Tertiary Stratigraphy 

of the Southeastern 

San Joaquin Valley, 

California

GEOLOGICAL SURVEY BULLETIN 1529-J

Tertiary Stratigraphy 

of the Southeastern 

San Joaquin Valley, 

California

By J. ALAN BARTOW and KRISTIN McDOUGALL 

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1529-J

Revisions to the Tertiary stratigraphy 

of the area on the basis of geologic mapping 

and subsurface stratigraphic studies, including 

radiometric dating and paleontologic examination 

of well samples

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1984
UNITED STATES DEPARTMENT OF THE INTERIOR 

WILLIAM P. CLARK, Secretary

GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging in Publication Data

Bartow, John Alan

Tertiary stratigraphy of the southeastern San Joaquin Valley, California.

(Contributions to stratigraphy) (Geological Survey bulletin 1529-J)

Bibliography: p. 40-42

Supt. of Docs, no.: 119.3:1529^1

1. Geology, stratigraphic Tertiary. 2. Geology California San Joaquin River 

valley. I. McDougall, Kristin A. II. Title. HI. Series: Contributions to 

stratigraphy. IV. United States. Geological Survey. Bulletin 1529-J.

QE75.B9 no. 1529^1 557.3s 83-600239 

[QE691] [551.7'8'0979488]

For sale by the Superintendent of Documents, U. S. Government Printing Office 

Washington, D. C. 20402
CONTENTS

Page

Abstract ----- __-«____---___ __________-________ _ __ ji

 ______- _ _______ ______________________________.________________________ «______________ 2

*~~____ ____ ___-_______-_________~ ~ ~ 2

Walker Formation 5

Bealville Fanglomerate 12

Vedder Sand _____________________________________ 12

Jp^vpfct Sand and Freeman Silt ______________________ _ --___ 1 fi

Ilmon Basalt ____________________________________ 20

Olcese Sand ______________________________________ 20

Bena Gravel _____________________________________ 23

Fruitvale Shale of Miller and Bloom (1937) - - 32

"Santa Margarita" and Chanac Formations 32

Kern River Formation 34

Geochronology 34

^fjilkgi* Fomi&tion ___---____-_____ __________ _______ 35

Olcese Sand - ~ ._. . ~ 35

Round Mountain Silt 36

Summary 37

Discussion _________________________________________ 38

Basin history _____________________________________ 38

Distribution of coarse clastic material 38

References cited 40

ILLUSTRATIONS

Page

FIGURE 1. Index map of southeastern San Joaquin Valley, Calif, showing distribution of Tertiary strata J4

2. Correlation chart of Tertiary formations in southeastern San Joaquin

Valley 6

3. Diagrammatic cross section of Kern River area, showing stratigraphic 

relations of Tertiary formations north of Bakersfield arch and approximate position of age control 13

4. Diagrammatic cross section of Cottonwood Creek area, showing stratigraphic relations of Tertiary formations south of Bakersfield arch 

and approximate position of age control 21

5. Diagrammatic section of the Tejon Hills area, showing stratigraphic relations of Tertiary formations and approximate position of age contro\ _____________________________________ 22

6. Columnar section of lower part of the Bena Gravel south of Cottonwood

Creek, showing position of age control 24

in
CONTENTS 

TABLES

Page

TABLE 1. Summary of references to principal geologic names in the southeastern

San Joaquin Valley, California J3

2. Checklist of foraminifers from the Gulf "KCL-B" 45 well in sec. 22, T.

29 §_ R. 27 E ______________________________ 8

3. Checklist of foraminifers from the Shell Oil Co. [Seaboard Oil & Gas

Co.] "Fuhrman" 1 well in sec. 28, T. 28 S., R. 28 E. - 10

4. Checklist of foraminifers from the Chevron USA, Inc. [Standard of

California] 33-1 well in sec. 1, T. 29 S., R. 27 E. - 14

5. Checklist of foraminifers Chevron USA, Inc. [Standard Oil of California] 24-35 well in sec. 35, T. 29 S., R. 29 E. - ___ 17

6. Checklist of foraminifers from the Jim Riley [Standard Oil of California] "Jeppi-Camp" 67-8 well in sec. 8, T. 30 S.,T. 29 S., R. 29 E. - 29

7. Checklist of foraminifers from outcrops of Miocene strata in the southeastern San Joaquin Valley, California 30

8. Checklist of marine diatoms from outcrops of Miocene strata in the

southeastern San Joaquin Valley, California 31

9. Analytical data for K-Ar age determinations 36

10. Analytical data for fission-track age determinations 37
CONTRIBUTIONS TO STRATIGRAPHY

TERTIARY STRATIGRAPHY

OF THE SOUTHEASTERN 

SAN JOAQUIN VALLEY, CALIFORNIA

By J. ALAN BARTOW AND KRISTIN MCDOUGALL

ABSTRACT

New information derived from geologic mapping and subsurface stratigraphic 

studies, including radiometric dating of pyroclastic materials and paleontologic examination of well samples, has provided the basis for revisions to the Tertiary stratigraphy of 

the southeastern San Joaquin Valley. The units discussed in this report are: the Walker 

Formation (Eocene, Oligocene, and early Miocene), the Bealville Fanglomerate (late 

Oligocene and early Miocene), the Vedder Sand (Oligocene), the Jewett Sand (early 

Miocene), the Freeman Silt (early Miocene), the Ilmon Basalt (early? Miocene), the 01- 

cese Sand (early Miocene), the Bena Gravel (Miocene), the Round Mountain Silt (early? 

and middle Miocene), the Fruitvale Shale of Miller and Bloom (1937) (middle and late 

Miocene), the "Santa Margarita" Formation (late Miocene), the Chanac Formation (late 

Miocene), and the Kern River Formation (late Miocene, Pliocene, and early Pleistocene?).

The Walker Formation is the nonmarine equivalent of the "Famoso" sand (Eocene) 

and the Vedder Sand; south of the Bakersfield arch the upper part of the Walker is equivalent in age to the Jewett Sand and the lower part of the Freeman Silt. The Bealville 

Fanglomerate is a coarser equivalent of the Walker but not of the Bena Gravel, and is 

so redefined.

The Bena Gravel is redefined to include a paralic facies in addition to the previously 

recognized alluvial gravel; the unit is equivalent to the uppermost part of the Freeman 

Silt, the Olcese Sand, the Round Mountain Silt, and the Fruitvale Shale. The "Santa 

Margarita" Formation and the nonmarine Chanac Formation are parts of the same transgressive-regressive depositional sequence and are partial age equivalents. The nonmarine Kern River Formation is the youngest Tertiary unit and unconformably overlies 

older Tertiary strata. The names "Bealville Fanglomerate" and "Ilmon Basalt" are 

adopted herein.

The Tertiary strata of the southeastern San Joaquin Valley record a major transgression beginning in Eocene time and continuing into the Miocene, followed by a major 

regression beginning in the late Miocene and extending into the Pleistocene. The transgression was interrupted by relatively minor regressions at the end of Eocene time, near 

the end of Zemorrian time (earliest Miocene), at the end of Saucesian time (late early 

Miocene), and near the end of Luisian time (late middle Miocene). The regression was interrupted by two minor transgressions during late Miocene time.

The coarse clastic materials of the Bealville Fanglomerate, the Bena Gravel and Olcese Sand, the Chanac Formation, and the Kern River Formation are considered to be 

evidence of tectonic activity. The close association of the coarsest part of the Bealville 

with the Edison fault indicates that this fault was probably active during the late 

Oligocene and early Miocene. The difference in depositional histories for the areas north 

and south of the Bakersfield arch suggests that this arch was an important tectonic 

boundary, particularly during the middle Miocene and later.

Jl
J2 CONTRIBUTIONS TO STRATIGRAPHY

INTRODUCTION

Knowledge of the stratigraphy of the southeastern San Joaquin 

Valley has developed gradually over the period from the early 1900's 

to the present as the petroleum industry has explored new areas and 

deeper horizons in the southern San Joaquin basin. The stratigraphic 

names that generally were first used informally by petroleum 

geologists have come into common use, and most have been formally 

adopted. Table 1 summarizes the history of this stratigraphic nomenclature.

The biostratigraphy has developed hand in hand with the rockstratigraphic nomenclature, owing in part to the large Miocene molluscan fauna that has attracted paleontologists to the area since W. P. 

Blake, with the Pacific Railroad Survey, first collected fossils there in 

1853 (for a review, see Addicott, 1970).

The stratigraphy of the Miocene marine rocks of the area has 

evolved mostly as part of the larger picture of the Miocene of the west 

coast, and relatively little information dealing directly with the Tertiary stratigraphy of the southeastern San Joaquin Valley has been 

published. The literature concerning this area is almost entirely a byproduct of stratigraphic studies carried out in conjunction with petroleum exploration and development and thus is concerned primarily 

with the subsurface stratigraphy and structure.

The purpose of this report is to present new information about the 

stratigraphy of the southeastern San Joaquin Valley that has been obtained as part of a regional study aimed at providing an overview of 

Cenozoic tectonics through an understanding of sedimentary-basin development. A geologic map covering the area of this report (fig. 1) was 

published in preliminary form by Bartow and Doukas (1978); a revised, 

colored version with cross sections is in press. In this report, Bartow 

is responsible for interpretations of the stratigraphy based on observations during field mapping and subsurface studies since 1975, and 

McDougall is responsible for the biostratigraphy based on benthic 

foraminifers.

Acknowledgments. We thank the Atlantic Richfield Co., Chevron USA, Inc., and Texaco, Inc., for loaning us the well samples used 

in our paleontologic studies. We also thank the many other oil companies who provided copies of well logs and other well data that made 

our subsurface studies possible, and the California Well Sample Repository in Bakersfield, Calif., for their assistance in providing additional material for examination.

STRATIGRAPHY

Addicott (1970) included a discussion of the Tertiary rock-stratigraphic units in the area between the Kern River and Poso Creek in 

his report on the Miocene gastropods and biostratigraphy of the Kern
TABLE 1. Summary of references to principal geologic names in the southe

 

Formation Original reference 

______________________________________________ _____________

 

Kern River Formation- Anderson (1911) 

Etchegoin Formation Anderson (1905) 

"Santa Margarita" Formation2 Merriam (1916)^ 

Chanac Formation Merriam (1916) 

Fruitvale Shale of Miller and Bloom (1937) Miller and Bloom (1937) 

Bena Gravel Dibblee and Chesterman (1953

Round Mountain Silt - Diepenbrock (1933) 

Olcese Sand do 

Freeman Silt Kleinpell (1938) 

Jewett Sand Godde (1928) _ 

Pyramid Hill Sand Member - Wilson (1935) 

Vedder Sand Wilhelm and Saunders (1927) 

Walker Formation ___ do -- - - - 

Bealville Fanglomerate - - Dibblee and Chesterman (1953

________________________________________________________

Anderson (1905, p. 187-188, 191) applied the name "Kern River Beds" to M

below what was later named the Kern River Group. His description did not i

 ? 

