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.

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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.

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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

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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

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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.

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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.

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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 North American plate boundary is complex and consists of a subduction zone to the north of the Cape Mendocino, and dextral strike slip along the San Andreas Fault from there to Central Mexico (Bloch, 1991).

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Fig. 2 – Tectonic setting along the coast of California from Oligocene to present showing the change from a convergent to a transform margin (Atwater, 1970).

STRATIGRAPHY OF THE BAKERSFIELD ARCH AREA

Vedder Formation

Figure 3 shows the stratigraphy, lithology and paleobathymetry of the units in the

Bakersfield Arch area. One of the oldest units is the Vedder Formation. Microfossils from subsurface samples indicate a Zemorrian age for the Vedder Formation (33.5-22 Ma) (Oligocene to earliest Miocene) (Bartow and McDougall, 1984; Bartow, 1991; Olson, et al., 2009). The

Vedder Formation is characterized by blue-gray, medium grained, well-sorted clean sand, interbedded with brown organic siltstone layers (Fig. 3) (Albright et al., 1957) and its thickness

11 may reach more than 300 m (984 ft) locally (Bartow and McDougall, 1984). It most often comformably overlies the Walker Formation but, in places, is the lateral marine equivalent of the upper part of the nonmarine Walker Formation (Bartow and McDougall, 1984). The silts and sands of the Freeman and Jewett formations unconformably overlie the Vedder Formation along the east margin of the basin, north of the Bakersfield Arch, but the contact may be conformable south of the Bakersfield Arch and farther west (Bartow and McDougall, 1984). In some areas the Vedder Formation is unconformably overlain by a 10 foot marker bed of Saucesian age known as the “grit zone” (Albright et al., 1957), which consists of fine to coarse-grained sand with black chert granules and quartz pebbles in a clay to silt matrix (Hackel and Krammes,

1958).

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5400

5100

4800

4500

4200

3900

3600

3300

3000

2700

2400

2100

1800

1500

1200

900

600

300

Fig. 3: Stratigraphic column showing the formations in the Bakersfield Arch area. The average thickness of the Vedder Formation is from Bartow and McDougall (1984), and the San Joaquin and Tulare thicknesses are from Keller et al., (2000). The other average thicknesses are calculated from well log curves: Freeman=258 m, Round Mountain=294 m, Monterey=516 m, Reef Ridge=240 m, and Etchegoin=959 m.

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The Vedder Formation was deposited in a shallow marine environment (Ramseyer et al.,

1993). Subsurface mapping and analysis of well log data on the Bakersfield Arch suggests that the Vedder Formation was deposited following a period of rapid subsidence (ca. 50 cm/1000 years) that lead to the formation of a ramp geometry with constant slope between nonmarine and deep-marine environments (Bloch, 1986).

Freeman-Jewett/Olcese formations

Foraminiferal faunas indicate an upper Zemorrian and Saucesian age for the

Freeman Silt (Olson, et al., 2009). Therefore the age of the Freeman Silt is about 23-16.5 Ma

(early Miocene). It is characterized by grey-white, sandy to clayey, micaceous siltstones containing fairly abundant early Miocene foraminifera (Fig. 3) (Olson, et al., 2009).

The upper Jewett Formation is a massive, concretionary, silty sandstone with megafossils, sharkteeth and abundant marine mammal remains (Barnes, 1979). Its basal part consists of grey, poorly sorted, coarse-grained sandstone containing sub-angular quartz grains and black chert pebbles at the base of the Pyramid Hill Sand Member (also known as the grit zone) (Barnes,

1979).

The composite thickness of the Freeman Silt and Jewett Sand is about 300 m (984 ft) in the Kern River area (Bartow and McDougall, 1984). The fossil assemblages indicate a deep water environment for the deposition of the Freeman Silt, probably at lower middle bathyal depths (1500-2000 m) (Bartow and McDougall, 1984; Olson, et al., 2009).The Freeman Silt gradationally overlies and intertongues with the Jewett Sand and also intertongues with the overlying Olcese Sand (Fig. 4). (Bartow and McDougall, 1984).

Bartow and McDougall (1984) indicate a Saucesian and Relizian age (early Miocene) for the Olcese Formation. The Olcese Formation is a sandstone with some interbedded siltstone and

14 pebbly sandstone and conglomerate. It reaches a thickness of 300 to 360 m (984 to 1181 ft) locally (Bartow and McDougall, 1984). This unit was deposited in a wide range of paleoenvironments including nonmarine, estuarine and outer shelf depositional settings (Olson, et al., 2009). In outcrop, the middle part is probably nonmarine, although the upper and lower parts are marine and abundantly fossiliferous in some areas (Addicott, 1970). Farther basinward, to the west, the Olcese is wholly marine (Bartow and McDougall, 1984).

The unit intertongues basinward with the underlying Freeman Silt and the overlying

Round Mountain Silt, and apparently pinches out completely within a few kilometers of the outcrop at the south end of the basin (Bartow and McDougall, 1984). This unit was mapped together with the Freeman-Jewett interval in this report.

Bena Gravel

Bartow and McDougall (1984) defined the age of the Bena Gravel to be late early

Miocene, middle Miocene, and late Miocene. This unit is restricted to the area south of the Kern

River where it can reach 750 m (2460 ft) thick (Bartow and McDougall, 1984). The Bena Gravel is divided into an alluvial fan facies of sandstone and cobble conglomerate, and a paralic facies containing plant material, fresh-water diatoms, foraminifers, rare oysters and marine mammal bones (Bartow and McDougall, 1984). The Bena Gravel changes facies within a short distance northward into the Olcese Sand and the Round Mountain Silt, and southwestward into the Edison

Shale of Kasline (Fig. 4) (Bartow and McDougall, 1984). The Edison Shale probably represents

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Bakersfield

Los Angeles

Fig. 4 – Diagrammatic cross section showing stratigraphic relationships of Tertiary formations south of the Bakersfield Arch, especially the Bena Gravel (alluvial-fan and paralic facies) (blue) grading southwestward into the Edison Shale of Kasline (green) during the late early and middle Miocene. Location of the cross-section (blue line) and the axial trace of the Bakersfield Arch (black thick solid line) are shown on the inset map (Modified from Bartow and McDougall, 1984).

a transitional facies between the Bena and the marine facies of the Round Mountain Silt and

Fruitvale Shale (Bartow and McDougall, 1984).

Round Mountain Silt

Foraminifera indicate the age of the Round Mountain Silt to be late Relizian to Luisian

(16.5-13.5 Ma—middle Miocene) (Beck, 1952). The Round Mountain Silt is a marine, greenish grey, micaceous, clayey to sandy siltstone with abundant foraminifera representing upper middle bathyal (1000-1500 m) depths (Fig. 3) (Olson, et al., 2009). The Round Mountain Silt reaches a

16 thickness of nearly 244 m (800 ft) in the vicinity of the Kern River (Albright et al., 1957). The unit conformably overlies the Olcese Sand and is unconformably overlain by the Santa Margarita or Chanac formations in the Kern River area (Bartow and McDougall, 1984). The depositional environment of the Round Mountain Silt was offshore and deep marine (Pyenson et al., 2009).

Monterey Formation

The age of the Monterey Formation varies with location because the sedimentation commenced and terminated at different times in separate depocenters. Behl (1999) notes the typical duration of deposition to be from about Luisian to early Delmontian (16-6 Ma--middle to late Miocene). Its thickness is up to 762 m (2500 ft) in some parts of the basin (Graham and

Williams, 1985). Interbedded rocks of different lithologies such as shale, mudstone, sandstone, pyroclastics, and carbonates are present within the Monterey Formation (Fig. 3) (Bramlette,

1948). However, the strata is characterized by rocks with high silica content such as silica- cemented rocks termed porcelanite and porcelanous shale, diatomaceous members, and large amounts of hard and dense silica rocks classed as chert and cherty shale (Bramlette, 1948).

Scheirer and Magoon (2007) point out that the Antelope Shale is 10-6.5 Ma in age and the

Fruitvale is 13.5-6.5 Ma, and therefore their upper boundaries are considered the top of the

Monterey Formation. Further, both formations are shales, and their lithologies are considered to be equivalent. However, Scheirer and Magoon (2007) also mentions that the well database indicates that the Antelope is confined to the western margin of the San Joaquin Basin and therefore should be considered separately from the Fruitvale Shale. As it can be seen in figure 5, the Antelope Shale forms the upper part of the Monterey Formation on the west and the Fruitvale

Shale comprises the upper Monterey Formation on the east.

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Bakersfield

Antelope Fruitvale

18, 035 0 (5497 m)

FEET

Fig. 5: Green represents the approximate area where the Antelope Formation is present, whereas the Fruitvale Formation approximate location is represented by the blue area. Black line shows the approximate location of the Bakersfield Arch crest. Polygons are oil fields and dots represent the wells chosen for mapping in this project (DOGGR (Division of Oil, Gas, and Geothermal Energy), 1998).

Sand-rich sediment sourced from the highlands to the west, south and east produced submarine fans that prograded across the deep floor of the basin during deposition of the

Monterey Formation (MacPherson, 1978; Webb, 1981). Therefore, the Monterey Formation serves as both source and reservoir for hydrocarbons. The Stevens sandstone occurs in the upper part of the Monterey Formation and represents deep water turbidite deposition. Figure 6 shows

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O Chert

P Chert

Fig. 6 – Stratigraphy of the Bakersfield Arch area showing the most important sequences in the Stevens sandstones. SB=sequence boundaries, LST=lowstand systems tracts, and black triangles are condensed sections (Modified from Hewlett and Jordan., 1993).

that the Stevens sandstone in the southern San Joaquin Basin contains lowstand systems tracts of the Rosedale, Coulter, Gosford, and Bellevue sequences in ascending order (Hewlett and Jordan,

1993). The three younger sequences were deposited during late Miocene and contain progradational wedges (high stand and lowstand), incised valley fills, and retrogradational systems (transgressive systems tracts) (Hewlett and Jordan, 1993). The lowermost lowstand wedge is the Rosedale sequence, which was deposited during the middle Miocene.

