California State University, Northridge Miocene

MIOCENE GEOLOGY OF THE EAST-CENTRAL PORTION OF THE SAN RAFAEL WILDERNESS, SANTA BARBARA COUNTY, CALIFORNIA

A thesis submitted in partial satisfaction of the requirements for the degree of Master of Science in Geology by John George Yaldezian II

LIST OF ILLUSTRATIONS ••••••••••••••••••••••••••••••••• vi

ABSTRACT. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • X

INTRODUCTION. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 1

PURPOSE AND LOCATION ••••••••••••••••••••••••••••• 1

ACCESSIBILTY. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 1

GEOGRAPHIC SETTING AND CLIMATE ••••••••••••••••••• 4

PREVIOUS WORK. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 6

FIELD AND LABORATORY WORK •••••••••••••••••••••••• 7

REGIONAL GEOLOGY ••••••••••••••••••••••••••••••••• 8

ACKNOWLEDGMENTS • ••••••••••••••••••••••••••••••••• 10

STRATIGRAPHY • ••••••••••••••••••••••••••••••••••••••••• 12

INTRODUCTION •• ••••••••••••••••••••••••••••••••••• 12

METHODS • •••••••••••••••••••••••••••••••••• e •••••• 12

UNDIFFERENTIATED CRETACEOUS ROCKS •••••••••••••••• 16 Nomenclature, Distribution, and Thickness. 16 Lithology ••••••••••.••••.• . . . . . 17 Contacts and Recognition. 20 Fossils and Age •••• . . 20 Origin ••••••• 21

SIMMLER FORMATION •• 22 Nomenclature •• 22 Distribution and Thickness •• . . . . 25 Lithology ••••••••••••••••• 25 Contacts and Recognition. 32 Fossils and Age. . . . . 33 Origin •••••••• . . 34 VAQUEROS FORMATION ••• ...... 37 Nomenclature •• 37 Distribution and Thickness •• 38 Lithology ••••••••••••••••••••• 38

iii Page Contacts and Recognition. . . . . 44 Fossils and Age •• . . . . . 45 Origin ...... 45 RINCON SHALE •••••• 48 Nomenclature •• 48 Distribution and Thickness •• so Lithology •••••••••••••••• . . . so Contacts and Recognition •••• 58 Fossils and Age •• . . . 59 Origin •••••••••• 60

UNDIFFERENTIATED MEMBER OF THE BRANCH CANYON SANDSTONE •• . . .. . 66 Nomenclature •••••••• . .... 66 Distribution and Thickness •• 68 Lithology ...... •. 69 Contacts and Recognition ••• ...... 82 Fossils and Age •• 83 Origin ••••••••••• . . . 84 UNNAMED MIOCENE UNIT. 89 Nomenclature •••• ...... 89 Distribution and Thickness •• 91 Lithology ••...•..•...... 91 Contacts and Recognition •• 98 Fossils and Age •• •• 100 Origin ••••••••••• • .100

UNDIFFERENTIATED MONTEREY SHALE •• .lOS Nomenclature •••••••••••••••• ..105 Distribution and Thickness. .106 Lithology •••••••••••••••• .107 Contacts and Recognition ••• . .. . . • •• 110 Fossils and Age •• • •• 111 Origin ...... • .112

