Lower and Middle Tertiary 

Stratigraphic Units of 

the San Emigdio and 

Western Tehachapi Mountains, 

California _______

GEOLOGICAL SURVEY BULLETIN 1372-H
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Lower and Middle Tertiary 

Stratigraphic Units of 

the San Emigdio and 

Western Tehachapi Mountains, 

California

By T. H. NILSEN, T. W. DIBBLEE, JR., and W. O. ADDICOTT

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1372-H

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1973
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress catalog-card No. 73-600123

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

Washington, D.C. 20402 Price 35 cents domestic postpaid or 25 cents GPO Bookstore

Stock Number 2401-00343
CONTENTS

Page

Abstract...................................................................................................................... HI

Introduction .............................................................................................................. 1

Regional geology ...................................................................................................... 2

Previous work............................................................................................................ 4

Stratigraphic sequence ............................................................................................ 7

Tejon Formation .............................................................................................. 7

San Emigdio Formation .................................................................................. 9

Pleito Formation .............................................................................................. 12

Tecuya Formation............................................................................................ 15

Temblor Formation .......................................................................................... 18

Monterey Shale and unnamed conglomerate ............................................ 19

Summary .................................................................................................................. 20

References cited........................................................................................................ 21

ILLUSTRATIONS

Page

FIGURE 1. Simplified geologic map of the San Emigdio and

western Tehachapi Mountains ................................................ H3

2. Lower and middle Tertiary formations exposed in the

San Emigdio and western Tehachapi Mountains ................ 4

3. Diagram showing lithofacies and geologic relations of 

pre-upper Miocene stratigraphic units of the 

San Emigdio and western Tehachapi Mountains ................ 8

IH

CONTRIBUTIONS TO STRATIGRAPHY

LOWER AND MIDDLE TERTIARY 

STRATIGRAPHIC UNITS OF THE

SAN EMIGDIO AND

WESTERN TEHACHAPI MOUNTAINS,

CALIFORNIA

By T. H. NILSEN, T. W. DIBBLEE, JR., and W. O. ADDICOTT

ABSTRACT

Lower and middle Tertiary stratigraphic units exposed in the San Emigdio 

and western Tehachapi Mountains, Calif., consist of the Tejon Formation 

(Eocene), San Emigdio Formation (late Eocene and Oligocene), Pleito Formation (Oligocene), Tecuya Formation (late Eocene (?) to early Miocene), 

Temblor Formation (early Miocene), and the Monterey Shale and an unnamed 

conglomerate unit (both middle and late Miocene). These units, well exposed 

in the central part of the report area, constitute one of the few fossiliferous, 

continuously deposited marine sedimentary sequences in California of early 

and middle Tertiary age. This sequence is moderately thick, and the marine 

strata interfinger eastward into nonmarine beds that contain fossil mammals 

and include radiometrically dated volcanic rocks. The marine San Emigdio and 

Pleito Formations and the nonmarine Tecuya Formation are redefined in this 

paper according to lithology, thickness, stratigraphic relations, depositional 

environments, ages, type sections, and type localities.

Most of the marine Eocene, Oligocene, and early Miocene strata were 

deposited on a shallow marine shelf that deepened westward and northward. 

The nonmarine fluvial strata of the Tecuya Formation to the east were probably 

deposited as alluvial fans fringing the shallow marine shelf. Climatic and 

tectonic changes affecting the supply of sediment resulted in a migrating and 

oscillating shoreline. Tectonic uplift in the southwestern part of the San 

Emigdio Mountains during Oligocene and early Miocene time produced a local 

angular unconformity.

INTRODUCTION

The lower and middle Tertiary stratigraphic units exposed in the 

San Emigdio and western Tehachapi Mountains form a sequence of 

sedimentary and volcanic rocks that is valuable for related stratigraphic and paleontologic studies in California. The section is moderately thick, complete, and well exposed in most of the area and

Hi
H2 CONTRIBUTIONS TO STRATIGRAPHY

contains interbedded volcanic rocks that have been radiometrically 

dated. In addition, the exposures present an east-west cross section 

of similar rocks that are concealed under the south end of the San 

Joaquin Valley. The continuous succession of Eocene to middle Miocene shallow-water molluscan assemblages in the central part of the 

area can be compared with both deeper water foraminiferal assemblages to the west and mammalian assemblages and radiometric dates 

from nonmarine sedimentary and volcanic rocks to the east.

The ages, stratigraphic relations, and depositional environments 

discussed in this report are drawn from various sources: original 

geologic mapping by Dibblee (1961) and subsequent modifications 

by him, detailed sedimentologic and stratigraphic studies of the 

Tejon Formation by Nilsen (1972), and analyses by Addicott of 

paleontologic reports of earlier workers, supplemented by some new 

fossil collections. Reference should be made to the more detailed maps 

of Dibblee (1961), Dibblee and Nilsen (1973), and Harris (1950) for 

outcrop localities.

REGIONAL GEOLOGY

The lower and middle Tertiary sedimentary sequence exposed on 

the north flanks of the San Emigdio and western Tehachapi Mountains rests unconformably on a pre-Tertiary crystalline basement 

complex of plutonic and metamorphic rocks, which constitute the 

greater part of both ranges (fig. 1). Except for the Los Lobes Canyon 

area in the western part of the San Emigdio Mountains, the basement 

complex is primarily granitic. These plutonic rocks are presumably 

of Mesozoic age and cogenetic with the Sierra Nevada batholiths. In 

the Los Lobos Canyon area, the basement complex is a mass of mafic 

and ultramafic igneous and metamorphic rocks that Ross (1970) suggested may represent a fragment of Mesozoic oceanic crust.

The lower and middle Tertiary strata generally dip northward off 

the basement complex and have been folded and faulted along a series 

of south-dipping thrust faults. The large northeast-plunging syncline 

in the Devils Kitchen area dominates the structure of the Tertiary 

rocks in the San Emigdio Canyon area. The Tertiary sequence 

thickens westward from a few hundred feet in the easternmost exposures to many thousands of feet. Some of the units extend northwestward into the adjoining northwest-trending Temblor Range. The ages 

and formation names of the lower and middle Tertiary units discussed in this report are shown in figure 2.

