Structural Evolution of the Russell Ranch Oil Field and Vicinity, Southern Coast Ranges, California

Home , Caliente Range, South Cuyama Oil Field

AN ABSTRACT OF THE THESIS OF

Barbara B. Nevins for the degree of Master of Science in Geology presented on December 14, 1982

Title: STRUCTURAL EVOLUTION OF THE RUSSELL RANCH OIL FIELD AND

VICINITY, SOUTHERN COAST RANCES-(ALIFORN

Abstract approved: Signature redacted for privacy. ' D. Robert(SA Yeats

The Russell Ranch oil field is located in the southern Coast

Rangeswest ofBakersfield, California. Detailed subsurface mapping shows that a northwest-oriented right-lateral wrench-fault system was active from possibly latest Oligocene to Pliocene time.

The effects of Quaternary thrusting were superimposed on, and influenced by, structures associated with the older wrench tectonic regime. The right-lateral shear system produced a complex pattern of right-stepping en echelon folds, dip-slip faults with normal separation, and strike-slip faults with both normal and reverse separation. Deformation along the wrench system began during deposition of the late Oligocene-earlv Miocene Soda Lake Shale and

Painted Rock Sandstone members of the Vaqueros Formation, pro- duciu elongate en echelon submarine troughs and highs. Northerly trending growth faults of early Miocene age caused thickening of the late Saucesian-early Relizian Saltos Shale Member of the

MontereyFormation and mayhave initiated growth of the Russell

Ranch anticline. Northeast- to northwest-trending normal faults and northwest-trending strike-slipfaults ofthe Russell fault system were active during deposition of a sequence tentatively correlated with the Branch Canyon Sandstone and Santa Margarita

Formation of middle and late Miocene age. Strike-slip faulting produced a complex interleaving of fault slices and juxtaposed slices of contrasting lithologies and orientations. Subsequent minor movement along the wrench system folded the base of the

Morales Formation, of PJ.iocene-Pleistocene age, into elongate en echelon folds.

The north-dipping Whiterock and Morales thrusts brought

Miocene and younger strata southward over deposits as young as late Pleistocene. The Whiterock thrust changes southward from a southeasterly to an easterly strike. The upper plate was thrust southward, and structures in the lower plate apparently controlled the geometry of the developing fault plane. The thrust ramps as it overrides the normal and strike-slip faults of middle Mb- cene age; rootless folds similar to those found in the Caliente

Range are present in the upper thrust plate above the tectonic ramps.

Wrench-related faulting in the Cuyama basin predates similar movement along the San Aridreas fault to the northeast and may represent a strand of the proto-San Andreas fault. Quaternary thrusting in the basin was influenced by and now obscures the structures of the older wrench fault system; thrusting activity was probably contemporaneous with thrust faulting in the Trans- verse Ranges to the south. STRL'CTUPAL EVOLUTION OF THE RUSSELL RANCH OIL FIELD AND VICINITY, SOUTHERN COAST RANGES, CALIFORNIA

Barbara B. Nevins

A THESIS

submitted to

Oregon State University

in partial fulfillment of the requirements for the degree of

Master of Science

Completed December 14, 1982

Commencement June 1983 ACKNOWLEDGEMENTS

Robert S. Yeats acquainted me with Cuyama Valley and was available for guidance and advice thoughout the study. William

J. M. Bazeley of Arco Exploration Company was instrumental in the origination and continued support of the project. T. W. Dibblee,

Thom Davis, and Ernie Duebendorfer generously provided their unpublished geologic maps of the area; Thom Davis also provided many enlightening field trips and discussions. Hans F. Schwing of Oregon State University shared the terrors of dodging killer snakes and spiders in the field, and never tired of discussing

Cuyama Valley geology. Isabelle and Lamar Johnston generously gave me a home in Cuyama Valley during the summer of 1980. Karla

Urbanowicz helped construct many cross-sections, and Edwin Howes deserves a special thanks for his excellent drafting and his once strong nerves.

I would especially like to thank Alan R. Wallace, whose support and encouragement were overwhelming and unending throughout this endeavor.

This project was funded under National Science Foundation grant EAR-802227l. Atlantic Richfield Company provided support for field work during the summer of 1980. TABLE OF CONTENTS

Page

INTRODUCTION 1 Geologic Setting I Methods 6 Previous Work 7

STRATIGRAPHY 9 General Statement 9 Crystalline Basement Complex 14 Unnamed Pre-Oligocène Marine Sedimentary Sequence 15 Siimnler Formation 17 Vaqueros Formation 19 Quail Canyon Sandstone Member 19 Soda Lake Shale Member 21 Painted Rock Sandstone Member 22 Monterey Formation 23 Saltos Shale Member 23 Whiterock Bluff Shale Member 24 Branch Canyon Sandstone 26 Santa Margarita Formation 27 Branch Canyon Sandstone-Santa Margarita Formation, 29 undifferentiated (BCSM) Morales Formation 30 Alluvium 32

STRUCTURE 34 General Statement 34 Pre-Caliente Range Structures 34 Vaqueros Age Deformation 36 Cox-type Faults 38 Russell Fault System 39 Morales Age Deformation 45 Caliente Range Faults 46 Whiterock Fault 47 Morales Fault 53

GEOLOGIC HISTORY 55

CONCLUSIONS 61

REFERENCES CITED 64 LIST OF FIGURES

Figure Page

1. Index Map of California 9

General index map of the Cuyama basin 3

Generalized geologic map of the Cuyama basin 5

Generalized stratigraphy of the Cuyama basin 10

Composite type electric log for the Russell Ranch 11 oil field, lower plate of the Whiterock fault

Composite type electric log for the Russell Ranch 12 oil field, upper plate of the Whiterock fault

Pre-Vaqueros subcrop map with isopachs of the 13 Simmler Formation

Tectonic map of the Cuyama Valley 35

Stratigraphic correlation section of the 37 Vaqueros Formation

Diagrammatic map of the facies boundary between 42 Branch Canyon Sandstone and the Monterey Formation

Diagrammatic cross section of rootless folds 50 produced in thin-skinned tectonics

Structure contour map of electric log marker 21 51 in the Saltos Shale Member of the Monterey Formation, upper plate of the Whiterock fault LIST OF PLATES

Plate Pocket

I Well base map and cross section locations

II Well base map of Russell Ranch oil field and cross section locations

III Geologic map of the Russell Ranch area

IV Isopach map of the interval from electric log marker 25 in the Saltos Shale Member to the base of the Vaqueros Formation

V Cross section A-A'

VI Cross section B-B'

VII Cross section C-C'

VIII Cross section D-D'

IX Cross section E-E'

X Cross section F-F'

XI Cross section c-c'

XII Cross section H-H'

XIII Cross section I-I'

XIV Structure contour map of electric log marker 25 in the Saltos Shale Member of the Monterey Forma- tion in the Russell Ranch oil field

XV Structure contour map of the Russell fault

XVI Structure contour map of the base of the Morales Formation showing paleogeography

XVII Structure contour map, of the Whiterock fault STRUCTURAL EVOLUTION OF THE RUSSELL RANCH OIL FIELD AND VICINITY, SOUTHERN COAST RANGES, CALIFORNIA

INTRODUCTION

The Russell Ranch oil field is one of two major fields in the

Cuyama basin in the southern Coast Ranges between Bakersfield and

San Luis Obispo, California (Figs. 1 and 2). Recent attempts to extend the oil fields have been unsuccessful, perhaps in part due to an inadequate understanding of the complex structural and stratigraphic relations in the Cuyama basin.

The Cuyama basin is part of the southern Salinian block, a terrane west of the San Andreas fault and east of the Sur-Naci- miento fault, north of the Transverse Ranges province. Older structures in the Cuyama basin reflect strike-slip faulting, which is characteristic of the Salinian block, whereas younger structures resemble the Transverse Ranges in both orientation and reverse- fault style. A better understanding of the structural style and deformational history of the Russell Ranch oil field serves two purposes: (1) to aid future petroleum exploration in the Cuyama region, and (2) to contribute to the understanding of the neotec- tonic relation of the southern Salinian block to both the Trans- verse Ranges and the San Andreas fault.

Geologic Setting

The Coast Ranges of California, characterized by northwest- trending right-slip faults, are truncated to the south by the 2 Figure1. Index map.

0 T -N

(S' 0 ' -v

Figure 2 Figure

Bakersfield N0 'L. Mojave Desert

34°N '0 Little Los n Bernardino Angel Mountains

'-p

0 00 200 300 Km

100 200 Mi

24° 1200 116°W \ 20° N 90 /1 N N GREAT VALLEY FRAER GABRIEL AN RANGE FAULT N 'V 44 LAKE,satu RRIZO - . 7 CHIMEN N - V / AP.CJI Ails CuycL? hr. uA FAULT PAN7A RANGE souTh kii. IL 7k A0 s Figure 2. Tectonicthe Cuyama Map of Basin. SIJRNACIMIENTO _____!E RNGE SAN RAFAEL MTNS St rike-slip F Dotted aultwhere R eversecovered Fau SCA I. E Jo CALIFORNIA 0 o JO 20 Kin 20 Anticline / Orolano ii LdwJn ft. Howt$ 20° 4

Transverse Ranges province which is dominated by west-trending reverse faults. The Cuyarna basin is located in the southern Coast

Ranges and lies near the boundary between the two structural prov- inces (Figs. 1 and 2).

The Salinian block, located in the southern Coast Ranges, is characterized by gneissic and granitic basement. In contrast, the basement rocks of the Coast Ranges east of the San Andreas fault and west of the Sur-Nacimiento fault consist mainly of the Franciscan Formation. The Cuyama basin, located in the southern Salinian block, was filled by a succession of sedimentary units of middle to late Cenozoic age which overlapped both a pre-

Oligocene sedimentary sequence and the crystalline basement (Fig.

3). The north-northwest-trending Russell fault transects the

Cuyama basin and is probably the southeastern extension of the

Red Hills-San Juan-Chimeneas fault system to the northwest

(Schwade et al., 1958; Bartow, 1974). This fault system inter- sects the San Andreas fault north of Red Hills and separates granitic terrane on the west from predominantly gneissic terrane on the east (Ross, 1978).