QUATERNARY DEPOSITS •••••••••••••••••••••••••••••• ll4

~~~lJC:~tJ~~- ••••••••••••••••••••• ~ ••••• ~ •••••••••••••••• 117

INTRODUCTION • ••••••••••••••••••••••••••••••••••• • 117

FOLDS • •••••••••••••••••••••••• e ell? Hurricane Deck Syncline •• . . . . .117 Other Folds ...... • .120

iv FAULTS •••••••••••••••• .121 Nacimiento Fault ••• ...... • .121 Other Faults •••••• ...... • .123 POST-MONTEREY SHALE STRUCTURAL HISTORY...... 124

GEOMORPHOLOGY • ••••••••••••••••••••••••••••••••••••••• • 127

SUMMARY OF GEOLOGIC HISTORY ••••••••••••••••••••••••••• 129

REFERENCES CITED •••••••••••••••••••••••••••••••••••.•• 132

APPENDIX 1 •••••••••••••••••••••••••••••••••••••••••••• 138

APPENDIX 2 ••••.•.•••••••••••.•••.••••••• ••..•.••••... • 144

1. Location of the study area in the San Rafael Wilderness .••••••••••••.•••••••••••••• 2 2. Oil and gas-producing basins of southern California which surround the study area...... 3

3. Aerial infrared photograph showing the general geographic nature of the study area...... 5 4. Regional fault map ••••••••••••••••••••••••••••••• 9

5. Stratigraphic diagram showing south to north facies relationships and age correlation of the rock units •••••••••••••••••••• 13 6. Stratigraphic diagram showing west to east facies relationships and age correlations of the rock units •••••••••••••••••.• 14 7. Thin-section sample location map ••••••••••••••••• 15

8. Resistant outcrop of the Simmler Formation...... 27 9. Sandstone lens in conglomerate of Simmler Formation ••••••••••••••••••••••••••••• 27 10. Ternary diagram showing sandstone composition in the Simmler Formation ••••••••••••• 30 11. Outcrop of the Vaqueros Formation •••••••••••••••• 40

13. Ternary diagram showing sandstone composition in the Vaqueros Formation •••••••••••• 42

14. Brush covered slopes of the poorly resistant Rincon Shale ••••••••••••••••••••••••••• 52

15. Fresh exposure of Rincon Shale showing horizontal bedding and sandstone dike •••••••••••• 52

16. Ternary diagram showing sandstone, mudstone, and carbonate composition in the Rincon Shale •••••••••••••••••••••••••••••• 55

17. Zero isopach of the Rincon Shale ••••••••••••••••• 65

18. Multistory submarine-fan channel deposits of the undifferentiated member of the Branch Canyon Sandstone •••••••••••• 70

19. Horizontal bedding and differential cavernous weathering in the undifferentiated member of the Branch Canyon Sandstone •••.•••••••••••••••••••••• 70

20. Brush covered finer-grained deposit of the undifferentiated member of the Branch Canyon Sandstone ••••••.••••••••••••••• 71

21. Pebble filled channel in the undifferentiated member of the Branch Canyon Sandstone •••••••••••••••••••••••••• 73

22. Load features in the undifferentiated member of the Branch Canyon Sandstone •••••••••••• 73

23. Large mudstone rip-up clasts in sandstone bed of the undifferentiated member of the Branch Canyon Sandstone •••••••••••• 74

24. Flame structure in the undifferentiated member of the Branch Canyon Sandstone •••••••••••• 74

25. Convolute bedding in the undifferentiated member of the Branch Canyon Sandstone •.••••••.••• 76

26. Possible slump fold in the undifferentiated member of the Branch Canyon Sandstone •••••••••••••••••••••••••• 76

27. Unconformity between Cretaceous turbidites and the overlying undifferentiated member of the Branch Canyon Sandstone •••••••••••••••••••••••••• 78

28. Ternary diagram showing sandstone, mudstone, and carbonate composition in the undifferentiated member of the Branch Canyon Sandstone •••••••••••••••••••••• 79

29. Zero isopach of the undifferentiated member of the Branch Canyon Sandstone •••••••••••• 88

30. Ternary diagram showing sandstone and limestone composition in the unnamed Miocene unit ••••••••••••••••••••••••••••• 93

31. Photomicrograph showing foraminifera in the unnamed Miocene unit ••••••••••••••••••••••••• 96

32. Same photomicrograph as in Fig. 31 with crossed-nicols ....•.....•.•....•.•...•.•.... 96

33. Photomicrograph showing diatoms and foraminifera in the unnamed Miocene unit •••••••••••••.••••••••••••••••••••••• 97

34. Photomicrograph showing pelecypod fragment filled drusy mosaic calcite cement in the unnamed Miocene unit •••••••••••••.• 97

35. Conformable contact between unnamed Miocene unit and undifferentiated Monterey Shale ••••••••••••••••••••••••••••••••••• 99

36. Index map showing locations of folds and faults in the study area ••••••••••••••• ll8

37. Trough of the Hurricane Deck syncline •••••••••••• ll9

1. Percent composition and texture of four sandstone samples from the Simmler Formation •••••••••••••••••.••••••••••.•.• 31

2. Percent composition and texture of six sandstone samples from the Vaqueros Formation ••••••••••••••••••••••••••••••• 43

3. Percent composition and texture of ten rock samples from the Rincon Shale ••••••••••• 56

4. Percent composition and texture of thirteen rock samples from the undifferentiated member of the Branch Canyon Sandstone •••••••••••••••••••••••••• 80

viii Table 5. Percent composition and texture of eight rock samples from the unnamed Miocene unit ••••••••••••••••••••••••••••••••••••• 94 6. Percent composition and texture of two rock samples from the undifferentiated Monterey Shale ••••••••••••••••••••••••••••••••••• l09

Plate 1. Geologic map and cross-sections of the Miocene geology of the east-central San Rafael Wilderness, San Barbara County, California •••••••••••••••••••••••••• In Pocket 2. Geologic map of the Miocene geology of the San Rafael Wilderness, San Barbara County, California •••••••••••••• rn Pocket

In the remote east-central San Rafael Wilderness, Santa Barbara County, California a sequence of Oligocene to Miocene strata was mapped in detail in order to deter mine stratigraphic and structural relationships between individual rock units.

The oldest rocks in the area are of Late Cretaceous age and are interpreted to have been deposited in a sub marine-fan environment. These rocks were uplifted, slight ly folded, and eroded prior to deposition of unconformably overlying middle Tertiary rocks. During late Oligocene to early Miocene time, continued erosion was accompanied by

X the formation of alluvial fans, as represented by the light-olive-gray cobble conglomerate and lithic arkosic sandstone of the Simmler Formation. Near the beginning of the Miocene, the area subsided. This allowed the sea to transgress and deposit the shallow-water marine arkosic sandstone of the Vaqueros Formation (Zemorrian to early Saucesian> • Continued rapid subsidence accompanied by transgression allowed for the rapid deposition of the Rin con Shale

The Rincon contains foraminifera which are suggestive of a lower bathyal environment. The interchannel and slope deposits of the Rincon consist of light- to dark-gray mud stone with some interbedded yellowish-gray, medium-grained, arkosic sandstone, whereas the submarine-fan channel de posits of the Branch Canyon consist of very light-gray, medium-grained, arkosic sandstone with very minor thin interbeds of mudstone. The interfingering of these two formations and the westward pinching out of the Rincon suggest channel migration to the west. Conformably over lying the Branch Canyon in gradational contact is an un named Miocene unit (Relizian) which contains interbedded yellowish-gray, medium-grained, arkosic sandstone; pale yellowish-brown, fossiliferous limestone; and poorly resis tant yellow-brown mudstone. These rocks represent channel

cene rockse Faults in the area include the major Naci miento fault and three minor faults all of which trend

The primary objective of this thesis is to complete a detailed geologic map and report on the Miocene geology of the east-central portion of the San Rafael Wilderness,

Santa Barbara County, California. The main emphasis is on structural relationships and stratigraphic correlation of the Miocene units. Lesser emphasis is on the Cretaceous units and Quaternary deposits. Included is a preliminary study of the depositional environments of the Miocene units.

The area mapped encompasses about 21 krn 2 ( 8. 5 mi 2> of the San Rafael Wilderness (Fig. 1). The study area includes parts of the San Rafael and Sierra Madre Mountains and is about 34 km (21 mi) north of Santa Barbara and 61 km ( 3 8 mi) southeast of Santa Maria. Producing oil and gas fields surround the Wilderness to the north in Cuyama

Basins, and to the east in Santa Maria Basin (Fig. 2), but oil has not been found within the Wilderness. The lack of oil or economically recoverable minerals and the remote ness of the area have left it little studied.

Accessibility is limited to horseback riders and back- packers. A wilderness permit is required for use of the

area and may be obtained, along with a map delineating the trails, from the u.s. Forest Service, Santa Lucia District Office, in Santa Maria. Parts of the Wilderness are closed

during the fire season. The trails at the time of this writing are in good condition.

west. The western boundary of the mapped area can be reached from Nira by following the Manzana Trail 18 km (11 mi) to

Happy Hunting Ground Campground. The study area also can be reached from the east, but one must obtain special per mission to use access roads which lead to the Wilderness boundary.

area. The canyons are narrow and the mountain slopes are steep. Maximum relief in the mapped area is 640 m (2,100

ft}. The northwest-flowing Sisquoc River provides the main drainage. The Sisquoc is fed by numerous smaller

Climate is of the semiarid Mediterranean type, general ly cold in the winter 4-16°C (approximately 40-60°F) and hot in the summer at 27-38°C (approximately 80-100°F).

Precipitation in the form of rain or snow may fall any time from October through May, with the average rainfall for the San Rafael Mountains at 64 em (25 in) CDibblee, 1950) •

(Fig. 3) and makes mapping difficult. The chaparral con sists of chamise, mountain mahogany, scrub oak, manzanita, and other types. Trees present include oak, sycamore, and 5

Figure 3. Aerial infrared photograph showing the general geographic nature of the study area. View is from east looking west. Dark blue with reddish tint indicates vegetation. Photo shows the east- west trending Hurricane Deck syncline and the northwest- flowing Sisquoc River {foreground) ., 6 big-cone spruce. Poison oak grows in abundance along many of the streams and also is found on some slopes. Wildlife is plentiful and consists of black bears, wildcats, deer, coyote, rabbits, fox, squirrels, mice, rats, skunks, snakes

(including rattlesnakes} , frogs and toads, turtles, many types of lizards, and many birds, such as red-tail hawks.

Sisquoc Condor Sanctuary is approximately 1. 6 km (1 mi} from the eastern border of the area. Insects such as flies, dragonflies, gnats, mosquitoes, spiders, ants, and ticks also thrive in the Wilderness. Native trout may be caught in the Sisquoc River and smaller tributaries during fishing season.

The study area has not been previously mapped in de tail. Fairbanks <1894} described the general structure and stratigraphy along a traverse apparently from north to south across the middle of the area. Gower and others <1966} made a preliminary geologic map

National Wilderness Preservation system. At their recom mendation, the present boundaries of the San Rafael Wilder ness were established. Dibblee (1966) published a map that includes a 1 km (0.6 mi} strip along the southern border of the study area. A reconnaissance geologic map (scale 7

1:48,000) by Vedder and others (1967) included the total map area. Fritsche {1969) did a detailed structural, stra tigraphic, and paleontologic study of the Miocene rocks about 1.6 km {1 mi) to the northeast across the Nacimiento fault in the central Sierra Madre Mountains. The Creta- ceous and Miocene rocks in the northeastern Zaca Lake quad rangle, about 26 km {16 mi) to the west of the study area were studied by Van Wagoner {1981). The Cretaceous rocks have been studied in some detail by Howell and others (1977), McLean and others {1977), and Vedder and others {1977).

The author, along with Stanley Popelar, mapped an 2 2 area encompassing about 55 km { 23 mi > in the Wilder ness. Mapping was done together for purposes of safety in such a remote area. On completion of field work, the mapped area was divided into two adjacent areas. The east ern area is described in this thesis {Plate 1) and Popelar is at this time writing his thesis on the western half.

1982. Mapping was done on UeSe Forest Service aerial pho tographs which have a scale of approximately 1:16,000.

The study area lies at the southern end of the north west-trending Coast Ranges Province and just to the north of the west-trending Transverse Ranges Province (Fig. 4).

The boundary between the two provinces is considered to be the Big Pine fault and the western extension of the Santa Ynez fault (Fritsche, 1969, p. 194). The study area is bounded on the northeast by the Nacimiento fault. The proper name for this fault is presently in dispute (Yaldezian and others, 1983) • The Nacimiento fault has long been cited as a major boundary in the California Coast Ranges between Mesozoic granitic-metamorphic base ment rocks on its northeast side and Franciscan rocks on the southwest (Page, 1966; Vedder and Brown, 1968).

The general structural trend in the study area is west to northwest. The Hurricane Deck syncline is the dominant structural feature. \ ~~<~ l \ 0~\'~ Area shown • ' ) on hgure '"' J N~ '\___

Figure 4. Regional fault map showing location of the study area at the southern end of the Coast Ranges (modified from Fritsche, 1969).

The author is deeply indebted to A. E. Fritsche for the many hours of guidance and patience which made this report possible. His help in the field and the classroom are greatly appreciated. Thanks also go to R. L. Squires for his help in identifying macrofossils and reviewing this report, and to J. G. Vedder for discussions on the structure and stratigraphy of the area and for reviewing this report.

The author owes a great deal of thanks to A. A. Almgren and M. v. Filewicz from Union Oil of California for identifying microfossils and for discussions of the ages and paleobathymetry of the rocks. Appreciation also goes to Getty Oil, the American Association of Petroleum

Geologists, and the Armenian Church Youth Organization of the Western Diocese for supplying me with grants and schol arships which lessened my financial burdens and allowed me to concentrate on my studies. The author is also grateful to Dave Liggett for his technical support, to Linda Ames and Diane Stephens for typing this report, to Dave Advocate and Rod Picknell for helping with the drafting, and to the boys at Rancho Oso for packing us in on horseback.

Special thanks go to my parents, family, friends, and fellow geology students for their support and encouragement.

(and fellow real mountain man) Stan Popelar, whose helpful 11 critic isms and discussion were essential to the writing of this report. STRATIGRAPHY

Stratigraphic units composed of Cretaceous, Eocene, Oligocene, and Miocene rocks along with Quaternary de posits crop out in the study area (Plate 1). Oligocene and Miocene rocks are described in detail and are corre lated to known formational units as best as possible (Figs. 5 and 6). Cretaceous rocks and Quaternary deposits are discussed only briefly, and Eocene rocks, exposed only northeast of the Nacimiento fault, are not discussed at all. The stratigraphic units which occur in the mapped area have been previously mapped in reconnaissance by Gower and others (1966) and Vedder and others (1967), but they were not assigned formation names. The three basins which surround the Wilderness (Fig. 2) all have differing stratigraphic nomenclature and proper extension of these differing nomenclatures into the study area is not without

Rock units are described from field notes, hand sam ples, and detailed analysis of 43 thin sections. Figure 7 shows the rock sample localities from which thin sections were made. These thin sections are on file in the Depart ment of Geological Sciences, California State University, Northridge

12 Lulalan South /Tm"" ' North .,!C• c ·- -• ' ~ / Tmu '\ \ il a:• ---r------r--I \ 1 \'('Present eroaional surface ...>- j Tub \ .! •c c ~ ... •Q - 0 • I \ t-• .. c t . i •0 ,• .. :J I \ ;:, ,- •J .,• 2 ~ / Tr \ - -~,------Tub \

Tm - Undifferentiated Monterey Shale Tr - Rincon Shale Tmu - Unnamed Miocene Unit Tv - Vaqueros Formation Tub - Undifferentiated member of the Ts - Simmler Formation Branch Canyon Sandstone Figure 5. Stratigraphic diagram showing south to north facies relation ships and age correlations of the rock units in the study area. Diagram not drawn to scale but vertical proportions show approximate relative thickness.

1-' w c West East :!• _,:I •c 1 <::::Boundary of study area •(,) 0 :!: j c r-' Tm ::::J II ,.! B - -...-<. IL.• , 'i z 0 a: E.._-->;mu ""·'-_'-._ ..c .! ~ ~ ...>- -~ ""-. c:::;- Present erosional 01 ~• ·-t:• Tub ' z. ~ surface e ' 0 1- ... ! c t» II •c -"0 •(,) .. 0 ' "0 Tr • •(,) 0 j :I 0 ·-~ II w .. rn •ill: .2 Cretaceous

I .... I !: eoe Eoc Q. Cll C II o.=.:::.0«> N• -.: Tm - Undifferentiated Monterey Shale Tr - Rincon Shale Tmu - Unnamed Miocene Unit Tv - Vaqueros Formation Tub - Undifferentiated member of the Ts - Simmler Formation Branch Canyon Sandstone Figure 6. Stratigraphic diagram showing west to east facies relation ships and age correlations of the rock units in the study area. Diagram not drawn to scale but vertical proportions show approximate relative thickness.

.-~----- ·- Tm Undofferenhated Monterey Shale 0 6000 FT Contact ote•at'so· Tmu Unnamed Moocene unot

-t Tub Undofferenttated me~r of the 8ranch Canvon Sandstone 1600 M Antocllne Tr Roncon Shale ~- --+- Tv Vaqueros Formatoon Syncline Til Stmmler Formatoon

r------~tar thea11 area- ------Yaldezoan thea•• erea (tltta report)- - -- -1 .,.•.. ·ao·

Figure 7. Simplified geologic map of the study area and Popelar's adjoin ing study area to the west showing thin section sample locations.

...... U1 16 reference for thin-section rock descriptions. Rock colors were assigned from the Geological Society of America Rock Color Chart (Goddard, 1970). Sedimentary rock terminology and grain size classifications follows Folk (1974). Bed ding and thickness terminology follows Collinson and Thomp son (1982) and Reineck and Singh (1980). Formation thick nesses were determined from cross sections.

Microfossils from 43 samples (Plates 1 and 2 and Ap pendices 1 and 2) were identified by Alvin A. Almgren and

Ventura, where the samples are now on file. The few macro fossils found (Plates 1 and 2) were identified with the help of A. E. Fritsche and R. L. Squires at c.s.u.N. These macrofossils are on file at c.s.u.N. under individual c.s.u.N. locality numbers.

Conglomerate, sandstone, and mudstone of Late Creta ceous age surrounds and unconformably underlies the Oligo cene and Miocene age rocks (Figs. 5 and 6) southwest of the Nacimiento fault in the mapped area (Plate 1) . The unconformable contact served as a geographic boundary be yond which no detailed mapping was done except between separated exposures of Oligocene-Miocene rocks' in the east where the Cretaceous rocks were studied in more detail than those cropping out in the north and south. 17

These Cretaceous rocks have not been named or defined at a type locality. Dibblee (1966) divided the Cretaceous

rocks along the southern border of the mapped area and further to the south in the central Santa Ynez Mountains, Santa Barbara County, into three mappable units which he called in ascending order the Unnamed conglomerate, Un named shale, and Unnamed sandstone. Gower and others (1966) mapped these rocks as one unit, whereas Vedder and

others (1967) divided the rocks into three mappable units as Dibblee (1966) had done. For the purposes of this re

will be called the undifferentiated Cretaceous rocks. The bottom contact of this unit was not mapped;

therefore, the true thickness of the unit is unknown. A thickness of greater than 1,525 m (5,000 ft) is estimated

from cross-section c-c • (Plate 1). McLean, Howell, and Vedder <1977, Fig. 2) show that these Upper Cretaceous rocks obtain a thickness of approximately 3,000 m (9,840

The undifferentiated Cretaceous rocks consist of vary ing amounts of conglomerate, sandstone, and mudstone.

around South Fork Campground (Plate 1), the unit consists mainly of sandstone with some interbedded mudstone and

some conglomerate lenses. Just south of the two north- 18 eastern exposures of the Simmler Formation and running parallel with the unconformity (Plate 1), the unit con sists mainly of mudstone with some interbedded sandstone and lenses of conglomerate. Overall, this unit displays a few moderately resistant ridges of sandstone and con glomerate and some poorly resistant slopes of mudstone. As a whole, the rocks in this unit are better indurated and contain more fractures than the overlying middle Ter tiary units. This unit is distinguished by its 1 ight-olive-gray (5 Y 5/2) and brownish-gray (5 YR 4/1), interbedded, fine- to medium-grained sandstone and mudstone. The sand stone is thin to thick bedded, whereas the mudstone is parallel laminated and mostly thin to medium bedded. These laterally continuous interbeds contain rare Bouma Ta-d,

Tb-d, and Te-d sequences. The beds contain good ripple bedding and some starved ripples. Many of the sandstone beds are graded. Outcrops of light-olive-gray (5 Y 5/2) to light-gray (N 7)

The average conglomerate has an open framework and consists of about 60% clasts and 40% sandstone matrix.

The clasts are well rounded, range in size from pebble (2 em) to boulder (50 em), and average cobble size (7 em).

They consist mainly of light-colored granitics and minor amounts of banded gabbro, argillite, volcanics, a,nd quartz ite.

The conglomerate matrix has the same composition as the sandstone in the unit. The sandstone is fine to very coarse grained. Actual sandstone composition is unknown because no rocks were studied in detail but composition is probably a lithic arkose. The sandstone contains up to as much as 20% biotite.

Fresh and weathered color of the mudstone is light olive gray (5 Y 5/2) and grayish olive (10 Y 4/2) to medium gray (N 5). Mudstone is thin (1 to 10 em) to medium (10 to 30 em) bedded and, in places, parallel laminated. Mud- 20 stone usually is found interbedded with fine- to medium grained sandstone. The mudstone contains both fissile, well-indurated shale and siltstone. No mudstone was studied in detail, so its true composition is unknown.

The lower contact of the undifferentiated Cretaceous rocks was not seen in the study area. The Cretaceous is unconformably overlain in the study area by the middle

Tertiary rocks of the Simmler Formation, the Vaqueros Forma tion, the Rincon Shale, and the undifferentiated member of the Branch Canyon Sandstone (Plate 1). This upper uncon formable contact is a buttress unconformity as defined by

Bates and Jackson (1980) and seen in Figures 5 and 6. The upper contact will be described in more detail in follow ing sections.

Rare to sparse agglutinated foraminifera identifed from this unit by Almgren (Appendix 1) suggest an age of Late Cretaceous (Campanian) and probably represent Goud koff's E to F2 zones.

