UNITED STATES DEPARTMENT OF THE INTERIOR 

Ray Lyman Wilbur, Secretary

GEOLOGICAL SURVEY 

George Oils Smith, Director

Bulletin 826

NAMES AND DEFINITIONS

OF THE

GEOLOGIC UNITS OF CALIFORNIA

COMPILED BY

M.GRACE WILMARTH

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON: 1931

For snle by the Superintendent of Documents, Washington, D. C. ----- Price 20 cents

PREFACE

By T. W. STANTON

In Bulletin 769, " The geologic time classification of the United 

States Geological Survey," by M. Grace Wilmarth, secretary of the 

committee on geologic names, it was announced that Miss. Wilmarth 

had in preparation a more extended compilation which will form a 

stratigraphic lexicon of the United States, containing definitions 

of all the geologic formations that have been named and described 

in this country. Work on this compilation is making good progress 

and has now reached a stage where it is possible to give geologists a 

sample of the lexicon, which will be locally useful and at the same 

time give them an opportunity to make helpful criticisms both of 

the character of the material to be included in the larger work and 

of the form in which it is presented.

It happens that California is almost completely isolated from the 

other States in its stratigraphic development and that the great local 

variations in sedimentation within its borders, epecially in Tertiary 

time, have caused the naming of an unusual number of formations. 

Less than half a dozen of the formations named in California extend 

into Oregon and Washington, and the number that come into eastern 

California from Nevada is not much larger. It is therefore thought 

desirable to issue the " Names and definitions of the geologic units 

of California " as a separate publication. Its compactness will make 

it more acceptable than the larger complete lexicon to stratigraphers 

whose work is temporarily or habitually restricted to California.

In the text that follows names of provincial and local series, 

groups, formations, members, and lentils are given under a single 

alphabetic arrangement. The terms just mentioned have had varied 

meanings in common English usage and even in geologic literature, 

but in tms paper and in other publications of the United States 

Geological Survey they are used with the technical definitions indicated by the following quotations from the rules of nomenclature and 

classification of formations published in the Twenty-fourth Annual 

Report:

in
IV . PREFACE

In all classes of rocks the cartographic units shall be called formations. * * *

When, for scientific or economic. reasons, it is desirable to recognize and 

map one or more specially developed parts of a varied formation, such parts 

shall be called members, if they have considerable geographic extent; or if 

their distribution is more limited they shall be described in some appropriate 

term, such as lentil.

All sedimentary formations shall receive distinctive designations. The most 

desirable names are binomial, the first part being geographic and the other 

lithologic (e. g., Dakota sandstone, Trenton limestone, etc.). * * * When 

the formation consists of beds differing in character, so that no single lithologic 

term is applicable, the word " formation " should be substituted for the lithologic term. [In actual practice it is customary to interpret this last statement 

rather broadly and to use the lithologic term if one lithologic type is dominant 

in a formation which has two or more kinds of sediment, such as sandstone 

with thinner beds of shale, or shale with thinner beds of sandstone and 

limestone.]

The name by which an igneous rock is designated upon the map may consist 

of two parts: (1) The petrographic designation, (2) a local term. * * * 

The local importance of igneous masses often renders the use of geographic 

terms in connection with the petrographic names highly advantageous; * * * 

e. g., Butte granite. * * *

Within the systems smaller aggregates of formations may be recognized, 

which shall be called series, and these may be divided into subordinate groups 

of formations. Groups may also be constituted without the recognition of 

series. These minor aggregates should be formed so as to express the natural 

relations of the formations of the particular province rather than to conform 

with divisions recognized elsewhere, though they may often prove to have a 

wider distribution. * * * When different provinces show a distinct development, provincial names may be used for series and groups. For example: In 

the Gulf province the lower Cretaceous is called the Comanche series, which is 

made up of the Washita, Fredericksburg, and Trinity groups, while in the Pacific province the lower Cretaceous has a different development, both lithologically and faunally, and is called the Shasta series.

In the compilation of this work Miss Wilmarth has had the full 

cooperation of John M. Nickles, of the Geological Survey library, 

who promptly furnishes the committee on geologic names with all 

important references to formation names found in the course of his 

bibliographic work on the current geologic literature of North 

America. All the names pertaining to California recorded by 

Mr. Nickles up to December 1,1930, are included in this paper.

The names here defined fall into three categories:

1. Names printed in black-face type have been approved by the 

 chief geologist on recommendation of the committee on geologic 

.names for use in publications of the United States Geological Survey.

2. Names in quotation marks have been abandoned, after consideration, either as synonyms of names in good standing or as ill defined, 

or as not needed for some other reason.
PEEFACE V

3. All other names (printed in ordinary type) have not received 

consideration for use in Geological Survey publications.

The definitions are either literal quotations of the original definitions or digests in which the words of the author cited are used. 

If the original definition differs from that in current use additional 

quotations or digests are given to show the changes made. The 

descriptions and definitions have been abbreviated as much as is 

consistent with clearness. The quotations and digests are printed in 

smaller type, but the small-type matter includes some comments by 

the compiler, indicated by brackets.

The age designation given with the geographic distribution as the 

first item beneath the name is the present accepted age classification. 

Areas north of the latitude of San Francisco are classed as northern 

California, and those south of that latitude as southern California. 

The other area! terms are self explanatory.

NAMES AND DEFINITIONS OF THE GEOLOGIC 

UNITS OF GALIFOENIA

Compiled by M. GRACE WILMARTH

Abrams mica schist.

Pre-Cambrian (?) : Northern California (Trinity and Shasta Counties).

0. H. Hershey, 1901 (Am. Geologist, vol. 27, pp. 225-245). Abrams mica eohlst. 

Is composed of thin folia of muscovlte of dull colors (gray, light brown, 

yellow, and dull red) separated by irregular layers of white quartz, representing the original laminae. Very highly siliceous throughout. Is of sedimentary 

origin, being originally a series of argillaceous sandstone beds, in part finely 

laminated. Thickness about 1,000 feet in upper Coffee Creek section, but 

may be much thicker at Bully Choop, to the south. Named for Abrams post 

office, in upper Coffee Creek region.

According to J. S. Diller (unpublished manuscript on Weaverville quadrangle) the Abrams mica schist is 5,000 feet thick.

Alameda formation.

Pleistocene: Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 103). 

Yellow sandy clay, of very uniform fine texture, which without much change 

in character passes into beds that carry marine shells. Intercalated with 

these marine deposits are nonpersistent beds of gravel of fluviatile origin, 

the conditions Indicating delta formation alternating with marine or estuarine 

deposition. Thickness several hundred feet. Unconformably underlies San 

Antonio formation and unconformably overlies Campus formation. Named for 

fact that it is well developed at Alameda.

Alamitos zone.

A petroliferous zone, about 670 feet thick, in the Fernando group of the Long 

Beach field, Los Angeles Basin, southern California. Is lower than the Wilbur 

zone and higher than the Brown zone. Includes the Booth zone. Named for 

discovery well Alamitos No. 1.

Amargosan series.

C. [R.] Keyes, 1923 (Pan-Am. Geologist, vol. 40, pp. 52, 78). "This title Is proposed 

for the thick succession of volcanics and conglomerates best exposed In the 

Amargosa Desert and in Furnace Canyon near Death Valley, and believed to be 

Early Tertic in age." In Nevada divided into Greenwater volcanics above 

and Grapevine conglomerate below. Stratigraphically unconformably above 

Zunian series and unconformably below Furnacean series.

Named for exposures in Amargosa Desert, Nye County, southwestern 

Nevada.

Anzar phase (of Santa Lucia series).

Paleozoic (provisionally) : Southern California (San Benito County).

P. F. Kerr and H. G. Schenck, 1925 (Geol. Soc. America Bull., vol. 36, pp. 470, 471, 

map). "A metarnorphic phase probably produced by serpentinizatlon of the basic 

phase of the igneous Intrusion. * * * There is a small area of red chert 

and granite associated with schist and gneiss west of the San Andreas fault In 

the vicinity of Anzar Lake. The chert appears to be Franciscan and the ser-
2 GEOLOGIC UNITS OF CALIFORNIA

pentinized schist and gneiss an alteration of the granite; all are now confused in 

their relations because of faulting. In the accompanying stratigraphic column 

they are included as the Anew phase of the Santa Lucia series. Further study 

might show that the rocks of this limited region are either (1) entirely Franciscan, (2) a slight variation of the Santa Lucia, or (3) a separate series."

Arlington formation.

Mississippian: Northern California (Taylorsville and Lassen Peak regions).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Arlington beds. 

Slates and sandstones with traces of conglomerate, 5,700 feet thick. " No fossils, 

but as they lie beneath Shoo Fly beds at one end and are associated with 

Silurian slates at the other, they are regarded as probably belonging to the 

upper Paleozoic." Older than Shoo Fly beds and younger than Taylor[s]ville 

slates.

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Arlington formation. Chiefly fine 

gray thin-bedded sandstone, with some shale, in part silicified, and a few beds of 

conglomerate. In lower member yellowish shales prevail and grade up into the 

shaly and thin-bedded greenish-gray sandstone of the middle member, which is 

well exposed in bold escarpment of Arlington Heights. In upper member, which 

is well exposed about Crystal Lake, slaty gray shales are most abundant, with 

local conglomerates and highly silicified red jaspery portions near the top. Measured thickness 5,700 feet. Is separated from overlying Shoo Fly formation by a 

great thickness of Taylor meta-andesite. Is younger than Taylorsvill? formation.

Named for Arlington Heights, Plumas County, which is composed of the 

formation and where the middle member is well exposed.

Arrastre quartzite.

Probably Lower Cambrian: Southern California (San Bernardino County).

F. B. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Scl. Bull., vol. 13, No. 9, pp. 

344, 351, 352-365, map). The oldest sedimentary rocks positively identified as 

such in the region. Quartzites and quartzose schists, chiefly thin bedded, in 

beds less than 6 inches thick. Differs from Saragossa quartzite in that it contains no beds up to 5 and 10 feet thick of pure quartzite, no pure saccharoidal 

quartzite, no coarse angular grits, pebble conglomerate, or cross-bedding. No 

fossils found. Grades into Furnace limestone above. Floor on which it was 

laid down has been destroyed by granite intrusions.

Named for Arrastre Creek, San Bernardino County.

Ashton zone.

A zone in the lower part of the Fernando group in the Huntington Beach 

oil field of Orange County, southern California. Consists of 1,200 to 

2,000 or more feet of sticky brown shale, sandy shales, sands, and hard 

shells. Some producing wells have penetrated it to a depth of at least 

1,750 feet, according to S. H. Gester.

Asphalto lake bed.

Pliocene: Southern California (northwestern part of Kern County).

J. G. Cooper, 1894 (California Acad. Sci. Proc., 2d ser., vol. 4, p. 168). A small 

fresh-water deposit of fossiliferous blackish marl, about 40 miles southeasterly 

from the Kettleman lake bed, 18 miles northwest of Buena Vista Lake, and 

1,100 feet above sea level.

Probably named for exposures at or near Asphalto, a village near McKittrick, Kern County.

"Atascadero " formation.

Upper Cretaceous: Southern California (San Luis Obispo region).

H. W. Fairbanks, 1904 (U. S. Geol. Survey Geol. Atlas, San Luis folio, No. 101). 

Thick and thin bedded sandstone with a small amount of conglomerate and 

shale. Thickness 3,000 to 4,000 feet. The local representative of the Chico 

group. Represents all of the Chico deposits present in the area. Unconformably underlies Yaquero[s] sandstone and unconformably overlies Knoxville. 

Named for exposures along Atascadero Creek, San Luis Obispo County.

Replaced by Chico formation.
GEOLOGIC UNITS OF CALIFORNIA 6

Atlas formation.

Quaternary (?) : Southern California (Kern County).

A. C. Lawson, 1906 (California Univ. Pub., Dept. Geology Bull., vol. 4, pp. 431-462). 

Ancient alluvium, made up of angular fragments of rocks of the bedrock complex, including schists, quartz diorite, granite, quartz, and arkose, well cemented. 

Older than Tank volcanics.

Derivation of name not stated and not known.

Atolia quartz monzonite.

Jurassic (?) : Southern California (Randsburg quadrangle, Kern and San

Bernardino Counties).

C. D. Hulin, 1925 (California State Min. Bur. Bull. 95, pp. 33-42, map). Intrudes 

Rand schist and the undifferentiated Paleozoic series of El Paso Mountains, 

which may be in part Carboniferous. Unconformably underlies middle Miocene 

sediments (Rosamond series). Is the undoubted correlative of the plutonic 

rocks of the Sierra Nevada and is probably of late Jurassic age. Named for 

exposures at and around Atolia, San Bernardino County.

"Auriferous slate series."

A descriptive term used in folios and other early reports on the Gold Belt 

region of northern California, to include the Mariposa slate and Calaveras formation, and in contradistinction to the " Superjacent series," a 

descriptive term applied to the Cretaceous, Tertiary, and Quaternary 

deposits of the region.

"Auriferous slates."

Term in common use by Whitney (Geological Survey of California) and 

subsequent writers for undifferentiated Paleozoic and Mesozoic strata 

in the Sierra Nevada.

Avenal sandstones.

Eocene: Southern California (Diablo Range).

F. M. Anderson, 1905 (California Acad. Sci. Proc., 3d ser., vol. 2, pp. 164-168). 

Avenal sandstones. A great thickness of sandstone, exposed along the canyon 

of Canoas Creek with a thin basal bed of conglomerate, 6 to 10 feet thick, 

resting upon the Lower Cretaceous shales. The upper 400 feet consists of very 

fossiliferous concretionary sandstones, below which occur thin-bedded sandstone. The Avenal wells at Tar Springs are drilled to penetrate these sands, 

which are exposed at Tar Springs on the east and at Sulphur Springs on the 

Zapata Chino Creek to the west. Underlie Kreyenhagen shales.

F. E. von Erstorff, 1930 (Am. Assoc. Petroleum Geologists Bull1 ., vol. 14, No. 10, pp. 

1321-1336). The 500 feet of sandstone underlying Kreyenhagen shale in canyon 

of Canoas Creek is the Domengine sandstone, of upper middle Eocene age. The 

type locality of the Domengine is north of Coalinga.

Bagley andesite.

Lower (?) Jurassic: Northern California (Redding quadrangle).

J. S. Diller, 1906 (U. S. Geol. Survey Geol. Atlas, Redding folio, No. 138). "Includes the lavas and pyroclastics of a succession of volcanic eruptions of similar 

general character. It is commonly filled with an abundance of small phenocrysts 

of plagioclase, and rarely also with dark grains in a greenish groundmass." 

Is composed chiefly of andesitic tuff, sometimes coarse, almost agglomeratic, but 

generally fine and stratified, with occasional traces of marine fossils. More 

than three-fourths of the Bagley Mountain area is occupied by tuff. The lavas 

are most abundant near the summit, and the whole mass has a thickness of 

about 1,000 feet. "Both areas [Bagley Mountain and along Fit River] of 

the Bagley andesite lie practically on the border between the Potem and Modln 

formations but do not necessarily indicate an unconformity. These areas 

represent centers of greater accumulation of volcanic material near points of 

eruption during the beginning of the Potem epoch. Between the two points 

the contemporaneous sediments contain some detritus from both centers, but 

apparently the greater portion comes from a different source. For this reason 

the intermediate sediments were included in the Potem."
4 GEOLOGIC UNITS OF CALIFORNIA

Baird shale.

Mississippian: Northern California (Redding region).

H. W. Fairbanks, July, 1894 (Am. Geologist, vol. 14, p. 28). Black siliceous shale, 

probably 500 feet thick, the lowest horizon recognized at the United States 

fisheries on McCloud River. Fauna considered by J. P. Smith to be analogous 

to the Waverly, but stratigraphic position is higher. The shales outcrop most 

prominently on west side of the river just above Baird post office where they are 

in places highly metamorphosed by dikes of diabase and diabase porphyrite.

J. P. Smith, September-October, 1894 (Jour. Geology, vol. 2, pp. 588-612). Baird 

shale. Black siliceous shales 500 feet thick. Older than McCloud limestone 

and younger than Sacramento formation [Kennett formation].

According to J. S. Diller (U. S. Geol. Survey Geol. Atlas, Redding folio, 

No. 138, 1906) the Baird shale overlies the Bragdon formation and 

underlies the McCloud limestone.

" Balaklala rhyolite."

Jurassic (?) : Northern California (Redding quadrangle).

J. S. Diller, 1906 (U. S. Geol. Survey Geol. Atlas, Redding folio, No. 138). A succession of irregular lava flows and tuffs which have been so compressed and 

folded as. to render very obscure the original layered arrangement of the mass. 

Thickness about 500 feet. Clearly underlies the Kennett limestone and shale 

and penetrates and overlies the Copley metaandesite. Named for fact that it 

forms the hills about the Balaklala mine.

Later work by L. C. Graton (U. S. Geol. Survey Bull. 430, pp. 81-85, 

1910) proved these rocks to be intrusive alaskite porphyry and the same 

as the so-called "Bully Hill rhyolite." Both geographic names have 

therefore been discarded as unnecessary. This porphyry cuts rocks as 

young as Pit shale (Middle and Upper Triassic).

Bald Peak basalt.

Pliocene: Western California (San Francisco region).

A. C. Lawson and C. Palache, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 

2, map at end). Top formation of Berkeleyan series [Berkeley group]. Forms 

large part of Bald Knob, east of Berkeley.

Barstow formation.

Miocene (upper) : Southern California (San Bernardino County).

O. H. Hershey, 1902 (Am. Geologist, vol. 29, pp. 369-370). Barstow series. A thin 

valley formation made under arid conditions. Occurs at several points in Mohave River Valley, notably along the railroad about 1% miles east of Barstow 

[San Bernardino County]. Type section near Barstow consists of 

1. Stratified hard brown material due to arid conditions but composition not 

determined. Persistent over considerable area. 20 feet.

2. Yellow and light-gray silt. 4 feet.

3. Stratified fine gravel and sand of dull red color and containing red lava 

fragments. 15 feet.

4. Structureless bed of white tuff with angular and subangular fragments of

various other rock species embedded in it. 20 feet.

Is extensively developed on low hills on north side of valley between Barstow 

and Daggett. Unconformably overlies Rosamond and Escondido series. Extensively eroded. Overlain unconformably by Quaternary.

J. C. Merriam, 1915 (Pop. Sci. Monthly, vol. 86, pp. 252-254). The term Barstow 

formation is used for the beds containing the Upper Miocene vertebrate fauna.

J. C. Merriam, 1919 (California Univ. Pub., Dept. Geology Bull., vol. 11, No. 5, pp. 

441-448). Barstow formation or group. Mainly bluish gray to yellowish brown, 

|lightly indurated strata, composed largely of fine arkose with a considerable percentage of volcanic ash. In an earlier publication (California Univ. Pub., Dept. 

Geology Bull., vol. 6, p. 168, 1911) the writer referred to the fauna of Barstow 

syncline as the Mohave fauna, this name being considered mainly a geographic 

designation. Later, in order to avoid confusion with other Tertiary faunas occurring in the Mobave area, the name Barstow has been used for this faunal assem-
GEOLOGIC UNITS OF CALIFORNIA 5

blage, and Barstow formation for the beds containing the Upper Miocene or 

Barstow fauna. This formation comprises the uppermost of the five divisions 

[of the Rosamond series] in the Barstow syncline, described by Baker [California 

Univ. Pub., Dept. Geology Bull., vol. 6, 1911] as fossiliferous tuff member, and 

any other beds which may be recognized as representing the horizontal or vertical extension of the same depositional unit. The limits of the Barstow formation may be found to correspond with those of the fossiliferous tuff member, or 

they may include a greater range of sediments above and below. It is possible 

that the Barstow fauna occurs in all of the strata of the Barstow syncline. It is 

also possible that the lowest strata of that section will be discovered to contain 

a faunal assemblage much older than the particular Upper Miocene assemblage 

known as the fossiliferous tuff. The resistant breccia member immediately below 

the fossiliferous tuff in Baker's Barstow syncline section seems to contain a 

representation of the Barstow fauna and may ultimately be included in the Barstow formation. Should the resistant breccia be recognized as a distinct formation the name Barstow group may be used for the sequence of formations. Excepting marine deposits of Eocene age, the oldest Tertiary rocks in the Mohave 

area of which the age is certainly known are included in the Barstow formation. 

Fauna [listed] is distinctly older than Ricardo fauna. Assigned to Upper 

Miocene.

" Basement complex."

" Basement complex " and " Bedrock complex " are descriptive terms that 

have been rather loosely applied in the literature to the basement rocks 

of a region, whether they are or are not of complex structure.

Bass Mountain diabase.

Mississippian: Northern California (Redding quadrangle).

J. S. Diller, 1906 (U. S. Geol. Survey Geol. Atlas, Redding folio, No. 138). Nonporphyritic dark, somewhat greenish compact lava, occasionally vesicular and 

more frequently fragmental. Is contemporaneous and partly interbedded with 

the upper part of the Bragdon formation. Named for fact that It forms southern 

slope of Bass Mountain.

Bautista beds. :

Pleistocene: Southern California (San Jacinto quadrangle).

C. Frlck, 1921 (California Univ. Pub., Dept. Geology Bull., vol. 12, pp. 283-;288). 

The Bautista beds occur in the Bautista Badlands or Bautista Creek area. They 

have yielded vertebrate fossils, and were evidently accumulated in part in a, 

playa-llke lake, as a series of fine, worked-over fanglomerates and clays derived 

from low highlands of the immediate north and east.

Bear River series.

Miocene: Northern California (Humboldt County).

W. Stalder, 1915 (California State Min. Bur. Bull. 69, pp. 447-449). Conglomeratic 

sandstones and conglomerate, resting on arenaceous bands and yellowish sandstones of .medium texture, poorly cemented, underlain by 300 feet of shales of 

nodular character containing a little interbedded limestone and some glauconitic 

sand. -Very fossiliferous at-'south fork of Bear River. Thickness 750 feet. Assigned to upper Miocene. Underlies Wild Cat series and overlies Rainbow series 

(post-Franciscan).

" Bedrock complex." See " Basement complete."

"Bedrock series." . A descriptive term used in folios and other early reports on the Gold Belt 

region of northern California, to include the Jurassic, Triassic, and 

Carboniferous formations, in contradistinction to " Superjacent series," 

which included the Cretaceous, Tertiary, and Quaternary deposits. The 

term has also been applied to the basement rocks of any region.

Bell oil zone.

Name applied to oil-bearing zone, about 370 feet thick, in the Santa Fe 

Springs field, Los Angeles County. Is capped by Foix oil zone and in 

turn caps the Meyer zone. Top lies at depth of 3,650 to 3,850 feet. 

Basal bed consists of 30 to 50 feet of sticky brown shale.
6 GEOLOGIC UNITS OP CALIFORNIA

"Bend formation."

Middle and Lower Jurassic: Northern California (Gold Belt region).

J. S. Diller, 1892 (preliminary proof-sheet edition of Lassen Peak folio, U. S. Qeol. 

Survey Geol. Atlas) and 1895 (published Lassen Peak folio, No. 15). The Bend 

formation contains some limestone but is composed chiefly of slates, sandstones, 

and conglomerates and crops out along the western arm of the great bend of 

Pit River. Isolated areas of the limestone are exposed near the stage road 

1 mile west of Montgomery Creek, and the slates and sandstones form the upper 

part of the north slope of Cedar Creek 4 miles west of Round Mountain. 

Jurassic fossils. Rests on Cedar formation and is overlain by Chico formation.

H. W. Fairbanks, July, 1894 (Am. Geologist, vol. 14, p. 27). " The Bend formation, 

then, consisting of slates and argillaceous limestone, embraces as far as is known 

the Lower and0 Middle Jura."

J. P. Smith, October, 1894 (Jour. Geology, vol. 2, p. 611). The Bend formation was 

named by J. S. Diller (U. S. Geol. Survey Geol. Atlas, Lassen Peak sheet, 1892), 

to include all the Jurassic deposits of the region of the Big Bend of Pit River. 

In a later publication Mr. Diller (Bull. Geol. Soc. America, vol. 4, 1893, p. 221) 

says that the Pit River Jura corresponds to the Mormon sandstone, Middle Jura, 

of the Taylorsville region. About 6 miles west of Big Bend, in Big Canyon, 

H. W. Fairbanks discovered fossils in shaly limestones which, on examination 

by the writer, proved to be Jurassic and probably equivalent to the Hardgrave 

sandstone, Lower Jura, of Indian Valley.

Includes Potem and Modin formations.

Berkeley group.

Pliocene: Western California (San Francisco region).

A. C. Lawson and C. Palache, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 

2, p. 375, map). The entire series of rocks, volcanic and sedimentary, from the 

base of the Orindan formation to the crest of Frowning Ridge, is here named 

the Berkeleyan series, and the interval in question is regarded as having a break 

in its accumulation dividing it into Upper and Lower Berkeleyan. The Upper 

Berkeleyan includes Bald Peak basalt, Siestan formation, Grizzly Peak andesite, 

and several other unnamed formations. The Lower Berkeleyan includes the 

Trampan and Orindan formations and a great thickness of unnamed igneous and 

sedimentary formations. The Berkeleyan series is uncouformably overlain by 

the Campan series and unconformably underlain by the Monterey series.

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Berkeley group includes rocks between the top of the Orinda formation and 

the base of the Campus formation. Divided into (descending order) Bald Peak 

basalt, Siesta formation, and Moraga formation. Rests with probable uncon- 

 formity on Orinda formation and is unconformably overlain by Campus formation.

Named for occurrence east of Berkeley. 

"Berkeleyan series." See Berkeley group.

Bicknell sandstone.

Upper Jurassic: Northern California (Taylorsville region).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Light-gray or 

bluish-gray sandstone, sometimes tufaceous above. Thickness 500 feet. Is older 

than Hinchman tuff and younger than Mormon sandstone.

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Chiefly red and gray sandstone 

associated with some dark shales and tuffaceous beds. Brownish-red sandstone 

forms the earliest part of the formation. The middle portion is composed of 

compact fine dark-gray sandstone interbedded with black shaly beds. The upper 

part consists of tuffaceous gray sandstone. Thickness 500 to 1,300 feet. Overlies, probably conformably, the Mormon sandstone and grades into the overlying 

Hinchman sandstone. Greatest development on southeast slope of Mount Jura, 

Plumas County.

Named for BicknelPs ravine, Mount Jura, near Taylorsville.

" Bicknell tuff."

Name applied by A. Hyatt (Geol. Soc. America Bull., vol. 3, p. 407, 1892) 

to the tuffaceous sandstone forming the upper-member of the Bicknell 

sandstone of Diller.
GEOLOGIC UNITS OF CALIFOBNIA 7

Big Blue serpentinous member.

Miocene: Southern California (Diablo Range and Coalinga district).

R. Anderson and R. W. Pack, 1915 (U. S. Geol. Survey Bull. 603). The upper member of the Vaqueros formation, locally known as the Big Blue but In this report 

called the Big Blue serpentinous member, is formed largely of small flakes of 

serpentine, which make up a fine-grained, compact, tough shale, slightly bluish 

when fresh but weathering to various shades of red, yellow, and brown, owing 

to oxidation of the iron. Locally this shale becomes sandy, but through most of 

its extent it is rc^sftrkable for being little else than a compacted mass of serpentine dust, flakes, and pebbles. With the shale are conglomerates formed 

almost entirely of serpentine boulders, the largest of which are huge blocks many 

feet in diameter. Thickness 40 to 1,000 feet. In the report on the Coalinga 

district (U. S. Geol. Survey Bull. 398, 1910) the Big Blue was tentatively included in the Santa Margarita formation. Named for exposures in the Big 

Blue Hills.

The Vaqueros sandstone being now restricted to the lower part, or Turr$- 

tella inezana zone, of the Vaqueros of earlier reports, the Big Blue, 

according to B. L. Clark, becomes a member of the overlying Turritella 

ocoyana zone and is older than Santa Margarita formation.

Bixby zone.

A petroliferous zone, about 2,400 feet thick, forming the lower part of the 

Fernando group in the Long Beach field of the Los Angeles Basin. 

Named for fact that the Shell Bixby No. 1 well has been producing 

from this sand.

Blackhawk breccia.

Pleistocene: Southern California (San Bernardino County).

A. 0. Woodford and T. F. Harriss, 1928 (California Univ. Pub., Dept. Geol. Sci. 

Bull., vol. 17, pp. 267, 279-283). Blackhawk breccia. Chiefly made up of limestone blocks, usually only a few inches or at most a few feet in diameter, but at 

mouths of Blackhawk and Miles Canyons more or less brecciated limestone, hundreds of feet across, are mapped as part of the formation, because they seem to 

be landslide blocks inextricably involved in the breccia. The basal part of the 

formation consists of alternating beds of limestone breccia and sandstone. The 

greater part of the material is spread out over the desert at the foot of the 

mountains. The formation is of land-slip origin. Thickness 100 to 600 feet. 

Includes Heights fanglomerate of Vaughan, 1922. Assigned to Pleistocene. 

Typically developed at mouth of Blackhawk Canyon.

Black Mountain basalt flow.

Tertiary or Quaternary: Southern California (western El Paso Range, 

eastern Kern County).

C. L. Baker, 1912 (California Univ. Pub., Dept. Geology Bull., vol. 7, pp. 121-142). 

Black Mountain "basalt flow. Olivine basalt, both vesicular and compact. 

Thickness more than 100 feet. Of post-Miocene Tertiary age and younger than 

Rosamond series.

C. D. Hulin, 1925 (California State Min. Bur. Bull. 95, pp. 20-61). Black Mountain 

basalt is both intrusive and extrusive. Intrudes Rosamond series and Red 

Mountain audesite. Named for widespread basalt flows on Black Mountain, 

7 miles west of El Paso Peaks, Kern County, where they unconformably overlie 

Tertiary sediments. It seems probable they are very late Pliocene or early 

Pleistocene.

Black Mountain volcanics.

Probably Upper Triassic or Jurassic: Southern California (San DiegoCounty).

M. A. Hanna, 1926 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 16, No. 7, 

pp. 187-246). Chiefly volcanic, including agglomerates, although in certain 

places sediments are. present. Contains rather massive conglomerates, quartzites, shales, massive andesitic agglomerates, trachytic and andesitic flows, and 

tuffs. All metamorphosed. Thickness more than 2,000 feet. Oldest rocks ex-
8 GEOLOGIC UNITS OF CALIFORNIA

posed in La Jolla quadrangle. Rest on intrusive rocks, and .nowhere is basement 

exposed. Unconformably overlain by Chico Cretaceous. No fossils. Well developed on Black Mountain, in northern part of La Jolla quadrangle.

Blue Canyon formation.

Mississippian: Northern California (Coifax quadrangle).

W. LIndgren, 1900 (U. S. Geol. Survey Geol. Atlas, Colfax folio, No. 66). Black 

and fissile clay slates and dark-gray fine-grained quartzitic sandstones; only 

one occurrence of conglomerate noted in the formation; a few limestone lenses 

and some chert occur in it in eastern part of area; including " a belt of gray 

or brown chert referred to as the Duncan chert." Corresponds to lower part 

of Calaveras formation. Few fossils not diagnostic, but formation assigned 

to Carboniferous. Underlies Relief quartzite. Oldest formation exposed in 

Colfax quadrangle. Named for exposures at village of Blue Canyon, Placer 

County.

According to later work by H. G. Ferguson (Am. Inst. Min. and Met. 

Bng. Tech. Pub. 211, p. 4, 1929), two formations (Tightner below and 

Kanaka above), composed of interbedded sedimentary and igneous 

rocks, are now discriminated between the Relief quartzite and the 

Blue Canyon formation.

"Blue chert series."

Devonian (?): Northwestern California (Klamath Mountains).

O. H. Hershey, 1906 (Am. Jour. Sci., 4th ser., vol. 21, pp. 58-66). A great series 

of black shales, limestones, and blue cherts, 5,000 feet thick, of which 3,000 feet 

is chert. Is presumed to be Devonian, because similar rocks elsewhere in 

Klamath region carry Devonian fossils. Is thoroughly intruded by dioritic 

and diabasic materials. Unconformably overlain by volcanic rocks. Must be 

pre-Bragdon. .Named for its most characteristic constituent, blue chert.

Bodega diorite.

Jurassic? (pre-Franciscan) : Western California (Marin County).

V. C. Osmont, 1904 (California Univ. Pub., Dept. Geology Bull., vol. 4, p. 43). 

Bodega Peninsula is made up almost wholly of this rock, which is a biotite 

diorite. The east shore of Bodega Bay, however, is entirely Franciscan. Point 

Reyes Peninsula, to the south, is composed largely of this diorite and granite. 

There are two varieties, one biotite diorite and the other quartz diorite. 

Best exposures of this diorite occur on ocean side of Bodega Peninsula, at 

south end, where it forms steep cliffs 50 to 80 feet high.

.Bodega Bay deposits.

Quaternary: Western California (Marin County).

V. C. Osmont, 1904 (California Univ. Pub., Dept. Geology Bull., vol. 4, p. 76). 

Bodega Bay deposits. At Bodega Bay similar deposits [to those described 

as Tomales Bay deposits] occur on both sides of the bay, but only in small 

patches, most of them having been removed by erosion. Near Bodega Point 

on the bay side is a remnant resting upon a wave-cut shelf just about at 

(high-water mark and extending up 113 feet above it, consisting principally

 of diorite sands and occasional pebbles showing very indistinct horizontal 

Gratification and cross-bedding. On the ocean side of the peninsula occasional

 still smaller patches, some 20 to 30 feet thick, may be seen resting upon a 

~very evenly worn diorite surface, which at a point about 3 miles south of 

ithe mouth of Salmon Creek dips gently toward the north and passes under the 

ibeach and eolian sands. On eastern side of bay is a broad, flat terrace,-'about

 one-fourth of a mile in width and some 75 to 90 feet above sea level at 

its back. In most places only a thin veneer of gravel covers this terrace, but 

.at one point on shore, at north end of bay, a remnant of gravel some 50 

feet thick rests on worn Franciscan surface, which is here only 20 feet above 

ifiea level. It is composed chiefly of Franciscan pebbles and loosely coherent 

?sands showing cross-bedding. Is somewhat distorted and dips slightly to 

jQorth.
GEOLOGIC UNITS OF CALIFORNIA 9

Bolinas sandstone.

Jurassic (?) : Western California (San Francisco region).

R. Arnold, March, 1902 (Science, new ser., vol. 15, table on p. 416). Bolinas 

sandstone (volcanics), 2,000 feet thick. A division of the Franciscan. [Shown 

in table as underlying Sausalito cherts and overlying volcanics that are 

younger than Calera limestone.]

A. C. Lawson, February, 1903 (Geol. Soc. America Bull., vol. 13, pp. 544-545). 

[Same as above.]

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

[Maps the Franciscan rocks of Bolinas Ridge, also of shore of Bolinas Lagoon 

and shore of Bolinas Bay (all in Marin County), as undifferentiated sandstones 

of the Franciscan group, with radiolarian chert lentils of undetermined horizons, but in other parts of the region the rocks between the Sausalito chert and 

the Calera limestone are mapped as the upper part of the Cahil sandstone.]

Bolsa zone.

An oil-producing zone, 600 to 800 feet thick, in the Huntington Beach oil 

field of Orange County. Consists of sands, sandy shales, and thin 

sands. Its top lies at a depth of about 1,914 feet.

Bonita sandstone.

Jurassic (?): Western California (San Francisco region).

R. Arnold, 1902 (Science, new ser., vol. 15, table on p. 416). Bonita sandstone, 

1,400 feet thick, top formation of the Franciscan. [Shown in table as overlying San Miguel cherts and unconformably underlying Knoxville.]

A. C. Lawson, 1903 (Geol. Soc. America Bull., vol. 13, table on pp. 544-545). 

[Same as above.]

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Massive, obscurely bedded sandstone of dark greenish-gray color and medium 

texture, with subordinate amounts of shale and conglomerate. Thickness 

about 1,400 feet. Top formation of Franciscan group. Conformably overlies 

Ingleside chert.

Named for exposures at Point Bonita, on the north shore of the Golden 

Gate, San Francisco County.

Booth zone.

A petroliferous zone, about 270 feet thick, included in the Alamitos zone 

of the Fernando group. Named for San Martinez Booth No. 1 well, 

in Long Beach field, Los Angeles Basin.

Bouquet Cafion breccia.

Probably Miocene: Southern California (30 miles north of Los Angeles).

A. 0. Woodford, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, 

No. 7, p. 212). "Bouquet Canon breccia. There may well be correlatives of 

the San Onofre [" breccia facies of Temblor formation"] north of the San 

Gabriel Mountains. A suggestion of this is given by a specimen of fine schist 

breccia furnished by Prof. F. P. Vickery and Mr. S. W. Harris. This is from 

lower Bouquet CaSon, 30 miles north of Los Angeles and 5 miles northeast 

of Saugus. It may be Miocene. The rock is made up of 1-4 cm. fragments of 

white quartz, quartz-muscovite schist, hornblende-epidote schist (hornblende 

close to karinthine), etc., in a carbonate cement, almost without fine clastic 

grains."

Bragclon formation.

Mississippian: Northwestern California (Klamath Mountains region).

0. H. Hershey, 1901 (Am. Geologist, vol. 27, pp. 236, 238). Upper slates or 

Bragdon formation. The latest of the formations included in the " Auriferous 

Slate series/' Consists of 2,000 feet of alternating thin-bedded slates and 

thick-bedded blue quartzites; no limestone. Similar to Mariposa slates. TentaUvely assigned to Jurassic.
10 GEOLOGIC UNITS OF CALIFORNIA

According to J. S. Diller (U. S. Geol. Survey Geol. Atlas, Folio 138, 1906> 

the Bragdon formation is 2,900 to 6,000 feet thick in the Redding 

quadrangle, underlies the Baird formation, unconformably overlies 

the Kennett formation, and is of Mississippian age.

Named for exposures in Bragdon Gulch and vicinity of Bragdon, Weaverville quadrangle.

Bridalveil granite.

Probably Cretaceous: Northern California (Yosemite region).

H. W. Turner, 1899 (Jour. Geology, vol. 7, p. 154). Bridal Veil granite. Finegrained white granite, occurring in drainage of Bridalveil Creek, on Horse Ridge, 

and at many other points in Yosemite Park.

Forms brink of Bridalveil Fall.

Briones sandstone.

Miocene (upper) : Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Prevailingly light-colored to whitish well-washed sandstone, in some places pebbly 

or conglomeratic, and in general of coarser texture than the lower sandstones of 

the Monterey group, of which it is the top formation. Thickness 2,300 feet. 

Very fossiliferous. [Fossils listed.] Includes the nonpersistent Hercules shale 

member. Overlies Rodeo shale and unconformably underlies San Pablo formation. Named for exposures in Briones Hills, Contra Costa County.

The fauna of the Briones sandstone is now generally considered to be 

younger than the Monterey fauna, and the formation is now excluded 

from the Monterey group.

Brock shale.

Upper Triassic: Northern California (Redding quadrangle).

J. S. Diller, 1906 (U. S. Geol. Survey Geol. Atlas, Redding folio, No. 138). "The 

Brock shale conformably overlies the Hosselkus limestone in Brock Mountain, 

whence the name, and has a thickness of about 400 feet. In the lower 300 feet 

or more adjoining the limestone the shales are dark, somewhat calcareous, and 

frequently contain HaloMa. Above these come sandy shales, gray and reddish in 

color and characterized locally by Pseudomonotis subdrcularis." Is overlain, 

probably unconformably, by the Modin formation. [Is approximate equivalent of 

Swearinger slate.]

Brown zone.

A petroliferous zone, about 250 feet thick, in the Fernando group of the 

Long Beach field, Los Angeles Basin. Lies lower than Alamitos zone 

and higher than Bixby zone. Named for fact that Petroleum Midway 

Brown No. 1 well is thought to be the discovery well of this zone.

" Bully Hill rhyolite."

Jurassic (?) : Northern California (Redding quadrangle).

J. S. Diller, 1906 (U. S. Geol. Survey Geol. Atlas, Redding folio, No. 138). In Bully 

Hill region [Shasta County] the rhyolite Is arranged in flows alternating with 

tuffs dipping southeastward beneath the Pit shales, but in places it cuts the 

lower portion of the Pit shales and envelops its fragments. For convenience all 

the rhyolites erupted in the Redding quadrangle during the deposition of the Pit 

shales are included under the term Bully Hill rhyolite, though they represent a 

considerable range of time. Bedded tuffs, composed largely of crystal fragments 

of quartz and feldspar, with a smaller proportion of glass and pumice particles 

replaced by quartz, are common among the Pit shales and are locally associated 

with sheets of rhyolite. Thickness about 500 feet.

Later work by L. C. Graton (U. S. Geol. Survey Bull. 430, pp. 81-85, 1910) 

proved this formation to be intrusive alaskite porphyry and the same as 

the so-called " Balaklala rhyolite." Both geographic names have therefore been discarded as unnecessary. The rock cuts formations as young 

as the Pit shale (Middle and Upper Triassic).
GEOLOGIC UNITS OP CALIFORNIA 11

" Bully Hill volcanics."

J. S. Diller, 1905 (Am. Jour. Sci., 4th ser., vol. 19, pp. 380-385). Lavas interstratified with tuffs and shales. Of late Carboniferous and early Triassic age.

Butauo sandstone.

Oligocene? (may be Eocene) : Southern California (Santa Cruz Mountains).

J. C. Branner, J. F. News'om, and R. Arnold, 1909 (U. S. Geol. Survey Geol. Atlas, 

Santa Cruz folio, No. 163). Massive brown and buff sandstones with conglomerate at base. Thickness about 2,100 feet. No fossils found. Conformably 

underlies San Lorenzo formation, and believed to overlie Eocene limestone unconformably, but sequence is concealed.

Named for exposures on Butano Ridge, San Mateo County.

Butte gravels.

Eocene (middle) : Northern California (Sutter County).

Howel-Williams, 1929 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 18, pp. 112- 

129). Butte gravels. Coarse gravels, composed of rounded, chiefly very siliceous pebbles, with sandy intercalations and thin beds of massive sandstone and 

siliceous limestone. Thickness 450 to 1,200 feet.- Overlie White lone sands, 

usually with minor disconformity, but occasionally with erosion unconformity. 

Are overlain by Sutter formation, in some places with sharp contact, in other 

places almost insensible gradation. Fossils 700 feet above lone sands are assigned by B. L. Clark to Meganos (middle Eocene) age. Present at Marysville 

Buttes.

" Button beds."

Miocene: Southern California (Kern County).

F. M. Anderson, 1905 (California Acad. Sci. Proc., 3d ser., vol. 2, p. 170). The 

first sandy beds1 below the Monterey shale at Temblor. Included in Temblor 

beds. Thickness 100 feet. Named for the great numbers of small discoidal 

sea urchins (Astrodapsis) that characterize them. [See also under Temblor 

formation. ]

Cabezon fanglomerate.

Quaternary: Southern California (San Bernardino Mountains).

F. E. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 9, 

pp. 344, 387-392, map). A fanglomerate deposited in Bear and Holcomb 

Valleys. Differs from older Coachella fanglomerate in being more uniform and 

massive, of yellowish color, and in lying nearly horizontal. The largest area 

in Bear Valley is the broad flat between Rathbone Creek and Erwin Lake, 

where material is aimost wholly unsorted angular and subangular quartzite 

brought down from Sugarloaf Mountain to southeast. Holcomb Valley is 

nearly surrounded by flat ridges of fanglomerate. Those on the south and 

east sides are particularly conspicuous and consist of limestone, granite, and 

quartzite from surrounding hills. The fanglomerate in Bear and Holcomb 

Valleys is only a local representative of a widespread deposition during the 

third cycle of erosion. The Cabezon fanglomerate is older than the Heights 

fanglomerate and younger than the Coachella fanglomerate.

Named for Cabezon Station, Riverside County.

Cable formation (or lake beds).

Quaternary (?) : Southern California (Kern County).

A. C. Lawson, 1906 (California Univ. Pub., Dept. Geology Bull., vol. 4, pp. 431- 

462). Cable formation (also Cable lake beds). Fresh-water lake beds, of wellstratified limestones, cherts, gravels, clays, and fine light-colored volcanic tuff. 

Named for town of Cable, Kern County. Older than Tehachapi formation and 

younger than Tank volcanics.

Cache Lake beds.

Pliocene: Northern California (Lake County).

G. .F. Becker, 1888 (U. S. Geol. Survey Mon. 13, p. 219). Fresh-water gravels, 

sand, and calcareous beds .of Pliocene age, 1,000 feet thick. Occur east of 

Clear Lake, about the north fork of Cache Creek. Deposited in extinct Cache 

Lake, which overlapped Clear Lake.

17462 31 2
12 GEOLOGIC UNITS OF CALIFOBNIA

 actus granite.

Probably late Jurassic: Southern California (San Bernardino Mountains). 

F. E. Vaugban, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 9,

pp. 344, 364-365, map). Medium coarse-grained intrusive granite, pinkish

to yellowish gray.

Named for Cactus Flat, San Bernardino .County.

 Cahil sandstone.

Jurassic (?) : Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Prevailingly massive, obscurely bedded sandstone of dark greenish-gray color 

and medium texture. Includes lenses of pebbly conglomerate and beds of dark 

shale. Includes, 500 feet above base, a conspicuous foramlniferal limestone 

the Calera limestone member 60 feet thick, which is overlain by 2,000 feet 

of beds belonging to the Cahil formation. On the summit of Fifleld Ridge a 

thin lens of obscurely fossiliferous impure limestone occurs in the 0Cahll sandstone several hundred feet above the Calera limestone. This limestone Is apparently not persistent and probably nowhere exceeds 10 feet in thickness. 