First named for exposures near Santa Margarita in the Coast Range 75 km 

Quotation marks are used here to indicate that the name is probably misappl

Valley because of uncertainties of correlation with the type locality. 

^Original reference is Fairbanks (1904), but name was first used in south

(1916). 
J4 CONTRIBUTIONS TO STRATIGRAPHY

36°00'

118°30'

35°00'

10 20 30 40 KILOMETERS

CONTOUR INTERVAL 500 FEET

EXPLANATION

Surficial deposits (Quaternary)

Sedimentary rocks and semi consolidated deposits (lower Quaternary 

and upper Neogene)

Sedimentary and volcanic rocks 

(Tertiary)

Basement rocks (pre-Tertiary)

 |jv Oil field

Figure 3 | Section line for figures 3 

through 5

Well used in this study

Crestline of Bakersfield arch 

Approximately located

FIGURE 1. Index map of southeastern San Joaquin Valley, Calif., showing generalized 

distribution of outcrops of Tertiary strata, lines of section for figures 3 through 5, 

and geographic names used in text. Wells used for paleontologic study are: (1) Gulf 

Oil Co. "KCL-B" 45, (2) Chevron USA, Inc., 33-1, (3) SheU Oil Co. "Fuhrman" 1, 

(4) Jim Riley "Jeppi-Camp" 67-8, and (5) Chevron USA, Inc., 24-35. Letters denote 

principal oil fields: E, Edison; F, Fruitvale; G, Greeley; KR, Kern River; MP, Mount 

Poso; MV, Mountain View; RB, Rio Bravo; RM, Round Mountain. Base from U. S. 

Geological Survey l:500,000-scale California State Map, south half.
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J5

River area. The stratigraphy of that area will, therefore, not be discussed in detail here, except where new information or interpretations 

can be offered to supplement those provided by Addicott. Several formations, such as the Bealville Fanglomerate (herein adopted), the 

Bena Gravel, the Chanac Formation, and the Fruitvale Shale of Miller 

and Bloom (1937), that were not discussed by Addicott (1970) because 

they do not crop out in the Kern River area or have no bearing on the 

Miocene biostratigraphy are included here.

Stratigraphic relations of the Tertiary units of the southeastern 

San Joaquin Valley are shown diagrammatically in figure 2. The 

Bakersfield arch, a structural salient of Sierran basement rocks, the 

crest of which approximately coincides with the Kern River, seems to 

form a boundary between two areas in the southeastern San Joaquin 

Valley that have had significantly different histories. The sections 

north and south of the Bakersfield arch are, therefore, diagrammed 

separately in figure 2,

WALKER FORMATION

A section of nonmarine clayey sandstone, siltstone, and green 

claystone overlying basement rocks at the base of the Tertiary sequence in the southeastern San Joaquin Valley has traditionally been 

included within the Walker Formation. This formation was originally 

named by Wilhelm and Saunders (1927) from three wells in the Mount 

Poso oil field area, 24 km north of Bakersfield (fig. 1), one of which was 

subsequently designated (Addicott, 1970) the subsurface reference section for the Walker. A type section on Walker Basin Creek, about 27 

km east of Bakersfield, was designated by Dibblee and Chesterman 

(1953). North of the Bakersfield arch, the Walker is overlain by the 

Pyramid Hill Sand Member of the Jewett Sand; south of the arch, including the area of the type section, it is unconformably overlain by the 

Bena Gravel.

The Walker Formation crops out in a more or less continuous strip 

along the edge of basement outcrops from the Caliente Creek area 

northward to the White River, and generally does not extend more 

than 25 to 30 km westward in the subsurface. It is, however, probably 

continuous in the subsurface with the correlative Tecuya Formation of 

the San Emigdio Mountains at the south end of the San Joaquin Valley 

(south of area of fig. 1). The formation is about 550 m thick in the type 

section; it thickens southeastward to about 900 m and thins northward 

and westward, and is from 200 to 300 m thick in the Kern River area.

Although no age-diagnostic fossils have been found in the outcrops 

of the Walker Formation, in the Kern River area the upper part of the 

formation intertongues basinward with the Zemorrian Vedder Sand, 

and the lower part intertongues basinward with strata bearing Eocene 

("Domengine") brackish-water to marine mollusks. Benthic foraminif-
J6 CONTRIBUTIONS TO STRATIGRAPHY

A8e 

(in m.y.) SERIES STAGE NORTH OF 

BAKERSFIELD ARCH

SOUTH OF 

BAKERSFIELD ARCH

1.8

Holocene and 

Pleistocene

Pliocene

10 -

15 - Miocene

20-

24

25 -

Delmontian

\

\4

Mohnian \

Kern River Formation

HIATUS

Kern River 

Formation

r ^^ Formation "Santa

Warflarita-Foimatiqi _ _ __ . .

Fruitvale

Fruitv8le~M4J I I I I I I | Shale of 

Shale of MillirOJ I I Miller and 

and Bloom (1937) ^UjBloom (1937)- -

Saucesian Freeman Silt

30 -I

35- 

37

40-

Edison 

\Shale of 

Round ( Ka8ljne 

Mountain.? (1941)

~^=~ *Pyramid< 

Hill Sand Mbr.

Walker 

Formation

Walker 

Formation

Eocene (Unknown)

FIGURE 2. Correlation chart of Tertiary formations in southeastern San Joaquin Valley. 

Ages of series and stage boundaries are from (1) Van Couvering (1978); (2) Hardenbol and Berggren (1978); (3) Berggren and Van Couvering (1974); (4) Pierce (1970) 

and Barren (1976); (5) Turner (1970), adjusted for new decay and abundance constants for calculation of K-Ar ages (Steiger and Jager, 1977); and (6) Brabb and 

others (1977).
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J7

ers are also present in the marine equivalent of the Walker in subsurface sections north of Bakersfield (tables 2, 3). Such diagnostic species 

as Cassidulina laevigata, Elphidium minutum, Uvigerina cocoaensis 

species group, and Valvulineria cf. V. willapaensis indicate a Refugian 

(late Eocene) age. Stratigraphically higher assemblages are not age 

diagnostic but are composed of a distinctive inner-shelf assemblage; 

this assemblage is also recorded as present in the Vedder Sand to the 

west, where it is mixed with Zemorrian species. Benthic foraminifers 

from equivalent marine strata suggest an age of late Eocene to 

Oligocene for the Walker.

A K-Ar age of 21.4 m.y. from a tuff in the type section of the 

Walker Formation (discussed more fully below in the section entitled 

"Geochronology") indicates that the top of the Walker in the area south 

of the Bakersfield arch is within the lower Miocene. In the Kern River 

area, north of the arch, an unconformity between the Walker and the 

Jewett Sand of earliest Miocene age (fig. 2) precludes that the Walker 

of that area is Miocene. The total age range of the Walker, then, is late 

Eocene to early Miocene (fig. 2).

As Addicott (1970) pointed out, the lithology of arkosic sandstone, 

conglomerate, and minor green sandy claystone in the type section on 

Walker Basin Creek differs from that in the area northeast of 

Bakersfield, where green sandy claystone is the most conspicuous rock 

type. In either case, where the Walker Formation consists of white 

anauxite-bearing kaolinitic quartzose sandstone and kaolinitic claystone with scattered quartz grains, it bears a strong resemblance to 

the Eocene lone Formation in its type area 350 km to the northwest. 

Although long-range correlations based on lithologic resemblance are 

generally questionable, where the lithology may be related to climatic 

factors (such as a wet tropical or subtropical climate that would cause 

intense chemical weathering), there may be some validity to the correlation. A tuff bed in the Walker on the White River near the northern 

end of the Tertiary outcrop belt (fig. 1) is, unfortunately, too badly 

weathered to date or to correlate chemically. Its weathered condition 

and its close association with anauxite-bearing quartz-kaolinite 

sandstone suggests, however, that it may be Eocene.

A few wells drilled for oil in the Wasco-Famoso area, about 30 km 

northwest of Bakersfield, have penetrated a thick (300-500 m) section 

of probable nonmarine rocks below Eocene marine strata; this section 

has yielded pollen that suggest a Late Cretaceous (Maestrichtian) age. 1 

The upper part of this section is probably equivalent to the thin Walker 

Formation that occurs below marine strata of Eocene age in nearby 

areas, but most of the section should probably be considered a separate 

unit of Cretaceous age.

'Palynologic age of Mobil-Pan American Petroleum "KCL" 31-15 sidewall cores (R. L. Pierce, Mobil Oil Corp., 

Los Angeles, unpub. data, 1967). Courtesy of Mobil Oil Corp.
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J12 CONTRIBUTIONS TO STRATIGRAPHY 

BEALVILLE FANGLOMERATE

The Bealville Fanglomerate was first named and described by 

Dibblee and Chesterman (1953) as an unsorted boulder-conglomerate 

fades of both the Walker Formation and the Bena Gravel. More recent 

fieldwork, however, has demonstrated that whereas the Bealville intertongues westward with the lithologically similar but finer grained 

Walker, a clear lithologic distinction exists between the Bealville and 

the Bena. Both the Bealville and the Walker are characterized by their 

relatively common greenish-gray clayey matrix, whereas the matrix of 

the Bena Gravel is typically sandy, and gray to orange brown in color. 

Also, the sorting and rounding of clasts is better in the Bena than in 

the Bealville conglomerate beds.

The Bealville Fanglomerate, then, is an unsorted granitic rubble 

that unconformably overlies granitic basement and intertongues westward with the Walker Formation. It is unconformably overlain by the 

Bena Gravel.

The Bealville Fanglomerate is restricted to a relatively small area 

in the vicinity of Caliente Creek south of the Kern River, although 

lithologically similar rocks are present in the Tecuya Formation farther 

to the south (Nilson and others, 1973). At its type section south of 

Caliente Creek, the Bealville is more than 2,100 m thick (Dibblee and 

Chesterman, 1953).

Although the part of the Bealville Fanglomerate below the Bena 

Gravel was considered by Dibblee and Chesterman (1953) to be 

Oligocene, the upper part is presumably early Miocene because of the 

intertonguing between the Bealville and the tuff-bearing part of the 

Walker Formation and because of the occurrence of what may be the 

same tuff in the Bealville. The name "Bealville Fanglomerate" is here 

adopted as defined above; its age is regarded as late Oligocene and 

early Miocene.