Macrofossils found in this unit include Inoceramus sp. fragments and impressions and a partial pachydiscid ammonite collected by John Alderson at c.s.u.N. fossil locality 699. These macrofossils are indicative of Late

Cretaceous age (J. Alderson, personal communication). In 21 addition to these macrofossils, Vedder and others (1967)

found Bacul i tes occidental is Meek, Pterotr igonia inezana (Packard), and Trigonia cf. T. leana Gabb about 475 m

(1, 500 ft) north of the study area in the Sisquoc River area. They state that these fossils indicate an early

The source of sediment for the Cretaceous rocks is unknown. The foraminifera found in this unit indicate a

middle to lower bathyal marine environment. The lateral ly continuous interbedded sandstone and mudstone beds which contain Bouma Ta-d' Tb-d' and Te-d sequences, paral lel laminations, and graded bedding are probably the pro duct of turbidity currents and represent facies C and/or D of Mutti and Ricci Lucchi <1978). Thick beds of medium- to coarse-grained, pebbly sandstone which contain mudstone rip-up clasts, scattered pebble-filled channels with scour ed bases, and thin interbeds of mudstone can be the product of both grain flows and high-velocity turbidity currents

(Mutti and Ricci Lucchi, 1978). These pebbly sandstone deposits represent facies B of Mutti and Ricci Lucchi

(1978). The lens-shaped conglomerate beds are interpreted to be facies A channel deposits that were produced by grain flows (Mutti and Ricci Lucchi, 1978). The cross-bedded or wavy-bedded sandstone and mudstone drapes which overlie some of the conglomerate lenses may have been produced by 22 traction and waning-flow currents as current velocity de creased in the channels.

Mutti and Ricci Lucchi (1978) state that deposits of mainly facies B, C, and D and minor amounts of facies A characterize the middle-fan sub-association, which consist of facies A and B channel deposits and facies C and D inter channel deposits.

Schwade and Dibblee (1952), in their field-trip road log through the Cuyama Valley area, called exposures of dark-red sandstone and conglomerate exposed in the south east Caliente Range, the Simmler Formation, but they did not define a type locality. Hill and others (1958) des cribed a complete section of the Simmler Formation at what they designated the type locality in the southeast Cali ente Range, T. 10 w., R. 25 w., East of Cuyama Ranch quad rangle about 32 km (19 mi) northeast of the study area.

They state that at the type locality the Simmler Forma tion (Oligocene(?) to lowermost Miocene) "is made up of a continuous series of hard pink to dark grayish red fine to medium-grained massive sandstone beds with numerous thin interbeds of dark maroon and greenish siltstone. The sandstones are biotitic, well laminated, and commonly cross-bedded. The basal part consists of about 9 m (30 ft) of conglomerate made up of rounded cobbles of grani- 23 tic, porphyritic, and quartz i tic rocks in a dark maroon matrix." The type section of the Simmler is about 915 m (3 ,000 ft) thick. In the western Cuyama Valley and Bad lands, the Simmler Formation is disconformably overlain by light-gray marine sandstone of the Vaqueros Formation and is unconformably underlain by Cretaceous rocks (now recog nized as Eocene by Gower and others, 1966) or granitic basement (Hill and others, 1958).

A lithologically similar unit, the Sespe Formation, was originally described by Watts (1897); was redefined by

Kew (1924) for nonmarine red, brown, and yellow conglomer ate and sandstone with interbedded shale; and has its type locality on Sespe Creek about 6 mi north of Fillmore, in the northwestern part of the Camulos quadrangle, about 87 km (52 mi) southeast of the study area. Dibblee <1966) described the predominantly red rocks of the Sespe in the

Santa Ynez Mountains as consisting of a series of inter bedded argillaceous shale, fine- to coarse-grained sand stone, and conglomerate. The conglomerate is generally well bedded, commonly cross bedded, and is made up of peb bles of hard rock types, such as quartzite, andesitic por phyry, and Franciscan red and green chert or jasper. The unit in the Santa Ynez Mountains is conformably underlain by the marine Coldwater Sandstone and Gaviota Formation and conformably under lies the 1 ight-gray, medium-grained sandstone of the Vaqueros Formation. Dibblee (1966) as signs an age of Oligocene (Refugian) through possibly early 24

An outcrop mapped as Sespe in the Hells Half Acre (just about 8 km (5 mi) southwest of study area) by Dibblee

(1950) has the same lithology as the deposits in the mapped area and at one time was probably connected to the deposits in the study area (Vedder, personal communica tion).

On the basis of similar lithology, stratigraphic posi tion, and relative ages, the Simmler Formation correlates regionally to 1) the Sespe Formation of Watts (1897) in the Ventura Basin, 2) the Berry Formation of Thorup (1943) in the Salinas Basin, and 3) the Lospe Formation of Thol man (1927) in the Santa Maria Basin.

The rocks described below are lithologically, strati graphically, and chronologically similar to both the Simmler and Sespe Formations. Because the type locality for the

Simmler is closer, because the rocks in the study area are unconformable on older rocks, and because the deposits in the mapped area are separated from the Sespe deposits to the south by a highland, possibly the San Rafael Uplift as referred to by Dibblee <1966), Fischer (1976), and Reid

(1979), the deposits in the mapped area are herein desig nated the Simmler Formation.

Canyon area of south Cuyama Valley was divided into eight informal members by Blake (1981), but these informal mem bers were not recognized in this area. 25

The Simmler Formation is exposed at four localities in the mapped area, all of which pinch out laterally (Plate

Vaqueros mapped in the south part of the study area. The northern deposit is the most extensive and is about 2.4 km

The Simmler Formation consists of about 65% conglomer ate, 30% sandstone, and 5% thin, interbedded mudstone which is exposed only in the northern deposit. Outcrops usually are moderately well indurated and are exposed as ridges, some cliffs, and some sparsely vegetated slopes.

The northeastern deposits are poorly exposed. The unit contains some secondary fractures.

Y 5/4) to light olive gray (5 Y 6/1 and 5 Y 5/2). Sand stone color is mainly light olive gray (5 Y 6/1) or yellow ish gray (5 Y 7/2), but can be grayish red (10 R 5/2) and 26

may weather to pale yellowish brown (10 YR 6/2). The color of the mudstone is light olive brown (5 Y 5/6).

in areas containing thin (3-cm-thick) mudstone beds. The unit contains medium- (lOcm) to very thick- (2 m) beds of conglomerate interbedded with thin- to thick-bedded sand-

stone. These beds may thicken and thin, have irregular tops and bases or be horizontally bedded. In the absence of interbedded sandstone, bedding in the conglomerate is

. the vague horizontal bedding and cross bedding found in the unit. Figure 9 shows a sandstone lens present in the conglomerate.

The predominant lithology is the pebble to cobble conglomerate, which consists of 55% clasts and 45% sand

stone matrix (Fig. 9). Clast composition on the average is about 45% light-colored granitic, 30% sedimentary, 20%

volcanic, 3% quartzite, 2% gneiss, and a trace of chert clasts. The igneous clasts are subangular to subrounded,

em). The sedimentary clasts consist of l) green-brown mudstone rip-up clasts, 2) brown to green, medium- to

Figure 8. Resistant 10 m high outcrop of sandstone and conglomerate of the Simmler Formation from the south eastern deposit. Notice vague horizontal bedding and cross bedding.

Figure 9. Sandstone lens in conglomerate in the Sirnrnler Formation. Hammer shown for scale is about 30 ern (1 ft) long. 28 29

(75 ern) and average cobble size (10 ern). The volcanic clasts are green to black, contain light-colored porphy ritic crystals, range in size from pebbles (1 ern) to cob bles (12 ern), and average pebble size (4 ern). Quartzite clasts are milky white and average pebble size (5 ern}. Gneiss clasts are dark and light banded and average cobble size (7 ern). The average conglomerate is poorly to moder ately sorted, has subangular to subrounded, cobble-size (7 ern) clasts, and is both clast and rnatr ix supported. The conglomerate matrix has the same composition as the sand stone described below.

The average sandstone is a light-olive-gray, rned~urn to coarse-grained, subrnature, lithic arkose (Fig. 10) which has an average composition of about 25% cement of various kinds, 25% quartz, 20% feldspar (orthoclase, plagioclase, and rnicrocline), 15% granitic rock fragments, 12% lithic rock fragments

Figure 10. Ternary diagram showing sandstone composi tion in the Simmler Formation. Classification scheme is from Folk (1974). Localities shown on Figure 7. <•=sand• stone) •

of the granitic clasts present in the conglomerate. Some metamorphic rock fragments contain myrmekite. Biotite is diagenetically altered to form hematite and chlorite grains and cements. Grains of biotite are highly deformed. A gradual decrease in grain size in the rocks from coarse sand to clay does not occur, therefore, the clay present in the rocks is probably authigenic cement, and not detrital matrix. Weathering of feldspar grains also supports this statement. The marine rocks from the northeast are 31

TABLE 1. PERCENI' CCXt1roSITION AND TEXTURE OF FOUR SAIDS'IONE SAMPLES FRCM THE Snt-1LER FORMATION

SANDS'IDNES LOCALITY -----+ 11 33 34 23 GRAINS: Quartz 21 23 22 33 Orthoclase 9 13 11 6 Plagioclase 8 7 6 10 Microcline 2 3 Granitic rock fragments 20 9 12 10 Volcanic rock fragments 4 5 6 1 Metamorphic rock fragments 9 6 5 Sedimentary rock fragments 2 Chert t 1 Biotite 8 t t t Muscovite t Chlorite 1 2 Hornblende t Glauconite 1

~: Calcite 2 t 23 Hematite t 29 Limonite 1 Chlorite 7 15 Clay 7 18 5 Leucoxene t Feldspar overgrowths t Q-F-R: 1 Q 28 35 35 51 F 51 45 47 45 R 21 20 18 4 GRAIN-SIZE: 0.125- o.o5- 0.125- 0.125- Range 5.0 3.0 5.0 0.5 Average 0.7 0.25 0.5 0.25

OORTIN;:2 p-m p p-m m ROOIDIN;: 3 sa-sr sa-sr sa-sr sa-sr GENERAL SUfof!ARY: Percent grains 84 65 62 65 Percent matrix 3 Percent fossils 10 Percent cements 14 35 34 24 Percent porosity 2 1 1 Footnotes: 1> Q + F + R = 10 follows Folk ; 2) p=poor, m=moderate; 3> sa=subangular, sr=subrounded. Synbols: t=trace, - =absent. Locali- ties shown on Figure 7. 32 cemented mainly with very fine crystalline calcite, where as the nonmarine rocks from the north and southeast are cemented with chlorite, hematite, clay, and minor amounts of calcite.

Mineralogical maturity is described by Pettijohn (1975, p. 492) as being the ratio of quartz plus chert to feldspar plus rock fragments. This ratio will increase downstream from the source. The north and southeast Simm ler deposits have immature ratios of 0.39 and 0.22, respec tively, whereas the northeast deposits are submature at

The Simmler Formation unconformably overlies the un differentiated Cretaceous rocks and is unconformably over lain by either the Rincon Shale or the undifferentiated member of the Branch Canyon Sandstone (Figs. 5 and 6). The basal contact is a buttress unconformity as defined by

Bates and Jackson (1980) , whereas the upper contact is a disconformity as defined by Collinson and Thompson (1982, p. 17). The upper contact is recognized as a disconform ity on the basis of the lack of ~hallow marine deposits in the over lying formations, so that a small hiatus exists between the final deposition of the Simmler Formaton and the onset of deposition of the Rincon Shale or the undif ferentiated member of the Branch Canyon Sandstone. 33

The lower contact is easily recognizable when the underlying Cretaceous rocks are light-olive to brown, inter bedded sandstone and mudstone

Cretaceous rocks are light-olive, interbedded sandstone and conglomerate and the bedding attitudes do not notice ably differ, the contact is not so apparent and is then recognized on the basis that the Simmler contains sedimen tary clasts of reworked Cretaceous and Eocene rocks.

The unconformable upper contact is recognized by the sharp difference in lithology from the light-olive-gray conglomerate and sandstone of the Simmler to the light gray mudstone of the Rincon Shale or the very light-gray, medium-grained, calcareous, arkosic sandstone of the un differentiated member of the Branch Canyon Sandstone.

680 a wood fragment was also found. Shallow-water marine fossils at locality 682 include oyster fragments, regular echinoid fragments and spines, possible brachiopod spines, possible algae, and foraminifera {Plate 1). Foraminifera identified by Almgren from this locality include Cibicides cf. C. conoideus and rare poorly preserved recrystallized small specimens of Anomalina cf. A. glabrata, Pulvinulinella sp., and Gyroidina cf. G. soldani(?) (Appendix 2). Almgren 34 states that these foraminifera indicate an age for the

As described in the Cretaceous section, the Creta ceous conglomerate contains granite, gabbro, argillite, volcanic, and quartzite clasts. Eocene deposits, which crop out northwest of the Nacimiento fault and at one time may have over lain the Cretaceous deposits in the mapped area, contain beds of sandstone with lenses of granitic pebble and cobble conglomerate (Gower and others, 1966; Vedder and others, 1967).

On the basis of similar clast composition, the under lying Cretaceous and Eocene conglomerate beds are believed to be the main source for the granitic, volcanic, gneiss, and quartzite clasts of the Simmler Formation in the study area. The underlying Cretaceous and Eocene sandstone and mudstone are believed to be the source for the first-cycle sedimentary clasts. Because the conglomerate clasts seem to have been reworked from the nearby Cretaceous-Eocene rocks, it ·is logical to assume that these rocks also were the source for the sand grains that make up the sand stone in the Simmler. The larger sized and more angular granitic clasts, however, along with fresh, sand-size grains of plagioclase and microcline, may have come from a granitic source nearby •. 35

Mineralogically immature deposits reflect high rates of erosion which indicate the source area had high relief

(Pettijohn, 1975, p. 492). "The generation and preserva tion of thick sequences of conglomerates require substan tial topographic relief and thus usually imply tectonic activity during or immediately prior to deposition." (Read ing, 1978, p. 42).

Because a humid climate would lead to a high degree of decomposition and super maturity of the sediment, the immaturity of the Simmler indicates a semiarid to moderate climate of the source area.

Because the sediment making up the Simmler Formation probably came mainly from the sur rounding area, it was transported only a short distance. The granitic clasts and sand-size grains which came from a nearby granitic source may have been transported a little further.

Because no paleocurrent indicators were measured in the Simmler, there is no direct evidence of transport direction. Reineck and Singh (1980, p. 302) state that flowing water in stream channels deposits lenticular-shaped beds of poorly sorted gravel and sand. Wasson (1977) recog nized that water-laid stream sediment is deposited in poor ly sorted, lenticular-shaped beds, and is dominantly clast supported, but that some matrix-supported fabric can be present. High viscosity debris flows are characterized by deposits of matrix-supported, randomly oriented gravel and 36 are overlain by parallel-bedded sandstone (Reineck and

Singh, 1980, p. 301). Although some of the matrix- supported conglomerate may be debris-flow deposits, it is possible that the entire unit represents stream deposits.

Both stream- and debris-flow deposits occur on semi arid alluvial fans above the intersection point near the fan apex (Reading, 197 8, p. 20) • Further support for an alluvial-fan environment for the Simmler is that the de posits lack a significant fine-grained component, are mineralogically immature, locally derived, and have a red dish and greenish coloration. The red coloration is essen tially a diagenetic process and is obtained by the conver sion of iron minerals, such as biotite, to hematite (Read- ing, 1978, p. 41). This process takes place in a sub aerial environment and takes a long time. The 1 ight- olive-gray color, which is the predominant color, is the result of more rapid deposition of the water-laid sediment so that the minerals remained in a reduced state.

The northeast deposits of the Simmler Formation which contain the marine fossils represent an environment where alluvial-fan deposits are associated directly with coastal sediment such as described by Shepard and Dill (1966). In this environment the alluvial-fan sediment is deposited directly into and reworked by the ocean.

(1904) for sandstone cropping out in Los Vaqueros Creek, T. 20 s., R. 6 E., Mount Diablo base and meridian, Junipero Serra quadrangle, Monterey County, California. At the

stated that the type section had not been defined precise ly, so Thorup (1943) redefined the formation at the type

that is exposed in the southern portion of the study area was previously referred to as the Vaqueros Formation by

(Zemorrian to early Saucesian) age. This sandstone unit unconformably overlies the undifferentiated Cretaceous 38 rocks and conformably underlies the Rincon Shale. In the adjoining area to the west (Plate 2) the Vaqueros conform ably(?) overlies the Simmler Formation (previously shown to be similar to the Sespe Formation) and conformably under lies the Rincon Shale. On the basis of similiar lithology, stratigraphic position, and similarity in age to the type section of the Vaqueros Formation and because Dibblee (1966) assigned the rocks in the study area to the Vaqueros, the marine sandstone unit to be described herein is designated the Vaqueros Formation. Fritsche (1969) mapped the Vaqueros Formation in the

Sierra Madre area about 5 km (3 mi) northeast of the Naci miento fault. Yaldezian and others (1983) have shown that this formation as well as others can be correlated across the fault into the study area.

The Vaqueros Formation is exposed as a thin continu ous strip along the southern border of the study area and as an isolated outlier in the southeast (Plate 1). The

Vaqueros Formation is 137 m (450 ft) in thickness just east of the South Fork of the Sisquoc River and pinches out to the north in the subsurface.

The Vaqueros Formation consists totally of fine- to coarse-grained, calcareous, arkosic sandstone. A 1-m- 39 thick basal pebble-cobble conglomerate and some S-cm-thick pebble conglomerate beds are exposed in the Vaqueros For mation just to the west in Popelar 's thesis area (Plate

2) • The pebble conglomerate beds have scoured bases and contain planar and trough cross bedding which strike N57°W and dip 38°NE or 4 °SW. The northeast-dipping beds are more numerous. The lateral extents of the basal and pebble conglomerate beds into the study area are unknown. No basal conglomerate was actually mapped in the study area, however, rounded igneous clasts averaging cobble size (7 em) were seen in the slope wash at the base of an outcrop of Vaqueros Formation in South Fork of the Sisquoc River

Cretaceous interbedded mudstone and sandstone (turbidites) and, therefore, may represent a basal conglomerate which is covered by slope wash. The clasts may have come from lenses of Upper Cretaceous conglomerate exposed near-by to the east and west (Vedder, personal communication).

Rocks of the Vaqueros Formation are moderately well indurated, resistant, and form prominent cliffs (Fig. 11).

Vegetation on the rocks is sparse and is only really notice able in areas of lesser resistance. The rocks are slight ly jointed and fractured. Fine-grained sandstone is spheroi dally weathered in places.

Color of the sandstone on a fresh surface ranges from yellowish gray (5 Y 7/2) to pale yellowish brown (10 YR

Figure 11. Resistant 4. 5 m <15 ft) high sandstone outcrop of the Vaqueros Formation exposed along the west bank of the South Fork of the Sisquoc River about 1.5 km southwest of South Fork Campground. Notice cross bedding near the base of outcrop.

Figure 12. Cross bedding as seen in the Vaqueros Formation in Popelar's thesis area just west of the east border of the study area. 41

(10 YR 7/2) to moderate yellowish brown (10 YR 5/4) and some pale red (10 R 6/2). Bedding in this unit is not always well defined but can be massive, thick (1 m) to thin (5 em) parallel bedded, or in places cross bedded (Figs. 11 and 12). Cross bedd ing occurs in beds up to 35 em thick, is prominent near the base of the formation, and is defined by changes in grain size. Parallel bedding is defined by changes in grain size and by changes in degree of cementation. Bedding planes can be vague and gradational but also can be sharp. The average sandstone composition is arkosic (Fig. 13) and consists of about 40% quartz, 25% cement of various kinds, 21% feldspars, 9% granitic rock fragments, 4% other rock fragments

---~--...... I .•· . . . \· f -:-::·.-:·:-. . . . . " ...... •...... ' ','.'. ·\ -:·:·:·.·:·l·:·:·:·:·. F :: _··.:. ::_ ... I \ • • ...• ' ~ -·• •l'l ..' R 3:1 1:1 1:3 RATIO FIR

Figure 13. Ternary diagram showing sandstone composi tion in the Vaqueros Formation. Classification scheme is from Folk (1974). Localities shown on Figure 7. <•=sand• stone) •

with minor amounts of mica. Volcanic rock fragments are usually well rounded and weathered. Grains of glauconite are present in minor amounts. Calcite cement of the granular spar i te type is the predominant cement in most rocks and has crystals ranging in size from fine (0.016 mm) to coarse (1 mm). Some grains of quartz and feldspar are replaced by calcite. Minor amounts of calcite cement show poikilotopic texture, which 43

TABLE 2. PERCENI' CXlotFOSITION AID TEX'ruRE OF SIX SANDS'IONE SAMPLES F!Oot THE WJJ(JEROS FORMATION

4 SANDS'lONES LCX:ALITY~ 33s 34A 34A' 38 39 46 GRAIN§: Quartz 45 29 42 39 16 33 Orthoclase 18 13 12 12 7 8 Plagioclase 13 11 8 8 5 7 Microcline t t t 4 t 2 Granitic rock fragments 9 11 10 9 4 Volcanic rock fragments 4 5 2 4 2 Metairorphic rock fragments 2 1 Sedimentary rock fragments t t Chert 1 2 2 Biotite t t t Muscovite t Ilmenite t Magnetite t 4 Leucoxene t t t Glauconite 2 t t FOSSIL FRJ!GMENI'S: 10 3 CEMENTS: Calcite 8 10 8 47 Hematite 1 10 5 3 Limonite 8 3 2 Clay 7 t Feldspar overgrowths t Chert t 61 Q=F-R: 1 Q 50 40 56 50 45 66 F 45 48 39 42 47 34 R 5 12 5 8 8 GRAIN SIZE: 0.25- 0.125- 0.25- 0.25- 0.25- 0.125- Range 0.5 1.0 0.5 1.0 1.0 0.5 Average 0.35 0.35 0.35 0.4 0.35 0.3 2 SORTIN:i: m-w m m m m m-w ROUIDIN:i: 3 sr sa-sr sa-sr sa-sr sa-sr sa-sr GENERAL SUMMARY: Percent grains 89 72 82 78 35 50 Percent fossils 10 3 Percent cements 9 25 18 10 64 47 Percent porosity 2 3 2 1

Footnotes: 1) Q + F + R = 100 follows Folk <1974); 2) m=moderte, w=well; 3) sa=subangular, sr=subrounded; 4) stained for orthoclase. Symbols: t=trace, - =absent. Localities shown on Figure 7. 44 is commonly referred to as luster-mottled texture (Scholle,

1979, p. 119). Hematite and/or limonite cement is also common in the rocks, whereas leucoxene and clay cement and feldspar overgrowths are uncommon. Bedded chert makes up most of the rock from locality 39.

