THE TEHAMA FORMATION at BLACK BUTTE LAKE with a REVIEW of the GEOLOGY of the ORLAND BUTTES ___A Thesis Presented to T

Home , Atlantic (period), Black Butte (Oregon), Black Butte Lake, Early Pleistocene

THE TEHAMA FORMATION AT BLACK BUTTE LAKE WITH A REVIEW OF THE GEOLOGY OF THE ORLAND BUTTES

______

A Thesis Presented To the Faculty of California State University, Chico

______

In Partial Fulfillment Of The Requirements for the Degree Master of Science In Geosciences

______

By David F. Maloney

Summer 2017 THE TEHAMA FORMATION AT BLACK BUTTE LAKE WITH A REVIEW OF THE GEOLOGY OF THE ORLAND BUTTES

A Thesis By David F. Maloney Summer 2017

APPROVED BY THE INTERIM DEAN OF GRADUATE STUDIES

______Sharon A. Barrios, Ph.D.

APPROVED BY THE GRADUATE ADVISORY COMMITTEE:

______Russell Shapiro, Ph.D., Chair

______Ann Bykerk-Kauffman, Ph.D.

______Todd Greene, Ph.D.

ACKNOWLEDGEMENTS

For many years I have walked the shoreline of Black Butte Lake and wondered about the geology of the area. On more than one occasion I thought that somebody needs to describe this area because it is not what people think it is. After many years of working in the northern San Joaquin Valley, I returned to northern California and was the person who was able to re-evaluate the geology at the lake. Hopefully this thesis will clear up questions that others have concerning the geology of the area.

I would like to thank everybody at CSU Chico for the help and support that you have given me. Thank you Dr Shapiro for accepting me as a graduate student and giving me the opportunity to complete this research. Thanks also for your guidance in the development of this thesis. Thank you Dr. Kauffman for your support and for giving me the opportunity to come back to CSUC and further my education. Thank you Dr.

Kauffman and Dr. Greene for your help and guidance in writing this thesis. Thanks also for all of the help with formatting and terminology.

I would not have been able to complete this thesis without the help and support of the people at Black Butte Lake. Thanks to all of you for the opportunity to conduct research at the lake. I hope to work with you in the future.

iii

TABLE OF CONTENTS

CHAPTER PAGE

Acknowlegements ...... iii

List of Tables ...... vi

List of Figures ...... vii

Abstract ...... ix

CHAPTER I. Introduction and Geologic History...... 1 Introduction ...... 1 Geologic History of the Study Area ...... 3

II. Geologic Setting and Stratigraphic Units ...... 9 Stratigraphic Units ...... 9 Present Model of the Geology of the Study Area...... 25 Location of the Study Area ...... 27 Methods and Sources of Data ...... 29

III. Results of field Surveys ...... 33 Description of the Stratigraphic Units in the Study Area ...... 33 Composite Stratigraphic Section ...... 56 Clast Composition Surveys ...... 56

IV. Subsurface Distribution of Stratigraphic Units ...... 67 Introduction ...... 67 Geologic Cross Sections ...... 67

V. Discussion of Results ...... 72

CHAPTER PAGE

References ...... 86

Appendices A. Pie Charts ...... 96 B. Geologic Map of the Study Area ...... 99

LIST OF TABLES

TABLE PAGE

1. Table of Clast Composition Survey/Pebble Count Locations ...... 61 2. Table of Clast Composition Survey/Pebble Count Results ...... 62

LIST OF FIGURES

FIGURE PAGE

1. Regional Map of the Northern Sacramento Valley ...... 5 2. Extent of the Tehama Formation in the Sacramento Valley ...... 20 3. Geologic Map of the Study Area and Surrounding Region...... 26 4. Regional Map of the Northern Sacramento Valley and the Study Area ...... 28 5. Map of the Study Area at Black Butte Lake ...... 29 6. Map of the Study Area Showing the Location of Geologic Features ...... 34 7. Black Butte Formation Sediments on the South Side of North Butte ...... 38 8. Claystone Facies of the Tehama Formation ...... 41 9. Conglomerate Facies of the Tehama Formation ...... 42 10. Measured Stratigraphic Section of the Rocks of the Tehama Formation ...... 44 11. Lovejoy Basalt Clasts in Tehama Formation Claystone ...... 45 12. View of Red Bluff Pediment and Eroded Region North of the Study Area ...... 48 13. Lower Riverbank Formation Alluvium ...... 49 14. Lower Riverbank Formation Terrace Deposit over Tehama Formation Claystone ...... 51