The present-day Cuyama Valley transects the Cuyama basin with a slightly north-of-west trend which is similar to orientations in the Transverse Ranges. The Caliente Range was thrust southward along the riorth-dipçing Whiterock, Morales, and Caliente Mountain faults and forms the northeastern boundary of the valley. The

Sierra Madre Mountains, which form the southwestern boundary of the valley, were thrust northward along the south-dipping South Qol Figu'e 3 Generalized(Modiliod Regional ((010 Geotogic JOiLnIfl.J1 andMap Sirand,orici l969 Jennings. 1958.59.) the Guyarna Basin Area. Sntitt., 1964 of Reverse louts,dottedconcealed whore Syricline f Gal Sl,ike - slip bolldulled where , NonmorineRecer,t alluvial deposits, deposits surface I concealed a5 Nonmarine deocits,Pliacenepreserved; deformed and Pleistocene Pleistocene 090. ['age. Sodi nentory rocks of Miocene age, Ne Cuyuno Qronsh Canyon Gal > local igneous (tows ond inlrusia'io McMiii 000morinemarine - South Cuyoma Y% Mb basall sill :..k.:i,.f J. 'Lft Oil Field . 8ortoroSonic. Nonmarine sedimentaryOtiçocene rocks age. of C. (.i. f. r Locone andMurinb Paleocene sedimeniary age. rocks of Qal> tj Marine) sedimentary rocksGncislc RockCrelacecos age, aEtt%%l ( I ole f-n 6

Cuyama and Ozena faults.

Methods

The subsurface geology of the Russell Ranch area was mapped in detail and integrated with the surface geology in order to determine the geological history of the study area. The study area includes 290 wells in and around the Russell Ranch oil field

(Plates I and II). Well data include electric logs, directional surveys, dipmeter logs, lithologic descriptions of core, sidewall, and ditch samples, and paleontological reports. The engineering report for unitization of the field (Core Laboratories, 1960) provided information on oil-water contacts in the producing zone.

Cross sections (located on Plates I and II), structure contour maps of key horizons, and isopach maps were constructed to delineate the subsurface geology. Fifty-eight cross sections were constructed, nine of which are included in this report.

Surface mapping of the study area by T. Dibblee (unpublished 15- minute quadrangle maps) and T. Davis and E. Duebendorfer (unpublished data) were used for surface control (Plate III). Surface exposures of relevant units were examined in and around the study area to familiarize myself with the lithologies and with regional stratigraphic and structural relationships.

The base map (1:24,000) used in this report is from the

Caliente Mountain, New Cuyama, Peak Mountain, and Wells Ranch

U.S.G.S. 7.5 minute topographic quadrangles. Surveyed section lines are not shown in land grant and some National Forest areas. 7

I projected surveyed section lines to establish the section corners in these unsurveyed areas. Therefore, the projected section corners in this report may not match projections made by various oil companies.

Previous Work

The first extensive geological reports of the Cuyama region were published by English (1916), Eaton (1939), and Eaton et al.

(1941). The discovery of oil in Cuyama Valley in 1948 led to publications on the areal geology and stratigraphy, including those by Schwade et al. (1958) and Hill et al. (1958). The stratigraphic nomenclature of Hill et al. (1958) stands today with only slight modification by Dibblee (1973b). The California

Division of Oil and Gas issued several reports on the.. geology of the oil fields, including that by Barger and Zulberti (1952) on the Russell Ranch oil field. A regional subsurface study was published by Cross (1962).

Topical studies in the Caliente-Cuyama region are numerous.

Sedimentological studies include Madsen (1959) in Salisbury

Canyon in the southeastern Cuyama Valley; Chipping (1970, 1972) on the pre-Oligocene marine sedimentary sequence in the La Panza,

Santa Lucia, and Sierra Madre Ranges; Bartow (1974, 1978) on the

Simmier and Vaqueros Formations; Clifton (1967, 1968, 1981) on the Branch Canyon Sandstone and Caliente Formation on the north side of Caliente Mountain; and Fritsche (1969) on the Miocene sedimentary rocks of the Sierra Madre Mountains. Biostratigraphic studies include Cower et al.(1966), Vedder et al. (1967), and

Vedder and Brown (1968) in the northern Sierra Madre, southern

Santa Lucia, and La Panza Ranges; Vedder (1973) in the Caliente

Range; Phillips (1976) on the Whiterock Bluff Shale Member of the

Monterey Formation; and Lagoe (1981, 1982) on the Saltos Shale

Member of the Monterey Formation. Biochronological studies in- dude Repenning and Vedder (1961) on vertebrate-invertebrate correlations in the Caliente Range. Studies on radiometric dating of Miocene basalts include Turner (1970). Tectonic studies include Suppe (1970), Huffman (1972), Dibblee (1976), Smith (1977), and Craham (1978). Studies on the crystalline basement rocks in the region include Ross (1972, 1974).

The U.S. Geological Survey published maps (1:24,000) for the eastern part of the Caliente region (Vedder and Repenning, 1965,

1975; Vedder, 1968, 1970) and a regional geological map

(1:125,000) by Dibblee (l973a). T. W. Dibblee, Jr. (1:62,500) and T. Davis and E. Duebendorfer (1:24,000) prepared unpublished geological maps of the western portion of the Cuyama region. 9

STRAT IGRAPHY

General Statement

The granitic and gneissic rocks which form the basement of the southern Salinian block are overlain by strata of pre-Oligocene to Holocene age. The generalized stratigraphy of the Cuyama basin is shown on figure 4. Typical electric logs for both the hanging and footwall blocks of the Whiterock fault in the Russell Ranch oil field are shown in figures 5 and 6.

Crystalline basement is encountered only in the northeastern- most part of the study area (Fig. 7), where it is overlain by the

Vaqueros Formation of Oligocene to Miocene age. Throughout the remainder of the study area a marine sedimentary sequence of pre-

Oligocene age is the oldest unit penetrated; presumably it overlies crystalline rocks at depth. The terrestrial Simmier Forma- tion of Oligocene age unconformably overlies the older marine strata to the east, west, and within the study area, and it overlies crystalline basement to the north. The marine Vaqueros For- mation of late Oligocene to early Miocene age conformably overlies the Simmier Formation in the Caliente Range and, locally, west of the Russell fault. Elsewhere, the Vaqueros Formation unconformably overlies the pre-Oligocene marine sequence. The early to middle Miocene marine Monterey Formation conformably overlies the

Vaqueros Formation. The marine Branch Canyon Sandstone grades laterally westward into and, in a limited area, conformably overlies the Monterey Formation. The marine Santa Margarita Formation SExIESFJ'tsdn/ STAI.ES roI(An. Figure 4. sT\(:Es MLI.. Generalized strat:igraphyM(KrIIwI:Sr CAl. of I LUtEthe t Cuyamau Basin (from Lagoe, 1982). RAN;ES CLNTRM. ANn CMJENTI; RANGE )UTHEAST CUYMA VA! IFY SIERRA MAURE RANC FLLO.EN. t1OtIAN POT- PASO RO8LE FM, MORALES FM. MORALES FM. MORALES FM. MONNIAN ii --- SANTA MARGARITA FM. SANTA SANTA SANTA RITAN" MARGARITA FM. --. / / MARGARiTA FM. / / / MARGARITA FM. / / / Id LIJISIAN MONTEREYFORMJ1TIO1 SANDSTONEIIRANCH z MONTEREY FM oz o RELiZ1AN I. SLOR" ----- 0 0 ° . a. MONTEREY VAQUEROS OR}tATION FM. If E51AN $'IiApIt 1 VAQUEROSFORIIATION FORMATIONVAQUEROS FORMATIONVAQUEROS CENEOLICO- RLANZEHOR- .11 SIMMLER FM. SI!'QILF.R FM.. SIIIMLER FM. SIMMIER' FM. /LHOR- PRE- CR STAt LI ROCKS I'AI(;RETACEOUS-ROt HH'FNE KS LIERUt'S . CRFTACLOLJS-ROCKSPAl COGFNF . PAlCRETACEOUS-N'CKS FO( FE II

Figure 5. Composite Type Electric log for the Russell Ranch Oil Field, Lower Plate of the White rock Fault.

BENTHIC (Electric-log intervals fromRussell 25-9, 200'-2720; PERIOD AGE FORAM Russell 65-9, 2720-3720; and Russell4_3l, 3720- STAGES 4730'; vertical scale in feet.)

BARBARA B, NEVINS OREGON STATE UNIVERSITY 1982

Morales Formation, Tmo, - interbedded satdstone, buff, red-brown, and green-gray, poorly sorted,very fine- to coarse-grained, pebbly, siltstone and clystone,brown to green-gray.

- ? 9 ??---?-9 L. - Branch Canyon Sandstone-Santa Margarita Fm., undiff.,Tbs, sandstone, white to light gray and green-gray, medium- to coarse- 20- graieed, pebbly; common interbeds of siltstone, green-gray.

z Branch Canyon Sandstone,Tbc, sandstone, gray, floe- to coorse-grained, massive, minor sittstone. -J

z S n-A xi-J Saltos Shale Member of the Monterey Formation, Tsa, Ui siltstone, dark brown, laminated to massive; m1nor interbeds of z sandstone, gray, very fine-groir.ed to silty; abundant foraminifera Ui 0 and fish remains; rare carbonaceous material. 0

>Selected Electric-log Markers

4 Painted Rock Sandstone Member,Tpr, (Dibblee sand), sandstone, light to medium gray, fine- to medium-gra;ned,silty; minor fossiliferous beds in upper part; common siltstone interbeds, gray, in lower part. Vaqueros Formation

Soda Lake Shale Member, Tsl, (Coigrove shale), siltstone, dark brown to gray, massive to ploty; abundant foraminifera and fish remains, minor interbeds of sndstOnS. xi 0 n-A uoan flan. to e ,(r9ve saft. , sandstone, dark gray to gray, Unnamed Pre-Oligocene Marine fine- to medium-grsived, Sedimentay Rocks, Tu, silty, massive; local interbedded sandstone, gray to dark gray, pebble and gravel lenses. fine- to medium-grained, very hard, biotitic and siltstone,dark gray to black, brittle, micoceous; abundant carbonaceous material and pyrite; minor conglomerate,subrounded, tine-grained igneous, quartzite, dark red sandstone cobbles, sandstone matrix. Drafting by Edwin R. Nouns Figure 6. Composite Type Electric log for the Russell Ranch 12 Oil Field. Upper Plate of the Whiterock Fault. (Electric-log intervals from: Russell 177-25, 200'-2 190' and Wood- Callahan 22A-25, 2190'-3700'vertical scale in feet.)

BARBARA B. NEVINS BENTHIC OREGON STATE UNIVERSITY PERIOD AGE FORAM 1962 STAGES

Morales Formation, Tmo, I interbedded gravel3 sandstone, buff and blue-gray, poorly [ sorted, fine- to coarse-grained, silty, pebbly and claystone, gray to buff. O5 -MU Santa Margarita Formation,Tsm, sandstone, white to light gray, fine- to coorse-grained, pebbly, kaolinitic, minor claystone, blue-gray; and siltstone interbeds, dark green-brown to black, sandy,fish remains.