Mineralogic maturity is defined by Pettijohn <197 5, p. 492) as being the ratio of quartz plus chert to feldspar plus rock fragments. The rocks of the Vaqueros on the average are mineralogically submature with a ratio of 1.0.

The Vaqueros Formation unconformably overlies the undifferentiated Cretaceous rocks and is conformably over lain by the Rincon Shale or the undifferentiated member of the Branch Canyon Sandstone. The buttress unconformity is easily recognized by the differences in lithology between the two units when there is not a noticeable difference in bedding attitudes. The upper contact with the Rincon

Shale is easily recognizable due to the different litholo gies of the two units. The upper contact between the

Canyon Sandstone is approximately located (Plate l) be cause the similarity of rock types in the two units makes recognizing the contact difficult. Differences between the two units are that the Vaqueros is cross bedded and the

Branch Canyon is not, and that the Branch Canyon usually looks whiter in outcrop. 45

Broken regular echinoid spines found at c.s.u.N. fos sil locality 684 (Plate 1) were the only fossils found in the Vaqueros in the study area. In the adjoining area to the west at thin-section locality 38 (Fig. 7), the

Vaqueros contains regular echinoid spines, barnacle frag ments, other shell fragments, and is bioturbated near the top of the formation.

Vaqueros is younger than the Simmler Formation (late Zemor rian to early Saucesian) which it unconformably overlies and is older than both the Rincon Shale (early Saucesian to Saucesian) and the undifferentiated member of the Branch

Canyon Sandstone (early Saucesian to Saucesian). The Vaque ros also is similar in age to parts of the Rincon Shale and the undifferentiated member of the Branch Canyon Sand stone (Figs. 5 and 6). Therefore the Vaqueros Formation in the study area is assigned an age of possible late Oligo cene(?) to early Miocene (late Zemorrian to early Sauce sian) •

Sand-size rock fragments in the Vaqueros Formation have the same composition as the rock fragments . in the

Simmler Formation. Fresh grains of plagioclase and microcline are present in the Vaqueros as they are in the 46

(Fig. 13), whereas composition of the Simmler sandstone is lithic arkosic (Fig. 10). These differences in composi tion are due mainly to changes in the depositional environ ments. Therefore, the source of sediment for the Vaqueros is the same as it was for the Simmler Formation; namely the underlying Cretaceous and Eocene rocks and a minor nearby granitic source. The Simmler may have also been a minor source of reworked sediment.

Differences in clast size and mineralogic maturity also exist between the two formations. Conglomerate which was abundant in the Simmler is absent in the Vaqueros.

The mineralogic maturity ratio increases from an average of 0.3 for the Simmler to an average of 1.0 for the Vaque ros. These changes between the two formations can be accounted for in the following ways: 1) a change in cli mate of the source area, 2) a change in relief of the source area, 3) a change in the distance of transport, 4) a change in time of exposure to weathering (maturing) pro cesses, or 5) a change in the intensity of action on the sediment. There is no evidence to indicate that the cli mate was still not semiarid to moderate as it was during deposition of the Simmler. The erosional processes respon sible for the deposition of the Simmler probably produced an area of moderate relief so the relief of the source area was reduced. Subangular to subrounded sand-size grains indicate a short to moderate distance of sediment trans- 47 port. Sediment in the Simmler as previously discussed also had a short distance of transport so there was no great change in distance of transport. Sandstone in the

(Tables 1 and 2). The increase in the mineralogic maturi ty ratio from 0.3 for the Simmler to 1.0 for the Vaqueros is due to the fact that the Vaqueros sediment was exposed to longer and more intense maturing processes, i.e., wave action (Pettijohn, 1975, p. 492). Therefore in summary the decrease in clast size and increase in mineralogic maturity from the Vaqueros to Simmler is explained by the change from the alluvial fan environment of the Simmler to the shallow water marine environment of the Vaqueros.

The few fossils found in the Vaqueros Formation as described above indicate that the unit was deposited in a shallow-water marine environment of normal salinity. The rarity of fossils may be the result of a high rate of sedimentation which would be unfavorable for marine life.

Vaqueros also indicate a shallow-water marine environment as did the fossils. Cross bedding seen in the unit indicates a bimodal current direction of N34°E. The cross beds dip steeper to the southwest than to northeast. The presence of the Cretaceous rocks and absence of the middle

Tertiary-aged rocks to the southwest indicates that a high land existed during this time to the southwest. Reineck and Singh (1980) and Reading (1978) state that cross bed- 48

ding with a higher dip value landward may be indicative of the upper shoreface, whereas parallel bedding can be found in the lower shoreface and foreshore. The clasts seen in the slope wash at the base of the outcrop of Vaqueros seen in figure 11 could represent a basal conglomerate. This basal conglomerate could represent a beach face deposit. The increase in bioturbation towards the top of the unit may indicate a deepening of the water level as one goes farther offshore like that described by Reading <1978). Therefore the sedimentary structures, and fossils found in the Vaqueros Formation represent shallow-water marine deposits mainly of the shoreface, but also of the foreface and beachface(?). Cross sections (Plate 1) show that the geometry of the Vaqueros Formation may be considered a sheet sand deposit which formed by lateral sedimentation and there fore does not represent the same age everywhere {Pettijohn, 1975, p. 146). This supports the idea that the Vaqueros which is equal in age to parts of the Rincon Shale and .the undifferentiated member of the Branch Canyon Sandstone represents a time-transgressive shallow-water marine sand stone deposit. After deposition, the Vaqueros Formation was compacted and cemented.

RINCON SHALE Nomenclature The Rincon Shale, as originally defined by Kerr <1931), 49 consists of marine, gray shale which contains dolomitic concretionary layers. The formation is 655.5 m (2,150 ft) thick at the type section exposed along Los Sauces Creek east of Rincon Mountain, Ventura County. At the type sec tion Kerr (1931) states that the Rincon conformably over lies the Vaqueros Formation and conformably underlies the bentonite bed at the base of the Modelo Formation (Mon terey Formation). Kleinpell <1938) describes the Rincon

Shale as containing Saucesian foraminifers in the type section and uses this type section of the Rincon to define the Saucesian Stage.

The rocks described below consist mainly of marine, gray mudstone with minor amounts of yellowish-gray sand stone and carbonate rocks and contain foraminifera which indicate an age of early Miocene (early Saucesian to Sauce sian). These rocks cannot be directly traced from the study area to the type section of the Rincon Shale, but because they are similar in lithology and relative age to the rocks at the type section of the Rincon Shale they are herein assigned to the Rincon Shale.

Madre Mountain area by Fritsche (1969) have been shown to correlate across the Nacimiento fault and into the study area by Yaldezian and others (1983). 50

Canyon Sandstone. The majority of the formation is exposed as a continuous band which wraps around the nose of

the Hurricane Deck syncline. The formation reaches a maxi mum thickness of 305 m (1000 ft) and laterally pinches out

' i 51 with the mudstone throughout the formation. The carbonate rocks which form beds of concretions of limestone or dolo stone are evenly dispersed throughout the formation. Mud stone and carbonate rocks may be very similar in appearance in the field and in places only by thin-section analysis can one determine the exact lithologic difference. The mudstone in the Rincon which overlies the Vaqueros Forma tion in the south or the undifferentiated Cretaceous rocks in the northeast may show a slight fining-upward pattern.

The unit generally is poorly exposed and forms slopes covered with vegetation (Fig. 14), except for fresh expo sures in stream or river cuts (Fig. 15). The sandstone and carbonate rocks are more resistant than the mudstone and usually are well bedded. The mudstone is poorly resis tant, crumbles easily, forms talus slopes, and is spheroi dally weathered in places. The unit contains some secon dary fractures.

The typical color of the mudstone in the Rincon is medium gray (N5). The typical color of the sandstone is yellowish gray (5 Y 7/2). Color of the mudstone on a fresh surface ranges from light gray (N 7) to dark gray (N 3) and some yellowish gray (5 Y 7/2). The color of the mud stone on a weathered surface is the same as that for a fresh surface except for some pale yellowish brown (10 YR

Figure 14. Brush covered slopes of the Rincon Shale overlain by resistant sandstone of the undifferentiated member of the Branch Canyon Sandstone which is overlain by a small poorly exposed outcrop of undifferentiated Mon terey Shale. View looking east across the Sisquoc River seen in the foreground.

Figure 15. Fresh exposure of horizontally-bedded Rincon Shale exposed along the east bank of the Sisquoc River. Notice sandstone dike which is almost perpendic ular to bedding. 53 54 and on weathered surfaces from very light gray (W 8} to yellowish gray (5 Y 7/2) to pale yellowish brown (10 YR

6/2} with some moderate yellowish orange (10 YR 7/6} staining. Carbonate rocks range in color on fresh sur faces from yellowish gray (5 Y 7/2} to medium gray (N 5} and on weathered surfaces from pale yellowish brown (10 YR

Bedding in the unit, as stated above, is usually de fined by interbeds of sandstone or concretions (Fig. 15}.

The mudstone is usually structureless but may contain poor ly developed thin (8 ern} to thick (1 m) parallel bedding, parallel laminations, cross laminations, or wavy bedding.

Sandstone usually is thin (7 em} to medium (20 m}, parallel or wavy bedded, and may show pinching and swelling, or form lenses 5 to 20 ern thick. However, very thick lenses

(>2 m} of sandstone which contain mudstone rip-up clasts exist near the gradational contact with the undifferen tiated Branch Canyon Sandstone in the Sisquoc River area to the north. Also exposed in this area are some thin

(5-10 em} beds of pebbly sandstone. Sandstone dikes, such as that shown in Figure 15, are present throughout the formation and are up to 40 ern wide. A few slump folds were also seen.

(i.e., rocks which contain both silt and clay size sediment as defined by Folk (1974)). The average mudstone is arkosic 55

::-:.:..-:----:--- ... : . :- ··.·>_-_ -:- . ---"~ .,_ I...... t·· .. ·__ ·_·· ...· .. ... ' ... , '

::-:-:-·.:-:::... ._·. ·.: :\·.--· ·. \ /'·.: -- . ··1- I -:-:·:-:-:.:-:\ . ..•...... " ..... , ' .. :-:-:-.. ~~- .. :-·-:-:- ... <·>.... ·... :. F <;::_~\::::>>. ::::.:. . . . -:-:. ·::.:.:::~~:::)>:., R 3:1 1:1 1:3 RATIO FIR

Figure 16. Ternary diagram showing sandstone, mud stone, and carbonate composition in the Rincon Shale. Classification scheme is from Folk (1974). Localities shown on Figure 7. <•=sandstone, o=mudstone, and A = carbonate).

(Fig. 16) and consists of about 45% clay; 25% cement (mainly calcite, dolomite, or hematite types); 22% silt-size grains which are predominantly quartz and feldspar, but may be up to as much as 12% authigenic pyrite; 3% foraminifera; and a trace of phosphate (fish bones or scales) (Table

3). The silt-size grains are subangular to subrounded and well sorted. Sample 26 has alternating red (hematite) and dark gray to black (pyrite), 4-mm-thick laminations. 56

,,...... , ...... ~ ~ ~ _ 19 20 35 4 26 28 42 21 22 36 GRAINS: 0-lartz 25 26 24 3 12 3 24 4 5 4 Orthoclase 12 15 13 2 3 1 8 2 2 1 Plagioclase 12 15 12 1 3 7 1 1 1 Microcline 4 4 4 t Granitic rock fragments 12 11 8 1 5 1 1 1 Volcanic rock fragments 8 4 17 1 2 1 1 1 MetaiOOq;:tlic rock fragments 4 4 t 1 t Sedimentary rock fragements 2 Chert 1 Biotite 1 t t fll.lscOvite t t t Magnetite t t Pyrite 10 12 9 12 1\patite t t Sphene t Leucoxene t t 1 Phosphate t t t t t t t 1

CEMOO'S: Calcite 20 21 15 4 1 81 t 75 Hematite 11 8 5 4 6 Limonite 3 2 Clay. 17 2 2 Chert t t 1 2 t 3 5 t 2 Dolanite 29 68 Q::f::B:l 0 32 35 30 50 60 75 50 44 so 50 F 51 60 45 50 35 25 42 45 40 37 R 17 5 25 5 8 11 10 13 GRAIN SIZE: 2 0.125- 0.125- 0.25- 0.004- 0.004- 0.002- 0.004- 004- 0.004- .004- Range (nm) 4.0 1.0 0.5 0.06 0.06 0.06 0.125 0 0.062 0.016 Average (nm) 0.35 0.35 0.35 0.025 0.025 0.006 0.035 008 0.008 '.008

SOR'I'IN:i: 3 m m, m w w w m-w Remi)IKJ:4 sr sa- sa- sa- sa- sa- sa- sa- sa- sa- sr sr sr sr sr sr sr sr sr

GENERAL Sl.JIIIoiARY: Percent grains 80 75 83 6 30 16 57 9 22 8 Percent clay 57 45 46 32 1 10 3 Percent foraminifera t 5 5 2 10 t t 5 Percent cements 20 24 14 31 20 36 1 90 68 83 Percent porosity 1 3 1 1

Footnotes: ll Q + F + R " 100 follows Folk <1974); 2) this equals crystal size for carbonates; 3) ~erate, w-well; 4) sacsubangu1ar, srasubrounded. Symbols: t=trace, - =absent. UX:alities shown on Figure 7. 57

Granular sparite is the dominant calcite cement and has crystals ranging in size from very fine (0.004 mm) to fine (0.062 mm). Dolomite cement abundant in sample 28 also has crystals ranging in size from very fine to fine.

Foraminiferal tests have been replaced by granular sparite and are filled mainly with sparite. Some are filled with chert and pyrite.

The average sandstone composition is arkosic to lith ic arkosic (Fig. 16) and consists of about 30% feldspars,

25% quartz, 13% other rock fragments (volcanic, metamor phic, and sedimentary types), 11% granitic rock fragments,

20% cement (mainly clay, calcite, and hematite types), 1% porosity, and a trace of other detrital grains (Table 3).

The sandstone is texturally submature, averages medium grained, but ranges from fine to coarse grained, may con tain pebbles, and has a closed framework. Grains are sub angular to subrounded and moderately sorted.

All kinds of quartz grains are present. Orthoclase grains are weathered to clay (sericite?). Some fresh grains of plagioclase and microcline are present. Granitic rock fragments have the same composition as the granitic clasts in the Simmler Formation. Volcanic rock fragments which are unusually abundant in sample 35 are well rounded and weathered.

The mineralogical maturity of the sandstone deposits is immature to submature at 0.5. 58

The carbonate rocks which form concretionary beds are believed to have formed by the recrystallization of micrite and are therefore called microspar i te or recrystallized dolostone (Folk, 1974). The carbonate rocks consist pre dominantly of either calcite or dolomite and contain minor amounts of silt-size grains, clay matrix, and other ce ments. Sample 22 contains a noticeable amount of autheni genic pyrite, whereas samples 21 and 36 contain some hema tite cement.

The Rincon Shale unconformably overlies the undifferen tiated Cretaceous rocks in the north and the Simmler

Vaqueros Formation in the south and interfingers with the undifferentiated member of the Branch Canyon Sandstone, and is in fault contact with the undifferentiated Creta ceous rocks and Eocene rocks in the northeast (Plate 1) •

The stratigraphically youngest deposits of the undifferen tiated member of the Branch Canyon Sandstone conformably overlie the Rincon Shale. The basal contact with the Simm ler and Vaqueros has been previously described. A but tress unconformity separates the Cretaceous rocks from the overlying Rincon in the north. The basal and upper con tacts with the Branrih Canyon are usually gradational, but they may be sharp when there are no sandstone beds in the

Rincon. In the Sisquoc River area to the north, the basal 59 contact with the Branch Canyon is gradational over 100 m

(328 ft) and is placed where there is greater than 50% mudstone ~n the Rincon. The upper and lower contacts with the Branch Canyon in the south are gradational over 4 m

Fossils and Age Traces of fish bones and scales, and perhaps some type of plant fragments, are the only macrofossils found in this unit. Benthic foraminifera are found throughout the unit. Almgren states that foraminifera found in micro fossil samples 9, 13, 15, 18, 22, 27, and 28 (Plate 1) strongly indicate an age of early Miocene (early Saucesian to Saucesian) and bathyal to lower bathyal water depths (Appendix I). Ingle (1975) states that the lower bathyal zone ranges in depth below sea level from 2,500 m (8,200 ft) to 4,000 m (13,120 ft). Filewicz states that calcar eous nannofossils identified from microfossil samples 9, 13, 22, and 28 are indicative of the early Miocene

Spherolithus belemnos Zone (Appendix I). Rare to sparse sponge spicules are also present in the rocks. The interfingering of, and the gradational nature of, the contacts between the Rincon Shale and the undifferen tiated member of the Branch Canyon Sandstone suggest they are the same age. However, the stratigraphically lowest unit of the Rincon is older than any Branch Canyon rocks, 60

The sandstone in the Rincon is similar in composition to the sandstone in the Vaqueros. Fresh grains of plagio

Therefore the sandstone deposits were not subjected to the maturing processes for very long.

rent energy may have been due to the development of a re- 61 stricted basin or to an increase in water depth. Sand- stone deposited in the Rincon with the same composition as

Vaqueros sandstone rules out the idea of a restricted basin. Microfossils and calcareous nannofossils found in the Rincon indicate a marine environment with bathyal to lower bathyal depths. The Vaqueros is a shallow water deposit and therefore suggests the change in current ener gy is due to an increase in water depth.

No paleocurrent indicators were measured in the Rin con, so there is no direct evidence of transport direc tion.

Collinson and Thompson (1982, p. 152) state that py rite forms in a strongly reducing environment and can be present in sediments just a few centimeters below the sur face. The alternating laminations containing hematite and pyrite found in thin-section 26 probably indicate that an oxidizing environment which produced the hematite existed at the surface, whereas a reducing environment producing pyrite existed just below the surface.

The interfingering of the Rincon Shale and the undif ferentiated member of the Branch Canyon Sandstone which is interpreted as submarine-fan channel deposits (see origin section for undifferentiated member of the Branch Canyon

Sandstone) indicates that the Rincon Shale in the study area probably represents interchannel and slope deposits.

The unit was deposited in a submarine-fan environment which was infilling a California Borderland-type basin. 62

The thick beds of sandstone which are lens shaped and contain some pebbly beds and abundant large mudstone rip-up clasts are indicative of grain flow deposits (Mutti and Ricci Lucchi, 1978; Reading, 1978). Middleton (1970) states that the angle of slope needed for sustained grain flow is high; i.e., some 18° or higher. Present day California Borderland basins have slopes with fault scarps up to 30° and are surrounded by both deep-sea fans and slumped slope deposits (Reading, 197 8, p. 3 87, 3 95; Gor- sline and Emery, 1959). The few slump features found in the Rincon probably resulted from mass movement down such steep slopes as described above.

The thin- to thick-bedded, and in some places parallel- laminated, mudstone which is interbedded with fine-grained sandstone and carbonate rocks, might have been deposited by low-density turbidity currents. Reading (1978) states that these low-density turbidity currents can be produced by storm waves on the shelf or by the development of a dilute tail to a high-density turbidity current which could be responsible for the deposition of the fine- grained sandstone beds. No Bouma T sequences were c-e found in these rocks therefore the rocks are most likely the product of deposition by storm waves and not turbidity currents. The sandstone beds could also have been deposited by traction currents, primarily under lower-flow regime conditions (Mutti and Ricci Lucchi, 1978). The thick units of structureless to parallel-bedded mudstones, which lack 63

layers. Sandstone dikes present in the study area form as sand from an under lying source is injected due to over lying pressure into uncompacted sediment through a frac ture or area of poorly developed resistance (Collinson and Thompson, 1982, p. 141). These sandstone dikes are can be found in slope deposits.

The submarine-fan model proposed here differs from the submarine-fan models described by Walker (1978) and Mutti and Ricci Lucchi <1978). In their models sediment col lects at the head of a submarine canyon near shelf break.

A storm, earthquake, or other triggering event, then trig gers the movement of sediment down a submarine canyon

The model described here for the rocks in the study area is one that is characterized by a high rate of sedi mentation, steep slopes, and the possible absence of a broad shelf. Evidence for the absence of a broad shelf comes from the fact that in the north and northeast the

Rincon rests unconformably on the Simmler Formation and undifferentiated Cretaceous rocks. In the absence of a broad shelf, sediment is transported directly down the slopes. The situation developed in this example would not be conducive to the orderly development of one main feeder 64 channel but rather a more chaotic development of feeder channels which transport sediment into the basin. The basin which the submarine fan was infilling was not par ticularly large. This coupled with its other features makes it nonconducive to the formation of "classical tur bidites" formed by turbidity current mechanisms, and common ly found in the models described by Mutti and Ricci Lucchi (1978) and Walker <1978).

In the eastern part of the study area where the Branch Canyon represents possible shelf deposits (see ori gin section for Branch Canyon) the environment is somewhat different. Basin slopes may not be as steep and sediment may be transported down the slopes through a more organ ized channel system.

In the south part of the study area, the Rincon is situated between the shallow-water marine deposits of the

Vaqueros and the submarine channel deposits of the Branch

Canyon. These units were simultaneously deposited in their respective environments during an eastward transgression of the sea. Figure 17 shows the eastern extent of this transgression for the stratigraphically oldest Rincon deposit. Stratigraphically younger deposits of Rincon were deposited over the underlying unconformity surface (Figs.

5 and 6) showing that by this time the entire basin was sub- merged. The gradational nature of the Rincon - Branch

Canyon contact in the Sisquoc River area to the north and in the interfingering of the same units to the west may N MN

c,.e, lice / ollll / / ....._.._ __ / / / Middle Tertiary y / / /

