Copyright

By

Jefferson Vasconcellos

2016

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

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:

' 'f: . uf~i::;e,~¥& Professor of Geology Committee Chair

Robert Negrini, PhD Professor of Geology

Dirk Baron, PhD Department Chair, Professor of Geology

2

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.

3

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.

4

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

5

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

6

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.

7

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.

8

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.

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

Sierra Nevada

Bakersfield Arch

Los Angeles

Tejon

San Joaquin

Valley

Bakersfield

9

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

10

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).

11

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

12

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).

13

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.

300

600

900

1200

1500

1800

2100

2400

2700

3000

3300

3600

3900

4200

4500

4800

5100

5400

14

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

15

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

16

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

Bakersfield

Los Angeles

17

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.

18

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

Antelope

Fruitvale

Bakersfield

0

18, 035 (5497 m)

FEET

19

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

O Chert

P Chert

20

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).

21

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)

Monterey Fm.

West East

22

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

23

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

24

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

25

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).

26

(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.

27

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)

28

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.

29

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

Edison Area

30

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).

31

(a)

(b)

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).

7 ± 8

degrees

21 ± 8

degrees

24 ±11

degrees

32

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).

33

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

MD

BAR BA

GCV

SNB

TM

34

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).

35

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

36

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

37

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).

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).

Forebulge

38

DATA AND 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.

39

From (top) To (top)

1. Etchegoin Macoma

2. Macoma Reef Ridge

3. Reef Ridge Monterey

4. Monterey Round

Mountain

5. Round

Mountain

Freeman

6. Freeman Vedder

Table 1: Tops used for mapping six sedimentary packages.

Fig. 15: Stratigraphic column of the Southern San Joaquin Valley and sedimentary packages

(Scheirer and Magoon, 2007).

Etchegoin-Macoma Macoma-Reef Ridge

Monterey-Round

Mountain

Round Mountain-

Freeman

Freeman-Vedder

Reef Ridge-Monterey

40

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).

41

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).

Bakersfield

0

18, 035 (5497 m)

FEET

0

1000 (305 m)

2000 (610 m)

3000 (614 m)

4000 (1219 m)

N

42

(a)

A

A`

Bakersfield

N

;

l

;

l

;

l

;

l

;

l

0

18, 035 (5497 m)

FEET

43

(b)

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.

A

A’

0

101

50

(309

4 m)

FEET

29

18

54

0

0 20

0

(61

m)

FEET

Axis o

f

the A

rch

44

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).

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).

Bakersfield

1000 (305 m)

200 (61 m)

N

1900 (579 m)

0

18, 035 (5497 m)

FEET

45

(a)

A`

A

Bakersfield

N

0

18, 035 (5497 m)

FEET

46

(b)

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.

A

A’

0 20

0

(61

m)

FEET 0

101

50

(309

4 m)

FEET

Axis o

f

the A

rch

47

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.

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).

Bakersfield

2000 (610 m)

1000 (305 m)

200 (61 m)

1400

1400

60

0

600

N

0

18, 035 (5497 m)

FEET

48

(a)

A

A`

Bakersfield

N

0

18, 035 (5497 m)

FEET

49

(b)

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.

A

A’

0 20

0

(61

m)

FEET 0

10

150

(30

94 m

)

FEET

Axis o

f

the A

rch

50

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).

51

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).

Bakersfield 0

1000 (309 m)

2000 (610 m)

3000 (914 m)

4000 (1219 m)

1000 1200

1600

2000

4000

4400

N

0

18, 035 (5497 m)

FEET

52

(a)

A

A`

Bakersfield

N

0

18, 035 (5497 m)

FEET

53

(b)

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.

A

A’

0 20

0

(61

m)

FEET 0

10

15

0

(30

94

m)

FEET

Axis o

f

the A

rch

54

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).

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).

Bakersfield

100 (30 m)

1000 (304 m)

2000 (610 m)

3000 (914 m) 940 700

1000

100

280

N

0

18, 035 (5497 m)

FEET

55

(a)

A

A`

Bakersfield

N

0

18, 035 (5497 m)

FEET

56

(b)

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

A

A’

0 20

0

(61

m)

FEET 0

10

15

0

(30

94

m)

FEET

29

06

07

7

Ro

un

d M

ou

ntain

Axis o

f

the A

rch

57

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).

58

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).