VEDDER SAND

The Vedder Sand is principally a subsurface unit that is widespread in the southeastern San Joaquin Valley (Richardson, 1966) and 

may reach a thickness of more than 300 m locally. It crops out in a narrow belt north of Poso Creek, where it is composed principally of lightgray well-sorted fine- to medium-grained sandstone, locally cemented 

with silica. The thickness in outcrop ranges from 0 to about 80 m. It 

conformably overlies the Walker Formation and in the subsurface is 

the lateral equivalent of the upper part of the Walker (fig. 3). The Vedder is unconformably overlain by the Jewett Sand (or the undivided 

Freeman-Jewett silt of some authors) along the east margin of the 

basin, north of the Bakersfield arch, but south of the Bakersfield arch 

and farther west in the deeper parts of the basin they may be conformable.
WEST 

Mf2953 Fossil locality

Marine diatoms 

A Foraminifers 

<B Mollusks

Stage bou

approxim

Formationa

Unconform

FIGURE 3. Diagrammatic cross section of Kern River area, showing stratigraphic relations of T

north of Bakersfield arch and approximate position of age control. Not to scale, althou

boundaries are in correct positions relative to formational boundaries. Numbered vertical 

(see fig. 1) from which samples were studied, projected into line of section.
J14 CONTRIBUTIONS TO STRATIGRAPHY 

TABLE 4. Checklist of foraminifers from the Chevron USA, Inc.

[A, abundant (more than 50 specimens); C, common (21-50 specimens); F, few (2-20

FORMATION

SERIES

STAGE

DEPTH 

SPECIES (FT)

Nonionella costifera (Cushman) 

Valvulineria spp . 

Bulimlnella subfuaiformia Cushman 

Valvulineria ornata Cuahman 

Baggina californica Cushman 

SiDhogenerina transversa Cushman 

Bolivina marginata Cushman 

Lenticulina simplex (d'Orbigny) 

Stilostomella adolphina (d'Orbigny) 

Bolivina imbricata Cushman 

Epiatominella aubperuviana Cushman 

Trifarina oocidentalia (Cuahman) 

Dorothia ap. 

Marginulina beali (Cuahman) 

Caasidulina laevigata d'Orbigny 

Hanzawaia crassiaeptus (Cushman 4 Laiming) 

Hanzauaia relizenais (Kleinpell) 

Lenticulina convergens (Bornemann) 

Bolivina advena Cushman 

Nonionella inciaa (Cuahman) 

Quinqueloculina cf. Q. goodspeedi Hanna & 

Hanna 

Bolivina spp. 

Anomalina glabrata Cuahman 

Lenticulina app. 

Valvulineria miocenica Cushman 

Buliminella curta Cushman 

Melonia oompilioidea (Fitchel 5 Moll) 

Fursenkoina ap. 

Praeglobobulimina ovata (d'Orbigny) 

Robertina sp. 

Cancria ap. 

Epistominella pacifica (Cuahman) 

Hanzawaia illingi (Nuttall) 

Pyrgo 3p. 

Casaidulinoides oalifornienais Bramlette 

Cibicidea floridanua (Cuahman) 

Troonammina ap. 

Cancpia aagra (d'Orbigny) 

Bulimina inflata alligata Cuanman 4 Laiming 

Ho«glundina elegana d'Orbigny 

Darby el la ap. 

Uenticulina smileyi (Kleinpell) 

Spiroplectammina tejonenaia Mallory 

Dentalina sp. 

Lenticulina miocenica (Chapman) 

Sphaeroidina bulloides d'Orbigny 

neophax pilulifera Brady 

Ammodiacua incertua (d'Orbigny) 

Gaudryina tnangularls Cuahman 

Hap lophragrao idea sp. 

TntaxiUna colei Cushman 4 Siegfus 

of 

Miller and Bloom (1937)

Illlllllll

Olcc 

Round Mountain Silt 

Sa

M 1 o c n 

Lul s 1 a n

00 0

F F F F F 

F F F F F C F -- 

F - F -- F F 

F -- ~ 

 _ F F R F 

 R R R F R F 

_----- A F F C C F C F F 

 R R 

 R R R -- F F F 

-- .- R 

 R R F F 

__ __ __ __ __ __ __ __ __ _ R _ __ __ 

 R 

 _ R

8«

fid

RollI ian

D <\l =r 

F F F

F F F 

 -- F

A A F

F F F 

p

R F 

 F 

F F F 

F R

-- F

 F 

 F F 

 F 

 R 

.. -. F
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J15

[Standard Oil of California], 33-1 well in sec. 1, T. 29 S., R. 27 E.

specimens), B, p

Olcese Ssnd Freemsn silt

Rio Bravo 

sand Vedder Sand

R e IIz la n

o o o o *o to o ru

 __ [ 

R R 

 -- R F

 R 

R _- 

Seuceslan

1 ! 1 1 ! 1 1 1 ! ! f ! ! ! ! 1 ! 1 !

-- -_ _- -. R 

.. .. R .. .. .. 

F F F F R F -------- -- 

FFF

ppOppppQ

-- -- R -- -- F F -- F R -- F

F B F F F B

F

/ Zemorrlan

S g

 R 

R

 R .- F F

 B 

R

F R 

F F F R - F F F F F F F F F 

R FB FF

FRR FF FFF F

F B

 -- -- -- -- S
J16 CONTRIBUTIONS TO STRATIGRAPHY

the nonmarine Walker Formation. Farther west in the deeper parts of 

the basin, common to abundant specimens of Sipkogenerina nodifera 

appear in the faunas and restrict these assemblages to the late Zemorrian Stage of Kleinpell (1938).

JEWETT SAND AND FREEMAN SILT

The Jewett Sand is a unit of silty sand to sandy shale that overlies 

the Vedder Sand or the Walker Formation, and the Freeman Silt is a 

siltstone unit that gradationally overlies or intertongues with the 

Jewett and intertongues with the overlying Olcese Sand (Addicott, 

1970). The Pyramid Hill Sand of Wilson (1935), formerly considered a 

separate formation, was reduced in rank by Addicott (1970) to a member (the Pyramid Hill Sand Member) of the Jewett Sand. The composite thickness of the two units is about 300 m in the Kern River area.

Basinward from the vicinity of the Round Mountain oil field (fig. 

1), where the Jewett Sand and the Pyramid Hill Sand Member are best 

developed (Park and others, 1963, pi. 6), the Jewett Sand thins by 

facies change to siltstone, and the Freeman Silt correspondingly thickens. In subsurface work, where the Jewett Sand is thin or absent, the 

interval between the Olcese Sand (or the Round Mountain Silt where 

the Olcese is absent) and the Vedder Sand is commonly referred to as 

the Freeman-Jewett Silt (of local usage). We prefer, however, to restrict the name "Jewett" to the sandstone facies, and use the name 

"Freeman" for all of the siltstone facies (fig. 3).

Although the Freeman Silt and the Jewett Sand can ordinarily be 

differentiated in subsurface correlations on the basis of their electriclog character, the two formations are generally difficult or impossible 

to differentiate in outcrop because of the fine-grained texture of the 

Jewett Sand. Toward the north end of the Tertiary outcrop belt (fig. 

1), the Freeman Silt becomes thinner and sandier, and consistent differentiation of the Freeman from the overlying Olcese Sand and the 

underlying Jewett Sand becomes nearly impossible. Neither the 

Freeman Silt nor the Jewett Sand crops out south of the Kern River, 

although both units or equivalent strata are present in the subsurface 

at the south end of the valley.

The basal part of the Pyramid Hill Sand Member of the Jewett 

Sand is a fossiliferous calcareous pebbly sandstone, informally called 

the grit zone, that unconformably overlies the Walker Formation or 

the Vedder Sand. The contact is locally channeled, and a slight angular 

discordance is evident. Basinward, particularly in the vicinity of the 

Rio Bravo and Greeley oil fields (fig. 1), this basal grit zone occurs in 

the Rio Bravo sand, an informal unit that is the local equivalent of 

the Pyramid Hill Sand Member. The relations of the Rio Bravo sand to 

the underlying Vedder Sand are uncertain. The data of Bandy and 

Arnal (1969, fig. 2, table 5) imply continuous deep-water sedimentation 

across the contact, but the presence of shallow-water mollusks (mostly
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J17

TABLE 5. Checklist offoraminifersfrom Chevron USA, Inc. [Standard Oil of California], 2^-35 well in sec. 35, T. 29 S., R. 29 E.

CA, abundant (more than 50 specimens); C, common (21-50 specimens); F, few_(2-20 specimens); R, rare (1 specimen). 

Depths shown are those given on ditch samples]

FORMATION

SERIES

STAGE

Qpprico DEPTH oPECIES (pi)

Bulimella curta Cushman 

Valvulinepia oalifornioa Cushman 

Gyroidina rosaformis (Cushman & Kleinpell) 

Gyroidina soldanii d'Opbigny 

Uvigepina spp. 

Pullenia mlooenioa Kleinpell 

Anomalina salinasensis Kleinpell 

Valvulineria spp . 

Haplo hpagmoides sp. 

Boliv na SD. 

Uvige inella obesa Cushman 

?Boli ina floridana Cushman 

Valvu ineria ornata Cushman 

Anoma ina glabrata Cushman T 

Boliv na imbpicata Cushman 

Bulim nella subfusiformis Cushman 

Boliv na advena Cushman 

Nonionella miocenica Cushman 

Dentallna sp. 

Nonionella oostifepa (Cushman) 

Nonionella inoisa (Cushman) 

Quinqueloculina of. Q. goodspeedi Hanna &

Bolivina mapginata Cushman 

Bolivin tumida Cushman 

Praeglo obulimina gupoides (d'Opbigny) 

Epistom nella subperuviana Cushman 

Marti.no ;iella patens Cushman & Kleinpell 

Cyclamm na gacifioa Beck 

Fupsenk ina hobsoni (Beck) 

Cassidu inoides oalifopniensis Bramlette 

Nodosap a longisoata d'Orbigny 

Cibicid s fietchepi Galloway & Wissler 

?EggePe la subconica Papp 

"Santa Margarita* 

"' Formation Edison Shale of Kasline (1941)

?

o °

L u i s i a n (Relizian not differentiated)

ocoooooooooooooooooooo

R R -_ R -- R

 R R F

 _ F R R R ~

 -- R _ -- R 

 -- R _. -- 

 _ -- R 

 H 

 -- _ R 

oysters) in the Rio Bravo sand suggests very shallow water conditions 

during its deposition. Although the presence of an unconformity at the 

Rio Bravo-Vedder contact, like that at the Pyramid Hill-Walker contact, cannot be demonstrated, the marked shallowing of the San Joaquin basin indicated by the presence of the Rio Bravo sand suggests 

that an unconformity could be present locally.