0 6000 FT

....-~.....---.-- -1 ------~--- _ 0 1500 M

- j_- ZERO ISOPACH APPROXIMATELY LOCATED ARROWS INDICATE DIRECTION OF THICKER DEPOSITS

Figure 17. Zero isopach of the stratigraphically oldest deposit of Rincon Shale. Shows extent of eastward transgression for this time per iod.

"'U1 66

represent alternating periods of channel deposition and

interchannel deposition.

After deposition, the Rincon Shale was compacted and

cemented. Recrystallization of micrite occurred after

deposition and may still be occurring.

UNDIFFERENTIATED MEMBER OF THE BRANCH CANYON SANDSTONE

Nomenclature

The Branch Canyon Formation was originally defined by

Hill and others <1958) for a marine sandstone unit which

graded laterally westward into the Monterey Shale and later

ally eastward into the terrestrial Caliente Formation.

The formation is 915 m (3,000 ft) thick at the type sec tion (sec. 2., T. 9 w., R. 27 w., Cuyama Ranch quadrangle) where it unconformably overlies Cretaceous rocks and con

formably underlies shale of the Santa Margarita Formation.

Rocks at the type section consist mainly of gray-white to

tan, medium-grained, fossiliferous, arkosic sandstone with

some calcareous "reefs" and are Relizian to Luisian in age (Hill and others, 1958). The u.s. Geological Survey adopt ed the usage of Hill and others (1958) but modified the name to Branch Canyon Sandstone because the unit is com posed mainly of sandstone (Dibblee, 1973). Southeast of the type section, the unit is separated into two informal members by a 229-m-(750-ft)thick section of Monterey Shale.

Fritsche (1969) mapped Miocene age rocks in the Sierra

Madre area just across the Nacimiento fault about 5 km (3 67 mi) to the north-east of the study area. The type section of the Branch Canyon is located in his study area. In this area he mapped the two informal members of the Branch

Canyon and stated that in the absence of the tongue of Monterey, the two members in some places were difficult to distinguish. Van Wagoner (1981) correlated outcrops of yellowish-gray marine sandstone exposed about 22 km (13 mi) to the west, in the Zaca Lake quadrangle, Santa Barbara

County, to the Branch Canyon Formation. These rocks can be traced into the study area on the reconnaissance map by Vedder and others (1967).

The rocks described below consist mainly of 1 ight gray, marine, arkosic sandstone and are early Miocene

(early Saucesian to Saucesian) in age. They unconformably overlie the undifferentiated Cretaceous rocks and the Simm ler Formation, conformably overlie the Vaqueros Formation, conformably overlie and interfinger with the Rincon Shale, and are conformably overlain by the unnamed Miocene unit and the undifferentiated Monterey Shale. Yaldezian and others (1983) have shown that these rocks can be traced almost continuously from the type section at Branch Canyon across the Nacimiento fault and into the study area. There fore, the rock unit described below which is older and differs slightly in lithology, but is traceable from the type section, will be designated the undifferentiated member of the Branch Canyon Sandstone. 68

Distribution and Thickness

Rocks from the undifferentiated member of the Branch

Canyon Sandstone cover about 50% of the mapped area (Plate

1). The unit interfingers with the Rincon Shale in the study area. The majority of the unit is exposed as a con tinuous band which wraps around the nose of the Hurricane

Deck syncline. The stratigraphically oldest rocks of the undifferentiated member of the Branch Canyon Sandstone crop out in the north and southwest and are separated from the major exposure of the unit by "fingers" of Rincon Shale.

These "fingers" of Rincon laterally pinch out to the west allowing the unit to thicken and cover about 80% of the adjoining area (Plate 2). Both of the stratigraphically oldest deposits pinch out to the east. Small deposits of the undifferentiated member of the Branch Canyon Sandstone are exposed in the core of the Hurricane Deck syncline and in the core of an anticline which is in a down-dropped fault block in the southeast. Rocks of this unit are also exposed in the eastern part of the mapped area along the

Nacimiento fault.

The undifferentiated member of the Branch Canyon Sand stone ranges in thickness from 0 to 503 m (1,650 ft). The unit obtains its maximum thickness of 503 m (1,650 ft) on the south limb of the Hurricane Deck syncline in the western part of the mapped area. 69

Lithology The undifferentiated member of the Branch Canyon Sand stone consists of about 92% light-gray arkosic sandstone, 5% interbedded gray mudstone, and 3% pebble conglomerate. The mudstone is exposed as thin interbeds in the sandstone throughout the formation. The pebble conglomerate beds crop out in the stratigraphically oldest unit exposed in the north and in between the Rincon and unnamed Miocene unit in the southwest. The southernmost exposure of the undifferentiated member of the Branch Canyon Sandstone was never looked at in detail by the author, however Vedder (personal communication) says that local thin lenses of pebble conglomerate do occur in this area. The pebbles are mostly less than 2 em in diameter. Figure 18 shows typical exposures of the unit and Figure 19 shows an outcrop that is vaguely horizontally bedded and has differential and cavernous weathering. The rocks are usually moderately to well indurated, resistant, and form prominent ridges and cliffs which are easily notice able on aerial photographs. Concretionary beds or rocks which are calcareously cemented are more resistant than the aver age rock and define bedding in places. Finer grained sandstones and rocks of poorer resistance and in duration can be heavily covered with brush (Figs. 18 and 20). Rocks become less resistant and indurated near the upper contact with the unnamed Miocene unit. The unit 70

Figure 18. Looking north (dip direction) at typical exposures of the undifferentiated member of the Branch Canyon Sandstone which represent multistory submarine-fan channel deposits. Beds thicken and thin and laterally pinch out.

Figure 19. Sandstone outcrops of the undifferen tiated member of the Branch Canyon Sandstone which show vague horizontal bedding and differential and cavernous weathering.

------71

Figure 20. Resistant sandstone outcrop of the undiffer entiated member of the Branch Canyon Sandstone overlain by a lesser resistant finer grained Branch Canyon deposit which is heavily brush covered. View is looking northwest along direction of strike.

contains some secondary fractures which are filled with calcite in some places. Color of the sandstone on a fresh surface is mainly very light gray (N8), but can be grayish orange (10 YR 7/4), very pale orange (10 YR 8/2), or yellowish gray (5 Y 7/2). On weathered surfaces color of the sandstone ranges from very pale orange (10 YR 8/2) to pale yellowish brown (10 YR 6/2) to pale yellowish orange (10 YR 8/6) with occa- 72 sional light brown (5 YR 5/6) • Color of the mudstone on a fresh surface ranges from light brownish gray (5 YR 6/1) to dark gray (N 3) and on weathered surface ranges from grayish orange <10 YR 7/4) to pale yellowish brown (10 YR 6/2) to dark gray (N 3). The pebble conglomerate is usual ly light gray (N 7). The majority of the unit is sandstone which is usual ly medium bedded (10 to 30 ern) to very thick bedded (~ 1 rn) and void of sedimentary structures. Bedding contacts are planar-parallel, curved-parallel, and irregular and are usually defined by slight grain-size variations but may be defined by thin (1 to 10 ern) interbeds of mudstone. The beds of sandstone are stacked on top of each other to form units up to about 10 rn thick. These units of amalga mated sandstone beds are laterally discontinuous (Fig. 18) but can be followed on aerial photographs for distances up to about 3.2 krn (2 rni). The pebble conglomerate, when present, is medium bedded (10 to 30 ern) to thick (30 to 100 ern) bedded. The sandstone beds which are usually void of sedimentary structures can contain such sedimentary structural features as: 1) channels with scoured bases that may contain rip-up clasts (up to 30 ern in length) and are filled with graded beds of pebble conglomerate (Fig. 21); 2) load casts (Fig. 22); 3) beds with non-erosive bases and tops that contain large

Figure 21. Pebble channel with erosive base in the undifferentiated member of the Branch Canyon Sandstone. Bed is slightly graded upwards. Fifteen ern (6 in) rule for scale.

Figure 22. Load features in the undifferentiated member of the Branch Canyon Sandstone which are tipped to the southwest and may indicate sagging in that direction. Granola bar used for scale is about 15 ern (6 in) long. 74

Figure 23. Large mudstone rip-up clasts dispersed throughout a sandstone bed in the undifferentiated member of the Branch Canyon Sandstone exposed along bank of the Sisquoc River in northern part of study area. Rock hammer used for scale is about 25 em (10 in) long.

Figure 24. Flame structure, approximately 30 em Cl ft) in height, and parallel laminations in fine-grained sandstone in the undifferentiated member of the Branch Canyon Sandstone. Fifteen em (6 in) rule for scale. 75

5) thin to medium thick beds of fine- to medium- grained

sandstone which contain parallel laminations and flame structures (Fig. 24); 6) thin beds of fine-grained sand

stone containing parallel laminations and contorted bed ding {Fig. 25); 7) rare slump folds (Fig. 26); 8) pale yellowish-brown (10 YR 6/2) limestone concretionary beds; 9) rare bioturbation; 10) low-angle planar cross bedding and one large set of channel fill cross beds (exposed in the east); 11) low-angle tabular cross bedding and ripple cross-bedding (exposed in beds in the core of the Hurri cane Deck syncline); and 12) low-angle, wedge-shaped cross bedding, some high-angle cross bedding, graded beds 6 to 8 em thick, and some mudstone rip-up clasts 2 to 4 ern in length (exposed in the bed resting on the unconformity surface seen in Fig. 27).

The average sandstone is a very light-gray, medium grained, submature arkose (Fig. 28}, which has an average composition of about 35% quartz, 30% feldspar, 10% grani tic rock fragments, 5% lithic rock fragments

Figure 25. Convolute bed of fine-grained sandstone overlain by 5 ern thick mudstone bed in the undifferenti ated member of the Branch Canyon Sandstone. Also note mudstone rip-up-clasts below convolute bed. Fifteen ern (6 in) rule for scale.

Figure 26. Small scale fold in the undifferentiated member of the Branch Canyon Sandstone which may represent slump folding within a submarine-fan channel. Hammer shown for scale is about 30 ern (1 ft) long. 77 78

Figure 27. Unconformable contact between Cretaceous turbidites and over lying thin deposit of the undifferen tiated member of the Branch Canyon Sandstone which is con formably overlain by Rincon Shale. Outcrop exposed about 610 m (2,000 ft) west of South Fork Campground in cut bank of the Sisquoc River. View is looking west. Note that contact is not sharp but is irregular.

cally submature with a ratio of about 0.9. Sample 30 differs from the average sandstone by having a mineralogic maturity ratio of 0. 5 and by containing less quartz and more lithic rock fragments (particularly sedmentary rock fragments) which results in a 1 i thic arkosic composition (Fig. 28). The mineralogic maturity ratio of sample 25 is 0.6. Pebbly sandstones also are present in the formation. Quartz grains are predominantly of the common type; i.e., single grains with single extinction. Some quartz grains have slightly undulose extinction and there are a few composite grains with undulose extinction. Orthoclase 79

Q -QUARTZARENITE

24 ·:·:te-: G ·. ~ t4 130:- of•. • . ·.: 16· ... -.. t -•r '17 •· . . ::. ·.• •s.

... •\ .. ;,

3:1 1:1 1:3 AAT10 FIR

Figure 28. Ternary diagram showing sandstone, mud stone and carbonate composition in the undifferentiated member of the Branch Canyon Sandstone. Classification scheme is from Folk (1974). Localities shown on Figure 7. <•=sandstone, o=mudstone, ~ =carbonate). grains have weathered into clay. Some fresh grains of plagioclase and microcline are present. Granitic rock fragments are of the light colored felsic type as found in the Rincon, Vaqueros, and Simmler Formations. Some grains of biotite and muscovite are highly deformed These grains are present in rocks which are condensed and have little to no calcite cement.

Calcite cement is mainly of the granular sparite type or luster mottled type and can be seen replacing grains of 80

Tl\BLE 4. PERC!Nr CDil'CISmCII AHl TEX'roRE OP THIRTEEN RJCit SNil'l.m FlU! THE tJM)IPF!RI!Nl'IA1'!D II!JIID OP THE BRAID! CAmal SNil6'I'QIE

fii.IJ5'taiE ~ LOCALI'l'r--+ ~5 14 15 ~25 30 37 l3 16 24 32 40 GIIADIS: Qlilrts 33 34 40 38 42 28 22 34 3 20 9 4 Orthoc:l- 8 21 12 15 17 14 8 17 2 6 3 o.s Plac;Jioc~ 16 9 12 12 8 12 4 13 1 6 3 o.s Microcline 4 2 2 2 4 1 Granitic rode fragllll!lltll 11 8 8 10 8 10 13 13 6 2 Volcanic rode frag~M~~tll 2 4 4 5 4 4 1 4 Me~rpbic rock fra

~·calcite 15 10 32 10 5 80 82 95 Heatite 3 t 9 Limonite 7 5 4 2 4 Clay 5 5 t t 15 10 Olert 3 t Feldspar overqrowthll 2 t t Chlorite 1 ~·1 0 42 43 51 45 53 37 34 42 so so 53 80 80 F 51 51 41 46 42 50 46 53 50 47 47 20 20 R 7 6 8 9 5 13 20 5 3 2 G!!AIN SIZE: Range (Jill) 0.125- 0.125- 0.125- 0.25- 0.125- 1.125- 0.25- 0.25 0.004- 0.04 0.004- 0.004- 0.004- 1.0 2.0 5.0 1.0 1.0 1.0 2.0 1.0 0.125 0.5 1.0 0.16 0.62 Average (1111) 0.25 0.35 0.5 0.5 0.35 0.35 0.45 0.6 0.04 0.15 0.005 0.008 0.03

9:ll'l'DG' 3 m m p p-111 m m m m w p m m w IOJ'IIlm:i: 4 sa- sa- sa sa sa- sa- sa- sr sa- sa- sa- sr sr sr sr sr sr sr sr sr sr GDIEIW. S!JIWn': Percent qraina 81 85 82 85 83 86 64 85 6 40 17 5 Percent clay 1 79 59 Percent forsinifera 10 t Percent ~til 14 10 18 14 15 14 34 14 5 81 95 95 Percent por011ity 5 5 1 2 1 1 1 2

Footnotes: ll 0 + F + R • LOO foll<:ld Folk <19741 1 21 this equals crystal size for carconates1 Jl p-poor, IIP'InOderate, -111 4l -SI.Ibiln9Ular, er-IIUbrounded; 51 stained for orthoclue. Sydlols: t•trace, - -absent. Locali t~es shown on Fiqure 7. 81 feldspar and quartz. A gradual decrease in grain size in the rocks from coarse sand to clay does not occur, there fore the clay present in the rocks is probably cement and not detrital matrix. The weathering of feldspar grains supports this statement. Clay syntaxial cement rims were noticed on a few grains and probably accumulated during transport. A few grains of feldspar have feldspar over growths. The diagenetic alteration of the iron minerals in the rock forms limonite and hematite. The average mudstone is medium gray and arkosic (Fig.

28). The mudstone is similar in composition to the mud stone in the Rincon Shale. Sample 13 contains 79% clay, 10% foraminifera, 6% silt-size grains (quartz and feld spar), and 5% calcite cement, whereas sample 16, which is from a rip-up clast contains 59% clay, 40% sand and silt size grains, and 1% porosity (Table 4).

The pebble conglomerate is usually light gray and contains about 65% clasts and 35% sandstone matrix. The clasts consist mainly of well rounded pebbles of the light colored felsic rock type, and some dark-colored volcanics.

The sandstone matrix has the same composition as the aver age sandstone described above. The concretionary beds that are interbedded in the sandstone consist mainly of recrystallized micrite which forms either microsparite as defined by Folk <1974), or recrystallized dolostone. Sample 21 is a microspar i te, whereas sample 22 is a recrystallized dolostone. Sample 82

24, the only rock of its kind in the study area, is a mi crite and may represent an old tufa deposit. The exact origin of the rock is unknown. A burrow filled with medium grained arkosic sandstone was found in thin-section 32.

Contacts and Recognition

The undifferentiated member of the Branch Canyon Sand stone unconformably overlies undifferentiated Cretaceous rocks and the Simmler Formation (except in the northeast where the contact with the Simmler may be conformable), conformably overlies the Vaqueros Formation in the south west, conformably overlies and interfingers with the Rincon

Shale, and is conformably overlain by the Rincon Shale, the unnamed Miocene unit, and the undifferentiated Mon terey Shale (Figs. 5 and 6). The Branch Canyon is also in fault contact with the Eocene rocks to the east. The un conformable contact with the Cretaceous rocks (Fig. 27) is a buttress unconformity as descirbed in previous sections, whereas the unconformable contact with the Simmler is a disconformity as previously described. The lower contact with the Vaqueros and Rincon, and the upper contact with the Rincon have been described in the preceding sections.

The upper contact with the unnamed Miocene units is grada tional. Beds of the typical undifferentiated member of the Branch Canyon Sandstone crop out in the unnamed Miocene unit which consists of poorly resistant sandstone, mud stone, and yellowish-gray, parallel laminated limestone 83

that is usually stained a pale red. The contact is placed

just above the last major resistant light-gray sandstone

outcrop of the undifferentiated member of the Branch Can

yon Sandstone or at the first major appearance of the lime stone. The contact is usually marked by a break in slope

(Fig. 3). This break in slope can usually be easily seen

on the aerial photographs and was used to map the contact

in the east.

The overlying conformable contact with the Monterey

is easily recognized by differences in rock types between

the two formations, i.e., resistant sandstone of the Branch

to mudstone of the Monterey.

Fossils and Age

Almgren found a few foraminifera in mudstone samples

taken from the Branch Canyon in the adjoining area to the west at microfossil localities 42 and 44 (Plate 1 and

Appendix 1) • He states that the foraminifera indicate an age of probably early Miocene (early Saucesian to Saucesian) and a paleobathymetry of bathyal to lower bathyal depths.

No calcareous nannofossils or macrofossils were found in the unit. Vedder and others (1967) state that they found a few macrofossils from one locality in the Branch Canyon exposed approximately 1. 7 km (1 mi) east of South Fork

Campground (Plate 1) • The fossils they identified were

Vaquerosella andersoni (Twitchell), Miogryphus? cf. M. willetti (Hertlein and Grant), and Lyropecten sp. which 84

they stated indicate an age of early to middle Miocene

(now considered just early Miocene; Vedder, personal commun

ication) •

Origin

The average sandstone in the undifferentiated member

of the Branch Canyon Sandstone is similar in composition

to the sandstone in the Rincon Shale and the Vaqueros For mation. The granitic rock fragments are of the same com

position as older units and fresh grains of plagioclase

and microcline are still present. Therefore, the nearby

Cretaceous, Eocene, and, in part, Simmler rocks and nearby granitic outcrops were the source of sediment for the un differentiated member of the Branch Canyon Sandstone.

Conditions of moderate relief and semiarid to temperate

climate are believed to exist as they did for the Vaqueros and Rincon.

The two eastern most sandstone samples 25 and 30 have

lesser values of mineralogic maturity and more lithic ar kosic compositions than the average sandstone in the unit.

This indicates that as the sea rapidly transgressed over

the unconformable surface in these areas, the sediment was quickly buried and was not exposed to the maturing process

for a long period of time. Nearby Cretaceous and Eocene

rocks were the major source of sediment for the rocks in these areas and the granitic source was of lesser impor tance. 85

Grains in the average sandstone are subangular to subrounded and indicate a short to moderate distance of transport. Volcanic grains are well rounded because of recycling. No good paleocurrent indicators were measured in the field so there is no direct evidence of transport direc tion. Load casts which sag to the southwest (Fig. 21) and flame structures which bend to the west (Fig. 23) may give a weak indication of a west to southwest paleoslope direc tion and possible current direction. Microfossils in the western portion of this unit indi cate a marine environment of bathyal to lower bathyal water depths. Macrofossils identified by Vedder and others (1967) from this unit in the eastern part of the study area indicate a shallow-water marine environment, however, they could have been transported into deeper water. The medium- to very thick-bedded, medium-grained, generally structureless marine sandstone which forms the majority of this unit may be the product of highly erosive grain-flow mechanisms as descibed by Mutti and Ricci Lucchi (1978). These sandstone beds and many of the depositional sructures that are found in the undifferentiated member of the Branch Canyon Sandstone are indicative of facies A and B submarine-inner-fan and mid-fan channel deposits of Mutti and Ricci Lucchi (1978). These depositional structures include load casts (Fig. 21) and flame structures (Fig. 23) that form when overlying sediment sinks into an uncom- 86

pacted sediment layer of lesser density (viscoplastic de-

formation) (Mutti and Ricci Lucchi, 1978; Collinson and Thompson, 1982, p. 138). Convolute bedding (contorted

bedding) is formed by plastic deformation of partially

liquefied sediment soon after deposition and is evidence of rapid deposition (Collinson and Thompson, 1982, p. 145). Thick beds of sandstone that contain large mudstone rip-up clasts and have non-erosive bases and tops (Fig. 22) are the product of grain flows (Mutti and Ricci Lucchi, 1978; Reading, 1978, p. 387). Pebble channels that have scoured bases and may be filled with graded beds (Fig. 20) can result from grain flow or tractive action of upper flow regime conditions (Mutti and Ricci Lucchi, 1978).

Slump folds can develop in submarine channels due to the

slumping of channel walls. They can be associated with rapid sedimentation (Reineck and Singh, 1980, p. 90) such as is found in submarine channels. All of the above men tioned features and depositional processes that are found in the undifferentiated member of the Branch Canyon Sand stone are indicative of facies A and B submarine-inner-fan and mid-fan channel deposits (Mutti and Ricci Lucchi, 197 8) •

The deposits of the undifferentiated member of the

Branch Canyon Sandstone however do not totally fit into the submarine-fan model as described by Mutti and Ricci

Lucchi <197 8)

Canyon interfingers with the Rincon Shale which represents 87 the expected inter-channel and slope deposits, however these deposits do not represent those called for by the models of Mutti and Ricci Lucchi (1978) and Walker (1978).

Most notably missing are rocks which represent facies C of

Mutti and Ricci Lucchi (1978) model or the "classical tur bidites" of Walker's <1978) model. Therefore the Branch

Canyon characterized in the study area by thick-bedded, multi-story, channelized sandstone beds (Fig. 18) was prob ably deposited in a sand-rich submarine-fan environment which was infilling a California Borderland-type basin.

The environment of deposition for this unit shallows in an eastward direction. Figure 29 shows the eastern extent of the transgressing sea during the time in which the oldest rocks of the undifferentiated member of the