Layers of siliceous shales and chert-rich rocks (N, O, and P cherts) are interbedded within

19 the Stevens sandstones. Recognizing these chert beds with the use of geophysical logs is the primary method of subdividing the turbidite systems. The log signature of the chert beds is suppressed SP and high resistivity.

The Santa Margarita and Chanac formations consist of coarse-grained sandstone and conglomerate, with the Chanac Formation representing the eastern, non-marine facies and the

Santa Margarita Formation being the western shallow-marine equivalent. The Santa Margarita and Chanac formations (Fig. 7) represent the shallow marine and non-marine lithostratigraphic equivalent units of the deeper water Stevens sandstone (Hewlett and Jordan, 1993).

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West East

Monterey Fm.

Fig. 7 - Correlation chart of Tertiary formations in southeastern San Joaquin Valley. The red box emphasizes the variation within the Monterey Formation including the Santa Margarita and Chanac (Modified from Bartow and McDougall, 1984)

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Reef Ridge Formation

The Reef Ridge Formation was deposited during Delmontian time (10-5 Ma) (late

Miocene) and is defined as a soft, blue (brown weathering), shale with minor beds of sandy shale

(Fig. 3) (Barbat and Johnson, 1934). The average thickness of the unit in the Bakersfield Arch area is 240 m (787 ft). The sandstone at the base of the Reef Ridge Shale south of the

Bakersfield Arch is interpreted to be deposited by a turbidity current (Bloch, 1991). This unit can be distinguished from the underlying upper Monterey formation by the higher resistivity of the latter (Bloch, 1991).

Etchegoin Formation/Macoma Claystone

Although age dating of the Etchegoin Formation is difficult due to the lack of age- diagnostic microfauna and macrofauna, it appears that the formation is 5.5-4.5 Ma (Delmontian)

(late upper Miocene to early Pliocene) (Scheirer and Magoon, 2007). Its lithology consists of bluish-gray to green shale, diatomaceous, micaceous claystones, and tan siltstones; lower in the section, the sediments are dark-brown medium-grained, massive, and pebbly (Fig. 3) (Peirce,

1949). Its thickness varies from 305 to 1067 m (1000 to 3500 ft). This unit is considered to be the basinward equivalent of the lower Kern River Formation, which Baron et al. (2008) dated as

6 Ma in age (latest Miocene) based on an ash bed found near the top of the Kern River

Formation. The Etchegoin Formation is known to pinch out approximately five miles northeast of Bakersfield (Olson, et al., 2009). The Macoma Claystone, which occurs at the base of the

Etchegoin Formation, is mostly marine claystone and siltstone (Wagoner, 2009). This unit provides a useful time-stratigraphic marker.

The Etchegoin Formation consists of interbedded shallow marine sandstone and offshore shale. This boundary is time transgressive in places (Bloch, 1991). These deposits are interpreted

22 to be marine based on scattered occurrences of shelly fragments and bioturbation (Link et al.,

1990). The Etchegoin Formation was deposited during a minor transgression during Pliocene time that resulted in deposition of shallow marine deposits, which separate the nonmarine

Chanac and Kern River Formations (Olson, et al., 2009).

Seismically, the Etchegoin Formation is distinguished from the Reef Ridge Shale by an onlap surface separating the fairly discontinuous reflections of the former from the continuous reflections of the latter (Bloch, 1991). This poor continuity of seismic reflections is probably due to the fact that the Etchegoin Formation contains discontinuous sandstone bodies (Bloch, 1991).

San Joaquin Formation

Deposition of the San Joaquin Formation occurred between 4.5 and 2.5 Ma (Delmontian)

(late Pliocene) (Scheirer and Magoon, 2007). It consists of silt and clay beds alternating with beds of sandstone and conglomerate and contains marine, brackish water and nonmarine fossils

(California Department of Water Resources, 2006), with a thickness of 100 to 1100 m (328 to

3609 ft) (Fig. 3) (Keller et al., 2000). This unit grades into the Kern River Formation to the east.

A brackish water depositional environment is indicated by the occurrence of mollusks of

Mya sp. (Loomis, 1990; MacGinitie, 1935). As the seaway connection between the Pacific

Ocean and the San Joaquin basin became more restricted, deposition of the San Joaquin

Formation sediments focused on the central region of the basin (Loomis, 1990). Fluvial and deltaic environments prevailed in the north and south parts of the basin (Loomis, 1990).

Tulare Formation

The age of the Tulare Formation is 2.5-0.6 Ma (Pleistocene) (Scheirer and Magoon,

2007). This formation consists of lenticular deposits of poorly sorted clay, silt, and sand with occasional interbeds of well-sorted fine-to-medium grained sand (Fig. 3) (California Department

23 of Water Resources, 2006). Its thickness can reach 2000 m (6562 ft) (Keller, et al., 2000). The base of this unit is the First Mya Sand within the San Joaquin Formation, which separates fresh water deposits of the Tulare Formation from brackish water deposits of the San Joaquin

Formation (Loomis, 1990). This marks a change from a predominantly marine environment to a continental environment of lakes, swamps, and streams (Page, 1983).

Lakes of varying size occupied the valley throughout the deposition of this sequence and caused the deposition of clay-rich sediments (Bloch, 1991). Coarser-grained fluvial and alluvial sediments are also present (Bloch, 1991). Page (1983) notes that sediments have been derived chiefly from the Sierra Nevada on the east and the Coast Ranges on the west and were deposited as alluvial-fan, deltaic, flood-plain, lake and marsh deposits.

PETROLEUM SYSTEM

The Bakersfield Arch area contains many important oil fields. Since the 1930's, when the first reservoirs were discovered in the Miocene Stevens sandstones of the southern San Joaquin basin, about 472 MMBO and 1.3 TCF has been produced from 22 fields in the Bakersfield Arch region (Hewlett and Jordan, 1993) (Fig. 8).

The importance of the Tejon and Buttonwillow depocenters as major areas for generation of hydrocarbons and the related oil migration into the Bakersfield Arch is also highlighted by

Peters et al. (2012). Chemometric analyses of geochemical data for 165 crude oils were used to identify oil families in the area, and their corresponding source rocks, migration pathways, reservoirs, and filling histories. The results show that the source rocks for the oil families include the (1) Eocene Kreyenhagen and Tumey formations, (2) Miocene Monterey Formation

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Fig. 8 – Map showing oil fields in the Bakersfield Arch area. Oil and gas produced since the 1930's are shown as MMBO and BCF, respectively. Blue area is the East Gosford field, green is the Canal oil field, orange the North Coles Levee and purple the South Coles Levee, as mentioned in the text. The red line shows the location of the cross-section shown on Fig. 9 (Modified from Hewlett and Jordan, 1993).

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(Buttonwillow depocenter), and (3) Miocene Monterey Formation (Tejon depocenter) (Peters et al., 2012).

Maturation timing

Oils analyzed to date show that the source rocks near the Bakersfield Arch occur predominantly within the middle and late Miocene-age Monterey Formation. This formation is fine-grained and biosiliceous, with total organic carbon ranging from less than one to nearly six percent (Gautier and Scheirer, 2008). The source rock feeding the reservoirs at the south part of the Bakersfield Arch matured within the Tejon depocenter, whereas the Buttowillow depocenter was the location of the source area for the north part of the Bakersfield Arch. Geochemical analyses and petroleum systems modeling confirm that depths of about 4 to 4.6 kilometers (2.5 to 2.9 miles) are needed to produce oil from the Monterey Formation (Gautier and Scheirer,

2008). This depth constraint is important because the oldest members of the Monterey Formation are currently at this depth on the Bakersfield Arch, and even the youngest strata of the Monterey are in the oil window in the Tejon depocenter (Gautier and Scheirer, 2008).

Traps and seals

In addition to acting as source rocks, shales of the Monterey Formation also serve as seals due to their low permeability and their ability to compartmentalize the sandstones bodies.

Siliceous shales and cherts, such as the N-, O-, and P-cherts, are important regional seals for reservoirs (Fig. 9). The complex geology along the Bakersfield Arch provides a vast array of traps for hydrocarbons, including updip sandstone pinch-outs, grain compaction decreasing the permeability of rocks surrounding reservoirs, and structural traps created by anticlines and faults.

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Fig. 9 – Seismic line and interpreted stacking of strata showing the chert condensed sections (CS) (N, O and P cherts) and sequence boundaries (SB). The Coulter, upper Gosford, and lower Bellevue of the Stevens sandstone sequence are shown here compartmentalized between the chert marker beds. The approximate location of the cross-section is shown on Fig. 8 (red line) (Hewlett and Jordan, 1993).

Almost every field on the Bakersfield Arch has at least one pool that is a combination stratigraphic-structural trap, even though a few reservoirs occur in structurally dominated traps

(Hewlett and Jordan, 1993). Traps in the Coulter turbidite system are basically structural, with faulting on post-depositional structures such as folds and within depositional (compactional)

27 anticlines. Compactional anticlines are formed by four-way closure developed by differential compaction of channel/overbank complexes and/or turbidite lobes (Hewlett and Jordan, 1993).

Stratigraphic traps in the lower Gosford system are created by sandstone deposits interbedded with low permeability shale such as those in the East Gosford oil field. The Gosford turbidite lobes at the Canal oil field (Fig. 8) are trapped by compactional anticlines. Anticlines also trap hydrocarbons in the upper Gosford turbidite wedge (i.e., Coles Levee oil field,)

(Hewlett and Jordan, 1993).