Both the Jewett Sand and the Freeman Silt were considered to be 

lower Saucesian (Ferguson, 1943; Beck, 1952; Rudel, 1965). Although
J18 CONTRIBUTIONS TO STRATIGRAPHY 

TABLE 5. Checklist offoraminifers from Chevron USA, Inc. [Standard

FORMATION

SERIES

STAGE

SPECIES D(EFPTT,H

Anomalina salinasensis Kleinpell 

Uvigerinella obesa Cushman 

Valvulineria ornata Cushman 

Uvigerinella spp. 

Anomalina glabrata Cushman 

Nonionella inoisa (Cushman) 

Praeglobobulimina pupoides (d'Orbigny) 

Epistominella subperuiriana Cushman 

Cibioides ap. 

Lentioulina ma^i (Cushman & Parker) 

Fursenkoina hobsoni (Beck) 

Buliminella elegantlssima (d'Orbigny) 

Cibioides fletoheri Galloway & Wissler 

Textularia sp. 

Edison Shale of Kasline (1941)

Miocene

L u i s i a n (Relizian not differentiated)

£8S8S8Sg § 8§8£88SgSi§S8§£

cncncnmcnwmcnmcnmcncncncnmcncncn^m^a-a-

 R .. ._ _. 

 R F 

 R R .. .. _. 

 -_ -- R -- -. .. _- .- __ __ __ __

 R _ R _.

R

the lower part of the Jewett Sand in outcrop is a shallow-water facies 

that does not carry a diagnostic foraminiferal fauna, the equivalent 

deeper water facies farther west in the subsurface is Zemorrian. The 

presence of diagnostic Zemorrian benthic foraminifers, including 

Bulimina carnerosensis, Cibicides floridanus, and the lowest occurrences of Siphogenerina mayi and Uvigerinella obesa impolita (tables 

2-6), indicate that the Zemorrian-Saucesian boundary occurs within the 

lower part of the Freeman Silt and that the unconformity at the base 

of the Pyramid Hill Sand Member may be at or very close to the 

Oligocene-Miocene boundary (fig. 2).
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J19 

Oil of California], 24-35 well in sec. 35, T.29S.,R. 29 E. Continued

Edison Shale of 

(( lift* (1841)

Olcese(?) 

Sand Freeman Silt Jewett Sand Vedder Sand

% .

£ e

« IL

Miocene O M g o c e n e

L u 1 s i a n (Relizlan 

not differentiated)

§

000000000 ^rcooa-cooa-coo

 FFRF--FFRR

 R 

 R R F R R -- F 

-- R -- - F - - -

~

Saucesian

o o o o o

 F 

 F F F

F R F

F F 

?

Zemorrian

on zr t- co ^r LA *o

-- R R R 

F R

R F F F ~ R R R 

F R R R R ~ ~ ~ 

F F F F F F ~ F ~ -- 

F - _- - _ _ - - - - - - - - - - - - - -

R R

R -- 

R -- -- - - - - - - - - - - - - - - - - - - -

F

 R ~ 

Saucesian benthic foraminifers are common throughout most of the 

Freeman Silt in subsurface sections. Characteristic of these assemblages are Bulimina inflata alligata, Dentalina quadrulata, Hanzawaia crassiseptus, Plectofrondicularia califomica, Siphogenerina 

transversa, Uvigerinella obesa, and U. obesa impolita (tables 2-7). 

Both Saucesian and Zemorrian assemblages indicate that the Freeman 

Silt was deposited in deep water, probably at lower middle bathyal 

depths (1,500-2,000 m).

In most subsurface sections the Saucesian assemblages appear to 

end abruptly because of the influx of transported shelf species, or in
J20 CONTRIBUTIONS TO STRATIGRAPHY

some places because of sample gaps. Farther west in the deepest part 

of the basin, diagnostic Saucesian benthic foraminifers disappear below 

the Freeman-Round Mountain Silt contact, and long-ranging Miocene 

species and transported shelf species appear that are most commonly 

associated with the middle and late Miocene (table 2). Although distinctly Relizian or younger species have not been identified in the uppermost part of the Freeman Silt, this interval is probably Relizian 

(fig. 2). The Freeman Silt, then, is early Miocene. On the basis of new 

evidence for a late Zemorrian-early Saucesian age of the Jewett Sand 

and the lower part of the Freeman Silt, and on the early Miocene age 

of the upper part of the Walker Formation reported here, we infer that 

the Jewett and the lower part of the Freeman are equivalent to the 

upper part of the Walker Formation south of the Bakersfield arch, 

even though the Jewett unconformably overlies the Walker in the Kern 

River area to the north of the arch (fig. 2).

ILMON BASALT

The Ilmon Basalt is a thin flow unit that lies above the Walker 

Formation and below the Bena Gravel in the vicinity of Caliente Creek. 

Dibblee and Chesterman (1953), who first named and described the 

unit, believed that the Ilmon and the Walker were conformable. However, although the two formations are apparently concordant, more 

probably there was a hiatus, however small, between the deposition of 

the Walker Formation and the time when the basalt flowed over its 

surface. The Ilmon is unconformably overlain by the Bena Gravel, as 

evidenced by its limited and discontinuous distribution.

The name "Ilmon Basalt" is here adopted as redefined above; 

lower Walker Basin Creek at its confluence with Caliente Canyon is 

designated as the type locality. Although the age and source of the 

Ilmon are not known, the unit is presumably early Miocene on the basis 

of its stratigraphic position (fig. 2) and may correlate with Miocene 

basalts northeast of Tehachapi.

OLCESE SAND

The Olcese Sand was defined by Ferguson (1941), although the 

name was first used by Diepenbrock (1933). The unit is dominantly a 

sandstone, with some interbedded siltstone and local pebbly sandstone 

or conglomerate. It reaches a thickness of 300 to 360 m in the vicinity 

of the Round Mountain oil field, which is its type area. In outcrop, the 

middle part is probably nonmarine, although the upper and lower parts 

are marine and abundantly fossiliferous in some areas (Addicott, 1970); 

farther basinward, the Olcese is wholly marine. Abrupt changes in 

benthic-foraminiferal faunas suggest an unconformity within the Olcese 

and near the Saucesian-Relizian boundary. The unit intertongues 

basinward with the underlying Freeman Silt and the overlying Round
SOUTHWEST 

FIGURE 4. Diagrammatic cross section of Cottonwood Creek area, showing stratigraphic relat

Bakersfield arch and approximate position of age control. Not to scale, but biostratigraphic bo

tive to formational boundaries. Numbered vertical lines (see fig. 1) indicate wells from which sa
WEST 

Marine siltstone 

and sandstone

Fruitvalel?) Shale of 

Miller and Bloom 

(1937)

Fossil locality 

Marine diatoms 

Foraminifers

Stage boundary-Ap

ly located

Formational contac

Intraformational co

Unconformity

FIGURE 5. Diagrammatic cross section of Tejon Hills area, showing stratigraphic relations of Tertiary f

and approximate position of age control. Not to scale, but biostratigraphic boundaries are inferred to 

rect positions relative to formational boundaries.
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J23

an age of Relizian or Luisian. Appearance of the assemblage including 

M. beali in the upper part of the Freeman Silt farther west implies lateral equivalency of the two formations. Although a Relizian fauna is 

not well represented in the Olcese, this formation is here considered 

Saucesian and Relizian, that is, early Miocene (fig. 2).

Addicott (1970, p. 18) described a crossbedded sandstone containing abundant pumice grains and pebbles that occurs near the middle of 

the unit. This pumiceous sandstone, first observed by W. P. Blake in 

1853, provides a marker bed to which the fossils that he collected in 

Ocoya (Poso) Creek can be related (Blake, 1857, p. 167; pi. 1, sec. 3). 

It can be traced northward to where it is overlapped by the Kern River 

Formation. Pumice pebbles from this sandstone have been dated by KAr and fission-track methods, and the best age is considered to be 15.5 

m.y. These results, which place the pumice bed near the Saucesian-Relizian boundary, are discussed more fully in the section below entitled 

"Geochronology."

BENA GRAVEL

The Bena Gravel was originally defined as "* * * a series of terrestrial gravels of lower and middle Miocene age lying conformably 

above the Walker formation and Union basalt and unconformably below 

the Kern River gravels in lower Caliente Canyon" (Dibblee and Chesterman, 1953, p. 38). In the vicinity of Cottonwood Creek, several 

kilometers northwest of the Caliente Canyon area, Dibblee and Chesterman (1953, p. 38) reported the presence of a thin unit consisting of 

thin-bedded punky shale containing laminae of silty sand. This unit, 

which they called the Freeman-Jewett Shale, was believed to occur 

conformably between the Bena Gravel and the Walker Formation. A 

later map (Dibblee and others, 1965) covering the Cottonwood Creek 

area shows the Freeman Silt, the Olcese Sand, and the Round Mountain Silt between the Bena and the Walker and intertonguing at the top 

with the Bena.

The heterogeneous lithology of the sequence between the Bena 

Gravel (as originally defined by Dibblee and Chesterman, 1953) and the 

Walker Formation, which consists of coarse sandstone and conglomerate closely associated with laminated claystone and siltstone, diverges 

from the typical lithologies of the Freeman Silt, the Olcese Sand, and 

the Round Mountain Silt in the area north of the Kern River. This sequence contains plant material in places, and it contains freshwater 

diatoms in a claystone at the base that was mapped as the Freeman 

Silt by Dibblee and others (1965). There are also rare occurrences of 

oysters and barnacles (Hackel, 1965, p. 29), marine-mammal bones, 

diatoms, and foraminifers (figs. 4, 6). The conglomerate interbeds are 

lithologically identical to the nonmarine Bena Gravel, and much of the 

sandstone, siltstone, and claystone occurs in fining-upward sequences 

a few meters thick, including at least one fossil soil (measured section 

unit 21), that are best interpreted as fluvial cycles. The whole sequence
J24 CONTRIBUTIONS TO STRATIGRAPHY

SCALE 

(meters)

200- 

150- 

100- 

50-

0-

LITHOLOGY

=_-z_-^_r^^_-^

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I- ^^^^vf=:

FOSSILS, 

LOCALITY 

NUMBER

<P

A Mf2993

:* Mf2997

DIBBLEE 

AND 

OTHERS 

(1965)

Mountain Silt Round 

m

?!