Thickness of Cahil sandstone approximately 2,560 feet. Basal formation of 

Franciscan group. Underlies Sausalito chert.

Named for exposures on Gahil Ridge, San Mateo County.

 Calaveras formation (also group).

Mississippian: Northern California (Calaveras and neighboring counties).

H. W. Turner, 1893 (Am. Geologist, vol. 11, pp. 3Q7-324, 425). "The term 

' Calaveras formation ' as used by the United States Geological Survey on the 

geological maps of the Gold Belt [then in preparation] includes all of the 

Paleozoic sedimentary rocks of the Sierra Nevada." Is characterized by large 

masses of associated greenstone. Includes slate, conglomerate, and limestone, 

associated with igneous rocks of apparently the same age as the inclosing 

sedimentary rocks. Unconformably underlies the Mesozoic Mariposa slates. 

" So far as yet known is chiefly lower Carboniferous, but may extend down 

into the Devonian. It is not intended to include In it the Silurian beds 

described by Mr. Diller nor the upper Carboniferous strata of Genesee Valley, 

called by Mr. Diller the Robinson beds."

Two of the United States Geological Survey maps of the Gold Belt referred 

to by Turner were published in 1894 (Folios 3 and 11), and others followed later. These folios describe the Calaveras formation as consisting 

of a conformable series, 4,000 feet or more thick, of black micaceous clay 

slate, argillaceous schist, quartzite, chert, and mica schist, with lenses 

of limestone and some beds of conglomerate, all associated and in part 

interbedded with igneous rocks. Is lower formation of the "Auriferous 

slate series."

Named for prominent development in Calaveras County.

<Calera limestone member.

Jurassic (?): Western California (San Francisco region).

R. Arnold. 1902 (Science, new ser., vol. 15, table on p. 416). Calera limestone, 

foraminiferal, 60 feet thick. [Shown in table as overlain by volcanics that 

are older than Boliuas sandstone and underlain by volcanics that are younger 

than Pilarcitos sandstone.]

A. C. Lawson, 1903 (Geol. Soc. America Bull., vol. 13, table on pp. 544-545). 

[Same as above.]

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Calera limestone member. Gray compact foraminiferal limestone resembling 

lithographic limestone and containing lenses of chert. Occurs in lower part 

of the Cahil sandstone, the basal formation of the Franciscan group. Thickness averages about 60 feet.

Named for exposures in the sea cliffs at the lower end of Calera Valley, 

San Mateo County.

41 California sandstone." See " San Francisco sandstone,"

 " Campan group " and " Campan series." See Campus formation.
GEOLOGIC UNITS OP CALIFORNIA 13

Oampito sandstone.

Lower Cambrian: Eastern California (Inyo Range).

B. Kirk, 1918 (U. S. Geol. Survey Prof. Paper 110). Chiefly sandstone, which on 

fresh fracture is a dense flne-grained grayish rock with conspicuous fine dark 

lines that indicate highly complex cross-hedding. Weathers reddish hrown to 

dark purplish red. Associated with this sandstone are some bands of very 

dense lighter-colored quartzitic sandstone separated hy thin layers of siliceous 

elate, which occur as partings in the dense sandstone. Upper third of formation is somewhat more slaty and includes zones curiously speckled by ferric 

oxide. Remarkable cross bedding at several horizons. Rests unconformahly 

on Deep Spring formation and appears to grade into overlying closely related 

Silver Peak group, the upper. limit of the Campito being placed at the lowest 

horizon at which fissile calcareous shales and fairly pure masses of limestone 

appear. Thickness of formation 3,200 feet. Named for prominent exposures 

on Campito Mountain.

Oampus formation.

Pleistocene: Western California (San Francisco region).

A. C. Lawson and C. Palache, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 

2, p. 398, map). Campan series. Interbedded fresh-water deposits and volcanic lavas and tuffs. Thickness 800 feet. Includes rhyolite tuff and other 

tuffs, agglomerate, conglomerates, andesites, basalt flows, clays, some sandstone and limestone, and the Pie Knob andesite. Unconformably overlies 

Berkeleyan series. Named because of its occurrence within the limits of the 

university campus, Berkeley [on a hill behind the area now covered with 

buildings].

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Campus formation, originally named Campan. Rests unconformably on Moraga 

and Siesta formations of the Berkeley group.

Oamulosj formation.

C. [R.] Keyes, 1925 (Pan-Am. Geologist, vol. 43, p. 316). [Name proposed for lower 

part of Arnold's Fernando formation, or probably for the same beds that Kew 

in 1921 named Pico formation.]

Named for the railway hamlet of Camulos, a few miles directly west of 

Saugus Junction, in Santa Clara Valley.

Oantua sandstone member.

Eocene: Southern California (north of Coalinga region).

R. Anderson and R. W. Pack, 1915 (U. S. Geol. Survey Bull. 603, pp. 33, 59-63, 

map). A huge lens of massive medium to fine grained gray concretionary sandstone and interbedded clay shale that forms the lower and major part of the 

Martinez (?) formation within a small area. Maximum thickness at least 

4,500 feet. Rests unconformably on Moreno formation. Is overlain by and in 

places grades laterally into dark clay shale that composes the rest (400 to 

1,100 feet) of the Martinez (?) formation. Named for fact that it reaches its 

greatest development at the head, of the western branches of Cantua Creek, 

Fresno County.

According to B. L. Clark, 1921 (Jour. Geology, vol. 29), these beds belong to 

his Meganos group and are younger than the Martinez.

<Cape Horn slate.

Mississippian: Northern California (Coifax quadrangle).

W. Lindgren, 1900 (U. S. Geol. Survey Geol. Atlas, Colfax folio, No. 66). The 

characteristic rocks are fissile typical clay slates, almost black when fresh and 

weathering to a gray or silvery-white color. Small limestone lenses1 are found 

below Cape Horn, in Bear River Canyon west of Dutch Flat, and in the 

canyon of the South Fork of Yuba River south of Relief; they are ordinarily 

only a few feet thick. Meager fossils not diagnostic as to age. The formation corresponds to part of Calaveras formation and Is assigned to the Carboniferous. Overlies Relief quartzite and underlies Delhi formation. Named for 

occurrence at Cape Horn, overlooking North Fork of American River, in Placer 

County.
14 GEOLOGIC UNITS OP CALIFORNIA

Capistrano formation.

Upper Miocene (?) : Southern California (between Santa Ana and Oceanside).

A. 0. Woodford, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 7,. 

pp. 169, 184, 216-217). " Capistrano formation. The light-colored Monterey 

shale is everywhere overlain by thin-bedded dark-gray shale, the contact being 

nearly or quite conformable. This shale and the associated sandstone cover 

a large synclinal area centering about Capistrano. Mica is prominent in the 

gray shale, and Foraminifera and other organisms are common both in it andin the sometimes abundant small limestone nodules or lenses. The shale rarely 

contains beds of fine sandstone, which is usually high in quartz and sometimes 

highly feldspathic. At the top of the formation this sandstone predominates. 

Occasionally the gray shale has white partings which resemble the Monterey. * * * The Capistrano beds may properly belong with the Monterey, 

but because of their different lithology and the local development of breccia at 

or near their base, they are here distinguished as a separate formation. Theshales are practically identical with those which unconformably overlie thpMonterey in the near-by Huntington Beach oil field, and which are commonl.i 

called Fernando Pliocene." Thickness 1,200 feet. Classified as upper Miocen< 

(?), as unconformably (?) overlying Monterey shale, and as unconformably 

overlain by San Mateo formation (Pliocene?). Suggests correlation with San 

Pablo formation (upper Miocene), but "fossil evidence is inconclusive," and1 

the beds may be lower Pliocene. [Mapped.]

Named for development around Capistrano, Orange County.

" Caribou formation."

Mississippian: Northern California (Plumas County).

J. S. Diller, 1892 (preliminary proof-sheet edition of Lassen Peak folio of U. S. 

Geol. Survey Geol. Atlas). Caribou formation. Northwest of Caribou Bridge 

[Plumas County, in southeastern part of Lassen Peak quadrangle] a series of 

slates and sandstones, with a heavy mass of fossiliferous limestone, forms for 

several miles the crest of the divide between Mosquito and Yellow Creeks. 

The limestone is of Carboniferous age and one of the most widely distributed 

strata yet recognized by fossils in northern California. It forms a prominent 

hill near Bass's ranch on Stillwater and on McCloud Biver opposite the United 

States fishery, as well as near Gazelle, northwest of Mount Shasta. Is younger 

than Grizzly formation and older than Spanish formation.

J. P. Smith, 1916 (California State Min. Bur. Bull. 72, pp. 28, 29). "The Caribou 

limestone of the Taylorsville region of Pluraas County, with Fustilina 

oylindrica, is mapped under the Carboniferous heading."

In the published Lassen Peak folio (No. 15) these rocks were mainly

included in the Calaveras formation. 

Carmelo series.

Eocene (? ) : Western California (Carmelo Bay region, southwest coast of 

San Mateo County).

A. C. Lawson, 1893 (California Univ. Pub., Dept. Geology Bull., vol. 1, pp. 1-59). 

Several hundred feet of thick-bedded conglomerates of dark color and thinbedded tawny sandstones with some argillaceous shales. No fossils at Carmelo 

Bay, but the series appears to be identical with the coal-bearing sandstones of 

Malpaso Canyon, about 2 miles distant, which carry coal and appear, from the 

fragmentary fossils found, to be of Tejon (Eocene) age. Overlain unconformably by Miocene Monterey series, and unconformably underlain by Santa 

Lucia granite.

H. J. Hawley .(Geol. Soc. America Bull., vol. 28, p. 225, 1917) and P. D. Trask 

(California Univ. Pub. Dept. Geol. Sci. Bull., vol. 16, p. 142, 1926) regard these 

rocks as of Chico age.

Carquinez (spelling adopted by U. S. Geographic Board). See " Karquinez." 

" Carrizo " formation.

Miocene (lower and middle or upper) : Southern California (Imperial and 

San Diego Counties).

J. P. Smith, 1910 (Jour. Geology, vol. 18, No. 3, chart opp. p. 226). Carrizo 

formation, sandstones with Pecten carrteoensis and P. cerrosenste. Of upper 

Miocene age. Older than San Diego.
GEOLOGIC UNITS OF CALIFOKNIA 15

W. S. W. Kew, 1914 (California Univ. Pub., Dept. Geology Bull., vol. 8, pp. 39-46, 

map). [Called Carrizo formation on map; no text heading; throughout description called Carrizo formation and Carriso Greek formation.] At type locality 

divided, on lithologic and biologic grounds, into lower division and upper division, both of which are well exposed there, but only remnants remain to 

indicate their former extent. The upper division is about 2,000 feet thick 

in Carrizo Valley and consists of fine-grained muddy sandstone and shale. 

It extends north along west side of Salton Sea to Santa Rosa Mountains, which 

is the most northerly limit of the beds in this region. The lower division 

consists of about 200 feet of more or less coarse arkosic sandstone, locally 

conglomeratic, underlain by a coarse angular conglomerate of subaqueous origin 

. and reddish color. The total thickness of the formation is probably 2,500 feet. 

It rests on the eroded surface of the basement complex or, in places, on a flow of 

andesite.

J. P. Buwalda and W. L. Stanton, 1930 (Science, new ser., vol. 71, pp. 104-106). 

Oarriso formation is Miocene or lower Pliocene.

W. P. Woodring, 1931 (Carnegie Inst. Washington Pub. 418, pp. 1-25). "Carrizo 

formation " of Kew (preoccupied) included the marine Imperial formation (late 

lower Miocene) and at least the basal part of the overlying nonmarlne deposits 

of upper or middle Miocene age, here named Palm Spring formation.

Name is preoccupied. See also " Ca/rrizo Creek beds" and Imperial

formation. 

Named for exposures in broad valley of Carrizo Creek immediately north

of Coyote Mountain, Imperial County.

"'Carrizo Creek beds."

Miocene (lower and middle or upper): Southern California (Imperial 

County).

C. R. Orcutt, 1890 (California State Min. Bur. Tenth Ann. Rept., p. 915). Carrieo 

Creek oyster teds. Shales and clays of light-brown or pinkish color, through 

which Carrizo Creek has been cut. Tentatively assigned to Miocene. [Inadequate definition.]

T. W. Vaughan, 1917 (U. S. Geol. Survey Prof. Paper 98, pp. 355-386). "The 

fauna of Carrizo Creek is related to Pliocene and post-Pliocene faunas of 

Florida and the West Indies and can scarcely be older than lower Pliocene."

W. S. W. Kew, 1920 (U. S. Geol. Survey Press Bull. 447, June, 1920). "These beds 

are known as the Carrizo Creek beds, from their extensive outcrops on Carrizo 

Creek, but. can also be seen along the west side of the valley around Coyote 

Mountain, at Yuha Buttes, and at Superstition Mountain, as well as at San 

Felipe Valley, west of the Salton Sea, and at places north of San Gorgonio Pass, 

in Riverside County. Remnants of these beds rest on the crystalline rocks at 

elevations as high as 2,000 feet above the present level of the valley. The 

Carrizo Creek beds consist mainly of tan-colored well-bedded sandy shales or 

silts, but include small amounts of sandstone and clayey shale. At some places, 

as on Carrizo Creek, they contain numerous marine fossils, the remains of 

animals that lived probably in Pliocene time."

See also " Carrizo " formation, W. S. W. Kew, 1914.

In 1926 (California Acad. Sci. Proc., 4th ser., vol. 14, p. 434) G. D. Hanna 

named these beds Imperial formation. In 1931 (Carnegie Inst. Washington Pub. 418, pp. 1-25) W. P. Woodring divided them into Palm 

Spring formation above (nonmarine) and Imperial formation (restricted) below (marine).

Carson Creek formation.

Age (?): Northern California (Calaveras County).

F. A. Moss, 1927 (Eng. and Min. Jour., vol. 124, pp. 1010-1011). In the Carson Hill 

area the oldest rocks constitute a sedimentary and volcanic series at least 5,000 

feet thick, to which I have given the local name of the " Carson Creeh formation." It is best exposed west of Carson Hill. Sediments in lower part are 

chiefly conglomerates with a few thin partings of sandstone. Near bottom is a 

series of hornblende-dacite lava flows and rhyolite tuffs 900 to 1,700 feet thick. 

Upper part of formation is slate, mostly tuffaceous, with several lenses of limestone and' beds of andesitic crystal tuff. At top Is1 a thick'and massive bed of 

andesitic tuff, in places containing much admixed sediment.
16 GEOLOGIC UNITS OF CALIFORNIA

Catalina facies of Franciscan series.

Jurassic (?): Southern California (Catalina Island).

A. 0. Woodford, 1924 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 3). 

OataKna metamorpMo fades of the Franciscan series. [Mapped.] " On Catalina 

Island off the coast of southern California, and in San Pedro Hill on the adjacent mainland, are areas of unusual metamorphic rocks similar to those forming 

part of the Franciscan series farther north. These rocks are schistose, are of 

variable grain, and made up largely of various combinations of the minerals 

quartz, albite, muscovite, chlorite, epidote, glaucophane, crossite, actinolite, and 

lawsonite. * * * The new term Catalina metamorphic facies indicates the 

absence of unmetamorphosed materials. * * * The Catalina facies is probably unconformably beneath the Chico, and it has a close lithologic resemblance' 

to the schists of north Berkeley and the Tiburon Peninsula mapped by A. C. 

Lawson (1914) as Franciscan. These facts taken together suggest correlation* 

with the Franciscan series. The quartz schists would then be metamorphosed.' 

radiolarian cherts, the quartz-albite schists former arkoses derived from a region, 

of quartz diorites, and the remaining types former basic igneous rocks. Soda> 

basalts of the type analyzed by Ransome from the Point Bonita Franciscan maybe represented. At this time, however, the correlation can be made only in themost general sense, indicating merely that these rocks belong to a great and perhaps heterogeneous group now called the Franciscan series. It may be that 

these metamorphic rocks belong to an ancient group which extends northward 

unconformably beneath the typical Franciscan."

A. 0. Woodford, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 7, pp. 

163, 172, 225). Oatalina fades of Franciscan series. Half of Catalina Islands 

is a complex of albitic, amphibolic, chloritlc schists, quartz schist, serpentine, etc.,, 

and there is a small area of similar rocks exposed in San Pedro Hill on the 

mainland. They are especially characterized by abundance of albite and by/ 

presence of the unusual minerals glaucophane, crossite, and lawsonite.

Catalina schist breccia. . . Lower (?) .Miocene: Southern California (southeast end of Catalina' 

Island).

A. 0. Woodford, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 7,. 

pp. 211-212). " Gatalina scMst breccia. At the southeast end of Catalina 

Island small areas of schist and quartzite breccia with sandy .matrix are involved in the volcanic rocks. As indicated by W. S. T. Smith, it is difficult to> 

determine whether these are contemporaneous with the volcanics or, inclusions 

in them. The breccia blocks are sometimes exclusively subrounded quartzite and 

gray porphyry. Sometimes glaucophane and other schists are also present, 

making a rock very similar to the San Onofre sandy breccia." [This description is under the center heading " Doubtful correlatives of the San Onofrefacies " of the Temblor formation of Monterey series.]

Cathedral Peak granite.

Probably Cretaceous: Yosemite National Park.

F. C. Calkins, 1930 (U. S. Geol. Survey Prof. Paper 160, pp. 126-127, map). A. 

- coarsely prophyritic rock, in which biotite is more abundant than hornblende.. 

The distinguishing feature of the granite is that it contains unusually large' 

phenocrysts of feldspar. Included in Tuolumne intrusive series, in which .it isnext younger than the Half Dome quartz monzonite. and next older than the 

Johnson granite porphyry.

Named from fact that it composes Cathedral Peak and most of the Cathedral) 

group or range in Yosemite National Park.

Cedar formation. ;

Upper Triassic: Northern California (Lassen Peak region).

J. S. Diller, 1892 (preliminary proof-sheet edition of Lassen Peak-folio of U. S, 

Geol. Survey Geol. Atlas) and 1895 (published Lassen Peak folio, No. 15). 

Although there are slates and sandstones, with occasional traces of conglomerate, the principal stratum of the Cedar formation is limestone, which forms 

conspicuous ledges on the road a few miles west of Buzzard's Roost. This 

limestone is rich in Triassic fossils, which clearly show it is the same horizon
GEOLOGIC UNITS OF CALIFORNIA 17

as the Hosselkus limestone of Genesee Valley. Named for exposure on Cedar 

Creek, along the toll road between Redding and Round Mountain, where it is 

overlain by the Bend formation.

H. W. Turner, April, 1894 (Am. Geologist, vol. 12, pp. 229-249). The Cedar formation includes the Hosselkus limestone and underlying slates [meaning the 

Swearinger slate, which is now known to overlie the Hosselkus limestone].

Cedarville series.

Miocene: Northeastern California (Modoc County).

R. J. Russell, 1928 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 17, No. 11, pp. 

402-416, map). Qedarville series. A series of andesitic rocks, at least 7,500 

feet thick, divided into (1) Upper Cedarville (andesitic tuffs, agglomerates, intercalated flows, and about 5 per cent of nonvolcanic sediments) ; (2) andesitic 

lava flows 150 to 500 feet thick; and (3) Lower Cedarville (3,700 feet of andesitic agglomerates, tuffs, conglomerates, intercalated flows, and about 5 per cent 

of nonvolcanic sediments). The Upper Cedarville contains fossil flora considered 

by Chaney to be of Mascall (Upper and Middle Miocene) age. [Mapped over 

large part of Warner Range, west of Cedarville.]

Centinela gravels.

Pleistocene: Southern California (Baldwin Hills, Los Angeles County).

A. J. Tieje, 1926 (Am. Assoc. Petroleum Geologists Bull., vol. 10, No. 5, p. 510). 

"The [post-Palos Verdes] alternating [fresh-water] blue-clay and gravel beds, 

however, of trench 10 may be correlated with a series of marine gravels which 

carry a fauna of still more warn>water aspect than that of the Palos Verdes 

strata and which may be tentatively styled the Centinela gravels, since they were 

exposed south of Centinela Creek, in trench 6. On the other hand, these Centinela gravels may represent a new submergence of the Baldwin Hills region."

Chanac formation.

Pliocene: Southern California (Tejon Hills, Fresno County).

J. C. Merriam, J. P. Buwalda, and B. L. Clark, 1916 (California Univ. Pub., Dept. 

Geology Bull., vol. 10, pp. 111-115). Chanac formation. Mammal-bearing beds, 

400 to 600 feet thick, apparently of terrestrial origin. Consist of angular sanda 

and coarser angular materials; the particles mainly rhyolitic, and display white, 

yellow, and striking reddish-brown colors in exposures; not sharply bedded. 

Should be termed fanglomerates. [Fossils described.] Of early Pliocene or 

latest Miocene age. In southern part of Tejon Hills the Chanac fanglomerates 

rest on old crystalline rocks without observed discordance. Exposed along 

Chanac Creek.

H. W. Hoots, 1929 (U. S. Geol. Survey Bull. 812, pp. 275, 291). Ohanao formation is 

equivalent to Tulare, Etchegoin, and Jacalitos formations but is geographically 

separated from them.

Chico formation (also gyoup) .

Upper Cretaceous: California and Oregon.

W. M. Gabb, 1869 (California Geol. Survey Paleontology., vol. 2, p. xiv, as reported 

by J. D. Whitney from an unpublished paper by Gabb, and footnote by Gabb on 

p. 129). One of the most extensive and important members of the Pacific coast 

Cretaceous. Is extensively represented in Shasta and Butte Counties; also in 

foothills of Sier.ra Nevada as far. south as Folsom; on eastern face of Coast 

Ranges bordering Sacramento Valley; at Martinez; and in Oristamba Canyon, in 

Stanislaus County. It includes all of the known Cretaceous of Oregon and the 

extreme northern portion of California and is the coal-bearing formation of Vancouver's Island. It underlies Martinez group and overlies Shasta group, but the 

Martinez group " may eventually prove to be worthy of ranking only as a subdivision of the Chico group." Typical localities are Chico Creek [Butte County, 

Calif.], Pence's ranch, and Tuscan Springs.

The Chico rocks consist of sandstones, shales, and conglomerates of marine 

origin, having a maximum thickness of 21,000 feet and characterized by 

an Upper Cretaceous fauna. In the Diablo Range the Chico is of very 

great thickness and becomes a group, divided into Moreno formation, 

above and Panoche formation below.
18 GEOLOGIC UNITS OF CALIFORNIA

 " Chico-Tejon series."

A term introduced by C. A. White (U. S. Geol. Survey Bull. 51, pp. 11-14, 

1889) to include all the Tipper Cretaceous and Eocene rocks of California, because they were then believed to constitute an unbroken series of 

sediments without unconformities, but they are now known to contain 

several unconformities.

Cierbo group.

Miocene (upper) : Western California (Mount Diablo region).

B. L. Clark, 1921 (Jour. Geology, vol. 29, pp. 586-614). "The use of the name San 

Pablo for the upper Miocene series of deposits on the west coast makes it necessary to dispense with the term San Pablo within the group. The name Cierbo 

is therefore used in this paper in referring to the middle group of the San Pablo 

series. The type section of the Cierbo is in the south side of the CaSada del 

Cierbo, near Carquinez Straits." These marine beds are recognized only in the 

general region of San Francisco Bay, where they lie disconformably below the 

Santa Margarita group and rest disconformably on the Briones group.

Same as San Pablo formation.

Olaremont shale.

Miocene (middle) : Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Bituminous shale. In Sobrante anticline it is in part soft and distinctly shaly 

or chalky and in places contains a large admixture of fine detrital material, but 

in Berkeley Hills it is notably cherty, consisting of beds of hard flinty chert alternating at regular intervals with partings of shale. Thickness 250 to 1,000 feet. 

A formation of Monterey group. Underlies Oursan sandstone and overlies 

Sobrante sandstone. Named for exposures on Claremont Creek, Concord quadrangle.

Olear Creek greenstone.

Mississippian(?) : Northwestern California (Klamath Mountains region).

0. H. Hershey, 1901 (Am. Geologist, vol. 27, pp. 226, 233, 238). The foundation 

rock of the basin of Trinity River between Trinity Center and Lewiston, the 

Trinity Mountains, and the ridges eastward to the Sacramento River. Provisionally assigned to the Jurassic. Is made up of a variety of deposits of a volcanic 

nature, but all having something in common, so that it appears over wide areas 

as a massive flne-grained dull-green rock. Much of it is of a detrital character, 

chiefly diabasic tuffs and ashes, although in places it is brecciated and occasionally it has a conglomerate structure. In large part is extrusive. Was deposited 

 on land. Thickness more than 1,000 feet. Is associated with Bragdon slates 

[Mississippian], Rests unconform-ably on Devono-Carboniferous rocks.

Probably named for exposures on or near Clear Creek, Shasta County.

Clear Creek series.

Mississippian (?): Northwestern California (southern part of Klamath 

Mountains).

0. H. Hershey, 1903 (Am. Geologist, vol. 31, pp. 231-245). Volcanic materials, 

such as andesite and rhyolite lavas and tuffs, intruded by dikes of diorite, 

diabase, and rhyolite porphyry, all altered. Thickness 200 to 2,000 feet. 

Associated with Bragdon formation [Mississippian].

Clear Creek volcanic series.

Triassic (?) : Northwestern California (Trinity and Shasta Counties).

O. H. Hershey, 1904 (Am. Geologist, vol. 33, pp. 248-256, 347-360). Lavas and 

tuffs, which grade into the overlying Pit shales by interstratiflcation. Assigned 

to the Triassic.

According to J. S. Diller (Am. Jour. Sci., 4th ser., vol. 19, pp. 380-385, 

1905) the Clear Creek volcanics of Hershey are pre-Bragdon and in part 

at least pre-Middle Devonian.
GEOLOGIC UNITS OF CALIFORNIA 19

Qlear Lake sediments.

Pleistocene: Northern California (Lake County).

W. H. Ball and G. D. Harris, 1892 (U. S. Geol. Survey Bull. 84, pp. 201-202). 

Tbe body of water in which these Cache Lake beds were laid down overlapped 

the area at present occupied by Clear Lake, with which Dr. G. F. Decker 

shows its geologic history has fraen continuous. The later andesite overlies 

the Cache Lake deposits and also underlies the Clear Lake sediments.

Clipper Gap formation.

Mississippian: Northern California (Coifax quadrangle).

W. Lindgren, 1900 (U. S. Geol. Survey Geol. Atlas, Colfax folio, No. 66). A 

highly compressed sequence of black clay slates and dark argillaceous sandstones. Bodies of limestone abundant but usually lenticular. Bluish or grayish chert is also common and so closely connected with the limestone as to 

suggest strongly its derivation from that rock by a process of siliciflcation. 

Contains lower Carboniferous fossils. Corresponds to upper part of Calaveras 

formation. Overlies Delhi formation. Is top formation of Carboniferous age 

in area. Named for exposures at village of Clipper Gap, Placer County.

Coachella fanglomerate.

Miocene (middle or upper): Southern California (San Bernardino Mountains).

F. E. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 9, 

pp. 344, 386-387, 391, map). Ooaohella fanglomerate. A. clastic rock having 

all characteristics of a fanglomerate. For most part the fragments are angular and show little sorting, but material varies somewhat throughout the 

mass. Greater part of mass is light-gray and dark purplish-gray, rather 

persistent coarse gravel and subangular polygenetic pebbles 2 inches to a 

foot in diameter, probably derived from the old rocks to north. In places 

it consists mostly of sharply angular fragments varying in size up to 3 feet 

across. The fragments are of porphyry, granite, and, largely, basalt. To the 

east this fanglomerate dips beneath more recent (Cabezon) fanglomerate, which 

differs from it in being more uniform and massive, of yellowish color, and in 

lying nearly horizontal. The Coachella fanglomerate rests on old schists and 

gneisses. Is younger than Deep Canyon fanglomerates.

Named for Coachella Valley, Riverside County, near which it occurs.

Coahuila silt.

Pleistocene: Southern California (Imperial County).

G. D. Hanna, 1926 (California Acad. Sci. Proc., .4th ser., vol. 14, No. 18, p. 435). 

" The Yuha Reefs are followed by an enormousi thickness of silt deposited in 

the fresh waters of the ancient Lake Coahuila, an appropriate name for which 

is the ' Coahuila silt.' It is exposed where the San Diego-El Centro highway 

crosses New River, about a mile west of El Centro. The total thickness of 

these silts is not known, but they contain fresh water fossils to the base of the; 

exposure indicated."

"Coalinga beds."

Pliocene and Miocene: Southern California (Fresno and Kings Counties). 

F. M. Anderson, 1905 (California Acad. Sci. Proc., 3d ser., vol. 2, pp. 174-185). 

The series of beds unconformably underlying the Etchegoin formation and resting unconformably on all underlying formations, the youngest of which is theMonterey shale. Includes (descending order) : 

Sands, etc. 1,300 feet. 

Tamiosoma bed (oyster bed). 20 feet. 

Sands and shales. 600+ feet. (Includes the "Rainbow beds.") [See p.

177 of book cited.] 

Reef bed. 15-50 feet. 

Basal sands and gravels. 120-250 feet.

F. M. Anderson, 1908 (California Acad. Sci. Proc., 4th ser., vol. 3, pp. 1-40). "It 

is now proposed to restrict the name Coalinga beds to the lower portion of a. 

series that is unconformably related to the older members of the Miocene." 

The Santa Margarita beds of the San Luis folio, are clearly related to the-
20 GEOLOGIC UNITS OF CALIFORNIA

Coalinga beds. Overlain, generally conformably, by Etchegoin formation, and 

underlain, in places unconformably, by Monterey shales. The " Reef bed" of 

former report is properly a part of the Temblor beds.

The " Coalinga beds " as originally described included rocks belonging to 

the Jacalitos formation, Santa Margarita(?) formation, Maricopa 

shale, and Vaqueros sandstone of subsequent reports. The restricted 

definition applied to essentially the same rocks that were called Santa 

Margarita(?) formation in United States Geological Survey Bull. 398, 

descriptive of the Goalinga district.

Named for exposures north, northwest, and west of Coalinga, Fresno County.

Coast complex.

Pre-Franciscan (possibly pre-Cambrian) : Southern California (northwestern part of Monterey County).

B. Willis, 1900 (Geol. Soc. America Bull., vol. 11, p. 419). Crystalline rocks, chiefly 

metamorphic, including marble, quartzitic schists, mica schists, gneisses, and 

intrusive granite. The marbles and schists are of sedimentary origin. The 

gneisses may be partly or wholly igneous. Occurs at base of geologic column in 

the Coast Ranges. Is long pre-Cretaceous. May be Paleozoic. Is the " basement complex " of Fairbanks.

Same as Santa Lucia series of Willis.

Coast Range complex.

A name that has been applied by some geologists to the pre-Franciscan rocks 

of the Coast Ranges of southern California.

Coldwater sandstone member.

Eocene: Southern California (Los Angeles County).

W. S. W. Kew, 1924 (U. S. Geol. Survey Bull. 753). The top sandstone of the Tejon 

formation in parts of Los Angeles County is locally known as the " Ooldujater 

sandstone."

N. L. Taliaferro, 1924 (Am. Assoc. Petroleum Geologists Bull., vol. 8, pp. 789-802). 

Coldwater member of Tejon formation. West of Sespe Canyon, in the heart of 

an anticline along Coldwater Creek, and again to the north along the southern 

flank of the Topatopa Mountains, there are about 400 to 500 feet of hard white 

sandstones with intercalations of light pink, pale green, and grayish shales. The 

sandstones carry a dwarfed estuarine fauna of Eocene age. These beds have 

heretofore been included with the Sespe, but since they are fossiliferous and also 

differ lithologically from the typical Sespe they should be included in the Tejon 

as the Coldwater member.

P. F. Kerr and H. G. Schenck, 1928 (Geol. Soc. America Bull., vol. 39. p. 1091). 

Coldwater sandstone, top member of Tejon formation, is about 2,500 feet thick 

near Matilija, Ventura County. It is characterized by white friable arkose sandstone interbedded with reddish sandy shale and massive hard ledges composed of 

numerous shells of Ostrea idriaensis Gabb. Has been traced more than 40 miles 

along Santa Ynez Range westward from type locality in Coldwater Canyon.

Colfax formation. :

Upper Jurassic: Northern California (Gold Belt region). 

J. P. Smith, 1910 (Jour. Geology, vol. 18, charts opp. pp. 217, 221). " Tuffs and 

shales of the Gold Belt with Perisphinctes colfaxi." Of Portland (Upper Jurassic) age. Overlies Mariposa formation [restriction of Mariposa] and is shown 

as older than Knoxville formation.

R. W. Goranson, 1924 (Am. Jour. Sci., 5th ser., vol. 8, p. 162). " The Mariposa formation (of the Auriferous slates) of the Sierra Nevada is divided into two parts, 

the lower part being the Mariposa slate and the upper the Colfax series of the 

Gold Belt. * * * The tuff beds of Colfax contain Perisphinctes colfaxi, and 

the same beds near Nashville, Amador County, contain SimbirsJcites sp."

Is the upper part of the Mariposa slate as used by United States Geological 

Survey.
GEOLOGIC UNITS OP CALIFORNIA 21

Concord formation.

Oligocene: Western California (San Francisco Bay region).

B. L. Clark, 1918 (California Univ. Pub., Dept. Geology Bull., vol. 11, pp. 54-111.) 

Chiefly fine grayish sandstone, becoming finer and more shaly near top, and including at the base a thin layer (6 inches) of conglomerate, the boulders of 

which are composed mainly if not entirely of tuff, sandstone, and shale apparently derived from the Immediately underlying Oligocene beds. Thickness about 

250 feet. On the south side of Sobrante anticline, in the Concord quadrangle, 

it disconformably overlies Kirker tuff and unconformably underlies Sobrante 

sandstone [restricted definition, and only upper part of Lawson's Sobrante sandstone] of the Monterey group. Included in San Lorenzo series. Is the lower 

part of the Sobrante sandstone as defined by Lawson, the name Sobrante being 

restricted by the author to the upper 80 to 100 feet of Lawson's Sobrante.

Conejo volcanics.

Miocene: Southern California (west end of Santa Monica Mountains).

N. L. Taliaferro, 1924 (Am. Assoc. Petroleum Geologists Bull., vol. 8, pp. 800-801). 

" One of the most important centers of Miocene volcanism in the State lies in 

the western end of the Santa Monica Mountains. This region is often referred 

to as the Conejo Mountains, and the name Conejo volcanics is here applied to all 

the series of volcanic and intrusive rocks occurring in that region." These volcanic rocks and the interbedded Miocene sediments probably aggregate 15,000 

feet in thickness.

" Contra Costa lake bed."

Pliocene: Western California (San Francisco Bay region).

J. G. Cooper, 1894 (California Acad. Sci. Proc., 2d ser., vol. 4, p. 169). Lies chiefly 

on the northeast slope of the hills west of San Pablo Creek, forming the boundary 

between Contra Costa and Alameda Counties in that part of its course about 

4% miles northeast of the State University.

Contra Costa County Miocene.

A term that has been applied in the earlier literature to the Miocene deposits of Contra Costa County, which are now divided into several 

named formations.

Copley meta-andesite.

Devonian or older: Northern California (Redding quadrangle).

J. S. Diller, 1906 (U. S. Geol. Survey Geol. Atlas, Redding folio, No. 138). Includes 

a great mass of lava made up of many separate volcanic flows of considerable 

variety and sheets of tuffs more or less distinctively bedded but generally so 

compressed as to develop slaty cleavage. Is generally pale green on weathered 

surface, but darker green and compact on fresh, somewhat shaly fracture. 

Thickness about 1,000 feet. Is overlain by Kennett limestone (Middle Devonian) 

and is oldest formation exposed in Redding quadrangle. In places the Bragdon 

formation rests on it. Named for its occurrence in the vicinity of Copley.

Corral Hollow shales.

Jurassic(?): Western California (Alameda County).

C. P. Tolman, Jr., 1915 (Nature and science on Pacific coast, p. 45, San Francisco, 

Elder & Co.). A subdivision of Franciscan series. Contain massive beds of 

crumpled and folded cherts and, especially in vicinity of serpentine intrusions, 

lawsonite, chlorite, and glaucophane bearing schists that seem to be peculiar to 

Franciscan series. Older than Oakrldge sandstone and underlain by dense blue 

sandstone of the Franciscan.

Courtney granite.

Mesozoic: Northern California (Trinity County).

0. H. Hershey, 1900 (Science, new ser., vol. 11, pp. 130-132). The-granite of Mount

Courtney batholith. A near-by batholith is .composed of entirely different

granite. . 
22 GEOLOGIC UNITS OF CALIFOBNIA

" Coyote Mountain clays."

Miocene (lower) : Southern California (Imperial County).

G. D. Hanna, 1926 (California Acad. Sci. Proa, 4th ser., vol. 14, No. 18, p. 435). 

"Above the Latrania sands there are enormous deposits of clay, the peculiar 

properties of which may make it of commercial value at some future time. 

* * * I would propose that they be called 'Coyote Mountain clays.' They 

are extensively developed over wide areas, but the type locality has been selected 

in the foothills bordering the southeast slope of Coyote Mountain. Above these 

clays, and interbedded with them near the top to some extent are extensivedeposits of oyster shells for which the name ' Yuha Reefs' has been selected." 

Assigned to Pliocene, probably middle or upper Pliocene. [Included in upper 

part of " Carrizo Creek beds." See under Imperial formation.]

See W. P. Wooclring, 1931, under Imperial formation.

Cozy Dell shale member.

Eocene: Southern California (Ventura County).

P. F. Kerr and H. G. Schenck, 1928 (Geol. Soc. America Bull., vol. 39, p. 1090). 

Cosy Dell shale member. The rhythmically bedded fossiliferous marine green 

micaceous shale and sandstone that is typically exposed in Cozy Dell Canyon, on 

east side of Ventura River, and forms middle member of Tejon formation. 

Thickness 2,500 ± feet. Underlies Coldwater sandstone member and disconformably overlies Matilija sandstone member.

Crescent City beds.

Miocene and Pliocene: Northwestern California (Del Norte County).

J. S. Diller, 1902 (U. S. Geol. Survey Bull. 196, pp. 31-35). "Somewhat similar 

beds [to those northward and southward from Point St. George, Del Norte 

County, which consist of soft yellowish and gray shaly sandstones and whitish 

shales full of Miocene fossils] occur by the wharf at Crescent City (Crescent 

City beds), and among their fossils Dr. [W. H.] Dall recognizes Pecten parmeleei 

and TerebrataMa hempMIU, species heretofore known only from the southern 

California Pliocene. It is probable that these soft Miocene and Pliocene beds 

have a wide extent under the Pleistocene of the low, broad coastal plain extending from Smith River to a point 3 miles south of Crescent City."

Cuesta diabase.

Lower Cretaceous: Southern California (San Luis Obispo region).

H. W. Fairbanks, 1904 (U. S. Geol. Survey Geol. Atlas, San Luis folio, No. 101). 

Geologically related intrusive masses and sheets of pre-Chico age occurring upon 

opposite sides of the long area of Toro shale which extends from vicinity of 

Cuesta Pass on the -.south to the .northern edge of the quadrangle. Other diabases occur in the area.

Named for exposures near Cuesta and Cuesta Pass, San Luis Obispo County.

Cuyama formation.

Tertiary (Pliocene?): Southern California (Cuyama Valley).

W. A. English, 1916 (U. S. Geol. Survey Bull. 621, pp. 191-215). Nonfossiliferous 

yellow and pink clays, sand, and gravel, in large part of nonmarine origin. 

Thickness 250 to 600 feet. Rest on eroded edge of Santa Margarita formation 

and older beds. Crop out only in Cuyama Valley. Overlain by Quaternary 

terrace gravels.

Cuyamaca basic intrusive.

Probably pre-Cretaceous: Southern California (Cuyamaca region, San Diego

County).

F. S. Hudson, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 6, 

pp. 181, 192-207, map). Chiefly gabbros, norites, and basic diorites. Three units 

mapped (1) hypersthene diorite, (2) augite diorite, and (3) norite, gabbro, etc. 

Cuts Julian schist and Stonewall quartz diorite.

Named for the three peaks of Cuyamaca Mountains.
23

Deadman Island beds.

Pleistocene: Southern California.

J. P. Smith, 1910 (Jour. Geology, vol. 18, chart opp. p. 217). Name applied to

lower part of San Pedro formation, Los Cerritos beds being applied to upper

part of the San Pedro.

Deep Canyon fanglomerate.

Quaternary: Southern California (San Bernardino Mountains).

F. E. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 9, 

pp. 344, 384-385, and map). Detrltal rocks, consisting largely of angular and 

subangular boulders derived from older rocks to north. Contain notable proportion of rounded material and many strata of sandstone comparable to that 

in Hathaway formation. Rest on basalt, of probably early Quaternary age, 

on both sides of Deep Canyon. Across upturned and eroded, edges of the 

fanglomerate and basalt later fanglomerate has been deposited. Is older than 

Coachella fanglomerate and younger than Pipes fanglomerate.

Named for Deep Canyon, Riverside County.

Deep Spring formation.

Pre-Cambrian: Eastern California (Inyo Range).

E. Kirk, 1918 (U. S. <3eol. Survey Prof. Paper 110). About 1,600 feet of sandstones 

and dolomitic limestones, unconformably underlying the Campito sandstone 

and unconformably overlying the Reed dolomite. Named for exposures along 

west side of Deep Spring Valley In canyons north of Antelope Spring.

Dekkas andesite.

Middle Triassic: Northern California (Redding quadrangle).

J. S. Diller; 1906 (1). S. Geol. Survey Geol. Atlas, Redding folio, No. 138). Is 

generally a dark-gray lava that is more or less porphyrltic, but not conspicuously so to the naked eye. It includes a great mass of lava made up of many 

separate overlapping volcanic flows and sheets of tuff more or less distinctly 

bedded, irregularly conformable, and dipping eastward. Along eastern border 

of the quadrangle these rocks are overlain conformably by and to a small extent 

are interbedded with the bottom part of the Pit shales. Overlies Nosoni formation and underlies Bully Hill rhyolite. Thickness approximately 1,000 feet. 

Named for exposures along Dekkas Creek.

Delhi formation.

Mississippian: Northern California (Coifax quadrangle).

W. Lindgren, 1900 (U. S. Geol. Survey Geol. Atlas, Colfax folio, No. G6). Chiefly 

a peculiar dark-brown or black hard rock so fine grained as to be almost flinty 

and rarely showing either stratification or schistosity. The rock often has a 

chertlike appearance but contains less silica than the normal chert. The 

peculiar petrographic character is probably due to regional metamorphism. 

Very few lenticular limestone masses occur in it. In a few places the rock 

shows marked schistosity and resembles a dark siliceous clay slate. The formation corresponds to part of Calaveras formation. Overlies Cape Horn slate 

and underlies Clipper.Gap formation. Typical exposures near the Delhi mine, 

Nevada County.

Delmar sand.

Eocene: Southern California (San Diego County).

M. A. Hanna, 1926 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 16, No. 7, 

pp. 187-246). Sandstones, shales, and some beds, composed almost wholly of 

oysters, that might be considered limestone, but usually the matrix surrounding 

the shells is argillaceous rather than calcareous. The sandstones are both 

coarse grained and fine grained and grade into arenaceous shales. They are 

of prevailingly brown color but often have a tinge of green, while a few beds 

have a reddish and purplish cast. Many of the shales are well stratified, but 

others grade into shaly sands. Bedding Is irregular. Cross-bedding is prominent in many places. Upper part contains more sand than lower part, and the 

sands are of darker color than the overlying Torrey sand, into which the
24 GEOLOGIC UNITS OF CALIFORNIA

Delmar sand grades. Thickness more than 200 feet. Is basal division of 

La Jolla formation in La Jolla quadrangle. Rests unconformably on ChlcoCretaceous. Named for excellent exposures in sea cliff at town of Delmar, San. 

Diego County.

Diamond Peak quartzite.

Carboniferous (Pennsylvanian?) : Northern Nevada and Inyo County, Calif.

Arnold Hague, 1883 (U. S. Geol. Survey Third Ann. Kept., pp. 253, 268). Massivevitreous quartzite of grayish-brown color, passing near the summit into brown 

and green shales and schists, and with firmly cemented conglomerate at base. 

A narrow belt of blue limestone about 500 feet above the base of the formation 

contains Carboniferous fossils. Thickness 3,000 feet. Overlies White Pine 

shale and is overlain by Lower Coal Measures. Named for exposures on flanksof Diamond Peak, Eureka district, Nev.

The age of the typical Diamond Peak quartzite remains to be determined. 

The formation, with a thickness of 3,500 feet, has been identified by 

E. Kirk (U. S. Geol. Survey Prof. Paper 110, 1918) in the Inyo Range, 

Calif., where it is separated from the underlying White Pine 

shale by 500 to 1,000 feet of limestone carrying Pennsylvanian fossils.

Domengine formation.

Eocene (middle) : Southern California (Diablo Range). 

F. M. Anderson, 1905 (California Acad. Sci. Proc., 3d ser., vol. 3, pp. 167-168). 

Domijean sands. Chiefly yellow sands. Thickness 350 to 1,200 feet. Greatest development in vicinity of Domijean ranch. Overlies Kreyenhagen shales 

and unconformably underlies Temblor beds. Correlated with a part of Tejon 

formation.

B. L. Clark and R. B. Stewart, 1925 (Geol. Soc. America Bull'., vol. 36, p. 227). 

Domengine horizon (middle Eocene), a newly recognized division of the Eocene 

of California. Contains a new fauna in beds stratigraphically below those containing a typical Tejon (upper Eocene) fauna and above those of Meganos age. 