- §6Whiterock Bluff Shale Member of the Monterey - Formation, Tmw, IS siltstone,dark brown, laminated to massive; abundant foraminifera and fish remains.

20 zLU 60 LU Selected Electric-lag Markers 0

z - -14 N 25 -J Ui Saltos Shale Member of the Monterey Formation,Tsa, - siltstone, dark brown,Iaminoted to massive; abundant foram- nifero and fish remains; minor interbeds of sandstone,gray,

17 fine-grained,silty. 30 -21

-25

35 Painted Rock Sandstone Member of the Vaqueros Formation,Tpr,(Dibblee sand), sandstone, light to dark gray, fine- to mediuni-grained, silty, massive to poorly bedded; abundant megafossils, uncommon fish remains. Drafting by Edwin R.Howes 13

N- C\JC'J Figure 7. Pre-Vaqueros Subcrop Map with Isopachs of the Simmier Formation. 5 14 013 18 A

0 Strike-slip Fault A Contour Line, Interval 500 Feet

S F \ Wells Reaching Simmler Format ion 24 20 0 50? 0 Wells Reaching Pre-Oligocene Sedi- \\ mentary Sequence, Not Encountering Simmier Formation 23 N,. 0+ 0 o .2 \\ Wells Reaching Crystalline Basement, F '.800 Not Encountering Simmler Formation jS\ 25 '\ 30 \ \\ \ \\\\ N 26 00 ) 25 \\\ 0 "31 30 \ \ 29 "450 0 \\ F + ± - 32 33 00 \ 0 \ S\\\0\\ 2OO? 0 35 36 \\ 3l 32 / \ \ 33 0\\ \ j IN ± \ + ± I ION \\ Russell Ranch \\\.___Oil Field \\(, 4 0 I 2 3 45000Ft. 6 \\ \\ 0 1/2 I Mile \ ---.-- \ \\\ \ \\\\ ± \ '.330. LOCATION MAP \ \ 0 7 \\\\8 ) 0 Russell Ranch \ Oil field 0 \ -1 'ç ± -"-

18 17 16

L 14 of middle and late Miocene age conformably overlies both the

Branch Canyon Sandstone and the Monterey Formation. East of the study area, Oligocene through Miocene marine strata intertongue to the east with the non-marine Caliente Formation. Non marine deposits of the Pliocene-Pleistocene Morales Formation and Pleis- tocene to Recent alluvium unconformably overlie the Miocene strata.

Crystalline Basement Complex

The crystalline basement in the study region may be divided into the granitic rocks of the La Panza Range and the gneissic rocks of Barrett Ridge. The boundary between these two crystalline terranes is the Red Hills-San Juan-Chimeneas (Russell) fault trend (Ross, 1972, 1978).

Medium-gray granodiorite and quartz monzonite are widely exposed in the La Panza Range. Rb/Sr and U/Pb data and Campanian fossils in overlying sedimentary rocks elsewhere in the Salinian block indicate an Early Cretaceous age for emplacement of the crystalline rocks (Compton, 1966). Therefore, a K-Ar date of about 80 m.y. from the La Panza Range (Curtis et al., 1958;

Evernden and Kistlér, 1970) probably reflects a post-emplacement event (Ross, 1972), probably cooling of the unit as it was up- lifted.

At Barrett Ridge, northeast of the Chimeneas fault, strongly foliated quartzo-feldspathic gneiss is associated with alaskite intrusions, biotite-rich gneiss, biotite schist, hornblende schist, and small lenses of quartzite (Ross, 1972). Strontium isotope 15 data onrocks of the Barrett Ridge indicate that these rocks are

- . 87 86 either of a ditferent age or different initial Sr /Sr (ri) ratio than other crystalline rocks of the Salinian block (Kistler et al.,1973). The Barrett Ridge gneiss may correlate 'with lithologically similar rocks of Precambrian age in the San Gabriel

Mountains.

In the subsurface, crystalline basement is rarely penetrated in the study area. Several exploratory wells east of the Russell fault and east of the oil field, (Mackie 1, Rohmer 1, and Luce 1 wells; cf. Plate I), bottom in crystalline rocks. Core and ditch sample descriptions indicate that the rock is composed of a dark gray granite in the Mackie 1 well, a black granitic gneiss in the

Luce 1 well, and a dioritic gneiss in the Rohmer 1 well; these rocks are presumably correlative with the gneissic rocks of

Barrett Ridge.

Unnamed Pre-Oligocene Marine Sedimentary Sequence

A sequence of marine sedimentary rocks is widely exposed in the La Panza, southern Santa Lucia, and Sierra Madre ranges. The sequence overlies granitic basement in the La Panza and Santa

Lucia Ranges and is30,000feet thick, but the base of the sedimentary sequence is not exposed in the Sierra Madre Range. This sequence of rocks is composed dominantly of arkosic sandstone interbedded with buff to gray shale and siltstone, together with conglomerate which contains clasts of volcanic, granitic, and metamorphic rocks. The sequence dips regionally to the southwest. 16

Although Chipping (1970, 1972) divided the thick marine sequence of the three ranges into several local lithogenetic units, the

lithologic monotony of these rocks precluded a more formal differ- entiation in the study area. Dibblee (1973b) considered the marine sequence to be a deltaic deposit, but Chipping (1972)

interpreted it to be composed of turbidites and fluxoturbidites.

The Pattiway Formation of Hill et al.(1958), exposed in the

southeastern Caliente Range and determined to be of Paleocene age by Vedder and Repenning (1965), may be an eastward extension of

the marine sequence of the La Panza and Sierra Madre Ranges

(Dibblee, 1973b).

This sedimentary rock sequence was mapped and described by

previous workers (Eaton et al., 1941; Hill et al., 1958; Jennings,

1958) as Late Cretaceous in age. Subsequent work shows that this

sequence ranges from Late Cretaceous to middle Eocene in age

(Gower et al., 1966; Vedder et al., 1967; Vedder and Brown, 1968).

In the subsurface of the study area, up to 1,800 feet of this

marine sequence were drilled without reaching its base. The

greatest penetration was reached in the Arco Russell 82-26 well.

The sequence is characterized in the subsurface by interbedded

gray to dark gray, hard, biotitic sandstones and siltstones which

contain abundant carbonaceous material. Associated conglomerate

contains cobbles of quartzite, sandstone, volcanic, and granitic

rocks. Although Hill et al. (1958) reported the presence of

Siphogenerino-ides whitei, a diagnostic foraminifera of Late Cre-

taceous age, from "a few well sections" in Cuyama Valley, no age- 17 diagnostic fossils were identified in paleontological reports made available to rae from wells in the study area. This sequence is referred to as the "Cretaceous of Cuyama" in most oil reports.

It is, however, possibly as young as Eocene, based on the early to middle Eocene age of this sequence in the Sierra Madre Range

(Gower et al., 1966; Vedder et al., 1967). Dipmeter and core dips indicate that the contact with overlying strata is an angular unconformity.

Siminler Formation

At the type locality in the southeastern Caliente Range, the

Siramler Formation of Hill et al. (1958) is a 3,000-foot thick terrestrial deposit that overlies the Pattiway Formation. The

Siramler Formation unconformably overlies and overlaps cr.ystalline basement at Barrett Ridge and the pre-Oligocene marine sequence in the Cuyama Gorge and La Panza Range (Bartow, 1974). At the type area the Situmler Formation is composed of red to greenish- gray sandstone and siltstone, and a local basal conglomerate.

The Simmier Formation is composed of a sandstone unit and a conglomerate unit (Bartow, 1974, 1978). The sandstone unit appears to be restricted to areas northeast of the Morales and Big

Spring thrust faults, and it attains a maximum thickness of 3,800 feet (Vedder, 1973). The conglomerate unit occurs to the southwest of these faults and ranges in thickness from 0 to 600 feet

(Bartow, 1974). Cross (1962) suggested that the conglomerate unit accumulated in local pockets on an irregular erosional 18 surface, whereas Bartow (1974) indicated that these deposits accumulated in re-entrants along the basin margin. In the subsurface of the study area, the Simmier Formation, identified on the basis of its red color, is erratic in both thickness and distri- bution (Fig. 7). The unit reaches a maximum thickness of over

800 feet in the Arco Indian 3 well and pinches out less than half a mile to the east, consistent with the suggestions of either

Cross (1962) or Bartow (1974). In the study area, the formation consists of both conglomerate and sandstone. The conglomerate, the dominant lithology, is composed of cobbles of dark gray sandstone, tan siltstone, chert, and plutonic rocks, with a matrix of light to dark red, poorly sorted sandstone. The Simmier Forma- tion overlies pre-Oligocene marine strata, as observed in the

Indian 4 and Marilyn 1 wells.

The conglomerate unit of the Simmler Formation was originally mapped as the Redrock Canyon Sandstone Member of the Santa

Margarita Formation by English (1916), the non marine Vaqueros

Formation by Eaton et al. (1941), the Sespe Formation by Clements

(1950), Oligocene(?) redbeds by Vedder and Brown (1968), and the

Situmler Formation by Hill et al. (1958) and Dibblee (l973b).

The Simmler Formation is unfossiliferous, with the exception of rare plant fragments, very rare bone fragments, and a few ostracods reported from a well near Soda Lake. The formation is tentatively assigned an Oligocene age on the basis of its uncon- formable relationship with the underlying units, its conformable contact with the overlying Vaqueros Formation of Oligocene and 19

early Miocene age, and its intertonguing relationship with the

Vaqueros Formation in the La Panza Range (Bartow, 1974).

Vaqueros Formation

The Vaqueros Formation (Hill et al., 1958) was named for the

widely exposed marine sandstone, siltstone, and shale which con-

formably underlie the Monterey Formation in the Caliente Range.

In the Cuyama basin, Hill et al. (1958) divided the formation into

three members; in ascending order, these are the Soda Lake Sand-

stone, Soda Lake Shale, and Painted Rock Sandstone. Dibblee

(l973b) renamed the lower sandstone the Quail Canyon Sandstone.

In the Cuyama basin, the Vaqueros Formation conformably

overlies and overlaps the discontinuous Simmler Formation to

cover the pre-Oligocene marine sequence with angular unconformity.

The thickness of the Vaqueros Formation varies widely across the

basin. In the Caliente Range the unit is as thick as 7,000 feet.

South of the Caliente Mountain fault, the formation ranges in

thickness from 1,800 feet southeast of the Russell Ranch oil field

to less than 1,000 feet within the oil field (Plate IV).

