conrad................. 125,128,131, 318

Monia macroschisma Deshayes.... 108,110,112,306

Morio tuberculatus Gabb.................... 72,73

Mulinia................................... 122,123

densata Conrad............... i... ; ...... -85,

86,108,110,125,128,131,136, SIS, 320

densata Conrad var. minor Arnold... 85,86, 288

Mya................................... 101,118,144

arenariaLinneus.......;................ 340

j aponica Jay.......... 125,128,131,136,137, 840

truncata Linneus....................... 340

Mytiloconcha coalingensis Arnold........... 110,

112,125,128,131,139, 316,322 

incurvus Conrad........................ 139

Mytilus (Mytiloconcha) coalingensis Arnold. 110,

112,125,128,131,139, S16,322

incurvus Conrad........................ 137

mathewsoni Gabb var. expansus Arnold. 85,

86,95, aSS 

N.

Nassa californiana.Conrad......... 127,129,133, 884

californiana Conrad var. coalingensis

Arnold........'........ 127,129,133.335

Natica. .................................... 127.

Neritaglobosa Gabb........................ 72

triangulata Gabb....................... 11,285

Neveritacallosa Gabb....................... 85,86

recluziana Petit............... no, 130,133,sis

var. alta Dall................. 127,130,3^5

sp....................................... 110

Nodosaria sp................................ 72

Nucula castrensis Hinds.................... 129

sp...................................... 60,122

0.

Ocinebra topangensis Arnold............ 85,86, 296

Olivella biplicata Conrad...................: 133

pedroana Conrad ..................... 130,133

Opalia sp................................. 130,133

Orbitolites sp............................... 70,280

Ostrea..................................... 101,122

atwoodi................ 110,112,126,132,136, SIS

aviculiformis F. M. Anderson........ 70,73, 277

idraensis Gabb......................... 70, 276

lurida Carpenter........... 129,132,153,154, 843

sculpturata Conrad....................... 139

titan Conrad...... 85,86,87,95,112, 288,298,300

vespertina Conrad..... 129,132,137,138,139, 326

var. sequens Arnold... 129,132,137,138, 340 

sp.................................. 70,126,129
OF FOSSILS.; 353

p.

Pachydiscus sp.............................. 60

Panopea......................:............ 101,102

estrellana Conrad.............. 109,110, 111, SOS

generosa Gould............ 110, 111, 126,132, 314

Paphiajacalitosensis Arnold.'.............. 110, 310

staleyi Gabb.......... 109,112,126,129,132, 338

tenerrima Carpenter........... 110,112,126, 806

truncata Gabb.......................... 126

Patinopecten oweni Arnold.................. 324

Pecten..................................... 76,101

andersoni Arnold ......... 84,85,86,87,146, 892

bowersi Arnold.,........................ 87

coalingaensis Arnold..................... 101,

119,129,132,136,137,138, 332 

crasslcardo Conrad..... 85,86,94,95,109, 111, 802

deserti Conrad..................... 129,139,332

estrellanus Conrad....................... 85,

86,94,95,101,102,106,107,109,110, 111, 112, 898 

gibbus var. concentricus Say............ 139

interradiatus Gabb ............. 70,73, 280,281

magnolia Conrad........................ 87

miguelensis Arnold...................... 85,86

nutteri Arnold........................ 129, 334

(Patinopecten) oweni Arnold........... 109,

110, 111, 112,126,129,132,136,219, S24 

peckhami Gabb.................. 70,73,74, S80

(Chlamys) wattsi Arnold ....:........... 119,

126,129,132,137,334 

var. etchegoini F. M. Anderson.... 129,137

Pectunculus............................... 316,318

veatchiiGabb............................ 61

Pelecypoda................................. 60,

72, 85, 86, 94, 108-109, 110, 125-126,

128-129,131-132,153, 276-277,280-281

Perissolax brevirostris Gabb............... 60, 274

Petricola sp................................. 70

Phacoides acutilineatus Conrad...... 85,86,126, 294

ovoidea Gould ........................... 132

(Miltha) sanctsecrucis Arnold....... 85,86, 290

Physa costata Newcomb.................... 154

humerosa Gould...................... 153, 342

wattsi Arnold......................... 153, 342

Pisania fortis Carpenter var. angulata Arnold................................. 127,133

Pisces..................... 109,110,127,130,133,153

Placunanomla californica Arnold.......... 129, 826

inornata Gabb.................. 70,73,280,281

macrochisma Deshayes.................. 306

Plagiopecten deserti Conrad................. 332

Planorbis tumeris Carpenter................. 415

vanvlecki Arnold ..................... 153, 348

Pleurotoma coalingensis Arnold........... 133, 322

domenginei Arnold..................... 71, 285

fresnoensis Arnold...................... 71, 285

guibersoni Arnold...................... 71,285

(Bathytoma) piercei Arnpld......... 85,86, 296

Pliohippussp .......................... 98,110,300

Polyrnorphina sp........................... 72

Potamides carbonlcola Cooper........... 71, 73,284

i Pseudocardium gabbi Rdmond.............. 320

 Pulvulina sp................................ 72

Purpura .................................. 308,314

R. 

