ANALYSIS OF COMPETING HYPOTHESES FOR THE TECTONIC EVOLUTION OF THE BAKERSFIELD ARCH by Jefferson Vasconcellos A Thesis Submitted to the Department of Geology California State University Bakersfield In Partial Fulfillment for the Degree of Masters of Petroleum Geology Winter 2016 Copyright By Jefferson Vasconcellos 2016 ANALYSIS OF COMPETING HYPOTHESES FOR THE TECTONIC EVOLUTION OF THE BAKERSFIELD ARCH By Jefferson Vasconcellos This thesis has been accepted on behalf of the Department of Geology by their supervisory committee: ' uf~i::;e,~¥&'f: . Professor of Geology Committee Chair Robert Negrini, PhD Professor of Geology Dirk Baron, PhD Department Chair, Professor of Geology ABSTRACT The widespread presence of Neogene and Quaternary units in the southeastern San Joaquin Valley provide evidence for the tectonic evolution of the Bakersfield Arch, an area of major oil production in California. The purpose of this study is to test two different age hypotheses for the uplift of the Arch: middle Miocene and late Quaternary. Electric log correlations of stratigraphic marker units were used to create isochore maps of sedimentary packages of various ages across the Arch. These data indicate that changes in horizontal distribution and thickness of stratigraphic units across the Arch are influenced by two distinct uplift events in the area: 1) during middle to late Miocene time and 2) latest Miocene (post-Etchegoin Formation deposition) to Pleistocene time. Future work incorporating more detailed correlation of individual chert markers within the Monterey Formation would more closely define the exact timing of the earlier episode of uplift in the area. Age diagnostic data are insufficient to determine the time of onset of the later period of uplift. 2 ACKNOWLEDGMENTS I would like to express the deepest appreciation to my thesis advisor, Janice Gillespie, who had the patience and the generosity to share her knowledge and expertise in this study. I definitely learned a lot with every correction she made along the way. I would like to show my special gratitude and thanks to my committee members Dirk Baron and Robert Negrini. Thanks are also extended to Sue Holt and Elizabeth Powers for guiding and helping me in order to make the study a well done achievement. Special recognition to my friends that were always available to share and hang out when I needed a study break. My thanks and appreciations also go to my family for the moral and financial support which helped me completing this study. I also would like to thank my beloved girlfriend Khanh Lu for providing me with all love and companionship when I needed her the most during long hours of study away from my family, country and culture. 3 TABLE OF CONTENTS Abstract………………………………………………………………………………….………..2 Acknowledgements………………………………………………………………………….…...3 Table of Contents…………………………………………………………………………….…..4 List of Figures……………………………………………………………………………….…....6 Introduction…………………………………………………………………………………..…..8 Geologic Setting……………………………………………………………………………….....9 Stratigraphy of the Bakersfield Arch Area……………………………………………………11 Vedder Freeman-Jewett/Olcese Bena Round Mountain Monterey Stevens Chanac Santa Margarita Fruitvale Bellevue Gosford Coulter Reef Ridge Etchegoin/Macoma San Joaquin Tulare Petroleum System………………………………………………………………………….……24 Importance Maturation Timing Traps and Seals Previous Studies……………………………………………………………………...…………28 Middle Miocene Hypothesis Late Quaternary Hypothesis Data and Methods………………………………………………………………………………38 Results………………..……………………………………………………………….…………40 4 Top of Etchegoin to top of Macoma Top of Macoma to top of Reef Ridge Top of Reef Ridge to top of Monterey Top of Monterey to top of Round Mountain Top of Round Mountain to top of Freeman Top of Freeman to top of Vedder Discussion……………………………………………………………………………………….61 Conclusion………………………………………………………………………………………65 References…………………………………………………………………………….…………67 Appendix………………………………………………………………………………………...71 5 LIST OF FIGURES Figure 1 Location map of the Bakersfield Arch, Buttonwillow and Tejon depocenters. Figure 2 Tectonic setting of the California borderland, from Oligocene to Miocene. Figure 3 Stratigraphic column of the Bakersfield Arch area. Figure 4 Diagrammatic cross section showing stratigraphic relations of Tertiary formations south of the Bakersfield Arch. Figure 5 Distribution of the Antelope and Fruitvale Formations Figure 6 Stratigraphic column of the Bakersfield Arch area showing the Monterey turbidites. Figure 7 Correlation chart of Tertiary formations in southeastern San Joaquin Valley. Figure 8 Map of oil fields in the Bakersfield Arch area. Figure 9 Seismic image and interpreted stacking of chert and sandstone beds. Figure 10 Tectonic model of the Tehachapi block rotation. Figure 11 Model of the kinematics involved in breaking the south San Joaquin Valley blocks apart and the formation of basins in the Bakersfield Arch area. Figure 12 Kinematic map of the westward deflection of the southern Sierra Nevada Batholith. Figure 13 Model of the Isabella anomaly and delamination of the mantle lithosphere. Figure 14 Diagram showing the onset convergence and Coast Range uplift and sediment- load subsidence. Figure 15 Stratigraphic column of the Southern San Joaquin Valley and sedimentary packages. Figure 16 Etchegoin-Macoma isopach map. Figure 17 Etchegoin-Macoma cross- section. Figure 18 Macoma-Reef Ridge isopach map. Figure 19 Macoma-Reef Ridge cross-section. 