Quail Canyon Sandstone Member

At the type locality in the southeastern Caliente Range this

member consists of 300 feet of light gray to white, fine- to

medium-grained, firmly indurated, cross-bedded sandstone (Hill et

al., 1958). Abundant mollusks and thin lenses of pebbly sandstone

occur locally. The unit conformably overlies the Simmler Forma- 20 tion and grades both upward and westward into the Soda Lake Shale

Member (Hill et al., 1958). There is no evidence, however, in the subsurface of either this study area (Fig. 9) or the South Cuyama oil field (Schwing, in 'prep.) which suggests lateral gradation to the Soda Lake Shale. To' the contrary, Schwing (in prep.) presents evidence which suggests that the contact between the Quail Canyon

Sandstone and the overlying Soda Lake Shale is an unconformity.

In the Caliente Range, the Quail Canyon Sandstone contains sparse mollusks diagnostic of "Vaqueros age" (provincial early to middle Miocene) (J. G. Vedder in Dibblee, 1973b; Vedder and

Repenning, 1975) and it underlies a siltstone unit which contains both "Vaqueros Stage" mollusks and Zemorrian Stage foraminif era

(Hill et al., 1958) now considered to be of late Oligocene age

(Poore, 1980). Based on this evidence, the Quail Canyon Sandstone is considered to be Oligocene in age. It was deposited as a basal transgressive sand in a high-energy, shallow-marine environment

(Bartow, 1974, 1978).

In the subsurface of the study area the Quail Canyon Sand- stone ranges in thickness from 0 to over 100 feet. Thickness variations in the sandstone appear to be related to pre-Vaqueros topography (Fig. 9). The unit is composed of gray to dark gray, silty, fine- to medium-grained, massive sandstone, with local pebble and gravel lenses. This sandstone is called the Coigrove sand in the subsurface, and it is a productive oil sand in the northwestern part of the Russell Ranch field. 21

Soda Lake Shale Member

The Soda Lake Shale Member is 1,225 feet thick at the type section near Soda Lake in the northwestern Caliente Range (Hill et al.., 1958). At this locality, the Quail Canyon Sandstone Member is absent, and the shale unit conformably overlies the Simmier

Formation. The shale member is composed of dark gray to grayish- brown, hard siltstone, platy concretionary shale, interbeds of brown, hard, thin turbidite sandstone, and a tan and light gray to green, hard, chert bed which occurs approximately midway through the unit. The Soda Lake Shale Member contains diagnostic foraminifera of the Zemorrian Stage (late Oligocene) below the chert bed and foraminifera diagnostic of the early Miocene Sauce- sian Stage above the chert (ItL. Pierce in Dibblee, l973b; Vedder and Repenning, 1975). The foraminifera indicate that the Soda

Lake Shale was deposited at bathyal depths, and Bartow (1978) suggests that this unit represents a basinal deposit with turbidite interbeds.

In the subsurface of the Russell Ranch field, the Soda Lake

Shale Member varies from a maximi.mi thickness of 600 feet southeast of the oil field to a minimum of 200 feet northward (Plate IV,

Fig. 9). The thickness variations are related to structural growth during the time of Soda Lake deposition (see discussion b- low of Vaqueros-age deformaton, p. 36). The unit is composed of dark brown to gray, massive siltstone which contains abundant foraminiferal and fish remains. The chert bed of the type area 22 was not found in the Russell Ranch field. The numerous sandstone interbeds in the unit are probably turbidite sandstones, as suggested by Bartow (1978) for comparable surface exposures. In the subsurface, the Soda Lake Shale Member is informally called the Colgrove shale. Within the study area the shale overlies the Quail Canyon Sandstone Member and is gradational with the overlying Painted Rock Sandstone Member.

Painted Rock Sandstone Member

The Painted Rock Sandstone is 5,400 feet thick at the type locality near Caliente Mountain (Hill et al., 1958). It is composed of medium-grained, thick-bedded, white arkosic sandstone with common siltstone interbeds. Locally it is fossiliferous.

The upper 900 feet of this unit were originally assigned to the

"Temblor Stage" and the rest of the unit to the "Vaqueros Stage" by Eaton et al. (1941). At the type area, the fauna is now considered to be of "Vaqueros age," early Miocene (Repenning and

Vedder, 1961; Vedder, 1973). The Painted Rock Sandstone Member is assigned a Saucesian age (early Miocene) on the basis of diagnostic Saucesian Stage foraminifera which occur in both the underlying Soda Lake Shale and the overlying Monterey Formation. The sandstone represents open-shelf sedimentation in the central

Caliente Range and deltaic sedimentation to the northwest and southeast (Bartow, 1974).

In the subsurface of the Russell Ranch oil field the Painted

Rock Sandstone Member ranges in thickness from 300 to 800 feet. 23

This member is the major oil-producing sand in the Russell Ranch

field, where it is locally called the Dibblee sand.The member is

composed of gray, fine- to medium-grained,niassive sandstone with

siltstone interbeds common in the lower part and fossiliferous

sandstone beds common in the upper part. Bartow (1974) suggested

that the lowermost sandstones of the member were turbidite depos-

its and that the upper sandstones of the member consisted of near-

shore and beach deposits.

Monterey Formation

The Monterey Formation was named for a distinctive siliceous

organic shale which conformably overlies the Vaqueros Formation.

The formation is late Miocene in age at its type section near

Monterey, California, but ranges in age from early to middle Mio-

cene in the Cuyama basin. Hill et al. (1958) divided the forma-

tion in the Cuyama basin into two conformable members, the Saltos

Shale Member and the overlying Whiterock Bluff Shale Member.

Saltos Shale Member

The Saltos Shale Member of the Monterey Formation (Hill et

al., 1958) was earlier mapped as the Maricopa Shale by English

(1916) and the Upper Temblor by Eaton et al. (1941); it is equiv-

alent to the Sandholdt Formation of Thorup (1943). At the type

section in the central Caliente Range, the Saltos Shale Member

consists of 2,150 feet of argillaceous and siliceous siltstones

and shales with thin beds of impure limestone and dolomite (Hill 24 et al., 1958). Abundant foraminif era and fish remains are characteristic of the unit. The lower part of the Saltos Shale Member contains foraminifera diagnostic of the late Saucesian Stage

(early Miocene), and the upper part contains foraminifera diagnostic of the Relizian Stage (late early Miocene) (Hill et al.,

1958; Lagoe, 1981, 1982); the foraminiferal stages are separated by a basalt sill at the type section (Hill et al.., 1958). Benthic foraminif era indicate that the Saltos Shale consists of base-of- slope or basin floor deposits accumulated at middle bathyal depths

(1,560-6,250 feet) in the lower part of the member, shallowing upsection to upper bathyal depths (470-1,560 feet) (Lagoe, 1981,

1982).

In the subsurface of the Russell Ranch field, the Saltos

Shale is composed of dark brown, hard, laminated to massive siltstone which contains abundant foraminifera and fish remains, and interbeds of gray, fine-grained, silty sandstone. Sedimentary structures suggest a turbidity flow origin for the sandstone beds

(Phillips, 1976; Lagoe, 1981, 1982). In the lower plate of the

Whiterock thrust, the unit varies in thickness from 900 feet in the Russell Ranch oil field to 1,150 feet northeast of the field.

In the upper plate of the thrust, the member reaches a maximum thickness of 1,300 feet; west of the Russell fault the unit varies in thickness from 150 to approximately 600 feet.

Whiterock Bluff Shale Member

The Whiterock Bluff Shale was originally named by English 25

(1916) as the lowermost member of the Santa Margarita Formation, but it was redesignated as part of the Monterey Formation by Hill et al. (1958). In the type area near Whiterock Bluff (cf. Plate

III), the unit is 1,200 feet thick and is composed of finely laminated siliceous shale, thin-bedded fissile shale, and punky diato- maceous shale with abundant foraminifera, diatoms, and fish remains.

The contact with the underlying Saltos Shale is gradational, and in outcrop the contact is difficult to pick (Phillips, 1976). The base of the Whiterock Bluff Shale contains Relizian Stage (late early Miocene) foraminifera, and the remainder of the member contains Luisian Stage (middle Miocene) foraminifera (Hill et al.,

1958; Phillips, 1976). This unit was deposited at upper bathyal depths (470-1,560 feet) in a slope or basin-plain environment

(Lagoe, 1982).

The Whiterock Bluff Shale Member was recognized in the subsurface of the study area by correlation with the type section at

Whiterock Bluff. Surface exposures of the Whiterock Bluff Shale at the northwestern end of the Russell Ranch oil field (Plate III) can be tied to a subsurface unit (Plate X) which has a more pronounced, jagged electric log character than the underlying Saltos

Shale (Fig. 6). It can be recognized in the upper plate of the

Whiterock fault throughout the northern half of the oil field.

Thus in this area the Saltos Shale and Whiterock Bluff Shale members can be distinguished from each other without paleontological control or lithologic descriptions. To the south, in the upper plate of the Whiterock fault, the distinctive electric log char- 26 acter is not present. However, electric log marker 60 (Fig. 6), which is at the base of the Whiterock Bluff Shale sequence in the north, persists to the south in the upper plate of the Whiterock fault and is present in the lower plate as well. The lack of paleontological control or subsurface lithologic descriptions makes it impossible to tell whether the change in electric log character is due to a facies change between the Whiterock Bluff and Saltos Shale, or due to a lithologic change within the White- rock Bluff Shale unit. Thus the Whiterock Bluff Shale may be present in the Russell Ranch oil field in the footwall block of the Whiterock fault. This questionable unit is arbitrarily called

Whiterock Bluff Shale in this report; it attains a maximum thickness of 400 feet and appears to grade laterally eastward into the

Branch Canyon Sandstone. In the hanging wall of the Whiterock fault, the Whiterock Bluff Shale reaches a maximum thickness of

950 feet and it grades laterally into the Branch Canyon Sandstone to the southeast.

Branch Canyon Sandstone

The Branch Canyon Sandstone was named by Hill et al. (1958) for a marine sandstone representing strandline deposition between the offshore Monterey Formation to the 'west and the terrestrial

Caliente Formation to the east. In the type section at Branch

Canyon, the sandstone consists of 3,200 feet of gray-white to tan, fine- to coarse-grained, arkosic sandstone with common calcareous reefs and minor shale interbeds. The lower 2,100 feet of the for- 27 mation contain mollusks and echinoids of the "Temblor" Stage

("Vaqueros," "Temblor," and "Briones" of Eaton et al., 1941).

Mollusks and echinoids of the "Santa Margarita" Stage ("upper

Briones," "Cierbo," and "lower Neroly" of Eaton et al., 1941) occur in the upper 1,100 feet. Relizian and possibly Luisian Stage foraminifera occur in the shale interbeds (Fritsche, 1969; Vedder,

1973). In the Caliente Range to the north, the Branch Canyon

Sandstone contains mollusks of the "Temblor" Stage only (Vedder,

1973), and attains a maximum thickness of 3,000 feet. In the

Caliente Range, this unit was deposited in various shallow-marine environments during numerous marine transgressive-regressive cycles (Clifton, 1981).