» 9

"o

c75

(D 

0)

£ LiVolcanic 

flows

 / 

Walker Formation

THIS 

REPORT

I ve

(Paralic facies)

G ar

(Alluvial-fan facies)

(D

c -

0>

ffi

"m 

.$ 

u

5 

_o

1

(D 

Q.

llmon 

Basalt

Walker Formation

DESCRIPTION

Siltstone and claystone, laminated, with thin to very thin 

interbeds of medium- to 

coarse-grained sandstone. 

Abundance of sandstone 

beds decreases upward. 

Contains marine-mammal 

bones of middle Miocene 

age.

Pebble -cobble conglomerate, 

sandy, massive, locally 

containing large rounded 

clasts of laminated white 

claystone or siltstone, with 

interbeds of massive 

coarse-grained sandstone.

Shale, silty, laminated, buff to 

light- brown, containing 

foraminifers of Luisian 

(middle Miocene) age.

/Conglomerate, massive, with\ 

' sandstone interbeds (as 

above).

/Sandstone, friable, massiveA 

medium- to very coarse 

grained, with interbeds of 

interlaminated siltstone, 

claystone, and fine-grained 

sandstone.

'Sandstone, friable, massive,N 

coarse-grained to very 

coarse grained, light-gray to 

pale-orange, slightly clayey.

/Claystone, diatomaceous, silty,N 

pale-olive. Freshwater.

\ icular. /

Sandstone, clayey, palegreenish-gray, and sandy 

claystone.

Pumiceous vitric tuff, 21.4 m.y.

FIGURE 6. Columnar section of lower part of the Bena Gravel south of Cottonwood 

Creek, showing position of age control.
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J25

MEASURED SECTION OF THE 

PARALIC FACIES OF THE BEN A GRAVEL

[From roadcuts along Breckenridge Road in sec. 16, T. 29 S., R. 30 E., Mount Diablo base and meridian]

Thickness 

(m)

Bena Gravel (part):

42. Claystone and silty claystone, laminated, light-olive-gray, containing

common gypsum veins. Higher beds not exposed 7.0+

41. Sandstone, pebbly, coarse-grained to very coarse grained, massive, including thin sandy pebble-conglomerate lens near base, and concentration of dense laminated limestone boulders in upper part. Scour

SUl*fflCG Jit t)£LS6 __ .» . __ - _ _ .«_ . _ _ _ ,.*... «__.__^__«t»_ Q A

40. Claystone, silty, pale-olive; sandy in lower part 1.0

39. Sandstone, pebbly, medium- to coarse-grained and coarse-grained to

very coarse grained, friable, yellowish-gray; contains large-scale

crossbedding locally. Fines upward to fine- to medium-grained

clayey sandstone and grades into overlying unit; scour surface at

KQIJA . _____________ ___ ________ _ _ _______________ ____ ______________ . 1ft 0 ILPCtOC iV.V

38. Claystone, sandy claystone, and clayey fine-grained to very fine

grained sandstone; pale-olive to yellowish-gray 6.5

37. Sandstone, pebbly, coarse-grained to very coarse grained friable;

grades upward into medium to coarse sand. Poorly exposed 6.0?

36. Sandstone, calcareous, coarse-grained to very coarse grained pebbly, 

and medium- to coarse-grained; large-scale crossbedding locally includes pebble-conglomerate lens near middle of unit; scour surface at

________ 12.0

35. Sandstone and siltstone, very fine grained, clayey, laminated, paleolive (locally stained dark yellowish orange); grades upward into silty

________ , _____ M ________________________________ ,. . __ ., __ . _____ __. _____ - 1.0

34. Sandstone, pebbly, coarse-grained to very coarse grained, including 

thin interbeds of medium- to coarse-grained sandstone, and laminated siltstone with calcareous concretions 1.5

33. Pebble conglomerate, friable, with coarse-grained sandstone matrix;

fines upward and grades into overlying unit 3.5 

Covered interval

32. Siltstone and silty sandstone, laminated, grayish-orange and pale-yellowish-brown, with thin interbeds of light-gray to light-olive claystone and thin lenses of medium-grained sandstone; weathers to very 

fissile shale. Claystone contains fish remains and marine diatoms - 4.0+

31. Sandstone and conglomerate, with clasts of laminated white claystone

in sandstone. Poorly exposed 2.0 

Fault and covered interval

30. Conglomerate, sandy, containing rounded pebbles and cobbles, with a 

few boulders of laminated white claystone near base. Fills channels 

in underlying unit 3.5 +

29. Sandstone, coarse-grained, friable, containing abundant claystone pebbles throughout and laminated white claystone boulders at top 1.8

28. Conglomerate, sandy, containing rounded pebbles and cobbles; crudely

bedded, with thin interbeds of pebbly sandstone 2.7

27. Sandstone, thin- to medium-bedded, friable, light-gray to yellowishorange; grain sizes range from fine to very coarse and pebbly 5.0

26. Conglomerate, sandy, massive, dark-yellowish-orange, containing 

rounded pebbles and cobbles; scour surface at base with a few centimeters of relief 3.0
J26 CONTRIBUTIONS TO STRATIGRAPHY

MEASURED SECTION OF THE 

PARALIC FAC IBS OF THE BEN A GRA VtfZ^-Continued

Thickness 

(m)

25. Interlaminated siltstone, claystone, and fine-grained sandstone, lightgray to grayish-yellow 0.3

24. Sandstone, coarse-grained to very coarse grained, friable, light-gray; 

poorly sorted grayish-orange conglomeratic sandstone at base; Contains large isolated clasts of laminated siltstone and poorly sorted 

conglomerate bed near base; includes eroded and truncated interbeds 

of interlaminated claystone, siltstone, and very fine grained 

sandstone in lower part, with scattered small claystone clasts in

iTTVrwi-f* naff - _ .___ __ ____ - __ _ __ 1 7 ft x^x"^ r** *

23. Sandstone, pebbly, clayey, pale-olive; contains clasts of very clayey 

greenish-gray sandstone at base. Fines upward to clayey finegrained to very fine grained sandstone at top 2.7

22. Claystone, pale-greenish-yellow to grayish-yellow; becomes silty to

ssndv T1G3J* too _______ __ __ ..... __ ._._ __ ..... _______ _..__ i ^

21. Eroded fossil soil, sandy, yellowish-gray to dusky-yellow in lower part, 

mottled-yellowish-orange toward top, and dark-yellowish-orange in 

upper few centimeters; clay content increases upward. Contains 

root(?) molds throughout; mostly massive but blocky structure in 

UDoer 30 cm _____________________________ 1 5

20. Sandstone, pebbly, medium- to coarse-grained, grayish-orange; becomes clayey in upper part. Fills erosional relief of 20 to 30 cm on underlvincr unit ______________________ _________ 3 6

19. Claystone, light-grayish-olive; becomes sandy upward and grades into

pale-olive sandy claystone to clayey very fine grained sandstone 3.0 

Fault

18. Sandstone, clayey, very fine grained 1.0 +

17. Conglomerate, containing rounded pebbles and cobbles, with coarsegrained sandstone matrix 2.8 

Fault

16. Conglomerate (as above), containing large white claystone boulders at

Vjjjg£« fiTiAs UT^wsu*fi __ ... . .____..._. ____ ..... ______ ... _____ __ __._.., ______ ..... ____ 2.0

15. Sandstone, pebbly, coarse-grained to very coarse grained, very pale

/YPQTioro f-j-v QTQTriaVi rM*sififro _ .. ..... _ _ ...... __ ..... 1 ft 4- \J1 AilgC -W g.1 rtJlOli L/l ClllgC . i» V T^

Fault and covered interval

14. Pebble conglomerate, sandy, crudely stratified; contains scattered

large cobbles 3.0 + 

13. Sandstone, coarse-grained to very coarse grained, friable, massive, 

light-gray to very-pale-orange; includes thin bands of pebbles and 

cobbles ______________ ____________________ 3 . 0 

12. Claystone, silty, pale-olive 1.5 

Fault

11. Sandstone, pebbly, grading upward into sandy conglomerate; fills channels in underlying sandstone 5.5 

10. Sandstone, clayey, very fine grained 1.0 + 

Fault

9. Pebble conglomerate, sandy, light-gray to pale-orange, crudely

8. Sandstone, very coarse grained, pebbly, friable, massive, light-gray - 4.5 

7. Sandstone, medium-grained, massive, very pale orange; contains pebble- and cobble-sized clasts of siltstone and claystone 1.5 

6. Conglomerate, sandy, massive, poorly sorted, light-gray to very pale

__________ - __ ___ - __ ___ __ * - ___ _ *" 2 0
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J27

MEASURED SECTION OF THE 

PARALIC FACIES OF THE BENA GRAVEL-Contiraied

Thickness 

(m)

Fault

5. Interlaminated siltstone and very fine grained sandstone, pale-olive to

yellowish-gray 1.0 

4. Sandstone, medium- to coarse-grained, light-gray; grades upward into

3. Pebble conglomerate; contains boulders of dense pale-olive limestone

\int'li SC3,tt61*6Q T^^bblfiS ______________________ -. .-. 1 5J

2. Sandstone, coarse-grained to very coarse grained, massive, pale-yellowish-orange; contains scattered pebbles, and pebble- to bouldersize clasts of pale-olive siltstone. Grades upward into sandy pebble

f*(\Y\cr\r\'tY\£*wti'£* __ _ - _ _______ fi ft l^Uilgll/Illd. OrLC V/« V

Fault

1. Claystone, laminated, light- through grayish-olive to locally dark gray, 

includes few very thin interbeds of very fine grained yellowish-gray 

calcareous sandstone near top and a thin dense microcrystalline

C*L at trvn v\j£t _ _ . _ ____ «. _ «.« _ **»\s 2 0

GXDOSGC! thiclcriGSS __ --- _ _ -- ___ --- _ . _________ _ 162 2 4

between the Bena Gravel (of Dibblee and Chesterman, 1953) and the 

Walker Formation probably represents a complex of freshwater, 

brackish-water, and marine environments equivalent to the deeper 

water marine facies represented by the uppermost part of the 

Freeman Silt, the Olcese Sand, the Round Mountain Silt, and the 

Fruitvale Shale of Miller and Bloom (1937) in the deeper parts of the 

basin. Because of the intertonguing of this sequence with the Bena 

Gravel at the top and the inclusion of conglomerate interbeds or lenses 

lithologically identical to the Bena throughout, we here include this sequence within the Bena Gravel as a paralic facies distinct from both the 

alluvial-fan facies characteristic of the remainder of the Bena and the 

fully marine facies to the southwest.