A part of this horizon was formerly considered by the senior writer to be 

Meganos, but in one locality it was called Tejon. A number of species are 

common to the Meganos and likewise to the Tejon, but, taken as a whole, thefauna is distinctive.

R. L. Nelson, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, pp. 399- 

402 and map). Divides the Eocene of Ventura County into (descending order) i 

Upper Eocene:

Tejon formation. 

Middle Eocene:

Domengine formation (gray shale interbedded with conglomerate and

brown sandstone). 

Santa Susana formation (fine-grained sandstone and shale, fossiliferous). , 

Lower Eocene:

Martinez group (three subdivisions).

" The name Domengine was proposed by F. M. Anderson and is now used by 

B. L. Clark for the upper part of his Meganos group."

F. E. von Estorff, 1930 (Am. Assoc. Petroleum Geologists Bull., vol. 14, No. 10, pp. 

1321-1336). The 500 feet of sandstone underlying typical Kreyenhagen shale 

in canyon of Canoas Creek is the Domengine sandstone, of upper middle Eocene 

age, and the sandstone unconformably underlying Kreyenhagen shale is Temblor 

sandstone, of lower middle Miocene age, the Vaqueros sandstone (of lower 

Miocene age) being absent.

Included in Meganos formation.

Named for development in vicinity of Domijean or Domengine ranch, in the 

NE. % sec. 17, north of Coalinga, Fresno County.

Domijean sands. See Domengine formation.

Duncan chert.

Mississippian: Northern California (Coifax quadrangle).

W. Lindgren, 1900 (U. S. Geol. Survey Geol. Atlas, Colfax folio, No. 66, p. 2). 

" From Duncan Peak there extends across the North Fork of American River 

to the vicinity of Monumental Hill a belt of gray or brown chert, referred to-
GEOLOGIC UNITS OF CALIFORNIA 25

as the Duncan chert. It is well exposed in the canyons near Canada Hill 

and in the canyon of the main river. This chert is in all probability not 

of clastic origin and may have been derived from limestone by a process of 

siliciflcation." Included in Blue Canyon formation.

Eden beds.

Pliocene (lower) : Southern California (San Jacinto quadrangle, Riverside County).

C. Frick, 1921 (California Univ. Pub., Dept. Geology Bull., vol. 12, pp. 283-288). 

Deposits containing a considerable collection of vertebrate fossils (including 

species of Pliohippus), through which they are correlated with middle of 

Etchegoin formation, and the Rattlesnake, Thousand Creek, and Snake Creek 

.formations. The beds occur in the Eden region, San Jacinto quadrangle. 

Assigned to the upper part of the lower Pliocene.

El Capitan granite.

Probably Cretaceous: Yoseinite National Park.

F. C. Calkins. 1930 (U. S. Geol. Survey Prof. Paper 160, pp. 121-122, map).

Light-colored biotite granite of moderately coarse and in part obscurely porphyritic texture, but along eastern margin it passes from a porphyritic to

' a nonporphyritic rock. Is one of the oldest intrusive rocks in Yosemite

region.

Named from fact that it forms greater part of El Capitan, Yosemite National Park.

" Escondido series."

Oligocene (?) : Southern California (Los Angeles County).

0. H. Hershey, April, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 3, pi. 1, 

map). [Escondido series and Escondido lava are the titles of two blocks on 

the map, lying between the Rosamond series below and Tejon (?) sandstone 

above. ]

0. H. Hershey, 1902 (Am. Geologist, vol. 29, pp. 349-372). Escondido series. 

Marine sediments and contemporaneous interbedded lava flows of Eocene (?) 

age occurring near the head of Escondido Canyon [Los Angeles County]. 

The type section is in Tick Canyon. Slightly younger than Rosamond series.

W. S. W. Kew, 1924 (U. S. Geol. Survey Bull. 753, pp. 38, 52). Hershey's "Escondido 

series" is tentatively correlated with the Sespe formation and mapped as 

.Sespe (?) formation. No fossils found. Is overlain unconformably by Mint 

Canyon formation. Name is preoccupied.

Esmeralda formation.

Miocene (upper) : Southern Nevada and Inyo County, Calif.

H. W. Turner, 1900 (Am. Geologist, vol. 25. pp. 168-170; TJ. S. Geol. Survey 

Twenty-first Ann. Rept, pt. 2, pp. 197-208). Esmeralda formation. Freshwater lake deposit, consisting of sandsto'nes, shales, and lacustral marls, with 

local development of breccia and conglomerate on a large scale; rhyolitic and 

basaltic lavas and tuffs at top in some places, also layers of rhyolitic and 

andesitic tuff lower clown in the formation. Thickness 14,800 feet. Overlain 

by rhyolitic and andesitic eruptive rocks. Named for development in Esmeralda 

County, Nev. [before the county was subdivided].

S. H. Ball, 1907 (U. S. Geol. Survey Bull. 308), mapped the " Siebert lake 

beds " (now abandoned for Esmeralda formation, the older name) in 

Inyo County, eastern California.

Etchegoin formation.

Pliocene (middle and upper) : Southern California (Sunset, Midway, 

Coalinga, Mount Diablo, and Salinas Valley districts).

F. M. Anderson, 1905 (California Acad. Sci. Proc., 3d ser., vol. 2, pp. 178-192). 

Etchegotn teds. Divided into Etchegoin sands, which compose the lower twothirds of the formation, and San Joaquin clays, which compose the upper 

one-third. The Etchegoin sands consist of unconsolidated sands and gravels, 

in many places characterized by a blue or bluish-gray color. They vary in 

thickness from 1,200 to 2,500 feet. Are commonly coarse in texture and often 

pebbly, forming beds of conglomerate. One fossil horizon occurs near bottom
26 GEOLOGIC UNITS OF CALIFORNIA

and another some distance above. [Fossils listed.] The San Joaquin clays 

are about 1,500 feet thick. At a distance they present a banded appearance, 

from the zones of color seen in the different strata, some of which have a width 

of 200 or 300 feet. The clays are conformably overlain by the fresh-water 

Tulare formation. " The Etchegoin beds overlie in turn all of the older formations of the region, resting upon each respectively with a distinct nonconformity." The next older rocks are the Coalinga beds.

R. Arnold and R. Anderson, 1908 (U. S. Geol. Survey Bull. 357, pp. 46-55). In 

accordance with Mr. [F. M.] Andersen's statements and on the basis of the 

reasons stated below, the Etchegoin formation is mapped and described in 

the present paper as the succession of slightly consolidated beds of sand, 

gravel, and clay, interbedded with occasional indurated beds, occurring on 

the summit and flanks of Anticline Ridge and on the southeast end of Joaquin 

Ridge north of Coalinga, above the base of the hill-forming sandstone beds 

(referred to for convenience as the Glyoymerls zone), and below the beds 

described as the Paso Robles formation. Strata in other portions of the 

Coalinga district are referred to the Etchegoin formation on the basis of 

paleontologic correlation with the beds on Anticline Ridge. The Glycymeria 

zone is underlain by clay that is classed in the Jacalitos formation and is overlain by a thick succession of bluish-gray sand beds interbedded with dark-gray 

sand. An unconformity occurs below the Glycymeris zone in the synclinal 

basin north of White Creek. Although in most places the Etchegoin appears to 

rest conformably on the Jacalitos formation, in other places it overlaps the 

Jacalitos. It is overlain by the Tulare formation, with possible unconformity. 

Thickness over 3,600 feet in the southern part of the district; 1,700 feet in 

oil field north of Coalinga; 1,100 feet in White Creek basin. [Fossils listed. 

The formation includes marine, brackish-water, and fresh-water deposits.]

Named for exposures in the vicinity of Etchegoin ranch, 20 miles northeast 

of Coalinga, in NW. % sec. 1, T. 19 S., R. 15 E., Fresno County.

Etchegoin sands.

Pliocene: Southern California.

F. M. Anderson, 1905 (California Acad. Sci. Proc., 3d ser., vol. 2, pp. 178-192). 

[Name applied to lower two-thirds of Etchegoin formation. See description 

under Etchegoin formation.]

Eureka quartzite.

Ordovician (Middle?) : Northern Nevada and Inyo County, Calif.

Arnold Hague, 1883 (U. S. Geol. Survey Third Ann. Rept., pp. 253, 262). Compact 

vitreous quartzite, of white and blue color, passing into reddish tints at base; 

indistinctly bedded. Thickness 500 feet. TTnconformably overlain by Lone Mountain limestone and underlain by Pogonip limestone. Named for development at 

Eureka, Nev.

This formation has been mapped by S. H. Ball (U. S. Geol. Survey Bull. 

308, 1907) in Inyo County, Calif.

Fant meta-andesite.

Lower Jurassic: Northern California (Taylorsville region).

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Altered andesitic flows and tuff 

conglomerate; of greenish to reddish-brown color. Thickness more than 150 

feet. Is younger than Hardgrave sandstone and older than Thompson limestone.

Named for an unidentified locality near Taylorsville.

Fernando group.

Pliocene and lower Pleistocene: Southern California (Los Angeles and Ventura Counties).

G. H. Eldridge and R. Arnold, 1907 (U. S. Geol. Survey Bull. 309, pp. 22-28). 

Fernando formation. A variable series of conglomerates, sandstones, and arenaceous clays; thickness 1,500 to 6,000 feet and possibly several thousand feet 

more. Fernando is a term applied by Homer Hamlin a number of years ago, 

on unpublished maps, to include the siliceous shale skirting the sides of the San 

Fernando Valley, Los Angeles County, which is the general equivalent of all
GEOLOGIC UNITS OF CALIFORNIA 27

post-Modelo and pre-Saugus beds in the Santa Clara province. Unconformably 

overlies Modelo formation in Santa Clara district and Puente formation in Puente 

Hills region and Los Angeles district. Unconformably underlies Pleistocene 

sand and gravel.

W. S. W. Kew, 1924 (U. S. Geol. Survey Bull. 753). Fernando group. Restricted to 

post-Miocene beds and divided into two formations, the Saugus formation (2,000 

feet thick) above and the Pico formation (4,000 feet thick) below. Both of 

these formations are present at the Fernando type locality, and they are separated by an unconformity. Unconformably overlain by Pleistocene terrace deposits and rests Unconformably on Modelo formation. Fossils indicate that it is 

of lower Pliocene, upper Pliocene, and lower Pleistocene age.

Foix oil zone.

Name applied to 180 to 185 feet of sandy shales and interbedded sands, 

shales, and shells, the basal 20 to 40 feet of which consists of sticky 

brown shale, in the Santa Fe Springs field, Los Angeles County. It 

directly overlies the Bell oil zone. Named for Foix No. 1 well, which 

yields oil at a depth of 3,500 feet.

Foreman formation.

Upper Jurassic: Northern California (Taylorsville region).

J. S. Dilller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Sixteen hundred 

feet of slates and sandstones with several beds of conglomerate. Plants identified by Fontaine as " clearly Mesozolc and most probably Rhaetic." Regarded 

as older than Hardgrave sandstone and younger than Trail beds. [Later proved 

to be much younger than Hardgrave sandstone.]

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). A succession of shale, sandstone, 

and conglomerate in which the sediment is for the most part derived from 

rocks which are not clearly volcanic. Shales often slaty and with pencil structure, and range in color from dark carbonaceous with traces of leaves through 

gray, which predominates, to shades and tints of red and yellow. Most of 

sandstones are very fine, decidedly shaly, and of reddish-brown and gray colors. 

Conglomerate less abundant than the shale and sandstone. Overlies, probably 

Unconformably, Hinchman sandstone, and in places Unconformably overlaps 

Mormon sandstone and even Robinson and Peale formations. [Fauna determined 

to be not earlier than Middle Jurassic.]

Named for exposures at Foreman and in Foreman's Ravine, northeast of 

Taylorsville, Plumas County.

Franciscan formation (group, where subdivided).

Jurassic (?) : Western California.

A. C. Lawson, 1895 (Am. Geologist, vol. 15, p. 347 ; U. S. Geol. Survey Fifteenth 

Ann. Rept., p. 415). Franciscan aeries. Several thousand feet of sedimentary 

and volcanic rocks with which are associated various basic intrusives, notably 

peridotite serpentines. Is of either Cretaceous or Jurassic age. Includes 

foramlniferal limestones, great formations of peculiarly bedded radiolarian 

cherts, and certain highly crystalline schists. The San Francisco sandstone 

is the dominant sedimentary formation of the series. In vicinity of San Pedro 

Point a basal formation of conglomerates, coarse grits, sandstones, shaly sandstones, shales, and argillaceous limestones is exposed.

The Franciscan rocks, which attain a thickness of several thousand feet, 

are usually treated as a formation, but in the San Francisco folio 

(No. 193) of the Geologic Atlas of the United States they were divided 

into five named and mapped formations, in descending order, Bonita 

sandstone, Ingleside chert, Marin sandstone, Sausalito chert, and Cahil 

sandstone, the Cahil including the Calera limestone member. The 

broader term " San Francisco sandstone " is no longer used. The intrusive serpentine is not a part of the formation. The Franciscan rests 

Unconformably on granite and is Unconformably overlain by the Knoxville formation.

Named for extensive exposures at San Francisco.

17462 31 3
28 GEOLOGIC UNITS OF CALIFORNIA

Furnace limestone.

Upper Cambrian (?), Ordovician (?), and Mississippiau (?): Southern 

California (San Bernarclino Mountains).

F. E. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 9, 

pp. 344, 352-365, map). White to nearly black coarsely crystalline limestone, 

4,500 feet or more thick. Grades downward into Arrastro quartzite and grades 

upward into Saragossa quartzite. Is Intruded by granites. No fossils found. 

Probably Upper Cambrian an'd Ordovician.

A. 0. Woodford and T. F. Harriss, 1928 (California Univ. Pub., Dept. Geol. Sci. 

Bull., vol. 17, p. 270). Fossils collected close to top of Furnace limestone are 

pronounced by G. H. Girty to be probably Carboniferous, and more probably 

Mississippian than Pennsylvania!! or Permian. " Thus a Mississippian (?) age 

is suggested for at least a part of the Furnace formation."

Named for Furnace Canyon, San Bernarclino County, which is cut in the 

formation.

Gabilan limestone.

Pre-Jurassic (?) : Western California (San Francisco Bay region).

G. F. Becker, 1888 (U. S. Geol. Survey Mon. 13, pp. 128, 181). In the Gavilan 

Range [spelled Gabilan by U. S. Geographic Board], some 60 miles south of Bay 

of San Francisco, the lowest sedimentary formation encountered is in part limestone, which at points is very crystalline. Associated with it are rocks of 

Archean gneiss type. " It is possible that it is a member of the Knoxville series 

much more metamorphosed than usual, but it appears more probable that it is 

a remnant of some older formation which has perhaps undergone repeated 

metamorphism."

Is of pre-Franciscan age, and in the San Francisco region it occurs as inclusions in the quartz diorite that has been called " Montara granite," of 

late Jurassic (?) age. (See also under Snr series.) 

Gavilan. See GaMlan limestone.

Genesee Valley limestone and shales.

Triassic: Northern California (Sierra Nevada).

J. P. Smith, 1910 (Jour. Geology, vol. 18, chart opp. p. 220). Oenesee Valley limestone and shales. Triassic. Older than Sailor Canyon shales [restriction (?) 

of Sailor Canyon formation], and overlies Paleozoic.

J. S. Diller (U. S. Geol. Survey Bull. 353, 1908) mapped the Triassic rocks 

of Genesee Valley region as Swearinger slate and Hosselkus limestone. 

Name probably derived from occurrence in Genesee Valley east of 

Genesee, Plumas County. 

"Golden Gate series."

Jurassic (?) : Western California.

H. W. Fairbanks, 1895 (Jour. Geology, vol. 3, pp. 416-426). Jasper, sandstone, 

shale, slate, and large bodies of fine-grained greenish eruptives. Extends from 

Santa Barbara County northwestward through Coast Ranges to Klamath Mountains. Unconformably overlain by Knoxville beds and rests unconforrnably on 

crystalline basement complex.

Is same as Franciscan formation.

Named for development on the north and south shores of the Golden Gate.

Gosnell shale zone.

A part of Pico formation in the Ventura field, Ventura County, southern 

California. Thickness 75 to 2,000 feet. Lies approximately 3,000 feet 

below surface. 

Grapevine conglomerates.

C. [R.] Keyes, 1923 (Pan-Am. Geologist, vol. 40, pp. 52, 79). Conglomerate, 500 

feet thick, unconformably beneath Greenwater volcanics, and composing lower 

formation of Amargosan series (of Early Tertic age) in Nevada.

Named for good exposures around base of Grapevine Range, on east side 

of Death Valley, Inyo County, Calif.
GEOLOGIC UNITS OF CALIFORNIA % 29

GreeaiAvater volcanics.

C. [R.] Keycs, 1923 (Pan-Am. Geologist, vol. 40, pp. 02, 79). "Term restricted to 

the tuffs and basalt flows associated with the borute deposits of Death Valley, 

and are presumably of Early Tertic age." Thickness 4,000 feet. Composes upper 

formation of Amargosan series in Nevada. Unconformably below Keclhill sandstones and unconformably above Grapevine conglomerates.

Derivation of name not stated, but probably derived from exposures at or 

near Greenwater, east of Death Valley, in Inyo County, Calif.

formation.

Silurian? (may be Ordovician) : Northern California (Taylorsville region).

J. S. Diller, 1892 ('Geol. Soc. America Bull., vol. 3, pp. 370-394). G-rizzly quartette, 

400 feet thick. Oldest formation in Taylor[s]ville region. Tentatively assigned to Silurian (7). Is older than Montgomery limestone of Niagara age.

.T. S. Diller, 1892 (preliminary proof-sheet edition of Lassen Peak folio, No. 15, 

of TJ. S. Geol. Survey Geol. Atlas). "Grizzly formation. Within the area 

represented on the [Lassen Peak] map it is composed chiefly of slates, but ire 

Mount Grizzly, near Taylor[s]ville, where the formation has its greatest development, there are besides slates both quartzite and limestone. The last is 

of special interest in being Silurian, the oldest fossiliferous rock yet discovered! 

in California." [The limestone is the Montgomery limestone, of Niagaran age, 

which is treated as a distinct formation, overlying the Grizzly formation.]

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Grizzly formation. Gray, welldeliiied but thin-bedded quartzite overlain by lentils of [Montgomery] limestone and interstratified with shaly, often siliceous slate (argillite) having; 

irregular cleavage. The beds of quartzite range i'n thickness from 5 to about 

20 feet and run out into shale in a short distance. The shale beds are generally thicker than the quartzite and for the most part greenish gray to drab, 

although sometimes black and more or less flinty, but not much altered. The 

lighter colored shales are often sandy and constitute the prevailing portion 

of the formation, although beds of well-marked quartzite are usually present 

and frequently predominate. The coarser beds of quartzite are near base of 

formation and are about 200 feet thick. Thickness of formation 400 to 1,000- 

feet. On eastern slope of Grizzly Mountains, near the northern end, quartzite 

prevails immediately beneath a lentil of [Montgomery] limestone, but north of 

Montgomery Creek shales occupy the corresponding position, and as the section.' 

does not continue below the tunnel it does not disclose the coarser beds lying; 

at the bottom of the Grizzly quartzite horizon. Is overlain in places conformably by Montgomery limestone, but in most places is unconformably overlain by Taylorsville formation. Rests on ancient metarhyolite.

As the Grizzly formation underlies the Montgomery limestone, of Niagaran

age, it may be either Silurian or Ordovician. 

Named for exposures on eastern and northeastern slopes of Grizzly Mountains, Plumas County.

Grizzly quartzite. See Grizzly formation.

" Grizzly Peak andesite."

Pliocene: Western California (San Francisco region).

A. C. Lawson and C. Palache, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 

'2, p. 379, and map). A thick accumulation of lava flows which for the most 

part are of a different petrographic type from the underlying basalts and 

should be classed as andesites. Though of rather varied character, they are 

grouped together under the name Grizzly Peak andesite. As mapped they 

include certain subordinate flows of basalt and intercalations of tuff. There 

:ire two rather distinct facies of the andesite the lower one a medium-textured 

holocrystalline rock, the upper a dense compact rock, frequently glassy, with 

a prevailingly porphyrltic habit, aggregating 175 to nearly 300 feet. As mapped 

the 'Grizzly Peak andesite rests on rhyolite tuff and is overlain by the Slestau 

formation. As mapped it forms Grizzly Peak, in the Berkeley Hills.

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

[The andesite of Grizzly Peak is included in the Moraga formation, according 

to the definition of Moraga, and as mapped.]
30 GEOLOGIC UNITS OP CALIFOBNIA

Half Dome quartz monzonite.

Probably Cretaceous: Yosemite National Park.

F. C. Calkins, 1930 (U. S. Geol. Survey Prof. Paper 160, p. 126, map). Name 

proposed by H. W. Turner, in unpublished manuscript. Medium-grained lightgray rock; contains nearly equal amounts of biotite and hornblende. Chiefly 

nonporphyritic, but in part obscurely porphyritic. Included in Tuolumne intrusive series, in which it is next younger than the Sentinel granodiorite, and 

next older than the Cathedral Peak granite.

Named from fact that it composes Half Dome, in Yosemite National Park.

Hall City limestone.

Carboniferous: Northern California (Klamath Mountains).

J. S. Diller, 1903 (Am. Jour. Scl., 4th ser., vol. 15, pp. 342-362). [Mentions (but 

does not describe or locate in the section, except to say that it belongs to the 

southwestern Carboniferous belt) the Hall City limestone. On a later page 

reference is made to the Hall City mines, to which one of these Carboniferous 

limestones extends.]

Hambre sandstone.

Miocene (middle) : Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Medium-textured slightly ferruginous sandstones with some sandy shales. Thickness 1,200 feet. A formation of the Montereyl group. Conformably underlies 

fiodeo shale and conformably overlies Tice shale. Named for exposures along 

Arroyo del Hambre, Contra Costa County.

Hardgrave sandstone.

Lower Jurassic: Northern California (Taylorsville region).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Red sandstone, 450 

feet thick, older than Thompson limestone and younger than Foreman beds. 

[Now known to be much older than Foreman beds.]

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Varies from fine shaly sandstone 

to conglomerate and is almost wholly of a tuffaceous character. The most 

common color is red, ranging from brick-red to dull brown, but much of it is 

gray, and the two colors are intermingled irregularly in the same bed. Bedding 

generally well marked. Thickness 450 feet. Is next younger than Trail formation. Is separated from overlying Thompson limestone by the Fant metaandesite. Is limited in its distribution within the Taylorsville region almost 

exclusively to the slope of Mount Jura, east of Taylorsville. One belt lies along 

western base of Mount Jura.

Named for exposures on Hardgrave's ranch, near Taylorsville.

Hathaway formation.

Upper Pliocene or lower Quaternary (mapped as Pliocene) : Southern California (San Bernardino Mountains).

F. B. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 9, 

pp. 344, 375, 376-378, 384, map). A series of land-laid deposits. Bulk of 

formation is rather fine for fanglomerate. Upper 1,800 feet consists of light 

bluish-gray sandstone containing many streaks of angular pebbles derived from 

igneous and metamorphic rocks to north. This sandstone grades downward into 

light-gray shale containing hard calcareous streaks, of which 800 feet is exposed 

in small canyon just west of San Gorgonio River and base not seen. Total 

thickness unknown. In places overlain, in angular discordance, by a basalt 

flow. In other places overlain by Deep Canyon fanglomerate or by Cabezon 

fanglomerate; and in still other places by Heights fanglomerate. Is younger 

than Lion sandstone and older than Pipes fanglomerate.

[Named for Hathaway Creek, Riverside County, on and near which it is 

exposed.
GEOLOGIC UNITS OF CALIFOENIA 31

Hay Fork beds.

Miocene: Northwestern California (Trinity County).

J. S. Diller, 1902 (U. S. Geol. Survey Bull. 196, pp. 43-44). [Describes deposits near 

town of Hay Pork, .Trinity County, consisting of sandstones and shales, locally 

associated with coal, and probably extending for 10 miles nearly east and west, 

with a width of about a mile. Contain Tertiary fossils and are probably of 

upper Miocene age. In one place casually alludes to them as the Hay Fork 

teds.]

J. S. Diller, 1903 (Am. Jour. Sci., 4th ser., vol. 15, pp. 342-362). [Describes upper 

Miocene beds of Hay Fork region and throughout the text calls them the Hay 

Fork teds.] "Formed In an estuary near sea level."

" Headlight porphyry."

A name that has been locally applied to a granodiorite porphyry, of probably 

earliest Cretaceous age, in Trinity County.

Heights fanglomerate.

Quaternary: Southern California (San Bernardino Mountains).

F. E. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 9, 

pp. 344, 392-393, map). Several areas of fanglomerate are found in this region 

which were laid down under the same conditions as obtain at the present day, 

but they have been uplifted and are undergoing dissection. Banning Heights is 

floored with such an accumulation which overlies schists and granite, the 

Hathaway shales and sandstones, and the Cabezon fanglomerate. In Hog Caflon, 

Little San Gorgonio Creek, and Cherry Cafion there is an extensive fanglomerate 

at same general elevation as Banning Heights. It is of the same sort of material 

and bears same relationships to surrounding topography. On north side of range 

there are several areas of fanglomerate which are probably of about same age as 

those described above.

A. C. Woodford and T. F. Harriss, 1928 (California Univ. Pub., Dept. Geol. Sci. Bull., 

vol. 17, pp. 279-283), state that Heights fanglomerate of Vaughan is included 

in their Blackhawk breccia. See under Blackhawk breccia.

Named for Banning Heights, Riverside County, which it floors.

Hercules shale member.

Miocene (upper): Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Bituminous shale, 500 feet thick, forming a member of the Brioncs sandstone. 

Named for Hercules station, on San Pablo Bay.

Hinchman sandstone.

Upper Jurassic: Northern California (Taylorsville region).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Hlnchman tuff

consists of 500 feet of greenish or gray sandrock, composed in many places of

lapilli. Overlies the Bicknell sandstone. 

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Hinchman sandstone consists of

500 to 1,000 feet of coarse tuffaceous sandstone and conglomerate of andesltle

material, with some shaly beds. Unconformably overlain by Foreman formation.

and grades into underlying Bicknell sandstone.

Named for exposures at Curtice Cliff, in the lower part of Hinchman Ravine, 

Plumas County.

Hinchman tuff. See Hinchman sandstone.

Horsetown formation.

Lower Cretaceous (Shasta series) : California and Oregon.

C. A. White, 1885 (U. S. Geol. Survey Bull. 15, pp. 19-32). [See definition under

Enoaville formation.] 

J. S. Diller and T. W. Stanton, 1894 (Geol. Soc. America Bull., vol. 5, pp. 435-464).

[See explanation under Knotaville formation.]

The Horsetown formation has a maximum thickness of 6,000 feet. It overlies the Knoxville formation and underlies the Chico formation. The
32 GEOLOGIC UNITS OF CALIFORNIA

upper part may be of early Cenomanian age, and therefore Upper Cretaceous, but the United States Geological Survey classifies the unit as 

Lower Cretaceous.

Named for exposures at Horsetowu, Shasta County. Also well exposed on 

North Fork of Cottonwood Creek.

Hosselkus limestone.

Upper Triassic: Northern California (Taylorsville and Redding region).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Fossiliferous limestone, 140 feet thick, considered to be younger than Sweariuger slate aud older 

than Trail beds.

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Dark-blue to light-gray limestone, 

thin bedded, in some places decidedly slaty; fossiliferous. Thickness 140. feet. 

Well developed in Redding region, where upper part is lighter colored and more 

massive and contains a spirifer-like shell, and }ower part is thinner bedded and 

darker, with small coiled forms. Conformably overlain (not underlain, as originally assumed) by Swearinger slate, and uuconformably underlain by Robinson 

formation. In Redding region it is separated from the Robinson horizon by 1,000 

feet of andesitic and rhyolitic lavas, which are overlain by 1,500 feet of shales, 

sandstones, and tuffs of Triassic age.

Named for fact that it forms prominent ledges on divide between Genesee 

A'alley and Hosselkus Creek, a mile northeast of Hosselkus ranch, in 

Plumas County.

Hosselkus series.

G. H. Ashley, 1923 (Eng. and Mm. Jour.-Press, vol. 115, pp. 1106-1108), proposed Hosselkus series as a geographic name for the Upper Triassic 

series.

Hall meta-aiidesite.

Upper Jurassic: Northern California (Taylorsville region).

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Greenish to reddish meta-andesite 

resembling Pant meta-andesite. Prevailing type is greenish and essentially nonporphyritic; occasionally in Little Grizzly Creek region it is decidedly amygdaloidal. Is only partially crystalline. Much of it is in more or less well-defined 

sheets representing lava flows and tuff. In places is decidedly slaty. It penetrates Mormon sandstone and Foreman formation. Most likely erupted near close 

of Jurassic.

Named for exposures east of the Hull diggings (called Taylor diggings on 

Taylorsville map).

Hyampom lake beds.

Miocene: Northwestern California (Trinity County).

J. S. Diller, 1902 (U. S. Geol. Survey Bull. 196, pp. 41-43). "Near the mouth of the 

canyon [where Hay Fork enters] the coal-bearing series, which for convenience 

we will call the Hyampom bed's, has an exposed thickness of 250 feet, the upper 

100 eet being conglomerate and the lower portion sandy, containing here and 

there concretions. Some of the sandstones are rather hard, strike N. 85° H., 

with a dip of 30° SE., and contain coaly beds. Near the base of the series 

is 25 feet of conglomerate, and the bottom portion, about 30 feet in thickness, 

is not exposed." Limited to Hyampom Valley, 3 or 4 miles in length and of 

less breadth. Rest unconformably on underlying beds. Flora identified by F. H. 

Knowlton as upper Miocene.

Imperial formation.

Miocene (late lower) : Southern California (Imperial County).

G. D. Hanna, 1926 (California Acad. Sci. Proc., 4th ser., vol. 14, No. 18, pp. 434-435). 

" There appears to be good reason to suspect that more than one Pliocene formation is represented on the flanks of Coyote Mountain [which he says is also 

called Carrizo Mountain]. Very little reason exists for the placing of the coral 

' reef, the lowermost exposed fossiliferous stratum, with the great oyster reefs of 

the upper part. For a long time the deposits about Coyote Mountain have been
GEOLOGIC UNITS OF CALIFORNIA 33

called ' Carrizo Creek' beds, or ' Carrizo ' formation; the latter was proposed 

definitely in 1914 by Kew, but F. E. Vaughan has shown that these names are 

inapplicable because of prior use elsewhere. This is to be regretted, but it 

seems that current usage demands a different name. Since we are unable as 

yet to correlate definitely any of the fossil-bearing strata with any named formation elsewhere, I would propose that it be known as the ' Imperial formation ' 

in the future. The type locality should he taken as> the coral reef exposed in 

Alverson Canon, on the south side of the mountain. This coral reef has a distinctive fauna. It is succeeded by about 200 feet of very fossiliferous calcareous 

sandstones for which I would propose the name ' Latrania sands.' * .* * 

Above the Latranda sands are enormous deposits of clay [which he names Coyote 

Mountain clays]. * * * Above the clays and interbedded with them near 

the top to some extent are extensive deposits of oyster shells for which the 

name ' Yuha Reefs ' has been selected. * * * According to the above nomenclature, Conrad's fossil mollusks came from the Yuha Reefs. Kew echinoderms 

are from the Latrania sands; and Vaughan's corals from the Imperial formation. It is believed that further work will necessitate further subdivision rather 

than a consolidation of the above formations." [According to the foregoing quotation the name Imperial formation was proposed as a substitute for " Carrizo 

Creek beds," but as defined it was also restricted to the coral reef forming the 

basal part of the "Carrizo Creek beds."]

W. P. Woodring, 1931 (Carnegie Inst. Washington Pub. 418, pp. 1-25), redefined 

Imperial formation in the broad sense, restricting it to marine deposits, and 

dividing it into an upper or siltstone m'ember (1,400± feet thick) and a basal 

conglomerate member (a few inches to 700 feet thick). He correlated the basal 

conglomerate member with the " Imperial formation " of Hanna in the narrow 

sense, and the siltstone member with the " Latrania sands," " Coyote Mountain 

clays," and the interbedded " Yuha Reefs " of Hanna. He assigned his Imperial 

formation to late lower Miocene, and his overlying Palm Spring formation (nonmarine) to middle or upper Miocene.

Indian conglomerate.

Eocene: Southern California (southern part of Sinta Ynez quadrangle,

Santa Barbara County).

R. N. Nelson, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 10, 

pp. 344, 350-352, pi. 46, and map). Rudely sorted pebbles and boulders, up to 1 

foot in diameter, in coarse-grained sandstone matrix, firmly cemented. In Indian 

Canyon, where the formation is over 500 feet thick, the conglomerate is in beds 

8 feet thick, or less, separated by massive, thick-bedded sandstones which sometimes attain an aggregate thickness of 25 feet. Near its base, in places, are 

lensps of) sandstone. A characteristic feature is the large percentage of acid 

porphyry pebbles. Varies in thickness from 25 feet in Mono Creek to 500 feet 

in Indian Canyon. Rests, with probable unconformity in places at least, on 

Cretaceous rocks, and is conformably overlain by Mono shale. Is best developed

in Indian Canyon, whence its name.

i

" Indio " formation.

Miocene (middle or upper) : Southern California (Riverside County).

J. P. Buwalda and W. L. Stanton, 1930 (Science, new ser., vol. 71, pp. 101-106). 

Indio formation. Several thousand feet of strongly folded and erosionally 

beveled terrestrial deposits, consisting of clays, probably playa deposits, arkosic 

sandstones and fanglomerates with considerably worn fragments in subequal 

thicknesses. Form entire exposed section in Indio Hills. Type section along a 

northeast-southwest line through the Indio Hills about 2 miles northwest of Thousand Palm Canyon. At all localities overlies the, marine Carrizo formation, 

probably uncouformably. No fossils, but stratigraphic relations to Carrizo formation and well-indurated character of Indio formation indicate a probable age 

not greater than middle Miocene and not less than lower Pliocene in short, 

approximately middle Neocene.

Preoccupied in Eocene of Texas.

Ingleside chert.

Jurassic (?): Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Radiolarian chert, prevailing dull brownish red, especially in its thicker and 

more evenly bedded portions, but also includes some yellow and green rock and
34 GEOLOGIC UNITS OF CALIFOBNIA

locally rock of other colors. Contains thousands of thin beds of earthy shale. 

In many places the rock is true jasper. Maximum thickness about 530 feet. 

Is overlain by Bonita sandstone and underlain by Marin sandstone. Next to top 

formation of Franciscan group.

Named for exposures in the San Miguel Hills^ east of Ingleside, San Francisco County.

Inyo marble.

Lower Cambrian: Eastern California (Inyo Range). .

H. G. Hanks, 1886 (California State Min. Bur. Sixth Ann. 0 Rept., pt. 1, p. 25). The 

Inyo marble caps White Mountain. Is a dolomite of finest quality, as pure and 

white as the finest Carrara marble. Is found at numerous localities in the 

Inyo Range from White Mountain south 100 miles or more.

The rocks that cap White Mountain are mapped by E. Kirk (U. S. Geol. 

Survey Prof. Paper 110, pi. 1, 1918) as of Lower Cambrian age.

Inyo series.

Middle and Lower Triassic: Southern California (Inyo Range).

J. P. Smith, 1910 (Jour. Geology, vol. 18, table opp. p. 217). The Inyo series includes black limestone of Inyo Mountains (Parapopanoceras beds), of Middle 

Triassic age, and gray limestones of Inyo Mountains (Meekoceras beds), of 

Lower Triassic age.

G. H. Ashley, 1923 (Eng. and Min. Jour.-Press, vol. 115, pp. 1106-1108), proposed 

Inyo series as a geographic name for the Lower Triassic series.

Inyoan series.

Lower Triassic: Southeastern California and Nevada.

C. [R.] Keyes, 1923 (Pan-Am. Geologist, vol. 40, pp. 52, 59, 79). "In southwest 

Nevada and the adjoining parts of California Early Triassic sedimentation is 

important. The Inyoan series, as it may be called, of the Death Valley region 

attains a thickness of 1,200 to 1,500 feet and is characterized by a well-defined 

fauna. * * * The section consists mainly of Early Triassic shales, of which 

five subdivisions are easily differentiated." Composes all the Early Triassic of 

Nevada and is divided into five unnamed formations in descending order, 10 feet 

of limestones, 800 feet of shales, 15 feet of limestones, 400 feet of shales, and 

100 feet of conglomerate. The name Koipatoan series is given to the Middle 

Triassic and Staran series to the late Triassic.

Named for Inyo County, Calif.

lone formation.

Eocene: Northern California (Gold Belt region).

W. Lindgren, 1894 (U. S. Geol. Survey Geol. Atlas, Sacramento folio, No. 5). 

" During the Neocene period the auriferous gravels accumulated on the slope

0 of the Sierra Nevada, and at the same time there was deposited In the gulf 

then occupying the Great Valley a sedimentary series consisting of clays and 

sands to which the name lone formation has been given." The largest development occurs south of American River. The strata form characteristic flattopped hills and consist of a succession of light-colored clays and white or 

yellowish-white sandstone. Is usually overlain by a few feet of reddish 

Pleistocene gravel and rests on Chico formation.

H. W. Turner, 1894 (Am. Geologist, vol. 13, pp. 229-249). lone formation consists of white shales, clay, and sand of Miocene age. It is best developed in 

Amador and Calaveras Counties, where it is separable into

1. lone clay rock or tuff 100+ feet.

2. lone sandstone 100+ feet.

3. White clay and sand beds containing coal seams 860+ feet.

Howel Williams, 1929 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 18, No. 6, 

pp. 112, 124). lone sands. Very siliceous sands with anauxite; usually 

pure white, but often stained brown, pink, or purple. Thickness 100 to 150 feet. 

Underlie Butte gravels, with minor disconformity, occasionally with erosion unconformity. Overlie Marysville formation with minor disconformity. The 

term lone is applied to these sands in the sense adopted by Dr. V. T. Alien, 

who has permitted this brief advance statement of his work. " Previous to 

Alien's work the term had been used so widely to include deposits of very 

different lithology and often of different ages that it had long since lost all
GEOLOGIC UNITS OP CALIFORNIA 35

accurate connotation. Alien has redefined the term, restricting it to the 

quartz-anauxite sands of the Meganos." His work indicates clearly that this 

peculiar lithological unit is of surprising uniformity throughout a wide belt 

along the foothills of the Sierra Nevada, and that it probably represents a 

single persistent horizon. He has shown that the lone sands are probably the 

age equivalents of the " Bench gravels" of the Sierra, and that they were 

chiefly derived by the erosion of an intensely weathered granitic series. The 

formation is often characterized by strong current bedding.

V. T. Alien, 1929 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 18, No. 14, 

pp. 347-419). lone formation restricted to lower two members of type section 

that is, to the white clay and sand beds containing coal seams and the overlying white or red sandstone. The upper clay rock or rhyolite tuff formerly 

included is now considered to probably be Miocene and is here excluded. It is 

separated from underlying lone formation restricted by an extensive erosion 

period. The lower clays of the lone were not formed from rhyolitic tuffs, as 

heretofore supposed. As here restricted the formation Is a lithologic unit serviceable in mapping and valuable in correlation, and it can be traced for more 

than 200 miles. The work of writer lends support to belief that the lone is 

contemporaneous with the white quartz gravels of Sierra Nevada. The lone 

is composed of delta deposits formed at the mouths of many westward-flowing 

streams. The presence of marine fossils in upper part shows that it accumulated on the shores of an Eocene sea. From 1913 to 1916 R. E. Dickerson 

made valuable contributions to our knowledge of the lone by finding Eocene 

marine fossils in it. He designated the lone as the Slphonalia sutterensis zone, 

which he considered the uppermost part of Tejon Eocene. He concluded the 

lone is the marine or estuarine equivalent of the auriferous gravels of Sierra 

Nevada. In 1921 B. L. Clark referred Dickerson's uppermost Eocene Siphonalia sutterensia zone to the Meganos Middle Eocene. This reference applied 

especially to the marine lone, such as Dickerson described from Oroville Table 

Mountain and Marysville Buttes, but not to the type section. Perhaps the 

latter was excluded because of its limited fauna and poor preservation of the 

forms obtained.

Named for exposures at lone, Amatlor County, Avliore it overlies Mariposa 

slate. It has been described as younger than Tejon, as equivalent to 

upper part of Tejon, and as older than Tejon and equivalent to 

Meganos formation!

41 lone clay rock or tuff." See under 'lone formation, H. W. Turner, 1894.

" lone sandstone." See under lone formation, H. W. Turner, 1894.

Jacalitos formation.

Pliocene (lower) : Southern California (Coalinga region).

R. Arnold and R. Anderson, 1908 (U. S. Geol. Survey Bull. 357). Sand, gravel, 

clay, and sandstone, 1,600 to 3,600 feet thick, with a characteristic fauna. 

Underlies, in places probably unconformably, the. major beds of blue sand that 

are characteristic of the lower part of the Etchegoin formation, but the Jacalitos 

also Includes a great thickness of blue-sand beds at its summit in the southeastern part of the Kreyenhagen Hills. Unconformably overlies Santa Margarita formation. Named for exposures both north and south of Jacalitos 

Creek, and in the Jacalitos Hills, Fresno County.

Johannesburg gneiss.

Archean: Southern California (Randsburg quadrangle, Kern and San Bernardino Counties).

C. D. Hulin, 1925 (California State Min. Bur. Bull. 95, pp. 21-23, 28, map). Consists of a variety of rock types, the majority of them gneisses. In no case do 

they show true schistose cleavage. The most characteristic type represented 

may be termed a hornblende-plagioclase gneiss, which shows a fine parallel 

banding of light and dark constituents. Another type, consisting entirely of 

coarsely crystalline black hornblende, may be termed a hornblende gneiss. Interbedded with these varying types of gneisses occur rather important quantities of a massive and quite coarsely crystalline white marble in beds 1 to 20 

feet thick. In places thin layers of light-colored gneiss are intercalated with 

the limestone. A subordinate amount of quartzite, which may be massive or 

coarsely banded, is interbedded with the marble and the gneisses. The forma-
36 GEOLOGIC UNITS OP CALIFOBNIA

tion is predominantly if not entirely of sedimentary origin and probably marine. 

The hornblende gneisses, however, may be derived from igneous rocks. A 

thickness of approximately 2,500 feet outcrops, but neither top nor bottom was 

seen. Believed to unconformably underlie Rand schist. Is assigned to Archean. 

Named for exposures 2 miles north of Johannesburg, Keni County.

Johnson granite porphyry.

Probably Cretaceous : Yosemite National Park.

P. C. Calkins, 1930 (U. S. Geol. Survey Prof. Paper 160, pp. 127-128, map). The 

most centrally located, most siliceous, and youngest rock of the Tuolumne intrusive series. Is next younger than Cathedral Peak granite. Its major . portion 

resembles an aplite, but it is distinguished by widely scattered phenocrysts of 

microcliue. A pavt of the mass has the texture of a more typical granite 

porphyry.

Named from fact that it forms Johnson Peak, Yosemite National Park.

Johnson gravels.

Miocene: Northern California (Taylorsville region).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 371-394). Auriferous gravels 

of fluviatile origin, containing Miocene plants. Lie at altitude of 5,000 to 5,600 

feet. Turner has traced these gravels south of the fortieth parallel, through the 

Cascade mine to vicinity of Haskell Peak, where they have an elevation of 7,000 

feet. The southerly inclination of the pebbles, the northerly slope of the 

deposits, and the distribution of pebbles containing Jurassic fossils.afford strong 

evidence that the stream by which the gravels were laid down flowed from the 

vicinity of Haskell Peak northward across Genesee Valley and the northern arm 

of Indian Valley to the Mountain Meadows. Lie unconformably on upturned 

edges of the massive Jurassic and Triassic formations, find although not in contact with the valley alluvium (Pleistocene) their unconformity due to erosion is 

well marked. [Derivation of name not stated.]

In subsequent publications Mr. Diller did not use this name, but described 

the gravels simply as auriferous gravels.

Julian group.

Triassic, Carboniferous, or older: Southern California (San Diego County).

F. J. H. Merrill, 1914 (Geology and mineral resources of San Diego and Imperial 

Counties, pp. 11-12, California State Min. Bur.). Metamorphic formations of 

mica schists, slates, quartzites, and limestone, the first especially well exposed 

near Julian and the latter occurring in small areas at several points. Age 

uncertain. May be Triassic, Carboniferous, or older.

Named for exposures near Julian, San Diego County.

Julian schist. (Sedimentary.)

Triassic or late Paleozoic, or both :. Southern California (Cuyamaca region, 

San Diego County).

F. S. Hudson, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 6, 

pp. 181, 182-190, map). Julian schist, Quartz-mica schists, quartz two-mica 

schists, quartz-muscovite schists, and some thin-bedded quartzites. The metamorphosed product of shales, fine clayey sandstones, and nearly pure quartz 

sandstones, with subordinate layers of basic volcanic rock. Thickness more than 

6,600 feet.

Named for village of Julian, San Diego County, which occurs in midst of 

the mass.

Kagel fanglomerate.

Quaternary: Southern California (San Gabriel Mountains).

M. L. Hill, 1930 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 19, No. 6, pp. 

141, 144). Kagel formation. The >younger and topographically lower Quaternary fanglomerate, in which Kagel Canyon is being dissected. Composed of subangular and poorly sorted fragments of gneiss and granitic rocks up to 2 feet in 

diameter. Is not so brown in color as the older Lopez fanglomerate. Overlies 

Saugus formation with angular unconformity.
GEOLOGIC UNITS OF CALIFOKNIA 37

Kalorama member (of Las Posas formation).

Pleistocene: Southern California (Veutura County).