Branch Canyon Sandstone were deposited.

Small-scale, low-angle, tabular cross beds and ripple cross beds that were found in a small outcrop east of the

Sisquoc River and in the core of the Hurricane Deck syn cline probably were the result of deposition from migrat ing small-current and wave ripples in a sand rich shore face environment. The low-angle, wedge-shaped, cross beds and high-angle cross beds, along with some small scale beds containing rip-up clasts and graded beds found in the bed overlying the Cretaceous rocks in Figure 27, probably also were deposited by wave processes in a shoreface envi ronment similar to that described by Reading <1978, p.

149). The poor mineralogic maturity and higher than aver- N MN

c,.e, 4tce oil• I Middle Tertiary I ..._ -.. - ____.J I I I I -,~ ~ eo~· I \ '"... u y \ ;;...... _ CJ.e'& I I 0 6000 FT /, .--- 0 1500-M

_l,- ZERO ISOPACH APPROXIMATELY LOCATED ARROWS INDICATE DIRECTION OF THICKER DEPOSITS

Figure 29. Zero isopach of the stratigraphically oldest deposit of the undifferentiated member of the Branch Canyon Sandstone. Shows extent of eastward transgression for this time period.

(X) (X) 89

age rock fragment composition of sample 25 from this area may support the interpretation that these rocks were quickly deposited in a shoreface environment during the eastward transgression of the sea over the erosional unconformity surface. Channel-fill cross bedding also seen in the east probably was produced by the infilling of channels. The undifferentiated member of the Branch Canyon Sandstone in the eastern part of the mapped area probably was deposited in a shallower water environment, possibly of the shoreface, rather than as submarine-fan channel deposits which cover the major part of the formation. Most all of the rocks from this area are cemented with luster mottled calcite and are free of clay matrix, which represents slower periods of cementation, and winnowing currents, rather than the faster rates of cementation and sedimentation as indicated by the predominantly clay cemented rocks found to the east. After deposition, the rocks were compacted and ce mented.

UNNAMED MIOCENE UNIT Nomenclature This unit contains poorly resistant medium-grained sandstone, fossiliferous limestone containing foraminif era of Relizian age and minor amounts of diatoms, and light colored mudstone. It is not lithologically similar to any presently named Miocene unit known to the author. The unit is similar in age and stratigraphic position to 90 the Point Sal Formation of Canfield (1939), but differs in lithology. Canfield temporarily proposed the name for the siltstone and shell zone of the lower part of the Monterey Shale exposed approximately 0. 8 km ( 0. 5 mi) east of old Point Sal Landing on Point Sal Grande, Santa Maria dis trict. Woodring and Bramlette (1950) redesignated the type locality of the Point Sal Formation as the south slope of Mount Lospe, Santa Maria district. Literature restricts usage of the name Point Sal Formation to the Santa Maria Basin. The unit described below is also similar in age and stratigraphic position to the Monterey Shale of Blake (1855), but again they are different in lithology. Dibblee (1950) included the Relizian Point Sal Formation in what he mapped as Monterey Shale, which included all rocks above the Rincon Shale and below the Sisquoc Formation. Many who have worked on the Monterey, including Woodring and Bramlett (1950), Dibblee (1966), Isaacs (1981), and

Pisciotto (1981), seem to agree that the lower Monterey Shale (Saucesian to Luisian) is calcareous and contains a prolific assemblage of formanifera, whereas the upper Mon terey Shale (Mohnian) is siliceous and contains numerous diatoms. Because this unit contains more sandstone than has been reported to exist in the Point Sal Formation or the Monterey Shale, it seems best to refer to this unit as the unnamed Miocene unit. 91

Distribution and Thickness

The unnamed Miocene unit crops out in the core of the

Hurricane Deck syncline in the west-central portion of the

mapped a rea (Plate 1) • This outcrop is rectangular in shape and is about 1,830 m (6,000 ft) long and 762 m (2,500

ft) wide. This deposit is laterally continuous into the

adjoining area to the west (Plate 2). The unnamed Miocene

unit ranges in thickness from 69 m (225 ft) to 175 m (575 ft) •

Lithology

The unnamed Miocene unit consists of about 35% sand

stone, 35% limestone, and 30% mudstone. These percentages

are only estimates because the unit is poorly resistant

and is covered by dense vegetation (Fig. 3). Sandstone,

which is interbedded throughout the unit with limestone

and mudstone, appears to be more abundant near the base

of the formation.

The brush-covered outcrops of sandstone are poorly to

moderately indurated and poorly resistant except for some resistant Branch Canyon-type sandstone ridges exposed near

the lower gradational contact with the undifferentiated

member of the Branch Canyon Sandstone. The limestone is moderately well-indurated and is exposed on brush-covered

slopes. Outcrops of mudstone are rare because areas con

sisting chiefly of mudstone support the thickest growths 92 of vegetation in the unit. The unit contains some secon dary fractures which are filled with calcite in places.

The color of the sandstone on a fresh surface ranges from yellowish gray (5 Y 7/2) to pale yellowish brown (10 YR 6/2) to light gray (N 7) with some pale red (10 R 6/2) and on a weathered surface shows the same color varia tions, except for some additional moderate yellowish brown (10 YR 5/4). Color of the limestone on a fresh surface ranges from light gray (N 7) to yellowish gray (5 Y 8/1) to grayish orange (10 YR 7/4) and to pale yellowish brown (10 YR 6/2) and on weathered surfaces ranges from yellow ish gray (SY 7/2) to grayish orange (10 YR 7/4) to pale yellowish brown (10 YR 6/2) with some pale red (10 R 6/2).

The color of the mudstone is generally the same as that for the limestone. The sandstone is thin (1 to 10 em) to thick (30 to

100 em) horizontally bedded, lens forming, and contains the following sedimentary structures and features: (1) a few pebble-filled channels with scoured bases, (2) paral lel laminations, (3) some small wedge-shaped cross bedding, ( 4) some 20- to 30-cm-thick sandstone beds con taining rip-up clasts, ( 5) possible bioturbation, and ( 6) a few small-scale slump folds. The limestone is parallel laminated and may be thin parallel bedded. Of the few outcrops of mudstone seen, some contained parallel lamina tions. 93

43 <\

~-···:·:·

...... · . ,. . . . ' ...... 'l- ... .. \· . . . 0 .•. . . . • • t:l'.. .. : • F ..... :...... t . 3:1 1:1 1:3 RATIO FIR

Figure 30. Ternary diagram showing sandstone and limestone composition in the unnamed Miocene unit. Class ification scheme is from Folk (1974). Localities shown on Figure 7. <•=sandstone, A =limestone).

The average sandstone is a medium-grained, submature arkose (Fig. 30) which has an average composition of about

30% quartz, 24% feldspar, 13% granitic rock fragments, 5% volcanic rock fragments, 2% metamorphic rock fragments,

25% cement (mainly calcite and hematite), and 1% porosity

(Table 5). The grains in the average sandstone are subangular to subrounded and moderately sorted with the excep- tion of sample 17, which is well sorted. The average sandstone is mineralogically submature with a ratio of 0.7. 94

TJ\BLE 5. PERCEm' CCMroSmON AN:> TEX'ruRE OF EIGHT R()(l{ SAMPLES FlO! THE UNNAMED MIOCENE UNIT

~ LIMES'lt;llES 8 9 10 17 7 5 43 44 GRAINS: Q.lartz - 30 31 30 31 5 4 6 Orthoclase 13 14 12 12 2 1 2 Plagioclase ll 10 10 12 2 1 Microcline t t t Granitic rock fr~ts 13 10 ll 15 1 1 Volcanic rock fr~ts 5 5 5 5 Metamorphic rock fragments 3 3 2 Sedimentary rock fragments t Olert t Biotite t t t t !l.lscovite t t t 2 t Apatite t t Leucoxene t

MATRIX: Detrital clay 15 Micrite 25 40

FOSSI!.S: Mollusk fragments 4 Foraminifera 5 20 35 DiatCIIIS 5 l

CEMDll'S: Calcite 10 15 5 13 85 25 5 80 Hematite 14 10 24 t t t Limonite 7 5 15 Phosphate 5 4 Olert t t t Q=F-R: 1 Q 40 43 43 41 50 85 60 F 49 47 47 52 50 15 40 R ll 10 10 7 2 GRAIN SIZ~: .125- 0.25- 0.25- 0.125- 0.004- 0.004- 0.016- 0.004- Range

SC>RTIN:;: 3 m m m m-w m-w m-w

ROONJIN:i: 4 sa-sr sa-sr sa-sr sa-sr sa sr sa-·~ .. GmmAL stMVIRY: Percent grains 75 73 70 77 10 5 10 Percent matrix 40 40 Percent fossils 5 25 40 Percent cement 24 25 29 20 85 30 10 99 Percent porosity l 2 l 3 l

Footnotes: ll Q + F + R ,. l 0 follows Folk (1974 ; 2 this equals crystal size for carbonates; 3 m=m:xler- ate, W"Well; 4) sa"subangular, sr=subrounded. Symbols: t=trace, - ~ent. Localities shown on Figure 7. 95

Quartz grains found in the rocks range in types from single grains with single extinction to composite grains with undulose extinction. Some fresh unweathered grains of plagioclase and microcline are present. Granitic rock fragmenst are of the light-colored felsic-type like those found in the underlying formations. Volcanic rock fragments are weathered and well rounded.

Calcite cement found in all samples is of the granu lar sparite type and is very finely to finely crystalline.

Hematite cement is found in all samples except for sample

17, which contains limonite cement instead.

Using Folk's (1974) classification of limestones, thin-section samples 5 and 43 can be classified as foram iniferal biomicrites (Figs. 31-34), and samples 7 and 44 are recrystallized micrites (microsparite). The average biomicrite composition is about 40% matrix (mainly micrite with minor amounts of detrital clay), 33% fossils (mainly foraminifera, but may contain diatoms and macrofossil frag ments), 20% cement (mainly calcite with minor amounts of hematite, limonite, and phosphate), and 7% grains

7% grains (mainly of quartz and feldspar), and 3% foram inifera

The microspar i tes probably contained a greater per centage of foraminifera before recrystallization took place. Foraminifera tests are filled mainly with sparite 96

Figure 31. Photomicrograph of thin section sample 43 (foraminiferal biomicrite), from the unnamed Miocene unit, showing foraminifera which are up to 1 mm in length. Note phosphate-filled foraminifera. Base of photograph is 3.45 mm long.

Figure 32. Same photomicrograph as in Figure 31 ex ~ept with crossed-nicols. 97

Figure 33. Photomicrograph of thin section sample 5 (foraminiferal biomicrite), from the unnamed Miocene unit, showing diatoms and foraminifera tests. Base of photo graph is 4.3 mm long.

Figure 34. Photomicrograph of thin section sample 43 (foraminiferal biomicrite), from the unnamed Miocene unit, showing a pelecypod fragment filled with drusy mosaic cal cite cement. Base of photograph is 2.15 mm long. 98

but may be filled with micrite, chert, or phosphate (Figs. 31 and 32). Diatom tests are filled with calcite and pos sibly some dolomite (Fig. 33). Calcite cement is mainly very fine- to finely-crystal line sparite. Some bivalve and gastropod fossil fragments in sample 43 are filled with drusy mosaic calcite cement (Fig. 34). Foraminifera range in size from 0.06 rom to 1.0 rom (Figs. 31 and 32). Broken and complete bivalve and gastropod fragments range in size from 4 to 8 rom. The average size of the diatoms is 0.16 rom. No samples of mudstone were taken and therefore, no mudstone samples were studied in thin-section. The age and the color of the mudstone in this unit is more like that of the mudstone in the overlying undifferentiated Monterey Shale which does not contain pyrite than that of the mudstone in the underlying undifferentiated member of the Branch Canyon Sandstone or Rincon Shale, which contains contains pyrite. Therefore, it is assumed that the mudstone in this unit is similar to the mudstone described in the next section on the undifferentiated Monterey Shale.

Contacts and Recognition The unnamed Miocene unit conformably overlies the undifferentiated member of the Branch Canyon Sandstone and conformably under lies the undifferentiated Monterey Shale (Figs. 5 and 6). The lower gradational contact with the undifferentiated member of the Branch Canyon Sand- 99

Figure 35. Sharp conformable contact between unnamed Miocene unit and overlying undifferentiated Monterey Shale. Contact is right above grip on hammer. Hammer shown for scale is about 30 em (1 ft) long.

stone was described in the previous section. The upper conformable contact with the undifferentiated Monterey Shale is sharp (Fig. 35). It is recognized by the differences in lithology from interbedded sandstone, limestone, and poorly exposed mudstone of the unnamed Miocene unit to the interbedded parallel laminated mudstone and minor thin-bedded sandstone and secondary gypsum of the undifferentiated Monterey Shale. 100

Fossils and Age

The unnamed Miocene unit has an abundant diverse cal careous benthic foraminiferal assemblage with a few scat tered planktic foraminifera (Figs. 31 and 32) and some diatoms (Appendix 2). Thin-section sample 5 (Fig. 7) con tained abundant diatoms(?) in some rare laminations (Fig.

33). Common benthic foraminifera identified by Almgren

include: Siphogenerina branneri, Baggina robusta, and prob ably Vavulineria aff. v. californica var. appressa (Appen dix 2). He states that these foraminifera indicate an age of middle Miocene (Relizian), probably Siphogenerina branneri Zone and bathyal depths. Arnal and Vedder (1976, p. 3) state that Baggina robusta indicates an upper bath yal facies (180 to 500 m). Macrofossils found in this unit at c.s.u.N. fossil locality 684 include the mud pecten Delectopecten peckhami

(Gabb), unidentified species of gastropod, and plant frag ments. Vedder and others (1967) state that they found mud pectens to the west of the study area in the same zone as foraminifera which indicated a middle Miocene age. The mud-pecten shells range in size from 0. 5 to 2 em. They are abundant, mostly articulated specimens, and well preserved.

Origin

The decrease in amount of sandstone and increase in the finer grained deposits of limestone and mudstone in 101 the unnamed Miocene unit when compared to the underlying undifferentiated member of the Branch Canyon Sandstone, may indicate 1) a change in the source, 2) a change in relief of the source, or 3) a change in the current energy at the site of deposition. The composition of the average sandstone in the unnamed Miocene unit is similar to the composition of the average sandstone in the undifferen tiated member of the Branch Canyon Sandstone. Fresh grains of plagioclase and microcline are present in the unnamed

Miocene unit as they were in the underlying unit. There fore, it is likely that there was no major change in the source of sediment. In addition, mineralogy of the rocks does not suggest any climatic changes occurred in the source area. The presence of diatoms may indicate a period of cooling or upwelling of nutrients as was the case for the Monterey Shale (Ingle, 1981). However, cal careous foraminifera are predominant and suggest no cli matic change occurred.

A slight decrease in the mineralogic maturity from

1.0 for sandstones in the Branch Canyon to 0.7 for sand stones in the unnamed Miocene unit probably indicates that deposition occurred quickly and that possibly the distance of transport was shorter. A slight decrease in relief of the source area due to from erosion is possible and partial ly could be responsible for the finer grained deposits in the unnamed Miocene unit. 102

A change in current energy, at the site of deposition may be due to restricted circulation in a newly developing silled basin or to a deepening of the basin. Continued subsidence during the Miocene produced continued transgres sion which resulted in eustatic drowning of the coast and the formation of silled basins starved of clastics (Ingle, 1981) • These silled basins were the sites of deposition for the Monterey Shale (Ingle, 1981). The presence of clastics in the unnamed Miocene unit proves that a complete ly silled basin had not formed and therefore circulation was not totally restricted. Foraminifera in this unit indicate a deep water marine environment of bathyal depths and possibly more precisely upper bathyal depths. Foraminifera in the Rincon Shale and undifferentiated member of the Branch Canyon Sandstone indicate bathyal to lower bathyal depths. Hence, the basin did not become deeper but either remained the same depth or became shallower. A high rate of sedimentation and a relatively lower rate of basin subsidence during deposi tion of the Branch Canyon could have caused a shallowing of the basin. In the adjoining area to the west (Plate 2) the un named Miocene unit laterally undergoes a facies change to become the coarser grained undifferentiated member of the Branch Canyon Sandstone. This fact probably suggests that the main reason for decrease in grain size was probably due to a lateral channel migration to the west which would 103

effectively reduce the current energy at the site of depo

sition.

No paleocurrent indicators were measured in the unit,

therefore no direct evidence of transport direction was

obtained.

The living assemblage of mud pectens found at C.S.U.N.

fossil locality 684 indicates little to zero distance of

transport. The limestone and mudstone which contain the

mud pectens probably represent hemipelagic deposits. Rei neck and Singh (1980, p. 486) state that hemipelagic sedi

ments are a combination of terrigenous sediments, brought

in by slight current activity, and pelagic "rain 11 sedi

ments. This slight current activity or pulsations in the

cur rent activity may have produced the parallel lamina

tions found in the limestone

stone deposits. Low-density turbidity currents could have

also produced the parallel laminated limestones and mud stones (Reading, 1978, p. 385). Reading C1978) states

that such low-density cur rents can be initiated on the

edge of the shelf by storm waves.

The thin- to thick-bedded sandstone found in this

unit is similar to the submarine-fan channel deposits

found in the underlying undifferentiated member of the

Branch Canyon Sandstone. The sandstone in both units prob

ably was deposited by grain flow processes similar to those described by Mutti and Ricci Lucchi (1978). The

pebble-filled channels with scoured bases and beds con- 104 taining rip-up clasts also can be the product of grain flow or tractive action of upper-flow regime conditions

(Mutti and Ricci Lucchi, 1978). The small scale wedge shaped cross bedding in the sandstone can result from the migration of ripples formed by traction currents (Reineck and Singh, 1980).

The lateral facies association between the unnamed

Miocene unit and the undifferentiated member of the Branch

Canyon Sandstone means that these two units were in part simultaneously deposited. The unnamed Miocene unit is in part younger and therefore also was deposited after deposition of the Branch Canyon. The main submarine channels that were simultaneously depositing the sand-size sediment of the undifferentiated member of the Branch Canyon Sand stone laterally migrated westward allowing for the deposi tion of the unnamed Miocene unit. This unit was deposited on the eastern fringe of the submarine fan that was infil ing the California borderland-type basin. The sandstone beds represent channel deposits whereas the limestone and mudstone represent basin-fill deposits and possibly some interchannel deposits. The upward decrease in grain size from sand to clay probably represents the gradual termina tion of submarine channel deposition.

After deposition the sediment was compacted, cemented, and then recrystallized. The exact time of recrystalliza tion of micrite into microsparite is unclear. The foramini fera tests might have been filled with micrite shortly 105 after deposition, but definitely were filled before re crystallization of the micrite began.

UNDIFFERENTIATED MONTEREY SHALE

Nomenclature Blake (1856) first used the name Monterey Formation for light-colored, mostly white, argillaceous and arena ceous material exposed about 2 mi southeast from the center of the town of Monterey, Monterey County, California. From 1913 to 1935 the u.s. Geological Survey included the Vaqueros Sandstone in the Monterey Group. After 193 5, they discontinued the useage of the name Monterey Group and the name Monterey Shale was adopted for a lithologic unit of variable Miocene age, consisting predominantly of hard silic-cemented shales and soft shales carrying sili ceous microfossils (Wilmarth, 1938). Bramlette (1946) stated that all Miocene units consisting predominantly of siliceous shales were similar and should all be called the

Monterey Formation. He also stated that the type locality was unsatisfactory because a complete unbroken sequence could not be measured; however, he failed to correct the problem. Many who have worked on the Monterey, including

Woodring and Bramlette (1950), Dibblee (1966), Isaacs

(1981), and Pisciotto (1981) seem to agree in that the lower Monterey Shale (Saucesian to Luisian) is calcareous and contains a pr ol if ic assemblage of foraminifer a, whereas 106 the upper Monterey Shale (Mohnian) is siliceous and contains numerous diatoms.

The Monterey Shale can not be traced from the type section into the mapped area, but on the basis of similar lithology, and relative age, the unit consisting of predomi nantly light colored mudstone of middle Miocene (Relizian-

Luisian) age described below, is herein designated the undifferentiated Monterey Shale. More specifically the rocks { are believed to belong to the lower calcareous Monterey

Shale. Fritsche (1969) mapped exposures of the (undifferentiated) Monterey Shale in the Sierra Madre area about 5 km

(3 mi) to the northeast of the study area. These rocks can be correlated across the Nacimiento fault and into the study area (Yaldezian and others, 1983). Van Wagoner

(1981) correlated outcrops of mudstone exposed about 22 km

(13 mi> to the west of the study area, in the Zaca Lake quadrangle, Santa Barbara County, to the Monterey Shale.

These rocks can be traced into the study area using the reconnaissance map by Vedder and others (1967).

Distribution and Thickness

Four small exposures of undifferentiated Monterey

Shale are exposed in the core of the Hurricane Deck syncline (Plate 1). They are all exposed along ridge tops

(Figs. 3 and 14). The most extensive of these deposits occurs in the east along the Nacimiento fault. There is a 107 facies change between the two easternmost deposits of Rin con Shale and the two easternmost deposits of undifferen tiated Monterey Shale (Fig. 6). The preserved thickness of the Monterey in the study area is 31m (100ft). The upper portion has been removed by erosion.

Lithology

The westernmost exposure of the undifferentiated Mon terey Shale (Plate 1) consists of about 70 to 80% mudstone

20 to 35% fine- to medium-grained, interbedded sandstone, and 5% siltstone. The rocks from the central and two east ern exposures (Plate 1) were not looked at in detail and therefore, their exact composition is unknown. The rocks in these exposures are predominantly light-colored (yellow brown> mudstones. _The undifferentiated Monterey Shale is finer-grained to the west. Only two thin-section samples were studied from this unit and both are from the adjoining area to the west (Plate 2 and Fig. 7) where the unit con sists of about 70 to 80% clay-shale, 10 to 20% siltstone,

