Facies relations in the Eocene-Oligocene in the Santa Ynez Mountains, California P. C. VAN DE KAMP, J. D. HARPER, J. J. CONNIFF & D. A. MORRIS CONTENTS I General stratigraphy ......... 547 2 Description and interpretation of lithofacies ..... 549 (A) The Turbidite and marine lutite facies ..... 549 (B) The Proximal turbidite facies ....... 55 I (c) The Shallow marine facies ....... 554 (v) The Coastal facies ......... 557 3 Depositional history .......... 558 4 General paleogeography ......... 56o 5 Sedimentological processes ........ 56o 6 References ........... 564 SUMMARY Facies relationships between deep and shallow major regressive sequences. In the first, the marine to continental deposits in the Eocene- Juncal-Matilija sequence, thin-bedded tur- Oligocene sequence of the Santa Ynez Moun- bidites and marine lutites are overlain by, and tains, California, have been studied in detail are laterally equivalent to, very thick proximal to (I) determine interrelationships between turbidites which pass upward into shallow shallower and deeper marine sands (coastal marine and coastal sands. The major sand and turbidite); (2) establish criteria for the accumulations are in the basin margin shallow recognition of genetic sand types; (3) de- marine, coastal, and proximal turbidite facies. termine factors influencing facies distribution; The second regression, the Cozy Dell-Sespe and (4) propose hypotheses of marine sand sequence, lacks significant proximal turbidite deposition. The rocks studied include the deposits but has extensive shallow marine and Anita, Sierra Blanca, Juncal (with the Camino coastal deposits. Facies distribution and Cielo Member), Matilija, Cozy Dell, and stratigraphical sequence are explained as "Coldwater" formations but not the topmost respomes to the interplay of depositional and unit of the Eocene-Oligocene sequence, the structural processes. non-marine Sespe formation. Detailed stratigraphical mapping has clari- In landward sequence, the facies recognized fied correlation in the Eocene sequence to the include: Turbidites and marine lutites, Santa Ynez Mountains. Micropaleontology is proximal turbidites, shallow marine, coastal used in support of correlations and bathy- and continental facies. These occur in two metric interpretations. EOCENE and Oligocene marine sandstones in the Santa Ynez Mountains and adjacent areas, on the north flank of the Ventura Basin (Fig. I), have been studied in detail to (I) determine interrelationships between shallower and deeper marine sands (coastal and turbidite), (2) establish criteria for the recognition of genetic sand types, (3) determine factors influencing facies distribution, and (4) propose hypotheses of marine sand deposition. Jl geol. Soc. Land. vol. x3o, I974, pp. 545-565, I I figs. Printed in Northern Ireland. Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/130/6/545/4884852/gsjgs.130.6.0545.pdf by guest on 27 September 2021 546 P. C. van de Kamp et al. This sequence is suitable for the objectives of this study as there is continuous exposure of variable quality over a distance of I oo km from Ojai in the east, west to Point Conception (Fig. z). The sequence records deposition in a wide variety of environments ranging from deep water to continental. This range permits comparison of lithostratigraphical correlation and facies interpretation with biostratigraphical data and paleoecological interpretations, thereby contributing insight into microfaunal facies variation. The type section for the Ynezian and Bulitian Stages (Kleinpell & Weaver 1963) at Santa Anita Canyon, occurs in this sequence. Detailed study was confined to the area south of the Santa Ynez Fault, in the Santa Ynez Mountains (Fig. I) and north of this fault only reconnaissance was undertaken. Correlation across the fault was based on lithological similarity, micropalaeontological data and facies interpretation. In this study over I ooo microfaunal samples were examined by Conniff and Morris to give age and environmental data but only the most significant palaeonto- logical results are summarized. Dibblee (I95o , I966 ) described the geology of the western and central Santa Ynez Mountains. Theses dealing with the distribution and origin of various units in the Eocene-Oligocene sequence include those by Jestes (I963), Stauffer (I965), and Johnson (i968). Other pertinent stratigraphical studies are by Kelley (~943), ~ ~ \ ................ ~ ~ / ~ ompo, ~NOR1 OF STUDY AREA ~~-.~~~~ ~ .... ~. k~ .......... ..... .............................................. ....... .....~,:~.. .......~.:~~ ...~,.....~.