Pinch-out of strata across the top of anticlinal structures is the most common trap mechanism for the lower Bellevue turbidite wedge. Up-dip pinch-out of confined turbidite and channel fill sandstones along and across structural features and within slope gullies are the trap mechanisms in the upper Bellevue sands (Hewlett and Jordan, 1993).

PREVIOUS STUDIES

Middle Miocene Hypothesis for growth of the Bakersfield Arch

Using a kinematic block model based on paleomagnetic data and faulting due to the clockwise rotation of the Tehachapi block (Fig. 10), Bloch’s (1991) model indicates that the extension in the southern San Joaquin basin is synchronously linked to the early Miocene clockwise rotation of the Tehachapi block. However, the model does not explain pre-rotation extension in the Edison area (prior to 22 Ma) that is responsible for faulting during late

Oligocene.

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Edison Area

Fig. 10 – Model explaining the kinematics involved in the formation of the Tejon Embayment, Edison area and Tehachapi Basin during clockwise rotation of the Tehachapi Block. The area is subdivided into several small blocks in an attempt to capture the behavior at this complex juncture between rotated and unrotated blocks (Bloch, 1991). The green rectangle represents the approximate location of the Bakersfield Arch, right above the Tejon Embayment.

Bloch (1991) uses sequence stratigraphy techniques to investigate the tectonic activity in the region during early Miocene time. His study employs seismic, borehole and outcrop data.

The tectonic activity started at 24-20 Ma with the passage of the Mendocino triple junction at the latitude of the Southern San Joaquin basin, converting the adjacent plate interaction from

29 subduction to dextral slip (Bloch, 1991). Tectonic activity in the region south of the Bakersfield

Arch started during early Miocene and continued into the middle Miocene (Bloch, 1991).

Bloch (1991) notes that tectonic events in the San Joaquin basin are related to the plate tectonic setting and the structural history of the basin should hold some record of the Mendocino triple junction passage. Therefore, the change of the plate margin configuration might have introduced compressional tectonic forces responsible for the rotation of the Tehachapi block during early

Miocene (Figs. 11a and 11b) and the subsequent uplift of the Bakersfield Arch during middle

Miocene. Bloch (1991) cites Bartow and McDougall (1984) who consider the formation of the

Arch to have occurred in middle Miocene time.

The lateral motion caused by the clockwise rotation of the Tehachapi block during the period from 22 Ma to 16 Ma (early Miocene), along the south and east margin of the basin, is inferred to have caused the crust beneath the basin to absorb the lateral motion caused by rotation

(Bloch, 1991). The San Joaquin basin could be subjected to extensional stress and/or deform in a manner which allows movement of the Tehachapi block into space formerly occupied by the basin (Bloch, 1991). Therefore, compressional forces probably caused the formation of folds as the Tehachapi block rotated northward into the southern part of the San Joaquin basin. Post-early

Miocene shortening, mainly across the Temblor Range in the southwestern end of the San

Joaquin Basin, is not included in the model. The magnitude and orientation of extension observed in the Mojave Desert equals that expected for the degree of rotation determined from paleomagnetic studies (Bloch, 1991).

30

(a)

(b)

7 ± 8 degrees

24 ±11 degrees 21 ± 8 degrees

Figs. 11a and 11b – Early Miocene (22-16 Ma) kinematic model suggesting timing of Bakersfield Arch formation. (a) Regional map showing blocks (red polygons) prior to clockwise rotation of the Tehachapi block. (b) Regional map showing blocks (red polygons) after the clockwise rotation of the Tehachapi block. Figure 11b suggests compressional forces imposed on the basin as the Tehachapi block rotated. Green arrows represent direction of compression. Approximate location of the Bakersfield Arch is represented by the green rectangle. Paleomagnetic data are posted for comparison to the degree of rotation of sub-blocks (locations of 7 ± 8 degrees, 21 ± 8 degrees and 24 ± 11 degrees rotations are shown). Blue arrows indicate locations where paleomagnetic data were taken (Modified from Bloch, 1991).

31

Sheehan’s (1986) study also proposes a mechanism for Arch formation during middle

Miocene time. His study suggests that growth of the Arch probably began 16 Ma (early middle

Miocene) along with crustal extension in the Basin and Range Province. Left lateral movement along the Garlock fault at about 16 Ma (early middle Miocene) and right lateral displacement along the White Wolf fault caused clockwise rotation of the southern end of the Sierra Nevada

(Fig. 12). The rotation and extension eventually caused the Sierra Nevada block to break along the Kern Canyon-Breckenridge-White Wolf fault system. The Tehachapi granitic block, which is bounded by the Kern Canyon-Breckenridge-White Wolf fault on the north and the Garlock fault on the south, was then moved southwestward across the south end of the San Joaquin Valley.

With the continued movement of the Tehachapi block and subsequent wedging of the Sierra

Nevada block westward into the San Joaquin Valley, the Bakersfield Arch was pushed up. This tectonic explanation gives a mechanism responsible for uplifting the Arch. Also, it considers a more regional event than the more localized clockwise rotation of the Tehachapi block referred to by Bloch (1991).

32

SNB

GCV

BAR BA TM

MD

Fig. 12 – Middle Miocene < 16 Ma model for Arch uplift. Geologic map of California showing westward (clockwise) deflection of the southern Sierra Nevada Batholith. Figure suggests that the southern San Joaquin Basin was pushed northward as compression was imposed from the south by the rotation of the Tehachapi block. Deflection is shown by the blue arrow; Garlock fault (brown); San Andreas fault (yellow); White Wolf fault (red); Breckenridge fault (green); Kern Canyon fault (blue); BAR=Basin and Range Province; MD=Mojave Desert; TM=Tehachapi Mountains; BA=Bakersfield Arch (purple area); SNB=Sierra Nevada Batholith (silver area), and GCV=Great Central Valley (light orange area) (Modified from Sheehan, 1986).

Even though Bartow and McDougall’s (1984) study does not give an exact age and mechanism for Arch formation, it provides evidence that the Arch was uplifted during the middle

33

Miocene, which supports Sheehan’s (1986) early middle Miocene age hypothesis. The evidence used by Bartow and McDougall (1984) for dating the Arch uplift is the coarse clastic materials of the Bena Gravel which originated from the uplift of the Sierra Nevada concurrent with faulting and subsidence in the southern part of the basin. Alluvial-fan and paralic facies of the Bena

Gravel were deposited by a fan delta formed at the steep east margin of the basin in response to the tectonic uplift in the Sierras to the east (Bartow and McDougall, 1984).

The 15-10 Ma Bena Gravel grades southwestward into the Edison Shale (Fig. 4), which contrasts with the simple stratigraphy to the north of the Arch, where rapid facies changes are not as apparent. This difference is evident by late early and middle Miocene, therefore, the

Bakersfield Arch became an important boundary between the far south end of the basin and a relatively more stable shelf area to the north by this time period (Bartow and McDougall, 1984).

Late Quaternary Hypothesis

Saleeby et al. (2013), note that some of the structural features of the San Joaquin Basin, such as the Bakersfield Arch, are the result of mid-Pleistocene orogeny. Saleeby et al. (2013) describe the Bakersfield Arch as a compressional uplift created by the merging of a faulted uplift northeast of Bakersfield, here described as the Kern Arch, and actively growing anticlines to the west. Saleeby et al. (2013) identify the Kern Arch (Bakersfield Arch) as a structure formed by ascending mantle lithosphere during late Quaternary. Saleeby et al. (2013) relate this structure to the most recent phase of lower crustal lithosphere delamination below the Tulare Lake basin area, known as the Isabella anomaly, and the consequent rise of asthenosphere material beneath the area of the Kern Arch (Fig. 13).

34

Fig. 13 – Block diagram showing how the high-wave-speed body known as the Isabella anomaly caused the uplift of the Arch. This anomaly occurs beneath the Tulare Lake basin and causes delamination of the mantle lithosphere. The red line shows the location of the delamination hinge, which is the place where the mantle lithosphere separates from the base of the crust. Upwelling of mantle lithosphere into the area south and east of the delamination hinge is interpreted to have caused uplift of the Bakersfield Arch, here depicted as the Kern Arch (Saleeby et al., 2013).

Cecil et al. (2014) use thermomechanical models of mantle lithosphere removal from beneath the southern Sierra Nevada to study vertical surface displacements in this area. This study claims that the principal burial episode to be 2.5 Ma or later, and exhumation to 1 Ma or later. Burial temperatures coupled with modern burial depths, and constraints on the geothermal gradient indicate that the Kern Arch (Bakersfield Arch) strata underwent about 1000-2400 m

(3281-7874 ft) of Pliocene-early Quaternary subsidence (Cecil et al., 2014). Cecil et al. (2014) estimates that about 1000-1800 m (3281-5906 ft) of Kern Arch strata were unroofed after 1 Ma

35 as a function of position on the Arch. The cause of such tectonic subsidence in the San Joaquin

Basin is attributed by the study to be the viscous coupling between the lower crust and a downwelling mass in the delaminating slab, whereas the exhumation event is interpreted to be the result from the northwestward peeling back of the slab and the associated replacement of dense lithosphere with buoyant asthenosphere that drove rapid rock and surface uplift (Cecil et al., 2014).

Another possible mechanism for post-Miocene uplift of the Arch is proposed by Miller

(1999). This study addresses the timing and causes of uplift of the Coast Ranges Provinces in central California and connects this event with a forebulge structure at the Bakersfield Arch area.