5% very fine- to fine-grained sandstone, and 5% limestone.

The rocks in this unit are moderately indurated and form poorly resistant usually brush covered slopes (Figs.

3 and 14) • Secondary gypsum is found along bedding planes and fractures.

The color of the mudstone on a fresh surface is main ly yellow brown (10 YR 7/2) but may be light gray

7/4). Siltstone is usually yellow brown (10 YR 7/2) to yellowish gray (5 Y 7/2) on both fresh and weathered sur faces. Color of the sandstone on a fresh surface is moder ate yellowish brown (10 YR 5/4) and weathers to dark yellow ish orange (10 YR 6/6). Limestone is the same color as the mudstone, mainly yellow brown (10 YR 7/2).

The sandstone and siltstone, when present, are inter bedded with mudstone. Both the mudstone and the sandstone are horizontally thin-bedded (5 to 10 em thick). The mud stone is parallel laminated (Fig. 31) and contains thin lenses of siltstone. Differences in grain size define the laminations. The siltstone and limestone also are parallel laminated.

Sample 41, a clay-shale from the adjoining area to the west, is representative of the composition of the mudstone found in the study area. The average mudstone is arkosic in composition and consists of about 60% matrix (detrital clay and micrite), 20% grains (mainly quartz and feldspar types), 10% fossils (mainly foraminifera with minor amounts of fish bones and scales, sponge spicules, and diatoms?),

10% cement (calcite, hematite, and limonite types), and possible traces of sapropel (Table 6). The amount of sand size detrital grains vary as it increases in siltstone and decreases in clay-shale. The amounts and kinds of cements and fossils also varies. The exact percent of diatoms is 109

TABLE 6. PERCENT (X)MFOSITION AND TEXTURE OF 'lWO ROCK SAMPLES FROM THE UNDIFFERENTIATED MONTEREY SHALE

CLAY-SHALE MICROSPARITE lOCALITY 41 45 GRAINS: Quartz 12 3 Orthoclase 6 1 Plagioclase 2 1 Biotite t Leucoxene t

MATRIX: Detrital Clay 40 16 Micrite 20 t

FORAMINIFERA: 10

CEMENTS: Calcite 5 72 Hematite 3 Limonite 7 Chert 2 1 Q:F-R: Q 60 60 F 40 40 R 2 GRAIN SIZE: 0.004- 0.004- Range (rnm) 0.125 0.016 Average (rnm) 0.03 0.01 3 SORTU"G: m w ROUNDI~: 4 sr sa-sr

GENERAL SUMMARY: Percent grains 20 5 Percent matrix 60 16 Percent foraminifera 10 Percent cements 10 79 Percent porosity Footnotes: 1) Q + F + R = 100 follows Folk (1974); 2) equals crystal size for sample 45; 3) m=moderate, w=well; 4) sa=subangular, sr=subrounded. Symbols: t=trace, -=absent. Localities shown on Figure 7. 110 unknown but they are less abundant than the foraminifera. The siltstone is believed to have the same general composi tion as the mudstone except for a slight increase in the amount of detrital grains. No samples of sandstone were studied in thin-section and therefore, their. true composition is unknown. However, since the sandstone in all of the underlying mid-Tertiary units previously described in this report have similar composition, it is logical to assume that the sandstone in this unit although finer-grained also is similar in composi tion. Therefore, the average sandstone is a fine- to medium grained, calcitic, submature arkose and contains grains that are subangular to subrounded. Sample 45 a microsparite (recrystallized micrite) is representative of all the limestone in the unit. The sample contains 72% calcite cement (mainly recrystallized micrite) 16% clay, 7% limonite cement, 5% detrital grains of quartz and feldspar, and possible traces of sapropel (Table 6). The calcite cement is very finely to finely crystalline.

Contacts and Recognition The undifferentiated Monterey Shale conformably over lies the unnamed Miocene unit in the west and the undiffer entiated member of the Branch Canyon Sandstone in the cen tral and eastern portions of t~e mapped area (Plate 1 and Figs. 5 and 6). The upper portion of the Monterey is not present in the study area. In the east the Monterey is in 111 fault contact with Eocene Rocks. The lower sharp conform able contacts with the unnamed Miocene unit (Figs. 3 and

35) and the undifferentiated member of the Branch Canyon

Sandstone (Fig. 14) are recognized due to the change in rock types as described in the preceding sections.

Fossils and Age

The undifferentiated Monterey Shale contains no macro fossils other than fish bones and scales. Microfossils present in this unit and identified by Almgren include foraminifera and sponge spicules (Appendix 1). Micro fossil locality 8 yielded only rare foraminifera which indicate an age of probably Miocene.

The outcrop of undifferentiated Monterey Shale which overlies the unnamed Miocene unit (Plate 1) is the young est stratigraphic unit in the study area. The central exposure of the Monterey (Plate 1) may stratigraphically correlate in age to the unnamed Miocene unit. A facies change between the two eastern exposures of the Monterey and the Rincon suggest they are similar in age. There- fore, the undifferentiated Monterey Shale may become older toward the east. Further support for this interpretation is the early Relizian age indicated by foraminifera from microfossil localities 23 and 24. These localities are both from exposures of Montetey Shale that crop out about

0.6 km (1 mi) southeast of the undifferentiated Monterey

Shale exposed along the trace of the Nacimiento fault. 112

Foraminifera from locality 38, which is in the adjoining area to the west (Plate 2) , strongly indicate an age of middle Miocene (Relizian-Luisian). Still further west, approximately 16 km (10 mi), in Tunnell Canyon, Horse Can yon, Burro Canyon, and in the Bald Mountain area Relizian and Luisian foraminifera assemblages are present (Vedder, personal communication). No strata containing Mohnian foraminifera were found in that area. Filewicz states that calcareous nanofossils from locality 38 indicate the

Sphenolithus heteromorphus Zone of middle Miocene age

(Appendix l) •

Origin The origin of the undifferentiated Monterey Shale is essentially the same as it is for the unnamed Miocene unit. The sandstone composition is believed to be similar and therefore the source of the sand-size sediment is the same. No mineralogic evidence exists to suggest that the climate had changed. Microfossils indicate a marine en vironment of bathyal depths.

The decrease in amount of sandstone in this unit compared to the unnamed Miocene unit indicates that the ability of the source to supply sand-size sediment was reduced. This is partially explainable by the assumption that erosional processes further reduced the relief of the source area and therefore reduced its ability to supply sand-size sediment. Also the continued relative subsi- 113 dence and transgression during the middle Miocene as des cribed by Ingle (1981) produced silled basins and the con tinued trapping of the clastic sediment along the eustati cally drowned coastal areas. The sandstone in the undif ferentiated Monterey Shale suggests that the basin was not totally restricted (silled) to clastic influx. This con tinued relative subsidence and trangression also reduced the actual areal extent of the source area and may have reduced its ability to provide clastic sediment. Areas that were once sources of clastic sediment were turned into sites of deposition.

No paleocurrent indicators were measured in this unit so there is no direct evidence of transport direc tion.

The rocks in the undifferentiated Monterey Shale represent basin-fill deposits. Submarine-fan channel ac- ti vi ty which was responsible for the deposition of the undifferentiated member of the Branch Canyon Sandstone and the basal part of the unnamed Miocene unit ceased before the deposition of the undifferentiated Monterey

Shale. The dormant fan was then covered by basin-plain deposits of the undifferentiated Monterey Shale. The

Monterey Shale has been previously described as repre senting basin-fill deposits by several authors (Dibblee,

1966) ; Ingle, 1981; Woodbridge and Bramlete, 1950; and

Isaacs, 1981). 114

After deposition, the unit was compacted and ce mented. Authigenic gypsum then formed between the bedding planes and in the secondary fractures.

QUATERNARY DEPOSITS

Quaternary deposits in the study area include stream terraces, landslides, and alluvium. Most of the alluvium and stream-terrace deposits occur along the Sisquoc River (Fig. 3). Some occur along South Fork of the Sisquoc River and White Ledge Creek (Plate 1). A single stream terrace is exposed just north of the Sweetwater Trail in the north east and another is exposed in the south along a tributary to White Ledge Creek. Landslide deposits occur along the north side of the Sisquoc River and in the northeast along the Nacimiento fault. Some spring-tufa deposits occur throughout the study area, but were not extensive enough to be mapped. These tufa deposits usually formed in areas where downward groundwater movement was impeded by an im permeable mudstone layer. All of these Quaternary deposits unconformably overlie older units. The thickness of the Quaternary deposits is estimated to be on the average of only a few meters. Stream terraces are the thickest deposits and may be as thick as 10 m (33 ft). Some of the younger alluvium is only 1 m or less thick. 115

Three levels of stream terraces were mapped in the study area. These three levels represent three periods of uplift accompanied by a deepening of the stream channels

(stream rejuvenation). The terraces are remnants of pre vious cycles of floodplain deposition. The current cycle is responsible for the alluvium in the river and stream beds.

Dense vegetation covers all the terrace deposits.

Some of the alluvium is partially grass and brush covered, whereas the landslide deposits are recognized by hummocky topography and are covered mainly by wild grasses and some brush.

Color of the terrace and landslide deposits is moder ate reddish brown (10 R 4/6) to dark yellowish orange (10

YR 6/6). Color of the alluvium is light grayish yellow (5 y 9/4). Terrace and landslide deposits are darker in color than the alluvium because the iron minerals they contain have been exposed to oxidation longer.

All Quaternary deposits consist of clay- to boulder size particles. Alluvium is unconsolidated, whereas terrace and landslide deposits are unconsolidated to semi consolidated due to compaction. The alluvium and terrace deposits consist mainly of irregular-shaped lenses of con glomerate and sand and some minor sand and silt beds. The deposits are poorly sorted and have a bimodal character.

Cross bedding also is common in these deposits. 116

Conglomerate clasts range in size from pebble to boul der and are angular to well rounded. Composition of the clasts varies as the underlying rock types vary. Clasts consist mainly of well-rounded grani tics and angular to rounded Miocene sedimentary clasts of sandstone, some con glomerate, and mudstone. Minor amounts of volcanics, quart zite, gabbro, and older sedimentary rocks are also present. The Miocene sedimentary clasts are first-cycle clasts and have not undergone a great amount of transport. Most of the other clasts are recycled except for some fresh Cre taceous sedimentary clasts. The well rounded clasts repre sent long distances or time of transport which may be accom plished through recycling. The range in size of the clasts indicates that stream current velocity varied. Gower and others (1966) state that the stream ter races in the study area are of probable Pleistocene age. Dibblee (1966) states that the two stages of uplift during the Quaternary caused two cycles of erosion and deposi tion. The first cycle ended with the deposition of stream terraces and older alluvium and the second or present cylce is responsible for deposition of Holocene alluvium. Land slide deposits, which lay undisturbed upon the trace of the Nacimiento fault, probably were deposited during one of these two periods of Quaternary uplift. The alluvium deposits are Holocene in age and are still being depos ited. STRUCTURE

INTRODUCTION

The major structural features of the study area are the Hurricane Deck syncline and the Nacimiento fault (Fig. 36). The trough of the Hurricane Deck syncline is partial ly faulted to the east. Other structural features include the faults and numbered folds shown in Figure 36.

FOLDS

Hurricane Deck Syncline The large Hurricane Deck syncline runs from east to west across the study area (Fig. 36). The fold, in its entirety, between the Huasna fault to the west and the Nacimiento fault to the east, is approximately 48 km (30 mi) long (Fig. 4) • The fold plunges very slightly to the west, is stratigraphically asymmetrical, cylindrical, slightly inclined to the north, and open. The fold is stratigraphically asymmetrical because the Miocene units thicken to the south. Miocene rocks on the north limb dip between 30° and 50°, whereas on the south limb they dip between 15° and 30° (Fig. 37). The syncline also folds Cretaceous rocks which on the average dip steeper than the Miocene rocks (Plate 1, cross-section B-B'). The reason for their steeper dip is that they have been ex posed to more periods of deformation than the Miocene rocks. Cretaceous rocks on the north limb of the fold dip

117 N MN c,.e, iiceo (18

'· EXPLANATION -- 1 - Anticline f - Syncline

---Fault 6000 FT

1 r-- -, ------~ 0 1500 M Oligocene-Miocene Rocks

Figure 36. Index map showing locations of folds and faults in the study area.

...... co 120

Other Folds

All of the other folds are similar to the Hurricane

Deck syncline and trend west to northwest. Fold 1

north because of a steep north limb; i.e., about 35° for

the north limb and about 20° for the south limb. The

anticline is upright with both limbs dipping about 35°.

Folds 5 (syncline) and 6

small and fold only Miocene rocks (Plate 1, cross-section

c-c I> • They terminate at the unconformity between the Cretaceous and Miocene rocks. These folds are believed to

be symmetrical, cylindrical, upright or slightly inclined,

and open. Folds 7 (anticline) and 8

folds mapped in the study area north of the Hurricane Deck

syncline. These folds are truncated to the southeast by

the Nacimiento fault and terminate to the northwest at the

unconformity with the Cretaceous rocks. They do not fold

Cretaceous rocks. The folds are symmetrical, cylindrical,

slightly inclined, and gentle. The north limb of the syn

cline dips 5° near the fault and about 45° farther

north, whereas its southern limb dips about 30° near

the fault and about 20° to the north.

FAULTS

Nacimiento Fault

The Nacimiento fault trends N45°W through the study

area (Fig. 36) and separates Miocene and Cretaceous rocks

from Eocene rocks (Plate 1). Figure 4 shows the regional

extent of this fault, which can be traced on aerial photo graphs. Dibblee (1976) renamed the fault in this area the 122

Rinconada fault and other authors (Schwade, 1954; Hill and others, 1958; and Gower and others, 1966) have used the name Nacimiento for other faults. The reader is referred to Yaldezian and others (1983) for details on the nomencla ture of this fault.

Two different periods of movement have been suggested for the Nacimiento fault in this area by Gower and others (1966), Vedder and Brown (1968), and Yaldezian and others

(1983): one pre-Miocene and one post-Miocene. The juxta position of Eocene rocks on the northeast side against

Cretaceous rocks on the southwest along most of the trace of this fault in the San Rafael Wilderness suggests rela tive down dropping of the northeast side during the pre

Miocene. Yaldezian and others (1983) state that the post

Miocene movement on this fault ranges between pure north east-side-up dip slip of about 800 m (2,625 ft) and pure right slip of a maximum of 6 km (4 mi). The absence of

Miocene rocks juxtaposed along the northeast side of the fault indicates that the movement must have had some com ponent of dip slip and therefore was a combination of dip slip and strike slip. Gower and others (1966) state that this fault dips 70° to 80°N. If this is correct, then the post-Miocene Nacimiento fault may be a reverse fault.

The last movement on the Nacimiento fault in this area occurred after the Miocene rocks were folded and be fore the Pleistocene landslides covered the fault trace. 123

Other Faults

The other faults in the area trend northwest and are minor when compared to the Nacimiento. The fault which coincides with part of the trough of the Hurricane Deck syncline (Fig. 36) shows northeast-side-up separation due to the absence of Miocene units on the northeast side of the fault. The linear nature of the contact also indi cates the presence of a fault rather than a buttress un conformity contact.

The faults south of the Hurricane Deck syncline merge to the west and east to form a relatively down-dropped fault block (Fig. 36). A trace of the fault continues to the southeast through the Cretaceous and out of the study area. Evidence for the relative down dropping is that the

Rincon is juxtaposed against older rocks of the Creta ceous. Slickensides were found in the Cretaceous rocks about 90 m (300 ft) east of South Fork Campground. Cross section C-C' (Plate 1) shows that the southern fault has a south-side-up separation of about 92 m (300 ft) and that the northern fault has a north-side-up separation of about 396m (1,300 ft).

These faults are believed to have formed due to the same stresses which formed the folding in the area. This would result in the formation of high-angle reverse faults, which these faults are believed to be. Further evidence is needed to determine if these faults actually are reverse faults. 124

POST-MONTEREY SHALE STRUCTURAL HISTORY

Sometime after deposition of the undifferentiated

Monterey Shale, the area was subjected to northeast-to southwest compressional stress. This stress caused the rocks to yield to produce the west-trending Hurricane Deck syncline, folds 1 and 2, and possibly folds 3 and 4. Stress continued until the brittle-failure point of the rocks was exceeded and the rocks broke to produce the minor northwest trending faults. These minor faults truncate folds 2, 3, and 4, and therefore indicate that faulting occurred after the folds were generated. Minor folds 5 to 8 are believed to have formed after the generation of these minor faults for the following reasons: 1) they are not truncated by the minor faults, 2) they are not mapped in and do not fold the Cretaceous rocks, and 3) they are smaller in size than the other folds.

Two possible explanations for the origin of these minor folds which fold Miocene rocks and not Cretaceous rocks are discussed below. The first explanation starts with initial post-Miocene stress that resulted in folding of both Miocene and Cretaceous rocks as seen evidenced by the Hurricane Deck syncline, folds 1 and 2, and possibly folds 3 and 4. As stress continued, the more rigid Cre taceous rocks might have reached a point where slip along bedding planes occurred. Movement along these bedding plane faults could have resulted in the generation of the minor folds found in the less rigid Miocene rocks. The 125

Miocene rocks at the time of folding could have been in a semi-consolidated, semi-compacted state. To prove this theory correct one would have to find evidence indicating bedding plane slippage existed in the Cretaceous rocks.

The second explanation involves detachment faulting at the unconformity surface between the rigid Cretaceous rocks and the less rigid Miocene rocks. This detachment faulting may have resulted due to further stress after the initial post-Miocene stress. This continued stress would then be concentrated in the Miocene rocks and result in further folding of these rocks. To prove this theory cor rect, one would have to find evidence indicating detach ment faulting existed.

Evidence to prove that either bedding-plane faulting or detachment faulting took place was not easily recog nized in the field and may in fact be very difficult to find if it is even present. A good exposure of the unconformity surface (Fig. 27) showed it to be irregular and perhaps wavy. This may be weak evidence for bedding-plane slip of the Cretaceus rocks rather than detachment fault ing along the unconformity surface. Vedder (personal com munication) states that he favors detachment faulting be cause he thought he saw evidence for this about 17 km (10 mi) to the east of the study area, in the Fox Mountain quadrangle and possibly about 12 km (7 mi) to the west of the study area in the Bald Mountain area. A combination of the two explanations may also account for the addition- 126 al folds in the Miocene. Further study is needed to deter mine the origin of the minor folds.

After these folds developed, movement on the Nacimi ento fault occurred and truncated all folds. The post-Monterey compressional events in this region are thought to be related to right-lateral translational shear on the San Andreas fault

Compressional forces uplifted the San Rafael Moun tains starting in the lower Pliocene (Dibblee, 1966).

The mountains continued to grow in the Pleistocene as is indicated by the terrace levels and probably are continuing to rise in modern times. GEOMORPHOLOGY

The area has a late youthful topography except for the floodplain of the Sisquoc River, which has an early mature topography. The hillsides of the Sisquoc River are marked by three terrace levels in a stair-step fashion

(Fig. 3). The terraces have gently sloping surfaces which represent old undissected floodplains of the Sisquoc

River. The three levels present indicate that three successive stages of uplift occurred during the Pleisto cene.

A dendritic pattern of youthful streams drains the area. These streams empty directly into the Sisquoc River or into other creeks, such as White Ledge Creek, which drain into the Sisquoc River. The northwestward-flowing

Sisquoc River is the major river in the area and contains water the year round, whereas many of the smaller creeks and streams go dry in the bot summer months. The Sisquoc

River is to be a braided river up to the point where the South Fork joins it near South Fork Campground. From this point north, the Sisquoc represents a young meander ing river and has developed a floodplain characterized by old meander scars and partially stabilized (by vegetation) flood-stage bars. The Sisquoc flows diagonal to strike and both down and up dip.

The youthful streams have their headwaters in the surrounding mountains and, therefore, may form waterfalls

127 128 during periods of high runoff. The streams are actively down cutting and have formed V-shaped valleys with steep slopes. Many of the larger streams which empty into the Sisquoc flow somewhat parallel to the general east-west strike of the beds. By doing this they take advantage of less resistant strata. The smaller streams generally take the shortest route possible to the Sisquoc or to the tri butaries of the Sisquoc. SUMMARY OF GEOLOGIC HISTORY

Late Cretaceous - Deposition of middle-fan channel and interchannel deposits of the undifferentiated Cretaceous rocks by turbidity currents and grain flow.