Eocene rocks of the San Emigdio and western Tehachapi Mountains consist of the Tejon Formation, the lower part of the San Emigdio Formation, and possibly the lowest part of the Tecuya Formation. 

Oligocene rocks are represented by the upper part of the San Emigdio
11915' 119 00' 118 45'

35 00'

EXPLANATION 

ROCK UNITS

Alluvium

Post-Miocene strata 

Monterey Shale Unnamed conglomerate 

Temblor Formation 

Volcanic rocks Tecuya Formation

San Emigdio Formation >£ Tejon Formation iBasement complex

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Contact

Fault

Dotted where concealed. Arrows indicate relative horizontal movement

FIGURE 1. Simplified geologic map of the San Emigdio and western Tehachapi Mountains. Modified from Geologic Map of 

California ( Smith, 1964; Jennings and Strand, 1969). DK, Devils Kitchen area, location of Devils Kitchen syncline. ffi co
H4 CONTRIBUTIONS TO STRATIGRAPHY

System

TERTIARY

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Lower Tertiary

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Series

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Provincial stage 

Megainvertebrate Foraminiferal

"Margaritan"

"Temblor"

"Vaqueros"

Unnamed

Refugian

"Tejon"

"Transition" \

"Domengine" A

"Capay" \

Mohnian

Luisian 

Relizian

Saucesian

Zemorrian

Refugian

Narizian

Ulatisian \

Penutian \

Formation

Monterey Unnamed 

Shale conglomerate

Temblor \.

Formation ^.,-fti i' 1 ".' '""-"'"" " 1 1 

<Qj[J | Volcanic u nit 1 1

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^^. Tecuya

Pleito ^\ 

Formation /

San Emigdio\. 

Formation \.

Tejon Formation

Basement complex

FIGURE 2. Lower and middle Tertiary formations exposed in the San 

Emigdio and western Tehachapi Mountains. Foraminiferal stages from 

Kleinpell (1938) and Mallory (1959); megainvertebrate stages from 

Weaver and others (1944) and Addicott (1972).

Formation and the Pleito Formation in the western part of the area 

and by most of the Tecuya Formation in the eastern part. Miocene 

rocks include the Temblor Formation and the Monterey Shale to the 

west, the upper part of the Tecuya Formation and the unnamed conglomerate to the east. The lower and middle Tertiary sequence is 

overlain unconformably by late Cenozoic predominantly nonmarine 

sedimentary rocks described and mapped by Hoots (1930), Dibblee 

(1961),andDibbleeandNilsen (1973).

PREVIOUS WORK

Whitney (1865), working in the San Emigdio Canyon area, was 

the first to separate unnamed younger marine strata thought to be 

of early Tertiary age from the underlying Tejon beds, then considered 

to be of Late Cretaceous age (fig. 1).

Anderson (1908, p. 20) stated that his Temblor beds in the 

Temblor Range (later Temblor Formation) "occur, however, on the 

San Emigdio [Creek] and at Kern River."
SAN EMIGDIO AND TEHACHAPI MOUNTAINS, CALIFORNIA H5

Anderson (1912) extended the marine Vaqueros Formation, then 

considered to be of early Miocene age, from the Temblor Range 

southeastward into the San Emigdio Mountains, applying the name 

to strata immediately overlying the Tejon beds; he did not clearly 

defiine its boundaries, however, or show it on a geologic map.

Dickerson (1915) reviewed the history of the controversy surrounding the age of the Tejon beds, which were eventually proved 

to be of Eocene age.

Dickerson (1916) and Gester (1917) first mentioned the existence 

of marine Oligocene beds in the San Emigdio Mountains but did not 

describe them.

Clark (1918, p. 100) recognized the presence of Oligocene beds in 

the San Emigdio Mountains and defined a maximum thickness for 

them in the vicinity of San Emigdio Canyon of between 2500 and 

3000 feet. He recognized a fauna similar to that of the San Lorenzo 

Formation of the Santa Cruz Mountains, then considered to be of 

Oligocene age (Branner and others, 1909) "in beds which are unconformable below beds contains fauna of the lower Miocene."

Pack (1920) recognized beds of Oligocene age in the San Emigdio 

Canyon area, but included them in the Vaqueros Formation which he 

considered to be unconformable on the underlying Tejon Formation.

Stock (1920,1932) found* mammalian fossils of early Miocene age 

near Tecuya Creek in red beds that he designated the "Tecuya beds"; 

these beds included interbedded volcanic rocks and were thought to 

rest unconformably on the Tejon Formation.

Wagner and Schilling (1923) defined and named the San Emigdio 

and Pleito Formations in the San Emigdio Canyon area and assigned 

both of these marine units to the San Lorenzo Group, which they 

correlated with the San Lorenzo Formation of Branner, Newson, and 

Arnold (1909) in the Santa Cruz Mountains. They considered the 

San Emigdio Formation to be unconformable on the underlying 

Eocene Tejon Formation and retained the name Vaqueros Formation 

for the overlying lower Miocene strata.

Hoots (1930) did not differentiate the San Emigdio and Pleito 

Formations of Wagner and Schilling, but included both in the San 

Lorenzo Formation, which he considered to be Oligocene and conformable between the Tejon Formation below and the Vaqueros 

Formation above. He recognized the nonmarine "Tecuya beds" of 

Stock (1920) east of Tecuya Creek, but included them in the 

Vaqueros Formation.

Henny (1938) briefly described the lithology of the San Lorenzo 

Group west of San Emigdio Canyon.

Marks (1941, 1943) traced the "Tecuya beds" of Stock eastward 

from Tecuya Creek into the type area of the Tejon Formation around
H6 CONTRIBUTIONS TO STRATIGRAPHY

Grapevine Canyon; he named these nonmarine red beds the Tecuya 

Formation and considered them to be disconformable on the underlying Tejon Formation. He considered the Tecuya early Miocene in 

age and noted that volcanic rocks and fossiliferous marine siltstones 

were interbedded in it.

Dibblee and Kelly (1948) andMcGill (1951) abandoned use of the 

term San Lorenzo Group and mapped the San Emigdio and Pleito 

Formations of Wagner and Schilling (1923) in the San Emigdio 

Canyon area.