Compression and shortening of the crust perpendicular to the San Andreas fault as a consequence of oblique convergence of the Pacific and North American plates are thought to be the cause of uplift in the Coast Ranges (Miller, 1999). This convergence and the resulting shortening correspond to a clockwise rotation of 8 to 23 degrees of the Pacific plate motion (Miller, 1999).

The tectonic configuration change from strike slip with slightly oblique extension in central

California, to strike slip with oblique convergence angle along the San Andreas is thought to have been caused by this event (Miller, 1999). Shortening perpendicular to the San Andreas fault resulted from this event since the convergence angle after rotation has been about 5 degrees at latitude 38 degrees (Miller, 1999). The onset of convergence created a foreland basin caused by the basin flexing downward under the weight of north-vergent thrust sheets along the southern margin of the San Joaquin Basin (figure 14). A small flexure called a forebulge forms along the leading edge of the thrust belt-foreland basin pair and may have resulted in uplift of the area near the Bakersfield Arch. Even though many other studies indicate age estimates for the uplift of the

Coast Ranges between 3 and 8 Ma, Miller (1999) uses reflection seismic, geohistory-subsidence

36 and lithologic data of the Miocene-Pliocene-Pleistocene sedimentary record to propose that the foreland-style uplift began about 6 Ma and no later than 5.4 Ma (tectonic subsidence), with a second event of subsidence at about 3.4 Ma (sediment-load subsidence driven by sea-level drop, climate change, erosion and enhanced sediment flux into the basin) (Fig. 14).

Forebulge

Fig. 14: Diagram showing the onset of convergence and Coast Range uplift by 5.4 Ma (A) and sediment-load subsidence by 3.4 Ma (B). The forebulge, which may have contributed to uplift of the Bakersfield Arch area, is indicated by the blue arrow (Miller, 1999).

37

DATAAND METHODS

This study focuses on well data available from the California Division of Oil, Gas and

Geothermal Resources (DOGGR) and data published in other studies available in the literature.

Available well log data along the Bakersfield Arch are used to delineate the extent and thicknesses of the Etchegoin, Macoma, Reef Ridge, Monterey, Round Mountain, Freeman, and

Vedder formations and determine the effect, if any, of the uplift of the Bakersfield Arch on the thicknesses and distributions of these lithofacies across the Arch.

Consequently, cross-sections and stratigraphic thickness maps of shale units were created based on well data across the crest of the Arch. Only shales are used as the tops for this study rather than sandstones because the finer-grained clastic rocks have a more regional distribution within the basin, whereas the distribution of sandy turbidites form local accumulations. Due to its widespread presence in the Bakersfield Arch area, the only sand unit used for this study is the

Vedder Formation.

The stratigraphic interval this study focuses upon ranges from the top of the Etchegoin

Formation (latest Miocene or early Pliocene) to the top of the Vedder Formation (Oligocene).

The Macoma Claystone is used as a local marker within the Etchegoin Formation. Using the tops defined for each unit and marker based on the log curves, thickness maps of six sedimentary packages are presented (Table 1). Figure 15 shows these packages in a stratigraphic column.

38

From (top) To (top)

1. Etchegoin Macoma

2. Macoma Reef Ridge

3. Reef Ridge Monterey

4. Monterey Round Mountain 5. Round Freeman Mountain 6. Freeman Vedder

Table 1: Tops used for mapping six sedimentary packages.

Etchegoin-Macoma Macoma-Reef Ridge Reef Ridge-Monterey

Monterey-Round Mountain

Round Mountain- Freeman

Freeman-Vedder

Fig. 15: Stratigraphic column of the Southern San Joaquin Valley and sedimentary packages (Scheirer and Magoon, 2007).

39

The thickness and distribution of the lithofacies across the Arch are used to determine the timing of uplift of the Arch relative to the stratigraphy. Sedimentary packages will be thicker in areas of subsidence and thinner over uplifts. For example, if strata pinches out or thins against the flanks of and across the top of the Arch, uplift occurred before or during deposition of that specific unit, unless there is an unconformity above the unit indicating that it thins by erosion and the unit is non-marine in nature. If strata is continuous or thickens across the Arch, deposition probably occurred before uplift of the Arch. The cross-sections show how the thicknesses of the units change in the third dimension

By using the age of each unit, it is possible to set age constraints for the uplift event and test the two competing hypotheses for the timing of uplift presented in this study, i.e., 1) the middle Miocene hypothesis supported by Sheehan (1986), Bartow and McDougall (1984) and

Bloch (1991) and 2) the late Quaternary hypothesis by Saleeby et al. (2013). These methods assume that the tops of the shale beds and chert layers approximate time horizons within the area occupied by the Bakersfield Arch.

RESULTS

Mapping

Top of Etchegoin to top of Macoma

The contour lines of the Etchegoin-Macoma (Fig. 16) isopach map are perpendicular to the crest of the Arch and the values show gradual thinning northeastward. Thickness reaches

4000 ft (1219 m) to the west, decreasing to less than 200 ft (610 m) to the east. The cross-section shows no change in thickness across the axis of the Arch (Fig. 17).

40

4000 (1219 m)

3000 (614 m)

2000 (610 m)

1000 (305 m)

Bakersfield 0

N

18, 035 0 (5497 m)

FEET Fig. 16: Top of Etchegoin to top of Macoma isopach map. Black line shows the approximate location of the Bakersfield Arch crest. Contour lines show the Etchegoin Formation thinning to the northeast but not across the crest of the Arch. Polygons are oil fields and dots the wells chosen for this project. Contour interval = 100 feet (30.5 m).

41

(a)

A ; l ; l ; l Bakersfield

; l

; A` l N

18, 035 0 (5497 m)

FEET

42

(b) A

2918540 the Arch Axis of

FEET

0

(61 m) 200

0

FEET (3094 m) 10150

A’

Fig. 17: (a) Map showing the cross-section line (blue line), axis of the Arch (triangle), oil fields (polygons), and wells (dots). (b) Cross-section showing that the Etchegoin-Macoma interval gets thicker as the axis of the Arch is approached.

43

Top of Macoma to top of Reef Ridge

The Macoma-Reef-Ridge isopach map shows contour lines perpendicular to the crest of the Arch and thickens to the southwest from the basin margin to the basin axis (Fig. 18).

Thickness is nearly 1800 ft (549 m) in the southwest and decreases to 200 ft (61 m) in the northeast. The cross-section shows this interval thickening to the southeast into the Tejon sub- basin (Fig. 19).

1900 (579 m)

1000 (305 m)

200 (61 m)

Bakersfield

N

18, 035 0 (5497 m)

FEET Fig. 18: Top of Macoma to top of Reef Ridge isopach map. Black line shows the approximate location of the Bakersfield Arch crest. Contour lines show the Macoma Formation thinning to the northeast. Polygons are oil fields and dots the wells chosen for this project. Contour interval = 50 feet (15 m).

44

(a)

A

Bakersfield

A` N

18, 035 0 (5497 m)

FEET

45

(b) A

the Arch Axis of

FEET

0

(61 m) 200

0

FEET (3094 m) 10150

A’

Fig. 19: (a) Map showing the cross-section line (blue line), axis of the Arch (triangle), oil fields (polygons), and wells (dots). (b) Cross-section showing the Macoma-Reef Ridge interval thickening to the southeast into the Tejon sub-basin.

46

Top of Reef Ridge to top of Monterey

The Reef Ridge-Monterey (Fig. 20) isopach map shows gradual thinning across the crest of the Arch. Thickness values reach about 1500 ft (457 m) on the flanks of the Arch, and 350 ft

(107 m) along the crest line of the Arch. The Reef Ridge-Monterey (Fig. 21) cross-section clearly shows thinning as the over the crest of the Arch.

2000 (610 m)

1000 (305 m)

200 (61 m) 600 Bakersfield

00 6

N

1400

18, 035 1400 0 (5497 m)

FEET f Fig. 20: Top of Reef Ridge to top of Monterey isopach map. Black line shows the approximate location of the Bakersfield Arch crest. Contour lines show the Reef Ridge Formation gradually thinning as the crest of the Arch is approached from the south and north. Polygons are oil fields and dots the wells chosen for this project. Contour intervals = 25 feet (7.5 m).

47

(a)

A

Bakersfield

N

A` 18, 035 0 (5497 m)

FEET

48

(b) A

FEET

the Arch Axis of 0

(61 m) 200

0

FEET (3094 m) 10150

A’

Fig. 21: (a) Map showing the cross-section line (blue line), axis of the Arch (triangle), oil fields (polygons), and wells (dots). (b) Stratigraphic cross-section hung on a datum of the top of the Reef Ridge Shale showing how the thickness of the Reef Ridge-Monterey interval changes across the Arch--thinning across the crest of the Arch.

49

Top of Monterey to top of Round Mountain

This interval from the top of the Monterey to the top of the Vedder Formation does not show thinning across the crest of the Arch. The Monterey-Round Mountain isopach map primarily presents northeast thinning from the basin axis onto the basin margin (Fig. 22). The contour lines are roughly perpendicular to the crest of the Arch, and the values range from 4400 ft (1341 m) to the south and less than 200 ft (61 m) to the northeast. The Monterey-Round

Mountain cross-section shows thickening to the southeast (Fig. 23).

50

4000 (1219 m)

3000 (914 m)

1000 2000 (610 m) 1200 1600 2000 1000 (309 m)

Bakersfield 0

4000

4400

N

18, 035 0 (5497 m)

FEET

Fig. 22: Top of Monterey to top of Round Mountain isopach map. Black line shows the approximate location of the Bakersfield Arch crest. Contour lines show the Monterey Formation thinning to the northeast. Polygons are oil fields and dots the wells chosen for this project. Contour intervals = 100 feet (30.5 m).