The Bena Gravel changes facies within a short distance northward 

into the Olcese Sand and the Round Mountain Silt, and southwestward 

into the Edison Shale of Kasline (1941) (fig. 4). The Edison Shale, 

which is recognized in the subsurface of the Edison oil field (fig. 1) a 

few kilometers southwest of outcrops of the Bena, probably represents 

a transitional facies between the Bena and the normal marine facies 

(Round Mountain Silt and the Fruitvale Shale of Miller and Bloom, 

1937).

The absence of the Freeman Silt and the Jewett Sand in outcrops 

south of the Kern River, where the Olcese Sand rests directly on the 

Walker Formation (Dibblee and others, 1965; Bartow, 1981), strongly
J28 CONTRIBUTIONS TO STRATIGRAPHY

suggests that, despite the statement of Dibblee and Chesterman (1953) 

to the contrary, an unconformity exists between the Bena Gravel and 

the underlying Walker Formation or Ilmon Basalt. The presence of 

this unconformity is supported by the strong lithologic contrast between the Bena Gravel and the Walker Formation (as discussed above) 

where the two formations are in contact.

The Bena Gravel is restricted to the area south of the Kern River 

and is about 760 m thick at the type locality south of Caliente Creek 

(Dibblee and Chesterman, 1953). In the vicinity of Cottonwood Creek, 

about 750 m of nonmarine conglomerate and sandstone overlies more 

than 200 m of the paralic facies.

Nonmarine sandstone, conglomerate, and mudstone unconformably below the "Santa Margarita" or Chanac Formation in the Tejon 

Hills were included within the Bena Gravel by Dibblee and Warne 

(1970), although these strata were originally mapped as the Santa Margarita Formation by Hoots (1930). These rocks, as much as 250 m 

thick, are lithologicaily similar to the type Bena Gravel but are equivalent to only the upper, late Miocene part (fig. 5).

Age diagnostic fossils have been found at a few localities in the 

Bena Gravel. The paralic facies in the area between Cottonwood Creek 

and Caliente Creek has yielded foraminifers of Luisian age and seal 

bones2 (figs. 4 and 6). Marine diatoms of middle Miocene age (table 8) 

were found in the measured section of the paralic facies (unit 32).

The Bena Gravel in the Tejon Hills contains nonmarine mammals 

of Savage's (1955) Cerrotejonian Stage (early Clarendonian Pate 

Miocene]). The Bena conformably overlies a marine sandstone containing a tongue of the Mohnian Fruitvale Shale of Miller and Bloom 

(1937), and unconformably underlies the "Santa Margarita" Formation 

containing a late Miocene molluscan fauna (fig. 5). The age of the Bena, 

then, is late early Miocene(?), middle Miocene, and late Miocene.

ROUND MOUNTAIN SILT

Diepenbrock (1933) first used the name "Round Mountain Silt" for 

an interval of diatomite, siltstone, and sandstone in a well in the Mount 

Poso area. Its boundaries were redefined by Addicott (1970) to make 

them more consistent with current usage. The unit conformably overlies the Olcese Sand and is unconformably overlain by the "Santa Margarita" or Chanac Formation in the Kern River area (fig. 3). In the 

subsurface to the west, the Round Mountain Silt, generally 120 to 180 

m thick, is conformably overlain by the Fruitvale Shale of Miller and 

Bloom (1937). The Round Mountain reaches a thickness of more than 

400 m locally south of the Kern River.

A unit composed mostly of fine-grained micaceous sandstone with 

thin interbeds of laminated siltstone and claystone crops out in the

Identified as AUodesmus kernensis (Lusian and Mohnian) by C. A. Repenning. This species is best known from 

the bone bed in the Round Mountain Silt.
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J29

TABLE 6. Checklist of foraminifers from Jim Riley [Standard Oil of California], 

"Jeppi-Camp" 67-S well in sec. 8, T. 30 S., R. 29 E.

[F, few (2-20 specimens); R, rare (1 specimen). Depths shown are 

those given on ditch samples]

FORMATION

SERIES

STAGE

SPECIES DfFPTT)H

Cibicides floridanus (Cushman) 

Giobobulimina pacifica Cushman 

Plectofrondicularia californica Cushman &

C < OTJQ nt" M »_ ^^^^ . _ «____

Gyroidina soldanii d'Orbigny -

Nonionella costifera (Cushman) 

Nonionella of. N. incisa (Cushman) 

Bolivina marginata Cushman 

Lenticulina simplex (d'Orbigny) 

Uvigerinella obesa Cushman 

Uvigerinella obesa impolita Cushman & Laiming

Siphogenerina mayi Cushman & Parker 

Bolivina sp . 

Cibicides americanus (Cushman) 

Marginulina exima Neugeboren 

Cassidulina monicana Cushman and Kleinpell 

Cassidulina californiensis Bramlette 

Lenticulina colorata (Stache) 

Siphogenerina transversa Cushman 

Trochammina sp . 

Uvigerina j^oa^uinensis Kleinpell 

Freeman 

Round sift 

Mountain 

~m OlceM(?) Sllt -- Sand

Miocene

Saucesian

o o o o o 

o CM -=r vo oo in in in in in in in in in in

F

T}

F R F R 

R R 

R D

 F R 

Zemorrian

o o

O OJ

in in

F F 

R 

 

R F

R 

R 

~ R

 R
J30 CONTRIBUTIONS TO STRATIGRAPHY

TABLE 7. Checklist offoraminifersfrom outcrops of Miocene strata in the 

southeastern San Joaqnin Valley, California

[X, present. Units sampled at various localities: 

Mf2938, Round Mountain Silt; Mf2953, Freeman Silt; 

Mf2993, Bena Gravel (paralic facies); Mf2944, 

FruitvaleC?) Shale]

SERIES Miocene

STAGE

SPECIES LOCALITY

Bolivina advena Cushman XXX

Boldia of. B. hodgei (Cushman & Schenck) X

Elphidium sp. X

Epistominella ramonensis Cushman & KleinpellFursenkoina californiensis (Cushman) X

Globobulimina pvula (d'Orbigny) X

Globocassidulina margareta (Karrer) X X

Gyroidina orbicular is planata Cushman X

Gyroidina soldanii d'Orbigny X

Lagena sp. X

Lagena sulcata Walker & Jacob X

Lenticulina simplex (d'Orbigny) X

Marginulina dubia Neugeboren X

Nonionella costifera (Cushman) XX 

Nonionella incisa (Cushman) XX 

Nonionella miocenica Cushman X

Planulina appressa Kleinpell X

Plectofrondicularia californiensis (Cushman)- X

Uvigerinella obesa Cushman XXX

Uvigerinella obesa impolita Cushman & Laiming X 

Valvulineria californica Cushman X

Valvulineria ornata XX

Bolivina conica Cushman X

Buliminella curta Cushman X

Buliminella subfusiformis Cushman ~ X

Buliminella sp. X

Bulimina montereyana Kleinpell X

Bulimina montereyana delmontensis Kleinpell X

Bulimina pseudoaffinis Kleinpell X 

Epistominella gyroidinaformis (Cushman &

Goudkoff) x

Hopkinsina magnifica Bramlette X

Uvigerina hootsi Rankin X
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J31

TABLE 8. Checklist of marine diatoms from outcrops of Miocene strata in the southeastern San Joaquin Valley, California

[Data from J. A. Barren (written communs., 1976, 1980X. X, 

present; ?, uncertain. Units sampled at various localities: Mf29M1, Mf2994, and Mf2995, Round Mountain Silt; 

Mf2942, unnamed siltstone and sandstone in Tejon Hills; 

Mf5b09, Bena Gravel (paralic facies)]

SERIES Miocene

Middle

ZONE/SUBZONE

Denticulopsis 

lauta zone

(Barren, 1981)

SPECIES LOCALITY CM CM CM CM in

CM CM CM 'i-t <i-t

s s s s s

Actinocyclus ingens Rattray X X X X X

Actinoptychus kernensis Hanna X

Actinoptychus thumii Schmidt X

Coscinodiscus endoi Kanaya X ? 

Coscinodiscus marginatus Ehrenberg X

Cussia praepalecea (Schrader) Schrader X

Cussia sp. X

Cymatosira andersoni Hanna X

Delphineis sp. of D. penelliptica Andrews X

Denticulopsis hyalina (Schrader) Simonsen X

Denticulopsis lauta (Bailey) Simonsen X XXX 

Denticulopsis norwegica (Schrader) Simonsen X

Glyphodisous stellatus Greville X 

Hemiaulus polymorphus Grunow X 

Mediaria splendida Shesukova-Poretzkaya X X 

Melosira sulcata (Ehrenberg) Kutzing X 

Qpephora schwartzii? (Grunow) Petit X 

Rha phone is angustata Pantocsek X 

Rhaphoneis miocenica Schrader X X X 

Rhaphoneis obesa Hanna X X X 

Rhaphoneis parilis Hanna X

Rhaphoneis cf. R. parilis Hanna X

Stephanopyxis sp. X X 

Synedra Jouseana Sheshukova-Poretzkava X X

Triceratium condecorum Brightwell X X 
J32 CONTRIBUTIONS TO STRATIGRAPHY

Tejon Hills (Bartow and Dibblee, 1981). This unit, which is probably 

correlative with the Round Mountain Silt, lies conformably on the 01- 

cese Sand and appears to be disconformably overlain by an upper 

Miocene marine sandstone (fig. 5). The siltstone-sandstone unit contains middle Miocene diatoms (table 8).

The Round Mountain Silt has been considered Relizian to Saucesian (Ferguson, 1941; Rudel, 1965) or latest Saucesian to Luisian 

(Beck, 1952). These age assignments are too old for most of the unit. 

An outcrop sample (loc. Mf2938, table 7), about 45 m above the base of 

the Round Mountain in the area just southeast of the Round Mountain 

oil field (fig. 1), contains a Luisian benthic-foraminiferal fauna. In subsurface sections, the Round Mountain is characterized by the distinctive "Valv. cat. flood" (Valvulineria califomicd), which is generally 

considered to be synonymous with the Luisian Stage. Benthicforaminiferal faunas in the subsurface sections include such restricted 

or diagnostic Luisian species as Bolivina advena striatella, B. imbricata, Cassidulina panzana, Siphogenerina branneri, Uvigerina 

joaquinensis, Valvulineria californica s.l., and V. ornata (tables 2-4). 

These faunas support a Luisian age for the Round Mountain Silt, although unsampled intervals may contain Relizian faunas. Diatoms from 

outcrop samples in the upper part of the unit (table 8) are assigned to 

the Denticulopsis lauta zone, which is correlative with the Luisian 

Stage. The age of the Round Mountain, therefore, is early(?) and middle Miocene (fig. 2).