In the subsurface of the Russell Ranch oil field, a sandstone with a blocky electric log response (Fig. 5) overlies the Monterey

Formation in part of the area. This sandstone was assigned to the

Branch Canyon Sandstone on the basis of correlations to the South

Cuyama oil field where the unit is more widespread (Schwing, in prep.). In the study area, the unit reaches a maximum thickness of 850 feet and is composed of fine- to coarse-grained, massive, graysandstonewith minor siltstone interbeds. The Branch Canyon

Sandstone grades laterally westward into the Monterey Formation in the subsurface, as it does at the surface (Fig. 10, Plates VI,

IX, X).

Santa Margarita Formation

The Santa Margarita Formation was named by Fairbanks (1904) 28 for a 1,500-foot thick marine sandstone overlying the Monterey

Formation near Santa Margarita, California. The Santa Margarita

Formation in the Caliente Range overlies the Monterey Formation and consists of 1,000 feet of fine- to coarse-grained, white, arkosic sandstone with several calcareous reefs and local pebbly lenses (Hill et al., 1958). This unit was originally mapped as the Ostrea titan zone of the Monterey Formation by Eaton et al.

(1941). The Santa Margarita Formation contains mollusks and echinoids of the "Santa Margarita" Stage of late Miocene age and was deposited under littoral conditions in a regressing sea (Dibblee,

1973b).

Although separation of the Branch Canyon Sandstone and the

Santa Margarita Formation is based on lithology, in places the distinction is difficult to make. The underlying Branch Canyon

Sandstone is composed dominantly of resistant sandstone, and echinoids dominate the fossil fauna (Madsen, 1959; Fritsche, 1969).

In contrast, the overlying Santa Margarita Formation is composed of alternating sandstones and shales containing dominantly oysters and scallops (Madsen, 1959; Fritsche, 1969). The contact between the two formations is placed at the base of a phosphatic claystone assigned to the Santa Margarita Formation (Hill et al., 1958).

However, where the basal shale member pinches out or becomes sandy, the contact is indistinguishable (Hill et al., 1958; Fritsche,

1969).

In the subsurface of the Russell Ranch field, this contact is also difficult to pick. In this report, the only unit assigned to 29 the Santa Margarita Formation occurs in the hanging wail block of the Whiterock fault, where the subsurface unit can be tied directly to surface geology (Plates X, XI, XIII). In the subsurface, the unit consists of up to 700 feet of white to light gray, fine- to coarse-grained, pebbly sandstone with minor blue-gray claystone, and dark green to black, sandy siltstone interbeds.

Branch Canyon Sandstone-Santa Margarita Formation, Undifferentiated (BCSM)

In the subsurface, both in the southeasternmost Russell Ranch field east of the Russell fault and directly west of the fault at the southern end of the field, a thin shale bed separates a lower sandstone with a blocky spontaneous-potential (SP) electric log characteristic (Branch Canyon Sandstone) from an upper unit which has a more irregular, ragged SF electric log appearance (Plates

V-VIII, XII). The lower sandstone is absent over most of the field. The upper unit is designated as Branch Canyon Sandstone-

Santa Margarita Formation, undifferentiated (BCSM) in this report.

It is composed of alternating gray, white, blue, or green-gray sand, and brown, blue, or green-gray shale, which is commonly tuf- faceous near the top. The BCSN unit ranges in thickness from less than 100 to almost 1,200 feet east of the Russell fault, and is as thick as 1,750 feet to the west of the fault. The sandstone is a minor oil-producing reservoir adjacent to thefault. 30

Morales Formation

The Morales Member of the Santa Margarita Formation was named by English (1916) for 2,000 feet of non marine strata near Morales

Canyon, in the Caliente Range. Hill et al. (1958) raised this member to formation rank on the basis of an angular unconformity and differing lithologies between this unit and the underlying

Santa Margarita Formation. At the type locality, several miles north of New Cuyama, the Morales Formation consists of over 2,700 feet of non marine claystone, sandstone, and gravel (Hill et al.,

1958). The lower part of the Morales Formation mapped by Hill et al. (1958) and Dibblee (l973a, unpublished data) south of the

Cuyama River was previously mapped as Santa Margarita by English

(1916) and Pleistocene lake beds by Eaton et al. (1941); the upper part was previously mapped by English (1916) as the Cuyama Forma- tion and by Eaton et al. (1941) as part of the Pleistocene fans.

The Morales Formation is unconformably overlain regionally by

Pleistocene alluvial fans (Hill et al., 1958).

In the Russell Ranch oil field, the Morales Formation in- creases in thickness eastward from about 1,000 feet to over 3,000 feet. The unit commonly consists of a basal green-gray to blue- gray clay or claystone which is overlain by poorly sorted, fine- to coarse-grained, pebbly sandstone with siltstone and claystone interbeds. Lithologic descriptions from ditch samples indicate

that the formation changes color upsection from blue-gray and green-gray to buff or brown. 31

Although the Morales Formation is a continental deposit, in the subsurface it is difficult to distinguish it on the basis of electric log characteristics arid available subsurface lithologic descriptions from the underlying marine Branch Canyon Sandstone-

Santa Margarita Formation, undifferentiated. An angular uricon- formity at the base of a claystone was used as the contact between these formations in the subsurface of the oil field (Plates V-X).

Locally, however, the claystone is absent and the precise location of the unconformity is difficult to pick. The Morales Formation in the subsurface can be correlated across the Russell fault, whereas units below the unconformity cannot be correlated across this fault.

No angular unconformity was recognized in the subsurface of the South Cuyama oil field; the base of a clay unit (electric log marker MO) was designated as the base of the Morales(?) Formation in this oil field by Schwing (in prep.). Cross section A-A'

(Plate V) shows two clay units at the southeastern edge of the

Russell Ranch oil field. One clay layer (electric log marker y) lies within the Branch Canyon Sandstone-Santa Margarita Formation, undifferentiated, and the other clay layer (electric log marker

ML) lies above the angular unconformity. Only one clay unit (MO) is recognized in the South Cuyama field, and it corresponds with the lower clay (y) in the Russell Ranch field. This suggests that the unconformity cuts upsection to the south towards the South

Cuyama oil field and that the lower part of the Morales(?) Forma- tion of Schwing (in prep.) is actually the upper part of the 32

Branch Canyon Sandstone-Santa Margarita Formation, undifferentiated of the Russell Ranch field. This correlation is further supported by structural relations (discussed later under Russell

Fault System).

in the subsurface, the Morales Formation cannot be distinguished from overlying alluvial deposits. There is no evidence of discordance or change in lithology upsection, suggesting that either the alluvial deposits are less than 200 feet thick (the depth to which the wells are cased and there is no electric log) or that the alluvial deposits are concordant with the Morales

Formation. The latter is not consistent, however, with surface data.

The age of the Morales Formation is uncertain. At the type locality and in the subsurface, it unconformably overlies marine strata of late Miocene age, and at the surface it unconformably underlies alluvial deposits of presumed Pleistocene age. Thus the Morales Formation may be as old as late Miocene, but is probably

Pliocene or Pleistocene in age.

Alluvium

T. Dibblee (unpublished data) divided the alluvial deposits of the Russell Ranch area into four units. These include fan gravels, older alluvium, younger alluvium, and river sands and gravels.

The fans, of probable Pleistocene age, show varying degrees of dissection and deformation; the coarse detritus indicates a 33 local derivation. Several terrace levels are distinguishable in the older alluvium, which is also probably Pleistocene in age.

Crystalline clasts in the Holocene younger alluvium and the present bedload of the Cuyama River indicate a source area in the

Mt. Pinos, Frazier Mountain area to the east.

Alluvial deposits at the surface could not be correlated to the subsurface in the Russell Ranch area. Electric log correlations in the subsurface suggest that the alluvial deposits, including the Cuyania River sediments, are less than 200 feet thick

(Plates V-XIII). 34

STRUCTURE

General Statement

The major structures within the study area include the steeply southwest-dippingRussellfault, the northwest-trending Russell

Ranchanticline, and the moderately northeast-dipping Whiterock and Morales faults. The major faults of the Cuyama basin are shown in figure 8. The Russell fault truncates the southwest flank of the Russell Ranch anticline. An unconformity truncates the

Russell fault in the subsurface, and the Whiterock fault tectonically overlies both the Russell fault and the Russell Ranch anti- dine. The structural features in the study area are discussed in order of relative age, from oldest to youngest.

Pre-Caliente Range Structures

Four episodes of deformation preceded and/or accompanied faulting and uplift of the Caliente Range. These are: (1)

Vaqueros Formation deformation;(2) Cox-type faults;(3) faulting on the Russell fault system during deposition of the Branch Canyon

Sandstone-Santa Margarita Formation, undifferentiated (BCSN); and

(4) Morales Formation deformation caused by post-BCSM Russell fault movement. The structural patterns and characteristics of these four structures define a style that, taken as a unit, suggest deformation in a right-lateral wrench system. 00 5. 9 Tectonic Map Figure 8. 4, CALIFORNIA 350O A' \( \\------RUSSELL RANCH (_ -1 T &, AUcT 's'!../ OIL FIELD 4'.' CUjIQr,?o Strike- slip FoulReverse Fault o 5 0 5 Km Anhicline o 0°00 5 Draft n b Ed OM a R Ilowas 9°4 Oil Field 36

Vaqueros Age Deformation

Thicknesses ofthe Soda Lake Shale and Painted Rock Sandstone

Members appear to reflect deformation following deposition of the

Quail Canyon Sandstone Member. The deformation created elongate west-northwest-trending submarine troughs and highs which trend obliquely westward toward the Russell fault. The folds are defined by isopachs of the Vaqueros Formation (Plate IV) and they show a right-stepping en echelon pattern which continues to the southeast into the South Cuyaina oil field (Schwing, in prep.).

As a result of this deformation, which accompanied Soda Lake and

Painted Rock deposition, the Vaqueros Formation varies in thickness by over 800 feet across the Russell Ranch field on the east side of the Russell fault (Plate IV). Data to the west of the

Russell fault are inconclusive.