51

(a)

A

Bakersfield

N

18, 035 A` 0 (5497 m)

FEET

52

(b) A

FEET the Arch Axis of

0

(61 m) 200

0

FEET (3094 m) 10150

A’

Fig. 23: (a) Map showing the cross-section line (blue line), axis of the Arch (triangle), oil fields (polygons), and wells (dots). (b) Cross-section showing how the thickness of the Monterey- Round Mountain interval increasing to the southeast.

53

Top of Round Mountain to top of Freeman

The Round Mountain-Freeman isopach map shows northeast thickening with values ranging from 100 ft (30.5 m) to the southwest to about 2000 ft (610 m) to the northeast (Fig. 24).

The cross-section indicates roughly continuous thicknesses across the crest of the Arch (Fig. 25).

940 700 3000 (914 m)

1000 2000 (610 m)

1000 (304 m)

100 (30 m)

Bakersfield

280

100

N

18, 035 0 (5497 m)

FEET Fig. 24: Top of Round Mountain to top of Freeman isopach map. Black line shows the approximate location of the Bakersfield Arch crest. Contour lines show the Round Mountain Formation thinning to the southwest. Polygons are oil fields and dots the wells chosen for this project. Contour interval = 40 feet (12 m).

54

(a)

A

Bakersfield

A`

N

18, 035 0 (5497 m)

FEET

55

(b) A

FEET

0

(61 m) 200

0

FEET (3094 m) 10150

the Arch Axis of Round Mountain

2906077 2906077

A’

Fig. 25: (a) Map showing the cross-section line (blue line), axis of the Arch (triangle), oil fields (polygons), and wells (dots). (b) Cross-section showing that the thickness of the Round Mountain-Freeman interval (does not show any relevant thickness trend across the Arch

56

Top of Freeman to top of Vedder

The Freeman-Vedder isopach does not show any relevant trend (Fig. 26). Thicknesses vary throughout the map without any distinguishable pattern, other than slightly thinning from the basin axis onto the basin margin. If anything, the thickness appears to increase along the crest of the Arch. Values range from less than 200 ft (61 m) to about 1600 ft (488 m) at different locations of the map. The cross-sections show little change in thickness across the crest of the

Arch other than a slight thickening (Fig. 27).

57

2000 (610 m) 1000

800

1000 1000 (305 m)

200 (60 m) Bakersfield

N

18, 035 0 (5497 m)

FEET Fig. 26: Top of Freeman to top of Vedder isopach map. Black line shows the approximate location of the Bakersfield Arch crest. Contour lines do not show any relevant trend. Polygons are oil fields and dots the wells chosen for this project. Contour intervals = 20 feet (6 m).

58

(a)

A

Bakersfield

A`

N

18, 035 0 (5497 m)

FEET

59

(b) A

FEET

0 the Arch Axis of

(61 m) 200

0

FEET (3094 m) 10150

A’

Fig. 27: (a) Map showing the cross-section line (blue line), axis of the Arch (triangle), oil fields (polygons), and wells (dots). (b) Cross-section showing that the thickness of the Freeman-Vedder interval does not show any relevant trend across the Arch.

60

DISCUSSION

The maps and cross-sections suggest that the Arch was not a positive feature influencing the sedimentation during the deposition of the Round Mountain (middle Miocene) and Freeman

(early Miocene) silts. However, the thinning of the Reef Ridge Shale (Fig. 20 and 21) over the crest of the present-day location of the Arch does indicates that it was a positive feature during late Miocene time.

If the Arch were a positive feature during middle Miocene time, as proposed by Bartow and McDougall (1984) and Bloch (1991), or early middle Miocene (Sheehan,1986) , the

Monterey Formation might be expected to thin across the Arch since the Monterey is a middle to late middle Miocene unit. However, figures 22 and 23 show the Monterey thinning northeastward toward the basin margin, not over the crest of the Arch. This could be due to the fact that the Arch is a southwest plunging structure; therefore, uplift might have started to the northeast, affecting deposition of the Monterey in this area first, causing the Monterey to appear thinner to the northeast. However, thinning to the northeast would be expected regardless as this would represent greater proximity to the basin margin. The axis of the basin lies to the west of the Bakersfield Arch. This area was the site of rapid subsidence and was occupied by a deep marine environment whereas the northeast margin of the basin adjacent to the Sierra subsided more slowly and was the site of a shallow shelf or non-marine depositional setting as can be seen in figure 28. If the Monterey were mapped as individual units instead of mapping it as a single package as in the case of this study, uplift of the Arch may have occurred during Monterey deposition as well.

The irregular distribution of middle to late Miocene turbidites in the Monterey

Formation, such as the Stevens sands, suggest the presence of several smaller positive features

61

Fig. 28: Late Miocene (about 9-10 Ma) paleogeography of the San Joaquin basin area (Bartow, 1991).

such as the Coles Levee and Elk Hills anticlines on the seafloor in the area of the Arch by the time of deposition of the uppermost Monterey. Hardoin (1962) and Dosch (1962) present cross- sections along the North and South Coles Levee fields, respectively, indicating that the younger turbidite sequences within the Monterey thin over or pinch out against the anticline structures, whereas the older turbidites have continuous thicknesses over these structures. At the Elk Hills

62 field, the cross-sections presented by Lorshbough (1967) indicate that the Olig sand within the upper part of the Reef Ridge Formation is truncated by an unconformity; the Reef Ridge thins slightly and the thickness of the turbidites in the underlying Monterey is continuous over the anticline structure.

The distribution of Monterey and Reef Ridge turbidite sands in the Coles Levee and Elk

Hills fields on the western end of the Bakersfield Arch suggest that these smaller anticlinal structures had no appreciable seafloor topography until later when the uppermost Monterey sands and the Reef Ridge Shale were deposited. The thinning of the uppermost Stevens sands over the tops of the Elk Hills and Coles Levee structures indicate that these smaller anticlines were rising during deposition of the uppermost part of the Monterey. These are smaller structures superimposed upon the larger Bakersfield Arch structure and, as such, they do not reflect uplift of the broader area of the Arch itself.

The uplift of the broader Arch primarily appears to have affected the thickness of the

Reef Ridge, since isopach maps and cross-sections indicate that this unit thins across the Arch.

The Etchegoin and Macoma intervals do not show evidence of thinning across the Arch, suggesting that the seafloor topography created by the rising Arch during Reef Ridge deposition was filled in prior to or during deposition of the upper Reef Ridge.

The present day topography seen in the study area (Fig. 29) consists of a topographic high across the crest of the Arch. Sedimentary layers of the younger Etchegoin, San Joaquin,

Kern River and Tulare formations dip away from the crest indicating renewed uplift in the area of the Arch after deposition of these younger formations. A geologic map presented by Bartow

(1984) shows the Kern River Formation (late Miocene to Pliocene) to the south of the Arch dipping 5-15 degrees in the southeast direction, and to the north dipping 5-10 degrees in the

63 northwest direction.

Although the present topography and structural data suggest that a second uplift event took place, an exact date for the start of this event is not possible to determine due to the lack of good markers within post-Etchegoin units. Consequently, it was not possible to generate thickness maps of post-Etchegoin units. The second uplift event, however, could have started at any time after the deposition of the Etchegoin Formation, which is the youngest mapped formation not showing evidence of thinning over the Arch. Since the exact age at which

Etchegoin deposition ended is not known, this second uplift event could have started during early

Pliocene or late Miocene. Also, the Kern River Formation, which is thought to be a late Miocene formation and time equivalent to the upper Etchegoin, was not mapped due to the lack of a good marker unit. Therefore, the Arch could have been reactivated in late Miocene time, when the lower Kern River Formation was deposited.

Thickening of the Etchegoin Formation (Fig. 17) as the axis of the Arch is approached from the south and north may be related to the Pliocene subsidence event described by Cecil et al. (2014). This relationship can be drawn based on the ages of subsidence of the basin (2.5 Ma or later) and deposition of the Etchegoin (5.5 to about 5 Ma). Although the exact age of the

Etchegoin Formation is not known, deposition of this formation is believed to have ceased during late Miocene or early Pliocene time (around 5 Ma). The Pliocene subsidence event is dated to 2.5 Ma or later according to Cecil et al. (2014). Therefore, the appreciable thickening

(about 61 m or 200 ft) of the Etchegoin observed on well 2918540 (Fig. 17) might be related to the Pliocene subsidence episode mentioned by Cecil et al. (2014).

64

Min., Avg., Max. Elevation: 334, 361, 379ft. Total Distance: 18.6 mi. Imagery Date: 3/26/2015

110m (361ft)

105 m (344ft)

100 m (328ft)

5 km (3mi) 15 km (9mi) 25 km (15mi) Fig. 29: Google Earth satellite photo showing the present day Bakersfield Arch area. The graph below shows the topopraphic profile along the red line in the photo. The black line represents the approximate location of the Arch crest.

CONCLUSION

The maps and cross-sections created in this study suggest that two periods of uplift took place across the broader Bakersfield Arch area: 1) during middle to late Miocene time and 2) during latest Miocene (post-Etchegoin Formation deposition) to Pleistocene time. The evidence for the former is based on the thinning of the interval between the top of the Reef Ridge to the top of the Monterey across the present day location of the axis of the Bakersfield Arch. The formations older and younger than this interval do not thin across the crest of the Arch.

Uplift of the Arch may have started as early as middle Miocene as proposed by previous studies however, in this study, sub-units within the Monterey Formation were not mapped

65 separately. Future detailed thickness mapping using chert marker beds within the Monterey

Formation may provide better resolution of the timing of uplift.

Finally, the present day topography in the area shows a positive feature across the crest of the Arch which suggests reactivation of the feature since deposition of the Etchegoin Formation.