E. D. Pressler, 1929 (California University Pub., Dept. Geol. Sci. Bull., vol. 18, No, 

13, pp. 325-345). Kalnrama member (also Kalorania horizon). Lower part of 

Las Posas formation. Contains a marine Pleistocene fauna, but of cooler water 

than overlying Long Canyon member. Correlated with Saugus formation. Is 

of approximately same age as or slightly older than Lower San 1'eclro Pleistocene.

Derivation of name not stated.

Kanaka formation.

Mi.s&issippian: Northern California (Colfax region).

H. G. Fergusou, 1929 (Am. Inst. Min. and Met. Eng. Pub. 211, p. 4). Kanaka formation. Chiefly interbedded dark-colored slates and chloride greenstones (the 

latter largely andesitic tuffs and breccias), with a cherty member [200 to 300 

feet thick] toward middle of formation, and a basal conglomeratic member [200 

'to 350 feet thick]. Contains some beds that are interpreted as flows, and possibly 

in part intrusive sheets, of andesite and dacite. Thickness of formation probably nearly 2,000 feet. Conformably underlies Relief quartzite and overlies, 

probably unconformably, Tightner formation. Named for exposures in valley of 

Kanaka Creek, Sierra County. Extends from Oregon Creek to South Yuba.

" Karquines series." 

"Karquinez series."

Eocene: Western California.

R. Arnold, 1902 (Science, new ser., vol. 15, p. 416), and A. C. LaAvson, 1903 (Geol. 

Soc. America Bull., vol. 13, p. 545). Includes Tejon (2,100 feet thick) and 

Martinez (2,200 feet thick),.or all of the Eocene of western California.

A local geographic name synonymous with Eocene series in this region. 

Probably named for occurrence at Carquinez Bay, Carquinez Point, or 

Carquinez Strait; connecting Suisun and San Pablo Bays, California. 

(Carqninez is spelling adopted by U. S. Geographic Board.)

" Keddie formation."

Pennsylvanian: Northern California (Lassen Peak and Taylorsville regions). 

Name used in preliminary proof-sheet edition of Lassen Peak folio of Geologic Atlas of the United States. 1892, for rocks forming "a narrow belt 

upon the northeast slope of the Keddie-Dyer ridge," in Plumas County. 

In the published Lassen Peak folio (No. 15), by J. S. Diller, 1895, the 

urea is mapped as Robinson formation.

Kennett formation.'

Middle Devonian: Northern California (Redding region).

J. P. Smith, 1894 (Jour. Geology, vol. 2, pp. 591-593, 598). Kcnuctt limestones and 

shales. A thick series of dark contorted siliceous shales, with occasional masses 

of limestone that contain Devonian fossils, probably Middle Devonian. Exposed 

between Squa\v and Backbone Creeks, about 4 miles west of Kennett, on Sacramento River. Compose the Sacramento formation (H. W. Fairbanks MS.). 

" We do not know the age of the rocks immediately underlying the Baird shales, 

but the siliceous shales of the Sacramento River lie some distance below them 

and are probably in part of Carboniferous age."

According to J. S. Diller (U. S. Geol. Survey Geol. Atlas, Folio 138, 1906) 

the Baird shale is underlain by the Bragdon formation (Mississippian), 

which rests unconformably on the Kennett formation.

Kern River formation.

Pliocene: Southern California (Kern River region).

P. M. Anderson, 1905 (California Acad. Sci. Proc., 3d ser., vol. 2, pp. 187-188, 191>. 

Kern River lefts. Mainly sands and sandy clays, dipping gently west. The 

locality is on Kern River, 2 to 6 miles east of Oil City, Kern County. The entire 

thickness of the strata exposed along the river aggregates about 3,000 feet, of 

which the lower two-thirds belongs to the Miocene. Toward the base they
38 GEOLOGIC UNITS OF CALIFORNIA

become very fossiliferous. [Lists many fossils.] The most complete and most 

typical fauna of the Lower Miocene of California interior is that of the Kern 

River beds on the southeastern border of the San Joaquin Valley.

F. M. Anderson, 1911 (California Acad. Sci. Proc., 4th ser., vol. 3, pp. 95,. 111). 

Kern River group. Green and brown beds, gravels, sands, and clays, almost 

without fossils, but includes the Kern oil measures. Well exposed 1 or 2 miles 

«ast of Kern River oil field and elsewhere. Beds of gravel and conglomerate 

and frequently large boulders are characteristic of the group. Is a terrigenous 

rather than an organic deposit. Called Kern River group because the productive oil measures of the Kern River district are confined to it. The oil measures 

make up about half of the stratigraphic volume of the beds. Unconformably 

overlies Temblor group. Assigned to Neocene. [Now classified as Pliocene.]

J. B. Stevens, 1924 (Am. Assoc. Petroleum Geologists Bull., vol. 8, No. 1, p. 33). 

Kern River series. Gravel, sand, and clay, 2,000 feet thick. Is unconformably 

overlain by alluvium and terrace deposits and unconformably underlain by 

Monterey group (Miocene). Probably includes at base equivalent of Santa Margarita Miocene. Rest of formation assigned to Pliocene.

Hi. S. Fox, 1929 (Am. Assoc. Petroleum Geologists Bull., vol. 13, No. 2, p. 103). 

Kern River series. Unconsolidated sands and clays of fresh-water origin, and, in 

its more basinward phase, of interstratified marine Etchegoin sediments. At 

numerous places along eastern fringe of the valley these beds are lacking, but 

farther west they increase in thickness to several thousand feet within a short 

distance. These Kern River beds represent the entire series of deposits from 

early Pliocene to Recent time.

Kettle meta-andesite.

Pennsylvania:!: Northern California (Taylorsville region).

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). An extended series of lava flows 

and products of volcanic explosions. The principal rock is decidedly porphyritic, 

with many small phenocrysts of feldspar, some of hornblende, and, rarely, round 

grains of quartz, all embedded In a reddish-brown or gray partially crystalline 

groundmass containing small grains of plagioclase and quartz. Also includes 

considerable pale greenish-gray, generally nonporphyritic rock. Both types are 

Intimately associated with fragmental rocks, mainly tuffaceous but locally passing 

Into fine conglomerate and sandstone. Appears to have been erupted about the 

time the Robinson formation was deposited, but to be older than the Reeve 

meta-andesite.

Named for development around Kettle Rock, northeast of Taylorsville.

Kettleman lake bed.

Probably Pliocene: Southern California (Tulare Lake region).

J. G. Cooper, 1894 (California Acad. Sci. Proc., 2d ser., vol. 4, p. 167). A fossiliferous fresh-water deposit about 10 miles west of Tulare Lake, on the edge of what 

was probably a Pliocene lake about 20 miles long and 5 miles wide, or half as 

large as Tulare Lake is now, and south of west from it, in the western corner 

of Tulare County. Lies 600 feet above sea leyel. [Type locality not stated, but 

the beds are probably the fresh-water deposit mentioned as occurring on the 

west border of the Kettleman Plains.]

Kirker tuff.

Oligocene: Western California (San Francisco Bay region).

B. L. Clark, 1918 (California Univ. Pub., Dept. Geology Bull., vol. 11, pp. 54-111). 

In the Sobrante anticline, in the Concord quadrangle, the formation consists of 

about 100 feet of fairly Indurated white tuff beds, which contain a few minor 

layers of tuffaceous sandstone, the formation as a whole being very fine and 

homogeneous in texture, and disconformably overlain by the Concord formation 

and underlain by the San Ramon formation. At the type locality (on Kirker 

Creek, north of Mount Diablo) the formation consists (in descending order) of 

tuffaceous sandstone, 50 feet; rhyolitic white tuff beds with lentils of bluish 

tuffaceous sandstone, 350 feet; and sandstone, tuffaceous toward top, 50 feet, 

resting disconformably on the Markley formation and unconformably overlain 

by the San Pablo formation. In the latter region [Kirker Creek] the beds were 

included in the San Pablo by Turner (1898) and Weaver (1909).
GEOLOGIC UNITS OF CALIFORNIA 39

Kirker's Pass beds.

Miocene: Western California (Mount Diablo region).

J. P. Smith, 1910 (Jour. Geology, vol. 18, table opp. p. 226). [Kirker's Pass ftedff 

with Santa Margarita fauna appears In column headed Mount Diablo regionAssigned to middle Miocene and correlated with upper part of San Pablo.]

"Klamath schists."

" Klamath schist series."

Pre-Cambrian (?) : Northern California (Klamath Mountains). 

Terms used by O. H. Hershey (Am. Geologist, vol. 27, pp. 225-245, 1901) to 

include the Abrams mica schist (sedimentary) and the Salmon hornblende schist (intrusive).

Knoxville formation.

Lower Cretaceous (Shasta series) : California and Oregon.

C. A. White, 1885 (U. S. Geol. Survey Bull. 15, pp. 19-32). The strata of ttte 

Shasta group occupy only a few isolated areas In California and are in every 

case either unconformable with the rocks both above and below them or so 

disturbed that their stratigraphical relations are obscure. Judged by their 

fossils, two divisions of the strata are plainly indicated, and I shall designate 

the divisions as the Horsetown beds and the Knoxville beds, respectively.' The? 

Horsotown beds have been found mainly in Shasta County and the Knoxvlll© 

beds mainly in Lake, Colusa, Contra Costa, and Santa Clara Counties. The 

. ; .[ Knoxville beds are characterized by Aucella, which Is, so far as known, absent: 

from the Horsetown. The Horsetown fossils appear to represent the Gault and) 

the Knoxville fossils to represent the Lower Neocomian. There is probably a 

considerable hiatus between the Knoxville and Horsetown beds.

J. S. Diller and T. W. Stanton, 1894 (Geol. Soc. America Bull., vol. 5, pp. 435-464).. 

[Give detailed sections of the Horsetown and Knoxville formations and list their 

faunas.] The upper or Horsetown formation consists of about 6,000 feet off 

shales, sandstones, and conglomerates. The lower or Knoxville formation conr 

sists chiefly of shales, although many sandstones and calcareous layers occur; 

20,000 feet maximum thickness. The Horsetown formation is overlain by the 

Chico formation.

Some geologists refer the lower part of the Knoxville formation to the

Jurassic. 

Named for exposures at Knoxville, Napa County, Calif.

"Koipatoan series."

Triassic (Middle?) : Northern Nevada.

C. [R.] Keyes, 1923 (Pan-Am. Geologist, vol. 40, pp. 52, 59, 79). "Title adopted? 

from King's Humboldt Range section o£ Mid Triassic sandstones." Sandstones, 

2,000 feet thick, underlying Staran series and younger than Inyoan series. Of 

Mid Triassic age and covers all Mid Triassic of Nevada. " The early title of 

Koipatoan [Koipato series] for the entire Mid Triassic section of this region le, 

probably too comprehensive, and if the section in this folded belt is actually so 

thick as formerly considered several units of serial rank are doubtless represented."

Same as Koipato formation, which was named for development in West 

Humboldt Range, Humboldt County, Nev., the Indian name for whicia 

is Koipato.

Kreyenhagen shale.

Oligocene? (may be Eocene) : Southern California (Diablo Range).

F. M. Anderson, 1905 (California Acad. Sci. Proc., 3d ser., vol. 2, pp. 163-168))'... 

Ereyenhagen shales. Brown bituminous or carbonaceous shale, more or less 

sandy in lower part, 600 feet exposed on hills a few miles north of Coallnga, 

but thickens to south and southeast, and at Kreyenhagen wells, for which it IB 

named, it is about 900 feet thick. Thins to 250 or 300 feet at the head of the 

Jacalitos and on Zapata Chlno. Underlie Domijean sands and overlie AvenaBi 

sandstones. Of Eocene age.
40 GEOLOGIC UNITS OF CALIFOBNIA

For many years the Kreyenhagen shale has been defined as the shale 

unconformably underlying the Vaqueros sandstone and overlying, 

probably unconformably, the Tejon formation in the Coalinga and 

neighboring districts.

F. E. von Estorff, 1930 (Am. Assoc. Petroleum Geologists Bull., vol. 14, No. 10, pp. 

1321-1336). Type locality of Kreyenhagen shale is on Canoas Creek, about 20 

miles south of Coalinga, Fresno County. Its maximum thickness in vicinity of 

Canoas Creek and Big Tar Canyon is 1,000 feet. It con'sists of shale with a 

very few lenticular beds of sandstone and a few lenses or nodules of limestone. 

The sandstone is common only at base of the formation, where the Kreyenhagen 

seems to grade into a transitional friable white sandstone interbedded with 

sandy clay shale which is tentatively included in the Kreyenhagen. It here 

overlies, with seeming conformity, but possibly with unconformity, the Doraengine 

sandstone, of upper middle Eocene age, and unconformably underlies Temblor 

sandstone, of lower middle Miocene age.

La Jolla formation.

Eocene: Southern California (San Diego County).

B. L. Clark, November 4, 1926 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 16, 

No. 5, pp. 103, 111, 117). At present there is in press a monograph on the 

 stratigraphy and fauna of the Eocene beds of San Diego County, by Marcus A. 

Hanna. In that monograph he refers the major portion of this section to a 

new formation, which he calls the La Jolla and which he correlates tentatively 

 with the Domengine formation described in this paper. Many species are common to the La Jolla and Domengine formations. Overlying the La Jolla are the 

Poway conglomerates, which previous workers have referred to the Pliocene but 

which Hanna has shown conclusively are of Eocene age, and he has tentatively 

correlated them with Tejon.

M. A. Hanna, 1926 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 16, No. 7, pp. 

187-246). In previous publications the Delmar sand, Torrey sand, and Rose 

Caiion shale have been mapped together and referred to the Tejon Eocene. In 

the present paper they are recognized as a distinct formation and so designated 

under the name La Jolla formation. The whole of the La Jolla formation probably represents deposition along an oscillating coast. For the most part the 

species found in the La Jolla formation are not present in either the Tejon or 

Meganos. The La Jolla formation is therefore considered as stratigraphically 

between the Meganos [as restricted by B. L. Clark] and Tejon formations, or 

approximately equivalent to the Domengine formation.

Landavista terrace material.

Quaternary: Southern California (San Diego County).

M. A. Hanna, 1926 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 16, No. 7, pp. 

187-246). Sand and gravel scattered over the Landavista terrace, which is a 

cut terrace in the La Jolla quadrangle. Color prevailingly red and brown. 

Boulders largely from Poway conglomerate. Thickness 25 to 100 feet. No 

fossils found, so that its marine origin has not been determined with certainty.

" Lang division."

Tertiary: Southern California (Los Angeles County).

O. H. Hershey, 1902 (Am. Geologist, vol. 29, pp. 349-372). A great bed of gravel 

and sand of buflf color; red and brown lava cobbles plentiful. Thickness 3,000 

feet. Has appearance of delta of a large river flowing westward on site approximately of Soledad Canyon. May be marine in western part of basin. Conformably underlies Soledad division and unconformably overlies Mellenia series. 

Named for exposures at Lang, Los Angeles County.

W. S. W. Kew, 1924 (U. S. Geol. Survey Bull. 753, p. 81). The "Lang division" 

of Hershey is thought by writer to be equivalent, in greater part at least, to 

the upper part of the Mint Canyon formation (upper Miocene) of this report.

Las Posas formation.

Pleistocene: Southern California (Ventura County).

E. D. Pressler, 1929 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 18, No. 13, 

pp. 325-345). Las Posas formation. In South Mountain area consists of 

1,500 ± feet of loose sands and conglomerate alternating with beds of silty sand
GEOLOGIC UNITS OF CALIFORNIA 41

and gravel. In Las Posas Hills it consists of 75 feet of light-colored conglomerates, and yellow to tan, One to medium grained sands. Overlaps Pico In 

some places, and in otber places appears to rest conformably on Santa Barbara 

beds (Upper Pico, Pliocene). Divided into Long Canyon member (above) and 

Kalorama member (below). Is marine Pleistocene, equivalent to Upper San 

Pedro, Lower San Pedro, and " San Pedro Pliocene " of Deadman's Island. Is 

equivalent to Saugus, which typically is terrestrial. "It seems unsatisfactory 

to use the same name for both marine and terrestrial strata, which are so 

situated that their integrating phases can not be traced, and for this reason 

the term Las Posas formation has been applied to the beds containing the 

Kalorama and Long Canyon faunas that come above the cool-water Santa 

Barbara in the western part of the basin."

Las Virgenes sandstone.

Eocene (lower) : Southern California (Ventura County).

R. N. Nelson, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 11, 

pp. 400-401, map). Beds of coarse-grained sandstone, conformably overlying 

and in part grading laterally into the Simi conglomerate and conformably 

underlying and in part grading laterally into the marine member of the Martinez 

group on the west side of the faults south of Simi Valley. Thickness 311 feet 

1 mile west of head of Las Virgenes Canyon. Is middle division of Martinez 

group (lower Eocene). Named for typical development at head of Las Virgenes 

Canyon, on south side of Simi Hills, Ventura County.

"Latrania sands."

Miocene (lower) : Southern California (Imperial County). 

G. D. Hanua, 1926 (California Acad. Sci. Proc., 4th ser., vol. 14, No. 18, p. 435). 

[See quotation under Imperial formation.] "Contains a large assemblage of 

marine M'ollusca." [Letter from G. D. Hanna, dated August 19, 1926, states 

that the name " is derived from latrans, the Latin name for a barker, such as a 

dog or a wolf," the rocks being exposed in Coyote Mountain, and the name 

Coyote having been previously used.] :

An unclifferentiated part of Imperial formation. See W. P. Woodring, 1930, 

under Imperial formation.

Leaning Tower quartz monzonite.

Probably Cretaceous: Yosemite National Park.

F. C. Calkins, 1930 (U. S. Geol. Survey Prof. Paper 160, p. 123, map). On fresh 

fracture of dull-gray color and moderately fine texture. On weathered surfaces 

deeply decayed and rusty.

Named from fact that it forms a considerable part of slopes of Leaning 

Tower, Yosemite National Park.

Leona rhyolite.

Pliocene (?) : Western California (San Francisco region). ° 

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Pyritic lava that forms a discontinuous belt along the west front of the Berkeley 

Hills, from Hamilton Gulch in Berkeley nearly to Decoto, a distance of 21 miles. 

Reaches its maximum width a little south of Leona Heights, Alameda County. 

Is in general an acidic or rhyolitic lava, but it includes local masses of darker, 

more basic rock. Is of about the same age and the same chemical composition 

as the Northbrae rhyolite, but has certain physical differences. Thickness about 

500 feet. Classified as Pliocene, but Its age is not proved, and it may belong 

to some other series of the Tertiary.

Lion sandstone.

Miocene (lower): Southern California (San Bernardino Mountains).

F. B. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 9, 

pp. 344, 375-376, 378, map). Lion scmdstone. Sandstone containing a small 

marine fauna consisting of forms found by Kew in Carrizo Creek region, which 

are regarded by T. W. Vaughan as not older than lower Pliocene. This fauna 

belongs to that of the Gulf of California and not to that of southern California 

coast. Is older than Hathaway formation and younger than Potato sandstone.
42 GEOLOGIC UNITS OP CALIFORNIA

W. P. Woodring, 1931 (Carnegie Inst. Washington Pub. 418, pp. 1-25). Lion sandstone of F. E. Vaughan is late lower Miocene and of same age as the marine 

imperial formation as here redefined.

. Named for Lion Canyon, Riverside County, near which (on third ridge to 

west of the canyon) it crops out.

Little Chief porphyry.

Age (?): Southeastern California (Inyo County).

F. MacMurphy, 1930 (Econ. Geology, vol. 25, p. 311). Intrudes Telescope group 

(lower Paleozoic?). [Derivation of name not stated.]

" Little Grizzly Creek beds."

Pennsylvanian: Northern California (Taylorsville region).

H. W. Turner, 1894 (Am. Geologist, vol. 13, pp. 230-231). Little Grizzly Greek 

beds.1 At the southwest base of Mount Ingalls [Plumas County, in Downieville 

quadrangle], by the road to the Cascade gravel mine and to the east of Little 

Grizzly Creek, there occurs a highly metamorphic tuff, in a fine-grained portion 

of which fossils were collected, which were identified by Charles Schuchert as 

Upper Carboniferous and closely related to the Robinson beds. These beds are 

stratigraphically nearly in a line with the Robinson beds.

H. W. Turner, 1894 (U. S. Geol. Survey Fourteenth Ann. Rept, pt. 2, p. 448). Little 

Grizzly Creek beds, which consist of highly metamorphic tuff containing many 

fossils, will probably be correlated with the Robinson formation. [In the 

Downieville folio, No. 37, these beds were mapped by Turner as Robinson formation. The latter name has priority over " Little Grizzly Creek beds."]

Lloyd zone.

An oil zone, 2,620 feet thick, in Pico formation of Ventura County. Top 

' lies 1,300 feet below base of Gosnell shale zone.

Lone Mountain limestone.

Silurian and Upper Ordovician: Northern Nevada.

Arnold Hague, 1883 (U. S. Geol. Survey Third Ann. Rept., pp. 253, 262, 267). Light 

gray siliceous rock, with all traces of bedding obliterated, and with black gritty 

beds at base. Thickness of formation 1,800 feet. Unconformably overlies Eureka 

quartzite and underlies Nevada limestone (Devonian).

The formation contains Silurian fossils of Niagaran age in upper part, and 

Upper Ordovician fossils of Richmond age in lower part.

Type locality, Lone Mountain, northeast of Eureka, Nev. Has also been 

mapped by S. H. Ball (U. S. Geol. Survey Bull. 308, 1907) in Inyo 

County, Calif.

Long Canyon member (of Las Posas formation).

Pleistocene: Southern California (Ventura County).

E. D. Pressler, 1929 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 18, No. 13, 

pp. 325-345). Long Canyon member (also Long Canyon horizon). Cross-bedded 

sands, some thin layers of calcareous sand, and a group of tan to yellow, finegrained sands. Thickness 200 feet. Upper part of Las Posas formation. Contains a warmer-water (marine Pleistocene) fauna than underlying Kalorama 

member. Occurs in Long Canyon, on south slope of South Mountain, Ventura 

County. Correlates with Upper San Pedro.

Lopez fanglomerate.

Quaternary: Southern California (San Gabriel Mountains).

M. L. Hill, 1930 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 19, No. 6, pp. 141, 

144). Lopess formation. The older and topographically higher Quaternary 

fanglomerate, which blankets part of ridge tops on either side of Lopez Canyon. 

Composed of subangular and poorly sorted fragments of gneiss and granitic rocks 

up to 2 feet in diameter. Is of browner color than the younger Kagel formation. 

Overlies Saugus formation with angular unconformity.

Los Angelan epoch.

Pleistocene: Southern California.

O. H. Hershey, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 3, pp. 1-29). 

Los Angelan epoch (erosion). Represented by valley of Los Angeles River in
GEOLOGIC UNITS OF CALIFORNIA 43-

city of Los Angeles. The three middle terraces of San Pedro Hill belong to this 

epoch, which preceded San Pedran epoch and followed Bed Bluff epoch. (See 

under Sierran.)

Los Cerritos beds. See under Deadman Island beds.

"MicCloud formation."

Pennsylvanian and Mississippian: Northern California (Redding region).

J. P. Smith, 1894 (Jour. Geology, vol. 2, pp. 592-593). The McCloud formation 

(H. W. Fairbanks MS.) is especially well developed in the region of McCloud 

River in Shasta County, and from this it receives its name. Divided into 

Balrd shales (Lower Carboniferous), 500 feet thick, overlain by McCloud 

limestone (Upper Carboniferous), 2,000 feet thick. Is overlain by McCloud 

shales, the basal formation of the Pitt formation, and underlain by the Sacramento formation (Kennett limestone and shales).

Unnecessary name with conflicting usages.

McCloud limestone.

Pennsylvanian: Northern California (Redding region).

H. W. Fairbanks, July, 1894 (Am. Geologist, vol. 14, pp. 29-30). "The limestonepeaks along the east side of the McCloud extend in a north and south direction, but the strike of the strata is about N. 30° W. The repetition of the 

limestone bodies in the north and south direction, as well as that of the fossiliferous beds along the river, is undoubtedly due to sharp folding or faulting.. 

If this were not so the thickness of the limestone would be immense. The 

McCloud limestones are considered by Mr. [J. P.] Smith as belonging to the 

Upper Carboniferous."

J. P. Smith, October, 1894 (Jour. Geology, vol. 2, pp. 592, 599-601). Immediately 

above the Baird shales, and probably conformably with them, lies the McCloud 

limestone, consisting of about 2,000 feet of massive limestones and marbles 

of the McCloud River, rich in corals and brachiopods. Underlie the McCloud 

shales. Form upper division of McCloud formation.

Now treated as a distinct formation, of Pennsylvanian age. Overlies Baird 

shale and underlies Nosoni formation.

"McCloud shales."

Pennsylvania!!: Northern California (Redding region).

H. W. Fairbanks, July, 1894 (Am. Geologist, vol. 14, p. 30). " MoOloud shales. 

The uppermost horizon of fossiliferous strata on the McCloud occurs about 20' 

miles above the Fisheries on the east side of the river. Here is found a calcareous argillite rich in several species of Productus, besides other forms,, 

which, according to Mr. Smith, belong in the upper portion of the Carboniferous. 

These argillitic limestones and the associated shales are embraced under the 

designation McCloud shales."

J. P. Smith, October, 1894 (Jour. Geology, vol. 2, pp. 592, 601-602). McCloud 

shales. Siliceous and calcareous shales and, conglomerates, with Upper Carboniferous fauna at the base. Occurs on east bank of McCloud River, about 

20 miles north of the United States fisheries. Thickness, 1,000 feet. Basal 

formation of Pitt formation. Underlies Pitt shales and overlies McCloud 

limestone.

Same as Nosoni formation.

McKittrick formation.

Pliocene and lower Pleistocene(?): Southern California (McKittrickSunset district).

R. Arnold, 1909 (U. S. Geol. Survey Bull. 390, p. 22). At most localities along, 

the flanks of the DJablo and Temblor Ranges south of the Coalinga district it 

is impossible to separate the post-Santa Margarita(?) Tertiary formations, and 

to these beds the equivalent of the Jacalitos, Etchegoin, and possibly Tulare 

formations of the Coalinga district the name McKittrick formation has been 

given in the McKittrick district (R. Arnold and H. R. Johnson, U. S. Geol. 

Survey Bull. 406). This name was chosen because of the importance of thebeds in that district, the basal members yielding the petroleum found in th°- 

productive McKittrick field.

17462 31 i
44 GEOLOGIC UNITS OF CALIFORNIA

JR. Arnold and R. Anderson, 1910 (U. S. Geol. Survey Bull. 398, p. 79). To the 

south of the Coalinga district the McKittrlck 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. 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 

day beds. Thickness ranges from 1,300 to possibly 2,500 feet. Unconformably 

overlies Monterey and Santa Margarita (?) formations and is unconformably 

overlain by Quaternary deposits. Is equivalent to Jacalitos, Etchegoin, and 

Tulare formations of Coalinga district.

R. Arnold and H. R. Johnson, 1910 (U. S. Geol. Survey Bull. 406, pp. 74-90).

[Same definition as above.] Named for exposures half a mile south of McKittrick, Kern County.

McLure shale.

Miocene or Pliocene: Southern California (Fresno and Kings Counties).

G. Heuny, 1930 (Am. Assoc. Petroleum Geologists Bull., vol. 14, No. 4, p. 403). 

MoLure aluile is a name given by writer to the brown shale of southern Coalinga 

region, Fresno and Kings Counties, previously termed Santa Margarita (?) shale 

on the geologic maps of United States Geological Survey. It is found, however, 

that this shale lies with an angular unconformity on Santa Margarita sandstone 

(Miocene), and that the Etchegoin (Pliocene) lies unconformably on the shale. 

Whether it is upper Miocene or lowest Pliocene in age has not been determined. 

Average thickness 800± feet. Base consists of 30 ± feet of light-gray coarse 

sandstone with concretions. Borders McLure Valley on nearly all sides. Type 

locality is a canyon crossing Tent Hills south of Avenal Creek, near west line of 

sec. C, T. 24 S., R. 17 E. In Zapata Canyon it overlies Temblor sandstone. 

In Devils Den it rests unconformably on Monterey shale.

Manix lake beds.

Pleistocene: Southern California (San Bernardino County).

J. P. Buwalda, 1914 (California Univ. Pub., Dept. Geology Bull., vol. 7, p. 444). Lake 

beds of arenaceous clays and fine argillaceous sands, both of light grayish-green 

color; quartz, feldspar, and mica are the abundant coarser constituents. The 

most notable characteristic is the evenness, persistence, an<? parallelism of the individual strata. Thickness about 75 feet, but the beds thin out gradually toward 

the west. Believed to be slightly younger than the Pleistocene fauglomerates. 

Are deposits of an extinct lake named Manix Lake. Well exposed along Mohave 

River 2 miles southeast of Manix, about 120 miles northeast of Los Angeles.

Maricopa shale.

Miocene (upper and middle) : Southern California (Sunset-Midway district) .

W. A. English, 1916 (U. S. Geol. Survey Bull. 621, pp. 191-215). The Maricopa 

shale, which overlies the white sandstone of1 the Vaqueros formation south of 

Cuyama Valley and which forms the upper part of the Monterey group, has been 

mapped separately only as far eastward as Salisbury Canyon [about 25 miles 

west of the Maricopa type locality]. It consists of about 1,700 feet of brown 

shale, in which reef-like outcrops of white sandstone are locally prominent. 

The shale is made up mostly of clastic fragments, locally clayey, and not 

noticeably diatomaceous. It is unconformably overlain by Santa Margarita 

formation. The name Maricopa shale is used in the report on the Sunset-Midway 

region [afterwards published as U. S. Geol. Survey Prof. Paper 116, 1920] for a 

great thickness of diatomaceous shale which in the preliminary report was 

mapped as Monterey shale. [The above definition of Maricopa shale (the first 

in print) applies the name to only the lower part of the typical Maricopa shale, 

as defined below by Pack, and the name Maricopa is no longer applicable in 

Cuyama Valley.]

R. W. Pack, 1920 (U. S. Geol. Survey Prof. Paper 116). Mainly thin-bedded siliceous, 

diatomaceous shale containing numerous thin calcareous layers and in the lower 

part a relatively small amount of arkosic sandstone, but in the upper part numerous lenses of arkosic sandstone and boulder beds. Typically developed in the 

gulch that drains northward through sees. 13 and 24, T. 11 N., R. 24 W., where 

exposed thickness is about 4,800 feet. Rests conformably on Vaqueros formation and is unconformably overlain by beds which are here tentatively called
GEOLOGIC UNITS OF CALIFORNIA 45

Etchegoiu formation but which probably include at base a representative of the 

Jacalitos formation. The upper part of the diatomaceous shales included in the 

Maricopa is equivalent to the Santa Margarita formation as mapped in the 

western part of the San Emigdio Mountains, which contains a typical Santa 

Margarita fauna and overlaps onto the Vaqueros and Tejon formations. 

Named for exposures west of Maricopa and Maricopa Flat, Kern County.

Marin sandstone.

Jurassic (?): Western California (San Francisco region).

R. Arnold, March, 1902 (Science, new ser., vol. 15, table on p. 416). Marin sandstone, 1,000 feet thick', underlies San Miguei'cherts and overlies Sausiilito cherts. 

A subdivision of the Franciscan.

A. C. Lawsou, February, 1903 (Geol. Sue. America Bull., vol. 13, table on pp. 544- 

545). [Same as above.]

A. C. Lawson, 1914 (U. S. Geol. Survey Atlas, San Francisco folio, No. 193). 

Massive dark-gray sandstone, obscurely stratified. Thickness 1,000 feet. Underlies Ingleside chert and overlies Sausalito chert. Included in Franciscan group. 

Named for occurrence on Marin Peninsula, Marin County.

4* Marino" formation. Incorrect spelling of Moreno formation.

.Mariposa slate. i

Upper Jurassic: Northern California (Mariposa, Calaveras, and neighboring counties).

G. F. Becker, 1885 (U. S. Geol. Survey Bull. 19, pp. 18-23). Naripoaa beds. An 

immense thickness of highly metamorphosed auriferous slates occurring along the 

foothills from M'ariposa to Nevada, and containing Aucella, Belenmites, and other 

fossils. Thin-bedded strata prevail, and siliciflcation and scrpentinization are 

predominant characteristics. The beds are upturned into a nearly vertical position, and are unconformably overlain by the Cliico beds. Regarded as identical 

with the Knoxville beds.

!Becls of sandstone and conglomerate are also included in the Mariposa 

slate, and contemporaneous greenstone is associated and in part interbedded with the formation. In 1910 (Jour. Geology, vol. 18, charts 

opp. pp. 217 and 221) J. P. Smith restricted the name Mariposa to the 

lower part of the Mariposa slate.of previous reports, or to the slates of 

the Gold Belt carrying Aucella erringtoni and Gardioceras alternans, 

and applied the new name Colfax formation to the upper part of the 

Mariposa, or to the " tuffs and shales of the Gold Belt with Perlsphimctes colfaxi." The U. S. Geological Survey uses the original 

broad definition of Mariposa and classifies it as older than Knoxville.

Named for occurrence on the Mariposa estate, in Mariposa County.

JMarkley formation.

Oligocene: Western California (San Francisco Bay region).

B. L. Clark, 1918 (California Univ. Pub., Dept. Geology Bull., vol. 11, pp. 54-111). 

Heterogeneous assemblage of beds, mostly of shallow-water origin but possibly 

in part continental. Thickness 3,300 feet. Lithology very different from that 

of San Ramon formation, but very probably it is contemporaneous, at least in 

part, with the San Ramon. The upper 1,300 feet consists of alternating layers 

of clay shale, sandy shale, and sandstone and contains a meager fauna. The 

lower 2,000 feet is predominantly sandstone and contains no fossils. In former 

paper writer included the latter beds in the Tejon, but he now believes them to 

be lower Oligocene. Disconformably underlies Kirker formation. The Kirker 

and Markley formations compose the San Lorenzo series in this area. Named 

for exposures in vicinity of Markley Canyon, Mount Diablo region.

Mark West andesite.

Pliocene: Northern California (Souoma County).

V. C. Osmont, 1904 (California Univ. Pub., Dept. Geology Bull., vol. 4, pp. 58-87). 

Thickness varies up to 1,500 feet. Conformably underlies Sonoma tuff. la 

certainly post-San Pablo and probably post-Orindan.

.Apparently named for Mark West Springs, Sonoma County.
46. GEOLOGIC UNITS OF. CALIFORNIA

Martinez formation. : , Eocene (lower): Western California.

W. M. Gabb, 1869 (California Geol. Survey, Paleontology,-.vol. 2, p. xiii, as reported 

by J. D. Whitney from an unpublished paper by Gabb, and footnote by Gabb 

on p. 129). The term Martinez group is proposed provisionally for the upper 

portion of " Division A" of the California reports, to include a series of beds, 

of small geographical extent found at Martinez [Contra Costa County] and' 

on the northern flank of Monte Diablo. "It may eventually prove to be worthy 

of ranking only as a subdivision of the Chlco group." Underlies Tejon groupand overlies Chico group.

T. W. Stanton, 1896 (U. S. Geol. Survey Seventeenth Ann. Kept., pt. 1, p. 1028). 

" The Martinez group of the California Survey is not a simple formation that 

can be considered a mere subdivision of the Chico but consists of two distinct 

portions, one of which is Cretaceous and inseparable from the Chico, while 

the other is Eocene and is here classed as Lower Tejon."

J. C. Men-Jam, 1897 (Jour. Geology, vol. 5, pp. 767-775). Martinez group. Thename Martinez is here applied to that portion of Gabb's Martinez group which, 

remains after the removal of the Chico Cretaceous element. Is the Lower Tejoa 

of Stanton and consists of sandstones, shales, and glauconitic sands. At 

Martinez it appears to be conformably overlain by the Tejon and conformably 

underlain by the Chico, although an unconformity probably exists at its base. 

It differs from the adjoining formations in the slightly different aspect of it£ 

sandstones and. the presence in them of considerable quantities of glauconite. 

The sandstones of the Martinez are grayish, those of the ChSco yellowish or 

bluish, and those of the Tejon white to dull red. The fauna also differs from 

the Chico and Tejon faunas and is a unit, although it grades to some extent 

into the Tejon fauna.

The present generally accepted definition of Martinez formation is for thebeds unconformably underlying the Meganos formation, unconformably 

overlying the Chico formation, and reaching a maximum thickness of 

3,500 feet or more. The rocks consist of conglomerate, sandstone,, 

and shale characterized by fossils of lower Eocene age. See definition 

of Meganos formation.

Martinez marine member.

Eocene: Southern California (Ventura County, south of Sinii Valley).

R. N. Nelson, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 11). 

On the southwest side of the faults the Martinez group has been separated into 

the three following lithologic units: Martinez marine member, Las Virgene* 

sandstone, and Simi conglomerate. These members grade into one another 

both laterally and vertically, but with sufficient abruptness that their boundaries may be accurately mapped. The fossiliferous Martinez marine member 

of the Martinez group consists of 800 to 2,400 feet of beds that " may be subdivided into a sandstone above and a shale- below, but their boundaries are 

t&o indefinite to be indicated on the map. With the exception of about 200- 

feet of light-gray shale at the top the marine member of the Martinez consists of medium to fine grained sandstones with occasional beds of coarsegrained sandstone in the lower portion."

Marvel limestone.

Lower Paleozoic (?) : Southeastern California (Inyo County).

F. MacMurphy, 1930 (Econ. Geology, vol. 25, pp. 309-310, and map). Marvel dolomitic limestone. Essentially a light bluish-gray cherty rock, showing frequent 

irregular mottling due to brecciation. All traces of organic structure destroyed. 

Age unknown. Is complexly folded. From its general characteristics a Lower 

Paleozoic age is assumed. Underlies Surprise formation, usually with gradation from a true limestone to a true schist for a distance of 5 to 30 feet. 

Exposed along Marvel Canyon. [" Interbedded schist in Marvel dolomitic limestone" is mapped separately on the geologic map.]

Marysville formation.

Eocene (middle) : Northern California (Sutter County).

Howel Williams, 1929 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 18, pp. 112,. 

121-124). Marysville formation. Loose buff sands, usually traversed by 

parallel strings of ferruginous calcareous concretions and by thin lenticular
-GEOLOGIC UNITS OF CALLFOENIA 47

masses of compact green-gray sandstone and, more rarely, limestone. In many 

places this sandy facies Is associated with a thick development of green-gray 

glauconitic shales that weather to a deep reddish brown soil. In some places, 

on west side of the Buttes, there Is a JlfeZania-bearing grit at base. Lithology 

and thickness are very variable over small areas. The ferruginous concretions 

range in size from a hen's egg to 4 or 5 feet long. Thickness 300 to 600 feet. 

Dlsconformably overlies Chico beds, and underlies, with minor disconformlty, 

the White lone sands. Fauna referred by B. L. Clark to Meganos (middle 

Eocene). The formation is present at Marysville and on Marysvllle Buttes.

3Iatilija sandstone member.

Eocene: Southern California (Ventura County).

P. F. £err and H. G. Schenck, 1928 (Geol. Soc. America Bull.,.vol. 39, p. 1090). 

Matilija sandstone member. Basal member of Tej'on formation. Comprises 

beds 2,500± feet thick, In which sandstone predominates over shale. The 

resistant massive arkose at base forms convenient guide for separating from 

underlying Chico formation, upon which it rests without apparent angular 

discordance. Is disconformably overlain by Cozy Dell shale member. Well 

exposed at type locality (in canyon at Matilija Springs), also on top of Topatopa Bluff and on San Cayetano Mountain. Near the springs is a bed of llgnitic facies distinguished by abundant mollusks .embedded In a green and 

purplish sandy shale, and the same bed is found farther east at same position 

in geologic column.

Meganos formation.

Eocene (middle) : Western California.

B. L. Clark, 1918 (Geol. Soc. America Bull., vol. 29, pp. 94, 281-296). "The name 

Meganos group is given to the new group situated between typical Martinez and 

typical Tejon. It Is believed that deposits of the Meganos group have a wide 

distribution throughout the Coast Ranges of California. In certain localities 

they have been referred to the Martinez group and at other places to the Tejon." 

Unconformably underlies typical Tejon and contains a faunal representative 

differing considerably from that of typical Tejon and also differing from the 

typical Martinez fauna of the lower Eocene. Unconformably overlies typical 

Martinez group. Includes the Turritella andersoni beds.

B. L. Clark and R. B. Stewart, 1925 (Geol. Soc. America Bull., vol. 36, p. 227), and 

B. L. Clark, 1926 (California Univ. Pub., Dept. Geol. Scl. Bull., vol. 16. No. 5). 

[Restrict Meganos to the lower part of Meganos as above defined, and apply the 

name Domengine to the beds between typical Tejon and Meganos restricted. 

See second entry under Domengine formation.]

.. The United States Geological Survey includes the Domengine formation of

Clark and Stewart in the Meganos formation.

Named for exposures on Meganos ranch or land grant, southeast of Martinez, Contra Costa County. In 1927 (California Univ. Pub., Dept. GeoL 

Sci. Bull., vol. 17, p. 71) B. L. Clark.and A. O. Woodford stated that 

the type section of Meganos restricted is a strip beginning about 1% 

miles cast and a little north of Clayton and ending in vicinity of Byron 

Hot Springs.

 "Mellenia series."

Miocene: Southern California.

O. H. Hershey, April, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 3, pi. 1, 

map). [On legend of map of a part of southern California the' Mellenia series 

appears between San Pablo series below and uppe'r Pliocene above. ]

O. H. Hershey, 1902 (Ain. Geologist, vol. 29, pp. 349-372). Fresh-water sediments, 

1,700 feet thick, composed of conglomerates, shales, and sandstones, unconformably underlying the Lang division and believed to. be younger than the San Pablo 

formation.

W. S. W. Kew, 1924 (U. S. Geol. Survey Bull. 753, p. 52). As the term "Mellenia," 

so far as could be ascertained, is not a place name, and Its origin Is doubtful, 

this series of strata is here renamed, to correspond to the rule of nomenclature 

of the United States Geological Survey, Mint Canyon formation, the beds being 

particularly well developed in the Mint Canyon region.
48 GEOLOGIC UNITS OP CALIFORNIA

Merced formation.

Pliocene: Western California (San Francisco Bay region).

A. C. Lawson, 1893 (California Univ. Pub., Dept. Geology Bull., vol. 1, pp. 142-151). 

Merced series. For convenience the Pliocene rocks here referred to will be designated the Merced series, from Lake Merced, which lies in a structural or synclinal depression of the Pliocene terrane, to the south of the city. The base of 

the series is observable at Mussel Kock. The basal bed is a stratum of partially 

carbonized forest material. Is a local or delta accumulation. Very fossiliferous. 

The delta- gravels on: the San Beiiito [on p. 153 casually called San BenitO' 

gravels] are the direct equivalent of the Merced series.

The Merced formation (marine) in the San Francisco region re.sts uucouformably on the Pinole tuff. In the Santa Cruz region it rests on the 

Purisima formation. It is considered equivalent to the noumarine 

Orinda formation and older than the Berkeley group.

Merritt sand.

Pleistocene: Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193).. 

Marine sand, 30 feet thick, unconformably overlying San Antonio formation and. 

unconformably underlying Temescal formation. Forms the sand underlying the 

cities of Oakland, and Aliimeda-. - Named -/for its occurrence on Lake = Merritt, in. 

the city of Oakland. Thickness 44 feet!

Meyer oil zone.

Name applied to tlie lower oil zone (consisting of 850 or 860 feet of brown, 

shale and sandy brown shale) in the Santa Fe Springs field, Los 

Angeles County. Contains oil at three distinct horizons. Is capped 

by the Bell oil zone.

Middle Park formation.

Lower Paleozoic (?) : Southeastern California (Inyo County). 

See under Telescope yroup. Derivation of name not stated.

Millerton formation.

Lower and middle Pleistocene: Western California (north of San Francisco Bay region).

R. E. Dickerson, 1922 (California Acad. Sci. Proc., 4th ser., vol. 11, No. 19, with, 

maps). Fossiliferous marine deposits, unconformably underlying Tomales 

formation and overlying Merced group and its correlative the Sonoma group. 

The best stratigraphic section seen (in headland 1^ miles northwest of Millerton station:)';'consisted (in descending order.) of (1) 23 fe<;t of carbonaceous, 

tan-colored"1 sandstone-and dark-gray shale ; (2) prominent conglomerate 2 

feet thick; (3) 85 feet of carbonaceous tan-colored sandstone and dark-gray 

shale with marine fossils in middle part; and (4) 50 to 65 feet of conglomerate 

at base.

Named for exposures in headland near Millerton station, Marin County.

Millett clay.

Southeastern California (Inyo County) and southwestern NevacUi.

C. [R-] Keyes, 1923 (Pan-Am. Geologist, vol. 40, pp. 52, 61, 79). Millett clays. 

Named for old Millett borax camp, in Furnace Canyon [east of Death Valley,. 

Inyo County, Calif.], which was situated directly upon the principal boratebearing beds, which appear to be Miocene, and separated from higher clays 

of similar character by marked unconformity. Thickness, 1,000 feet. Unconformably below Negra clays and above Redhill sandstones. Top formation of 

Furnacian series in Nevada.

Milton formation.

Jurassic (?) : Northern California (Downieville region).

H. W. Turner, 1894 (Am. Geologist, vol. 13, pp. 232-234). Milton series. Comparatively little altered sediments containing a large amount of fragmental
GEOLOGIC UNITS OF CALIFORNIA 49

diabaslc material with some quartzitc, flue-grained reddish clastic rocks, a variegated breccia, and a few limestone lenses. Considered older than Mariposa 

slate and younger than Sailor Canyon formation.