Harris (1950, 1954) mapped the Tecuya Formation between Pastoria and Tunis Creeks, dividing it into three unnamed members 

having a total thickness of 1,090 feet; two of the members included 

marine beds. He noted that the Tecuya was slightly unconformable 

on the Tejon Formation and that east of Tunis Creek it was unconformable on granitic basement rocks.

Durham, Jahns, and Savage (1954) discussed the vertebrate fauna 

of the Tecuya Formation in relation to marine Tertiary rocks.

Van Amringe (1957) mapped 680 feet of fossiliferous Oligocene 

San Emigdio Formation that he thought rested conformably on the 

Tejon Formation in the Brush Mountain area.

Hammond (1958) measured a thickness of 8,970 feet of fossiliferous 

Oligocene strata between Los Lobos and Santiago Creeks and designated the strata the San Emigdio-Pleito Formation, undifferentiated.

Dibblee (1961) differentiated the following Tertiary formations on 

a geologic map of the San Emigdio Mountains in ascending order: the 

Tejon Formation (Eocene), the San Emigdio Formation (late Eocene 

and Oligocene), the Pleito Formation (Oligocene and early Miocene), 

and the Temblor Formation (early Miocene), all marine, and the 

nonmarine Tecuya Formation, which contains basalt and dacite and 

intertongues westward into the Pleito and Temblor Formations.

Tedford (1961) discovered new mammalian fossils in the Tecuya 

Formation, permitting it to be correlated with the marine Vaqueros 

Formation.

Kleinpell and Weaver (1963) reviewed paleontologic data on the 

San Emigdio and Pleito Formations, and concluded that the lower 

part of the San Emigdio is of late Narizian age, the upper part of the 

San Emigdio and the lower part of the Pleito are of Refugian age, 

and the upper part of the Pleito is of Zemorrian age.

Crowell (1964) compiled a map of the San Emigdio Mountains 

from many sources, but used the same Tertiary units as Dibblee 

(1961).

DeLise (1967) studied the stratigraphy and paleontology of the 

San Emigdio Formation in San Emigdio Canyon in detail; he con-
SAN EMIGDIO AND TEHACHAPI MOUNTAINS, CALIFORNIA H7

sidered it to range in age from late Eocene (Narizian) to Oligocene 

(Refugian) and did not recognize an unconformity at its base or top.

Jennings and Strand (1969) compiled a map of the San Emigdio 

Mountains from published sources.

Nilsen (1972) suggested that the Tecuya Formation conformably 

overlies the Tejon Formation and that the two formations represent 

partly laterally equivalent nonmarine and shallow-marine deposits of 

a regressing shoreline.

STRATIGRAPHIC SEQUENCE

The stratigraphic relations between the lower and middle Tertiary 

formations of the San Emigdio and western Tehachapi Mountains are 

shown in figure 3. Deposition began with the marine Tejon Formation, of Eocene age, which was deposited over most of the area. Overlying the Tejon Formation in the western part of the area is a 

sequence of conformable marine units, in ascending order, the San 

Emigdio, Pleito, and Temblor Formations. These formations interfinger eastward into the nonmarine Tecuya Formation, which conformably overlies the Tejon Formation in the eastern part of the area. 

Sedimentary facies in the central part of the area thus define an 

oscillating Eocene, Oligocene, and lower Miocene shoreline. The 

Temblor Formation of the western and central parts of the area is 

conformably overlain by the Monterey Shale of Miocene age. The 

Monterey Shale intertongues eastward into an unnamed nonmarine 

conglomerate which unconformably overlies the Tecuya Formation 

in the eastern part of the area.

TEJON FORMATION

The Tejon Formation, the oldest Tertiary unit in the San Emigdio 

Mountains, rests unconformably on the pre-Tertiary basement complex. It consists of marine sandstones and shales, with some interbedded conglomerates and siltstones. Marks (1941, 1943) divided it 

into four members. Mollusks found in it span the provincial Eocene 

stages, ranging from the "Capay Stage" 1 near the base of the Tejon 

Formation near Santiago Creek (USGS loc. M4654) to the "Tejon 

Stage" (USGS localities between Pleito and Tunis Creeks) (fig. 2). 

The Tejon gradually thickens westward from a few feet near Tunis 

Creek to a maximum thickness of about 4,000 feet near Pleito Creek. 

West of Pleito Creek, it thins to less than 2,000 feet near San Emigdio 

Canyon and to about 1,000 feet near Santiago Creek (Hammond, 

1958). West of Salt Creek, it is overlain by the San Emigdio Formation; east of Salt Creek, by the Tecuya Formation; and near Brush

'Stage names are those of Weaver and others (1944).
H8 CONTRIBUTIONS TO STRATIGRAPHY

'S>
SAN EMIGDIO AND TEHACHAPI MOUNTAINS, CALIFORNIA H9

Mountain, unconformably by the Temblor Formation. The Tejon 

consists primarily of shallow marine deposits in its eastern exposures 

and deep marine deposits in its western exposures (Nilsen, 1972).

SAN EMIGDIO FORMATION

DEFINITION

The San Emigdio Formation, named by Gester (1917), was mapped 

and defined by Wagner and Schilling (1923) as a sequence of marine 

sandstone and shale about 1,000 feet thick on the east side of San 

Emigdio Canyon in the Devils Kitchen area. They believed it to lie 

unconformably on the Tejon Formation and to contain molluscan 

fossils distinct from those of the Tejon Formation. The name San 

Emigdio is adopted in this report. The formation is well exposed 

between Salt and San Emigdio Creeks and discontinuously exposed 

farther west to Santiago Creek (fig. 1).

TYPE SECTION

The type section of the San Emigdio Formation is designated as 

the section mesured by DeLise (1967, p. 9-10) on the east side of San 

Emigdio Canyon in the Devils Kitchen area, 5^ miles south of the 

San Emigdio Ranch headquarters, in the SE14 sec. 31, T. 10 N., R. 21 

W., San Bernardino base line and meridian, Eagle Rest Peak 7^- 

minute quadrangle:

Pleito Formation (lower part) :

Gray, buff, and tan, massive, medium-grained micaceous sandstone. 