FRUITVALE SHALE OF MILLER AND BLOOM (1937)

The name "Fruitvale Shale" was apparently used informally in 

subsurface correlations in the southern San Joaquin Valley for several 

years before being introduced into the literature by Miller and Bloom 

in 1937. As first used, the unit consisted of dark poorly sorted carbonaceous silt of late Miocene age below the "Santa Margarita" Formation.

The Fruitvale Shale is Mohnian (late middle and late Miocene) (fig. 

2; Beck, 1952). The only known outcrops that might be identified as the 

Fruitvale Shale are at Comanche Point, about 30 km southeast of 

Bakersfield, where a small area of silty claystone has yielded an early 

to middle Mohnian foraminiferal fauna (sample Mf2944, table 7), although that outcrop is probably only a tongue of the Fruitvale in a 

thick upper Miocene marine sandstone (fig. 5). Benthic foraminifers 

from subsurface sections compose an early to middle Mohnian assemblage characterized by such age-diagnostic species as Bolivina 

girardensis, B. obliqua, Uvigerina hootsi, and U. peregrina (table 2).

"SANTA MARGARITA" AND CHANAC FORMATIONS

Merriam (1916) introduced the names "Santa Margarita" and 

"Chanac" for the outcrops of upper Miocene strata in the Tejon Hills
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J33

area. The original description of the nonmarine Chanac by J. P. 

Buwalda (in Merriam, 1916, p. 113-114) did not include a stratigraphic 

section or a map, and so there is some uncertainty about which beds he 

intended to include in the formation. Hoots (1930) provided a map and 

a more complete description of the Chanac Formation, and it is his 

usage that has been followed by subsequent workers. As used by 

Hoots, the Chanac is easily differentiated from underlying units because of its prevailing brown color.

The "Santa Margarita" Formation is a marine sandstone that conformably underlies the nonmarine Chanac. Subsurface correlations indicate that the lower part of the Chanac is the lateral equivalent of the 

"Santa Margarita." The "Santa Margarita," as mapped in the Tejon 

Hills by Hoots (1930), included an extensive area of nonmarine 

sandstone, claystone, and conglomerate below the fossiliferous marine 

sandstone. As noted above, Dibblee and Warne (1970) referred these 

nonmarine strata to the Bena Gravel.

Previous workers (see Hoots, 1930, and Ferguson, 1941) have generally agreed that an unconformity exists at the base of the "Santa 

Margarita" Formation, although in the Tejon Hills area there is uncertainty about the position of the base of the "Santa Margarita." In the 

area east of Comanche Creek, a unit of coarse-grained marine 

sandstone and conglomerate abruptly overlies generally finer grained 

older units (fig. 5) and appears to overlap most or all of the older section (Bartow and Dibblee, 1981). Part of this apparent overlap is due 

to rapid thinning of the older units by facies change, and no angular 

discordance is apparent at the contact. The field evidence favors only 

a local unconformity.

An angular unconformity can be seen west of lower Comanche 

Creek, where the "Santa Margarita" Formation, represented by a unit 

of thin white sandstone conformably below the buff to brown Chanac 

Formation, overlies light- and greenish-gray sandstone and claystone 

of the Bena Gravel. The presence of an unconformity in this part of the 

section is supported by evidence from vertebrate paleontology. Two 

vertebrate assemblages occur in the Tejon Hills (Drescher, 1942; Savage, 1955) one at the base of the Chanac Formation, and one in the 

uppermost part of the Bena Gravel (Santa Margarita Formation of 

Hoots, 1930). According to Drescher (1942, p. 7), the "striking differences" that distinguish the faunas, which are as close as 15 m apart 

stratigraphically, suggest a break in deposition between the two units. 

The "Santa Margarita" Formation in this area, then, is restricted to 

the thin white marine sandstone that lies below the Chanac and unconformably above the lower nonmarine unit now called the Bena Gravel.

A thin white sandstone and conglomeratic sandstone in the Kern

River area that unconformably overlies the Round Mountain Silt and is

unconformably overlain by the Kern River Formation was mapped as

the "Santa Margarita" Formation by Dibblee and others (1965). Alhough marine fossils are abundant in the "Santa Margarita" at Comiche Point (B. L. Clark, in Merriam, 1916, p. 115; Hoots, 1930), they
J34 CONTRIBUTIONS TO STRATIGRAPHY

have not been found in the thin unit in the Kern River area (Addicott, 

1970). Because of the absence of fossils and the poor sorting of the sand 

and gravel, this unit was questionably referred to the Chanac by Bartow and Doukas (1978). Although marine "Santa Margarita" sandstone 

is present only a few kilometers downdip to the west, "Chanac" is 

probably a more appropriate name for the outcrops of this unit (fig. 3).

Most information on the age of the "Santa Margarita" and Chanac 

Formations comes from the Tejon Hills outcrops, where both formations are fossiliferous. The sandstone beds of the "Santa Margarita" 

bear late Miocene marine mollusks (B. L. Clark, in Merriam, 1916, p. 

115; Hoots, 1930), and continental vertebrates have been found at the 

base of the Chanac; these vertebrates are of the Montediablan Stage 

(late Clarendonian age) of Savage (1955). Late Miocene marine 

megafossils are also common in the "Santa Margarita" in the subsurface (Addicott, 1970).

In summary, the "Santa Margarita" and Chanac Formations are 

considered to be different facies of the same upper Miocene depositional sequence (fig. 2) that, in outcrop, unconformably overlies older 

Miocene strata. The "Santa Margarita," however, apparently becomes 

conformable with the underlying Fruitvale Shale of Miller and Bloom 

(1937) in the subsurface to the west. The "Santa Margarita" is no more 

than 15 to 20 m thick in outcrop at Comanche Point but reaches a thickness of more than 200 m in the subsurface. The Chanac is from 90 to 

more than 300 m thick in the Tejon Hills (Hoots, 1930) but no more 

than 30 m thick in the Kern River area. The thickness of the Chanac 

is indeterminate in the subsurface because of the difficulty in differentiating the Chanac from the Kern River Formation.

KERN RIVER FORMATION

The Kern River Formation is the youngest Tertiary unit in the 

southeastern San Joaquin Valley. It unconformably overlies older Tertiary strata and laps onto pre-Tertiary basement rocks about 50 km 

north of Bakersfield. The lower part of the nonmarine Kern River intertongues westward with the marine Etchegoin Formation, and the 

upper part of the Kern River is equivalent to the San Joaquin and Tulare Formations of the west side of the valley. The Kern River, now 

considered to be late Miocene, Pliocene, and early Pleistocene(?), is 

discussed in more detail by Bartow and Pittman (1983).

GEOCHRONOLOGY

The geochronology of Miocene strata in California is based on the 

dating of KleinpelTs (1938) benthic-foraminiferal stages by Turner 

(1970). The stage boundaries shown in figure 2 have been adjusted 

slightly to conform to the K-Ar ages recalculated according to new 

decay and abundance constants (Steiger and Jager, 1977). The ages for 

the Zemorrian-Saucesian boundary (originally 22.5, now 23 m.y.) and
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J35

the Saucesian-Relizian boundary (originally 15.3, now 15.7 m.y.), which 

are most critical to this discussion, were the least ambiguous of 

Turner's results. Recent correlation of the California benthic stages 

with the European stages by means of a deep-sea planktonic biochronology (Poore and others, 1981) suggests that the California stage 

boundaries may need to be revised. These new correlations, however, 

have not yet been reconciled with the chronology derived from the dating of rocks within the province. Evidence of the time-transgressiveness of benthic assemblages is also accumulating (for example, Brabb 

and others, 1977, fig. 2; Crouch and Bukry, 1979); but regardless of 

where correlations of the benthic stages may eventually lead, there is 

presently no direct evidence to contradict Turner's age determinations 

for the stage boundaries in the San Joaquin basin.

The Tertiary section in the southeastern San Joaquin Valley contains several tuff beds that might provide additional age control for the 

associated sedimentary rocks and their contained faunas. Samples from 

a thin vitric tuff in the Round Mountain Silt, a thick ash-flow tuff in the 

type section of the Walker Formation, and pumice pebbles from the 

pumiceous sandstone in the Olcese Sand were collected for radiometric 

dating.

WALKER FORMATION

A thick pumiceous rhyolite tuff occurs about 365 m below the top 

of the type section of the Walker Formation in Walker Basin Creek. 

The outcrop consists of a massive ash-flow unit, about 3 m thick, that 

was apparently confined to a channel, and an overlying much thicker 

water-laid tuff that is interbedded with sedimentary rocks of the 

Walker Formation. Both units were sampled, and the petrology of the 

samples, together with trace- and minor-element chemistry of the glass 

fractions, was determined by neutron-activation analysis of cleaned 

glass separates (A. M. Sarna-Wojcicki, written commun., 1979). The 

results indicate that the two units are virtually identical in composition. Plagioclase from the ash-flow unit was dated by the K-Ar method 

at 21.4 m.y. (field No. GV75-2, table 9).

Evidence that the Jewett Sand and the lower part of the Freeman 

Silt are partly Zemorrian, that is, older than 23 m.y., indicates that the 

upper part of the Walker Formation south of the Bakersfield arch must 

be partly equivalent to the Jewett and the lower part of the Freeman. 

This would be the case even if the tuff were actually 1 m.y. older, 

which would be more than the probable error (±0.6 m.y.) of the K-Ar 

age. Additional dates from the tuff might refine this age somewhat but 

would probably not greatly change the relations shown in figure 2.

OLCESE SAND

The abrupt appearance of a high concentration of pumice pebbles 

and grains in the pumiceous sandstone zone of the Olcese Sand
J36 CONTRIBUTIONS TO STRATIGRAPHY

TABLE 9. Analytical data far K-Ar age determinations

[Field No. GV74-1, tuff in the Round Mountain Silt; field No. GV75-13, pumice 

pebbles from the Olcese Sand; field No. GV75-2, tuff in the Walker Formation. 

Potassium determinations by J. Tillman, J. Christie, and M. Cremer; argon 

determinations and age calculations by A. Berry, E. Sims, and J. Von Essen. 

''"K decay constants: A =4.962xl(T 10 yr" 1 , X +A '=0. SSlxKT 1 ° yr" 1 , and 1+0 K/K= 

1.167X10-4 mol/mol] £ £

Field 

No.

GV74-1 

GV75-13 

CT7S-?

Mineral K2 

(wt

 10.

 1.

0 

pet)

955

449

125 

000

snfi

(ID' 12

804 

28

318 

27

IS

rad 

mol/g)

.2 

.20

.9

.50

.61

rad

r total

0.86 

.70

.80 

.59

.49

Calculated 

age 

(m.y.)

61. 

43.

21. 

19.

21.

3+1. 

1+1.

8+0. 