Named for exposures in the neighborhood of Milton, an old stage station 

on Middle Fork of Ynba River, in Downieville quadrangle.

Mineral King beds.

Triassic (?) : Southern California (Tulare County).

H. W. Turner, 1894 (Am. Geologist, vol. 13, p. 231; U. S. Geol. Survey Fourteenth 

Ann. Kept, pt. 2, p. 451): Clay slate, 'mica'-schist,'quartzite; and crystalline 

limestone, exposed at the old mining camp of Mineral King, about 15 miles 

southwest of Mount Whitney, at the headwaters of Kaweah River, TulareCounty. Assigned to Triassic (?) on basis of poorly preserved fossils.

Mint Canyon formation.

Miocene (upper) : Southern California (Los Angeles County).

W. S. W. Kew, 1923 (Am. Assoc. Petroleum Geologists Bull., vol. 7, pp. 411-420). 

Land-lafd deposits locally developed in vicinity of Mint Canyon, a branch of 

the upper part of Santa Clara River -north of San Gabriel Mountains. Contains good vertebrate faunas at several horizons. Rests unconformably on 

beds that are probably equivalent to the Sespe formation. Is in places overlain 

by strata containing an upper Miocene fauna and tentatively correlated with 

the Modelo formation, and'in other places it: lies-unconformably-beneath the 

Pico formation. [In U. S. Geol. Survey Bull. 75?., 1924, Kew gives the thickness of the Mint Canyon formation as 4,000 ± fret and states that the name 

is substituted for " Mellenla " because that name is not geographic.]

Modelo formation.

Miocene (upper) : Southern California (Ventura and Los AngelesCounties).

G. H. Eldridge, 1907 (U. S. Geol. Survey Bull. 309). Consists of 1,700 to 6,000' 

feet of strata, divided into a lower sandstone, massive and heavy bedded, 200 

to 2,000 feet thick; overlain, by 400 to 1,600 feet of earthy shale, gray to 

brown, with limestone concretions that weather yellow; succeeded by the 

upper sandstone member, about 900 feet thick and similar to the lower sandstone member except that it is nonconcretionary and is thinner bedded. The 

top member of the Modelo consists of a body of brown, gray, or yellowish 

shale of uncertain thickness (owing to the erosion unconformity above it),, 

but variously estimated at between 200 and 1,500 feet. The upper shale 

member is indistinguishable from the shale between the two sandstones; both 

vary from granular siliceous to earthy and fissile, and both carry calcareous 

layers and here and there lenticular limestone concretions. Rests on Vaqueros 

sandstone [younger than true Vaqueros, according to Kew] and is unconformably^ overlain, by ' Fernando formation:. The'' formation, is well -developed . in 

Hopper Canyon and at the head of Modelo Canyon, Ventura County.

W. S. W. Kew, 1924 (U. S. Geol. Survey Bull. 753). The' beds called Vaqueros 

sandstone by Eldridge are, younger than true Vaqueros sandstone, and Modelo 

formation is here redefined to include the Modelo formation and the 2,000 to 

3,000 feet of so-called Vaqueros of Eldridge, all of which are of upper Miocene 

age. As redefined the Modelo formation aggregates 9,000 feet in thickness. It 

is primarily clay, diatomaceous shale, and fine-grained laminated sandstone and 

cherty beds, and contains huge lenses of coarse brown and tan sandstone about 

4,000 feet in maximum thickness. It rests unconformably on the Topanga 

formation, and is unconformably overlain by the Pico formation, the basal 

division of the Fernando group.

Later work by Kew and other geologists proved that typical Modelo contains beds equivalent to Topanga formation (middle Miocene), but the 

United States Geological Survey follows Kew's 1924 definition, which 

restricted the name Modelo to upper Miocene beds, believing that that 

usage will be more useful, and that the Topanga may eventually be 

separated from the type Modelo.
50 GEOLOGIC UNITS OF CALIFOKNIA

Modln formation.

Lower Jurassic: Northern California (Redding quadrangle).

J. S. Diller, 1906 (U. S. Geol. Survey Geol. Atlas, Redding folio, No. 138). An 

extensive succession of tuffaceous beds, overlain by a greater mass of compact, 

fine gray shaly sandstones and sbales, with a few small lenses of limestone. 

At base an extensive bed of volcanic conglomerate, having a maximum thickness 

of about 400 feet in Bear Mountain. Estimated thickness of formation 3,000 

feet. Rests unconformably on Brock shale. " The relation of the Modin formation to the overlying Potem formation appears to be one of conformity, though 

the Modin epoch closed at a time of vigorous volcanic activity, especially in the 

vicinity of Bagley Mountain." [See Bagley andesite.] Named for exposures on 

Modin Creek, near the mouth of which, in the northeastern part of^he Redding 

quadrangle, the formation has yielded most of its fossils.

Mohave (approved spelling). See " Mojave."

Mohawk lake beds.

Miocene (upper): Northern California (Plumas County).

H. W. Turner, 1891 (Washington Philos. Soc. Bull. 11, pp. 385-410). Name applied

to lake beds of fine stratified material deposited in Mohawk Valley and vicinity,

in Plumas County, during Pliocene and Pleistocene time. Rest on Tertiary

igneous rocks (andesites and rhyolites) and are overlain by recent alluvium.

. According to J. P. Smith (California State Min. Bur. Bull. 72, p. 37, 1916) 

these beds are of upper Miocene age.

 "Mojave formation,"

Tertiary (probably Eocene) : Southern California (Mohave region).

J. Hervey Smith, 1900 (Jour. Geology, vol. 8, pp. 455-456). A formation in southeastern California described [but not named] by H. W. Fairbanks (Am. Geologist, 

vol. 17, p. 63 [also 67-68], 1896) as consisting of "a series of beds of clays, 

sandstone, volcanic tuffs, and interbedded lava flows, probably 1,000 feet or more 

in thickness," occurring " on the northern slope of the El Paso Range, between 

Mojave and Owen's Lake," and probably extending over a considerable area betweeu me El Paso Range and the Sierra Nevada. Finely exposed in Red Rock 

Canyon and about Black Mountain; tilted northward at an angle of 15°-20°. 

Fossil plants Identified by F. H. Knowlton as without doubt Tertiary and as 

probably Eocene.

Mono, shale.

Eocene: Southern California (southern part of Santa Ynez quadrangle, 

Santa Barbara County).

B. N. Nelson, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 10, 

pp. 350, 352, pi. 46, map). At type locality consists of a series of sandy gray 

shales, in beds up to 4 inches thick, interbedded with light-gray, medium finegrained micaceous sandstones varying in thickness from 1 to 4 inches. In lower 

; ; part some of the softer shales are locally contorted. Oval concretions occur 

locally. Toward top are impure limestone ledges 1 to 2 feet thick. .At base is a 

rather hard, massive coarse-grained sandstone about 50 feet thick. Total thickness of formation 700 feet. Rests conformably on Indian conglomerate and la 

conformably overlain by Sierra Blanca limestone. No fossils but believed to be 

of marine origin. Extends from Mono Creek to Santa Cruz Creek; also occurs 

on southeast side of Big Pine Mountain. Named for exposure in . canyon of 

Mono Creek, at mouth of Roble Creek, Santa Barbara County.

 "Montara granite."

Late Jurassic (?): Western California (San Francisco Peninsula and 

southward).

A. C. Lawson, 1895 (U. S. Geol. Survey Fifteenth Ann. Rept., p. 408; Am. Geologist, 

vol. 15, pp. 343-346). Montara granite, of undetermined age. Is intrusive into 

the crystalline limestone [Gabilan limestone] and constitutes the mass of Montara Mountain, San Francisco Peninsula.

-A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

[Mapped and described as quartz diorlte of pre-Franciscan age, the name " Montara granite" being discarded.]
GEOLOGIC UNITS OF CALIFORNIA 51

Monte de Oro formation.

Upper (?) Jurassic: Northern.California (Oroville, Butte County).

H. W. Turner, 1896 (U. S. Geol. Survey Seventeenth Ann. Rept., pt. 1, p. 648). 

Plant-bearing clay slate with some conglomerate. The slates are very similar 

to those of the Mariposa formation, from known areas of which they are, however, widely separated. Occur near Oroville, Just south of Monte de Oro, ButteCounty.

Local name for slate whose relations to Mariposa slate still remain undetermined.

Monterey group.

Miocene (middle and lower) : Western California.

W. P. Blake, 1856 (Acad. Nat. Scl. (Philadelphia) Proc., vol. 7, pp. 328-331). Monterey formation, consisting of " regular strata of light-colored, prevailingly whiteargillaceous and arenaceous material, the particles being very fine and firmly 

Impacted, so that in some places the strata break with smooth, curved surfaces 

and have a semlvitreous luster." Top 50 feet very rich in diatoms, and the 

underlying beds may be equally rich. Thickness undetermined. Typical section 

is about 2 miles southeast from center of town of Monterey, and it forms a 

portion of a hill 500 to 600 feet high, which fronts the bay and rises on the 

east side of the stage road to San Francisco. This hill is separated from the 

bay by a broad sandy plain and a belt of sand hills along the beach. Thedetailed section approximates 81 feet, exclusive of the basal member, which 

"extends down for a long distance." The formation Is unconformably overlain 

by a rudely stratified or assorted mass of boulders and gravel like the accumulation along a beach, and it "appears to be conformably underlain by Tertiary 

strata that underlie a part of the town of Monterey and extend to and beyond' 

the Mission of San Carlos." Is quarried near town of Monterey.

G. D. Louderback, 1913 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 7, pp. 

191-241), proposed Monterey series to Include all the Miocene deposits as wellas the underlying Sespe formation, chiefly if not wholly of OHgocene age.

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 198). 

The Monterey group is divided into (descending order) Briones sandstones, 2,300' 

feet, containing Hercules shale member near middle; Rodeo shale, 670 feet; 

Hambre sandstone, 1.200 feet; Tlce shale, 460 feet; Oursan sandstone, 600 feet; 

Claremont shale, 800 feet; and Sobrante sandstone, 400 feet. [The subsequent 

studies of B. L. Clark resulted In excluding the Briones sandstone from theMonterey group.]

The United States Geological Survey includes in the Monterey group theSalinas shale, Temblor formation, and the underlying Vaqueros sandstone, and it now excludes Briones sandstone.

Montgomery limestone.

Silurian (Niagaran) : Northern California (Taylorsville region).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Limestone of 

Niagara age, 10 to 60 feet thick. Older than Taylor[s]vllle slates and younger 

than Grizzly quartzlte.

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Light to dark bluish gray limestone with occasional knots or benches of black chert. The form of the limestone 

is lenticular, and the Jargest lentil, which is on the crest of the northern end of 

the Grizzly Mountains^ and is fossiliferous, has a thickness of 60 feet with a 

length of about 200 feet. Five of these limestone lentils have been found. One 

Is on the south bank of Montgomery Creek, where it forms prominent cliffs at an 

altitude of about 4,000 feet. Rests conformably on Grizzly formation. Believed 

to be unconformable with overlying Taylorsville formation.

Named for occurrence on Montgomery Creek, 2% miles south of Taylorsville, Plumas County.

Moraga formation.

Pliocene: Western California (San Francisco region).

A. C. Lawson, 1914 (D. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Chiefly flows of andesite and basalt, with which are associated some basic tuffsand beds of well-cemented rhyolite tuff. Between these volcanic rocks lie lenticu-
52 GEOLOGIC UNITS OF CALIFORNIA

lar beds of conglomerate, clay, and limestone. One of the limestone beds contains fresh-water fossils, is 30 feet thick, and has lavas above and below it. 

One of the conglomerate lenses in places reaches a thickness of about 200 feet. 

The first of the flows after an unusually long interval [between flows of the 

Moraga formation] was the andesite of Grizzly and Ruin Peaks. Maximum 

thickness of Moraga formation about 1,200 feet. Is basal formation of Berkeley 

group. Underlies Siesta formation and unconformably overlies Merced formation. Named for occurrence in Moraga Valley, Contra Costa County.

Morales member.

Miocene (upper) : Southern California (Cuyama Valley).

W. A. English, 1916 (U. S. Geol. Survey Bull. 621, pp. 191-215). Upper member of 

Santa Margarita formation. Consists of about 2,000 feet of clay, white sand, 

and gravel, with, at base, 300 to 400 feet of light-gray, poorly bedded soft clay 

shale containing a few thin beds of white limestone which on weathering break 

up into small irregular fragments. Rests uncouformably on Whiterock Bluff 

shale member of Santa Margarita, which in places it overlaps. Is uucouforinably 

overlain by Cuyama formation. Named for development in vicinity of Morales 

Canyon.

Moreno formation.

Upper Cretaceous: Southern California (Diablo Range).

R. Audersou and R. W. Pack, 1915 (U. S. Geol. Survey Bull. 603). Upper formation 

of Chico group. Rests conformably on the Panoche formation, the lower formation of the Chico group, and is uncouformably overlain by the Martinez (?) 

formation. Is lithologically divisible into two parts, a huge lens of concretionary 

sandstone and iuterbedded shale (the Cuutua sandstone member), which forma 

its lower and major part in a small area, and a body of foraminiferal and diatoinaceous chocolate-brown and maroon clay shale with minor amounts of 

sandstone and some calcareous layers and concretions, which constitutes the 

upper part of the formation but which also includes lower beds believed to be 

equivalent to the Cantua sandstone member where that is lacking. The maximum thickness of the Cantua sandstone is at least 4,500 feet. The thickness of 

the clayey member averages 450 feet, with a maximum of about 1,000 feet. 

Named for exposures in Moreno Gulch, on the east flank of the Panoche Hills, 

Fresno County.

Mormon sandstone.

Middle Jurassic: Northern California (Taylorsville region).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Fine-grained compact gray sandstone with several small bed| of conglomerate. Thickness 500 

feet. Older than Bicknell sandstone and younger than Thompson limestone.

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Prevailingly fine-grained gray 

compact sandstone, passing on the one hand into greenish or reddish conglomerate and on the other hand into more slialy beds. Thickness 550 feet. Rests 

conformably on Thompson limestone and is overlain, probably conformably, by 

the Bickuell sandstone. Extends across Mount Jura from the lower slopes of 

Grizzly Mountains to North Arm.

Named for exposures at Mormon station, on old stage route near Taylorsville, Plmnas County.

"Morrison sandstone." Q

Middle Jurassic: Northern California (Trinity and Shasta Counties). 

0. H. Hershey, 1904 (Am. Geologist, vol. 33, pp. 356-360). [Morrison sandstone as 

used on pages above cited is, according to J. S. Diller (unpublished note), a misprint for Mormon sandstone.]

Mountain Girl congloinerate-quartzite.

Lower Paleozoic (?) : Southeastern California (Inyo County). 

See under Telescope group. Derivation of name not stated.

Mount Clark granite.

Probably Cretaceous: Yosemite National Park. .

F. C. Calkins, 1930 (U. S. Geol. Survey Prof. Paper 160, p. 128, map). Very 

siliceous light-colored granite or alaskite. composed almost wholly of feldspar
CORRECTION 

Moreno formation.

Upper Cretaceous: Southern California (Diablo Range).

R. Anderson and R. W. Pack, 1915 (U. S. Geol. Survey Bull. 603). Upper formation 

of Chlco group. Rests conformably on Panoche formation, the lower formation 

of Chico group, and is unconformably overlain by Cantua sandstone member of 

Martinez (?) formation. In the southern area it consists of foraminiferal and 

diatomaceous maroon and chocolate-colored shale and dark clay shale, -with 

some interbedded sandstone, and has a maximum thickness of about 1,600 to 

1,800 feet. In the northern area it contains less of the shale of truly organic 

origin and more clay shale and sandstone and is unconformably overlain by 

Tejon formation. Typically exposed in Moreno Gulch, on east flank of Panoche 

Hills, where it is 1,700 to 2,000 feet thick and composed predominantly of 

thin-bedded, rather brittle brownish and lavender-colored shales that weather 

into small bits and flakes. In lower part of formation are numerous beds of 

sandstone, locally containing poorly developed concretions and in general similar 

to the sandstone of Panoche formation. The upper half of formation is more 

nearly pure shale and contains a greater proportion of material of organic 

origin. Calcareous shale, limestone nodules, and layers of semiporcelaneous 

siliceous shale occur locally, and near top of formation is a zone of white platy 

diatomaceous shale about 200 feet thick, which is traceable most of way 

along face of Panoche Hills, Fresno County. Line between Moreno and Panoche 

formations is arbitrarily drawn at horizon where the sandstone beds that form 

the steep eastern slope of Panoche Hills dip beneath the predominantly shaly 

beds.

[To face p. 52, U. S. Geological Survey Bulletin 826] 

75593 31
GEOLOGIC UNITS OP CALIFORNIA. 53

and quartz. Moderately coarse grained and even textured. Is practically devoid 

of t'erromagnesian minerals, such as biotite and hornblende.

Named from fact that it composes Mount Clark, Yosemite National Park.

Mount Lowe granodiorite.

Age (?) : Southern California (San Gabriel Mountains, Los Angeles County).

W. J. Miller, 1926 (Geol. Soc. America Bull., vol. 37, p. 149, abstract). White to 

light-gray massive to moderately foliated granodiorite, which may be called 

Mount Lowe granodiorite, because of its typical occurrence on Mount Lowe and 

vicinity. Younger than Mount Wilson quartz diorite.

Mount Wilson quartz diorite.

Age (?) : Southern California (San Gabriel Mountains, Los Angeles County).

W. J. Miller, 1926 (Geol. Soc. America Bull., vol. 37, p. 149, abstract). The most 

typical and extensively developed of the diorites of the San Gabriel Mountains 

may be called the Mount Wilson quarts diorite, because of fine exposures on and 

near Mount Wilson. A hornblende-rich diorite, occurring in smaller masses, may 

be older than the Mount Wilson diorite or it may be only a fades of it. A 

pinkish-gray, more or less foliated granite, which occupies a considerable area, 

is younger than the diorite. The diorite is older than Mount Lowe granodiorite.

Mud Hill series.

Miocene to Pleistocene (?) : Southern California (Riverside County). 

E. E. Free, 1914 (Carnegie Inst. Washington Pub. 193, pp. 22-23). Consists of an 

upper member of very variable sandstones and clays, mostly thinly bedded and 

showing many probable unconformities; underlain by a thick member of coarse 

arkose sandstone, usually of reddish color and quite uniform texture; at base a 

basal conglomerate, resting normally upon an eroded surface of schists and 

grunitrs such as make up the core of the range. Thickness 3,000 feet. No 

fossils at type locality at Mecca, 'but in Carri/o Creek Valley Blake found 

Miocene fossils in lower beds. Very probably includes beds of all ages from 

Carrizo Creek Miocene into early Pleistocene. Named for occurrence in Mecca 

Mud Hills, Mecca, Riverside County.

'Neocene.

A term that has had considerable usage in geologic literature to include the 

Pliocene and Miocene series.

Nerola formation.

Miocene: Central western .California (Mount Diablo region).

B. L. Clark and A. 0. Woodford, 1927 (California Univ. Pub., Dept. Geol. Scl'. 

Bull., vol. 17, p. 69). " Unconformably on the San Lorenzo deposits is the San 

1'ablo group, divided into two formations, the Cierbo and the Nerola. Unconformably on the San Pablo is n series of tuffs and sandstones; the'tuffs have 

generally been referred to the Pinole tuff, the sandstones to the Orinda 

formation."

Nordheinier formation.

Carboniferous (?) : Northwestern California (Klamath Mountains).

O. H. Hershey, 1906 (Am. Jour. Sci., 4th ser., vol. 21, pp. 58-06). Black slaty shale 

with maximum estimated thickness of 3,000 feet. At base a slight development 

of coarse' sandstone, apparently made up of debris from the underlying quartzbearing rhyolite. This sandstone is nowhere more than 50 feet thick but can be 

traced for several miles. No evidence of nonconformity between the sandstone 

and the rhyolite. No other sandstones and no conglomerate or limestone, but 

contains a few thin layers of chert. Is badly shattered by intrusive rocks. No 

fossils. May be late Devonian but is more likely Carboniferous. Some characters suggest Baird formation. It might also be a western representative of the 

Trlasslc Pit shales, but is not likely to be any younger. The valley of Nordheimer Creek is cut in the formation.

Northbrae rhyolite.

Pliocene: Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Numerous isolated patches of a white rhyolite lava, apparently the remnants of
54 GEOLOGIC UNITS OF CALIFOBNIA

a flow, the greater part of which has been removed by erosion. Thickness probably nowhere exceeds 100 feet. Occurs on western slope of Berkeley Hills north 

of Berkeley. Rests on worn surface of Franciscan and Cretaceous formations. 

Overlain by Campus and Orinda formations. Named for occurrence in Northbrae 

district, near Berkeley.

Nosohi formation.

Pennsylvania!!: Northern California (Redding quadrangle).

J. S. Diller, 1906 (U. S. Geol. Survey Geol. Atlas, Redding folio, No. 138). Largely 

andesite or basalt tuffs and tuffaceous conglomerate and a few flows of lava,, 

locally interstratifled with shales and sandstones, in part calcareous and often 

rich in fossils. Thickness 500 to 1,200 feet. Top formation of the PennsyIranian. 

Conformably overlies McCloud limestone and underlies Dekkas andesite. Includes 

the " McCloud shales " of Smith and Fairbanks, as well as the pyroclastic rocks 

with which these shales are so intimately associated. Named for exposures on 

Nosoni Creek.

Oakland conglomerate member.

Upper Cretaceous: Western California (San Francisco region).

R. Arnold, 1902 (Science, new ser., vol. 15, table on p. 416). Oakland, 500 feet 

(conglomerate). [Shown as underlying Chico and as younger than KnoxvilleJ

A. C. Lawson, 1903 (Geol. Soc. America Bull., vol. 13, table on pp. 544-545). [Sameas above.]

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Oakland conglomerate member of Chico formation. Conglomerate, 100 to 1,000> 

feet thick, forming the basal member of the Chico formation in the Berkeley 

Hills. At many places the conglomerate shows distinct stratification but exhibits 

none of the subordinate plication observed in the underlying shale of the Knoxville formation, upon which it rests conformably. Named for type exposure at 

the city of Oakland.

Oakridge sandstone.

Jurassic (?) : Western California (Alameda County).

C. F. Tolman, jr., 1915 (Nature and science on Pacific coast, p. 45, San Francisco, 

Elder & Co.). Oakridge sandstone, upper member of Franciscan series at Corral 

Hollow [near Livermore, Alameda County] ; slightly metamorphosed. Younger 

than Corral Hollow shales.

" Ocoya Creek beds."

Miocene (lower) : Southern California (Kern County).

H. W. Turner, 1894 (Am. Geologist, vol. 13, p. 239). Ocoya Creek beds, of Miocene 

age, occur on Ocoya or Pos6 Creek and farther south.

In Pacific Railroad Reports (vol. 5, pp. 164-173, 1856) W. P. Blake described 

the Miocene beds along Ocoya Creek, but did not name them. These 

beds were for a time included in the Vaqueros sandstone, but according 

to J. P. Smith (Jour. Geology, vol. 18, No. 3, 1910) they carry the Turntella ocoyana fauna and are therefore younger than the Vaqueros 

sandstone as now restricted to the beds characterized by the Turritella 

inezana fauna. The name Temblor formation is now generally applied 

to the beds carrying the Turritella ocoyana fauna in this region.

Orinda formation.

Pliocene: Western California (San Francisco region).

A. C. Lawson and C. Palache, 1902 (California Univ. Pub., Dept. Geology Bull., 

vol. 2, p. 371, map). Orindan formation. Fresh-water conglomerates, sandstones, shales, clays, limestones, and tuffs, with pebble conglomerate at base. 

Thickness 800 to more than 2,400 feet. Basal formation of Berkeleyan series. 

Rests on Monterey series and is overlain by rhyolite tuff that forms the basal 

division of the Upper Berkeleyan.

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Orinda formation. Fresh-water conglomerates, sandstone, clay shales, limestones, some thin seams of lignite, and at a few horizons thin layers of brown, 

decomposed volcanic tuff. Farther east, in Mount Diablo quadrangle, it in-
GEOLOGIC UNITS OF CALIFORNIA 55

eludes, in lower part, a few beds of pumiceous tuff similar to Pinole tuff. 

Thickness 2,000 to 2,500 feet in San Fablo Ridge, but 6,000 feet to the southeast, near southern border of Concord quadrangle. Lies conformably on Pinole 

tuff, or, where that is absent, rests on San Pablo or older formations. Excluded from Berkeley group. Is overlain by Moraga formation, which is now 

treated as the basal division of the Berkeley group. Named for exposures at 

Orlnda, Contra Costa County.

" Orindan " formation. See Orinda formation.

 Oro Grande series.

Lower Cambrian: Southern California (San Bernardino County).

0. H. Hershey, 1902 (Am. Geologist, vol. 29, pp. 273-290). Nearly pure limestone 

underlain by pure quartzite. The alteration of the Oro Grande series has destroyed all fossils, and its age can only be conjectured. Except for higher 

degree of metamorphism it is identical in character with the Lower Cambrian 

series described by Walcott from Inyo County, and I believe the propriety of 

classing it as Lower Cambrian will hardly be questioned.

Osos basalt.

Jurassic (?): Western California (San Luis Obispo region).

H. W. Fairbanks, 1904 (U. S. Geol. Survey Geol. Atlas, San Luis folio, No. 101). 

Dark fine-grained, generally amygdaloidal basalt, which occurs in several areas 

and from its relation to San Luis formation [Franciscan] does not appear to be 

intrusive but to have cooled as surface flows. Other basalts occur in the area. 

Named for outcrops in Los Osos Valley, San Luis Obispo County.

tOursan sandstone.

Miocene (middle): Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Rather fine-grained sandstone, 600 feet thick. A formation of the Monterey 

group. Underlies Tice shale and overlies Claremont shale. Named for exposures 

on Oursan Ridge, Concord quadrangle, Contra Costa County.

 Oweiiyo limestone.

Permian: Eastern California (Inyo Range).

IB. Kirk, 1918 (U. S. Geol. Survey Prof. Paper 110). Mainly massive grayish crystalline to compact limestones. Basal 2 feet is blue-gray compact limestone carryIng irregular lenses and stringers of sandstone whose grains were apparently 

 derived from the underlying Reward conglomerate. Here and there, particularly in the upper third, are layers carrying rounded chert pebbles. Thickness 

126 feet. The limestones carry a Permian (Sptrlferina pulchra) fauna throughout and according to G. H. Girty are probably to be correlated in part with 

the Park City, Phosphoria, and Embar formations of Utah, Idaho, and Wyoming. 

Only two exposures of the Owenyo limestone are known, both of which lie 

between the Reward mine and Union Wash. One shows the base and the other 

the top of the formation. It is unconformably overlain by Lower Triassic 

shales and unconformably underlain by Reward conglomerate. Named for exposures about 3% miles north of Owenyo station on Southern Pacific, between 

Union Wash (the first large canyon to the north) and the Reward mine.

41 Ozarkian."

Pliocene and Quaternary: Time term.

0. H. Hershey, 1896 (Science, new ser., vol. 3, pp. 620-622). A marked period of 

elevation and subaerial erosion instituted by the great post-Tertiary epelrogenic 

uplift of North America and terminated by the Kansan epoch of widely extended 

glaciation. Preceded by the Lafayette epoch of deposition. Assigned to the 

Pleistocene.

See Sierran.

Paicines formation.

Pliocene: Southern California (San Benito County).

P. F. Kerr and H. G. Schenck, 1925 (Geol. Soc. America Bull., vol. 36, pp. 470, 476, 

map). "Continental Pliocene herein given the local formational name 

' Paicines ' pending more exact correlation." Yellow, loosely consolidated sand-
56 GEOLOGIC UNITS OF CALIFOBNIA

stone interbedded with shale; soft gray sandstone colored by fragments of 

Franciscan metamorphics; occasional peat seams. Fresh-water fossils. " The 

age of the Paicines is in all probability Pliocene." [Is classified as Pliocene.] 

It lies unconformably on Etchegoin formation and is overlain, .probably unconformably, by San Bcnito gravels. [Apparently named for extensive development 

west of Paicines, Benito County.]

Pala conglomerate.

Pleistocene: Southern California (San Diego County).

A. J. Ellis, 1919 (U. S. Geol. Survey Water-Supply Paper 446). Coarse valleyfill conglomerate of a type not common in this area. It is a conglomeratic mass, 

of boulders and residuum, having a thickness of about 200 feet above and extending to an undetermined depth below the present level of the river. Is 

older than the valley fill which underlies the present valley floors and may be 

as old or even older than the San Pedro formation. Occurs in the valley of the 

San Luis Key, in the vicinity of Pala, San Diego County.

Palm Spring formation.

Miocene (middle or upper) : Southeastern California (Imperial County).

W. P. Woodring, 1931 (Carnegie, Inst. Washington Pub. 418, p. 10). Palm Spring 

formation. Unconsolidated or poorly consolidated nonmarine sands and light 

chocolate-brown and faint brick-red silts 1,000 ± feet thick. Of middle or upper 

Miocene age. Conformably overlie the marine Imperial formation in Carrizo 

Mountain and vicinity, Iihperial County. Named for a spring on lower part of 

Vallecito Creek, a southeastward-flowing tributary entering Carrizo Creek about 1 

mile above the old stage station.

Palos Verdes sand.

Pleistocene: Southern California (Los Angeles County).

A. J. Tieje, 1926 (Am. Assoc. Petroleum Geologists Bull., vol. 10, No. 5, pp. 505-512). 

Massive gray-green, very coarse to gravelly quartzose and loosely cemented marine sands, of several varieties, containing pebbles up to one-half inch in diameter. Thickness 50 feet. "Sand dollars (Echinarachnius eteoentriou-8 Esch.?) 

amazingly abundant, and the pelecypods and gastropods are typically Palos 

Verdes, with some 70 species thus far identified." Rest on 104 feet of unfossiliferous sands of beach type and are overlain by 150 feet of unfossiliferous 

sands assumed to be of fresh-water origin. Assigned to the Pleistocene. 

Younger than San Pedro sands.

Composes a part of the San Pedro formation of previous reports, but in 

report cited above the San Pedro is restricted to a part only of the 

formation as heretofore defined.

Panoche formation.

Upper Cretaceous: Southern California (Diablo Range):

R. Anderson and R. W. Pack, 1915 (U. S. Geol. Survey Bull. 603). Lower formation of Chico group. Rests unconformably on Franciscan formation and is conformably overlain by Moreno formation, the upper formation of the Chico group. 

.The Panoche consists of alternating beds of dark thin-bedded clay shale and 

massive gray concretionary sandstone aggregating 9,500 to over 20,000 feet in 

thickness. The formation also includes some arenaceous shale, platy sandstone, 

and beds of coarse conglomerate, which locally attain great thicknesses. The 

lowest beds here included in the Panoche formation are nonfossiliferous and 

may represent the Knoxville formation, which, however, is believed to be absent. 

Named for development in the Panoche Hills, Fresno County.

Pasadena formation.

Miocene: Southern California (San Gabriel Mountains)

R. Arnold and A. M. Strong, 1905 (Geol. Soc. America Bull., vol. 16, p. 188). A 

conformable series of conglomerates, sandstones, and shales of either lower or 

middle Miocene age. Flanks the San Rafael Hills on the south and underlies 

the southern portion of the city of Pasadena. The conglomerates of this formation rest on and are composed of the San Gabriel plutonic and metamorphic 

rocks.
GEOLOGIC UNITS OF CALIFORNIA 57

"Paskenta horizon."

Lower Cretaceous: Northern California (Tehama County).

F. M. Anderson, 1902 (California Acnd. Sci. Proc., 3d ser., vol. 2, pp. 43-47). Paskenta horizon is here applied to upper 4,000 feet of the 20,000 feet of strata 

composing the Knoxville formation, which is especially well represented in the 

vicinity of Paskenta, Tehama County, and which lies conformably on the rest 

of the Knoxville.

Paso Bobles formation.

Pliocene and lower Pleistocene (V) : Western California (San Luis Obispo 

County and neighboring areas).

II. W. Fairbanks, 1898 (Jour. Geology, vol. 6, pp. 565-566). Fresh-water conglomerates and sandy and marly clays, usually slightly consolidated. Overlap unconformably upon the upturned and sharply folded San Pablo formation. Fill the 

Salinas Valley as far up as Atascadero. Are characteristically exposed about 

town of Paso Robles [San Luis Obispo County], from where they extend westward toward Santa Lucia Mountains and for many miles north and east of that 

place, filling the valley of the Estrella and its tributaries, and may reach into 

the Great Valley. Are of later Neocene age.

Pato red member.

Miocene (lOAA'er) : Southern California (Cuyaina Valley).

W. A. English, 1916 (U. S. Geol. Survey Bull. 621, pp. 191-215). Gray and red 

clay shale and sandstone, 1,300 feet thick, forming the basal member of the 

Vaqueros formation. The upper 500 feet of beds are of a brilliant crimson color 

and are. composed of material eroded from the adjacent land at the time the 

red beds were being deposited. Conformably below these bright-red beds is 

about 800 feet of gray and red clay, which forms the lower part of the member. 

The Pato member is overlain, in places unconformably, by massive white sandstone of the Vaqueros. It rests with marked unconformity on pre-Monterey 

shale. Named for exposures in Pato Canyon, Cuyama Valley.

According to W. S. W. Kew (California Univ. Pub., Dept. Geology Bull., vol. 

12, pp. 1-21, 1919) the Pato red member is older than true Vaqueros 

and corresponds to the Sespe formation, of OHgocene and lower Miocene 

(?) age. ^

Peale formation.

Mississippian: Northern California (Taylol'sville region).

J. S. DHler, 1908 (U. S. Geol. Survey Bull. 353). Of variable character. Reddish 

to brown slaty shale, sometimes gray or greenish, passing into tuffaceous sandstone and fine conglomerate, is most common. The fine conglomerate contains 

much volcanic material, with occasional red lapilli and small lenses of calcareous matter. Thin beds of gray quartzite also occur, and masses of black^ 

gray, or red chert form prominent ledges. The tuffaceous beds are well exposed 

and fossiliferous on the horse trail from Wards Creek to Peale diggings, also 

beyond Hosselkus and to within about a mile of Lucky S road. The chert is 

best exposed near the forks of the road just east of Hosselkus, where there is 

a prominent ledge of red banded chert full of quartz veins, but no considerable . 

amount of hematite with it as on Houghs Peak. Red siliceous slate and chert 

occur near the summit along the trail from Wards Creek to Peale diggings, as 

well as in the divide at the head of Hinchman Ravine. [Fossils listed.] The 

formation is almost completely surrounded by igneous rocks, meta-andesites, and 

is in part made up of pyroclastic material of the same sort. It evidently represents an epoch of volcanic activity, although the immediately enveloping rock 

may be in large part intrusive. Thickness 1,400 feet. Is overlain by Reeve 

meta-amlesite. Is older than Robinson formation and younger than Shoofly 

formation.

Pedroian.

A time term used by J. E. Eaton (Am. Assoc. Petroleum Geologists Bull., 

vol. 12, p. 138, 1928) to cover the San Peclro formation as restricted by 

him (to the basal part of the original San Peclro) and his overlying Hall 

Canyon formation, or to all of the lower Pleistocene.
58 GEOLOGIC UNITS OF CALIFORNIA

Pelona schist series. . Pre-Cambrian(?) : Southern California (Los Angeles County).

O. H. Hershey, April, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 3, pi. 1, 

map). [Pelona scMsts on legend of map lie between gneiss below and Archean 

gneiss above.]

0. H. Hershey, 1902 (Am. Geologist, vol. 29, pp. 273-290). Pelona schist aeries. 

3,000 feet of dark-colored and more schistose mica schist underlain by 2,000 

feet of light-yellowish coarse, angular mica schist. Assigned to pre-Cambrian(?). 

Named for Sierra Pelona, Los Angeles County. :

,0. H. Hershey, 1912 (Am. Jour. Sci., 4th ser., vol. 34, pp. 271-273). Another area 

of the Pelona series constitutes the greater part of the Rand Mountains near 

Randsburg, Kern County. This series is the youngest important Archean series. 

" I propose to extend the name over the Abrams and Salmon formations of the 

Klamath region."

 ^ Pescadero series."

.Upper Cretaceous, Eocene, Miocene: Western California (Santa Cruz Mountains region).

,G. H. Ashley, 1895 (Jour. Geology, vol. 3, pp. 435-439). A great series of sandstones, shales, and conglomerates having considerable prominence in the Santa 

Cruz Mountains. They consist in part of the San Francisco sandstone of previous writers. The section near Pescadero gives a questionable thickness of 

over 10,000 feet. The rocka have been greatly disturbed and faulted. "Their 

age has been shown to be in part Miocene and is thought to extend down 

through the Eocene and possibly into the Cretaceous." Unconformably underlies Monterey series and rests, probably unconformably, on pre-Cretaceous metamorphic sandstone.

Named for exposures at Pescadero Point and near Pescadero, San Mateo 

County.

iPetaluma formation.

Miocene (upper) : Northern California (north of San Francisco Bay 

region).

R. B. Dickerson, 1922 (California Acad. Sci. Proc., 4th ser., vol. 11, No. 19, with 

maps). Chiefly lacustrine deposits of clays, clay shale, arid sandstone. Is char- 

;=> acterized by great abundance of clays, but only in certain stream canyons is 

there opportunity to observe them. It is a fresh-water and brackish-water phase 

of marine San Pablo formation and is confined to northeast corner of Petaluma 

quadrangle and southeast corner of Santa Rosa quadrangle. Is unconformably 

overlain by Merced group or its correlative the Sonoma group. Is probably 

underlain by Monterey group at many localities.

Named, apparently, for exposures in vicinity of Petaluma, Sonoma County.

JWco formation.

Pliocene: Southern California (Los Angeles and Ventura Counties).

B. L. Clark, 1921 (Jour. Geology, vol. 29, pp. 608-609, chart opp. p. 586). Over 

a fairly large area in the Los Angeles region there is a marked difference in 

dip and strike between the lower and middle Fernando, now referred to the 

Pico formation by the United States Geological Survey, and what has previously 

been referred to as the upper Fernando. (Footnote: A paper by Dr. W. S. W. 

Kew, of the United States Geological Survey, is now in press in which the 

Fernando is considered a group composed of the Pico and Saugus formations 

separated by an unconformity.) The beds of this upper horizon contain a very 

large percentage of recent species. The Geological Survey proposes to use the 

name Saugus forma'tion for the upper Fernando section, which is herein referred 

to as the Saugus group.

W. S. W. Kew, 1923 (Am. Assoc. Petroleum Geologists Bull., vol. 7, pp. 411-420). 

The author's name Pico formation, for the lower [formation of the Fernando 

group, first appeared in print in 1921, in a brief paper by B. L. Clark on the 

Los Angeles region. The formation is well exposed in Pico Canyon, Los 

Angeles County, from which it is named. It is also well exposed in Santa
GEOLOGIC UNITS OF CALIFORNIA 59

Clara Valley and in San Fernando Valley, where it rests unconformably upon 

the Modelo formation and lies unconformably below the Saugus formation. 

It is entirely of marine origin and contains a fauna belonging to the base of 

the Pliocene.

W. S. W. Kew, 1924 (U. S. Geol. Survey Bull. 753). The Pico formation, the lower 

formation of the Fernando group, consists of fine-grained'gray sandstone, interbedded with coarse sandstone and conglomerate, and is about 4,000 fedt thick. 

Along the south side of Fernando Valley and westward to Las Virgenes Canyon 

It consists of laminated gray sandy clay and fine-grained sandstone with zones 

or lenses of white diatomaceous soft shale; the upper strata largely mediumgrained soft sandstone with some conglomerate.

J. B. Eaton, 1926 (Oil and Gas Jour., Nov. 11, 1926, p. 72; Oil Age, November, 1926, 

p. 16). Santa Paula formation, 10,000 feet thick, previously unrecognized, 

underlies Pico formation and unconformably overlies Modelo formation. [See 

under Santa Paula formation.]

Pie Knob andesite.

Pleistocene: Western California (San Francisco region).

A. C. Lawson and C. Palache, 1902 (California Univ. Pub., Dept. Geology Bull., 

vol. 2, pp. 403-404, map). Andesite, 180 feet thick on Pie Knob, occurring 

in the lower part of the Campan series, about 250 feet above its base. Forms 

a large part of Pie Knob, north of the university campus, Berkeley.

Pilarcitos sandstone.

Jura?sic( ?) : Western California (San Francisco region).

R. Arnold, 1902 (Science, new ser., vol. 15, table on p. 416). Pilnrcitos sandstone, 

790 feet thick. A formation of the Franciscan. [Shown in table as underlying 

volcanics that are older than Calera limestone.]

A. C. Lawson, 1903 (Geol. Soc. America Bull., vol. 13, pp. 544-545). (Same as 

above.]

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

[Maps the Franciscan rocks along Pilarcitos Creek and Pilarcitos Lake, both In 

San Mateo County, as Cabil sandstone, of which the Caloru limestone is a 

member.!

Pinecate formation.

Oligocene: Southern California (San Benito County).

P. F. Kerr and H. G. Schenck, 1925 (Geol. Soc. America Bull., vol. 36, pp. 470, 

472, map). Chiefly massive yellowish pebbly sandstone with Interbeclded conglomerate. Cross-bedding common. Thickness about 1,000 feet. Fossils rare 

but when found indicate marine origin. Lies on San Juan Bautista formation 

with probable disconformity. Underlies Vaqueros formation, probably unconformably. Is upper formation of San Lorenzo series. Typically exposed at 

Pinecate Peak, 4 miles northwest of San Juan, and also near the S;m .Tnan 

Cement Works.

Pinoche formation. Misprint for Panoche formation.

Pinole tuff.

Pliocene: Western California (San Francisco region).

R. Arnold, March, 1902 (Science, new ser., vol. 15, table on p. 416). Pinole, 1,000 

feet (pumiceous, fossiliferous tuffs). [Shown as underlying Orindan form:ition 

and overlying San Pablo formation.]

A. C. Lawson, 1903 (Geol. Soc. America Bull., vol. 13,- table on pp. 544-545). 

Pinole tuffs, 1,000 feet (fossiliferous, pumiceous). [Shown as underlying Orindan formation and overlying San Pablo formation.]

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

The Pinole tuff in most of its deposits is distinctly stratified. It consists 

almost wholly of whitish or light-yellowish pumice, partly in fragments ranging from 1 to 50 millimeters and partly in fine dust. It occurs only in small 

exposures in the Concord and San Francisco quadrangles but is more extensively 

exposed in the Coast Ranges farther north. Stratigrapbically it lies chiefly 

between the San Pablo formation below and the Orinda formation above, but 

It is in part Interbedded with the basal sediments of the Orinda, with which it

17462 31 5
60 GEOLOGIC UNITS OF CALIFORNIA

is more closely associated than with the marine San Pablo. On the shores of 

San Pablo Bay it contains fresh-water fossils and bones of terrestrial mammals. 

Thickness 0 to 1,000 feet. Rests, with probable unconformity, on San Pablo. 

formation. Named for exposures near Pinole, on San Pablo Bay.

Pipes fanglomerate.

Upper Pliocene or lower Quaternary (mapped as Pliocene) : Southern California (San Bernardino Mountains).

F. E. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 9,. 

pp. 344, 379-380, map). A flat-lying sedimentary deposit. Lower 15 feet, soft 

gray sandstone containing many rounded pebbles. This grades upward into 

reddish conglomerate, for most part of rounded granite, aplite, and quartz, 

pebbles up to 6 inches in diameter, but containing considerable angular material. 

Larger part of mass on hill half a mile southeast of The Pipes is "rather'well 

cemented and more resistant to weathering than the underlying granite, so that 

it forms a distinct bench near top of the ridge. Total thickness on this hill 

is 50 feet. Total thickness at table-topped hill directly east of The Pipes, 

is 60 feet on south side, but less than 20 feet on north side. Is overlain by 

basalt. Is younger than Hathaway formation.

Named for The Pipes, a watering place in San Bernardino County, near 

which it occurs.

Pismo formation.

Miocene (upper) : Southern California (San Luis Obispo region).

H. W. Fairbanks, 1904 (U. S. Geol. Survey Geol. Atlas, San Luis folio, No. 101).. 

Siliceous shale, diatomaceous earth, and thick beds of soft sandstone, with a 

member of sandstone and conglomerate at the base. Thickness about 3,000 feet. 

Occurs in southern part of area mapped and is considered to be contemporaneous with Santa Margarita formation of the northern part of tbe area, 

though the two formations are not known to have been connected. Unconformably overlain by Paso Robles formation and unconformably underlain by 

Monterey shale.

Named for exposures at Pismo, San Luis Obispo County.

Pit shale.

Middle and Upper Triassic: Northern California (Shasta County).

H. W. Fairbanks, July, 1894 (Am. Geologist, vol. 14, p. 28). Pitt shales-. Siliceous^ 

slates, of which nearly 2,000 feet are exposed at Silverthorne's ferry [on Pit 

River (approved spelling)], containing fossils regarded by J. P. Smith as Middle 

and possibly Lower Triassic. " It is intended to apply the term Pitt Bhales to. 

these rocks, which, together with some Upper Carboniferous strata (McCloud. 

shales), 20 miles above the fisheries, shall be embraced under the designation 

Pitt formation."

J. P. Smith, October, 1894 (Jour. Geology, vol. 2, pp. 592, 601-604). The Pitt 

formation (H. W. Fairbanks MS.) overlies conformably the McCloud limestoneand consists of about 3,000 feet of siliceous and calcareous shales, conglomerates, and tuffs. The rocks in, most places are highly metamorphosed, very 

poor in fossils, and folded to such a degree that the stratigraphy is obscure. 