Conformable contact 

San Emigdio Formation:

Alternating sequences of buff, yellowish-brown, and gray 

thick-bedded to flaggy arkosic sandstone and dark-red bands 

and lenticular bodies of sandstone containing abundant marine 

megafossils; some stringers of pebble conglomerate ............................ 430

Bluish-gray to black sandy shale with interbedded tan to

greenish-gray calcareous mudstone ...................................................... 300

Massive to thick-bedded medium-grained arkosic sandstone

with thin siltstone interbeds .................................................................... 190

Massive buff to tan medium- to coarse-grained arkosic

sandstone with stringers of pebble conglomerate ................................ 170

Total thickness (feet) .................................................................. 1,090

Conformable contact

Tejon Formation (upper part):

Dark-gray, brown, and greenish-brown sandy shale with 

thin-bedded to slabby and flaggy fine-grained sandstones.

LITHOLOGY, THICKNESS, AND STRATIGRAPHIC RELATIONS 

In the San Emigdio Canyon area, the lower part of the San Emigdio 

Formation consists of thickly bedded gray and tan unfossiliferous
H10 CONTRIBUTIONS TO STRATIGRAPHY

medium- to coarse-grained locally conglomeratic sandstone beds; the 

middle part of bluish-black shales; and the upper part of thickly 

bedded gray and tan sandstone, locally conglomeratic and with thin 

interbeds of gray to red calcareous sandstones containing abundant 

molluscan fossils. These richly fossiliferous sandstones form a persistent marker zone traceable on both sides of the Devils Kitchen 

syncline. As the formation thins to the east, it grades laterally into a 

continuous sequence of gray fine- to medium-grained sandstone containing abundant molluscan fossils near Pleito Creek and into a gray 

to white coarse-grained unfossiliferous conglomeratic sandstone with 

abundant medium and large-scale cross-stratification at Salt Creek. 

West of San Emigdio Canyon, it grades laterally into a series of 

locally fossiliferous fine- to coarse-grained conglomeratic sandstones 

that are interbedded with siltstones and shales (Van Amringe, 1957; 

Hammond, 1958) and at one place contains a large lens of granitic 

breccia (DibbleeandNilsen, 1973).

The San Emigdio Formation is 1,090 feet thick in its type section 

at San Emigdio Canyon (DeLise, 1967). Eastward it thins gradually 

to about 700 feet at Salt Creek. West of San Emigdio Canyon it 

thickens, but because of structural complexity its true thickness 

cannot be determined; as much as 4,300 feet of the formation may be 

exposed at Santiago Creek. Hammond (1958) measured a combined stratigraphic thickness of 8,970 feet for the undifferentiated 

San Emigdio-Pleito Formation near Santiago Creek. On Brush 

Mountain the San Emigdio Formation is locally missing.

In the Devils Kitchen area, massive conglomeratic sandstone at 

the base of the San Emigdio Formation conformably overlies thinly 

interbedded fine-grained sandstones and shales of the Tejon Formation. The thinner bedded upper sandstones of the San Emigdio 

Formation are conformably overlain by massive medium-grained 

conglomeratic sandstone beds forming the base of the Pleito Formation. East of the Devils Kitchen area, the San Emigdio Formation is 

overlain conformably by a thin finger of westward-thinning nonmarine conglomerate of the Tecuya Formation, which separates it 

from the overlying Pleito Formation with no discordance or evidence 

of unconformity with the underlying Tejon Formation. West of San 

Emigdio Canyon, the San Emigdio Formation continues to conformably overlie the Tejon Formation and to be overlain conformably by 

the Pleito Formation. West of Santiago Creek the San Emigdio Formation is concealed beneath extensive outcrops of the Pleito and 

Temblor Formations (figs. 2, 3). On Brush Mountain the San Emigdio Formation may be unconformable on the Tejon Formation, 

although stratigraphic relations are not well defined in this area.
SAN EMIGDIO AND TEHACHAPI MOUNTAINS, CALIFORNIA Hll 

DEPOSITIONAL ENVIRONMENT

Molluscan fossils are locally abundant in the sandstone beds of the 

San Emigdio Formation, especially in the upper beds. They suggest 

shallow-water, inner shelf deposition (depths of less than about 20 

fathoms). Assemblages from near Pleito Creek suggest deposition in 

very shallow water, possibly intertidal, and indicate shoaling to the 

east; Nilsen (1972) suggested that the formation grades laterally 

eastward into a shoreline facies and then into nonmarine beds of the 

Tecuya Formation. Foraminiferal assemblages in the lower and middle parts of the formation represent upper bathyal or lowermost outer 

shelf depths (DeLise, 1967). The mollusks of the San Emigdio Formation are suggestive of unusually cool water conditions, as compared with the warm-water mollusks of the underlying Tejon 

Formation and of the post-Refugian part of the overlying Pleito 

Formation (Addicott, 1970).

In the Brush Mountain area, the stratigraphic and thickness irregularities of the San Emigdio Formation, the granitic breccia lens 

within it, and the possible unconformity at the base of this formation 

suggest local penecontemporaneous tectonic activity.

AGE

On the basis of molluscan faunas, the San Emigdio and Pleito 

Formations were assigned by Wagner and Schilling (1923) to the 

San Lorenzo Group, then considered to be of Oligocene age. The San 

Emigdio Formation was later included by Schenck and Kleinpell 

(1936, p. 219) in their Refugian Stage, which they considered to be 

of late Eocene or early Oligocene age.

The upper part of the type section of the San Emigdio Formation 

was assigned to the upper part of the Refugian Stage by Kleinpell 

and Weaver (1963) and DeLise (1967) on the basis of molluscan 

faunas. The middle and lower parts of the section were assigned to 

the Narizian Stage by DeLise (1967) on the basis of foraminiferal 

faunules (fig. 2). North of the Devils Kitchen syncline, however, 

localities at or near the base of the San Emigdio on the east side of 

San Emigdio Canyon (USGS Iocs. M432, M4595, M4658) yield 

Refugian mollusks including Turritella variata lorenzana and Olequahia lorenzana. Accordingly, molluscan and foraminiferal provincial ages of the lower part of the San Emigdio seem to be in conflict, 

as shown in figure 2. Moreover, a molluscan assemblage from the 

base of the formation (Hammond, 1958) near Santiago Creek 

includes Acila shumardi, indicating a post-Narizian Refugian age. As 

indicated in figure 2, the Refugian is considered to be entirely of
H12 CONTRIBUTIONS TO STRATIGRAPHY

Eocene age by some workers and in part, or entirely, of Oligocene age 

by others.