Bakersfield 200 (60 m)

1000 (305 m)

2000 (610 m)

1000

800

1000

N

0

18, 035 (5497 m)

FEET

59

(a)

A

A`

Bakersfield

N

0

18, 035 (5497 m)

FEET

60

(b)

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.

A

A’

0 2

00

(61

m)

FEET 0

101

50

(309

4 m)

FEET

Axis o

f

the A

rch

61

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

62

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

63

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

64

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).

65

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

5 km (3mi) 15 km (9mi) 25 km (15mi)

110m (361ft)

105 m (344ft)

100 m (328ft)

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

66

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.

67

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71

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

API Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Maco-

ma

Reef

Ridge Monterey

Round

Mountain Freeman Vedder

2963863 35 27S

23E 17500 5630 10200 14395 14830

2909478 25 27S

23E 14770 4370 7500 9112 14252

2949212 3 27S

23E 15880 12700

2946452 12 27S

23E 16505 8500 9698 11282 12280 13194

2941957 35 27S

24E 15476 4620 7490 7720 11960 12560

2909489 17 27S

24E 13716 4300 7860 12800

2937135 8 27S

24E 13253 7400 8960 12720

2937131 7 27S

24E 13453 7880 8980 12700

2948583 6 27S

24E 15435 4750 8400 9720 12950 13510

2930723 36 27S

26E 6050 2780 2990 5420 5946

2942852 25 27S

26E 5765 2830 3190 5450

2950284 27 27S

26E 7355 3670 4260 5810 6915

2930721 15 27S

26E 7737 3280 3000 4970 5828

2930728 16 27S

26E 7549 4070 5630 6489

2930718 12 27S

26E 7213 2450 4350 5005

2930722 2 27S

26E 6703 2530 4310 4975

2930727 4 27S

26E 7486 3570 5350 6125

2916088 32 27S

27E 3546 2280 2490

2916183 34 27S

27E 4220 3300 3918

2916564 36 27S

27E 3098 2190 3045

2916187 36 27S

27E 3187 1380 2325 3057

2916138 26 27S

27E 3747 1620 2600 3268

2914928 27 27S

27E 3700 1910 2900 3585

2914931 28 27S

27E 4178 1520 1680 3250 3850

2916503 24 27S

27E 4517 1250 2150

72

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin

Macoma Reef

Ridge Monterey

Round

Mountain Freeman Vedder

2916056

20 27S

27E 4219 2150 2280

2916125 13 27S

27E 2935 2190 2850

2914787 15 27S

27E 5540 1360 3150 3780

2914930 17 27S

27E 2364 1880 2010

2952963 12 27S

27E 2713 1150 2010 2685

2914779 10 27S

27E 1429 1295 1429

2916157 7 27S

27E 3046 2170 2500

2914786 9 27S

27E 2513 1500 1855 2400

2914932 1 27S

27E 2876 2105 2665

2916100 2 27S

27E 4656 1020 1700 2500 3160

2916105 4 27S

27E 5205 2100 2960 3540

2914763 4 27S

27E 5084 1770 2100 2950 3515

2914728 6 27S

27E 2808 1900 2210

2912296 31 27S

28E 2765 1780 2508

2912377 32 27S

28E 2201 870 1700 2175

2912378 33 27S

28E 2127 740 1710 2121

2912251 34 27S

28E 2053 400 1450

2912248 35 27S

28E 1403 750 1380

2900006 28 27S

28E 2144 410 1182

3004666 30 27S

28E 3600 870 1720 2437

2912275 22 27S

28E 1539 885 1462

2914070 20 27S

28E 2341 1670 2280

2912479 19 27S

28E 2768 980 1810 2456

2912667 15 27S

28E 1307 780 1285

2954754 15 27S

28E 1878 1210 1706

2914057 18 27S

28E 2565 1150 1880 2468

2912395 11 27S

28E 1183 588 1137

73

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge Monterey

Round

Mountain Freeman Vedder

2954441 10 27S

28E 1808 1180 1690

2957343 9 27S

28E 1977 1020 1876

2912084 8 27S

28E 2337 870 1650 2296

2912013 7 27S

28E 1987 1185 1900

2912225 3 27S

28E 1564 135 900 1327

2912458 4 27S

28E 1954 640 1230 1638

2954644 5 27S

28E 2345 855 1615 2262

2912492 6 27S

28E 1989 1130 1820

2903173 5 28S

23E 13614 4863 10670 12120

2964052 30 28S

23E 16285

3048481 4 28S

23E 12709 5600 11595

2919848 8 28S

23E 12900 10705

2975353 14 28S

23E 13700 5860 9490