The formation is largely developed in the region near the junction of Pitt and, 

McCloud Rivers. It contains both Carboniferous and Triassic rocks, in an 

apparently conformable series. Divided into Pitt shales, 2,000 feet thick, of 

Middle and Upper Triassic age, and McCloud shales, 1,000 feet thick, of UpperCarboniferous age. Underlies Swearinger slates. The Pitt shales consist of 

siliceous shales and conglomerates containing Triassic fossils about 1,500 feet 

below their top, underlain by several hundred feet of shales and conglomerates, 

without fossils.

J. S. Diller, 1906 (U. S. Geol. Survey Geol. Atlas, Redding folio, No. 138). Pit sliale. 

Largely dark and gray shales, thin-bedded sandstones, and many layers of tuffs. 

Thickness probably more than 2,000 feet. Conformably underlies Hosselkus limestone and rests upon the volcanic rocks called Bully Hill rhyolite and Dekkas> 

andesite, the latter being in part interbedded with lower beds of the Pit shale-.. 

Foaaila indicate Upper and Middle.Triassic age.
GEOLOGIC UNITS OF CALIFORNIA 61

" Pit formation." 

" Pitt formation."

Pennsylvanian to Upper Triassic: Northern California (Shasta County). 

See definition under Pit shale. The United States Geological Survey does 

not use the broad definition of the name Pit, which included the Pit 

shale and Nosoni formation ("McCloud shales") of present terminology.

Pitt series.

G. H. Ashley, 1923 (Eng. and Min. Jour.-Press, vol. 115, pp. 1106-1108), 

proposed Pitt series as a geographic name for the Middle Triassic series.

" Pleito formation."

Oligoceue: Southern California (Kern County).

C. M. Wagner and K. H. Schilling, 1923 (California Univ. Pub., Dcpt. Geol. Sci. 

Bull., vol. 14, pp. 235-252). Upper formation of San Lorenzo group in San 

Einigdio region. Discouformably overlies San Emigdio formation, the lower 

formation of the San Lorenzo group, and is unconformably overlain by Monterey 

group. At Caraera Pass, east of Pleito Creek, it consists of 350 feet of brownish 

and pearl-gray fine sandstones, the lower portion medium grained and white; 

underlain by 600 feet of massive dark-brown and buff sandstones with fossiliferous layers and light bluish-gray massive conglomerates toward base; 

the basal 50 feet consists of dark brick-red coarse sandstones and conglomerates, grading into gray toward west. Exposed on Pleito Creek, Kern 

County. The Pleito and San Emigdio are littoral deposits but faunally distinct, 

the faunas being more closely related to each other than either one is to the 

faunas of overlying and underlying formations.

Is a fauna! zone in San Loreuzo formation.

Plumas series.

Jurassic (Upper, Middle, and Lower) : Northern California.

J. P. Smith, 1910 (Jour. Geology, vol. 18, table opp. p. 217). Phimas series, includes 

Hinchman sandstone of Plumas County, Mormon sandstone, and Hardgrave sandstone, the Arietites beds of Inyo County, Calif., and Nevada being considered 

equivalent to the lower part of the Hardgrave sandstone.

Pogonip limestone.

Lower Ordoviciau : Northern Nevada.

Clarence King, 1876 (U. S. Expl. 40th Par. Atlas, map 4) and 1S78 (U. S. Expl. 40th 

Par Rept., vol. 1, pp. 187-195, 248). Pogonip limestone. Dark-colored limestone, 4,000 feet thick, conformably underlying Devonian Ogden quartzitc and 

conformably overlying Cambrian quartzites. The lower limestone beds are highly 

siliceous, of steely black color, with blue shales, and vary in physical characteristics, passing downward into rather argillaceous shales. Higher in formation 

it develops a dark-blue color and is much banded by zones of arenaceous limestone and occasional seams of pure chert several inches thick. Type locality 

Pogonip Ridge at White Pine (Hamilton), Nev.

In 1883 (U. S. Geol. Survey Third Ann. Kept., pp. 253-263, map) Arnold 

Hague, in his report on the Eureka district, defined the Pogonip limestone as comprising 2,700 feet of highly fossiliferous limestones, the 

upper part consisting of purer fine-grained limestone of bluish-gray color 

and distinctly bedded, and the lower part consisting of interstratified 

limestones, argillites, and, at base, arenaceous beds; the formation being 

overlain by the Eureka quartzite and underlain by the Hamburg shale 

(later named Dunderberg shale). This is the commonly accepted definition of Pogonip limestone. As thus defined the main mass of the formation has been classified as of Beekmantown age, but at top it carries a 

Chazy fauna. In 1923 (Smithsoniari Misc. Coll., vol. 67, No. 8, pp. 466- 

467, 475), however, C. D. Walcott proposed restricting the name Pogonip to the upper part of the Pogonip limestone of previous usage, and 

applied the name Goodwin formation to the lower 1,500 feet, which he
62 GEOLOGIC UNITS OF CALIFORNIA

stated contains a " Lower Ozarkian " fauna. The formation has been 

mapped by S. H. Ball (U. S. Geol. Survey Bull. 308, 1907) in Inyo 

County, Calif. The U. S. Geological Survey uses Pogonip limestone in 

the broad sense.

Pohono granodiorite.

Probably Cretaceous: Yosemite National Park.

F. C. Calkins, 1930 (U. S. Geol. Survey Prof. Paper 160, p. 123). Grayish-white 

mixture of quartz and feldspar in which are embedded elongated grains of 

hornblende and biotite about 1 millimeter in diameter.

Named from occurrence near Pohono Trail, Yosemite National Park.

Poncho Rico formation.

Pliocene and Miocene (?) : Southern California (Salinas Valley).

R. D. Reed, 1925 (Jour. Geology, vol. 33, pp. 591, 592, 605-607). Poncho Rico 

formation. Marine strata variously classed as latest Miocene or earliest 

Pliocene. Overlies Santa Margarita formation; where latter is absent rests 

on Monterey shale. Underlies nonmarine Paso Robles formation. "A striking 

feature of the lower portion of the sandy strata resting on the Monterey shale 

(Sfinta Margarita, in the strict sense) is the large amount of cleanly washed 

white granitic sand that it contains. One sample proved to contain almost 

nothing but quartz grains, an extremely unusual condition for a Tertiary 

sandstone. * * * In higher parts oi' the scries diatomito occurs on a great 

scale; also clastic shale, yellowish sandstone, and conglomerate beds in which 

Monterey shale pebbles play an increasingly prominent role toward the top 

of the series. These are the strata h'ere grouped together as the Poncho Rico 

formation."

These beds were identified as Jacalitos and Etchegoin formations by W. A.

English in United States Geological Survey Bulletin 691, page 231, 1919. 

Probably named for exposures along or near Poncho Rico Creek, Monterey

County.

Potato sandstone.

Miocene, probably : Southern California (San Bernardino Mountains).

F. E. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13. 

No. 9, pp. 344, 374-375, map). Very hard sandstone, entirely different from 

any other rock in district. For most part is a well-bedded coarse angular 

arkose with angular boulders of schist and granite. A yellowish variety 

predominates, but there are also finer greenish and some red varieties. A 

few thin beds of shale are found between the sandstone strata. Bedding 

varies in thickness from a few inches to more than 30 feet. Age not definitely 

determined. The intense shearing and induration indicate that it is older 

than Hathaway formation and Santa Ana sandstone. Is believed to be 

younger than Saragossa quartzite, but relations are obscure. Tentatively considered Miocene. Resembles Puente sandstone, of Miocene age.

Named for Potato Canyon, San Bernardino County. Forms the portion of 

the ridge between Potato Canyon and Mill Creek east of Wilson Creek.

Potem formation.

Middle and Lower Jurassic: Northern California (Redding quadrangle).

J. S. Diller, 1906 (U. S. Geol. Survey Geol. Atlas, Redding folio, No. 138). Sandstones, shales, and tuffs. Thin-bedded sandstones and gray, sometimes slaty 

shales predominate in its lower part and make up the greater portion of the 

formation. They are more or less calcareous and contain a few small lentils 

of limestone. Tuffaceous conglomerates occur sparingly in lower half of 

formation, but in upper part are most abundant in fact, nearly all the sediments of this part are of igneous material, some of which may have been 

furnished by contemporaneous volcanic activity, but most of it was derived 

by the ordinary processes of erosion from a wide expanse of volcanic rocks. 

"Must be at least several thousand feet thick" [2,000± in columnar section]. 

Regarded as equivalent to Hardgrave sandstone and most likely the Mormon 

sandstone also. Underlies Chico formation and overlies in places Bagley
GEOLOGIC UNITS OF CALIFOBKIA 63

andesite and in other places rests, probably conformably, on Modln formation. 

[See also under Bagley andesite.} Named for development on Potem Creek, 

Shasta County.

Poway conglomerate.

Tertiary (Eocene) : Southern California (San Diego County).

A. J. Ellis, 1919 (U. S. Geol. Survey Water-Supply Paper 446). Chiefly conglomerates, but lenses of cross-bedded sand and thin layers of marly clay are 

exposed in some of the canyon walls. Forms Poway Mesa and occurs in a 

narrow belt extending from that mesa eastward to Witch Creek. Also well 

exposed near town of Poway and forms south wall of Poway Valley. Maximum 

thickness west of Foster is about 1,000 feet. No fossils found and relations 

to marine San Diego formation not determined, but probably is somewhat 

older than-the upper part of the San Diego. Rests on pre-Tertiary crystalline 

rocks.

M. A. Hanna, 1926 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 16, No. 7), 

says fauna is Eocene and tentatively correlates formation with the Tejon 

formation.

Prospect Mountain quartzite.

Lower Cambrian: Northern Nevada.

Arnold Hague, 1883 (U. S. Geol. Survey Third Ann. Rept, pp. 253, 254). Bedded

brownish-white quartzites weathering dark brown; ferruginous near base;

intercalated with thin layers of arenaceous shales; beds whiter near summit.

Thickness 1,500 feet. Oldest sedimentary rock exposed in Eureka district.

Directly overlain by Prospect Mountain limestone [name now replaced by

Eldorado limestone]. Named for occurrence in Prospect Peak, Eureka district,

Nev.

This formation has been mapped by S. H. Ball (U. S. Geol. Survey Bull. 

308, 1907) in Inyo County, Calif.

Puente formation.

Miocene (upper and middle) : Southern California (Puente Hills and Los 

Angeles district).

G. H. Eldridge and R. Arnold, 1907 (U. S. Geol. Survey Bull. 309). Puente formation. Miocene deposits unconformably underlying the Fernando formation 

in the Puente Hills [southern part of Los Angeles County] and Los Angeles 

district. Consists, in descending order, of

Upper Puente shale. 300-2,000 feet. (Earthy chalklike shale with a 

few beds of fine yellow ferruginous sandstone and quartzo calcareous 

concretions.) Resembles Monterey shale.

Puente sandstone. 300-2,000 feet. (Moderately coarse gray and yellow 

heavy-bedded sandstone separated by minor bands of organic siliceous 

shale.)

Lower Puente shale. 2,000 feet. (Chiefly earthy shale, but with minor 

members of a siliceous nature, the whole gray or brown from presence 

of iron and bitumen. Thin, fine-grained sandstones interbedded from 

top to base, and lentils of gray limestone. This is lowest rock 

exposed in Puente Hills.)

Is unconformably overlain by Fernando formation, and overlies, unconformably, 

pre-Cretaceons granite and schist.

According to W. S. W. Kew (U. S. Geol. Survey Bull. 753, pi. 3, 1924) 

the Puente formation of the Puente Hills corresponds to the Modelo 

formation of Bulletin 753, and the Puente formation of the Los 

Angeles district corresponds to the Modelo and underlying Topanga 

formation of Bulletin 753.

 ' Puente sandstone." See under Puente formation. 

" Puente shale." See under Puente forriiation.

"Pulaski sand."

A sand bed, about 40 feet thick, in the Vaqueros sandstone in the Coalinga 

district, lying about 40 feet below the " Sauer Dough."
64 GEOLOGIC UNITS OF CALIFORNIA

Purisima formation. ,, 

Pliocene: Western California (Santa Cruz Mountains).

H. L. Haehl and R. Arnold, 1904 (Air'. Philos. Soc. Proc., vol. 43, pp. 16-53). Finegrained sandstones and shale 700 feet thick resting on basal conglomerate 20 , 

feet thick. At top grades into beds having a fauna somewhat similar to that 

of the Merced formation. " Its upper limit may be defined as the base of 

the Merced." Rests unconformably on Monterey shale.

Named for exposures near Pu'ris'ima and along Purisirna Creek, San Mateo

County. -*

Radcliff formation. ^ 

Lower Paleozoic (?) : Southeastern California (Inyo County). 

See under Telescope group. Derivation of name not stated.

" Rainbow beds." See under " Coalinga beds."

Rainbow series.

Post-Franciscan: Northern California (Humboldt County). *

W. Stalder, 1915 (California State Min. Bur. Bull. 69, pp. 447-449). Post-Franciscan and pre-uppei1 Miocene rocks of Rainbow Ridge, divided into Walker 

Ridge sandstones above, 50 to 750 feet thick, and Walker Ridge shales below, 

500 to 1,500 feet thick. Underlies Bear River series (upper Miocene) and 

overlies post-Franciscan rocks called basal sandstone series.

" Raised Beach formation." t 

Pleistocene: Southern California (San Pedro and vicinity). 

R. Arnold, 1903 (California Acad. Sci. Mem., vol. 3), applied this nongeographic terra to beds younger than San Pedro series. . ^

Rand schist.

Archean: Southern California (Randsburg quadrangle, Kern and San

Bernardino Countie.?)- ,.

C. D. Hulin, 1925 (California State Min. Bur. Bull. 95, pp. 23-29, map). Predominately a mica-albite schist, showing highly developed schistosity ; usually dark 

silvery, gray, but weathers yellowish brown. Amphibole schists are next in 

order of abundance and are only slightly subordinate in amount to the micaalbite schist. Actinolite schist, actinolite-talc scbist, talc schist, and hornblende schist also occur in minor amounts. The mica-albite schist and the 

amphibole schists are interbedded with quartzite and limestone in beds from 

1 to 10 feet thick. Greenstone schist, of igneous origin, is present in small, 

irregular, and. isolated masses. The rest of the formation is of sedimentary ~i 

origin. It is believed to unconformably overlie Johannesburg gneiss and to 

unconformably underlie the rocks of Paleozoic age. Assigned to Archean. 

Thickness exposed is probably between 1,500 and 2,000 feet. Composes the 

bulk of the Rand Mountains, Kern County.

Rattlesnake granite. ^ 

Probably pre-Cretaceous: Southern California (San Diego County). '

F. S. Hudson, 1922 (California Univ. Pub. Dept. Geol. Sci. Bull., vol. 13, No. 6, \ 

pp. 181, 207-20S, map). A true granite, varying from an alaskite to a biotitehornblende granite. Intrudes rocks of probable Triassic age.

Named for Rattlesnake Valley, Cuyamaca region, San Diego County. '

Ravenna plutonic series. < 

MesozoicC?): Southern California (Los Angeles County).

0. H. Hershey, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 3, pi. 1, map). 

[Maps but does not describe Ravenna plutonics. As mapped lies between Cretaceous shales above and the granite below.] (Am. Geologist, vol. 29, p. 284). * 

" Ravenna plutonic series. I predict it will be found to be Mesozoic in age and 

Just a little older than the granitic series." " ,'

Probably named for occurrence at Ravenna station, Los Angeles County,

around which it is mapped. f
GEOLOGIC UNITS OP CALIFORNIA 65

Red Bluff epoch.

Pleistocene: California.

0. H. Hershey, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 3, pp. 1-29). 

Red Bluff epoch (deposition). Divided into Red Bluff proper above, and below 

a sheet of alluvium of same material as Red Bluff proper. Believe that Arnold's 

Lower San Pedro series corresponds in part at least with the Red Bluff formation. " It seems proper to extend the term Red Bluff to the marine Pleistocene 

in Los Angeles and to the alluvial material of the 400-foot terrace of Soledad 

Canon." [See under Sierran.]

Hed Bluff formation.

Pleistocene: Northern California (Redding region).

J. S. Diller, 1894 (U. S. Geol. Survey Fourteenth Ann. Rept, pt. 2, pp. 413-416, map,

pi. 44). Gravels, clay, and sand of Pleistocene age, overlying Tuscan tuff. 

J. S. Diller, 1906 (U. S. Geol. Survey Geol. Atlas, Redding folio, No. 138). Chiefly

gravel and sands, with a small proportion of clay, and a few large boulders.

TJnconformably overlies Tuscan tuff. Thickness more than 200 feet.

Named for exposures at Red Bluff, Tehama County.

Redlands limestone.

Lower Paleozoic (?) : Southeastern California (Inyo County). 

See under Telescope group. Derivation of name not stated.

Red Mountain andesite.

Miocene (upper) : Southern California (Randsburg quadrangle, Kern and 

San Bernardino Counties).

C. D. Hulin, 1925 (California State Min. Bur. Bull. 95, pp. 55-58, map). Chiefly 

lava flows, but with prominent amounts of agglomerates and tuffs. The general 

composition of the series is that of a basic andesite. Overlies Rosamond series, 

usually with angular unconformity, and unconformably underlies Black Mountain 

basalt. Forms a thick capping of the Rosamond series in Red Mountain [San 

Bernardino County], where it reaches an approximate thickness of 1,400 feet of 

flows and pyroclastics. Believed to be early Pliocene.

Hedrock Canyon sandstone member.

Miocene (upper) : Southern California (Cuyama Valley, southwestern part 

of Kern County)..

W. A. English, 1916 (U. S. Geol. Survey Bull. 621, pp. 191-215). Basal member of 

Santa Margarita formation in a small area in Redrock Canyon (Cuyama Valley), 

to which it is limited. Thickness 500 feet. Consists of bright-red sandstone, 

clay, and conglomerate, the materials of which were derived from an adjacent 

land mass of pre-Monterey rocks. Rests unconformably on pre-Monterey rocks, 

the Monterey group being absent, probably through erosion. Is conformably 

overlain by Whiterock Bluff shale member of the Santa Margarita.

'" Red Rock Canyon beds."

Pliocene (lower) : Southern California (eastern part of Kern County).

J. C. Merriam, 1919 (California Univ. Pub., Dept. Geology Bull., vol. 11, No. 5). 

There may be some justification for name Red RocTc Canyon beds, formation, or 

group, for stratigraphic sequence containing the Ricardo fauna, but G. K. Gilbert 

(Geog. and Geol. Expl. W. 100th Mer., pp. 142-143, 1875) and H. W. Fairbanks 

(Am. Geologist, vol. 17, pp. 68-69, 1896) did not use the name for nomenclature 

purposes. Following the discovery that the fauna from the beds in Red Rock 

Canyon [at Ricardo, eastern part of Kern County] is sharply distinct from that 

in the Barstow section, the writer has described numerous mammalian forms 

from the Red Rock Canyon section as representing the Ricardo fauna, Ricardo 

T)e<i?f<, or Ricardo Pliocene, and be therefore prefers the name Ricardo formation 

or Ricardo group for the deposits containing them.

Heed dolomite.

Pre-Cambrian: Eastern California (Inyo Range).

E. Kirk, 1918 (U. S. Geol. Survey Prof. Paper 110). Heavy-bedded dolomite, much 

jointed and breaking up into large angular blocks that form rough talus slopes. 

Varies from aphanitic to coarsely crystalline. White or slightly bluish on fresh
66 GEOLOGIC UNITS OF CALIFOBNIA

fracture. Weathers slightly creamy to buff. Thickness about 2,000 feet. Unconformably underlies Deep Spring formation. Is underlain by thin-bedded arenaceous slates which grade down into more heavily bedded sandstones. Named 

for exposures for several miles along eastern side of Reed Flat; best section is in 

canyon at head of Wyman Creek, in sec. 7, T. 6 S., R. 35 B.

"Reef bed."

* Miocene: Southern California. 

See under " Coalinga beds"

Reeve ineta-andesite.

Pennsylvanian: Northern California (Taylorsville region).

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Volcanic, tuffaceous, porphyritie 

meta-andesite, about 200 feet thick. Occurs as a definite flow and tuff. Is intimately associated with Robinson formation, into which it grades. Appears to be 

 younger than the Kettle meta-andesite.

Named for an unidentified locality near Genesee, east of Taylorsville.

Relief quartzite.

Mississippian: Northern California (Coifax quadrangle).

W. Lindgreu, 1900 (U. S. Geol. Survey Geol. Atlas, Colfax folio, No. 66). Very hard 

grayish or yellowish siliceous rock of fine grain and clastic origin, which might 

be characterized as a very fine grained quartzite alternating with streaks of siliceous clay slates. The quartzite is completely filled by small irregular bunches 

and veinlets of white quartz. No fossils. Corresponds to part of Calaveras formation. Overlies Blue Canyon formation and underlies Cape Horn slate. Named* 

for exposures at Relief. Best exposures in canyons of South Fork of Yuba River 

below Relief, Bear River, and Steep Hollow north of Dutch Flat.

According to later work by H. G. Fergusou (Am. Inst. Min. and Met. Eng. 

Tech. Pub. 211, p. 4, 1929), two formations (Tightner below and Kanaka 

above), composed of interbedded sedimentary and igneous rocks, are 

now discriminated between Blue Canyon formation and Relief quartzite.

Reward conglomerate.

Pennsylvanian: Eastern California (Inyo Range).

E. Kirk, 1918 (U. S. Geol. Survey Frof. Paper 110). Conglomerate composed of 

coarse material of both angular and rounded fragments of red, brown, and white 

grits, together with jasper, brown hornstonc, and green chcrty pebbles firmly' held 

together by a siliceous cement. , A brownish-weathering sandstone with darkbrown patches and layers forms the uppermost 100 feet of the Reward north of 

Union Wash. Thickness of formation 100 to more than 350 feet, tlnconforroably underlies Owenyo limestone (Permian) and conformably overlies Pennsylvanian limestone and shale. Named for bold exposures just south of Reward 

mine.

Ricardo formation.

Pliocene (lower) : Southern California (Kern and San Bernardino Counties).

J. C. Merriam, 1914 (California Univ. Pub., Dept. Geology Bull., vol. 8, pp. 276, 278). 

" The Ricardo Pliocene is the next faunal stage known after the Mohave in the 

Great Basin." A series of beds, occurring at Ricardo [Kern County], on the 

western border of the Great Basin, representing a faunal and stratigraphic stagewhich is distinctly pre-Pleistocene, is certainly much later than the Mohave 

Upper Miocene, and presumably represents early Pliocene. Doubtful that much, 

if any, of the Pliocene of King really represents the Ricardo stage.

J. C. Merriam, 1915 (Pop. Sci. Monthly, vol. 86, pp. 252-254). The Ricardo beds 

contain Pliocene mammals.

J. C. Merriam, 1917 (California Univ. Pub., Dept. Geology Bull., vol. 10, pp. 430-443). 

Ricardo formation. Thickness 3,000 to 5,000 feet. Contains Pliocene fauna. 

The beds in which the fauna occurs consist in large part of tuffs with desert 

conglomerates or fanglomerates and other deposits formed on land or in evanescent water bodies. Fauna seems to be a unit not divisible into sharply separated stages and indicates an earlier stage than Thousand Creek and Rattle-
GEOLOGIC UNITS OF CALIFORNIA 67

snake, which te supported by greater degree of induration and deformation of 

the Ricardo. Is younger than Barstow formation. 

J. C. Men-lain, 1919. (See under "Red Rock Canyon beds.")

Robinson formation.

Pennsylvanian: Northern California (Taylorsville region).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Robinson beds. 

Slates, conglomerates, tuff, and sandstone, of which the last two are most important. Thickness 1,150 feet. Uppermost Carboniferous formation in Taylorsville region. Fossiliferous. Younger than Shoofly beds and older than Hosselkus 

limestone and Swearinger slate.

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Robinson formation. A succession 

of variable sediments ranging from shale to conglomerate and composed chiefly 

of igneous material with occasional lentils of limestone. Most characteristic 

portion is gray sandstone that weathers reddish brown. Contains more or less 

disseminated carbonate of lime forming small lentils up to 15 feet in thickness. 

Below the calcareous horizon the reddish-brown thin-bedded tuffaceous sandstone 

and shale extend to bottom of formation. Above the calcareous horizon the 

pyroclastic material becomes somewhat coarser and passes into a tuffaceous conglomerate containing fossiliferous limestone nodules and beds of reddish-brown 

sandstone, with here and there crinoid stems like that of the principal horizon 

below. [Fossils listed.] Is separated from the older Peale formation by the 

Reeve meta-audesite. Is unconformably overlain by Hosselkus limestone.

Named for exposures on the Robinson ranch (where it makes up the mound 

east of the house), near Taylorsville.

Hodeo shale.

Miocene (middle) : Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Bituminous shale, mostly chalky and more or less stained with oxide of iron but 

is locally cherty. A subdivision of the Monterey group. Underlies Briones 

sandstone and overlies Hambre sandstone. Thickness 670 feet. Named for 

exposures along Rodeo Creek, in the northwestern part of Concord quadrangle, 

Contra Costa County.

 "Rosamond series."

Tertiary: Southeastern California (southeastern Kern County and northern 

Los Angeles County).

0. H. Hershey, April, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 3, pi. 1, 

map). [On legend of map appears between Cretaceous shales below and 

Escondido series above, and is mapped to the north of Rosamond, Kern County.]

0. H. Hershey, 1902 (Am. Geologist, vol. 29, pp. 349-372). A rhyolite series, 1,650 

feet thick, consisting of interbedded sandstone and rhyolite tuff with one massive

o bed of dark-red lava. Unconformably underlies Barstow series. Type section 

near Rosamond station.

J. C. Merriam, 1919 (California Univ. Pub., Dept. Geology Bull., vol. 11, No. 5, 

pp. 440-448). While the name Rosamond series may be tentatively used for 

tlie middle and late Tertiary sediments of Mohave area it has not been demonstrated that the several formations represented are as closely related in their 

dcpositional history as they appeared in the first investigations. If the Barstow 

formation is a member of the Rosamond series of Hershey it is a late member. 

It will be recognized as a division of the Rosamond series. It is doubtful if 

the Rosamond series comprises sediments of the stage represented at Ricardo.

Hose Canon shale.

Eocene: Southern California (San Diego County).

M. A. Hanna, 1926 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 16, No. 7, 

pp. 187-246). Mudstones, gray shales, fine sands, conglomerates, and a few 

thin beds of limestone. The sandstones are usually fine grained and vary from 

light to dark brown. Lower part is cross-bedded. Thickness about 300 feet. 

Is upper division of La Jolla formation. Disconformably underlies Poway conglomerate and grades into underlying Torrey sand. In northwestern part of 

quadrangle rests with marked angular unconformity on Black Mountain volcanics. Named for exposures at big bend in Rose Canon, La Jolla quadrangle. 

Contains brackish-water fauna.
68 GEOLOGIC UNITS OF CALIFORNIA

" Sacramento " formation.

Middle Devonian: Northern California (Redding region).

J. P. Smith, 1894 (Jour. Geology, vol. 2, pp. 591, 592). [In heading and table this 

name is used to cover the Kennett limestones and shales, and is credited, in 

footnote, to H. W. Fairbanks MS. A later publication by J. P. Smith (California 

State Min. Bur. Bull. 72, 1916) states that the Middle Devonian limestones of 

Kennett and Lower Soda Springs occur in the Sacramento Canyon.J

Same as Kennett formation.

Sailor Canyon formation.

Upper Triassic (J. P. Smith, 1910) : Northern California (Colfax region).

H. W. Turner, 1894 (Am. 'Geologist, vol. 13, p. 232). Sailor Canyon beds. At 

Sailor Canyon, which drains into the American River about 6 miles southeast of 

Cisco, are a series of beds from which Mr. Lindgren and Dr. Cooper Curtice have 

collected fossils regarded by Hyatt as of Liassic [Lower Jurassic] age. Considered older than Milton and younger than Cedar formation.

W. Lindgren, 1900 (U. S. Geol. Survey Geol. Atlas, Colfax folio, No. 66). Sailor 

Canyon formation. Calcareous clay slates with some limestone and a contactmetamorphic facics consisting chiefly of mica schist and hornfels. Younger than 

Calaveras formation and older than Mariposa slate.

The Sailor Canyon formation has an estimated thickness of 6,000 feet.

St. Helena rhyolite.

Pliocene: Northern California (Sonoma County).

V. C. Osmont, 1904 (California Univ. Pub., Dept. Geology Bull., vol. 4, pp. 59-87).. 

Of varying thickness up to 2,000 feet. Rests conformably on Sonoma tuff.

Apparently named for occurrence on Mount St. Helena, Sonoma County.

" St. Paul sand."

A sand, about 30 feet thick, occurring toward the top of the Santa Margarita formation in the Coalinga district, in the vicinity of the California 

Oilfields property, sec. 27, No. 20, and extending down into northern 

part of sec. 34. It lies about 830 feet above the base of the Big Blueserpentinous member and from 150 to 600 feet beneath the surface.

Salinas shale.

Miocene (middle) : Southern. California (Salinas Valley region).

W. A. English, 1918 (U. S. Geol. Survey Bull. 691, pp. 219-250). Probably the best 

known of the California Tertiary formations is the marine diatomaceous shalewhich extends from Monterey southward. This shale was known as " bituminous 

shale" by the early California geologists but is now commonly called the- 

" Monterey shale." The name Monterey has been adopted as a group name by 

the United States Geological Survey to include the so-called " Monterey shale " 

and the underlying Vaqueros sandstone. The name " Monterey shale " is therefore no longer applicable as a formation name. The name Maricopa shale was 

used in the writer's report on the Cnyama Valley (U. S. Geol. Survey Bull. 

621, 1916) on the mistaken assumption that the shale previously called " Monterey shale" was essentially contemporaneous with the shale exposed in thevicinity of Maricopa, but the latter has since been found to include representatives not only of the shale previously called " Monterey" in the area under 

consideration but also of the overlying Santa Margarita formation. The name 

Maricopa shale is therefore not appropriate as a substitute for " Monterey shale."' 

The name Salinas shale Is here proposed for the diatomaceous shale which is well 

developed on the west side of the Salinas Valley within the area mapped and 

which is believed to extend as a single formation northward along the west 

side of the valley to the town of Monterey.

Is treated by United States Geological Survey as the upper formation of theMonterey group, of which the Vaqueros sandstone is the lower 

formation.
GEOLOGIC UNITS OF CALIFOKNIA 69

Salmon hornblende schist.

Pre-Cambrian (?) : Northern California (Trinity and Shasta Counties).

0. H. Hershey, 1901 (Am. Geologist, vol. 27, pp. 225-245). Salmon hornblende 

sclvist. Of remarkable uniformity throughout its thickness of probably not less 

than 2,500 feet. The largest area of this schist is traversed by the south fork 

of Salmon River between its head and the vicinity of the village of Cecilville.

According to J. S. Diller and H. G. Ferguson (unpublished manuscript 

on Weaverville quadrangle) is probably intrusive into Abrams mica 

schist.

San Antonio formation.

Pleistocene: Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

San Antonio formation. A great series of alluvial fans at the foot of the steep 

face of the Berkeley Hills between Bast Oakland and Berkeley, built up by 

streams that emerge from the hills. Is divisible into an older gravel, which 

consists of rock fragments derived from the front of the hills and does not contain any chert, and a later or upper part, here called the chert-gravel member, 

because it contains abundant fragments of chert. The formation has been 

thoroughly dissected and terraced. [Fossils listed.] Unconformably underlies 

Merritt sand and unconformably overlies Alameda formation. Named for development in San Antonio Township, Alameda County.

San Benito gravels.

Pleistocene: Western California (San Benito County).

A. C. Lawson, 1893 (California Univ. Pub., Dept. Geology Bull., vol. 1, pp. 151- 

153). [Correlates the Merced "series" (Pliocene) with the delta gravels on 

the San Benito. On p. 153 he casually uses the term San Benito gravels, but 

apparently not as a geologic name.]

P. F. Kerr and H. G. Schenck, 1925 (Geol. Soc. America Bull., vol. 36, pp. 468-469, 

470, 477, map). Yellow loosely consolidated sandstones, blue shale, blue, red, 

and gray bedded gravel, indurated sandstone in places, strata often, brilliantly 

colored. Thickness 1,000 ± feet. " The gravel was called Pliocene by Whitney 

and accepted by Lawson, but they carry characteristic Pleistocene vertebrate 

fossils. * * * These Pleistocene gravels were named ' San Benito gravels' 

by Lawson (1893), who thought they were Pliocene in age." Unconformably 

overlie Pliocene Paicines formation. [The formation is mapped along San 

Benito River.]

San Bruno sandstone.

Jurassic (?) : Western California (San Francisco region).

R. Crandall, 1907 (Am. Philos. Soc. Proc., vol. 46, pp. 3-58). San Bruno sand' 

stone. Chiefly hard blue-gray sandstone intcrbedded with shales and some coarse 

conglomerates; several hundred feet of sandstone at top. Thickness great. Is 

a subdivision of the Franciscan series. Overlain by the lower jasper bed of the 

Franciscan and rests on crystalline limestones of the Franciscan. Named for 

fact that it forms San Bruno Mountains.

A. C. Lawson (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193, 

1914) mapped the above-described rocks as Cahil sandstone, toward the 

middle of which occurs the Calera limestone member. As Crandall's 

San Bruno sandstone rests on the limestone it is equivalent to the upper 

part of the Cahil sandstone of Lawson.

San Diego formation.

Pliocene (middle?) : Southern California (San Diego region).

W. H. Ball, 1897 (U. S. Geol. Survey Eighteenth Ann. Rcpt., pt. 2. p. 337). San 

Diego 'beds. Pliocene sandy marls exhibited in well explored by Hctnphill in 

city park; bolow Pleistocene at Pacific Beach, San Diego, on shoies of False Bay 

near by; and on Coronado Peninsula opposite San Diego. The same horizon 

crops out in various places northward, especially at Dead Mans Island and Harbor Hill, San Pedro, and on coast of Todos Santos Bay, Lower California.
/U GEOLOGIC UNITS OF CALIFORNIA

A. J. Ellis, 1919 (U. S. Geol. Survey Water-Supply Paper 446). Sam Diego formation. An extension of Dall's use of the name. Consists of lenticular deposits 

of conglomerate, sandy marls, sand, and clay, with rare lenses of limestone. 

The sandy marls which are exposed arouncl Mission Bay and in Mission Valley 

and underlying the conglomerates east of San Diego have been referred to in 

the literature as the San Diego beds. Fossil collections obtained from them 

have been classified as Pliocene. Orcult has assembled data in regard to fossil 

collections obtained from these deposits in a well boring in the city of San Diego. 

The beds described by Orcutt are near base of later Tertiary section. They are 

best developed in immediate environs of city of San Diego, but they have been 

recognized by their lithologic character as far south as Otay and in the northern 

part of the area in the vicinity of Oceanside. They seem to be integral parts 

of a simple formation and chronologically inseparable from the other lenticular 

 strata with which they arc interbedded. On this ground it is proposed to include all the later Tertiary marine deposits in this area under the name San 

Diego formation. It is essentially a shallow-water deposit. Rests on Eocene 

beds and is overlain by San Pcdro formation. Thickness 500 feet.

San Dimas formation.

Quaternary (?) : California .(southwestern part of San Bernarclino County).

R. Eckis, 1928 (Jour. Geology, vol. 36, pp. 228, 235-236). San Dimas formation on 

map, San Dimas alluvium in heading. Dissected alluvium with decomposed 

gravels of red, brown, or yellow color commonly occurring as high fan-head remnants and as isolated or nearly isolated ruidfan mesas. Called " earlier alluvium " by W. C. Mendenhall in United States Geological Survey Water-Supply 

Paper 219, pages 10-12, 1908. Type locality is at San Dim-as, 5 miles west 

of Claremont. Overlain by Recent alluvium, from which it is sometimes difficult 

to distinguish, it. Is generally: undeformed.

San Emedio series.

Pre-Cambrian( ?) : Southern California (Kern County).

0. H. Hershey, April, 1902 (California Univ. Pub., Dcpt. Geology Bull., vol. 3, pi. 1,

map). [/S'an Emedio schists on legend of map lie between Cambrian above and

Afchean gneiss below.] 

0. H. Hershey, 1902 (Am. Geologist, vol. 29, pp. 273-290). A series of thoroughly

crystalline schists and limestone. Tentatively assigned to pre-Cambrian(?).

Relations to Pelona schist series unknown and can not be conjectured.

Probably named for San Emedio Range.

" San Emigdio formation."

Oligocene: Southern California (Kern County).

G. C. Gester, 1917 (California Acad. Sci. Proc., 4th ser., vol. 7, plate opp. p. 220). 

[Gives a section of Midway and Tejon districts, in which the name San Emigdio 

is applied to shales and sands underlying the lower Miocene and apparently 

referred to the Oligocene.]

C. M. Wagner and K. H. Schilling, 1923 (California Univ. Pub., Dept. Geology Bull., 

vol. 14, pp. 235-252). San Emigdio formation. Basal formation of San Lorenzo 

group [expanded definition]. Discouformably underlies Pleito formation, the 

upper formation of the San Lorenzo group, and unconfovmably overlies Tejon 

formation. East of San Emigdio Canyon it consists of 700 feet of alternating 

yellowish and grayish sandstones and sandy shales containing very fossiliferous 

dark-red bands, and lenses ; underlain by 150 feet of bluish-black shale carrying 

fossils in calcareous concretions; with, at base, 150 feet ot light-gray and tan 

unfossiliferous sandstone, in places conglomeratic and gritty. Mapped along 

east side of San Emigdio Creek, southwestern part of Kerii County. Carries 

Molopopliorus linconensls zone. Correlated with Butano sandstone, which is 

older than typical San Lorenzo formation.

Is a fauna! zone in San Lorenzo formation.

" San Francisco group."

Late Tertiary and Franciscan (Jurassic?) : Western California (San Francisco region).

J. S. Newberry, 1857 (Pacific R. R. Repts., vol. 6, pt. 2, pp. 10-12). Upon the 

serpentine lies a deposit of sandstones and shales, several hundred feet in thickness. They are somewhat interstratifled, their strata conformable and apparently
GEOLOGIC UNITS OF CALIFORNIA 71

belonging to the same geological epoch, being members of a group widely spread 

over the Pacific coast, and to which, under the name of Sun Francisco group, 

I shall frequently have occasion to refer. The sandstone where long exposed 

is light gray, soft, and easily worked. It forms the slopes of the axis lying 

between the Bay of San Francisco and the ocean and the rocky basis upon 

which the city of San Francisco rests. The shales are greenish or yellowish 

brown. No fossils found in either the sandstone or shale in vicinity of San 

Francisco, but on San Pablo Bay this group is highly fossiliforous. Assigned 

to Miocene.

Apparently includes Franciscan and late Tertiary rocks.

" San Francisco sandstone."

Jurassic (?) and late Tertiary: Western California (San Francisco Bay 

region).

W. P. Blake, 1856 (Pacific R. R. Repts., vol. 5, pp. 145-156). Fine-grained compact 

sandstones associated with thin shales. Thickness 1,000 to 3,000 feet. Tertiary 

in part at least, but Upper Cretaceous may also be represented. Forms greater 

part of hills and mountains around the [San Francisco] bay and, so far as explored, a considerable part of the mass of the Coast Mountains. " Is believed to 

be the most extensive and highly developed sedimentary formation of the California coast, and may appropriately he known as the San Francisco or California 

sandstone." [Includes sandstones of Franciscan group and rocks belonging to 

the Merced formation.]

A. C. Lawson, 1895 (Am. Geologist, vol. 15, p. 347 ; U. S. Geol. Survey Fifteenth Ann. 

Rept., p. 417). San Francisco sandstone, the dominant-sedimentary formation 

of the Franciscan series, consists of moderately fine-grained sandstone with subordinate beds of shale and conglomerate. Is interbedded with foraminiferal limestones, radiolarian cherts, and volcanic rocks, including basaltic lavas, diabases, 

pyroclastic accumulations, etc.

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

[Divides the Franciscan rocks into five named formations, three of which are 

sandstone.]

The term " San Francisco sandstone " is no longer used by geologists.

San Joaquin clays.

Pliocene: Southern California (San Joaquin Valley).

F. M. Anderson, 1905 (California Acad. Sci. Proc., 3d ser., vol. 2, pp. 178-192). 

Name applied to upper one-third of Etchegoin formation. [See description under 

Etcliegoin formation.]

San Juan Bautista formation.

Oligocene:. Southern California (San Benito County).

1'. F. Kerr and H. G. Schenck, 1925 (Geol. Soc. America Bull., vol. 30, pp. 470, 471, 

472, 493, map). Blue'indurated calcareous sandstone; also line-grained argillaceous buffi-colored sandstone, carbonaceous grit, and clay shale. Thickness about 

1,500 feet. Base not exposed. Contains numerous fossils, which establish its 

Oligocene age and marine origin. Lower formation of San Lorenzo series. 

Named for exposures in vicinity of San Juan Bautista.

San Lorenzo formation.

Oligocene: Southern California (Santa Cruz Mountains region).

R. Arnold, 1906 (U. S. Geol. Survey Prof. Paper 47, p. 16). San Lorenmo formation. 

Essentially a series of grayish " muddy " shales and fine sandstones, typically 

exposed along the bed of San Lorenzo River about 2 miles above Boulder Creek, 

Santa Cruz County. . Extends westward from type locality into the Big Basin, 

on the north side of which it rests conformably against the older yellowish 

sandstones (possibly Oligocene in age) of Butano Ridge [later named Butano 

sandstone]. Conformably [unconformably] underlies Vaqueros sandstone. 

[Fossils listed.] Thickness about 2,300 feet in vicinity of type locality.

In 1918 (California Univ. Pub., Dept. Geology Bull., vol. 11, pp. 54-111) 

B. L. Clark used the term San Lorenzo series to include "all of the 

known marine beds in California, Oregon, Washington, and British Columbia that have generally been referred to the Oligocene." In the
72 GEOLOGIC UNITS OF CALIFORNIA

Sobrante anticline, in the Concord quadrangle, he divided his San Lorenzo series into (descending order) Concord formation (=lower part 

of Lawson's Sobrante sandstone), Kirker tuff, and San Ramon formation, and stated that it represents the Agasoma gramdiim zone. In this 

expanded San Lorenzo Clark now includes the lower part of the Sobrante 

sandstone of Lawson ; the San Lorenzo formation and underlying Butano 

sandstone of the Santa Cruz Mountains and their equivalent; and the 

Kreyenhagen shale.

The United States Geological Survey recognizes San Lorenzo formation as 

originally.defined, and as distinct from Butano sandstone.

" San Luis " formation.

Jurassic (?) : Southern California (San Luis Obispo region).

H. W. Fairbanks, 1904 (U. S. Geol. Survey Geol. Atlas, San Luis folio, No. 101). 

Usually earthy sandstone, but in places there is a great thickness of dark shale 

very similar to the Toro formation. Contains many lentils of radiolarian jasper 

and some contact-metamorphic schist. Local representative of the Franciscan. 

Represents all of the Franciscan present in the area. TJnconformably underlies 

Toro formation (Knoxville) and unconformably overlies serpentine and other 

basic igneous rocks. Named for development in San Luis Valley, San Luis 

Obispo County.

Replaced by Franciscan formation.

San Mateo formation.

Pliocene (?) : Southern California (San Diego and Orange Counties). 

A. O. Woodford, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 7, 

pp. 169, 217-219). " Post-Cayistrano formation. The younger [than Capistrano formation] rocks are of slight significance in the present study. They are 

very patchy in distribution and lie unconformably on the older rocks. There is 

the tilted San Mateo formation, doubtful correlative of the San Diego Pliocene, 

consisting of arkosic sands and gravels with a little admixture of blue schists, 

and containing an occasional marine fossil; and topping all the very slightly 

deformed or untilted Terrace gravels and alluvium." Thickness several hundred 

feet. Classified as Pliocene (?). [Mapped.]

Named for occurrence along San Mateo Creek, in northwest corner of San 

Diego County.

" San Miguel cherts."

Jurassic (?) : Western California (San Francisco region).

R. Arnold, 1902 (Science, new ser., vol. 15, p. 416). San Miguel cherts, radiolarian,

530 feet thick. Underlie Bonita sandstone and overlie Marin sandstone. A

formation in the Franciscan. 

A. C. Lawson, 1903 (Geol. Soc. America Bull., vol. 13, pp. 544-545). [Same as

above.] 

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193).

[The rocks of San Miguel Hills, San Francisco County, which appears to be

the type locality, are mapped as Ingleside chert, Marin sandstone, and Sausalito

chert. The name San Miguel is preoccupied.]

San Onofre breccia.

Miocene (lower) : Southern California (San Diego County).

A. J. Ellis, 1919 (U. S. Geol. Survey Water-Supply Paper 446). Very coarse 

breccias or agglomerates, made up almost entirely of angular boulders and 

slabs of garnetiferous glaucophane schists and other schistose rock fragments. 

Forms the San Onofre Hills, in San Diego County. Older than Poway conglomerate and San Diego formation. [M. A. Hanna, 1926 (California Univ. 

Pub., Dept. Geol. Sci. Bull., vol. 16, No. 7) says Poway fauna is Eocene.] 

Assigned to lower Miocene.

A. O. Woodford, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, 

No. 7). [Describes the above formation as the San Onofre fades of the 

Temblor formation or Turritella ocoyana zone, gives the thickness as 2,610 

feet, and states that the Temblor beds underlying the San Onofre facies consist
GEOLOGIC UNITS OF. CALIFORNIA 73

 of 300 feet or more of gray or white sandstone and shale. " Doubtful correlatives " of the San Onofre are described under the headings San Pedro 

schist breccia and sandstone, Catalina schist breccia, and Bouquet Canon 

breccia.]