A stratigraphic correlation section (Fig. is representa- tive of the thinning of the Soda Lake Shale and Painted Rock Sand- stone from the submarine troughs across the structural highs; none of the beds are truncated against the highs. Structural growth either prior to or contemporaneous with deposition of the

Soda Lake Shale could have caused the observed thinning of the unit across the highs. If the high formed prior to deposition, a combination of slumping of the hemipelagic silts off the highs and by-pass of turbidites around the highs could account for the apparent thinning of this unit. However, the lack of truncation of any beds against the highs suggests that structural growth was Figure 9. Stratigraphic Correlation Section of the Vaqueros Formation. Quintano 1 -16 2271' 26-9, projected 2071' (For location of wells, see Plate ]V.)23-9, projected 2113' 25-10 2159' Steele Pet. 1-10 2112' Elevatton of kelly bushing above sea level N LL E + 30S ± ± a)c>.' --'7----- Saltos Shale Mbr. 0 ---25----- datum SandstonePainted Rock Mbr. ft- --QuailTO. 5173 Canyon Ss. Mbr. *Soda4Pre-Oligocene Lake Shale Mbr. Marine Sedimentary 10.5000 TD.5085 TO. 5340 200 OREGONBARBARA STATE B. NEVINS UNIVERSITY No Horizontal Scale Vertical Scale oo \A ç4400 Drafting1982 by Edwin R. Howes ('4 38 contemporaneous with deposition of both the Soda Lake Shale and the Painted Rock Sandstone.

In contrast, in the South Cuyama area, Schwing (in prep.) was able to show truncation of several electric log markers in the lowermost Soda Lake Shale against the Quail Canyon Sandstone.

This suggests that structural growth may have begun slightly ear- her in the South Cuyama area than in the Russell Ranch region.

The underlying Quail Canyon Sandstone shows large thickness variations across the oil field, but the variations show no consistent relationship to the thickness variations seen in the overlying units. This suggests that structural growth and subsidence were initiated after deposition of the Quail Canyon Sandstone, and that Quail Canyon Sandstone thicknesses are related to pre-Vaqueros topography.

The early stage of wrench tectonics in a right-lateral system produces a right-stepping en echelon pattern of folding

(Wilcox et al., 1973) similar to that seen in the Vaqueros Forma- tion along an ancestral Russell fault. If the folds in the study area die out away from the fault, this would imply that right-slip movement on a wrench system may have occurred during the time of deposition of the Vaqueros Formation. However, as seen on Plate

IV, the well control is inadequate to determine whether the folds die out or not.

Cox-type Faults

The northerly trending growth faults of early Miocene age in 39 the Russell Ranch oil field are probably correlative with faults of the Cox fault zone, a major structural feature east of the

South Cuyaina oil field (Fig. 8; Lagoe, 1981, 1982). In the Russell

Ranch field the Saucesian Saltos Shale thickens by a maximum of

150 feet on the downthrown side of the east-dipping growth faults

(Plates VI, VIII). The underlying Painted Rock Sandstone has a uniform thickness across the faults and the growth faults do not cut an overlying electric log marker of early Relizian age. This demonstrates that the faults were active in the Russell Ranch field from latest Saucesian to early Relizian time.

The Russell Ranch anticline, which encompasses the Russell

Ranch oil field, probably began to grow during the late Saucesian, contemporaneously with Cox-type fault activity. Isopach maps of the Saltos Shale at the southern end of the field suggest a very slight, irregular thinning of the unit across the anticline, indicating that, although the anticline persisted after the end of Cox- type faulting, the structure was weakly positive throughout

Saucesian and Relizian time.

The Cox-type fault set may have partly controlled growth of the Russell Ranch anticline during the late Saucesian to early

Relizian time. The northerly trend and normal separation on the

Cox-type faults in the Russell Ranch area indicate east-west extension during the early Miocene.

Russell Fault System

The northwest-trending Russell fault zone dips steeply to the 40 southwest and forms the structural trap for and the southwestern boundary of the Russell Ranch oil field. The Russell fault system is composed of the main Russell fault, a set of north- to northwest-trending strike-slip faults, and a set of northwest- to northeast-trending dip-slip faults. The unconformity at the base of the

Morales Formation truncates all of the faults in most of the

Russell Ranch oil field (Plates V-IX). The Whiterock fault tectonically overlies the faults in the northern end of the field

(Plates X, XI, XIII). The orientation and sequence of development of the faults demonstrate that the Russell fault system formed in response to a right-lateral system of wrench tectonics.

At the southwestern end of the Russell Ranch oil field, the main Russell fault is a single, steeply dipping faultwhichjuxta- poses dissimilar Miocene sequences (Plates V & VII). In contrast, the "Russell fault" at the northwestern end of the field is composed of several parallel faults in a narrow zone. This change in morphology along strike is similar to that described along the

Newport-Inglewood structural zone (Harding, 1973; Barrows, 1974).

At the northwestern end of the Russell Ranch field, a fault slice on the western side of the fault zone contains a section of Saltos

Shale which is correlative to Saltos Shale in the main part of the oil field. This slice is separated from the oil field by several fault slices of uncorrelative units, demonstrating complex interleaving of fault slices in the northwestern fault zone. For this report, the Russell fault at the northwestern end of the Russell

Ranch field refers to the easternmost fault which juxtaposes 41 dissimilar Miocene sections. Although well control in the central part of the oil field is poor, the projected trace of the Russell fault in the central area suggests a slight bend or right step

(Plate XV). This bend is comparable to that described by Schwing

(in prep.) between the South Cuyama and Russell Ranch oil fields.

Dissimilarity of coeval units across the Russell fault indicates that fault movement is probably largely strike-slip. At the southern end of the field, southwest of the Russell fault, the Branch Canyon Sandstone-Santa Margarita Formation, undifferentiated, is as much as three times thicker than it is northeast of the fault. Conversely, the Saltos Shale is locally less than half as thick southwest of the fault as it is on the northeast side.

Normal fault slip during BCSM and Saltos Shale deposition should have produced thickening of both formations on the same side of the fault. Electric log markers in either unit could not be

correlated across the Russell fault. Offset of the Branch Canyon

Sandstone suggests a minimum of three miles of right-lateral hori-

zontal separation (Fig. 10) along the Russell fault, compared with previous estimates of between 8 and 14 miles of right-lateral

displacement for the Russell fault (Schwade et al., 1958; Bartow,

1974; Lagoe, 1982).

The north- to northwest-trending strike-slip faults form a

vague left-stepping, en echelon pattern sub-parallel or slightly

oblique to the main Russell fault (Plate XIV). The dips of the

faults range from 50° to almost 80° to the southwest. Movement

was predominantly strike-slip and generated apparent normal and 42

Figure 10. Diagrammatic Map of the Facies Boundary Between Branch Canyon Sand- stone and Monterey Formation.

Strike-slip Fault

Reverse Fault, Teeth On Upper Plate

Normal Fault, Hachures On Downthrown Side

Approximate Trace Of Facies Boundary Between Branch /--.- Canyon Sandstone And The Monterey Formation 0 23 Encounters Branch Canyon Sandstone \26 \ F- \ c'J A 24 \ Encounters Transitional Facies F- + 25 30 a \\ Encounters Monterey Fm., No Branch \ Canyoii Sandstone (Symbols Combined When In Same 26 25 \ Well) \ \31 30 4 29 D 32 33 F- + \\\\J 0 L '0o r 0\

35 36 32

IN T ION +

?0 \ 0 2 3 45000Ff. 5\\ 4 0 1/2 Mile \\ Russell Ranch Oil Field + \\ 0 \ LOCATION MAPI 7

Russell Ranch Oil Field \. + 0 CU)...4

0 \ 18 0 17 6 43 reverse separation (Plate VIII). The Saltos Shale is correlative across the strike-slip faults, but the faults appear to displace the overlying Branch Canyon Sandstone in a right-lateral sense

(Fig. 10). The Branch Canyon Sandstone-Santa Margarita Formation, undifferentiated, is commonly thicker on the west side and cannot be correlated across the faults.

The absence of correlation in the BCSM suggests that lateral displacement took place during deposition of that unit. Schwing

(in prep.) shows a post-Morales(?) Formation episode of strike- slip displacement along the Russell fault in the South Cuyama oil field. In contrast, the Russell fault system in the Russell Ranch field is truncated by an unconformity at the base of the Morales

Formation. Stratigraphic evidence indicates that the basal part of Schwing's Morales(?) Formation is older than the basal part of the Morales Formation in the Russell Ranch field (see Plate V and discussion on page 31) and suggests that the lower part of the

Morales(?) Formation of Schwing is equivalent to at BCSM of this study. Thus Schwing's post-Morales(?) Formation strike-slip activity would be contemporaneous with deposition of the upper part of the BCSM in the Russell Ranch field. Deposition of the

BCSM during lateral movement along the Russell fault system would account for the lack of correlation of this unit in the Russell

Ranch field. Therefore, the fault system apparently moved after the end of deposition of the Saltos Shale and sometime during deposition of the overlying two units.

The northeast- to northwest-trending dip-slip faults, which 44 show normal separation, dip from 30° to 800 to the west and include two growth faults, one of which appears to be listric (Plates VI

& IX). Vertical separation of the Saltos Shale and overlying units ranges from 50 to 400 feet across individual normal faults, but there is no evidence of strike-slip displacement on these faults. Growth fault activity began during deposition of the lowermost Luisian (middle Miocene) Branch Canyon Sandstone and ceased during deposition of the Branch Canyon Sandstone-Santa

Margarita Formation, undifferentiated (Plate VI). This resulted in a thickening of these units by up to 600 feet on the downthrown side of the faults. Normal faults similar to those in the Russell

Ranch field form as tension fractures along wrench zones and commonly develop during the early stages of deformation (Wilcox et al., 1973). Therefore, constraints on timing of growth faulting indicate that wrench activity was probably renewed during middle

Miocene time in the Russell Ranch field.

The middle Miocene strike-slip and dip-slip faults in the

Russell Ranch field, and growth of the Russell Ranch anticline, may have formed in response to wrench movement oriented parallel to the Russell fault. The orientation of the subsidiary faults with respect to the main Russell fau't is similar to that in models of wrench tectonics in a system of right-lateral shear

(Wilcox et al., 1973). The Russell Ranch anticline appears to be a northwest- or north-northwest-trending fold (Plate XIV) which trends obliquely to and is truncated to the southwest by the strike-slip faults of the Russell fault system; the trend of 45 the fold is consistent with the orientation of strike-slip and normal faults in a right-lateral wrench-fault system. Similar features are found along the Newport-Inglewood fault (Harding,

1973; Barrows, 1974).

The development of the Russell fault as the main throughgoing wrench fault in a right-lateral shear system probably occurred after folding of the anticline and formation of the strike- slip and dip-slip faults, if it follows the style described by Wil- cox et al. (1973). The braided fault pattern on the southwestern edge of the Russell Ranch anticline is similar to faults which form during the development of the main throughgoing wrench fault.

Distortion and complex faulting of the entire fault zone occur as the displacement is shifted from the numerous subsidiary faults to the main wrench fault (Wilcox et al., 1973). The structure of the Russell Ranch field indicates that the single trace, throughgoing wrench fault developed at the southern end of the Russell field is not present in the oil field farther to the northwest.

