CALIFORNIA STATE UNIVERSITY, NORTHRIDGE BENTHIC FORAMINIFERA AND PALEOBATHYMETRY OF THE EOCENE LLAJAS FORMATION, SOUTHWESTERN SANTA SUSANA MOUNTAINS, CALIFORNIA A thesis submitted in partial satisfaction of the requirements for the degree of Master of Science in Geology by Herman Bodo Schymiczek August, 1983 The Thesis of Herman B. Schymiczek is approved: California State University, Northridge ACKNOWLEDGEMENTS This investigation has had the benefit of the assistance, cooperation, advice, and discussions of many individuals, and for all of it I am deeply grateful. My deepest thanks goes to my friend and mentor, Dr. Richard L. Squires, Cal State University, Northridge, for his advice and patience, without which this project could not have been completed. Squires provided thicknesses and aided also in collecting of the microfossil samples. The type­ section traverse used by Squires {1981, 1983b) is the same one used in this report. Dr. Robert G. Douglas, University of Southern California, provided several outstanding discussions as to paleobathymetric interpretations. The skills and techniques required for this investigation were provided by the expert instruction of Dr. Benjamin N. Akpati, Cal State University, Northridge. Alvin A. Almgren, Roy Fulwider, Mark Filewicz, Merton Hill, III, all of the Union Oil Company, reviewed and confirmed many of my identifications as well as providing information from their own studies of the Llajas Formation. Gary Taylor, Cal State University, Northridge, helped in ostracod identification and provided some of the photomicrographs used for the plates. Gerald Haigh, Wiff Haigh, and the Marr Ranch granted permission for access into the study area. Richard Chow, Cal State University, Northridge, provided instruction and assistance in the use of the scanning electron microscope. All of the figures and tables were skillfully drafted by Dale Dow. I am especially indebted to Nancy Pratt and Diana Gary for typing the manuscript and for their patience with my countless revisions. My thanks to the Getty Oil Company for their support. iii Despite the invaluable contributions of those listed above, they are in no way to be held responsible for any identifications, interpretations, or conclusions made in this investigation. iv CONTENTS Page ABSTRACT vii INTRODUCTION 1 PREVIOUS WORK 5 METHODS 7 GEOLOGIC SETTING 9 PALEONTOLOGY 12 AGE 16 PALEOBATHYMETRY 21 INTRODUCTION 21 DIVERSITY 22 BENTHIC FORAMINIFERAL SUBORDER TRENDS 23 HYALINE SUPERFAMILY TRENDS 26 GENERA AND SPECIES TRENDS 26 ASSOCIATED MICROFOSSIL TRENDS 28 SYSTEM A TIC MATERIALS AND METHODS 31 SYSTEM A TIC PALEONTOLOGY 32 REFERENCES CITED 68 v LIST OF ILLUSTRATIONS Figure Page 1. Index map of study area 2 2. Stratigraphic column of the Llajas Formation 3 3. Generalized historical development of stratigraphic nomenclature for the Santa Susana, Llajas, and Sespe Formations 6 4. Sample locations along the type section of the Llajas Formation 8 5. Location of study area relative to the Ventura Basin setting 10 6. Foraminiferal diversity variations in the Llajas Formation 25 7. Distribution of foraminiferal suborders in the Llajas Formation 25 8. Distribution of hyaline foraminifer superfamilies present in the Llajas Formation 27 9. Paleobathymetric curve for the Llajas Formation 30 Table 1. Checklist of foraminifers found in the Llajas Formation 13 2. Known age ranges for benthic foraminifers in the Llajas Formation 19 Plate 1. Foraminifers of the Llajas Formation 79 2. Foraminifers of the Llajas Formation 8l 3. Foraminiferas of the Llajas Formation 83 4. Pseudophragmina clarki, equatorial section 85 vi ABSTRACT BENTHIC FORAMINIFERA AND PALEOBATHYMETRY OF THE EOCENE LLAJAS FORMATION, SOUTHWESTERN SANTA SUSANA MOUNTAINS, CALIFORNIA by Herman Bodo Schymiczek Master of Science of Geology The late early to middle Eocene Llajas Formation, southwestern Santa Susana Mountains, California, contains an abundant and diverse benthic foraminiferal fauna. At least 37 genera and 68 species were identified. Most of the· foraminifers are well preserved and unabraded, with little mixing of faunas, suggesting minimal post-mortem transport. However, shallow water faunas found in the slope facies show signs of abrasion and fragmentation. The age of the Llajas Formation, based on benthic Foraminifera, ranges from lower Ulatisian for the lower one third, through upper Ulatisian for the remainder of the formation. The most recently accepted age of the Ulatisian is lower to lower middle Eocene, and my studies support this. Variations in foraminiferal assemblages within the section suggest paleobathymetries ranging from inner neritic to upper bathyal during deposition of the Llajas Formation. Expressed as the number of species per vii sample, diversity ranges from 