The dip of post-Reef Ridge strata away from the crest of the Arch and the fact that the Etchegoin is the youngest mapped unit that does not thin over the Arch suggest that uplift was reactivated on or after latest Miocene to Pleistocene time.

66

References

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Beck, R. S., 1952, Correlation chart of Oligocene, Miocene, Pliocene, and Pleistocene in San Joaquin Valley and Cuyama Valley areas, in Field trip routes, geology, oil fields, AAPG, SEPM, SEG Guidebook, Joint Annual Meeting, Los Angeles, California, 1952, p. 104.

Behl, R. J., 1999, Since Bramlette (1946): the Miocene Monterey Formation of California revisited: Geological Society of America, Special Paper 338, p. 301-313. Bloch, R. B., 1986, Ramp-style deposition of Oligocene marine Vedder Formation, San Joaquin Valley, California (abs.): AAPG Bulletin, v. 70, p. 463.

Bloch, R. B., 1991, Studies of the stratigraphy and structure of the San Joaquin Basin, California [Ph.D. diss.]: Stanford, California, Stanford University, 319 p.

Bramlette, M. N., 1948, The Monterey Formation of California and the origin of its siliceous

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rocks: United States Department of the Interior, Geological Survey Professional Paper 212, 57 p.

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Cecil M.R., Saleeby Z., Saleeby J., Farley K., 2014, Pliocene–Quaternary subsidence and exhumation of the southeastern San Joaquin Basin, California, in response to mantle lithosphere removal: Geosphere, v. 10, p. 129–147.

DOGGR (Division of Oil, Gas, and Geothermal Energy), 1998, California oil & gas fields, Volume 1 – Central California: California Department of Conservation, n. TR11.

Dosch, M., W., 1962, South Coles Levee oil field: Calif. Div. of Oil and Gas, Summary of Operations – Calif. Oil Fields, vol. 48, no. 2, p. 63-72.

Gautier, D. L., and Scheirer, A. H., 2008, Miocene total petroleum system-lower Bakersfield Arch assessment unit of the San Joaquin basin province: Chapter 14 in Petroleum systems and geologic assessment of oil and gas in the San Joaquin Province, California, U.S. Geological Survey Professional Paper 1713, p. 17.

Graham, S. A., and Williams, L. A., 1985, Tectonic, depositional and diagenetic history of Monterey Formation (Miocene), central San Joaquin basin, California: American Association of Petroleum Geologists Bulletin, v. 69, p. 385-411. Hackel, O., and Krammes, K. F., 1958, Stratigraphy: San Joaquin Geological Society Guidebook, Spring Field Trip, Round Mountain area, p. 10-11 and 14-15. Hardoin, J., L, 1962, North Coles Levee oil field: Calif. Div. of Oil and Gas, Summary of Operations – Calif. Oil Fields, vol. 48, no. 2, p. 53-61. Hewlett, J. S., and Jordan, D. W., 1993, Stratigraphic and combination traps within a seismic sequence framework, Miocene Stevens turbidites, Bakersfield Arch, California: AAPG memoir, v. 58, p. 135-162.

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Group, west-central San Joaquin Valley, California: Field Trip Guidebook - Pacific Section, Society of Economic Paleontologists and Mineralogists 64, p. 231-246

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APPENDIX: wells and tops (measured depths) used in the study

Top of Units or Stratigraphic Markers (ft) TD API Location Maco- Reef Round (ft) Etchegoin Monterey Freeman Vedder ma Ridge Mountain

35 27S 2963863 17500 5630 10200 14395 14830 23E 25 27S 2909478 14770 4370 7500 9112 14252 23E 3 27S 2949212 15880 12700 23E 12 27S 2946452 16505 8500 9698 11282 12280 13194 23E 35 27S 2941957 15476 4620 7490 7720 11960 12560 24E 17 27S 2909489 13716 4300 7860 12800 24E 8 27S 2937135 13253 7400 8960 12720 24E 7 27S 2937131 13453 7880 8980 12700 24E 6 27S 2948583 15435 4750 8400 9720 12950 13510 24E 36 27S 2930723 6050 2780 2990 5420 5946 26E 25 27S 2942852 5765 2830 3190 5450 26E 27 27S 2950284 7355 3670 4260 5810 6915 26E 15 27S 2930721 7737 3280 3000 4970 5828 26E 16 27S 2930728 7549 4070 5630 6489 26E 12 27S 2930718 7213 2450 4350 5005 26E 2 27S 2930722 6703 2530 4310 4975 26E 4 27S 2930727 7486 3570 5350 6125 26E 32 27S 2916088 3546 2280 2490 27E 34 27S 2916183 4220 3300 3918 27E 36 27S 2916564 3098 2190 3045 27E 36 27S 2916187 3187 1380 2325 3057 27E 26 27S 2916138 3747 1620 2600 3268 27E 27 27S 2914928 3700 1910 2900 3585 27E 28 27S 2914931 4178 1520 1680 3250 3850 27E 24 27S 2916503 4517 1250 2150 27E

71

Top of Units or Stratigraphic Markers (ft)

TD API Location (ft) Etchegoin Reef Round Macoma Monterey Freeman Vedder Ridge Mountain

2916056 20 27S 4219 2150 2280 27E 13 27S 2916125 2935 2190 2850 27E 15 27S 2914787 5540 1360 3150 3780 27E 17 27S 2914930 2364 1880 2010 27E 12 27S 2952963 2713 1150 2010 2685 27E 10 27S 2914779 1429 1295 1429 27E 7 27S 2916157 3046 2170 2500 27E 9 27S 2914786 2513 1500 1855 2400 27E 1 27S 2914932 2876 2105 2665 27E 2 27S 2916100 4656 1020 1700 2500 3160 27E 4 27S 2916105 5205 2100 2960 3540 27E 4 27S 2914763 5084 1770 2100 2950 3515 27E 6 27S 2914728 2808 1900 2210 27E 31 27S 2912296 2765 1780 2508 28E 32 27S 2912377 2201 870 1700 2175 28E 33 27S 2912378 2127 740 1710 2121 28E 34 27S 2912251 2053 400 1450 28E 35 27S 2912248 1403 750 1380 28E 28 27S 2900006 2144 410 1182 28E 30 27S 3004666 3600 870 1720 2437 28E 22 27S 2912275 1539 885 1462 28E 20 27S 2914070 2341 1670 2280 28E 19 27S 2912479 2768 980 1810 2456 28E 15 27S 2912667 1307 780 1285 28E 15 27S 2954754 1878 1210 1706 28E 18 27S 2914057 2565 1150 1880 2468 28E 11 27S 2912395 1183 588 1137 28E

72

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Round Etchegoin Macoma Monterey Freeman Vedder Ridge Mountain

10 27S 2954441 1808 1180 1690 28E 9 27S 2957343 1977 1020 1876 28E 8 27S 2912084 2337 870 1650 2296 28E 7 27S 2912013 1987 1185 1900 28E 3 27S 2912225 1564 135 900 1327 28E 4 27S 2912458 1954 640 1230 1638 28E 5 27S 2954644 2345 855 1615 2262 28E 6 27S 2912492 1989 1130 1820 28E 5 28S 2903173 13614 4863 10670 12120 23E 30 28S 2964052 16285 23E 4 28S 3048481 12709 5600 11595 23E 8 28S 2919848 12900 10705 23E 14 28S 2975353 13700 5860 9490 23E 10 28S 2947380 20753 5652 10500 23E 35 28S 2921230 11988 4955 24E 36 28S 2919890 10987 24E 23 28S 2936449 7502 3809 6441 8138 10917 12390 24E 33 28S 2916643 11510 7638 8432 9820 10503 R25 34 28S 2916657 11700 7472 8156 10245 11280 25E 35 28S 2916682 11500 8273 9410 10242 25E 25 28S 2971552 11830 7885 10229 11227 25E 26 28S 2965091 12092 9675 10401 11390 25E 27 28S 2916579 11695 8078 9458 10149 11275 25E 21 28S 2930750 11754 6539 10575 11738 25E 20 28S 2930749 12404 4830 6759 11130 25E 19 28S 2960414 13170 9907 25E 16 28S 2955045 13963 5670 9819 10660 11552 25E

73

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Round Etchegoin Macoma Monterey Freeman Vedder Ridge Mountain

17 28S 2930755 15068 4720 6470 9950 10725 25E 18 28S 2910932 12563 3812 6610 6909 10052 10771 25E 7 28S 2910930 12628 6829 9440 10004 10699 25E 34 28S 3001226 8100 5190 6630 25E 32 28S 2947999 8200 3336 5566 26E 33 28S 3014351 11130 7885 8688 9689 26E 26 28S 2979500 10184 4025 4460 7800 8520 26E 27 28S 2930769 7543 4403 4930 26E 28 28S 3033663 7846 4755 7690 26E 20 28S 2930760 7001 3284 5567 26E 15 28S 2930761 8515 3086 4206 6315 7299 26E 16 28S 2930768 9100 2967 4664 6572 7505 8618 26E 11 28S 2930773 4300 3376 3680 26E 13 28S 2930764 9498 3386 3683 6318 7513 26E 31 28S 2985041 4900 3512 3787 27E 25 28S 3037484 2593 1696 1880 27E 26 28S 2910282 2415 1857 2050 27E 27 28S 2910611 2590 1954 2161 27E 28 28S 2910453 2899 2483 2755 27E 24 28S 3049469 2085 1626 1809 27E 23 28S 3037795 2252 1685 1873 27E 23 28S 3037480 2820 1785 1975 27E 20 28S 2916575 3492 2750 2990 27E 19 28S 2930787 3964 3210 3580 27E 16 28S 2916486 2950 2250 2505 4590 5650 27E 17 28S 2970225 3600 2650 2940 27E 18 28S 2916411 3756 2980 3255 27E