2947380 10 28S

23E 20753 5652 10500

2921230 35 28S

24E 11988 4955

2919890 36 28S

24E 10987

2936449 23 28S

24E 7502 3809 6441 8138 10917 12390

2916643 33 28S

R25 11510 7638 8432 9820 10503

2916657 34 28S

25E 11700 7472 8156 10245 11280

2916682 35 28S

25E 11500 8273 9410 10242

2971552 25 28S

25E 11830 7885 10229 11227

2965091 26 28S

25E 12092 9675 10401 11390

2916579 27 28S

25E 11695 8078 9458 10149 11275

2930750 21 28S

25E 11754 6539 10575 11738

2930749 20 28S

25E 12404 4830 6759 11130

2960414 19 28S

25E 13170 9907

2955045 16 28S

25E 13963 5670 9819 10660 11552

74

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge Monterey

Round

Mountain Freeman Vedder

2930755 17 28S

25E 15068 4720 6470 9950 10725

2910932 18 28S

25E 12563 3812 6610 6909 10052 10771

2910930 7 28S

25E 12628 6829 9440 10004 10699

3001226 34 28S

25E 8100 5190 6630

2947999 32 28S

26E 8200 3336 5566

3014351 33 28S

26E 11130 7885 8688 9689

2979500 26 28S

26E 10184 4025 4460 7800 8520

2930769 27 28S

26E 7543 4403 4930

3033663 28 28S

26E 7846 4755 7690

2930760 20 28S

26E 7001 3284 5567

2930761 15 28S

26E 8515 3086 4206 6315 7299

2930768 16 28S

26E 9100 2967 4664 6572 7505 8618

2930773 11 28S

26E 4300 3376 3680

2930764 13 28S

26E 9498 3386 3683 6318 7513

2985041 31 28S

27E 4900 3512 3787

3037484 25 28S

27E 2593 1696 1880

2910282 26 28S

27E 2415 1857 2050

2910611 27 28S

27E 2590 1954 2161

2910453 28 28S

27E 2899 2483 2755

3049469 24 28S

27E 2085 1626 1809

3037795 23 28S

27E 2252 1685 1873

3037480 23 28S

27E 2820 1785 1975

2916575 20 28S

27E 3492 2750 2990

2930787 19 28S

27E 3964 3210 3580

2916486 16 28S

27E 2950 2250 2505 4590 5650

2970225 17 28S

27E 3600 2650 2940

2916411 18 28S

27E 3756 2980 3255

75

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Maco-

ma

Reef

Ridge Monterey

Round

Mountain Freeman Vedder

2946156 12 28S

27E 4505 2190 3240 4310

2959847 8 28S

27E 3225 2560 2770

2916275 7 28S

27E 3597 2700 2906

2930844 35 28S

28E 3141 310 1840 3034

2983701 36 28S

28E 4043 180 1740 2885

2930836 25 28S

28E 3168 310 1770 2900

2930815 26 28S

28E 4231 270 1870 3040

2924047 27 28S

28E 3463 900 1160 2510 3126

2928038 30 28S

28E 5998 2060 2300 3460 4605

2918193 24 28S

28E 2250 1210 2208

2916913 23 28S

28E 2891 670 1850 2845

2918463 22 28S

28E 3270 1063 2196 3204

2918169 13 28S

28E 2287 1230 2253

2918276 14 28S

28E 2721 645 1780 2688

2918149 15 28S

28E 2794 800 1960 2775

2930824 16 28S

28E 3385 1440 2380 3314

2926738 17 28S

28E 3762 1700 2800 3750

2918445 15 28S

28E 2928 930 2043 2912

2930871 31 28S

29E 4462 1320

2916876 32 28S

29E 2250 1220 2225

2930879 33 28S

29E 2634 1440 2435

2940467 35 28S

29E 3386 2475 3240

2930859 27 28S

29E 3170 2050 3140

2942653 28 28S

29E 2250 920 1817

2930881 21 28S

29E 2250 1100 1922

2969120 20 28S

29E 2875 1520 2325

2972088 16 28S

29E 2020 990 1602

76

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge Monterey

Round

Mountain Freeman Vedder

2918375 17 28S

29E 2117 1490 2055

2953853 18 28S

29E 2235 1140 2038

2918313 7 28S

29E 1655 1120 1955

2911407 32 29S

23E 15006 11569

2952494 30 29S

23E 16005 11450

2901176 25 29S

24E 11948 4718 8850

3022259 23 29S

24E 11498 4600 9200 10400

2965169 16 29S

24E 11495

2901177 9 29S

24E 15396 13890 14490

2939158 7 29S

24E 12989 4570 9950

2930904 32 29S

25E 9766 7750 8500

2947429 35 29S

25E 10025 3188 6407 8801

2942011 36 29S

25E 12723 6470 7400 10970

2930892 25 29S

25E 10300 6490 7380

2930889 26 29S

25E 10265 6580 7580

7960,

9530

(lower)

2930894 27 29S

25E 10267 7680 8250

2930890 28 29S

25E 13768 8600

2930903 29 29S

25E 10194 4540 8900 9490

3033912 24 29S

25E 13850 5800 6850 7860 10250 11900

2904265 23 29S

25E 12733 6400 7300

8410,

9570

(lower)