The middle shale unit of the San Emigdio Formation in the Devils 

Kitchen area, assigned to the Narizian foraminiferal stage by DeLise 

(1967), is of approximately the same age as the Reed Canyon Silt 

Member of the Tejon Formation, as defined by Marks (1943, p. 535). 

The Reed Canyon Member was subsequently renamed the Reed 

Canyon Siltstone Member by Nilsen (1972). Its type section is in 

Reed Canyon about 1 mile west of Grapevine Creek (fig. 1). Additional detailed mapping will be required to determine whether the 

Reed Canyon Siltstone and the middle shale unit of the San Emigdio 

Formation are discontinuously laterally equivalent rock units or 

whether they are merely lithologically similar rock units of approximately the same age.

PLEITO FORMATION

DEFINITION

The Pleito Formation was defined and named by Wagner and 

Schilling (1923), presumably for Pleito Creek, as a sequence of 

marine sandstones and shales about 2,300 feet thick near San Emigdio 

Canyon. They considered it to disconformably overlie the San 

Emigdio Formation and to underlie the Vaqueros Formation and 

furthermore indicated the occurrence in the Pleito Formation of an 

Oligocene molluscan fauna distinct from that of the San Emigdio 

and Vaqueros Formations. The name Pleito Formation is adopted in 

this report. The formation is exposed between San Emigdio and Salt 

Creeks and from Los Lobos Creek west to and beyond Santiago Creek.

TYPE SECTION

The type section of the Pleito Formation is designated as the east 

side of San Emigdio Canyon as described by Wagner and Schilling 

(1923, p. 239), about 5 miles south of the San Emigdio Ranch headquarters, in the E% sees. 31 and 32, T. 10 N., R. 21 W., San Bernardino base line and meridian, Eagle Rest Peak 7 1/% -minute quadrangle.

Temblor Formation (lower part):

Thick-bedded to massive conglomeratic sandstone. 

Conformable contact 

Pleito Formation:

Massive buff sandstone with local conglomerate near top. 

Fossiliferous ................................................................................................ 500

Massive coarse-grained white sandstones and grits ................................ 100

Massive buff and yellowish-brown sandstones with fossiliferous

zone near top .............................................................................................. 500

Alternating series of brownish and pearl-gray micaceous shales 

with minor amount of fine-grained sandstones of same color. 

Few fossils near base ................................................................................ 800
SAN EMIGDIO AND TEHACHAPI MOUNTAINS, CALIFORNIA H13

Pleito Formation Continued

Pearl-gray and light-yellowish massive micaceous sandstone 

with minor amount of sandy shale. Very fossiliferous near top. 

Thin basal conglomerate .......................................................................... 400

Total thickness (feet) .................................................................. 2,300

Conformable contact

San Emigdio Formation (upper part):

Alternating sequences of buff, yellowish-brown, and gray 

thick-bedded to flaggy arkosic sandstone and dark-red bands 

and lenticular bodies of sandstone containing abundant marine 

megafossils; some stringers of pebble conj?lomerate.

LITHOLOGY, THICKNESS, AND STRATIGRAPHIC RELATIONS 

In San Emigdio Canyon, the Pleito Formation is composed of 

thickly bedded light-gray sandstone in the lower and upper parts, 

thinly bedded fine-grained gray sandstones and silty shales in the 

middle part. The base of the formation here is marked by very thick 

massive beds of finely conglomeratic medium- and coarse-grained 

sandstone.

Eastward, toward Pleito Creek, almost the entire formation 

becomes light-gray sandstone that interiingers eastward near Pleito 

and Tecuya Canyons into part of the nonmarine Tecuya Formation 

(Dibblee, 1961). A westward-thinning tongue of nonmarine conglomerate from the base'of the Tecuya Formation separates the 

Pleito Formation from the underlying San Emigdio Formation east 

from San Emigdio Canyon (fig. 3). This conglomerate was previously 

considered to be a basal conglomerate of the Pleito Formation lying 

unconformably on the San Emigdio Formation (Wagner and Schilling, 1923). West of the nonmarine tongues of the Tecuya Formation, 

the marine San Emigdio, Pleito, and Temblor Formations can be 

differentiated by means of their thickly bedded basal sandstones, 

which overlie more thinly bedded finer grained rocks.

West of Los Lobos Creek, the Pleito and underlying San Emigdio 

Formation are difficult to differentiate because exposures are poor 

and structure is complex. However, the Pleito can be separated from 

the San Emigdio Formation in this area on general lithology and 

stratigraphic position, although Dibblee (1961) and Hammond 

(1958) did not distinguish the two formations (fig. 1). In Los Lobos 

and Santiago Canyons, the Pleito Formation ranges in thickness from 

2,000 to 3,000 feet and is divisible into two units: a lower unit, 200- 

400 feet thick, of light-gray massive sandstone, an upper unit, 1,800- 

2,500 feet thick, of poorly bedded rmidstone. The westernmost 

exposures of the Pleito Formation are about 3 miles west of Santiago 

Creek, beyond which it is concealed beneath extensive outcrops of 

the Temblor Formation (fig. 3).
H14 CONTRIBUTIONS TO STRATIGRAPHY

The Pleito Formation is about 2,300 feet thick on the east side of 

San Emigdio Canyon and probably maintains approximately the 

same thickness to the east and west. It is conformable between the 

San Emigdio Formation below and the Temblor Formation above. To 

the east, it intertongues with the Tecuya Formation; to the west, it 

dips beneath younger formations. On Brush Mountain, the lower part 

of the coarse, conglomeratic sandstone mapped as the Temblor Formation, resting unconformably on the San Emigdio and Tejon Formations, may be in part equivalent to the Pleito Formation.