~--~-~ ~, ........... \ ,. / " ~~~~ii ~: ~.. P~ntnceptlon ~ ~ Fillmore" 10 20 30 WVentura . , 10 Km=o 30 ~ AREA STUDIED BY RECONNAISSANCE Ve..... \ F I G. I. Index map of the western Transverse Ranges area showing the general distri- bution of Eocene and Oligocene rocks in the shaded areas. The Santa Ynez Mountains lie south of the Santa Ynez Fault. Measured sections referred to in this study are indicated as numbered lines on the map as follows: z. West Cojo Canyon, 2. East Cojo Canyon, 3. Gato Canyon, 4. San Augustin Canyon, 5. Santa Anita Canyon, 6. Cuarta Canyon, 7. Gaviota Pass, 8. East Gaviota, 8A. Dos Vistas Ranch, 9. Santa Ynez Peak, i o. Tecolote Tunnel, ~ ~. Gibraltar Road, z2. Romero Road, 13. Divide Peak, ~4- Wheeler Springs. Major paleocurrent trends in the Eocene and Oligocene are shown by arrows. Most transport was from the north and east. Our data is supplemented by that of Jestes (1963). Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/130/6/545/4884852/gsjgs.130.6.0545.pdf by guest on 27 September 2021 Eocene-Oligocene sedimentary fades, California 547 Page et al. (I95I), Bailey (z952), Kerr & Schenck (I928), Link (z972) and O'Brien (1972). In the broadest sense, the structure of the Santa Ynez Mountains west of Ojai is homoclinal, dipping steeply toward the south and locally overturned (e.g., Matilija Overturn, Kerr & Schenck I928). This homocline is truncated on the north by the Santa Ynez Fault (Fig. t). In detail, the structure is more complex. Several significant open folds trend obliquely (NW-SE) to the E-W trend of the mountains. The most significant fault in the area, the Santa Ynez Fault, shows northward thrusting as well as left-lateral displacement (Dibblee 1966). Other less significant faults occur within the homocline and appear to be associated with folding. Vertical and lateral offsets on these faults are generally on the order of several tens or hundreds of metres. I. General stratigraphy All the stratigraphical terminology given is lithostratigraphical and this, and applications, differ from previous work (Kelley z943, Dibblee I95% i966, Bandy & Kolpack 1963). The changes are based on litkostratigraphical and palaeon- tological correlations from east to west in the Santa Ynez Mountaim (Table I). TAB LE 1 EOCENE-OLIGOCENE STRATIGRAPHY. NORTH FLANK OF VENTURA BASIN Comparison of correlations of earlier studies with this work. Kleinpell and Weaver (1963) Page, Marks, (Dib~ee, 1950) Walker (19,51) van de Kamp and Harper (this work) Western Santa Eastern Santa Weste rn Eastern East Northeast Series Stage Stage Series Ynez Mtns. Ynez Mtns. Santa '~nez Santa Ynez Ventura Basin Ventura Basin Oligoce,w Zemorrian Alegfia Upl~' (.) ""~L._ Sespe ? ? Refugian Oligoceno "Coldwater" "Coldwater" Upper (shale) Middle :zhlde) °'C~ter °' : ...... Co~dwater" Middle (ss) Lower (as) Refugian Upper t shale) Upper (shale) I Upper (shale) I Upper (shale) F. Upper r.9 Cozy Dell Sand Cozy D(II Sand ~>. Cozy Dell Sand ~,. Cozy Dell Sand Lower (shale) Cozy Dell N ~> (Circle B Sz) '" O o o r..)o r_l r..) ¢.1 Lower (;hale) Lower (shale) i Lower (shale) ' Lower (shale) i Sacate Narizian Derrydale and (Dibblee, 1950; Matilija Matilij j Matilija Matilija Thorn Meadows Kelley, 1943) Narizian Eocene "Cozy Dell" Upper Upper Upper Juncal D Middle u,l -~ CaminoCielo ~ ClminciCielo "~ Camino Cielo "Matilija" Sand ~ Saw Sand Ulatisian Ulatbian : Lower i Lov~er LoMr Junr~ ? Mu~oFm Sierra Bh,nca ? Penutian ,~ SierraBlancl Sierra Blanca Sierra Blanca Penutian Lower :"Poppin' S 1ale") Bulitian Bulitian Paleocene " n " ' Paleoc~ne Ynezian Ynezian ///f/I// //--7-7-7' ? :"77"~ I Maestrichtian Up0~r Cretaceous Espada lu$ to Cretaceous I Cretace( Cretaceous Cretaceous Honda I Campanian Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/130/6/545/4884852/gsjgs.130.6.0545.pdf by guest on 27 September 2021 548 P. C. van de Kamp et al. South of the Santa Ynez Fault, the Eocene-Oligocene clastic sequence (Fig. 2) is underlain disconformably by Upper Cretaceous siltstones and sandstones (Jalama formation). North of the fault, the Eocene is unconformable on either Mesozoic granitic, Franciscan metamorphic, or Lower to Upper Cretaceous sedimentary rocks. Overlying the Eocene-Oligocene sequence in the area south of the fault are the continental Sespe formation (Eocene to Miocene) in the east and the transgressive Vaqueros sandstone (Lower Miocene) in the west. All formation contacts within the Lower Tertiary sequence are transitional and conformable. The Anita, Sierra Blanca, Juncal and Cozy Dell Formations are dominantly shale. Within the Juncal is the major Camino Cielo Sandstone member. The Camino Cielo member occurs as three major sand accumulations, each of which grades laterally into dominantly shale and siltstone. Folding discussed previously coincides with areas where the sand is minimal. Sandstone makes up the bulk of the Matilija and "Coldwater" Formations. The lateral