12010 12635

2930895 21 29S

25E 10648 8850

2930883 20 29S

25E 10235 4570 8930 9550

2908597 13 29S

25E 11741 6420 7290 8290 9200 10934 11584

2946490 14 29S

25E 12600 6650 7600 12010 12575

2930887 17 29S

25E 10595 4610 9170 9700

2930899 18 29S

25E 14011 9650 13320 13690

77

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge Monterey

Round

Mountain Freeman Vedder

2908578 12 29S

25E 11488 6590 7470 8370 9970 11540

2930906 8 29S

25E 10843 9500 10160

2908572 1 29S

25E 11492 6730 7550 8450 9950 11460

2916708 2 29S

25E 11589

2968934 3 29S

25E 12000 4580 7500 8600 9994 10830 11630

2969336 4 29S

25E 12166 4680 8910

2930935 31 29S

26E 12130 6370 7307 10414 11028 11975

2966322 32 29S

26E 13084 6080 6925 7203 10565 11029 12000

2904248 33 29S

26E 9671 5706 6498 6842

2965543 34 29S

26E 11632 5625 6295 6642 10941

2966599 35 29S

26E 11182 4824 5292 5430 9950

2985636 36 29S

26E 12070 4315 4792 5091 9360 10291

2930927 26 29S

26E 8700 5353 5880 6330

3000334 27 29S

26E 9406 5675 6460 6750

2930939 28 29S

26E 11638 6300 6600 9750 10340

2930915 29 29S

26E 9384 6130 6960 7310

2972285 30 29S

26E 11970 7280 7520 9850 10457 11880

2916773 23 29S

26E 10617 4415 4895 9210 9700

2930918 22 29S

26E 11470 5382 6040 6380 9600 10080

2908564 21 29S

26E 11756 6045 6800 7025 10140 11591

2908639 20 29S

26E 11536 6150 6980 7270 9370 9950 11473

2908635 19 29S

26E 11785 7140 7650 9200

2916723 14 29S

26E 10761 4595 5025 8940 9470

2916740 15 29S

26E 7321 5050 5482

2908542 16 29S

26E 8253 6062 6783 7060

2908611 17 29S

26E 11610 6370 7200 7630 9380 10640

2908617 18 29S

26E 11510 6420 7300 7670 9180 10030

78

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge Monterey

Round

Moun-tain Freeman Vedder

2916777 12 29S

26E 9200 3840 7790

2930912 11 29S

26E 9788 4210 4660 8080 8900

2940003 10 29S

26E 12705 3050 5240 5740 9700 10495

2930936 9 29S

26E 8620 5605

2900728 7 29S

26E 11510 6370 7158 8063 9102 9900 11285

2940837 5 29S

26E 11725 6125 7084 8748 9368 11056

2942802 4 29S

26E 8250 5374 5947 8096

2916850 2 29S

26E 5020 3897

2916839 1 29S

26E 4810 3694

2908312 34 29S

27E 11570 7800 8750

2930950 30 29S

27E 10866 3960 4350 7250 9920

2961380 21 29S

27E 4623 2870

2908493 20 29S

27E 4959 3500

2906729 19 29S

27E 9772 3640 8660 9594

2930978 13 29S

27E 8252 1750 2670 6925

2963414 14 29S

27E 3592 2380

2908438 11 29S

27E 7719 2847 5850 6870

2954448 10 29S

27E 8082 2896 5950

2930968 7 29S

27E 7133 7140

2930973 1 29S

27E 7014 5820

2944869 3 29S

27E 8350 5620 2860 6725

2930952 4 29S

27E 8670 3165 5900 7170

2930979 5 29S

27E 4500

2916782 6 29S

27E 8522 3620 4110 7330

2932002 34 29S

28E 6717 3930

2932020 35 29S

28E 7890 3790 6450 7620

2930983 36 29S

28E 6444 3210 5080 6208

79

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge Monterey

Round

Mountain Freeman Vedder

2932005 26 29S

28E 7009

2932021 24 29S

28E 6163

2932009 15 29S

28E 7124 2256 5710