San Pablo formation.

Miocene (upper) : Western California (San Francisco region).

J. C. Merriam, 1898 (California Univ. Tub., Dept. Geology Bull., vol. 2, pp. 109- 

118). San Pablo formation. Marine sandstones, tuffs, and ashes, 1,500 feet 

thick, characterized by presence of Astrodopsis and Scutella (Glypeaster) 

gabbi. A considerable thickness of tuffs and ashes, most prominent in the 

upper portion of the formation, and the peculiar weathering of the sandstones 

are constant and striking characters of the greatest value in identifying the 

formation where fossil remains are rare or absent. Overlies Contra Costa 

County Miocene, without distinct unconformity, although a break is indicated 

at several localities.

A. C. Lawson, 1914 (U. S. Geol. Survey (?col. Atlas. San Francisco folio. No. 193). 

[Describes the San Pablo' formation as resting unconformably on the Briones 

sandstone, and as unconformably overlain by Pliocene rocks (Pinole tuff in 

some areas and the younger Orinda formation in other areas). According to 

B. L. Clark (Jour. Geology, vol. 29, pp. 586-614, 1921) the San Pablo formation 

(renamed by him Cierbo group) occurs only in the general region of San 

Francisco Bay, lies disconformably below the Santa Margarita formation, and 

rests disconformably on the Briones sandstone.]

Named for occurrence on San Pablo Bay, Contra Costa County, near town 

of Rodeo.

San Pablo group.

San Pablo series.

Miocene (upper) : Western California (coast region).

B. L. Clark and R. Arnold, 1918 (Geol. Soc. America Bull., vol. 29, p. 298). [Apply 

the name San Pablo group to all the upper Miocene deposits of western 

California, including the Briones sandstone at the base and the Santa Margarita formation at the top.]

B. L. Clark, 1921 (Jour. Geology, vol. 29, pp. 586-614). [Uses San Pablo series 

to cover all the upper Miocene formations of western California, including 

Santa Margarita formation, Mint Canyon formation, and Maricopa shale. 

In the Mount Diablo region he divides it, in descending order, into Santa 

Margarita formation (300 to 3,000 feet thick), resting disconformably on 

Cierbo group (600 to 1,300 feet thick and the formation heretofore called 

San Pablo formation), which in turn is disconformable on the Briones sandstone (2,300 feet thick and formerly included in the Monterey group). As 

thus applied the San Pablo series is described as resting on the Rodeo shale 

of the Mount Diablo region, the Salinas shale of the Salinas Valley, and on 

the rocks designated Temblor by B. L. Clark; and it is described as unconformably 

overlain, in different areas, by the Pinole tuff, the Jacalitos formation, and 

the Fernando group. See under Cierbo group.]

San Pedran epoch.

Pleistocene: Southern California.

O. H. Hershey, 1902 (California Univ. Pub., Dcpt. Geology Bull., vol. 3, pp. 1-29). 

San Pedran epoch (deposition). "Arnold's Upper San Pedro series seems to 

include the deposits of the three lower [of the 10] terraces of San Pedro Hill, 

and perhaps it might be convenient to extend the name, in the form of Saw 

Pedran, to the epoch as well." May be approximately equivalent to lowan. 

[He applied Los Angelan epoch to the erosion epoch preceding the upper San 

Pedro and correlated Arnold's lower San Pedro with what he called the 

Red Bluff epoch (deposition). See under Sierran.]

San Pedro formation.

Pleistocene: Southern California (San Diego, Los Angeles, and Ventura 

Counties).

W. H. Dall, 1897 (U. S. Geol. Survey Eighteenth Ann. Rept., pt. 2, 1898 first published in 1897 as 55th Cong., 2d sess., H. Doc. 5 p. 335). San Pedro beds. 
74 GEOLOGIC UNITS OF CALIFORNIA

Extensive beds of unconsolidated Pleistocene sand replete with molluscan shells 

in very perfect condition, best exhibited at Harbor Hill, at head of San Pedro 

Harbor, Los Angeles County. Assigned to Pleistocene. Same horizon is recognizable above the Pliocene of Pacific Beach, San Diego; at various points on 

Coronado Beach peninsula opposite San Diego, especially at a cove called Spanish 

Bight; and also at Santa Barbara and elsewhere. Unconformably overlies 

Merced group.

W. S. W. Kew, 1923 (Am. Assoc. Petroleum Geologists Bull., vol. 7, p. 420). San 

Pedro formation (Pleistocene). This series of beds, which is typically developed 

In the vicinity of San Pedro, has been described in detail By Ralph Arnold 

(California Acad. Sci. Mem., vol. 3, 1903), who has divided it into two members, 

separated by an unconformity. The San Pedro occurs at many places in th« 

Los Angeles Basin, resting unconformably upon the Saugus formation or upon 

beds of San Diego age.

A. J. Tieje, 1926 (Am. Assoc. Petroleum Geologists Bull., vol. 10, pp. 502- 

512), applied Polos Verges spn&s to the upper member and restricted 

San Pedro to the lower member.

The United States Geological Survey follows the original broad definition.

San Pedro schist breccia and sandstone.

Miocene or Pliocene: Southern California (San Pedro and San Pedro Hill).

A. 0. Woodford, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 7, 

pp. 210-211). "San Pedro schist breccia and sandstone. Point Fermin at San, 

Pedro is composed of blue schist sandstone, with a little breccia of various sorts, 

interflngering with more or less purely diatomaceous shale. One may trace in 

the sea cliffs the gradual change from a section that is chiefly blue sandstone to 

one exclusively made up of thin beds of white shale. At the very tip of Point 

Fermin there are 100 feet of tar-saturated blue schist sandstone intercalated in 

the shale series. In this sandstone are included several 1 to 3 foot beds of 

breccia and, near top and bottom, thin beds of shale. * * * The San PedroPoint Fermin Oil & Gas Co. well at Point Fermin passed through the following 

materials (oral communication from officers of the company, supplemented byinspection of samples) :

0-600 feet below sea level. Chiefly fine sandstone and shale.

600-1,200 feet. Blue sandstone, schist breccia, some shale.

1,200-1,800 feet. Soft shale, with blue schist flakes.

1,800-2,500 feet. Bedrock, chiefly blue-green quartzose schist. 

.In San Pedro Hill, 5 miles northwest of Point Fermin, the schists in place are 

separated from the overlying shale by a few feet of fine schist breccia, which 

along the eastern edge of the schists becomes much thicker, and probably grade* 

out into shale, as at the point. The overlying shale contains blue sandstone 

beds and pockets, as well as numerous pumice fragments. The fossil evidence 

is inadequate for certain correlation of the San Pedro occurrences. * * * 

The fossils listed suggest a Lower Miocene age for at least a portion of the section. However, W. S. W. Kew, of the United States Geological Survey, who has 

studied the San Pedro region in detail, considers the beds below the Point Fermin breccia to be Upper Miocene and those above Pliocene, on the basis of theresemblance of the shales to those of the Upper Miocene and Pliocene, respectively, of the Santa Monica Mountains. Below the breccia, chert predominates, 

and Kew has never been able to find diatoms; above, soft diatomaceous shale 

predominates." [Described under center heading " Doubtful correlatives of the 

San Onofre facies."]

" San Pedro shales."

Eocene (?) : Western California (San Francisco region).

R. Crandall, 1907 (Am. Philos. Soc. Proc., vol. 46, pp. 3-58). Thin-bedded blackcoarse-grained hard shales, 4,000 feet thick, exposed in cliffs north and south 

of San Pedro Point. Included in Franciscan series. Rest on basal coarse 

conglomerate of the Franciscan and are overlain by crystalline limestone of tiie 

Calera Valley [Calera limestone member], which is also included in the 

Franciscan.
GEOLOGIC UNITS OF CALIFORNIA 75

The name is preoccupied in southern California. The rocks of the San 

Pedro Point southwest of San Francisco and in San Mateo County, and 

of adjacent areas, are mapped by A. C. Lawson (U. S. Geol. Survey 

Geol. Atlas, San Francieco folio, No. 193, 1914) as Martinez (?) 

formation.

San Ramon formation.

Oligocene (?): Western California (San Francisco Bay region).

B. L. Clark, 1918 (California Univ. Pub., Dept. Geology Bull., vol. 11, pp. 54-111). 

On the Sobraute anticline, in the Concord quadrangle, the formation consists 

for the most part of medium-flue gray sandstones, which at base are massive, 

rather coarse, and somewhat calcareous, but toward top are not so massive, 

thin beds of micaceous gray medium-fine sandstone alternating with thinner 

layers of sandy shale and clay shale, well exposed on side of road just south 

of divide between Bear and Pinole Creeks, on the north side of the anticline.' 

The formation is the basal formation of the San Lorenzo series in this region,, 

where it is overlain by the Kirker tuff and rests uncouformably on Tejon 

formation. The San Lorenzo series of San Ramon syncline, Mount Diabloregion, is considerably different from that of Sobrante anticline. Only one 

distinct formation was recognized in the Ramon syncline, and " this is called 

the San Ramon formation, the name already applied to the basal member 

of the San Lorenzo of the Sobrante anticline. It seems very probable that 

the San Ramon formation of this section represents a longer period of deposition than the San Ramon formation of the Sobrante anticline, but whether 

the time of the deposition of the Kirker tuffs and Concord formation [the twoupper formations of his San Lorenzo series in the Sobrante anticline] are 

represented in this record may be open to doubt." It rests unconformably 

on the Tejon formation.

W. P. Woodring, 1931 (Carnegie Inst. Washington Pub. 418, pp. 1-25). Fauna of 

San Ramon formation " looks suspiciously like Miocene."

Santa Ana.

Triassic: Southern California.

F. J. II. Merrill, 1914 (Geology and mineral resources of San Diego and Imperial 

Counties, p. 9, California State Min. Bur.). [Santa Ana is used in table as a 

" local " name for Triassic. Statement on page 10 indicates that it is intended 

to be applied to the same metamorphic rocks in Orange County (in which are 

the Santa Ana Mountains) as those to which the name Julian group is applied 

in adjoining San Diego County.]

Santa Ana limestone.

Triassic: Southern California (Orange County).

J. P. Smith, 1898 (Jour. Geology, vol. 6, pp. 779-780). Hard black siliceous limestone on west slope of Santa Ana Range, Orange County.

Santa Ana sandstone.

Probably upper Pliocene or lower Quaternary (mapped as Pliocene) :

Southern California (San Beruardino Mountains).

F. E. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 9, 

pp. 344, 378-379, map). Sandstone and shale formation, for most part of 

medium-gray color, although brown nnd reddish streaks are present. Also 

includes strata of coarse granitic detritus up to 5 and 6 feet thick, between 

which are finely laminated shales and occasional calcareous seams. Can not 

be correlated with much certainty with any other formation in district. May 

possibly have been formed at same time as Hathaway formation, of south 

side of range. Is unconformably overlain by Cabezon fanglomerate. The 

present position of the evenly bedded sandstone and shale in bottom of a 

deep canyon can only be explained by faulting.

Named for Santa Ana River, San Bernardino County, along which it is

exposed. 

17402 31 6
76 GEOLOGIC UNITS OF CALIFORNIA

.Santa Barbara beds (also marls).

Pliocene (upper) : Southern California (Santa Barbara County).

J.- P. Smith, 1912 (California Aicad. Sci. Proc., 4th ser., vol. 3, pp. 161-182). 

" The upper Pliocene is recorded under the name Santa Barbara, because it 

is by no means certain that the name Merced, which has been used for the 

upper Pliocene, is applicable in southern California."

J. P. Smith, 1915 (Nature and science on Pacific Coast, p. 51, San Francisco, Elder 

& Co.). [The name Santa Barbara 'beds is used in chart for uppermost Pliocene 

beds in the Coast Ranges, which are shown as younger than San Diego and 

Merced.]

 C. M. Carson, 1925 (Pan-Am. Geologist, vol. 43, pp. 2G5-270). Santa Barbara 

marls. Composed of evenly bedded soft brownish-yellow sandy bryozoan marls 

giving place above to fine soft sands. 'Thickness 1,000 feet. Probably rests 

unconformably on Miocene shales. Younger than Ventura sands and San Diego 

clays. The Santa Barbara formation represents the coldest part of the Pliocene 

epoch, immediately preceding the very cold early Pleistocene. It occurs at Santa 

Barbara and San Pedro.

Santa Clara formation.

Pliocene and Pleistocene: Western California (Santa Clara County).

J. G. Cooper, 1894 (California Acad. Sci. Proc., 2d ser., vol. 4, p. 171). " The Santa 

Clara lake beds. Fossil fresh-water shells have been found at several points on 

both sides of this valley and at different heights above it, but sufficient specimens 

have not yet been collected to determine the ages, elevations, disturbances, etc., 

of the various beds. The oldest known is that at San Jose" Mission, where a 

ridge apparently of Pliocene date remains as a remnant of a thick bed of gravel 

and alluvium once filling the greater part of the valley to a depth of probably 

300 feet above tides. The same deposit is seen at intervals from East Oakland 

along the foothills southward on the east side of the valley, and less abundantly 

on the west side to near Redwood City, but does not everywhere contain fossils. 

It is considerably disturbed in some places, usually by elevation of the mountains 

since its deposit." Fossils from San Jose' Mission listed.

J. C. Branner, J. F. Newsom, and R. Arnold, 1909 (U. S. Geol. Survey Geol. Atlas, 

Santa Cruz folio, No. 163). Santa Clara formation. Coarse gravel, sand, and 

sandy clay, locally lignitic, containing a fresh-water fauna. Thickness at least 

500 feet. Greater part is contemporaneous with Paso Robles formation. Rests, 

probably conformably, on Purisima formation. Overlain by Quaternary deposits. 

Recent alluvium resting unconformably on it in at least one place. Considered 

contemporaneous with Merced formation.

Appears to have been named for its considerable development in Santa 

Clara County.

. Santa Claran epoch.

Pleistocene: California.

0. H. Hershey, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 3, pp. 1-29). 

Santa Claran epoch (erosion). The epoch of erosion that initiated the Sierran 

period of Le Conte precedes Red Bluff epoch of deposition. " There is no portion of the State in which this epoch is so clearly defined as on the Upper 

Pliocene area of the Santa Clara River Valley of the south. Therefore I suggest 

for it the name Santa Claran as being eminently appropriate." (See under 

Sierran.)

;Santa Lucia granite. 

Santa Lucia quartz diorite.

Pre-Cretaceous: Southern California.

A. C. Lawson, 1893 (California Univ. Pub., Dept. Geology Bull., vol. 1, pp. 1-89). 

Santa Lucia granite, pre-Cretaceous, forms the main ridge of the Santa Lucia 

Range.

P. D. Trask, 1926 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 16, No. 6). 

Santa Lucia quartz diorite. The term Santa Lucia was first applied by Lawson 

(1893) to the porphyritic granite in the vicinity of Carmel Bay, but the porphyritic variety that he describes is only of local extent in Point Sur quadrangle. As 

it apparently grades into the main quartz diorite mass of the region and hence 

is probably a differentiate of the quartz diorite, the name Santa Lucia is retained 

for the entire plutonic mass.
V

GEOLOGIC UNITS OF CALIFORNIA 77

Santa Lucia series.

Pre-Franciscan (possibly pre-Cambrian) : Southern California (Monterey, 

San Benito, and San Luis Obispo Counties).

B. Willis, 1900 (Science, new ser., vol. 11, p. 221). Santa Lucia series, preFranciscan. Separated from Franciscan by erosion interval. [All there is 

about it.]

J. P. Smith, 1916 (California State Min. Bur. Bull. 72, pp. 9, 25-26). Santa Lucia 

formation. Schists, gneisses, and crystalline limestone of the Santa Lucia Range 

in Monterey and San Luis Obispo Counties, and Frernont's Peak of the Gavilan 

Range in San Benito County, have been named by Bailey Willis [above citation] 

the Santa Lucia series. The rocks have never been fully described, but a partial 

description is given by H. W. Fairbanks (California State Min. Bur. Rept. 12, 

pp. 493-526) without naming the series. No definite fossils known, but round 

crinoid stems arc said to have been found in the Gavilan limestones of Fremont's 

Peak. They are certainly pre-granitic, and the granite of the Santa Lucia 

Range is older than the Franciscan. The rocks are thoroughly metamorphosed 

and look as old as the pre-Cambrian rocks of southern California. Thickness 

and structural relations unknown, but the Franciscan rocks lie unconformably 

upon them in the few places where contacts have been observed.

 Same as Coast complex of Willis and Sur series of Trask.

Santa Margarita formation.

Miocene (upper) : Southern California (Santa Cruz Mountains and 

southward).

H. W. Fairbanks, 1904, (U. S. Geol. Survey Geol. Atlas, San Luis folio, No. 101). 

Santa Margarita formation. Alternating beds of conglomerate and soft sandstone, with several strata of diatomaceous earth and pumice. Thickness about 

1,500 feet. Occurs in northern part of the area, and considered to be contemporaneous with the Pismo formation of the southern part of the area, though 

the two formations are not known to have been connected. Unconformably underlies Paso Robles formation and unconformably overlies Monterey shale.

Named for exposures at Santa Margarita, San Luis Obispo County.

" Santa Maria " formation.

Pliocene and Pleistocene: Southern California (Santa Barbara County).

C. M. Carson, 1925 (Pan-Am. Geologist, vol. 43, pp. 265-270). In the Santa Maria 

district the Fernando formation is sometimes called the Santa Maria formation. 

It consists of a succession of shaly conglomerates, fine white and yellow sandstones, coarse gray sands, and thick beds of incoherent conglomerates having an 

aggregate thickness of not less than 3,000 feet according to Arnold and Anderson.

Santa Monica slate.

Triassic(?) : Southern California (Santa Monica Mountains).

H. W. Hoots, 1931 (U. S. Geol. Survey Prof. Paper 165, pp. 88-89). Santa Monica 

slate. Dark-gray and bluish-gray to black slate and phyllite, much of which 

has undergone contact and regional metamorphism and is locally altered to mica 

schist. Thickness 5,000 to 7,000 feet. Is of pre-Chico age. Assigned to 

Triassic(?) ; may be Jurassic or Paleozoic. Is intruded by Jurassic (?) granite 

and granodiorite. Named for occurrence in Santa Monica Mountains.

Santa Paula formation.

Lower Pliocene and Miocene?: Southern California (Ventura Basin).

J. E. Eaton, 1926 (Oil and Gas Jour., Nov. 11, 1926, p. 72; Oil Age, November, 1926, 

p. 16). Santa Paula formation. Previously unrecognized. Well-bedded sandstones, blue sandy and brown sticky shales and conglomerates, locally present in 

Los Angeles Basin. Northwest of Santa Paula 10,000 feet exposed ; absent south 

of Ventura Basin (on upthrowh side of Santa Clara River fault) from South 

Mountain to and including type locality of Pico formation. Best exposed on 

great monocline northwest of Santa Paula. The exposed Santa Paula sediments 

in Ventura Basin are Lower Pliocene in age, but base is not there exposed 

and is elsewhere indicated to be of Santa Margarita (Upper Miocene) .age. 

Basal formation of Fernando group. Underlies Pico formation and unconformably overlies Modelo formation.
78 GEOLOGIC UNITS OF CALIFORNIA

J. B. Eaton, 1929 (Am. Assoc. Petroleum Geologists Bull., vol. 13, No. 7, p. 755). 

Santa Paula formation. Consists of (1) heavy-bedded gray to blue arkosic sandstone, with lesser members of thin and medium-bedded sandstone and brown and; 

blue clay; locally conglomeratic; 7,500 feet; (2) calcareous sandstone and brown 

and blue sandy clay; locally conglomeratic; 1,750 feet. Of Middle and Lower 

Pliocene age. Underlies Pico formation and overlies Santa Margarita formation..

Santa Susana shale.

Eocene (middle) : Southern California (Ventura County).

B. L. Clark, 1924 (Pan-Pacific Sci. Cong., Australia, 1923, Proc., pp. 874-879).. 

Santa Susana formation. A formation only recently recognized and as yet differentiated only in region of Simi Valley, Ventura County. Richard Nelson, whohas completed a monograph on Martinez of Simi Valley, proposes to call it Santa 

Susana formation. The beds referable to it had previously been mapped as part 

of the Martinez. Consists very largely of shale and shaly sandstones with heavy 

conglomerates at base. Thickness 1,000 to 1,500 feet. Fauna entirely different 

from that of the underlying Martinez and has very little in common with that of 

the unconformably overlying Meganos group, although it is more closely related 

to M'eganos fauna than to Martinez fauna.

R. N. Nelson, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 11, 

p. 401, map). Santa Susana shale. Predominantly light-gray shale with some 

fine-grained sandstone and a lens of conglomerate at. the base toward its easterns 

end. Sporadic boulders of quartzite up to 6 inches in diameter have been found 

in both sandstone and shale. [Thickness not stated.] Grades into upper shale 

of underlying Martinez group and into overlying Domengine formation. Is of 

middle Eocene age. Occurs east of the main fault south of Simi Valley. Fauna 

includes several distinctive genera, such as Corbis and Velates, which are new to 

the Eocene of California. Other forms are closely related to those in the Meganos, 

but distinct from any known hi the Martinez. Named for its occurrence in 

proximity to town of Santa Susana.

San Timoteo beds.

Pliocene (upper) : Southern California (San Jacinto quadrangle, RiversideCounty).

C. Frick, 1921 (California Univ. Pub., Dept. Geology Bull., vol. 12, pp. 283-288). 

Great thickness of beds of late Pliocene age, coarser than the Eden beds, theupper division of the lower Pliocene in this region, and containing vertebrate' 

fossils which correlate in general way with the Blanco of Texas. Occur in San. 

Timoteo Canyon area.

Saragossa quartzite.

Probably Silurian or Devonian: Southern California (San Bernardino:

Mountains).

F. E. Vaughan, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 9; 

pp. 344, 352-363, map). At least 3,500 feet of rocks (upper limit unknown), 

consisting (in descending order) of

1. Very heavy-bedded saccharoidal quartzites containing occasional strata of 

schist.

2. Series of soft biotite and muscovite schists.

3. Saccharoidal quartzite, cross bedded.

4. Schists, 200 feet thick, rather thin bedded and varying from fine biotite 

schist to coarse gritty quartz-biotite schist; toward top free from dark 

constituents.

o. Quartzite pebble conglomerate. Several feet.

6. White and pink quartzite, so recrystalljzed as to have lost all semblance 

of original clastic structure, 120 feet.

7. Soft decomposed biotite schist, 50 feet. 

Is intruded by granites. Grades downward into Furnace limestone.

Named for Saragossa Spring, San Bernardino County, around which it is 

well developed.

" Sauer Dough."

A local sand bed, about 10 feet thick, in the Vaqueros sandstone of the 

Coalinga district. It is the uppermost sand in some wells along the 

western edge of sec. 22, T. 19 S., R. 15 E., and lies about 40 feet above 

the " Pulaski sand."
GEOLOGIC UNITS OF CALIFORNIA 79

Saugus formation.

Upper Pliocene and lower Pleistocene: Southern California (Los Angeles 

County).

0. EL Hershey, 1902 (Am. Geologist, vol. 29, pp. 349-372). Great series, 2,000 feet 

thick, of unlithifled sand, gravel, and clay, stratified, waterworn, and water 

deposited. Is an alluvial deposit, a river delta progressively sinking. Splendidly exposed in railway cuts in Soledad Canyon near Snugus, Los Angeles 

County. Conformably overlies Soledad division.

W. S. W. .Kew, 1923 (Am. Assoc. Petroleum Geologists Bull., vol. 7, pp. 411-420) 

and 1924 (U. S. Geol. Survey Bull. 753, p. 81). The Saugus formation was 

first recognized by Hershey as the " Saugus division of the upper Pliocene 

series." In previous reports the Saugus deposits have been included in the 

Fernando formation, of which they constitute the upper unconformable part. 

In this report the Saugus deposits are treated as a distinct formation and the 

Fernando is made a group. In most places the Saugus formation rests unconformably on the Pico, the lower formation of the Fernando group, and is 

unconformably overlain by Pleistocene terrace deposits.

The typical Saugus deposits are nonmarine, but to the west contemporaneous 

marine beds are included in the formation.

Sausalito chert.

Jurassic (?) : Western California (San Francisco region).

R. Arnold, 1902 (Science, new ser., vol. 15, table on p. 416). Sausalito cherts, 

radiolarian, 900 feet thick. [Shown in table as underlying Marin sandstone 

and overlying Bolinas sandstone.] A subdivision of the Franciscan.

A. C. Lawsoii, 1903 (Geol. Soc. America Bull., vol. 13, table on pp. 544-545). 

[Same as above.]

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Radiolarian chert, prevailingly dull brownish red, especially in thicker and 

more evenly bedded portions, but includes some rock of yellow, green, and 

other colors, interbedded with thousands of thin layers of shale. Underlies 

Mariu sandstone and overlies Cahil sandstone. Included in Franciscan group.

Named for exposures west of town of Sausalito, on Marin Peninsula, Marin

County.

Sentinel dolomite.

Lower Paleozoic (?) : Southeastern California (Inyo County). 

See tinder Telescope group. Derivation of name not stated.

Sentinel granodiorite.

Probably Cretaceous: Yosemite National Park.

P. C. Calkins, 1930 (U. S. Geol. Survey Prof. Paper 160, p. 125, map). Is less 

uniform in composition than most of the other intrusive bodies. In western 

part of the zone crossed by Yosemite Valley the rock is relatively light-colored 

and homogeneous, but in the eastern part of the valley it is darker and more 

streaky and contains many dark inclusions. Constitutes greater part of both 

walls of Yosemite Valley from the Three Brothers nearly to the Royal Arches 

and from the Fissures eastward to Glacier Point. Is oldest known formation 

of Tuolumne intrusive series. Next older than Half Dome quartz monzonite, 

and generally contains more biotite and hornblende than the Half Dome.

Named from fact that it composes Sentinel Rock, Yosemite National Park.

Sespe formation.

Oligoceue and lower Miocene (?) : Southern California (Ventura County).

W. L. Watts, 1897 (California State Min. Bur. Bull. 11, pp. 22-38). Sespe Irowristohe formation. Consists of sandstone, shales, and conglomerate, all more or 

loss brown. Is widely exposed in Sespe district. Underlain, with apparent 

conformity, by white sandstone, and overlain, also with apparent conformity, 

by drab sandstone. Is of Tertiary age, and younger than rocks containing 

Eocene fossils and older than beds containing Miocene fossils.

W. S. W. Kew, 1924 (U. S. 'Geol. Survey Bull. 753). Sespe formation. Nonmarine 

red, brown, and yellow conglomerate and sandstone with interbedded shale. 

Corresponds to the Sespe brownstone formation of Watts. Thickness 3,500 feet
80 GEOLOGIC UNITS OF CALIFORNIA

at type locality on Sespe Creek, in the northwest part of the Camulos quadrangle. Ranges up to 4,000 feet or more. Conformably underlies the marine 

Vaqueros formation (with true Vaqueros Turritellu inezana fauna), and 

unconformably overlies the marine Tejon formation. The top 500 feet of the 

Tejon consists of light-gray sandstone with some shale and corresponds to the 

" white sandstone " of Watts. The Vaqueros corresponds to the " drab sandstone " of Watts. The typical Sespe corresponds to the middle member only 

of the Sespe formation of G. H. Eldridge and R. Arnold, as mapped and described 

in United States Geological Survey Bull. 309, 1907.

The Sespe formation and the overlying and underlying formations are 

exposed in the gorge of Sespe Creek near the entrance of Tar Creek and 

In the region that extends eastward between the waters of Tar and 

Little Sesce Creeks.

Sbasta series.

Lower Cretaceous: California and Oregon.

W. M. Gabb, 1869 (California Geol. Survey, Paleontology, vol. 2, pp. vii, xiv, 129, 

133).

A provincial series: term applied to the lower part of the marine Cretaceous 

rocks as developed on the Pacific coast. These rocks are now divided 

into the Horsetown formation above and the Knoxville formation below 

and are unconformably overlain by the Chico formation and unconformably underlain by the Franciscan formation.

Named for development of the rocks in Shasta County.

" Shasta-Chico series."

Lower and Upper Cretaceous: California and Oregon.

J. S. Diller, 1893 (Geol. Soc. America Bull., vol. 4, pp. 205-224). "An essentially 

conformable and continuous series of sediments formed without a distinct 

interruption. For this scries Mr. [T. W.] Stanton and I have agreed to use 

the name Shasta-Chico series." Includes Chico, Horsetown, and Knoxville 

formations, or all of the known Cretaceous of California.

Shastan. See Shasta series.

Shoofly formation.

Mississippian: Northern California (Taylorsville region).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Shoo Fly teds. 

Thickness 8,600 feet. Contain a limestone which crops out on Clear Creek, 

about 2 miles southeast of Shoo Fly Bridge.

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Shoo Fly formation. Mainly clay 

slates above and quartzite below. The slates are light to dark gray, generally 

dull, but sometimes silky and in places slightly micaceous, and contain occasional films of gray or black flinty material as well as thin beds of sandstone 

and fine conglomerate of quartz pebbles. Here and there are traces of beds 

composed exclusively of volcanic fragments, some of which are clearly vesicular. 

Near middle are limestone lentils, some over 50 feet thick. The quartzites that 

prevail in the upper part are thin bedded, somewhat slaty, and indistinctly 

schistose, with micaceous partings. Thickness 6,800± feet. Everywhere separated from the underlying Arlington formation by the Taylor meta-andesite. 

Is older than the Peale formation, but relations not determined.

Named for exposures in road between Shoo Fly Bridge and Spanish Creek, 

Taylorsville region.

" Siebert" formation.

Miocene (upper) : Southern Nevada.

S. H. Ball, 1907 (U. S. Geol. Survey Bull. 308, pp. 27, 32-34, map). Sirtert lake 

beds. Thick masses of sediments occur in the majority of the ranges of the 

area [southwestern Nevada and Inyo County, eastern California], and on lithologic and stratigraphic grounds are correlated with the Siebert, lake beds, of Mio-
GEOLOGIC UNITS OF CALIFORNIA 81

cone age, at Tono-pah, described by Spurr. These tuffaceous sandstones and 

conglomerates, largely composed of rliyolitic material, reach an observed maximum (in Amargosa Range) of 1,150 feet. Are unconformably underlain by 

rhyolite and unconformably overlain by rhyolite. In southern Klondike Hills 

and the Silver Peak Eange the Siebert lake beds are interbedded, without erosional unconformity, with rhyolites and siliceous latites and dacites. [As abovedefined and mapped Ball's Siebert lake beds include the Fraction rhyolite breccia,, 

which is not a part of the Siebert tuff of Spurr.]

The Siebert formation of F. L. Ransome (U. S. Geol. Survey Bull. 303, 1907,. 

and Prof. Paper 66, 1900) in the Goldfield district, Nev., also included' 

the Fraction rhyolite breccia! and is therefore a larger unit than the 

Siebert tuff as originally defined by Spurr. Siebert in this broad sense 

has been abandoned by the United States Geological Survey, being the 

same as the older name, Esmeralda formation.

Sierra Blanca limestone.

Eocene (upper) : Southern California (southern part of Santa Ynez quadrangle, Santa Barbara County).

R. N. Nelson, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 10,. 

pp. 350, 352-354, pi. 46, map). Remarkably pure massive, almost white foraminiferal limestone, its upper 10 or 15 feet grading into medium to fairly 

coarse grained gray sandstone interbedded with gray shales. Thickness 0 to 

200 feet. In Indian Canyon it is 200 feet thick. Decreases in thickness tothe east and disappears a little over a mile west of Mono Creek. Rests conformably on Mono shale. On south side of San Rafael Mountains it is overlain by 25 feet of massive maroon-gray to gray shale of Eocene age. It is alsounconformably overlain by Miocene strata. Is conspicuously exposed on south, 

side of Sierra Blanca Mountain, 1% miles southwest of Loma Pelona.

Sierran.

Pliocene and Quaternary: Time term.

J. Le Conte, 1899 (Jour. Geology, vol. 7, pp. 525-544). Name proposed to replace1 

Ozarkian (preoccupied), applied to "a time of general uplift and erosion, longer 

than both the Glacial and the Champlain put together. * * * In eastern 

part of continent the Ozarkian grades into the Tertiary. In Sierra Nevada it 

is sharp'ly marked off from the Tertiary. That it belongs to the Quaternary is 

certain."

0. H. Hershey, 1902 (Am. Geologist, vol. 29, pp. 88-95). "The term Sierran is not 

the equivalent and can not properly replace the term Ozarkian. As I understand Le Conte, Sierran is derived from the canons of the Sierra Nevada region 

and its definition may be given as the designation of that period during which 

these canons we're in process of formation. * * * Under Le Conte's definition Sierran apparently covers at least part of the Ozarkian or preglacial portion of the Pleistocene, and nearly the whole of the Glacial period as the latter 

has been established in the Eastern States and Europe. * * * I have 

avoided applying the term Ozarkian in California because, the Glacial period 

being so very imperfectly represented here, I could not distinguish the work of 

the Ozarkian from that of later time."

0. H. Hershey, 1902 (California Univ. Pub., Dept. Geology Bull., vol 3, pp. 1-29). 

Divides Le Conte's Sierran period into (descending order) :

Erosion epoch not named.

San Pedran epoch (deposition). "May be approximately equivalent to 

lowan."

Los Angelan epoch (erosion).

Red Bluffi epoch (deposition).

Santa Claran epoch (erosion).

J. P. Smith, 1910 (Jour. Geology, vol. 18, No. 3, p. 227), divided. Quaternary of California into (descending order) Terrace epoch, Champlain epoch, and Sierran 

epoch (including Glacial and pre-Glacial).

J. E. Eaton, 1928 (Am. Assoc. Petroleum Geologists Bull., vol. 12, p. 119), divided 

the Pleistocene of California into (descending order) Champlain, Glacial, Sierran, 

and Pedroian.
82 GEOLOGIC UNITS OF CALIFOKNIA

Siesta formation.

Pliocene: Western California (San Francisco region).

A. C. Lawson and .C. Palache, 1902 (California Univ. Pub., Dept. Geology Bull., 

vol. 2, pp. 384-390, map). Siestan formation. Fresh-water conglomerates, 

sandstones, and shales, with lignites, clays, limestone, chert, and tuff. Included 

in Upper Berkeleyan. Overlies in places Grizzly Peak andesite and underlies 

in places a fresh-water limestone member of the Upper Berkeleyan.

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Siesta formation. Lake beds. [Same lithology as above.] Thickness 200 

feet. Underlies Bald Peak basalt and overlies Moraga formation. Middle 

formation of Berkeley group.

Named for development in Siesta Valley, Berkeley Hills. 

'" Siestan " formation. See Siesta formation.

Silver Peak group.

Lower Cambrian: Southern Nevada and Inyo County, Calif.

H. W. Turner, 1902 (Am. Geologist, vol. 29, pp. 261-272). Silver Peak formation. 

Lower Cambrian rocks consisting, in the mountains north of Clayton Valley, 

Esmeralda County, Nev., in ascending order, of (1) massive dolomite, (2) 

massive green quartzite, (3) knotted schists, (4) ArcheocyatJws limestone and 

green Olenellus slate with dark limestone and some quartzite and thin-bedded 

slate near the top of the series. Also exposed in Silver Peak Range, Esmeralda 

County, Nev. Unconformably overlain by Upper Cambrian rocks designated 

as Emigrant formation. Rests on Algonkian rocks. According to C. D. 

Walcott's division line between Cambrian and Algonkian, items 1, 2, and 3 

of the section north of Clayton Valley would belong to the Algonkian, but 

they are here included in the Lower Cambrian. Thickness not given.

The Silver Peak deposits are regarded as divisible into two or more formations and hence have been called Silver Peak group and Silver 

Peak " series." They have been identified, with a thickness of 7,000 

feet, by E. Kirk (U. S. Geol. Survey Prof. Paper 110, pp. 28-30, 1918) 

in the Inyo Range, Calif. C. D. Walcott also identified them in the 

Inyo Range in 1908.

 'Silver Terrace" sandstone.

Jurassic (?): Western California (San Francisco).

R. Crandall, 1907 (Am. Philos. Soc. Proc., vol. 46, pp. 3-58). Sandstones, with 

some shales, tuffs, and lignites. Thickness 500 feet. Forms the Silver Terrace 

Hills, in the eastern part of the city of San Francisco. Is older than the 

Telegraph Hill sandstone. In places is overlain by the upper jasper bed. 

Is a part of the Franciscan.

A. C. Lawson (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193, 1914) 

mapped this sandstone as Marin sandstone.

Simi conglomerate.

Eocene (lower) : Southern California (Ventura County).

R. N. Nelson, 1925 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 15, No. 11, 

pp. 400-401, map). A very persistent conglomerate of well-rounded pebbles 

and boulders of all sizes up to 1 foot in diameter, in a matrix of coarse-grained 

arkosic sandstone. Occasionally, especially near top, there are lenticular beds 

of sandstone varying in thickness from 6 inches to several feet. The pebbles 

are chiefly quartzite, but granite and rhyolite pebbles are abundant, and the 

formation also contains pebbles of diorite, sandstone, gneiss, and schist. 

Thickness few feet to SOO feet on west side of the faults south of Siml 

Valley, with a maximum of about 1,500 feet east of the main fault. Is the 

basal formation of Martlnez group (lower Eocene). Rests unconformably on 

Chico formation. Grades vertically and laterally into the overlying Las 

Virgenes sandstone. Named for occurrence on the flanks of Simi Hills, 

Ventura County.
GEOLOGIC UNITS OF CALIFORNIA 83

Sobrantc sandstone.

Miocene (lower) : Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Sandstone, somewhat variable in character, but prevailingly fine grained and 

light colored, though it shows local ferruginous staining. Some beds are gritty 

and some flaggy. Near base a bed of volcanic ash that ranges in thickness from, 

a few inches to 20 or more feet. Is basal formation of Monterey group. 

Thickness 400 feet. Underlies Claremont shale and unconformably overliesTejon formation. Named-for exposures on Sobrante Ridge, Contra Costa County.

In 1918 (California Univ. Pub., Dept. Geology Bull., vol. 11, No. 2, pp. 54-111) 

B. L. Clark proposed to restrict the name Sobrante sandstone to the upper 80 to100 feet of Lawson's Sobrante sandstone, or to the beds containing the Area 

montereyana fauna, and to transfer the lower (and unconformable) part to the 

San Lorenzo (Oligocene) or Affasoma gravidum zone.

" Soledad division."

Miocene (upper) : Southern California (Los Angeles County).

0. H. Hershey, 1902 (Am. Geologist, vol. 29, pp. 349-372). Gravel and sand, chiefly

granitic, with lava pebbles and cobbles less abundant than in the Lang division,

and finer and more evenly bedded. Supposed to be marine. Thickness 3,000"

feet. Conformably underlies Saugus division and conformably overlies Lang

. division.

W. S. W. Kew, 1924 (U. S. Geol. Survey Bull. 753, p. 81). The "Soledad division" 

of Hershey is now thought by the writer to be equivalent, in greater part at 

least, to the upper part of the Mint Canyon formation (upper Miocene) of thisreport.

Named for exposures in Soledad Canyon, near Saugus, Los Angeles County.

Soledad group.

Miocene (lower) or Oligocene: Southern California (Los Angeles County).

D. S. Jordan, 1919 (Leland Stanford Junior Univ. Pub., Univ. ser., Fossil fishes of 

southern California, pp. 3-5). Soledad group. Sandstones and shales; the sandstones of pale yellow color, also soft white sandstones and rather fine white 

shuly sandstone. Considerably older than the diatomaceous deposits referred to 

Monterey, which arc sometimes segregated under the name Puente. The fish 

fauna is older than Monterey and of lowest Miocene or possibly of Oligocene 

age. Well developed about Soledad Pass, in the extreme northern part of LosAngeles County, about 40 miles north of Los Angeles.

Sonoma group.

Pliocene: Northern California (north of San Francisco Bay region).

R. B. Dickerson, 1922 (California Acad. Sci. Proc., 4th ser., vol. 11, No. 19, maps).. 

Basalts, andesites, rhyolites, tuff breccia, fine-grained tuff, and other agglomerates. Generalized section running north from Adobe Fort to Petaluina Reservoir 

shows following sequence, in descending order: Basalt, tuff, basalt, conglomerate, 

basalt, NeoMpparion gidleyi beds, and tuff, resting uncouformably on Petaluma 

formation. Includes the Sonoma tuff, Mark West andesite, and St. Helena 

rhyolite of Osmont. Is overlain by MUlerton formation. In Pinole synclinc is 

known as Pinole tuff. The tuffaceous facies of Sonoma group are represented 

as. interbedded tuff members of marine Merced group.

Named for typical exposures on western flanks of Sonoma Mountains, 

Sonoma County.

Sonoina tuff.

Pliocene: Northern California (Sonoma County).

V. C. Osmont, 1904 (California Univ. Pub., Dept. Geology Bull., vol. 4, pp. 39-87). 

Sonoma tuff. Andesitic in character and interbedded with thin flows of basalt, 

and with sandstones and volcanic conglomerates, to the west, where it is of 

fluviatile origin. To east interbedded with volcanic agglomerates and breccias 

and largely of eolian origin. Rests conformably on Mark West andesite. 

Thickness 1,700 feet.

Probably named for exposures in Sonoma Mountains, Sonoma County.
 84 GEOLOGIC UNITS OF CALIFORNIA

Sour Dough limestone.

Lower Paleozoic (?) : Southeastern California (Inyo County). 

See under Telescope group. Exposed in Sour Dough Canyon.

'" Spanish formation."

Mississippian: Northern California (Lassen Peak region).

J. S. Diller, 1892 (preliminary proof-sheet edition of Lassen Peak folio, No. 15, of 

U. S. Geol. Survey Geol. Atlas). Chiefly quartzites and slates Avith occasional 

lenses of limestone. Has yielded no fossils. Is younger than Caribou formation 

and older than Arlington formation. Named from fact it surrounds the northern 

end of Spanish Peak.

In the published Lassen Peak folio (No. 15) these rocks are mapped and 

described as Calaveras formation.

 ' Staran series."

Triassic (Upper?) : Humboldt County, Nev.

C. [R.] Keyes, 1923 (Pan-Am. Geologist, vol. 40, pp. 52, 59). " The great Star Peak 

limestone, or Staran series, of the Humboldt Mountains, reported to he more 

than 5,000 feet in thickness." [Thickness assigned by Keyes 3,000 feet.] Unconformably below Jurassic Lovelockian series and above Koipatoan series. Of 

late Triassic age.

Named for exposures in Star Peak Mountain, Humboldt County, Nev.

 " Stewartsville group."

Eocene: Western California.

B. L. Clark, 1918 (Geol. Soc. America Bull., vol. 29, p. 94).

Synonym of Meganos printed through inadvertence.

Stonewall quartz diorite.

Jurassic (" post-Triassic and pre-Cretaceous ") : Southern California (Cuyaniaca region, San Diego County).

F. S. Hudson, 1922 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 13, No. 6, pp. 

181, 191-193, map). Named after Stonewall Peak, which is composed of this 

rock, which is intrusive into Julian schist.

<( Suisun marble."

Age unknown: Western California (Solano County).

J. D. Whitney, 1865 (California Geol. Survey, vol. 1, p. 104). North of Suisun commences another .series of hills, which has received the name of the " Pelevo 

Hills," at their southeastern end, but which extend northwest and become 

merged in the chain known as the " Vacca Mountains," which is the name given 

to the ridges here bounding the Sacramento Valley on the western side. The 

Pelevo Hills are made up of Cretaceous strata. The well-known " Suisun marble " occurs in these sandstones and is evidently a deposit from calcareous 

springs. It is a deep brownish-yellow color with a banded structure.

A local deposit of travertine of unknown age.

" Superjacent series."

A descriptive term used in folios and other early reports on the Gold Belt 

region of northern California, to include the Cretaceous, Tertiary, and 

Quaternary deposits, in contradistinction to the " Bedrock series," a 

term applied to the underlying Jurassic, Triassic, and Carboniferous 

formations.

Sur series.

Pre-Franciscan (possibly pre-Cambrian) : Southern California (Southern 

Coast Ranges).

P. D. Trask, 1926 (California Univ. Pub., Dept. Geology Bull., vol. 16, No. 6). Sur 

series. The term Santa Lucia series was first applied to the crystalline complex 

of the Santa Lucia Range by J. P. Smith in 1909 (Science, new ser., vol. 30, 

p. 347). [Name used but not defined in publication cited.] The name
GEOLOGIC UNITS OF CALIFORNIA 85

»

Santa Lucia, however, had been previously applied by Lawson (1893) to the 

granite at the north end of Santa Lucia Range. It is very evident that the

^ crystalline schists comprise a sedimentary series deposited prior to the intrusion 

of the quartz diorite. At present both a series of sediments and the granite

J which intrudes them bear the same name. A new name should be applied to the 

schists, since, by priority, the name Santa Lucia should be given to the granite 

and quartz diorite. The name Sur series is proposed as a comprehensive name 

for the schist series of the southern Coast Ranges, which is particularly well

3 developed along Sur River. Age unknown. No fossils have yet been found in

J this series. It is intruded by the Santa Lucia quartz diorite, of pre-Chico age. 

It consists chiefly of sedimentary rocks now metamorphosed into quartzites, 

marbles, mica schists, paragneisses, and in part Into injection gneiss. It Includes the crystalline limestones that have been named Gabilan limestone.

Surprise formation.

Lower Paleozoic (?) : Southeastern California (Inyo County).