74

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Maco- Reef Round Etchegoin Monterey Freeman Vedder ma Ridge Mountain

12 28S 2946156 4505 2190 3240 4310 27E 8 28S 2959847 3225 2560 2770 27E 7 28S 2916275 3597 2700 2906 27E 35 28S 2930844 3141 310 1840 3034 28E 36 28S 2983701 4043 180 1740 2885 28E 25 28S 2930836 3168 310 1770 2900 28E 26 28S 2930815 4231 270 1870 3040 28E 27 28S 2924047 3463 900 1160 2510 3126 28E 30 28S 2928038 5998 2060 2300 3460 4605 28E 24 28S 2918193 2250 1210 2208 28E 23 28S 2916913 2891 670 1850 2845 28E 22 28S 2918463 3270 1063 2196 3204 28E 13 28S 2918169 2287 1230 2253 28E 14 28S 2918276 2721 645 1780 2688 28E 15 28S 2918149 2794 800 1960 2775 28E 16 28S 2930824 3385 1440 2380 3314 28E 17 28S 2926738 3762 1700 2800 3750 28E 15 28S 2918445 2928 930 2043 2912 28E 31 28S 2930871 4462 1320 29E 32 28S 2916876 2250 1220 2225 29E 33 28S 2930879 2634 1440 2435 29E 35 28S 2940467 3386 2475 3240 29E 27 28S 2930859 3170 2050 3140 29E 28 28S 2942653 2250 920 1817 29E 21 28S 2930881 2250 1100 1922 29E 20 28S 2969120 2875 1520 2325 29E 16 28S 2972088 2020 990 1602 29E

75

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Round Etchegoin Macoma Monterey Freeman Vedder Ridge Mountain

17 28S 2918375 2117 1490 2055 29E 18 28S 2953853 2235 1140 2038 29E 7 28S 2918313 1655 1120 1955 29E 32 29S 2911407 15006 11569 23E 30 29S 2952494 16005 11450 23E 25 29S 2901176 11948 4718 8850 24E 23 29S 3022259 11498 4600 9200 10400 24E 16 29S 2965169 11495 24E 9 29S 2901177 15396 13890 14490 24E 7 29S 2939158 12989 4570 9950 24E 32 29S 2930904 9766 7750 8500 25E 35 29S 2947429 10025 3188 6407 8801 25E 36 29S 2942011 12723 6470 7400 10970 25E 25 29S 2930892 10300 6490 7380 25E 7960, 26 29S 2930889 10265 6580 7580 9530 25E (lower) 27 29S 2930894 10267 7680 8250 25E 28 29S 2930890 13768 8600 25E 29 29S 2930903 10194 4540 8900 9490 25E 24 29S 3033912 13850 5800 6850 7860 10250 11900 25E 8410, 23 29S 2904265 12733 6400 7300 9570 12010 12635 25E (lower) 21 29S 2930895 10648 8850 25E 20 29S 2930883 10235 4570 8930 9550 25E 13 29S 2908597 11741 6420 7290 8290 9200 10934 11584 25E 14 29S 2946490 12600 6650 7600 12010 12575 25E 17 29S 2930887 10595 4610 9170 9700 25E 18 29S 2930899 14011 9650 13320 13690 25E

76

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Round Etchegoin Macoma Monterey Freeman Vedder Ridge Mountain

12 29S 2908578 11488 6590 7470 8370 9970 11540 25E 8 29S 2930906 10843 9500 10160 25E 1 29S 2908572 11492 6730 7550 8450 9950 11460 25E 2 29S 2916708 11589 25E 3 29S 2968934 12000 4580 7500 8600 9994 10830 11630 25E 4 29S 2969336 12166 4680 8910 25E 31 29S 2930935 12130 6370 7307 10414 11028 11975 26E 32 29S 2966322 13084 6080 6925 7203 10565 11029 12000 26E 33 29S 2904248 9671 5706 6498 6842 26E 34 29S 2965543 11632 5625 6295 6642 10941 26E 35 29S 2966599 11182 4824 5292 5430 9950 26E 36 29S 2985636 12070 4315 4792 5091 9360 10291 26E 26 29S 2930927 8700 5353 5880 6330 26E 27 29S 3000334 9406 5675 6460 6750 26E 28 29S 2930939 11638 6300 6600 9750 10340 26E 29 29S 2930915 9384 6130 6960 7310 26E 30 29S 2972285 11970 7280 7520 9850 10457 11880 26E 23 29S 2916773 10617 4415 4895 9210 9700 26E 22 29S 2930918 11470 5382 6040 6380 9600 10080 26E 21 29S 2908564 11756 6045 6800 7025 10140 11591 26E 20 29S 2908639 11536 6150 6980 7270 9370 9950 11473 26E 19 29S 2908635 11785 7140 7650 9200 26E 14 29S 2916723 10761 4595 5025 8940 9470 26E 15 29S 2916740 7321 5050 5482 26E 16 29S 2908542 8253 6062 6783 7060 26E 17 29S 2908611 11610 6370 7200 7630 9380 10640 26E 18 29S 2908617 11510 6420 7300 7670 9180 10030 26E

77

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Round Etchegoin Macoma Monterey Freeman Vedder Ridge Moun-tain

12 29S 2916777 9200 3840 7790 26E 11 29S 2930912 9788 4210 4660 8080 8900 26E 10 29S 2940003 12705 3050 5240 5740 9700 10495 26E 9 29S 2930936 8620 5605 26E 7 29S 2900728 11510 6370 7158 8063 9102 9900 11285 26E 5 29S 2940837 11725 6125 7084 8748 9368 11056 26E 4 29S 2942802 8250 5374 5947 8096 26E 2 29S 2916850 5020 3897 26E 1 29S 2916839 4810 3694 26E 34 29S 2908312 11570 7800 8750 27E 30 29S 2930950 10866 3960 4350 7250 9920 27E 21 29S 2961380 4623 2870 27E 20 29S 2908493 4959 3500 27E 19 29S 2906729 9772 3640 8660 9594 27E 13 29S 2930978 8252 1750 2670 6925 27E 14 29S 2963414 3592 2380 27E 11 29S 2908438 7719 2847 5850 6870 27E 10 29S 2954448 8082 2896 5950 27E 7 29S 2930968 7133 7140 27E 1 29S 2930973 7014 5820 27E 3 29S 2944869 8350 5620 2860 6725 27E 4 29S 2930952 8670 3165 5900 7170 27E 5 29S 2930979 4500 27E 6 29S 2916782 8522 3620 4110 7330 27E 34 29S 2932002 6717 3930 28E 35 29S 2932020 7890 3790 6450 7620 28E 36 29S 2930983 6444 3210 5080 6208 28E

78

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Round Etchegoin Macoma Monterey Freeman Vedder Ridge Mountain

26 29S 2932005 7009 28E 24 29S 2932021 6163 28E 15 29S 2932009 7124 2256 5710 28E 1 29S 2977088 5300 4360 28E 3 29S 2971358 5140 3079 28E 5 29S 2956263 1375 120 28E 31 29S 2932104 5986 4550 5565 29E 32 29S 2904581 5375 3040 4000 29E 33 29S 2904605 4950 2460 4090 4906 29E 34 29S 2906109 4798 1283 3950 4770 29E 35 29S 2932118 5200 1250 2605 29E 25 29S 2942882 4752 2045 3767 4510 29E 26 29S 2906290 4704 739 4430 4682 29E 27 29S 2906382 4682 990 2270 3910 4750 29E 29 29S 2900812 5889 1668 4000 4920 29E 24 29S 2932133 3510 1100 2720 3410 29E 23 29S 2932055 4005 740 3060 3734 29E 22 29S 2904005 4031 2990 3940 29E 21 29S 2932116 5004 1101 3355 29E 20 29S 2932054 5689 4250 5210 29E 14 29S 2932098 4439 3210 4135 29E 15 29S 2900967 4582 536 4005 29E 16 29S 2904014 4408 280 3252 29E 12 29S 2932092 3578 650 2450 3250 29E 11 29S 2932070 3600 800 2610 29E 10 29S 2949694 4472 3040 4050 29E 9 29S 2932040 4747 2488 29E

79

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Round Etchegoin Macoma Monterey Freeman Vedder Ridge Mountain

8 29S 2947863 3911 2060 3245 29E 7 29S 2956058 5650 780 2480 3742 29E 1 29S 2944053 3167 1782 2730 29E 2 29S 2932062 3060 300 2175 2800 29E 3 29S 2932130 3100 2050 2965 29E 4 29S 2932132 3859 2745 3109 29E 6 29S 2978271 4200 2500 3727 29E 24 30S 2980083 12650 9300 9700 24E 25 30S 2973421 10100 6767 8450 8920 24E 31 30S 2915246 9160 5800 7420 7780 25E 32 30S 2915275 9148 6630 25E 33 30S 2915306 9350 5870 7740 8150 25E 34 30S 2901452 9609 6650 8400 8700 25E 35 30S 2915342 9827 7030 8720 9030 25E 25 30S 2940087 10455 3750 7000 25E 26 30S 2901064 13930 8550 8842 25E 27 30S 2915161 9385 7012 8530 8850 25E 28 30S 2915180 9728 6612 7950 8250 25E 29 30S 2915210 9370 5950 7720 7980 25E 30 30S 2915230 9230 7950 8200 25E 24 30S 2900655 9785 3750 7250 25E 23 30S 2920537 9904 3730 7290 25E 13 30S 2900103 9983 3940 6010 7200 7690 25E 14 30S 2904310 13400 6070 7200 25E 12 30S 2918566 12425 6120 7250 8067 11400 12350 25E 11 30S 2932167 10323 6380 7680 25E 10 30S 3002902 13413 6330 7400 8100 11830 13160 25E