0+0.

4+n

8 

3

6

8

6

suggests that the pumice was transported and deposited very soon 

after eruption. An age for the pumice should be close to, but no 

younger than, that of the containing sediment.

Feldspar (plagioclase and sanidine) and zircon crystals separated 

from large pumice pebbles, which had first been cleaned of adhering 

sediment, were dated by the K-Ar and fission-track methods, respectively. The results, summarized in tables 9 and 10 (field No. GV75-13), 

show an age spread of 6.3 m.y. that appears to span the stratigraphically determined age of the pumice-bearing sediment.

Where K-Ar ages are older than a fission-track age for the same 

unit, the best explanation is that the sample contained an admixture of 

older material. The feldspar concentrates, then, would be composites 

of crystals of different ages, and the resulting K-Ar age would fall 

somewhere between the oldest and youngest. The zircon concentrate 

would also contain older crystals, but because the crystals were 

examined and counted individually, the older population can be eliminated from the age calculation. The fission-track age of 15.5 m.y. was 

based on six zircon grains; however, a seventh zircon that was counted 

had an age of 28.2 m.y. which indicates the presence of older material 

in the sample. The best of these three ages, then, is the fission-track 

age of 15.5 m.y., which is very close to the stratigraphically determined age of the pumice bed. The older contained material could be 

either detrital grains that had worked deeply into the porous pumice, 

or a separate population of pumice pebbles from an older deposit in the 

source area. The fact that the sanidine K-Ar age is the oldest argues 

against detrital-grain contamination because detrital sanidine is rare in 

the Kern River area.

ROUND MOUNTAIN SILT

A thin fine-grained vitric tuff, about 45 m above the base of the 

Round Mountain Silt and within 1 m of Luisian locality Mf2938 (fig. 3),
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J37 

TABLE 10. Analytical data far fission-track age determinations

[Field No. GV74-1, tuff in the Round Mountain Silt (5 zircons counted); field No. 

GV75-13, pumice pebbles from the Olcese Sand (6 zircons counted). Age determinations by C. E. Meyer and C. W. Naeser, respectively]

Field

No.

GV74-1

GV75-13

U

(ppm)

216

210

Spontaneous

Density 

(106 /cm2 )

3.34

1.78

tracks

No.

947

527

Induced

Density 

(10 6 /cm2 )

6.50

5.15

tracks

No.

922

763

Neutron

flux

1.35

.732

Calculated

age 

(m.y.)

41.4+1.9

15.5+1.7

was dated by both the K-Ar and fission-track methods. The resulting 

K-Ar ages of 43.1 and 61.3 m.y. from plagioclase and biotite, respectively (field No. GV74-1, table 9), were judged to be too old by a factor 

of 3, most probably because of the inclusion of detrital minerals derived 

from the Sierra Nevada batholith.

The fission-track age of 41.4 ± 1.9 m.y. from the zircons (field No. 

GV74-1, table 10) oddly coincides with the plagioclase K-Ar age. Because this fission-track date is derived from individual grains, it cannot 

reflect a mixing of old and young populations, as is the case with the 

K-Ar ages. Nor is it likely that the zircons were derived from 41-m.y.- 

old igneous rocks, because this age falls within the early Cenozoic magmatic null period (Snyder and others, 1976), although the existence of 

an Eocene tuff, now altered or removed by erosion, cannot be discounted. Bentonite and other volcanic detritus have been recognized in 

Eocene strata elsewhere in central California. Another possible explanation is that older (approx 41 m.y.) zircons in rocks of the vent area 

were thermally reset at 41 m.y., or partially reset at some later time, 

and then still later became accidental constituents of the middle 

Miocene ash.

SUMMARY

Radiometric dating of pyroclastic material from Tertiary rocks in 

the southeastern San Joaquin Valley has produced mixed results. Despite a few questionable age, these results are, on the whole, encouraging because they represent only single-sample dating of what are relatively complex deposits.

The best material for dating came from the tuff in the Walker Formation, and we consider the age of 21.4 m.y. to be reasonably accurate 

for this tuff, even though a single sample provides no means for assessing possible area! or stratigraphic variations in composition within the 

massive ash-flow unit. The best agreement with an age inferred from 

stratigraphic position is provided by the pumice bed in the Olcese 

Sand. Although each pebble is, in effect, a separate sample, the fissiontrack dating technique affords a means of discriminating between older
J38 CONTRIBUTIONS TO STRATIGRAPHY

and younger material, and the age of 15.5 m.y. is probably accurate for 

the pumice that was deposited a short time later in the Olcese Sand. 

A worst case is illustrated by the tuff in the Round Mountain Silt. A 

thin tuff in a marine siltstone should always be suspect, even if is looks 

pure, because of the strong probability of inmixing of a small amounts 

of detrital minerals by bioturbation.

These results, though of some usefulness to San Joaquin Valley 

stratigraphy, should be considered preliminary. Careful multiple sampling, exacting mineral-separation procedures, and replicate analyses 

should refine the ages reported here and remove any remaining ambiguities.

DISCUSSION

BASIN HISTORY

The Tertiary strata of the southeastern San Joaquin Valley record 

a major transgression, beginning in Eocene time and continuing into 

the Miocene, that was punctuated by relatively minor regressions at 

the end of Eocene time (as evidenced by a small tongue of the nonmarine Walker Formation overlying a probable lagoonal fades of the 

late Eocene age; fig. 3), near the end of Zemorrian time, and at the end 

of Saucesian time (the Olcese Sand). Evidence from benthic foraminifers also suggests a regression near the end of Luisian time. A major 

and relatively rapid regression began in late Miocene time and continued into the Pleistocene, with only two minor marine transgressions 

("Santa Margarita" and Etchegoin Formations).

The Paleogene formations, such as the Vedder Sand and the 

Walker Formation, are relatively thin, considering the timespan that 

they represent. Their thinness, together with their widespread distribution and relatively uniform lithology, suggests a period of relative 

stability. However, the coarse Bealville Fanglomerate is evidence of 

some tectonic activity near the end of the Paleogene. Increased tectonic activity, beginning near the end of Saucesian time, produced the 

coarse clastic materials of the Bena Gravel, the Olcese Sand, and the 

Chanac and Kern River Formations, and was responsible for the major 

regression beginning in late Miocene time.

DISTRIBUTION OF COARSE CLASTIC MATERIALS

The Bealville Fanglomerate and the Bena Gravel are presently restricted to the southeast margin of the San Joaquin Valley south of the 

Bakersfield arch. The Bealville is, in addition, restricted to the area 

north of the east-west-trending Edison fault (which separates Tertiary 

and basement rocks south of Caliente Creek) and intertongues northward or northwestward with the finer grained Walker Formation. This 

relation, together with evidence that the coarse angular blocks in the 

Bealville were derived from upthrown basement rocks south of the
TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J39

fault (Dibblee and Chesterman, 1953, p. 50), indicates that the Edison 

fault was active during the time of Bealville deposition, that is, in the 

late Oligocene and early Miocene.

The Bena Gravel is related to this increased tectonic activity, 

mostly in middle Miocene time. The coarse clastic materials probably 

reflect uplift of the Sierra Nevada concurrent with faulting and subsidence in the southern part of the basin. The Bena Gravel, including 

both alluvial-fan and paralic facies, seems to represent a fan delta that 

formed at the steep east margin of the basin in response to this tectonic 

activity. The close juxtaposition of dissimilar facies in the Bena and its 

rapid transition southwestward into the Edison Shale of Kasline (1941) 

(fig. 4) contrast with the relatively simple stratigraphy without the 

rapid facies changes shown by equivalent-age strata north of the 

Bakersfield arch. This difference suggests that the Bakersfield arch 

was, by middle or possibly late early Miocene time, beginning to become an important boundary between the deep south end of the basin 

and a relatively more stable shelf area to the north.

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2d sess., Senate Ex. Doc. 78), 310 p.
J40 CONTRIBUTIONS TO STRATIGRAPHY

Brabb, E. E., Clark, J. C., and Throckmorton, C. B., 1977, Measured sections of 

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Dibblee, T. W., Jr., and Warne, A. H., 1970, Geologic map of the Cummings Mountain 

quadrangle, Kern County, California: U.S. Geological Survey Miscellaneous 

Geologic Investigations Map 1-611, 5 p., scale 1:62,500.

Diepenbrock, Alex, 1933, Mt. Poso oil field: California Division of Oil and Gas Summary 

of Operations California Oil Fields, v. 19, no. 2, p. 5-35.

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TERTIARY STRATIGRAPHY, SAN JOAQUIN VALLEY, CALIFORNIA J41

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Contributions to Stratigraphy

GEOLOGICAL SURVEY BULLETIN 1529

This volume was published 

as separate chapters A J
UNITED STATES DEPARTMENT OF THE INTERIOR 

WILLIAM P. CLARK, Secretary

GEOLOGICAL SURVEY 

Dallas L. Peck, Director

For sale by the Superintendent of Documents, U. S. Government Printing Office 

Washington, D. C. 20402
CONTENTS

[Letters designate the separately published chapters]

(A) Stratigraphic nomenclature for the Upper Devonian and Lower Mississippian(?) 

Kanayut Conglomerate, Brooks Range, Alaska, by Tor H. Nilsen and 

Thomas E. Moore.

(B) Summit Island Formation, a new Upper Cretaceous formation in southwestern 

Alaska, by J. M. Hoare, W. L. Coonrad, and Scott McCoy.

(C) Graywacke of Buchia Ridge and correlative Lower Cretaceous rocks in the Goodnews Bay and Bethel quadrangles, southwestern Alaska, by J. M. Hoare and 

W. L. Coonrad.

(D) The Kern River Formation, southeastern San Joaquin Valley, California, by J. Alan

Bartow and Gardner M. Pittman. 

(E) Cenozoic rocks in the Barstow basin area of southern California stratigraphic

relations, radiometric ages, and paleomagnetism, by D. B. Burke, J. W.

Hillhouse, E. H. McKee, S. T. Miller, and J. L. Morton. 

(F) Distribution and stratigraphic significance of foraminifers and algae in well cores

from the Madison Group (Mississippian), Williston Basin, Montana, by

William J. Sando and Bernard L. Mamet. 

(G) Las Animas Formation (upper Precambrian) in the subsurface of southeastern

Colorado, by Ogden Tweto. 

(H) Stratigraphic notes, 1980-1982. 

(I) New names for units in the lower part of the Green River Formation, Piceance

Creek Basin, Colorado, by Ronald C. Johnson. 

(J) Tertiary stratigraphy of the southeastern San Joaquin Valley, California, by J. Alan

Bartow and Kristin McDougall.

GPO 787-042/115