Morales Age Deformation

Deformation which post dates the unconformity at the base of the Morales Formation created elongate northwest-trending right- stepping en echelon folds at the base of the Morales Formation

(Plate XVI). The folds cross the Russell fault at an oblique angle and die out laterally away from the fault. The northwest orientation of the en echelon folds suggests deformation in a right-lateral wrench-fault system, oriented parallel to the Russell 46 fault. The Morales Formation is uncut by any fault of the Russell fault system, indicating that wrench movement following deposition of the Branch Canyon Sandstone-Santa Margarita Formation, undifferentiated, was small. Rupture along the wrench system was possibly confined to the basement blocks, causing folding of the overlying sediments without significant lateral offset.

In summary, the intricate structure associated with the

Russell fault zone is the result of a northwest-oriented wrench system of right-lateral shear which began possibly as early as

Oligocene- early Miocene time and continued into the time of

Morales Formation deposition. Minor variations in the extensional and compressional stresses, in both time and space, caused a tectonic overprinting of different deformational styles related to the development stages of a major right-lateral wrench-fault system.

Caliente Range Faults

A series of northeast-dipping faults with reverse separation trends to the northwest along the northern edge of the Cuyama

Valley. These faults appear to be arranged in an en echelon pattern (Plate III) and include, from southwest to northeast, the

Whiterock, Morales, and Caliente Mountain faults. The Whiterock fault, which is exposed northwest of the study area, but has only minor surface expression in the area, is well documented by subsurface data over most of the Russell Ranch oil field. To the northeast, the Morales fault occurs in only one well in the study 47 area, the Shell Mackie 1 well. The Caliente Mountain fault, which was first discussed by Eaton (1939) and Eaton et al. (1941), is northeast of the study area and is not discussed further in this report.

Whiterock Fault

The northwest-trending Whiterock fault tectonically overlies the northern half of the Russell Ranch oil field and cuts most of the Oligocene and younger sequence (Plates VIII-XIII). In the north, the fault strikes northwest and is subparallel to the Red

Hills-San Juan-Chimeneas-Russell fault system to the northwest.

To the south, the fault curves to an easterly trend (Plate XVII) which is parallel to that of the Cuyama Valley and the Transverse

Ranges to the south. At the northeastern edge of the oil field, the fault is parallel to bedding and dips 200 to 30° to the northeast. Across the oil field to the southwest, the fault steepens to 45° as it overrides the middle Miocene normal faults of the Russell fault system. The fault ramps steeply to the surface with dips up to 75° as it overrides the middle Miocene strike-slip faults and the main Russell fault. Northeast of the oil field, the fault cuts downward across the stratigraphic section. The downdip extension of the Whiterock fault, especially the possibility of downdip extension into the crystalline basement, could not be resolved with the data available for this study.

However, northwest of the study area, a surface analogue suggests that the fault extends into the Vaqueros Formation and pre-Oligo- 48 cene strata (Dibblee, 1973a, unpublished data; T. Davis and E.

Duebendorfer, unpublished data). Both Vaqueros sandstone and pre-

Oligocene conglomerate occur along the fault to the northwest; the soutnernmost occurrence of Vaqueros Formation crops out just northwest of the study area and is shown on Plate III. Surface mapping of the Saltos-Whiterock Bluff Shale contact, northeast of the Whiterock fault exposures, demonstrates the presence of a monocline. The relatively straight-traced Whiterock fault cuts downward through the monocline at the mouth of Morales Canyon; this is analogous to the subsurface relations in the Russell

Ranch area (cf. Plate XIII).

Subsurface data indicate that the older structures in the

Russell Ranch area controlled the geometry of the developing White- rock thrust. The numerous faults of the Russell fault system juxtaposed rocks of contrasting lithology and orientation, and caused ramping of the decollement fault plane; rootless folds formed in the upper plate, above the tectonic ramps. The White- rock fault at the northeastern edge of the field follows a bedding plane at the base of the Saltos Shale. This plane is probably a bentonite layer, as based on electric log characteristics and a few core descriptions. The southwest-dipping normal faults juxta- pose the bentonite bed against siltstone and shale typical of the

Saltos Shale. This forced the Whiterock fault out of the bentonite layer and into other rock types. As a result, the fault was deflected slightly upsection on the southwest side of the normal faults. The southwest-dipping strike-slip faults and the main 49

Russell fault juxtaposed sandstone and siltstone of the Branch

Canyon Sandstone-Santa Margarita Formation, undifferentiated, against the less competent Saltos Shale. The contrast between these lithologies, in addition to a contrast in the dip of the units across the strike-slip faults, caused the Whiterock fault to be deflected sharply upsection across these faults. The steep upward deflection of the Whiterock fault produced severe deformation in rocks of both the upper and lower plates of the Whiterock fault. Electric log correlations indicate that beds in both the hanging wall and footwall were folded by drag along the fault

(Plates Ix-xIIl). Deformation in the hanging wall produced several rootless folds (Fig. 12) which resemble those found in the Caliente Range.

Fault-bend folds in a thrust sheet are formed in response to steps in a decollement surface (Rich, 1934; Suppe and Namson,

1979). These rootless folds, as illustrated by Harris and Milici

(1977) in the Appalachians, can be defined by 'domains" (Fig. 11) which show the relationship of bedding between the upper and lower plates of the thrust. The domain boundaries and fold axes described by Harris and Milici (1977) are parallel to the trace of the underlying fault; the domain boundaries and fold axes above the Whiterock fault trend obliquely to the strike of the fault

(Fig. 12, Plate XVII). If the fold axis is normal to the direction of fault movement, this would indicate oblique right-slip movement along the northwest-trending Whiterock fault segment.

A relatively large component of oblique-slip movement along 50

Figure II. Diagrammatic Cross Section of Rootless Folds Typical of Thin-skinned Deformation. (Modified from Harris and Milici, 1977.)

tectonic rampi upper level d6collement-

ç-lower level dcollement

I B111t I

Idealized Fold Domain Boundaries I. Bedding plane both plates, no separation. U. Bedding plane upper plate, cross-cutting lower plate. Itt. Cross-cutting both plates. ].Cross-cutting upper plate, bedding plane lower plate. Fl gure 12. Structure Contour Map 51 725 MontereyofSaltos Electric-log Shale Formation, MemberMarker Upper 211of th enthe Plate 3PC -396 N \\\ N of the Whiterock Fault. 260 -s'N N\ -16851 I 200 320 N\b070 \- \ -: I \\ \ I \ I 480 415 (45J \ \\ j Contour line, dashed where -'. 415435 400360 4Z2 55 25352' 1 /663/ -650 / ( I I ( ( inferred,dash -dot interval pattern 200 represent feet; S // r(5L 75 \ç470 ('73 tOO foot interval (----). \4o .\.735 i \ \ .c3 -1605 110 Ill -842 \ \ \ 2952 \ \ \ \ \ \ 40 \\ O675 \ \\ ', o \ Altitude of horizon abovebelow(-) or sea level. \ 260 146\ 305 4O\O\"\ '-836 OH. - 4I0 \ 28O 305\5 '' \ \\ \ \ \ . -'-.--'-"- \ \\\\\ \ \ \ \ \N335 20 \\:63'0\ \ ' \ \\ \-845\\-430\\\ \ \ \ \\ \ \ \ \ \-o\ \ % (JQ 630 \\\ \ '\\\ \ \\ \\ \ 0000 \ \ \\ Oo\OOQ°0\ \ '& 'o \ N N N N NNNNN N -3180 I '55 N- N 0 - 2 I 3 4 5000 Feet N\ \\°5N NN" N N 0 1/2 i le Trunc0 NNN - -.- IM 2\NN \\\NNN hiferock N NNN 52 this fault segment is also strongly indicated by the absence of any faults of the Russell fault system and the presence of a thick deposit of Whiterock Bluff Shale in the upper plate. Electric log markers which are offset across the Whiterock fault suggest

1,500-2,000 feet of dip-slip separation. Based on this, one would predict finding the extension of the lower plate faults in the upper plate. Yet none of the lower plate structures were recognized in the upper plate. Furthermore, it seems unlikely that the upper plate sequence of Whiterock Bluff Shale, a basinal deposit

(Lagoe, 1982), was transported from the east, the direction of the

Luisian strandline (Clifton, 1981; Lagoe, 1982). The north-northeast south-southwest contraction suggested by the orientation of the upper plate fold axes would produce oblique right-slip movement on the northwestern fault segment and dominantly dip-slip movement on the southern segment of the fault. The northwest-

trending segment of the Whiterock fault is probably a tear fault; the geometry of the fault plane was influenced by the underlying structures.

The Whiterock fault was active in the Pleistocene, after movement ceased on the Russell fault. Subsurface control indicates that several small south-facing fault scarps, mapped by T.

Davis (cf. Plate III) in Pleistocene alluvium and fanglomerate in the southwestern Russell Ranch field, are related to the Whiterock

fault; the westernmost fault scarp is probably the surface trace of the fault (Plate VIII). Faulting did not displace Holocene alluvial deposits. In the upper plate of the Whiterock fault, the 53

Pliocene-Pleistocene Morales Formation shows no evidence of the folding seen in this formation along the Russell fault in the lower plate (Plate XVI), suggesting that deformation related to the Russell fault ceased prior to movement on the Whiterock fault.

Morales Fault

The northeast-dipping Morales fault is roughly parallel to the curved trace of the Whiterock fault to the southwest. The exact location and extent of the surface trace, however, is con- troversial (Dibblee, 1973a; Bartow, 1974; Vedder and Repenning,

1975; T. Davis oral cominun., 1980, 1982). At the northeastern edge of the study area (Fig. 8, Plate III), T. Davis (oral commun.,

1982) does not find any surface expression of a fault, and he believes that the Morales fault must die out before reaching the surface. The apparent thinning of the Santa Margarita Formation northeast of the proposed surface trace may be explained by limb attenuation on the overturned syncline, rather than faulting.

The axis of this syncline would be close to the trace of the

Morales fault as drawn on the geologic map, Plate III. The Mackie

1 well documents the location of the Morales fault at depth; the

Saltos Shale is faulted over the Santa Margarita Formation. The projection of the fault upsection from the Mackie well is equivo- cal, and it may die out in the overturned limb of the syncline as shown in Plate XI.