4 species per sample from the middle neritic portion of the shallow marine facies to a high of 44 species per sample from the upper bathyal portion of the outer shelf to slope facies. Agglutinated Foraminifera have the greatest abundance and diversity in the upper bathyal portion of the section, whereas porcelaneous types are most abundant and diverse in the middle and outer neritic portion of the section. The hyaline suborder predominates throughout the section. Planktonic foraminifers, diatoms, radiolarians, and calcareous nannofossils all increase in abundance with increasing depth, while ostracodes decrease in abundance with increasing depth. Inner to middle neritic conditions are indicated in the lower and upper portion of the section, indicating transgressive and regressive phases of deposition. viii INTRODUCTION The Llajas Formation in Simi Valley contains a diverse and well preserved benthic foraminiferal fauna, but very few studies on the micropaleontology have been published to date. The purposes of this study are to update and illustrate the taxa, to provide synonymies of the species, and to make the first paleobathymetric interpretation based on the contained microfauna. With this completed, one can make a more meaningful comparison of the microfauna and depositional environments of the Llajas Formation with other formations of similar age along the West Coast. The Llajas Formation crops out in the southwestern Santa Susana Mountains and southern part of Simi Valley (Fig. 1). Most of the outcrops on the south side of Simi Valley are poorly exposed. The best exposure is the 545 m-thick type section in Chivo Canyon (Fig. 1), where there is a 95 percent exposed section. This section was chosen as the main area of study for this reason. At the type section, the Llajas Formation is unconformable over the upper Paleocene to lower Eocene Santa Susana Formation, and it is unconformably overlain by the upper Eocene to Oligocene Sespe Formation (Fig. 2). The basal portion of the Llajas Formation consists of an unfossiliferous conglomerate interpreted to be deposited as a coastal alluvial fan (Squires, 1981). The remainder of the formation consists mostly of very fine-grained sandstone deposited in a shallow-marine environment with minor amounts of siltstone deposited in an outer shelf environment. Microfossils, along with megafossils, tend to be concentrated in numerous beds that are mostly channel-fill deposits. Also present in the formation is a relatively thin 1 2 _Figure 1 Index map of Ventura County with location of study area. 3 EARLY Sespe NONMARINE LATE Formation EOCENE .. z SHALLOW MARINE 0 Regressive Phase -~ en z <t w a: z ~ w wI (.) z OUTER SHELF TO SLOPE 0 - w z With Turbidite-filled "w w ~ Channels ....J 0 Q 0 Q :t Bed ~ ~Stewart 0 1- .. :::E >- w ....J z SHALLOW MARINE "'<t 0: Transgressive Phase "' <( z w "w ~ w 0 1- 0 <( :t ....J ALLUVIAL FAN EARLY Susana EOCENE Formation MARINE FIGURE 2 Stratigraphic column of the Llajas Formation in the vacinity of the type section showing age (in part) and facies of Squires (1981) . '· ' ~.. 4 interval of slope siltstone and turbidite-filled channels within the slope siltstone (Squires, 1981). PREVIOUS WORK Most of the previous geologic studies of the Llajas Formation deal with the stratigraphy and megafossils. The more notable previous stratigraphic works are those by Cushman and McMasters (1936), Stipp (1943), and Squires (1981). Notable megapaleontologic works are those by Waring (1917), Clark (1921, 1926), and Squires (1983a, 1983b). Because the name "Llajas Formation" was not formalized until 1936 by Cushman and McMasters, early workers (Waring, 1917; Kew, 1924; Clark, 1921, 1926; McMasters 1933; and others) referred to the strata equivalent to the Llajas Formation by various names (Fig. 3). Most previous micropaleontological studies of the Llajas Formation deal with the age, taxonomy, and description of benthic foraminifers (Schenck, 1929; McMasters, 1933; Cushman and McMasters, 1936; Laiming, 1940, 1943). The most detailed study was done on a core taken from Getty Oil Company "Tapo Fee" No. 42 well (Cushman and McMasters, 1936). This core was used as part of the formalization of the name "Llajas Formation", and it has since been lost. This well produced oil until 1973, when it was plugged and abandoned. Recently, the emphasis has been to interpret the depositional environments of the Llajas Formation based on sedimentology and megafossils (Squires, 1981) and on microfauna (Schymiczek, 1983a), and to relate this information to available subsurface data (Schymiczek, 1983b). Filewicz and Hill (1983) have recently inferred the age of Llajas Formation based on calcareous nannofossils. 5 CUSHMAN AND McMASTERS. 1936 WARING, 1917 KEW, 1924 ClARK, 1926 i~TIPP.