Late Cretaceous to Oligocene - Uplift, folding, and ero sion, as indicated 1) by the lack of any lower Tertiary rocks and 2) the angular unconformity between the Cre taceous and middle Tertiary rocks. Rocks of Eocene age probably were deposited and mostly eroded away during this time.

Late Oligocene to Early Miocene - Continued erosion which is accompanied by the formation of alluvial fans and the deposition of stream-laid channel deposits of the Simmler

Formation. Also slight transgression in northeast suggest ed by shallow-water marine deposits of the Simmler in that area.

A short period of non-deposition and possible erosion suggested by the disconformity between the Simmler Forma tion and the overlying Miocene units occurred after deposi tion of the Simmler.

Late Miocene (Zemorrian to SaucesianL - Subsidence follow ed by eastward transgression of the sea and resumption of marine deposition. This is indicated by deposition of the

129 130 transgressive shallow-water marine sandstone of the Vaque ros, the submarine-fan channel deposits of the undifferen tiated member of the Branch Canyon Sandstone, and the interchannel and slope deposits of the Rincon Shale.

The zero isopachs of the stratigraphically oldest Rincon Shale (Fig. 17) and undifferentiated member of the

Branch Canyon Sandstone (Fig. 29) indicate the extent of eastward transgression during these times. Transgression continued and finally flooded the study area during deposi tion of the undifferentiated member of the Branch Canyon

Sandstone. Migration of the submarine channels is shown by the interfingering of the undifferentiated member of the

Branch Canyon Sandstone and the Rincon Shale.

Middle Miocene (Relizian to_Luisi_9.nL - Continued subsi dence and transgression with deposition of unnamed Miocene unit and undifferentiated Monterey Shale. The channel and interchannel deposits in the lower part of the unnamed

Miocene unit along with the westward facies change into the undifferentiated member of the Branch Canyon Sandstone suggest channel migration was to the west. The finer grained nature of the basin-fill deposits of the upper half of the unnamed Miocene unit and of the undifferen tiated Monterey Shale may suggest that: 1) the source area had been eroded to lower relief, 2) the source area had been further removed from the site of deposition, 3) the 131 possible generation of a partially restricted basin, or 4) a combination of all of the above.

Upper Miocene to Pleistocene - Uplift and deformation which result in folding and faulting of the Cretaceous, Oligocene, and Miocene rocks. Erosion follows or is simultaneous with deformation.

Pleistocene - Nonmarine deposition results in accumulation of stream terraces. Continued uplift results in formation of three terrace levels and landslides.

Holocene - Nonmarine deposition of alluvium and possible continuation of uplift. REFERENCES CITED

Arnal, R. E., and Vedder, J. G., 1976, Late Miocene paleo bathymetry gf the California continental borderland north of 32 , in Fritsche, A. E., TerBest, H., Jr., Warnardt, W. W.-,-eds., The Neogene symposium: Society of Economic Paleontologists and Mineralogists, Pacific Section, p. 1-12. Bates, R. L., and Jackson, J. A., 1980, Glossary of Geo logy: Falls Church, Virginia, American Geological Institute, 2nd ed., 751 p.

Blake, T. F., 1981, Depositional environments of the Simm ler Formation in southc-n Cuyama Valley, Santa Barbara and Ventura Counties, ~alifornia [M.S. thesis]: Cali fornia State University, Northridge, 151 p., 1 plate. Blake, w. P., 1855, Notice of remarkable strata containing the remains of Infusaria and Polythalmia in the Ter tiary formation of Monterey, California: Philadelphia, Proceedings of the Academy of Natural Sciences, v. 7, p. 328-331 [1856].

Bramlette, M. N., 1946, The Monterey Formation of Califor nia and the origin of its siliceous rocks: United States Geological Survey Professional Paper 212, 57 p. Canfield, c. R., 1939, Subsurface stratigraphy of Santa Maria Valley oil field and adjacent parts of Santa Maria Valley, California: American Association of Petroleum Geologists Bulletin, v. 23, no. 1, p. 45- 81.

Collinson, J. D., and Thompson, D. B., 1982, Sedimentary structures: London, George Allen and Unwin Ltd., 194 P· Dibblee, T. w., JR., 1950, Geology of southwestern Santa Barbara County, California: California Division of Mines and Geology Bulletin 150, 95 p.

1966, Geology of the central Santa Ynez Mountains, Santa Barbara County, California: California Division of Mines and Geology Bulletin 186, 99 p., 4 plates.

132 133

1973, Stratigraphy of the southern Coast Ranges near the San Andreas fault from Cholarne to Maricopa, Cali fornia: United States Geological Survey Professional Paper 764, 45 p. 1976, The Rinconanda and related faults in the south- ---ern Coast Ranges, California, and their tectonic signif- icance: United States Geological Survey Professional Paper 981, 55 p. Fairbanks, H. w., 1894, Geology of the northern Ventura, Santa Barbara, San Luis Obispo, Monterey, and San Benito Counties, California: California State Mining Bureau, Report 12, p. 493-526. Fischer, P. J., 1976, Late Neogene- Quaternary tectonics and depositional environments of the Santa Barbara Basin, California, ~n Fritsche, A. E., TerBest, Harry, Jr., and Wornardt, w. w., eds., The Neogene sympo sium: Society of Economic Paleontologists and Mineralo gists, Pacific Section, p. 33-52. Folk, R. L., 1974, Petrology of sedimentary rocks: Austin, Texas, Hemphill Publishing Company, 192 p. Fritsche, A. E., 1969, Miocene geology of the central Sierra Madre Mountains, Santa Barbara County, California [Ph.D. dissertation]: University of California, Los Angeles, 385 p., 24 plates. Goddard, E. N., chairman, 1970, Rock-color chart: Boulder, Colorado, Geological Society of America. Gorsline, D. s., and Emery, K. 0., 1959, Turbidity- current deposits in San Pedro and Santa Monica basins off southern California: Geological Society of America Bulletin, v. 70, p. 279-290. Gower, H. D., Vedder, J. G., Clifton, H. E., and Post, E. v., 1966, Mineral resources of the San Rafael primi tive area, California: United States Geological Survey Bulletin 1230-A, p. A1-A28, 2 plates. Hamlin, Horner, 1904, Water resources of the Salinas Valley: United States Geological Survey Water-Supply Paper 89, 91 p., 12 plates. Hill, M. L., Carlson, s. A., and Dibblee, T. w., Jr., 1958, Stratigraphy of Cuyama Valley-Caliente Range area, California: American Association of Petroleum Geolo gists Bulletin, v. 42, p. 2973-3000. 134

Howell, D. G., Vedder, J. G., McLean, Hugh, Joyce, J. M., Clark, Jr., and Smith, Greg, 1977, Review of Creta ceous geology, Salinian and Nacimiento blocks, Coast Ranges of Central California, j~ Howell, D. G., Vedder, J. G., and McDougall, K. , eds. , Cretaceous geology of the California Coast Ranges, west of the San Andreas fault: Society of Economic Paleontolo gists and Mineralogists, p. 1-46. Ingle, J. C., 1975, Paleoecologic indicators and trace fossils, in Dickinson, w. R., ed., Current concepts of depositional systems with applications for petro leum geology, short course: Bakersfield, California, San Joaquin Geological Society, p. 8-1 - 8-11. 1981, Cenozoic depositional history of the northern continental borderland of southern California and the origin of associated Miocene diatomites, in Isaacs, c. M., ed., Guide to the Monterey Formation in the California coastal area, Ventura to San Luis Obispo: American Association of Petroleum Geologists, v. 52, p. 1-8. Isaacs, c. M., 1981, Lithostratigraphy of the Monterey Formation, Goleta to Point Conception, Santa Barbara Coast, California, in Isaacs, C. M. , ed. , Guide to the Monterey Formation in the California coastal area, Ventura to San Luis Obispo: American Association of Petroleum Geologists, v. 52, p. 9-23. Kerr, P. F. , 1931, Bentonite from Ventura, California: Economic Geology, v. 26, no. 2, p. 153-168. Kew, w. s. w., 1924, Geology and oil resources of a part of Los Angeles and Ventura Counties, California: United States Geological Survey Bulletin 753, 202 p. Kleinpell, R. M., 1938, Miocene stratigraphy of California: Tulsa, Oklahoma, American Association of Petroleum Geologists, 450 p. McLean, H., Howell, D. G., and Vedder, J. G., 1977, An unusual Upper Cretaceous conglomerate in the Central San Rafael Mountains, Santa Barbara County, Califor nia, in Howell, D. G., Vedder, J. G., and McDougall, K., eds., Cretaceous geology of the California Coast Ranges, west of the San Andreas fault: Society of Economic Paleontologists and Mineralogists, p. 79- 83. 135

Middleton, G. v., 1970, Experimental studies related to problems of flysch sediment action, in Lajoie, J., ed., Flysch sedimentology in North America: Special Paper Geological Association of Canada, v.7, p. 253- 272.

Mutti, E., and Ricci Lucchi, F., 1978, Turbidites of the northern Apennines: introduction to facies analysis: International Geological Review, v. 20, no. 2, p. 125-166.

Page, B. M., 1966, Geology of the Coast Ranges of Califor nia, in Bailey, E. H., ed., Geology of northern Cali fornia: California Division of Mines and Geology Bulle tin 190, p. 255-276.

_____ 1977, Some Pliocene and Quaternary events in Califor nia, in Nilsen, T. H., Late Mesozoic and Cenozoic sedimentation and tectonics in California, short course: Bakersfield, California, San Joaquin Geologi cal Society, p. 86-98.

Pettijohn, F. J., 1975, Sedimentary rocks: New York, Harper and Row, 3rd ed., 628 p.

Pisciotto, K. A., 1981, Notes on Monterey rocks near Santa Maria, California, in Isaacs, C. M. , ed. , Guide to the Monterey Formation in the California coastal area, Ventura to San Luis Obispo: American Association of Petroleum Geologists, v. 52, p. 73-81.

Reading, H. G., 1978, Sedimentary environments and facies: Osney Mead, Oxford, England, Blackwell Scientific Publications, 557 p. Reid, s. A., 1979, Depositional environments of the Va queros Formation along upper Sespe Creek, Ventura County, California [M.S. thesis]: California State University, Northridge, 129 p., 2 plates.

Reineck, H. E., and Singh, I. B., 1980, Depositional sedi mentary environments: New York, Springer-Verlag, 2nd ed., 549 p.

Scholle, P. A., 1978, A color illustrated guide to carbo nate rock constituents, textures, cements, and porosi ties: American Association of Petroleum Geologists Memoir 27, 241 p. 136

1979, A color illustrated guide to constituents, textures, cements, and porosities of sandstones and associated rocks, American Association of Petroleum Geologists Memoir 28, 201 p. Schwade, I. T., 1954, Geology of Cuyama Valley and adja cent ranges, San Luis Obispo, Santa Barbara, Kern, and Ventura Counties, lrr Jahns, R. H., ed., Geology of southern California: California Division of Mines and Geology Bulletin 170, map sheet 1. Schwade, I. T., and Dibblee, T. w., Jr., 1952, Sespe Creek - Cuyama divide through Cuyama Valley to San Andreas fault, in American Association of Petroleum Geolo gists - Society of Economic Paleontologists and Miner alogists - Society of Exploration Geophysicists Guide book: Joint Annual meeting, Los Angeles, California, March, 1952, p. 84-88.

Shepard, F. P., and Dill, R. F., 1966, Submarine canyons and other sea valleys: Chicago, Rand McNally, 381 p. Tholman, c. F., 1927, Biogenesis of hydrocarbons by diatoms: Economic Geology, v. 22, no. 5, p. 459.

Thorup, R. R., 1943, Type locality of the Vaqueros Forma tion, in Geologic formations and economic development of the oil and gas fields of California: California Division of Mines and Geology Bulletin 118, p. 463- 466. Van Wagoner, s. L. , 1981, Geology of a part of the Zaca Lake Quadrangle, Santa Barbara County, California [M.S. thesis]: California State University, North- ridge, 143 p., 1 plate. Vedder, J. G., and Brown, R. D., Jr., 1968, Structural and stratigraphic relations along the Nacimiento fault in the southern Santa Lucia Range and San Rafael Moun tains, California, in Dickenson, w. R., and Grantz, A., eds., Proceedings of conference on geologic prob lems of San Andreas fault system: Stanford University Publications in the Geological Sciences, v. 11, p. 242-259. Vedder, J. G., Gower, H. D., Clifton, H. E., Durham, D. L., 1967, Reconnaissance geologic map of the central San Rafael Mountain and vicinity, Santa Barbara County, California: United States Geological Survey Miscel laneous Geologic Investigation map I-487, scale 1:48,000. 137

Vedder, J. G., Howell, D. G., and McLean, Hugh, 1977, Upper Cretaceous red beds in the Sierra Madre - San Rafael Mountains, California, in Howell, D. G. , Vedder, J. G., and McDougall, K., eds., Cretaceous geology of the California Coast Ranges, west of the San Andreas fault: Society of Economic Paleontologists and Mineralo gists, p. 71-78. Walker, R. G., 1978, Deep-water sandstone facies and ancient submarine fans: models for exploration for stratigra phic traps: American Association of Petroleum Geolo gists Bulletin, v. 62, p. 932-966. Wasson, R. J., 1977, Last-glacial alluvial fan sedimenta tion in the Lower Derwent Valley: Tasmania Sedimento logy 24, p. 781-799. Watts, w. L., 1897, Oil and gas yielding formations of Los Angeles, Ventura, and Santa Barbara Counties, Califor nia: California State Mining Bureau Bulletin, no. 11, 94 p. Wilmarth, M. G., 1938, Lexicon of geologic names of the United States: United States Geological Survey Bulle tin 896, part 2, M-Z, p. 1245-2396. Woodring, w. P., and Bramlette, M. N., 1950, Geology and paleontology of the Santa Maria District, California: United States Geological Survey Professional Paper 222, 185 p.

Yaldezian, J. G., Popelar, s. J., Fritsche, A. E., 1983, Movement on the Nacimiento fault in northern Santa Barbara County, California, in Anderson, D. w., and Rymer, M. J., eds., Tectonics and sedimentation along faults of the San Andreas system: Society of Economic Paleontologists and Mineralogists, p. 11-15. APPENDIX 1

Unton Otl and Gas DtvtSJOn Western Reg1on

Un1on Oil Company of California 2323 Knoll Dnve. P 0 '3ox 6176. Ventura, Cal1fOrn1a 93006 Telephone (805) 656-7600

Paleo /StratigraphiC Section October 21, 1982

Mr. John Yaldezian california State University at Northridge 1811 Nordoff Street Northridge, CA 91330

SAN RAFAEL WILDERNESS RESERVE SURFACE SAMPLES

The following report is a SQ~ry of paleontologic determinations based on foraminifera present in forty-one surface samples submitted for examination. Age and paleobathymetric determinations are given for each sample containing foraminifera. Generalized faunal descriptions noted by lettered annotations are also given.

SAMPLE NO. ANNOTATION AGE PALEOBATHYMETRY

82-SR-MF-4 Miocene, undifferentiated 7 Outer neritic to R upper bathyal.

82-SR-MF-5 Early Miocene, early Saucesian Lower bathyal. LS

82-SR-MF-6 Early Miocene, early Sauces ian Lower bathyal. LS

82-SR-MF-7 Early Miocene, early Sauces ian Lower bathyal. LS

82-SR-MF-8 Uncertain, Pro b. Miocene 7 Outer neritic to R,SS upper bathyal.

82-SR-MF-9 Early Miocene, early Sauces ian Lower bathyal. LS

82-SR-MF-10 Indeterminate, barre!"\ Indeterminate

82-SR-MF-ll Indeterminate, barren Indeterminate

82-SR-MF-12 Uncertain; prob. early Miocene Bathyal. R

138 139

Mr. John Yaldezian San Rafael Wilderness Reserve October 21, 1982 Page 2

SAMPLE NO. ANNOTATION AGE PALEOBATHYMETRY

82-SR-MF-13 Early Miocene, early Saucesian Lower bathyal. R

82-SR-MF-14 Late Cretaceous ; Bathyal; prob. middle. CA prob. Campanian.

82-SR-MF-15 Early Miocene; Bathyal SS,R Prob. early Saucesian.

82-SR-MF-16 Miocene, undifferentiated Indeterminate ss

82-SR-MF-1 7 Uncertain; prob. Saucesian Bathyal. R,SS

82-SR-MF-18 Uncertain; prob. Saucesian Bathyal. SS,R

82-SR-MF-19 Indeterminate; barren Indeterminate ss

82-SR-MF-20 Indeterminate; barren Indeterminate ss

82-SR-MF-22 Early Miocene, early Saucesian Lower bathyal. LS

82-SR-MF-23 Middle Miocene, early Relizian Upper lower bathyal. c

82-SR-MF-24 Middle Miocene, early Relizian Upper lower bathyal. c

82-SR-MF-27 Uncertain; Prob. Miocene Bathyal R,SS

82-SR-MF-28 Early Miocene, Early Saucesian Lower bathyal LS(weak)

82-SR-MF-29 Probable late Cretacesou Bathyal; Prob. CA,R middle or deeper.

82-SR-MF-30 Indeterminate; barren Indeterminate. 140

Mr. John Yaldezian San Rafael Wilderness Reserve October 21, 1982 Page 3

SAMPLE NO. ANNOTATION AGE PALEOBATHYMETRY

82-SR-MF-31 Early Miocene, early Saucesian Lower bathyal. LS

82-SR-MF-32 Late Cretaceous, Prob. E-F2 Middle to deep bathyal. CA Zone undifferentiated, Campanian

82-SR-MF-33 Early Miocene, early Saucesian Lower bathyal. LS,SS

82-SR-MF-34 Indeterminate; barren Indeterminate ss

82-SR-MF-35 Late Cretaceous, Bathyal, Prob. lower. CAC Prob. E-F2 Zone, undiff.

82-SR-MF-36 Indeterminate; barren Indeterminate

82-SR-MF-37 Indeterminate; barren Indeterminate

82-SR-MF-38 Middle Miocene; Bathyal C Relizian - Luisian

82-SR-MF-39 Early Miocene, Bathyal R Prob. early Saucesian

82-SR-MF-40 Indeterminate; barren Indeterminate

82-SR-MF-41 Early Miocene, early Saucesian Lower bathyal. LS

82-SR-MF-42 Probably early Miocene, Lower bathyal. R early Saucesian

82-SR-MF-43 Indeterminate; barren Indeterminate

82-SR-MF-44 Prob. early Miocene, Saucesian Bathyal

82-SR-MF-45 Indeterminate; barren Indeterminate

82-SR-MF-46 Indeterminate; barren Indeterminate ss

82-SR-MF-47 Early Miocene; early Saucesian Lower bathyal. LS 141

Mr· John Yaldezian San Rafael Wilderness Reserve October 21, 1982 Page 4

ANNOTATIONS:

LS Generally common foraminifera, dominated by Calcareous species indicative of oceanic lower bathyal environment. A few of the most characteristic species generally present in varying abundances include:

qyroidina soldanii, Cibicides aff, c. me kannai, Melonis aff, M. pompillioides, Plectofrodicularia californica, Bathysiphon sp. (black), Haplaphragmoides trullisata, Cibicides americanus, and Uvigerina hispida (of R. M. Kleinpell).

CA Rare to sparse agglutinated foraminifera suggestive of Late Cretaceous E to F Zones (probably Campanian); weak evidence.

CAC As in CA, but calcareous foraminifers also present.

ss Rare to sparce sponge spicules present.

c Generally abundant calacreous species.

R Rare to few foraminifera present.

Forty-one surface samples from the San Rafael Wilderness Reserve were examined for calcareous nannofossils. Twelve of the samples contain moderately to poorly preserved nannofossils which are age indicative of the early Miocene. One sample (82-SR-MF-38) contains moderately preserved nannos diagnostic of the middle Miocene, while the remaining twenty-eight samples are essentially barren of calcareous nannos.

Zonal calls are applied, when possible, and follow Okada and Bukry (1980). Reworked specimens were not observed except in sample 82-SR-MF-7 where very rare Dictyocoecites bisectus may be reworked from the Oligocene.

Detailed results are as follows:

SAMPLE DESCRIPTION

82-SR-MF-5, 7, 9, 13, 22, 28, 41 AGE: Early Miocene. ZONE: Spherolithus belemnos.

Diagnostic species such as Sphenolithus belemnos, ~ aff, belemnos, Discoaster deflandrei, Reticulofenestra gartneri, Helicosphaera carteri, Discoaster cf. calculosus, and Dictyococcites antarcticus are present in rare to frequent numbers. The early Miocene species Helicosphaera mediterranea was also observed in 82-SR-MF-5. 142

Mr. John Yaldezian San Rafael Wilderness Reserve October 21, 1982 Page 5

82-SR-MF-6, 23, 24, 31, 33 AGE: Early Miocene. ZONE: Indeterminate

These samples contain either ~ deflandrei or ~ gartneri along with H. carteri and assorted Neogene species.

82-SR-MF-38 AGE: Middle Miocene. ZONE: Sphenolithus heteromorphus.

Specimens of ~ heteromorphus are present along with~ deflandrei, Sphenolithus abies and Coccolithus pelagicus.

82-SR-MF-39, 40 AGE: Tertiary, undifferentiated. ZONE: Indeterminate.

Rare ~ pelagicus is present along with rare cyclicargolithus floridanus in sample 40.

82-SR-MF-4, 8, 10, 11, 12, 14, Barren of calcareous nannofossils. 15, 16, 17, 18, 19, 20, 27, 2°, AGE: Indeterminate. 30, 32, 34, 35, 36, 37, 42, 43, 44, 45, 46, 47

C1tl~r A. A. ALMGREN Sr. Paleontologist

M. V. FILEWICZ Area ~aleont legist .-- ., ~ NOTED:~-~ ~WN _.- Regional Paleontologist

AAA/MVF/plh (0146p) cc: T. w. Redin R. T. Budden 143

AfiO Jilt't11"1.10C' /·~·"'•..,...... ao...c ~,..,..tom,~Q.C'(•c:.) "- -~ ... .,.....,.,._a,.o.o..e ~...a! ...... ,_,._c...... ~ a....- 0"' -'!;-...... ~ ·-~ .. -.nc.. 10'-IC' .. ·~ ... ,.w1' .. ·•o- .... =~-- &.::.N··· (.-""""c.•_.•> - ~ ... .. ~"'WC.T"'VC" ...,,.. -- ~ ..•!l.wt"''""cq, ...... ,.._-c.~· o• I ll•tO•tS"""- ...~,.,. ..s:al 1\ICIRa.oc\,..... 1 •-·~o..-. >t----,.,•. ll 0 ...... ~r--0· "''"'"""'"' 20NC •o.e.- ,.,,.~.) -, -- -·--. t!LASS.IFICA"!"ION 01" 'T----·- __ .. IV'\-'RI~- SLh.l~ONI <:._.

"'NVI'C_O>.J,"\t:NT~ --.. .a.o .... c _..•• ~~ I .-...... \M'a./IO!t't.. ,/ --"' ...._...... 04,. ,....,...__, ...... 'II'QAM., II ·~~ -.~..,. ~ '---- ..• _...... ,.MC~ •"'-~~.,...... ,.,._....

Fig. 8-l Classification of benthontc marine environments m terms of depth and relationships with sigmficant wave or water mass boun

...., .... = =

::E UJ z UJ rvPE ,' z ' . . u '0 1 cc .~. ~ ~ ~ l ' I 0 0 Ill ., . v 0 C I 2 ~ [l ( l 0 II{ N" _,= l [ ~ u>~oorr' --fY"""PE- :E ' "((Dl ·- TYPE . \ ~ ~ z : c w- ~ ,.-~- ' ~_,... "" _~-;.;-;,e-1 ' >- .... TYPE a:: "" cc ~ ...., "",...... ' ... ~ =cc ., ~ . i ~ APPENDIX 2

Un1on Oil and Gas Division: Western Reg1on

Union Oil Company of California 2323 Knoll Dnve. P.O. Box 6176. Ventura. Cal1forn1a 93006 Telephone (805) 656-7600

Paleo./ Stratigraphic Section .March 18, 1983

Mr. John Yaldezian California State University at l'tlrthridge 1811 Nordoff Street Northridge, CA 91330 THIN SECTIONS SAN RAFAEL WILDERNESS RESERVE SURFACE SAMPLES SANT~ BARBARA COUNTY, CALIFORNIA The following is a report on the four thin section slides from your sample area. These slides and the small rock samples will be returned under separate cover. SR-TS-5 AGE: Tertiary; probably post Eocene, Miocene. This sample is reported by you as being from the same rock unit as SR-TS-43 which is Middle Miocene, Relizian in age. Lithology is a medium-brown, thin bedded laminated lime mudstone to very fine grained bioclastic lime wackestone/grainstone. Planktic foraminifera (Globigerina spp.) are scattered in occurrence and occasional laminations contain abundant diatoms (?). SR-TS-23 AGE: Probably late Oligocene - early Miocene, late !emorrian - early Saucesian undifferentiated. Light brown, calcareous, hard, very fine grained, angular quartz sandstone with scattered, small megafossil fragments and small foraminifera. NOTE: This sample processed for foraminifera yielded scattered Cibicides cf. c. conoideus and rare poorly preserved, recrystalized-small specimens of Anomalina cf. ~ glabrata, Pulvinulinella sp.and Gyroidina cf. ~ soldani (?). NOTE: Although evidence is very weak this sample may be a lower Rincon shale equivalent, or "Vaqueros" ss. transition.

144 145

SR-TS-43 AGE: Middle Miocene, Relizian; probably Siphogenerina 'Ei"r'anneri Zone. Spl. 1) Medium brown foraminiferal lime wackestone with an abundant diverse calcareous benthic foraminiferal assemblage and scattered planktic foraminifera. Some of the more common benthic species identified in this thin section are: Siphogenerina branneri (A), Baggina robusta (C), and probably Valvulineria aff. v. californica var. appressa (F). Spl. 2) Lithology as in sample 1 above, but with common megafossils (brachiopods?).

t{tl~~ A. A. ALMGREN f Paleontologist AAA/plh (0526H)