Continental strata as young as Pleistocene are involved in thrusting along the Morales fault in the subsurface (Vedder and 54

Repenning, 1975). Faulting produced scarps in Holocene alluvium

(T. Davis oral coinmun., 1980). Furthermore, alluvial deposits in the hanging wall of the Morales fault contain clasts of crystalline rocks, similar to clasts in the modern fluvial deposits of the

Cuyama River. Therefore, movement along the Morales fault apparently took place after the emplacement of the Cuyama River in its present course. 55

GEOLOGIC HISTORY

A tectonically active borderland developed along the continental margin of central California during the Late Cretaceous and early Tertiary in response to transform faulting along a proto-

San Andreas fault (Nilsen and Clarke, 1975). Deep, restricted marine basins with rapid sedimentation were characteristic of the borderland area. One of the major basins of this area, the

Sierra Nadre basin of"Chipping (1970, 1972), received over 30,000

feet of sands, silts, and gravels during the Late Cretaceous and

early Tertiary. Subsequent uplift and deformation took place

sometime before deposition of the continental Sixumler Formation

of Oligocene age which overlies the marine strata with angular

unconformity.

The sandstone unit of the Sirnmler Formation was deposited by small- to moderate-sized streams in an alluvial plain rimmed

to the south and southwest by alluvial fans. The fans, which com-

pose the conglomeratic unit of the Simmler Formation, spread

northward toward the alluvial plain from the edges of the fault-

controlled basin (Bartow, 1974, 1978; Bohannon, 1976). The Simmler

Formation is absent over most of the Russell Ranch and South Cuyama

area, indicating that these areas were highlands during deposition

of this unit. However, the occurrence of Simmier Formation in

one well east of the Russell fault in the Russell Ranch field

(Arco Russell 42-5) suggests that the topography was locally ir-

regular and that a small accumulation was deposited and preserved 56 in a local depression on this irregular surface. The Russell fault probably widely displaced the accumulations of Siinmler For- mation west of the fault from their original locations.

Basin subsidence and a marine transgression in late Oligocene

(Zemorrian) time was a response to early interaction between the

North American and Pacific plates (Bartow, 1978). The shallow- marine Quail Canyon Sandstone was deposited in a near shore environment on an irregular erosional surface. The surface was formed on the deformed strata of pre-Oligocene age, and, locally, the undeformed Simmier Formation. Rapid subsidence of the basin dropped the shallow-marine sandstone to bathyal depths. At the same time, alluvial fans formed around the southwest perimeter of the subsiding, fault-controlled basin (Bartow, 1974, 1978).

Folding of the basinal sedimentary rocks accompanied further subsidence of the basin and produced right-stepping en echelon submarine troughs and highs. The northwest trend and en echelon pattern of the folds suggest northwest-oriented, right-lateral shear along a proto-Russell fault system that may have been active as early as latest Oligocene time (during deposition of Soda Lake

Shale). The Soda Lake Shale and Painted Rock Sandstone thin across the submarine structural highs, indicating that deformation continued throughout deposition of these units. The basin reached maximum depths during deposition of the lowermost Soda Lake Shale.

Sedimentation outpaced basin subsidence, and subsequent deposition occurred during progradation of the shoreline (Bartow, 1974).

Schwade et al. (1958) and Bartow (1974) suggested that a large 57 normal fault along the southern edge of the Caliente Range controlled subsidence and sedimentation within the basin that was later to become the Caliente Range. This produced a great thickness of Soda Lake Shale and Painted Rock Sandstone north of this

Caliente Mountain frontal fault and a thin sequence south of the fault under Cuyama Valley. Alternatively, strike-slip displacement at a later time could have juxtaposed the two contrasting sections of Vaqueros Formation (Smith, 1977). In the Caliente

Range, a set of left-stepping en echelon domes expressed in these early Miocene and older strata suggests an episode of left-lateral wrench tectonic faulting along the southern edge of the Caliente

Range.

Renewed basin subsidence resulted in the deposition of middle bathyal Saltos Shale on top of the shallow-marine Painted Rock

Sandstone. Turbidity currents and other grain-flow processes deposited interbeds of sandstone and siltstone in the Saltos Shale

(Lagoe, 1981, 1982). Normal faults of the Cox fault set developed across the Cuyama Valley and controlled basin subsidence in the eastern Cuyama basin during the late Saucesian to early Relizian.

Simultaneous growth of both the faults and the major anticlines in the Cuyama Valley produced thick deposits of Saltos Shale on the downthrown side of the faults and thin deposits of the shale across the structural highs (Lagoe, 1981, 1982; Schwing, in prep.).

A large submarine fan developed east of the Cox fault zone from a source to the north or northeast and marks the approximate position of the early to middle Miocene basin strandline (Lagoe, 1982). 58

The east-west extension demonstrated by the northerly orientation of the Cox fault set may reflect continued deformation along the

Oligocene right-lateral shear system. Middle Miocene norma.l faults with small displacement, some filled with basalt, cut the en echelon domes in the Caliente Range and may be related to the same episode of extensional tectonics.

In the Caliente Range, shallow-marine and deltaic deposits of the Branch Canyon Sandstone intertongue to the northeast with the continental red beds of the Caliente Formation and to the southwest with the bathyal marine Saltos Shale. The marine to nonmarine transition zone encompasses a complex pattern of transgression and regression and marks the approximate boimdary of the middle Miocene shoreline (Clifton, 1967, 1968, 1981). Local basalt flows, the "Triple" basalts of Eaton (1939), were extruded in the

Caliente Range during the middle Miocene and crossed the fluctu- ating shoreline.

Basin subsidence slowed during the Luisian, and sediment progradation began to fill the basin from southeast to northwest.

A high sea level stand at this time trapped terrigenous material around the basin margins and produced undiluted biogenic deposition in the central part of the basin (Phillips, 1976; Lagoe,

1982). This deposit, the Whiterock Bluff Shale, is limited in extent and grades laterally into the Branch Canyon Sandstone; the

Whiterock Bluff Shale is absent under most of the Cuyama Valley

(Lagoe, 1981, 1982).

Major right-lateral displacement along a northwest-oriented 59 shear system occurred during progradation of the Branch Canyon

Sandstone and the shallow-marine Santa Margarita Formation. East- west extension related to wrench tectonics along the shear system produced numerous northwest- to northeast-trending normal faults of the Russell fault system. Northwest-trending strike-slip faults of the Russell fault system, parallel to the shear zone, developed during deposition of the BranchCanyonSandstone-Santa Margarita

Formation, undifferentiated, and disrupted patterns of sedimentation. Continued wrench faulting in the late Miocene culminated in the narrowing of the shear zone and the development of the

Russell fault as the main, throughgoing wrench fault.

Deformation in the Russell Ranch area resulted in an angular unconformity between the Santa Margarita Formation (which marked the end of marine deposition in the Cuyama Basin) and the nonmarine deposits of the Pliocene-Pleistocene Morales Formation.

Deformation must have been much less intense to the southeast, as the contact between marine and non marine deposition in the South

Cuyama area is apparently conformable (Schwing, in prep.). Subse- quent minor movement on the wrench system folded the Morales For- mation in the Russell Ranch area into elongate northwest-trending en echelon folds, oblique to, but uncut by the Russell fault.

Quaternary deformation in the Cuyama Basin is characterized by a shift from a regime of extensional and strike-slip tectonics to one of north-south compression. Miocene and older rocks in the

Sierra Madre Mountains to the south were tightly folded into rootless, north-verging folds and thrust northward along the south- 60 west-dipping South Cuvama and Ozena faults (Vedder and Repenning,

1975; Schwing, in prep.). Deformed and faulted older alluvial deposits indicate that youngest movement along the South Cuyama fault continued into the late Pleistocene (Vedder and Repenning,

1975). In the Caliente Range to the north, Miocene and older rocks were folded and thrust southward along the northeast-dipping

Whiterock, Morales, and Caliente Mountain faults. The Whiterock fault tectonically overrode the Russell fault and much of the

Russell Ranch anticline. Fault scarps in the older alluvium indicate a late Pleistocene age of movement; undeformed Holocene alluvium overlies the fault trace. The en echelon domes in the

Caliente Range were exposed during late Pleistocene uplift along the Morales fault (Vedder, 1973). The most recent movement on the range front has deformed and cut Holocene alluvial deposits. 61

CONCLUSIONS

The structure of the Russell Ranch oil field and adjacent areas formed in response to wrench tectonics throughout the late

Paleogene and Neogene along a northwest-oriented, right-lateral shear system. The orientation and apparent sequence of develop- merit of the structural features in the Russell Ranch field are consistent with the laboratory clay-model wrench systems of

Wilcox et al.(1973) and with other structural trends of wrench fault affinity (cf. Harding, 1973; Barrows, 1974). Subsurface mapping techniques have shown the development of wrench tectonic features in the Russell Ranch field which began in the late Oligo- cene. Recurrent right-lateral shear along the northwest-oriented system produced a complex deformational pattern of right-stepping en echelon folds, normal faults, and left-stepping strike-slip faults, which culminated in the development of the Russell fault as the main throughgoing fault of the shear zone. The tectonic style of deformation in the Cuyama basin during the Neogene is similar to the wrench tectonism of the Salinas and other central

California coastal basins during the middle Miocene (Graham, 1978).

Wrench-style deformation in the Cuyama Valley began about

29 m.y. ago (Zenimorian) and continued until as recently as 5 m.y. ago (early Pliocene). Although the amount of right-slip displacement along the Russell fault system appears to be small, it had a pronounced effect on concurrent sedimentation. Major movement along the Russell fault system ceased about 12 m.y. ago (Luisian), 62 and thus predated incipient offset along the San Andreas fault about 8 m.y. ago (Crowell, 1981). Therefore, the Russell wrench fault system may represent a strand of a proto-San Andreas fault with very small displacement.

The present-day north-south-oriented contractile regime resulted in east-trending thrust faulting in the Transverse

Ranges; movement on the Caliente Mountain, Morales, Whiterock, and South Cuyama thrusts may have been contemporaneous with thrust faulting in the Transverse Ranges. The products of

Quaternary thrusting in the Cuyama region were superimposed on structures produced during earlier wrench tectonics. The older structures influenced the geometry of the Whiterock fault; as the upper plate was thrust southward, the fault plane ramped to the west, across the Miocene faults of the Russell-fault system.

Rootless folds were formed in the upper plate above the tectonic ramps. Thus the northwest-trending segment of the Whiterock fault, which has a large component of oblique-slip displacement, was produced as a result of the underlying topography. The contrast in fault profile between the Whiterock thrust and ramp thrust systems as illustrated by Harris and Milici (1977), is a result of the complex underlying structure in th Cuyama region. Ni.uner- ous, closely spaced faults which juxtaposed slices of contrasting lithologies and orientations precluded bedding plane decollements of any magnitude, in contrast to the Appalachians. Tectonic ramping of the thrust was so closely spaced as to give it a linear, cross-cutting appearance. Thus thin-skinned tectonics in the 63

Cuyama Basin was strongly controlled by and now obscures the structures of the older Russell wrench fault system. 64

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