DEPOSITIONAL ENVIRONMENT

Local abundance of in situ mollusks indicates that the sandstones 

in the Pleito Formation east of San Emigdio Canyon were deposited 

in a shallow-water marine environment. Many of the molluscan 

assemblages are in close proximity to the Oligocene shoreline defined 

by the interfingering of the marine Pleito Formation to the east with 

red beds of the Tecuya Formation (fig. 3). Foraminiferal shales of 

the Pleito between San Emigdio and Pleito Creeks include Siphogenerina nodifera (Dibblee, 1961, p. 17) and Cyclamina incisa 

(DeLise, 1967), which are indicative of deep water, middle to lower 

bathyal (Bandy and Arnal, 1969). Near Santiago Creek to the west, 

the lower standstones of the Pleito Formation contain molluscan 

assemblages (Barbat and Von Estorff, 1933; Hammond, 1958) indicative of relatively shallow water deposition. Stratigraphically higher 

shales in the Pleito Formation of Dibblee (1961) in this area contain 

foraminifers referable to the middle to lower bathyal biofacies of 

Bandy and Arnal (1969). Deposition of the Pleito records a series of 

fluctuations between shallow marine environments in which molluskbearing sandstones were deposited and deeper water offshore environments in which foraminiferal shales were deposited. These changing 

water depths probably correlate with eastward and westward migrations of the shoreline that are defined by the contact between the 

Pleito and Tecuya Formations to the east. If the Temblor Formation 

on Brush Mountain is in part equivalent to the Pleito Formation, 

then local uplift and emergence occurred in this area.

AGE

The lower part of the Pleito Formation was initially assigned to 

the Refugian Stage by Schenck and Kleinpell (1936) on the basis of 

molluscan assemblages recorded by Wagner and Schilling (1923). 

Mollusks from the overlying middle and upper parts of the Pleito 

have long been recognized as representing a younger time-stratigraphic unit of pre-"Vaqueros" age (Clark in Hoots, 1930, p. 254;
SAN EMIGDIO AND TEHACHAPI MOUNTAINS, CALIFORNIA H15

Weaver and others, 1944, chart). This distinctive fauna, characterized by Pecten sanctaecruzensis and Vertipecten n. sp. has recently 

been assigned to an unnamed molluscan stage (Addicott, 1972) of 

provincial late Oligocene age. Foraminifera from the middle and 

upper parts of the Peito Formation between Pleito Creek on the east 

(Dibblee, 1961, p. 17) and near Santiago Creek to the west (Kleinpell, 1938, p. 57-60, loc. 12) are of early Zemorrian (Oligocene) age 

(Kleinpell and Weaver, 1963, fig.; DeLise, 1967) .

TECUYA FORMATION

DEFINITION

The "Tecuya beds" of Stock (1920, 1932), later named the Tecuya 

Formation by Marks (1941, 1943) for Tecuya Creek, is a sequence of 

mainly nonmarine sedimentary and volcanic rocks exposed nearly 

continuously for 23 miles from east of Tunis Creek to west of Pleito 

Canyon (fig. 1 ) . The name Tecuya Formation is here adopted for this 

unit. The formation intertongues westward into the marine Pleito 

and Temblor Formations.

TYPE SECTION

The type section of the Tecuya Formation is designated as the 

crest of the first ridge west of Tecuya Canyon, 3 miles west of Grapevine, in the W% sec. 25, and E% sec. 26, T. 10 N., R. 20 W., San 

Bernardino base line and meridian, Grapevine 7 ^ -minute quadrangle :

Temblor Formation (lower part)

Thick-bedded to massive conglomeratic sandstone. 

Tecuya Formation: 

Upper unit:

Crudely interbedded red, green, buff, and blue-gray cobble

and pebble conglomerates, sandstones, and mudstones .............. 850

Volcanic unit:

Black fine-grained ophitic basalt and some scoriaceous basalt ...... 150

Pinkish-brown-weathering blue-gray dacite with small

phenocrysts of plagioclase in an aphanitic groundmass ............ 150

Lower unit:

Interbedded conglomerates, sandstones, and mudstones 

similar to those of the upper unit, including local breccias 

in the lower part .............................._................... ...... ... ............. 1,200

Approximate total (feet) ................................... ... ..... .............. 2,350

Tejon Formation (upper part):

Reed Canyon Silt Member of Marks (1943), renamed Reed Canyon 

Siltstone Member by Nilsen (1972):

Thin-bedded dark-gray siltstone and fine-grained sandstone 

with few marine megafossils.
H16 CONTRIBUTIONS TO STRATIGRAPHY

LITHOLOGY, THICKNESS, AND STRATIGRAPHIC RELATIONS

The Tecuya Formation is best exposed in Tecuya Canyon and in 

two smaller canyons to the west, where it is about 2,350 feet thick and 

consists of three units. The lower and upper units are composed of 

interbedded red, green, gray, and brown mudstones, siltstones, sandstones, and pebble and cobble conglomerates; the middle unit is composed of volcanic rocks. In the canyon west of Tecuya Canyon, the 

formation contains at the base a lens of granitic breccia, 150 feet in 

maximum thickness. This breccia was mapped by Hoots (1930) as a 

fault sliver of granitic basement, but we consider it to be more 

probably a landslide mass or other type of sedimentary breccia 

deposited when the Tecuya Formation began to accumulate in this 

area.

Near Tecuya Canyon the lower unit is about 1,200 feet thick. It 

consists largely of pebble to boulder conglomerates composed primarily of granitic and metamorphic clasts, including clasts of metavolcanic rock and quartzites, in a coarse sandy matrix. It rests with 

apparent conformity on both shallow marine sandstones of the San 

Emigdio Formation west of Salt Creek and the Tejon Formation east 

of Salt Creek. To the west, the lower unit intertongues into shallow 

marine sandstones of the Pleito and lower parts of the Temblor Formations near Salt and Pleito Canyons (fig. 3). The basal beds of the 

lower unit extend westward nearly as far as San Emigdio Canyon, as 

a thin nonmarine tongue between the Pleito and San Emigdio 

Formations.