2977088 1 29S

28E 5300 4360

2971358 3 29S

28E 5140 3079

2956263 5 29S

28E 1375 120

2932104 31 29S

29E 5986 4550 5565

2904581 32 29S

29E 5375 3040 4000

2904605 33 29S

29E 4950 2460 4090 4906

2906109 34 29S

29E 4798 1283 3950 4770

2932118 35 29S

29E 5200 1250 2605

2942882 25 29S

29E 4752 2045 3767 4510

2906290 26 29S

29E 4704 739 4430 4682

2906382 27 29S

29E 4682 990 2270 3910 4750

2900812 29 29S

29E 5889 1668 4000 4920

2932133 24 29S

29E 3510 1100 2720 3410

2932055 23 29S

29E 4005 740 3060 3734

2904005 22 29S

29E 4031 2990 3940

2932116 21 29S

29E 5004 1101 3355

2932054 20 29S

29E 5689 4250 5210

2932098 14 29S

29E 4439 3210 4135

2900967 15 29S

29E 4582 536 4005

2904014 16 29S

29E 4408 280 3252

2932092 12 29S

29E 3578 650 2450 3250

2932070 11 29S

29E 3600 800 2610

2949694 10 29S

29E 4472 3040 4050

2932040 9 29S

29E 4747 2488

80

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge Monterey

Round

Mountain Freeman Vedder

2947863 8 29S

29E 3911 2060 3245

2956058 7 29S

29E 5650 780 2480 3742

2944053 1 29S

29E 3167 1782 2730

2932062 2 29S

29E 3060 300 2175 2800

2932130 3 29S

29E 3100 2050 2965

2932132 4 29S

29E 3859 2745 3109

2978271 6 29S

29E 4200 2500 3727

2980083 24 30S

24E 12650 9300 9700

2973421 25 30S

24E 10100 6767 8450 8920

2915246 31 30S

25E 9160 5800 7420 7780

2915275 32 30S

25E 9148 6630

2915306 33 30S

25E 9350 5870 7740 8150

2901452 34 30S

25E 9609 6650 8400 8700

2915342 35 30S

25E 9827 7030 8720 9030

2940087 25 30S

25E 10455 3750 7000

2901064 26 30S

25E 13930 8550 8842

2915161 27 30S

25E 9385 7012 8530 8850

2915180 28 30S

25E 9728 6612 7950 8250

2915210 29 30S

25E 9370 5950 7720 7980

2915230 30 30S

25E 9230 7950 8200

2900655 24 30S

25E 9785 3750 7250

2920537 23 30S

25E 9904 3730 7290

2900103 13 30S

25E 9983 3940 6010 7200 7690

2904310 14 30S

25E 13400 6070 7200

2918566 12 30S

25E 12425 6120 7250 8067 11400 12350

2932167 11 30S

25E 10323 6380 7680

3002902 10 30S

25E 13413 6330 7400 8100 11830 13160

81

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge Monterey

Round

Mountain Freeman Vedder

2932163 9 30S

25E 10655 6513 7900 8310

2932168 8 30S

25E 9511 8400 8900

2900120 1 30S

25E 10240 6350 7300

2918604 2 30S

25E 12665 3900 7014 11250 11600 12570

2932165 3 30S

25E 10310 4000 6520 7510 8410

2932161 4 30S

25E 13957 7500 12130 12560

2932166 5 30S

25E 9600 6130 7350

2920673 31 30S

26E 8196 3830 7130 7700

2920535 32 30S

26E 10645 7120 7882

2932820 33 30S

26E 10800 6430 7590

2900004 34 30S

26E 16322 6500 7410 12820

2910924 35 30S

26E 11011 6570 7510

2904346 36 30S

26E 10868 6290 7250 7588

2904393 25 30S

26E 10656 6040 6990 7331

2904407 26 30S

26E 10606 6210 7115 7500

2904519 27 30S

26E 10734 6290 7366 7681

2953125 28 30S

26E 10510 3800 7010

2948167 29 30S

26E 9534 3840 6760 7520

2900275 30 30S

26E 14000 3650 6850 7600

2904518 24 30S

26E 10262 5780 6600 6960

2904507 23 30S