Rimella canalifera Gabb..................... 71, 284

Sagrina sp................:.................. 72

Saxidomus nuttalli Conrad........ 109,126,132, 320

vaquerosensis Arnold............... 85,86, 292

Schizodesma abscissa Gabb........... 110,111/302

Schizotluerus nuttalli Conrad...... ........ 126

pajaroanus Conrad............ 109, 111, 112,126

Scutella..................................... 84

merriami F. M. Anclerson........ 85,86,87, 290

perrini Weaver........................ 128, 338

Semele rubropicta Ball.................... 132,355

Septifer coalingensis Arnold............. 85,86, 288

dichotomies Gabb...................... 70,276

Serpulorbissp.............................. 71,254

Sigaretus scopulosus Conrad .............. 127, 326

Siliqua nuttalli Conrad ................... 126,132

sp....................................... 132

Solen paralellus Gabb....................... 70

sicarius Gould...... 94,110,126,129,132,137,340

Sp.............:......................... 60

Sphaerium cooperi Arnold................. 153, 342

dentatum Haldeman.................... 154

kettlemanenis Haldeman ............. 153, 8$

Spiroglyphus tejonensis Arnold............ 71,285

Spondylus carlosensis F. M. Anderson...... 70,270

T.

Tamiosoma gregaria Conrad.................... 76,

94,95,110, 111, 112,127,133, SD8 

Tapes staleyi................................ 332

Tellina aragonia Dall J................. 110, 111, 306

hornii Gabb...................... 70,72,73,270

joaquinensis Arnold.................... 70,277

ooides Gabb............................ 60,27.$

sp....................................... 70

Terebratalia occidentals Dall................ 131

smithi Arnold................. 128,131,137,334

Terebratella sp .............................. 72

Thais........................................ 314

crispatus Chemnitz ............ 110,130,133, 300

etchegoinensis Arnold............. 130,133,3/4

kettlemanensis Arnold..... 110,112,127, 308,820

Thracia jacalitosensis Arnold.............. 110,3/0

Tivela inezana Conrad....................... 85,86

Trachycardium vaquerosensis Arnold........ 85,

Transennella californica Arnold............ 129, 382

Tritonidea kreyenhageni Arnold............ 71, 285

Tritonium californicum Gabb.............. 71, 284

Trochita filosa Gabb......... 85,86,127,130,133,137

sp....................................... 85,86

Trochosmilia striatus Gabb.................. 72

Trochosyathus striatus Gabb................ 72

Trophon (Forreria) bartoni Arnold...... 85,86, 292

(Forreria) carisaensis F. M. Anderson.... 94,

95,898 

(Forreria) coalingense Arnold.......... 133,322

(Forreria) gabbianum F. M. Anderson... 85,

86,888,890 

var. cancellarioides Arnold.......... 85,86

(Forreria) ponderosum Gabb............ 109,

110,111,127,133,300 

(Boreotrophon) stuarti Smith......... 130, 328

Turritella ineziaua Conrad................... 87
INDEX'OF FOSSILS.

'',*. - Page.

Turritella ocoyana ................ 84,85,86,87, S94

pachecoensis Stanton........,.-.... 71,72,73, 286

uvasana Conrad........................ 71, 285

vanvlecki Arnold................;..... 127,322

V.

Vaginulina sp. ........................ 72

Venericardia alticostata Gabb.............. 70, 281

hornii Gabb............................. 72

planicosta Lamarck.............. 70,72,73, 276

sp....................................... 70

Venuspertenuis Gabb................... 85,86, 294

Venus varians Gabb.

Page. 

. 60

Volutoderma gabbi White.................. 60,274

' 'X. . - ' 

Xenophora sp ........'....................... 71

Xylotrypasp............................ 85,86,130

Yoldia impressa Conrad. .................... 85, 36

Z.

Zirphaea dentata Gabb ....... 85, 86, 94, 110, 111, 292

gabbi Tryon.......... ................... 129,132

o

ot