East of Tecuya Canyon, the lower unit rests without discordance 

on the Tejon Formation, in places with a gradational contact, nearly 

as far east as Tunis Creek, where it rests on granitic basement. Harris 

(1950) measured 1,090 feet of the lower unit below the volcanic unit 

in Pastoria Creek and 450 feet near Tunis Creek; east of Tunis Creek, 

the lower unit laps out between the basement complex and the overlying volcanic unit. Interbeds of fossiliferous marine siltstone and 

sandstone have been noted by previous workers in the lower unit at 

several localities (Marks, 1941,1943; Harris, 1950).

The middle, or volcanic, unit is composed chiefly of flows of black 

locally scoriaceous basalt and dark-reddish-brown andesite with 

minor dacite (Marks, 1941; Harris, 1950). Near Tecuya Canyon the 

unit is 300 feet thick and consists of a lower subunit of dacite and 

dacite breccia and an upper subunit of basalt. Both subunits are 

laterally extensive, even though only 100-200 feet thick. West of 

Tecuya Canyon, the dacite thickens to about 500 feet, the basalt to 

about 1,500 feet near Pleito Creek. From there both subunits extend 

westward into the Temblor Formation, pinching out within 2 miles
SAN EMIGDIO AND TEHACHAPI MOUNTAINS, CALIFORNIA H17

farther west. East of Tecuya Creek, the entire volcanic unit thickens, 

from about 200 feet at Pastoria Creek to a maximum of 1,500 feet 

just west of Tunis Creek (Harris, 1950), where the lower part contains several beds of dacitic tuff-breccia. East of Tecuya Creek, it is 

unconformably overlain by, and in places completely overlapped by, 

the unnamed Miocene conglomerate. At Tunis Creek the volcanic 

unit rests directly on granitic basement.

The upper unit of the Tecuya Formation is lithologically similar 

to the lower unit and is present only in the Tecuya Creek area, where 

it is about 850 feet thick. It is missing west of some faults near Salt 

Creek and eastward from Tecuya Canyon is unconformably overlapped by the unnamed Miocene conglomerate. The upper unit is 

overlain by marine sandstones of the Temblor Formation and intertongues westward into the Temblor in Salt Creek Canyon.

DEPOSITIONAL ENVIRONMENT

The Tecuya Formation was probably deposited as a complex series 

of coalesced alluvial fans on a coastal plain by streams draining source 

areas to the east and southeast. The intertonguing of the terrestrial 

sediments of this formation into marine sediments to the west and 

also downdip to the northwest, as indicated from well data, defines 

a shoreline with a general northeasterly trend. A great variety of 

depositional environments is probably preserved along this nonmarine-marine boundary, with shoreline irregularities probably 

responsible for the irregular occurrence of marine sediments within 

the otherwise nonmarine Tecuya Formation. Climatic variations and 

tectonic movements probably provided varying amounts of sediments 

to the large alluvial fans, resulting in a shoreline that migrated or 

oscillated through time. The volcanic rocks were extruded probably 

from concealed nearby fissures or vents.

AGE

Previous workers have demonstrated that the Tecuya Formation 

ranges from Oligocene to early Miocene in age. It was assigned an 

early Arikareean (late Oligocene or early Miocene) age on the basis 

of mammalian remains found below the volcanic unit near Tecuya 

Creek by Stock (1920, 1932), Tedford (1961), and Stirton (1960, 

p. 362). The stratigraphic occurrence of the fossils (Stock, 1920) is 

in the middle part of the lower unit, which intertongues westward 

into probable late Oligocene mollusk-bearing strata of the Pleito 

Formation (fig. 3), rather than into the Vaqueros Formation 

(Temblor Formation of this report) as previously contended. Accordingly, these strata are probably coeval with strata assigned to the 

unnamed megainvertebrate stage of Addicott (1972).
HIS CONTRIBUTIONS TO STRATIGRAPHY

The stratigraphically higher parts of the Tecuya Formation, both 

above and below the volcanic unit, interfinger westward with the 

Temblor Formation, which carries molluscan assemblages referable 

to the "Vaqueros Stage" (fig. 3). This stage is coeval with the upper 

part of the Zemorrian and lower part of the Saucesian Stages of the 

provincial foraminiferal sequence (fig. 2). Marine mollusks reported 

by Marks (1941, p. 55) from 150 feet above the base of the Tecuya 

in a tributary of Tecuya Creek are not age diagnostic.

In wells drilled for oil located about 2 miles (Dibblee and others, 

1964) and 5 miles (Turner, 1970, p. 101) northwest of the exposures 

at Tecuya Creek, strata of the Temblor Formation that directly 

underlie and interfinger with the volcanic unit are of Saucesian age. 

Samples of the dacite from Pleito Creek and from between Tecuya 

and Grapevine Creeks have been radiometrically dated at from 21.5 

±0.7 million years to 22.3 ±0.7 million years by Turner (1970, p. 101).

If the Tecuya and Tejon Formations are in part equivalent in age, 

as postulated by Nilsen (1972), then the Tecuya Formation ranges 

in age from the late Eocene, "Tejon Stage" to the early Miocene 

"Vaqueros Stage."

TEMBLOR FORMATION

The Temblor Formation, formerly included in or mapped as the 

Vaqueros Formation (Pack, 1920; Wagner and Schilling, 1923; Hoots, 

1930) and in part as Pleito Formation (Dibblee, 1961, fig. 1), is a 

thick marine sandstone and shale unit traceable southeastward into 

the San Emigdio Mountains from the Temblor Range. It is continuously exposed west of lower Santiago Creek, where it is about 5,500 

feet thick; here it conformably overlies the Pleito (?) Formation and 

is overlain unconformably by the Monterey Shale. From lower Santiago Creek to the Devils Kitchen area, a thick-bedded to massive 

conglomeratic sandstone forms the basal part of the Temblor Formation, permitting it to be differentiated from the underlying Pleito 

Formation. Eastward, the Temblor thins to about 2,000 feet near 

Pleito and Salt Creeks, where it conformably overlies the Tecuya 

Formation and intertongues into the upper part of it. Southeastward 

from Santiago Creek to Brush Mountain, the Temblor Formation 

thins to 1,000 feet or less of coarse to pebbly sandstone and unconformably overlaps the San Emigdio and Tejon Formations onto the 

basement complex. These exposures contain several local lenses of 

probable extrusive porphyritic dacite, presumably coeval with those 

found in Pleito Canyon and eastward.