26E 10300 5920 6900

2904488 22 30S

26E 10024 6020 6890 7331

2900398 21 30S

26E 10774 6220 7220 7654

2920688 19 30S

26E 9940 3800 7000 7910

3003281 13 30S

26E 10450 6305 6640

2904460 14 30S

26E 10400 6480 6917

2979970 15 30S

26E 10546 7030 7383

82

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge

Monte-

rey

Round

Mountain Freeman Vedder

2904450 15 30S

26E 10190 6700 7123

2900760 16 30S

26E 10300 6420 7350 7830

2944205 18 30S

26E 13626 6070 7100 7920 11000 11310 12350

2956684 10 30S

26E 10317 5960 6790 7259

2918589 9 30S

26E 10373 6220 7150 7642

2918557 8 30S

26E 10152 7270 7830

2918540 7 30S

26E 9596 3860 6040 7090

2918578 6 30S

26E 9650 5960 7070 8068

3006412 5 30S

26E 9935 6160 7000 7450

2972460 3 30S

26E 11600 5670 6420 6800 10000 10650

2932204 33 30S

27E 12355 5266 7330 11045

2977284 36 30S

27E 12853 7045 7471 12406

2932203 25 30S

27E 11031 7050 7510 8580

2932198 30 30S

27E 10765 6010 6671 7365

2974451 23 30S

27E 11880 6226 6590 7502 10203

2970086 22 30S

27E 11743 5984 6590 7255 10484

2976546 21 30S

27E 11941 5630 6154 7075 10725

2973855 20 30S

27E 12015 5873 6395 7351 11276

2904087 19 30S

27E 10300 5859 6500 6905

2932197 13 30S

27E 7800 5081 5330

2972368 14 30S

27E 13350 5026 5666 6672 9974

2932199 15 30S

27E 13690 5561 6052 6895 9989 12495

2932202 17 30S

27E 10305 5495 5965 6972

2932205 7 30S

27E 8008 5180 5730 5995

2932194 5 30S

27E 12222 4581 4925 5442 11196

2980759 6 30S

27E 11095 4707 5352 6206 10480

2963355 25 30S

28E 12404 9992 10875

83

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge

Monte-

rey

Round

Mountain Freeman Vedder

2989352 27 30S

28E 11041 6951 9220

2982030 22 30S

28E 10500 6361 8290

2932234 28 30S

28E 10874 7227 9940

2932231 24 30S

28E 10509 7554 10439

2979382 11 30S

28E 9758 4289 7386

2932247 9 30S

28E 9645 5050 7532

2932227 8 30S

28E 8604 5579 5210

2906002 1 30S

28E 6700 3220

2906367 2 30S

28E 6037 3771

2914346 32 30S

29E 8688 5200 6640 7410 8215

2914639 30 30S

29E 10510 6080 7700

2906447 21 30S

29E 5509 3500 5153

2914451 20 30S

29E 8107 4790 6060 6903

2906314 16 30S

29E 5378 3374 4500

2906183 18 30S

29E 7450 4270 5960 5810 7250

2973115 9 30S

29E 7000 2000 3300 4270 5163

2904652 8 30S

29E 5942 4840 5775

2932260 2 30S

29E 5810 1133 4200

2906131 3 30S

29E 4699 1510 2900 4070

2906077 4 30S

29E 5278 3560 4090 5025

2963490 36 31S

25E 14890 5605 8980 10258 14890

2915786 25 31S

25E 11084 5800 9320 10350

2950170 26 31S

25E 16455 5900 9436 10467 15032

2959597 21 31S

25E 13780 9250

2945524 20 31S

25E 13600 11103 11650

2911297 13 31S

25E 11043 9450 10100

2929411 12 31S

25E 12823 7801 9030 9530

84

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge

Monte-

rey

Round

Mountain Freeman Vedder

2929396 11 31S

25E 10192 7430 8800 9300

2956928 10 31S

25E 9750 4430 7970 8470

2929373 9 31S

25E 9958 7920 8480

2939272 8 31S

25E 9359 6945 7950

2939291 2 31S

25E 10050 8910 9250