F. MacMurphy, 1930 (Econ. Geology, vol. 25, pp. 309-311, map). Surprise formation. A series of predominantly fine-textured flaggy or slaty rocks which occupy

* an irregular strip of country on west side of Panamint Range. Prevailing rock 

types are conglomerate schist, actinolite schist, ottrelite schr'st, quartz-sericite

^ schist, slate, phyllite, quart-biotite-tonrmaline schist, metamorphosed sandstones, 

and grits, and a few beds of brown limestone, and there exist all gradations and 

combinations of these rocks. Though bedding is not often seen, it is frequently 

suggested, and there can be no doubt as to sedimentary origin. Overlies Marvel 

dolomitic limestone, usually with gradation from a true limestone to a true schist 

for a distance of from 5 to 30 feet. Underlies Sour Dough dolomitic limestone 

with nonconformity. Exposed along Surprise Canyon. .

Slitter formation.

^ Eocene (?) : Northern California (Marysville Buttes region, Sutter County). 

R. E. Dickerson, 1916 (California Univ. Pub., Dept. Geology Bull., vol. 9, pp. 404- 

406). Chiefly rhyolitic ash, rhyolitic tuff breccia, thin flows of rhyolite, and 

conglomerate containing rhyolitic and quartz pebbles. Thickness 500 to 600 

feet. Rests with marked unconformity on Chico and on Tejon. Is overlain unconformably by lava flows and mud flows that consist of andesitic material. Included in upper part of lone formation as mapped in Marysville folio of United 

States Geological Survey, which also included Tejon and Chico rocks. Named 

for occurrence in Sutter County, in what is now known as the Marysville Buttes 

(formerly Sutter Buttes).

Howel Williams, 1929 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 18, pp. 112, 

129+)- Sutter formation. Predominantly washed rhyolite tuffs below and 

andesite tuffs above, admixed with sands, clays, and gravels. Thickness 500 to 

1,000+ feet. Overlies Butte gravels and is overlain, with erosion unconformity, 

by intrusive andesite porphyry. Assigned to Miocene and Pliocene(?). " Dickerson's original description of Sutter beds calls for drastic revision. Essentially 

the Sutter formation is the detrital equivalent of the Tertiary rhyolitic and 

andesitic deposits of the Sierra Nevada, admixed with sediments that are the

*' equivalents in age of the six auriferous gravels of tb/e intervolcanic period of

x the Sierra. Although the Sierra was unquestionably the chief source of the

Sutter beds, it is likely that part of the sediments was also derived from the

Coast Ranges. * * * Its volcanic materials appear to be entirely pyroclastic

and free from lava flows, and there is nothing in the formation to suggest a

derivation from local vents, as Dickerson has supposed. * * * The most

notable and persistent feature of the Sutter formation is the regularity and

prominence of its banding." Most complete and typical section is along West

> Butte Pass, adjacent to road bridge that lies due south of South Butte.

l Swearinger slate.

Upper Triassic: Northern California (Taylorsville region).

J. S. Dillcr, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Dark calcareous 

slates with thin blue limestones and some siliceous layers. Thickness 200 feet, 

Includes Halobia bed, RhaMoceras bed, and Monotis bed [zone of Ps&udomonotis

* subcircularls]. Rests directly and unconformably on the Carboniferous Robinson 

formation. Believed to underlie Hosselkus limestone.
86 GEOLOGIC UNITS OF CALIFORNIA

J. S. Diller, 1908 (TJ. S. Geol. Survey Bull. 353). Chiefly dark slaty shale, sometimes 

more or less calcareous and at other times decidedly siliceous, but the thin beds 

of limestone or chert form only a small proportion of the whole mass. In the 

side of the slate adjoining the Hosselkus limestone thin lenticular beds of limestone become more abundant. They are generally dark, with irregular cherty or 

sandy layers, and are fossiliferous. Thickness 200 feet. Is underlain (not overlain, as originally supposed) by Hosselkus limestone, with which it is conformable, but in places it rests on the older Robinson formation. Is overlapped by 

Trail formation. [Is approximate equivalent of Brock shale.]

Named for fact that it occurs just above Swearinger's house, on north side 

of Genesee Valley, Plumas County.

Taft granite.

Probably Cretaceous: Yosemite National Park.

F. C. Calkins, 1930 (U. S. Geol. Survey Prof. Paper 160, p. 122, map). Nonporphyritic hiotite granite, of even, medium-coarse grain. Consists chiefly of white 

feldspar and smoky-gray quartz in grains mostly about 5 millimeters in diameter. 

Is younger than El Capitan granite.

Named from fact that it composes Taft Point, Yosemite National Park.

Tamarack formation.

Term applied by O. H. Hershey (Am. Geologist, vol. 27, p. 226, 1901) to the 

gabbro in the Klamath Mountain region of northern California.

Tank volcanics.

Quaternary (?) : Southern California (Kern County).

A. C. Lawson, 1906 (California Univ. Pub., Dept. Geology Bull., vol. 4, pp. 431-462). 

Andesitic lava flows and tuffs, best exposed in vicinity of the railway tank 2 miles 

below Tehachapi station, on Tehachapi Creek. Older than Cable formation and 

younger than Atlas formation.

"Tassajara lake(?) bed." [U. S. Geographic Board has adopted spelling

Tassajero.] 

Pliocene (probably) : Western California (Alameda County).

J. G. Cooper, 1894 (California Acad. Sci. Proc., 2d ser., vol. 4, p. 170). Tassajara 

lake(?) bed. Along a small branch of Walnut Creek, in Alameda County, north 

of Livermore, is a deposit which contains chiefly living species and was formerly called Quaternary, but one extinct species has been described from there, 

and its high elevation, nearly corresponding with the Contra Costa lake bed, 

makes it probable that it may better be called Pliocene. [Fossils listed.]

Probably named for exposures on Tassajero Creek, Alameda and Contra 

Costa Counties.

Taylor meta-andesite.

Mississippian: Northern California (Taylorsville region).

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Green, in places slaty metaandesite, more than 1,000 feet thick. Occurs as lava flows, tuffs, and volcanic 

conglomerate. Conformably overlies Arlington formation and conformably underlies Shoofly formation.

Named for exposures around Taylor Rock.

Taylorsville formation.

Devonian: Northern California (Taylorsville region).

 T. K. Diller, 1892 (Geol. Soc.. America Bull., vol. 3, pp. 370-394). Taylor[s]villt> 

slates, 1,800 feet thick. Older than Arlington beds and younger than Montgomery limestone.

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Taylorsville formation. Chiefly 

slates and thin-bedded sandstones, among which there are numerous small 

layers of fine black chert or occasional less regular masses of red chert, but 

at base there is locally a fine greenish-gray conglomerate with indistinct pebbles, 

and near middle well-defined beds of light-colored quartzite. Thickness 1,800
GEOLOGIC UNITS OF CALIFORNIA 87

feet. Rests with probable unconformity on Montgomery limestone. Is older 

than Arlington formation, from which it is separated by granite. Fossils not 

distinctive, but formation is believed to be Devonian.

Named for exposures on eastern face- of the spur above the limestone about 

a mile south of Taylorsville, Plumas County.

Taylorville slates. See Taylorsville formation. 

Tecuja beds. See Tecuya beds.

Tecuya beds.

Miocene (lower) : Southern California (San Joaquin Valley).

C. Stock, 1920 (California Univ. Pub., Dept. Geology Bull., vol. 12, No. 4). Tecuja 

beds. Landlaid beds in which red sandstones and shales are most striking 

lithologic members, but lavas and tuffs are also present. Rests unconformably 

on Tejon formation in the immediate vicinity of Tecuja [Tecuya] Canyon, in 

the lower part of the San Joaquin Valley, and is overlain, without evidence 

of unconformity, by Monterey marine deposits presumably with a Vaqueros 

fauna. The beds may be contemporaneous with a part of the Sespe formation 

or may belong to Monterey series.

B. L. Clark, 1921 (Jour. Geology, vol. 29, pp. 586-C14; and First Pan-Paciflc Sci. 

Conference Proc., pt. 3, pp. 801-818). The Tecuja "beds are continental deposits 

intercalated in the marine Vaqueros group, and it seems to the writer that they 

are of lower Miocene age, rather than upper Oligocene.

Tehachapi marble.

Southern California (Kern County).

H. G. Hanks, 1886 (California State Min. Bur. Sixth Ann. Kept., pt. 1, p. 23). A 

large deposit of yellow brecciated marble half a mile from the town of 

Tehachapi, Kern County, on the road to Caliente, also 9 miles west of 

Tehachapi, in Brlght's Valley.

Tehachapi formation.

Quaternary (?) : Southern California (Kern County).

A. C. Lawson, 1906 (California Univ. Pub., Dept. Geology Bull., vol. 4, pp. 431-462). 

A great body of postlacustrine coarse alluvium in fresh undecomposed condition, only slightly cemented. Thickness 250 feet. Younger than Cable 

formation.

Probably named for occurrence near town of Tehachapi and in Tehachapi 

Creek Valley.

Tejon formation.

Eocene (upper) : Western California.

W. M. Gabb, 1869 (California Geol. Survey, Paleontology, vol. 2, p. xiii, as reported 

by J. D. Whitney from an unpublished paper by Gabb, and footnote by Gabb 

on p. 129). Division B of the Cretaceous of previous California reports is 

here named the Tejon group, from the localify where it is most strongly 

developed. This division of the Cretaceous is peculiar to California. Is found 

most extensively developed in vicinity of Fort Tejon and about Martinez. From 

latter locality it forms an almost continuous belt in the Coast Ranges to 

Marsh's, 15 miles east of Monte Diablo, where it sinks under San Joaquin 

plain. It was also discovered at various points in eastern face of same range 

as far south as New Idria, and in summer of 1866 by Mr. Gabb, in Alendocino 

County, near Round Valley, the latter locality being the most northern point 

at which it is as yet known. Is the only coal-producing formation in California. 

Contains a large and highly characteristic series of fossils, the larger part 

peculiar to itself, while a considerable percentage is found extending below into 

the next [Martinez] group, and several species still further clown into the Chico 

group. [On p. 147 Gabb mentions " beds intermediate between Tejon group 

and Martinez group west of town of Martinez," but no such beds are mentioned 

in connection with the definitions of Tejon or Martinez. 1
88 GEOLOGIC UNITS OF CALIFOBNIA

In 1918 (Geol. Soc. America Bull., vol. 29, pp. 94, 281) the name Tejon 

formation was restricted by B. L. Clark to the upper part of the Tejon 

of previous usage, or to the beds containing a " typical Tejon fauna," 

the unconformably underlying beds being named Meganos " group." 

The United States Geological Survey uses this restricted definition of 

Tejon formation. The Eocene age of the Tejon formation lias long 

been recognized.

Named for occurrence in vicinity of Fort Tejon, Kern County.

" Telegraph Hill" sandstone.

Jurassic (?) : Western California (San Francisco).

K. Crandall, 1907 (Am. Philos. Soc. Proc., vol. 46, pp. 3-58). Sandstones and shale* 

very similar to the older San Bruno sandstone of the Franciscan. Thickness 

800 to 1,000 feet. Is topmost formation of Franciscan or Golden Gate series. 

At the Potrero the formation rests on the jaspers of the Franciscan, which 

overlie the San Bruno sandstone. Named for exposures at Telegraph Hill, San. 

Francisco.

A. C. Lawson (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193,. 

1914) mapped this sandstone as Marin sandstone.

Telescope group.

Lower Paleozoic (?) : Southeastern California (Inyo County).

F. MacMurphy, 1930 (Econ. Geology, vol. 25, p. 311 and map). Telescope group. 

Consists of seven mapped units (in descending order) Eedlands dolomitic 

limestone, Radcliff formation, Sentinel dolomite, Wildrose formation, Mountain 

Girl conglomerate quartzite, Middle Park formation, and Sour Dough dolomitic 

limestone. The Mountain Girl conglomerate quartzite overlies Middle Park. 

formation with disconformity (?), and the Sour Dough limestone nonconformably 

overlies Surprise formation. The names of these formations are derived from 

geographic terms used in this part of Panarnint Range. The rocks have nearly 

all been metamorphosed to some degree. In absence of diagnostic paleontologicevidence the age of all formations is open to question. Tentative assignment to 

Lower Paleozoic has been made largely on lithologic grounds. The rocks areundeformed.

Temblor formation.

Miocene (middle) : Southern California (Kern County).

F. M. Anderson, 1905 (California Acad. Sci. Proc., 3d ser., vol. 2, pp. 168-187).. 

Temblor beds. The entire series of Miocene sands and shales below the Monterey 

shales in the Mount Diablo Range. Thickness 1,500 feet. Include (descending 

order) :

" Button beds," 100 feet (sandy beds characterized by great numbers of" 

small discoidal sea urchins, Astrodapsis).

Siliceous and clay shales with interstratifled sandstone, 600 feet.

Sandstones with numerous fossil species, 800 feet.

Rest unconformably on Dornijean sands. In some places there is a distinct 

overlapping of the Monterey shales beyond the borders of the Temblor beds. 

[Fossils listed.]

F. M. Anderson, 1908 (California Acad. Sci. Proc., 4th ser., vol. 3, pp. 1-40). 

Temblor beds. Calcareous beds, clay shale, sa'nds, and gravels, with a pebbly 

conglomerate at base and containing typical lower Miocene fossils. Thickness450 to 550 feet. The " Reef bed " of former report [which was included in the 

" Coalinga beds"] is properly a part of the Temblor beds. Rest uncouformably 

on Oligocene (?) organic shales, which in former report were thought to be 

Miocene and were called Monterey shales and which overlie the Domijean sands.. 

Strntigraphically and faunally the " Vaqueros sandstone" agrees with the 

Temblor beds and is without doubt to be correlated with the Temblor of the 

Mount Diablo Range.

J. P. Smith, 1910 (Jour. Geology, vol. 18, No. 3). Temblor sandstone. The type 

Temblor is younger than the type Vaqueros and carries a fauna like that of theOcoya Creek beds. The Temblor fauna carries Turritella ocoyana and other 

fossils, while the older or type Vaqueros is characterized by the Turritella.
GEOLOGIC UNITS OF CALIFORNIA 89'

inezana fauna. The true Vaqueros is absent in the Coallnga region, the type 

section of the Temblor, and the true Temblor is absent in the Salinas Valley, 

the type region of the Vaqueros. The true Temblor underlies the diatomaceous 

Monterey shale.

F. M. Andersou, 1911 (California Acad. Sci. Proc., 4th ser., vol. 3, pp. 17+). 

Temblor group. [Describes these deposits in the Kern River region and the 

part of the Diablo Range that is locally known as the Temblor Mountains.] 

Chiefly marine, but locally contains a fresh-water or brackish-water faciea. 

Thickness ranges up to 1,760 feet. Correlates with Ocoya Creek beds. " If 

Monterey is present it can not be separated from the Temblor group." The 

more shaly portion is nearest the base and the beds become coarser toward 

the top, though clays are distributed throughout the column. Called 

" Vaqueros " by Arnold and others. Unconforrnably underlies Kern River group, 

and rests unconformably on granite.

F. M. Anderson and Bruce Martin, 1914 (California Acad. Sci. Proc., 4th ser.,. 

vol. 4, pp. 31-51). Temblor (Vaqueros) beds. [Gives details of the beds.] 

Thickness 500 to 2,500 feet in Temblor Basin and San Juan district. Uncoinformably underlie Monterey shale [ = Salinas shale] and unconformably overlie 

granite. " It has yet to be shown that the so-called Vaqueros beds of Salinas 

Valley are older in time than the Temblor deposits at the base of the Miocene 

in the Great Valley."

B. L. Clark, 1921 (Jour. Geology, vol. 29, pp. 586-614). The Monterey series contains two fairly distinct but closely related faunas, the upper the Temblor group, 

or Turritella ocoyana zone, the lower the Vaqueros group or Turritellu inezana 

zone. A very large percentage of the. Vaqueros species is common to the Temblor. The marine Temblor includes the middle Miocene land formation locally 

known as the Big Blue. The Temblor group corresponds to the " Salinas shale " 

and " Monterey shale " of other reports but is older than the Maricopa shale, 

and the Briones sandstone. In most places it uuconformably overlies Vaqueros 

group and unconformably underlies Santa Margarita formation.

The present generally accepted definition of Temblor formation applies 

the name to the Turritella, ocoyana, zone, of middle Miocene age and 

younger than Vaqueros formation (Twritella inezana zone), of late 

lower Miocene age. Belongs to Monterey group.

Named for exposures on Temblor ranch, in the MoKittrick district, Kern 

County.

Temescal formation.

Recent: Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Secondary alluvium derived from the main alluvial embankment of the San 

Antonio formation in the course of its degradation and consisting of the same 

kind of material, namely, fragments of Mesozoic and Tertiary rocks. Thickness 

varies up to 13 feet. Rests unconformably on the marine Merrltt sand, of 

Pleistocene age. Named for development along Temescal Creek, Alameda 

County.

Tequepis sandstone.

Miocene: Southern California (Santa Barbara County).

R. N. Nelson, 1924 (Geol. Soc. America Bull., vol. 35, pp. 166-167). Is topformation of Monterey series in upper Santa Ynez River region. Is younger 

than Salinas shale, and unconformably beneath Fernando Pliocerre.

R. N. Nelson, 1925 (California Univ. Pub., Dept. Geology Bull., vol. 15, No. 10).. 

Fine-grained light-gray feldspathic and tuffaceous sandstones, in places interbedded with thin layers of brown bituminous shale, and with 100 feet of diatomaceous shale at top. Is characterized by abundance of brown fish scales. -Maximum thickness 1,000 feet. The massive cream-gray tuff that overlies the Salinas. 

shale on the north side of Santa Ynez River one-half mile east of Redrock Canyon 

is considered to be a part of the Tequepis sandstone. The Tequepis is a unit of 

rather limited extent, overlying the Salinas shale in the western portion of the. 

district along Santa Ynez River. Is top formation of Monterey group, which is 

unconformably overlain by Fernando Pliocene. Named for development on Tequepis rnnclio.
90 GEOLOGIC UNITS OF CALIFORNIA

Thompson limestone.

Middle Jurassic: Northern California (Taylorsville region).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). 10 to 30 feet of 

limestone, gray above and red below. " Its position everywhere appears to clearly 

indicate that it lies between the Mormon and Hardgrave sandstones."

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Gray and red limestone lentils in 

calcareous shale. Thickness 10 to 30 feet. Appears to conformably overlie 

Mormon sandstone. Rests on Fant meta-andesite, which in turn is younger than 

Hardgrave sandstone.

Named for exposures on Thompson's ranch, on west slope of Mount Jura, 

east of Taylorsville, Plumas County.

Tice shale.

Miocene (middle): Western California (San Francisco region).

A. C. Lawson, 1914 (U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

Bituminous shale, prevailingly chalky, in some places whitish, in others pinkish 

or yellowish. A formation of Monterey group. Overlies Oursan sandstone and 

underlies Hambre sandstone. Thickness 460 feet. Named for exposures along 

Tice Creek, in the Concord quadrangle.

Tightner formation.

Mississippian: Northern California (Coifax region).

H. G. Ferguson, 1929 (Am. Inst. Min. and Met. Eng. Tech. Pub. 211, p. 4). Tightner 

formation. Almost entirely fine-grained greenish hornblende schist with varying 

amounts of quartz, probably for the most part secondary. Near the veins the 

schist is altered to talc schist. A small amount of quartzose mica schist and 

rare beds of glistening black slate are interbedded. Small lenses of coarsely crystalline white limestone occur here and there. Dominantly of volcanic origin. 

Thickness of formation probably 7,000 feet. Underlies, probably unconformably, 

Kanaka formation, and is believed to overlie Blue Canyon formation, but the two 

are in fault contact. Named for fact that it forms the principal wall rock of the 

Tightner mine. Extends from North Yuba to South Yuba.

Tolenas marble.

Probably late Tertiary or Quaternary: Western California.

W. L. Watts, 1890 (California State Min. Bur. Tenth Ann. Kept., pp. 668-669). 

Pure waxlike aragonite, the work of springs; quarried at Tolenas Springs, 

Solano County.

Tomales formation.

Upper Pleistocene: Western California (Marin and Sonoma Counties). 

R. B. Dickerson, 1922 (California Acad. Sci. Proc., 4th ser., vol. 11, No. 19, maps). 

Largely land or stream-laid deposits, including, terrace deposits containing a 

small but distinctive Pleistocene fauna and also probably material composing 

alluvial fans. In part of the area the formation consists of lignitic beds overlain by loosely consolidated tan-colored sandstones and conglomerates (or 

perhaps fanglomerates would be a better designation) of lighter color than 

the tan-colored sandstones of Millerton formation. A small estuarine fauna 

found in the upper beds indicates that during part of the time the region was 

occupied by a shallow bay. Rests unconformably (important break) on 

Millerton formation.

Named for occurrence on northeast side of Tomales Bay, where most of 

the headlands are thinly coated with the loosely consolidated sandstones and conglomerates of the formation.

Tomales Bay deposits.

Pleistocene: Western California (Marin County).

V. C. Osmont, 1904 (California Univ. Pub., Dept. Geology Bull., vol. 4, p. 76). 

Tomales Bay deposits. According to Anderson, consist of coarse arkose detritus 

with indistinct horizontal stratification. Generally found in the larger depressions of the peninsula. Range in elevation from 500 feet downward. Form
GEOLOGIC UNITS OF CALIFOKNIA 91

a series of low broad hills, extending along the middle of the valley near 

Olema, and occur at intervals on both shores of Tomales Bay, forming there 

a system of low benchlike terraces below 200 feet in height. West of the 

main ridge they are found in occasional patches around the flanks of the 

hills at the head of Drake's Estero and north of Abbott's Lagoon.

Topanga formation.

Miocene (middle) : Southern California (Los Angeles County).

W. S. W. Kew, 1923 (Am. Assoc. Petroleum Geologists Bull., vol. 7, pp. 411-420). 

Name proposed to include the rocks lying below the Modelo formation and 

above the Vaqueros formation and containing the Turritella ocoyana fauna. 

The strata are essentially sandstone. Formerly included in the Vaqueros formation (now restricted to Turritella inezana fauna). Unconformably overlies 

true Vaqueros formation and In Topanga Canyon, Los Angeles County, Is 

overlain with marked unconformity by the Modelo formation. [In U. S. 

Geol. Survey Bull. 753, 1924, Kew gives the thickness of the Topanga formation 

as 6,000 ± feet.]

"Topatopa formation."

Eocene: Southern California (Ventura County).

G. H. Eldridge, 1907 (U. S. Geol. Survey Bull. 309). The lowest formation outcropping in the mountains north of Santa Clara Valley. Total thickness 

unknown, but about 5,500 feet are exposed. This consists of very hard, submassive sandstones (light gray to white) and quartzites (greenish gray, clenr 

or mottled with white) ; shales (of slightly bluish hue) that differ from the 

quartzites in carrying an additional content of mica and in the fineness of 

their material. The quartzites and sandstones greatly predominate in the lower 

2,000 feet, and the shales predominate in the upper 2,500 feet. Quartzites also 

occur near the middle of the formation. The conspicuous features of the 

formation are a tendency to a broad concretionary structure in some of its 

members; the presence of smaller brown ferruginous sand concretions; the 

sparse distribution of fossil oysters and other imperfect molluscan remains 

through a great portion of its thickness, more particularly in the shales; 

some evidences of woody tissue; and a frequent recurrence of what appear to 

be fucoids. Underlies Sespe formation and probably rests on granite.

According to W. S. W. Kew (U. S. Geol. Survey Bull. 753, pi. 3) the 

"Topatopa formation" as above defined corresponds to the Martinez 

and Meganos formations of Bulletin 753, the deposits corresponding 

to the Tejon formation having been included in the overlying Sespe 

formation of Eldridge. The " Topatopa formation" of Arnold as 

described in United States Geological Survey Bulletin 321, 1907, corresponds to the Tejon, Meganos, and Martinez, formations of present 

terminology, all of which Kew has differentiated and mapped in 

neighboring areas.

"Toro" formation.

Lower Cretaceous: Western California (San Luis Obispo region).

H. W. Fairbanks, 1904 (U. S. Geol. Survey Geol. Atlas, San Luis folio, No. 101). 

Dark thin-bedded clay shale, with thin irregular layers of conglomerate at 

bottom and near middle. Thickness about 3,000 feet. Unconformably underlies 

Chico deposits and Unconformably overlies Franciscan deposits. Is the local 

representative of the Knoxville. Named for exposures along Toro Creek, San 

Luis Obispo County.

Replaced by Knoxville formation, the name "Toro" being unnecessary.

Torrey sand.

Eocene: Southern California (San Diego County).

M. A. Hanna, 1926 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 16, No. 

7, pp. 187-246). Sand, usually coarse, porous, and unconsolidated; color 

usually white to light brown; highly cross-bedded. Consists of clean, moderately

17462 31 7
92 GEOLOGIC UNITS OF CALIFORNIA

well rounded grains of quartz with varying amounts of feldspar, some muscovite 

and biotite, and minor amounts of ferromagnesians. Thickness more than 

200 feet. Pinches out to south, where it probably was not deposited. Probably 

increases in thickness to the north. Is middle division of La Jolla formation 

in La Jolla quadrangle. Grades into overlying Rose Canon shale and into underlying Delmar sand. Typically exposed on Torrey Pines grade, where the highway 

climbs from Soledad Valley to the 400-foot terrace to the south.

Trabuco formation.

Cretaceous: Southern California (Santa Ana Mountains).

E. L. Packard, 1916 (California Univ. Pub., Dept. Geology Bull., vol. 9, pp. 140-141). 

Trabuco formation. Massive red conglomerates composed of angular and waterworn boulders loosely cemented, with subordinate bands of red sandstone. 

Thickness 200 feet. No fossils found, but from stratigraphic relations the formation is probably but slightly older than Chico group and presumably represents some phase of the pre-Chico Cretaceous. Grades into overlying Chico 

group and rests unconformably on basement complex. Extends from North 

Star Canyon nearly to Trabuco Canyon. Best exposed at Harding Canyon.

Trail formation.

Lower Jurassic: Northern California (Taylorsville region).

J. S. Diller, 1892 (Geol. Soc. America Bull., vol. 3, pp. 370-394). Trail beds, Triassic(?); 2,900 feet thick. On structural grounds regarded as Triassic and 

probably newer than Hosselkus limestone.

J. S. Diller, 1908 (U. S. Geol. Survey Bull. 353). Largely slaty shales with some 

interbedded sandstone and conglomerates. Shales often purplish or red, but 

perhaps more frequently gray, with pencil structure locally developed; in places 

contain numerous cherty nodules of carbonate of lime. Sandstones generally 

fine, often somewhat slaty, thin bedded, and gray to almost black. Fresh-water 

fossils. Thickness 2,900 feet. Overlaps, unconformably, Swearinger slate, Hosselkus limestone, and Robinson formation. Is next older than marine Hardgrave sandstone, with which it is assumed to be unconformable.

Named for exposures along Hosselkus Creek on the trail, Plumas County, 

California.

" Trampan formation."

Miocene (upper) : Western California (San Francisco region).

A. C. Lawson and C. Palache, 1902 (California Univ. Pub., Dept. Geology Bull., vol. 

2, pp. 447-448). Trampan formation. Marine beds, aggregating about 2,000 

feet, succeeding the fresh-water Orindan deposits. Fauna is, in opinion of Prof. 

J. C. Merriam, closely allied to that of San Pablo formation. Named for exposures along Las Trampas Creek, Contra Costa County.

A. C. Lawson, 1914 ,(U. S. Geol. Survey Geol. Atlas, San Francisco folio, No. 193). 

[Maps the marine beds formerly called " Trampan formation " as the San Pablo 

formation.]

Tres Pinos sandstone. .

Eocene: Southern California (San Benito County).

P. F. Kerr and H. G. Schenck, 1925 (Geol. Soc. America Bull., vol. 36, pp. 470, 475). 

Massive coarse-grained quartzose buff-colored marine sandstone, with conglomerate phases; jointed; more indurated on exposed surfaces; large erosional cavities common. Thickness about 900 feet. No diagnostic fossils. " Of possible 

Eocene age." Is quite similar lithologically to the Pinccate sandstone and may 

prove to be the same. But at present is considered to be Tejon(?), because it 

overlies well-established Meganos deposits with no marked unconformity.

Probably named for exposures at or near Tres Pinos or Tres Pinos Creek.

"Trinity formation."

Term applied by O. H. Hershey (Am. Geologist, vol. 27, p. 226, 1901) to the 

serpentine in the Klamath Mountain region of northern California.
GEOLOGIC UNITS OF CALIFORNIA 93

Truckee formation.

Miocene: Northern Nevada and eastern California (Lake Tahoe region).

Clarence King, 1876 (U. S. Geol. Expl. 40th Par. Atlas, map V) and 1878 (U. S. 

Geol. Expl. 40th Par. Kept, vol. 1, p. 412). Truckee group. Fresh-water deposits of Miocene age, consisting of coarse sands and gravels, white stratified 

trachytic tuff, pelagonite tuff, marly grits, some sandstones, and one 60-foot 

bed of saccharoidal limestone. A large portion of the material is made of 

trachytic muds, which carry, especially in Oregon, numerous numhers of Miocene fossil mammals. The deposits are partly older and partly contemporaneous 

with the trachytes that are interbedded with the sediments. Thickness about 

4,000 feet. Deposited In lake to which the name Pah-Ute lake is applied. [As 

mapped In the above-mentioned atlas the formation occurs in disconnected areas 

across Nevada, indicating the probable deposition of the sediments in several 

disconnected lakes. It is mapped over considerable areas in the valleys east 

and west of the south end of the Truckee Range and in Truckee Canyon between 

Reno and Verdi, Nev.]

Tulare formation.

Pliocene or Pleistocene: Southern California (San Joaquin Valley region).

F. M. Anderson, 1905 (California Acad. Sci. Proc., 3d ser., vol. 2, p. 181). Tulare 

formation. Fresh-water deposits of gypsiferous sands and clays exposed at intervals along the western border of the Great Valley. In Kettleman Hills, 10 to 

15 miles southeast of Coalinga, and near the western shore of Tulare Lake, 

these beds aggregate fully 1,000 feet in thickness. They lie conformably on the 

San Joaquin clays (the upper division of the Etchegoin formation), which they 

in some respects resemble. [Fossils listed.] Doubtfully assigned to Pliocene.

Contemporaneous with part of Paso Robles formation, but deposited in a 

separate basin.

Tuolumne intrusive series.

Probably Cretaceous: Yosemite National Park.

F. C. Calkins, 1930 (U. S. Geol. Survey Prof. Paper 160, p. 121, map). The great 

bulk of the granitic rocks in the Yosemite region belong to two series of intrusions, the members of each series exhibiting an especially close relationship 

to one another. These may be termed the biotite granite series of the Yosemite 

Valley and the Tuolumne intrusive series. * * ° The latter includos 

[ascending order of age] the Sentinel granodiorite, Half Dome quartz monzonite, 

Cathedral Peak granite, and Johnson granite porphyry formations which 

extend in large bodies from the upper half of the Yosemite Valley northward 

to the Tuolumne River and northeastward into the High Sierra.

Named for exposures along Tuolumne River, Yosemite National Park.

Tuscan tuff.

Pliocene and Miocene (?): Northern California (Lassen Peak, Redding, 

and Chico regions).

J. S. Diller, 1895 (U. S. Geol. Survey Geol. Atlas, Lassen Peak folio, No. 15). 

Composed wholly of fragrnental material derived from the numerous volcanoes 

of the Lassen Peak district. Much of it is fine, clearly stratified, and properly 

called tuff, but a large part is an agglomerate of coarse and fine material Intermingled. Most of the fragments are angular, but some beds are made up of 

pebbles woll rounded by water action. Best exposed in canyons of Mill, Deer, 

and other creeks on their way from the mountains to the Sacramento Valley. 

At a number of points there are sheets of lava in the tuff. Is youngest Tertiary 

deposit in region. Rests on lone formation. [The deposits mapped and 

described as Tuscan formation in the preliminary proof-sheet edition of the 

Lassen Peak folio (1892) are divided into Tuscan formation and lone formation 

in the completed Lassen Peak folio.] »

The Tuscan tuff reaches a maximum thickness of more than 1,000 feet. 

Named for exposures at or near Tuscan Springs, Lassen Peak quadrangle.
94 GEOLOGIC UNITS OF CALIFOKNIA

Vaqueros sandstone.

Miocene (lower) : Southern California (Salinas and San Joaquin Valleys).

H. Hamlin, 1904 (U. S. Geol. Survey Water-Supply Paper 89, p. 14). Vaqvero 

sandstone. Rather coarse, uniformly gray, white, or light-yellow quartzose 

sandstone, with an occasional stratum of granitic pebbles. In Salinas Valley 

It is a well-defined formation. So far as observed in this region it rests unconformably on the Basement complex and on stratified terraces older than the 

Neocene, being thus in this locality the oldest known member of the Neocene, 

but in other localities Neocene formations are found below the Vaquero sandstone. Is of great thickness along eastern slope of Santa Lucia Range, especially in Los Vaqueros Valley, hence the designation proposed by the writer for 

this series of sandstones. [Lists fossils. Los Vaqueros Creek is shown on 

Hamlin's map.]

The present generally accepted definition of Vaqueros sandstone is for the 

oldest knowin Miocene deposits in southern California, which range in 

thickness from 500 to 6,000 feet or more and are characterized by the 

Turritella inezana fauna. In the Santa Cruz Mountain region the 

Vaqueros is unconformably underlain by the San Lorenzo formation, of 

Oligocene age. In the Coalinga and neighboring districts it is unconformably underlain by the Kreyenhagen shale, of probable Oligocene 

(early Oligocene?) age. In Ventura and Los Angeles Counties it is 

underlain, in places unconformably, by the Sespe formation, of probable 

Oligocene (late Oligocene?) age. In the Salinas Valley region it is 

conformably overlain by the Salinas shale. In the northwestern part 

of Kern County it is overlain by the Maricopa shale. In Ventura and 

Los Angeles Counties it is overlain, probably conformably, by the 

Topanga formation, which is characterized by the Turritella ocoyanct 

fauna. The Vaqueros sandstone is now generally considered to be 

older than the Temblor sandstone or Twrritella ocoyana zone. The 

United States Geological Survey treats the Vaqueros: as the basal formation of the Monterey group.

Named for exposures on Los Vaqueros Creek, Monterey County.

Ventura sands.

Pliocene: Southern California (Ventura County).

C. M. Carson, 1925 (Pan-Am. Geologist, vol. 43, pp. 265-270). Ventura sands. The 

Ventura formation of Ventura County is well exposed in the foothills between 

Ventura and Santa Paula, in the Las Posas Hills, near Camarillo, on the south 

and west flanks of South Mountain, and in Simi Valley. The formation is from 

500 to 1,000 feet thick and is composed of coarse and fine yellowish sand, which 

in places becomes quite gravelly. It is in general only moderately consolidated, 

although locally hard beds occur. [Fossils listed.] "This fauna is a cold-water 

facies, but its habitat is not so cold as that of. the Santa Barbara fauna which 

follows." Is younger than San Diego clays.

Wagonwheel formation.

Oliogocene(?) : Southern California (McKittrick-Sunset region). 

H. R. Johnson, 1909 (Science, new ser., vol. 30, pp. 63-64). Local occurrence of 

sandstones and several layers of white diatomaceous shales, which appear, upon 

paleontologic evidence, to be of Oligocene age. Underlie Vaqueros sandstone and 

overlie Tejou sandstone. Occur in the isolated group of hills south of Bartons 

and northeast of Point of Rocks, in the Devils Den district.

Named for^exposures north and southwest of Wagonwheel Mountain, Kern 

County.
GEOLOGIC UNITS OF CALIFOBNIA 95

Walker Ridge sandstones.

Post-Franciscan and pre-upper Miocene: Northern California (Humboldt 

County).

W. Stalder, 1915 (California State Min. Bur. Bull. 69, pp. 447-449). Walker Ridge 

sandstones, upper formation of Rainbow series in Humboldt County. Overlie 

Walker Ridge shales. Thickness 50 to 750 feet. Are mostly siliceous and well 

cemented. Vary in color from green to gray; weather yellowish. Older than 

upper Miocene. Named for exposures on Walker Ridge, Humboldt County.

Walker Ridge shales.

Post-Franciscan and pre-upper Miocene: Northern California (Humboldt 

County).

W. Stalder, 1915 (California State Min. Bur. Bull. 69, pp. 447-449). Bluish to black 

to gray soft shale beds alternating with fine to medium grained gray to bluish 

sandstones varying from 3 inches to 10 feet. Minor bands of limestone, some 

chert, and lenses of calcite at a few localities. Thickness 500 to 1,500 feet. 

Basal formation of Rainbow series. Underlies Walker Ridge sandstones. Named 

for Walker Ridge.

"Wallala beds."

" Wallala group."

' Upper Cretaceous: Northwestern California (Mendocino County).

G. F. Becker, 1885 (U. S. Geol. Survey Bull. 19, pp. 7-17). Wallala beds A 

series of sandstones and conglomerates extending along the coast from near 

Fort Ross at least to Wallala. In some places they rest unconformably on 

metamorphosed rocks thought to belong to Kuoxville group. Fauna not decisive 

as to age. Fossils collected near Wallala are regarded by C. A. White as 

probably pre-Chico and younger than Knoxville.

C. A. White, 1885 (U. S. Geol. Survey Bull. 22, p. 8). Wallala group. "Since so 

little is known of the stratigraphical relations of the Wallala and San Diego 

beds with other formations I can not now discuss them fully, but I shall 

give them the provisional name of the Wallala group, referring those of both 

localities to one and the same formation."

The beds referred to belong to the lower part of the Chico formation.

Warner basalt.

Tertiary: Northeastern California (Modoc County).

R. J. Russell, 1928 (California Univ. Pub., Dept. Geol. Sci. Bull., vol. 17, No. 

11, pp. 416-425, map). Warner basalt. A thin sheet of basalt flows. The 

most widespread surface rock in Modoc County, probably covering half of the 

county. Thickness 0 to 600 feet. Named for exposures on sides of Warner 

Valley and for widespread distribution in Warner Lakes Range and Warner 

Range. Underlies rhyolite and overlies Cedarville series, the upper part of 

which contains flora considered to be Mascall (Upper and Middle Miocene). 

The Warner basalt is therefore considered much younger than Columbia River 

basalt.

Weltchpec schists.

Age (?): Northwestern California (Humboldt County).

O. H. Hershey, 1904 (Am. Geologist, vol. 33, p. 357). "The Weitchpec schists 

resemble the most highly metamorphosed Calaveras schists."

0. H. Hershey, 1906 (Am. Jour. Sci., 4th ser., vol. 21, p. 63). "In approaching 

the western border of the belt, the strata are bent up, and presently there 

appears under them a .formation made up of white serlcite and green chloritic 

schists that are evidently sheared rhyolites and andesites. In a very short 

distance another fault brings down the Bragdon slates. This may be repeated 

several times in 20 miles, but far the larger portion of the area is Bragdon. 

The shearing becomes more pronounced toward the west until traces of the 

bedding planes are virtually destroyed. I now consider the Weitchpec schists,
96 GEOLOGIC UNITS OF CALIFORNIA

formerly classed as pre-Bragdon, as a portion of this series. Indeed the 

apparent ancient schists of Redwood Mountain in the Korbel-Hoopa trail 

are probably Bragdon, although undoubted pre-Devonian schists occur in 

South Fork Mountain." --"""

Probably refers to schist exposed at or near Weitchpec, Humboldt County.

White Pine shale.

Mississippian (probably upper and lower) : Northern Nevada and Inyo 

County, Calif.

Arnold Hague, 1883 (U. S. Geol. Survey Third Ann. Kept., pp. 253, 266-267). 

Black argillaceous shales, more or less arenaceous, with intercalations of red 

and reddish-brown friable sandstone, changing rapidly with the locality. 

Plant impressions. Thickness 2,000 feet. Conformably overlies Nevada limestone and is overlain by Diamond Peak quartzite. Named for exposures in the 

White Pine mining district [now known as Hamilton], White Pine County, Nev.

This formation, with a thickness of 1,000 feet, has been identified by 

B. Kirk (U. S. Geol. Survey Prof. Paper 110, 1918) in the Inyo Range 

of eastern California.

Whiterock Bluff shale member.

Miocene (upper) : Southern California (Cuyama Valley).

W. A. English, 1916 (U. S. Geol. Survey Bull. 621, pp. 191-215). Middle member 

of Santa Margarita formation. Conformably overlies Redrock Canyon sandstone member of Santa Margarita formation and is unconformably overlain 

by Morales member of the Santa Margavita. Near Whiterock Bluff, on tho 

north side of Cuyama Valley, it consists of not less than 1,500 feet of white 

" chalky" diatomaceous shale, which rests (unconformably, it is believed) 

on the Monterey group. On south side of Cuyama Valley it consists of interbedded white clay shale, diatomaceous shale, and sandstone, and apparently 

grades into the underlying sandstone and shale beds mapped as Maricopa shale, 

the line of separation being drawn at the lowest horizon at. which Santa Margarita echinoderms occur. Three zones of white sandstone and two zones of 

shale are present, aggregating 2,000 to 2,500 feet, of which about one-third is 

shale.

Wilbur zone.

A petroliferous zone, about 200 feet thick, lying 1,000 feet below top of 

Fernando group in the Long Beach field, Los Angeles Basin.

Wildcat series.

Pliocene: Northern California (Humboldt County, along the coast to 

Eureka).

A. C. Lawson, 1894 (California Univ. Pub., Dept. Geology Bull., vol. 1, pp. 255-263). 

Evenly bedded yellow and brown clays, silty clay shales, sandy clays, argillaceous sands, compact yellow sandstones, and pebbly conglomerates, 4,600 

feet thick. Contain Pliocene fossils and are correlated with the Merced 

formation. " The region occupied by the terrane is commonly known to the 

people of Humboldt County as the ' Wild-cat Country.' " Occupies large part 

of Humboldt County to the north of Bear River Ridge and east of Humboldt 

Bay and is also doubtless extensively developed in the coastal region north 

of Eureka.

Wildrose formation.

Lower Paleozoic (?) : Southeastern California (Inyo County). 

See under Telescope group. Derivation of name not stated.

Wildwood limestone.

Permian: Northern California (Trinity County).

J. P. Smith, 1910 (Jour. Geology, vol. 18, chart opp. p. 217, p. 218). "Limestones 

of Trinity County with Guadalupian fauna, Stacheoceras, etc." Assigned to 

Permian.

Named for Wildwood (Landis's ranch), on Hay Fork.
GEOLOGIC UNITS OF CALIFORNIA 97

Wilmington group.

Late . Pleistocene: Southern California.

R. T. Hill, 1929 (Science, new scr., vol. 69, pp. 379-380). Wilmingtoti group. Has 

hitherto included Lower San Pedro, Upper San Pedro, and [Los] Cerritos stages 

of Arnold, or their equivalents. Contains Pleistocene marine invertebrate 

fossils. Structural and physiographic evidence proves that these beds are older 

than the Pleistocene invertebrate-bearing beds of La Brea pits, but both belong 

to Later Pleistocene stage, and not to Earlier Pleistocene. [Derivation of 

name not stated.]

Wilson Ranch beds.

Pliocene: Western California (Sononia County).

V. C. Osmont, 1904 (California Univ. Pub., Dept. Geology Bull., vol. 4, p. 74). 

West of Santa Rosa Valley, sandstones and small proportion of shales and fine 

volcanic conglomerate, with marine fauna. East of Santa Rosa Valley, sandstones, shales, and a large proportion of coarse volcanic conglomerate; no 

fossils; coarseness of gravel and close bedding indicating fluviatile origin. 

Believed to be older than St. Helena rhyolite and younger than Sonoma tuff.

Probably named for exposures on a ranch in Sonoma County.

Wymer beds.

Miocene (upper), Pliocene, or Pleistocene: Northwestern California (Del 

Norte County).

J. S. Diller, 1902 (U. S. Geol. Survey Bull. 196, pp. 32-35, 47). Neocene marine 

deposits occur " on the edge of the plateau at an elevation of about 2,200 feet, 

along the old Wymer stage road, in sec. 20, about 13 miles northeast of Crescent 

City. North of the old Harvey place, where Thomas Haley now lives, a thin 

coating of the soft iron-stained, slightly indurated shaly sand Is exposed on the 

banks of the road for several miles and has furnished numerous imperfect casts 

of mollusks as well as impressions of leaves. A short distance farther eastward, in an excavation made by Mr. Williamson near his barn, in sec. 22, a 

very fine, soft gray sandy clay, very slightly indurated, is rich in shells. The. 

deposits of the two localities just mentioned will be called for distinctness the 

Wymer beds. They are very, thin, resting on schists, peridotite, sandstone, and 

other rocks." [Fossils described.] Flora said to be upper Miocene by F. H. 

Knowlton. W. H. Ball says fauna is not characteristic but not older than 

Tertiary. " If on further study the Wymer beds should turn out to be Pliocene 

or Pleistocene the age of the Klamath peneplain would be correspondingly 

reduced."

" Yuha reefs."

Miocene (lower) : Southern California (Imperial County).

G. D. Hanna, 1926 (California Acad. Sci. Proc., 4th ser., vol. 14, p. 435). "Above 

these [Coyote Mountain] clays, and interbedded with them near the top to 

some extent, are extensive deposits of oyster shells for which the name Yuha 

Reefs has been selected. The type locality has been chosen as a prominent hill 

made up of the material, thoroughly cemented and partially metamorphosed, 

located on the east end of the Coyote Mountain uplift. The same reefs are 

found on Yuha Buttes." Overlain by Coahuila silt. Assigned to Pliocene, 

probably middle or upper Pliocene.

Are interbedded at different horizons in upper part of Imperial formation. 

See W. P. Wooclring, 1931, under Imperial formation.

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