80

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Round Etchegoin Macoma Monterey Freeman Vedder Ridge Mountain

9 30S 2932163 10655 6513 7900 8310 25E 8 30S 2932168 9511 8400 8900 25E 1 30S 2900120 10240 6350 7300 25E 2 30S 2918604 12665 3900 7014 11250 11600 12570 25E 3 30S 2932165 10310 4000 6520 7510 8410 25E 4 30S 2932161 13957 7500 12130 12560 25E 5 30S 2932166 9600 6130 7350 25E 31 30S 2920673 8196 3830 7130 7700 26E 32 30S 2920535 10645 7120 7882 26E 33 30S 2932820 10800 6430 7590 26E 34 30S 2900004 16322 6500 7410 12820 26E 35 30S 2910924 11011 6570 7510 26E 36 30S 2904346 10868 6290 7250 7588 26E 25 30S 2904393 10656 6040 6990 7331 26E 26 30S 2904407 10606 6210 7115 7500 26E 27 30S 2904519 10734 6290 7366 7681 26E 28 30S 2953125 10510 3800 7010 26E 29 30S 2948167 9534 3840 6760 7520 26E 30 30S 2900275 14000 3650 6850 7600 26E 24 30S 2904518 10262 5780 6600 6960 26E 23 30S 2904507 10300 5920 6900 26E 22 30S 2904488 10024 6020 6890 7331 26E 21 30S 2900398 10774 6220 7220 7654 26E 19 30S 2920688 9940 3800 7000 7910 26E 13 30S 3003281 10450 6305 6640 26E 14 30S 2904460 10400 6480 6917 26E 15 30S 2979970 10546 7030 7383 26E

81

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Monte- Round Etchegoin Macoma Freeman Vedder Ridge rey Mountain

15 30S 2904450 10190 6700 7123 26E 16 30S 2900760 10300 6420 7350 7830 26E 18 30S 2944205 13626 6070 7100 7920 11000 11310 12350 26E 10 30S 2956684 10317 5960 6790 7259 26E 9 30S 2918589 10373 6220 7150 7642 26E 8 30S 2918557 10152 7270 7830 26E 7 30S 2918540 9596 3860 6040 7090 26E 6 30S 2918578 9650 5960 7070 8068 26E 5 30S 3006412 9935 6160 7000 7450 26E 3 30S 2972460 11600 5670 6420 6800 10000 10650 26E 33 30S 2932204 12355 5266 7330 11045 27E 36 30S 2977284 12853 7045 7471 12406 27E 25 30S 2932203 11031 7050 7510 8580 27E 30 30S 2932198 10765 6010 6671 7365 27E 23 30S 2974451 11880 6226 6590 7502 10203 27E 22 30S 2970086 11743 5984 6590 7255 10484 27E 21 30S 2976546 11941 5630 6154 7075 10725 27E 20 30S 2973855 12015 5873 6395 7351 11276 27E 19 30S 2904087 10300 5859 6500 6905 27E 13 30S 2932197 7800 5081 5330 27E 14 30S 2972368 13350 5026 5666 6672 9974 27E 15 30S 2932199 13690 5561 6052 6895 9989 12495 27E 17 30S 2932202 10305 5495 5965 6972 27E 7 30S 2932205 8008 5180 5730 5995 27E 5 30S 2932194 12222 4581 4925 5442 11196 27E 6 30S 2980759 11095 4707 5352 6206 10480 27E 25 30S 2963355 12404 9992 10875 28E

82

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Monte- Round Etchegoin Macoma Freeman Vedder Ridge rey Mountain

27 30S 2989352 11041 6951 9220 28E 22 30S 2982030 10500 6361 8290 28E 28 30S 2932234 10874 7227 9940 28E 24 30S 2932231 10509 7554 10439 28E 11 30S 2979382 9758 4289 7386 28E 9 30S 2932247 9645 5050 7532 28E 8 30S 2932227 8604 5579 5210 28E 1 30S 2906002 6700 3220 28E 2 30S 2906367 6037 3771 28E 32 30S 2914346 8688 5200 6640 7410 8215 29E 30 30S 2914639 10510 6080 7700 29E 21 30S 2906447 5509 3500 5153 29E 20 30S 2914451 8107 4790 6060 6903 29E 16 30S 2906314 5378 3374 4500 29E 18 30S 2906183 7450 4270 5960 5810 7250 29E 9 30S 2973115 7000 2000 3300 4270 5163 29E 8 30S 2904652 5942 4840 5775 29E 2 30S 2932260 5810 1133 4200 29E 3 30S 2906131 4699 1510 2900 4070 29E 4 30S 2906077 5278 3560 4090 5025 29E 36 31S 2963490 14890 5605 8980 10258 14890 25E 25 31S 2915786 11084 5800 9320 10350 25E 26 31S 2950170 16455 5900 9436 10467 15032 25E 21 31S 2959597 13780 9250 25E 20 31S 2945524 13600 11103 11650 25E 13 31S 2911297 11043 9450 10100 25E 12 31S 2929411 12823 7801 9030 9530 25E

83

Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Monte- Round Etchegoin Macoma Freeman Vedder Ridge rey Mountain

11 31S 2929396 10192 7430 8800 9300 25E 10 31S 2956928 9750 4430 7970 8470 25E 9 31S 2929373 9958 7920 8480 25E 8 31S 2939272 9359 6945 7950 25E 2 31S 2939291 10050 8910 9250 25E 3 31S 2929346 9889 4860 7250 8670 8950 25E 4 31S 3001480 11213 7700 8270 25E 5 31S 2903276 16176 6650 8210 8640 25E 32 31S 2921672 10558 5780 8150 9060 26E 33 31S 2921677 10833 8410 9330 26E 28 31S 2921656 11441 9090 9850 26E 29 31S 2921665 11110 6150 8520 26E 30 31S 2921667 10811 5850 8270 9330 26E 23 31S 2903687 14945 9180 9950 10410 26E 20 31S 2939857 11713 8500 26E 14 31S 2961295 10551 8340 9050 9550 26E 16 31S 2932355 11500 8830 9600 26E 9 31S 2973377 10400 7680 8812 9252 26E 1 31S 2932356 10499 6807 7720 26E 2 31S 2932350 9484 7300 8300 8650 26E 3 31S 2910925 12517 7170 8360 26E 26 31S 2981162 15399 9000 10260 27E 20 31S 2979059 16025 5710 8100 9130 28E 34 31S 2914251 11711 10540 10810 29E 27 31S 2914464 9526 8160 9260 29E 8 31S 2987345 13800 10700 11400 12400 29E 12 32S 2921643 11213 6890 9600 10130 26E

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Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Monte- Round Etchegoin Macoma Freeman Vedder Ridge rey Mountain

11 32S 2929558 12507 6360 8960 9600 26E 10 32S 2962062 12500 5900 8200 8930 26E 9 32S 2935506 11467 6270 8800 9480 26E 2 32S 2973154 12790 6280 8737 9200 26E 3 32S 2971260 12273 5920 8530 8980 26E 4 32S 2921731 21482 5940 8250 8950 26E 6 32S 2921181 12700 6690 9890 10620 26E 17 32S 2932422 13515 12630 27E 7 32S 2921650 11858 10800 27E 32 32S 2962666 17191 12250 28E 33 32S 2959267 17199 8900 12500 28E 26 32S 2932458 3270 2000 2320 29E 23 32S 2932436 2056 800 1120 29E 32 12N 2959180 14678 8170 10580 22W 33 12N 2959519 13778 8750 11160 22W 34 12N 2959090 13816 8700 11180 11970 22W 36 12 N 2984174 13185 9050 11680 12833 22W 34 12N 2952487 14439 12350 13660 21W 35 12N 29611210 14952 10420 12650 13880 21W 26 12N 2955327 16548 10850 13130 14500 21W 28 12N 2956431 14775 10210 12550 13850 21W 35 12N 2900086 12894 10040 11940 19W 10 11N 2935297 12446 8400 10050 11330 22W 12 11N 2954331 12200 8600 10820 11422 22W 24 11N 2983574 12642 11700 12400 22W 32 11N 2909408 10017 800 1030 3002 22W 6 11N 2986161 11600 7392 9750 10700 22W

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Top of Units or Stratigraphic Markers (ft)

TD Location API (ft) Reef Monte- Round Etchegoin Macoma Freeman Vedder Ridge rey Mountain

4 11N 2954464 16300 8700 9955 10980 22W 7 11N 2979723 10350 7700 8750 9920 22W 20 11N 2985023 14325 12500 14200 21W 15 11N 2915820 14471 10030 12170 13500 21W 5 11N 2915793 13960 11700 12750 21W 3 11N 2915789 12899 9890 12250 21W 9 11N 2915806 12645 9170 11270 12612 21W 12 11N 2986323 16050 11200 13445 15012 21W 30 11N 2978673 12650 9400 11460 21W 29 11N 2913706 13600 10250 12120 21W 15 11N 2932768 16421 4280 5580 6625 7310 8330 20W 32 11N 2979722 11150 9410 20W 34 11N 2976062 13249 8770 9290 20W 35 11N 2932776 12750 3100 6000 20W 25 11N 2920448 9089 20W 21 11N 2973640 7900 3000 6800 7850 19W 29 11N 2920515 8820 6330 7430 19W 27 11N 2932751 7650 2950 5610 6380 19W 20 11N 2920507 12470 3150 7820 19EW 15 11N 2932732 9550 7690 19W

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