Mollusks from the basal sandstones of the Temblor Formation 

between Pleito and San Emigdio Creeks include the "Vaqueros
SAN EMIGDIO AND TEHACHAPI MOUNTAINS, CALIFORNIA H19

Stage" index species Macrochlamis magnolia (USGS loc. 13330). 

This species has also been reported from the marine tongue of the 

Temblor below the Tecuya volcanic unit east of Pleito Creek (Loel 

and Corey, 1932, p. 95). Mollusks from above the volcanic unit (Loel 

and Corey, 1932) are also referred to the "Vaqueros Stage." Doubtfully identified specimens of Leptopecten andersoni from near the top 

of the formation east of Pleito Creek (Dibblee, 1961, p. 14) suggest 

assignment of this part of the formation to the "Temblor Stage." The 

pectinid locality is overlain by Monterey Shale containing foraminifers of lower Relizian age.

Sparse data on foraminifers from exposures of the Temblor Formation indicate a generalized late Zemorrian (Kleinpell and Weaver, 

1963) to late Saucesian (Dibblee, 1961) age. In wells along the north 

margin of the San Emigdio Mountains, the Temblor Formation has 

yielded foraminifers diagnostic of the upper part of the Zemorrian 

Stage below the volcanic unit that extends into it from the Tecuya 

Formation and foraminifers diagnostic of the lower part of the 

Saucesian Stage from above the volcanic unit (Dibblee, 1961; Turner, 

1970).

MONTEREY SHALE AND UNNAMED CONGLOMERATE

The Monterey Shale is a marine thin-bedded siliceous and semisiliceous shale unit of middle and late Miocene age that conformably 

overlies the Temblor Formation (Dibblee, 1961). In the Temblor 

Range, northwest of the San Emigdio Mountains, the Monterey 

Shale is 7,000 feet thick; however, in the area of this report only the 

lower part, or that of Luisian and Relizian (middle Miocene) and 

possibly Late Saucesian (early Miocene) age, is exposed.

An unnamed nonmarine conglomerate is exposed in the foothills 

from west of Grapevine Canyon eastward to and beyond Tunis Creek. 

It is composed of coarse unsorted granitic detritus, including boulders 

in a weakly consolidated arkosic matrix. It rests with angular discordance on the Tecuya Formation, overlapping it onto the basement 

complex east of Tunis Creek; west of Tecuya Creek, it wedges out 

between the Temblor Formation and the Monterey Shale (Dibblee, 

1961). This conglomerate was assigned by Harris to the Temblor 

Formation (1950) and to the Olcese Formation (1954), but the 

assignment is not adopted in this report because the conglomerate 

is nonmarine. This unit presumably intertongues northward and 

westward into Miocene marine formations. The unnamed conglomerate probably was deposited as a complex of alluvial fans along a 

coastal plain fronting mountains to the southeast.
H20 CONTRIBUTIONS TO STRATIGRAPHY

SUMMARY

The lower and middle Tertiary sedimentary rocks of the San 

Emigdio and western Tehachapi Mountains record a series of marine 

transgressions and regressions, in which shallow marine sandstones 

and deeper marine shales of the western part of the area interfmgered 

eastward with nonmarine sediments. The depositional cycle began 

with the Tejon Formation, which accumulated during a major transgression from west to east across the area from early to late Eocene 

time (Nilsen, 1972). The transgression was followed by a westward 

regression and deposition of the San Emigdio and Pleito Formations 

on a shallow marine shelf that deepened westward and northward in 

Oligocene time. Nonmarine fluvial strata of the Tecuya Formation, 

probably derived from land areas to the east or southeast, were 

deposited during that time as alluvial fans fringing the shallow marine 

shelf. Climatic and tectonic changes affected the supply of sediments, 

resulting in a migrating and oscillating shoreline. Eruptions of dacite 

and basalt lava flows covered the terrestrial area extensively during 

late Oligocene and early Miocene time and flowed partly onto the 

marine shelf. These probably erupted from fissures, now presumably 

covered by the flows. Similar dacites were erupted penecontemporaneously in the Brush Mountain area.

The sharp, angular unconformity between the Temblor Formation 

and the underlying Tejon and San Emigdio Formations in the Brush 

Mountain area (fig. 2) indicates that uplift and erosion occurred 

locally during late Oligocene time. This uplift must have been contemporaneous with deposition of the Pleito Formation to the north. 

If the San Emigdio Formation is also unconformable on the Tejon in 

this area, then some uplift may have occurred even earlier. The late 

Oligocene activity was followed by volcanic eruptions in the Brush 

Mountain area and further east and by later uplift in the Brush 

Mountain area prior to deposition of the Monterey Shale.

Tipton (1971), in a study of subsurface late Eocene and Oligocene 

sedimentary units in the southeastern San Joaquin Valley, suggested 

that the major source of the Oligocene sediments was to the south, 

toward Santiago Creek in the San Emigdio Mountains. This implies 

that at least two major sources for Oligocene sediments were present 

 the Sierra Nevada, Tehachapi, and Mojave Desert regions to the 

east and southeast and the San Emigdio or other adjacent provenance 

areas to the south. Subsequent right-lateral movement along the San 

Andreas fault may have displaced this southern source area many 

hundreds of kilometers to the north, so that it may not be easily 

recognized today. The large thickness of Oligocene sedimentary rocks 

in the area north of Brush Mountain suggests that this part of the
SAN EMIGDIO AND TEHACHAPI MOUNTAINS, CALIFORNIA H21

basin subsided contemporaneously with uplift to the south. Tipton 

(1971) concluded that Oligocene sedimentary rocks further north 

were deposited in deep water, indicating that this part of the basin 

remained deep from Eocene through Oligocene time. The tectonic and 

volcanic activity in the Brush Mountain area and the uplift of southern source areas of Oligocene sedimentary rocks were no doubt the 

local effects of widespread Oligocene diastrophism and volcanism that 

affected much of central and southern California and climaxed in late 

Oligocene time.

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H22 CONTRIBUTIONS TO STRATIGRAPHY

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U.S. GOVERNMENT PRINTING OFFICE: 1973 SIS 658/56