6 Figure 20 Reef Ridge-Monterey. isopach map. Figure 21 Reef Ridge-Monterey cross-section. Figure 22 Monterey-Round Mountain isopach map. Figure 23 Monterey-Round Mountain cross-section. Figure 24 Round Mountain-Freeman isopach map. Figure 25 Round Mountain-Freeman cross-section. Figure 26 Freeman-Vedder isopach map. Figure 27 Freeman-Vedder cross-section. Figure 28 Late Miocene paleogeography of the San Joaquin basin area. Figure 29 Present day topography of the Bakersfield Arch area. 7 INTRODUCTION The Bakersfield Arch is a major structural feature located in the southern end of the San Joaquin Valley in California (Fig. 1). The city of Bakersfield is located along the axis of the Arch and the city of Los Angeles lies about 100 miles to the southeast. The San Andreas Fault is to the west and the Sierra Nevada to the northeast. San Joaquin Valley Sierra Nevada Bakersfield Tejon Bakersfield Arch Los Angeles Fig. 1 – The Bakersfield Arch plunges to the southwest (delineated by the red lines). The Buttonwillow depocenter to the north and Tejon depocenter to the south are shown in yellow. The Arch plunges southwest from the city of Bakersfield toward the valley center. Oil generated at the Tejon depocenter to the south and Buttonwillow depocenter to the north of the Bakersfield Arch migrated into oil fields along the crest of the Arch. Timing of Arch uplift 8 relative to deposition of organic-rich source rocks and reservoir sandstones affects the distribution and thickness of the reservoirs, timing of oil migration, and the trapping characteristics of the local oil fields. A better understanding of the regional geology of the Bakersfield Arch oil fields is hindered due to the lack of studies that extend beyond the individual oilfield-scale. Previous works that discuss the tectonic evolution of the Bakersfield Arch area and geologic setting include Bartow and McDougall (1984), Bloch (1991), Sheehan (1986), and Saleeby et al. (2013). This study tests two hypotheses--one that the Arch was activated in middle Miocene time and the other that the Arch did not form until late Quaternary--by presenting cross-sections, stratigraphic columns and shale/chert thickness maps based on available log data in the area. The goal of this study is to present data leading to an up-to-date and more complete interpretation of the broader regional geology across the Bakersfield Arch. GEOLOGIC SETTING The San Joaquin basin is located east of the San Andreas Fault which forms the boundary between the North American and Pacific plates. The margin was the site of a subduction zone during Jurassic through early Miocene time at which time the San Joaquin basin was a forearc basin. To the west, the Pacific plate was subducting beneath the North American plate, which led to the formation of a continental volcanic arc represented by the Sierra Nevada Mountains to the east of the San Joaquin Valley. Today the plutonic roots of the arc are exposed east of the Arch. Sediments of the Great Valley Group filled the forearc basin north of the Arch during Jurassic to Cretaceous time. In the southern part of the San Joaquin Valley, the Great Valley 9 sequence thins, possibly due to uplift associated with the oroclinal bending of the southernmost Sierra Nevada in the early Tertiary (Bartow, 1991). Saleeby et al. (2013), on the other hand, attributed the lack of Cretaceous and Paleocene strata in the southern part of the basin along the Arch to the collision and low-angle subduction of a seamount (correlated to the Shatsky Rise of the modern NW Pacific Basin) in this area. This event caused late Cretaceous uplift and erosion of the forearc basin and adjacent Sierran batholith across about 500 km of the batholith in the southern California region (Saleeby et al., 2013). A major tectonic change in the plate margin occurred during early to middle Miocene time when the East Pacific spreading center encountered the trench, creating the Mendocino triple junction (Fig. 2). This caused the plate boundary to change from subduction to dextral strike slip. The current California segment of the western