2929346 3 31S

25E 9889 4860 7250 8670 8950

3001480 4 31S

25E 11213 7700 8270

2903276 5 31S

25E 16176 6650 8210 8640

2921672 32 31S

26E 10558 5780 8150 9060

2921677 33 31S

26E 10833 8410 9330

2921656 28 31S

26E 11441 9090 9850

2921665 29 31S

26E 11110 6150 8520

2921667 30 31S

26E 10811 5850 8270 9330

2903687 23 31S

26E 14945 9180 9950 10410

2939857 20 31S

26E 11713 8500

2961295 14 31S

26E 10551 8340 9050 9550

2932355 16 31S

26E 11500 8830 9600

2973377 9 31S

26E 10400 7680 8812 9252

2932356 1 31S

26E 10499 6807 7720

2932350 2 31S

26E 9484 7300 8300 8650

2910925 3 31S

26E 12517 7170 8360

2981162 26 31S

27E 15399 9000 10260

2979059 20 31S

28E 16025 5710 8100 9130

2914251 34 31S

29E 11711 10540 10810

2914464 27 31S

29E 9526 8160 9260

2987345 8 31S

29E 13800 10700 11400 12400

2921643 12 32S

26E 11213 6890 9600 10130

85

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge

Monte-

rey

Round

Mountain Freeman Vedder

2929558 11 32S

26E 12507 6360 8960 9600

2962062 10 32S

26E 12500 5900 8200 8930

2935506 9 32S

26E 11467 6270 8800 9480

2973154 2 32S

26E 12790 6280 8737 9200

2971260 3 32S

26E 12273 5920 8530 8980

2921731 4 32S

26E 21482 5940 8250 8950

2921181 6 32S

26E 12700 6690 9890 10620

2932422 17 32S

27E 13515 12630

2921650 7 32S

27E 11858 10800

2962666 32 32S

28E 17191 12250

2959267 33 32S

28E 17199 8900 12500

2932458 26 32S

29E 3270 2000 2320

2932436 23 32S

29E 2056 800 1120

2959180 32 12N

22W 14678 8170 10580

2959519 33 12N

22W 13778 8750 11160

2959090 34 12N

22W 13816 8700 11180 11970

2984174 36 12 N

22W 13185 9050 11680 12833

2952487 34 12N

21W 14439 12350 13660

29611210 35 12N

21W 14952 10420 12650 13880

2955327 26 12N

21W 16548 10850 13130 14500

2956431 28 12N

21W 14775 10210 12550 13850

2900086 35 12N

19W 12894 10040 11940

2935297 10 11N

22W 12446 8400 10050 11330

2954331 12 11N

22W 12200 8600 10820 11422

2983574 24 11N

22W 12642 11700 12400

2909408 32 11N

22W 10017 800 1030 3002

2986161 6 11N

22W 11600 7392 9750 10700

86

API

Location TD

(ft)

Top of Units or Stratigraphic Markers (ft)

Etchegoin Macoma Reef

Ridge

Monte-

rey

Round

Mountain Freeman Vedder

2954464 4 11N

22W 16300 8700 9955 10980

2979723 7 11N

22W 10350 7700 8750 9920

2985023 20 11N

21W 14325 12500 14200

2915820 15 11N

21W 14471 10030 12170 13500

2915793 5 11N

21W 13960 11700 12750

2915789 3 11N

21W 12899 9890 12250

2915806 9 11N

21W 12645 9170 11270 12612

2986323 12 11N

21W 16050 11200 13445 15012

2978673 30 11N

21W 12650 9400 11460

2913706 29 11N

21W 13600 10250 12120

2932768 15 11N

20W 16421 4280 5580 6625 7310 8330

2979722 32 11N

20W 11150 9410

2976062 34 11N

20W 13249 8770 9290

2932776 35 11N

20W 12750 3100 6000

2920448 25 11N

20W 9089

2973640 21 11N

19W 7900 3000 6800 7850

2920515 29 11N

19W 8820 6330 7430

2932751 27 11N

19W 7650 2950 5610 6380

2920507 20 11N

19EW 12470 3150 7820

2932732 15 11N

19W 9550 7690