vii

FIGURE PAGE

15. Upper Riverbank Formation Conglomerate ...... 54 16. Composite Section of the Stratigraphic Units Observed

in the Study Area ...... 57 17. Map of the Study Area Showing Location of Clast Composition Surveys/Pebble Counts ...... 59 18. Pie Charts of the Relative Composition of the Clasts in the Lithologic Units...... 61 19. Map of the Study Area Showing the Location of Cross Sections ...... 68 20. Cross Sections Compiled from Field Surveys ...... 71 21. Buttress Unconformity in the Tehama Formation ...... 76 22. Map of the Extent of the Red Bluff Pediment ...... 79

viii

ABSTRACT

THE TEHAMA FORMATION AT BLACK BUTTE LAKE WITH A REVIEW OF THE GEOLOGY OF THE ORLAND BUTTES

David F. Maloney Master of Science in Geosciences California State University, Chico Summer 2017

Field surveys at Black Butte Lake in western Glenn and Tehama counties and a synthesis of the published literature of the Geology of the northern Sacramento Valley and have led to a revision of the stratigraphy and structure of the western side of the northern Sacramento Valley.

The Orland Buttes are a series of flat topped mesas that bound Black Butte Lake on the east. The Buttes are composed of Upper Cretaceous marine rocks of the Great

Valley Group, overlain by Oligocene to Miocene alluvium and capped by the middle

Miocene (15.4Ma) Lovejoy Basalt. Alluvium of the Pliocene Tehama Formation and

Pleistocene Riverbank Formation butt unconformably against the side of the Orland

Buttes.

Prior geologic maps show the Black Butte fault on the western slope of the Orland

Buttes. This fault was proposed by Russell (1931) to explain the uplift of the buttes in

relation to the surrounding Tehama Formation and was proposed as a source for the

basalt that caps the Orland Buttes. The Basalt has subsequently been identified as a

western exposure of the Lovejoy Basalt. The Orland Buttes are a series of Table

Mountains similar to Oroville Table Mountain. There is no evidence to support the

existence of the Black Butte fault.

Oligocene to Miocene alluvium below the Lovejoy Basalt was not recognized in early surveys of the region. This alluvium is present on the north slope of North Butte where it was previously identified as the Tehama Formation. The alluvium was identified below the Lovejoy Basalt during construction of Black Butte Dam (US Army

Corps of Engineers Foundation Report, 1963) and was informally named the Black Butte formation. Detailed descriptions of the lithology of the unit are available (US Army

Corps of Engineers Foundation Report, 1963; Hancock et al., 1986). Lithologic descriptions compiled during field surveys reveal that the Black Butte formation is green to tan claystone interbedded with gravel and cobble conglomerate at the base of the unit.

The fine-grained sediments are arkosic, the coarse-grained sediments contain clasts from the Sierra Nevada or Klamath Mountains. Previous researchers have correlated the Black

Butte formation with other recognized units, but it is Oligocene to Miocene age and is a new lithologic unit.

The Tehama Formation is an extensive deposit of Pliocene (3.27Ma) alluvium that is the primary aquifer on the west side of the Sacramento Valley. The Tehama

Formation underlies both the Pleistocene Red Bluff Formation gravels and Riverbank

Formation alluvium. North of Stony Creek the Tehama Formation is present in stream beds and below the elevation of the high water level along the shoreline of Black Butte

Lake. South of Stony Creek the Tehama Formation is present in wave cut cliffs along the southern shoreline of the lake. On the eastern shoreline of the lake the Tehama

Formation is present as perched terraces on the western slope of Middle Butte and North

Butte.

Detailed geologic mapping reveals that north and west of the Orland Buttes the surface exposures of the Tehama Formation are not as extensive as shown on prior geologic maps. Geologic maps produced by Russell (1931) depict exposures of the

Tehama Formation north and west of the Orland Buttes, but he also explained in his PhD. dissertation that there was insufficient time to differentiate between the Tehama

Formation and the overlying Red Bluff Formation in his maps of the region. This study verified that there are large areas west of the Orland Buttes that are covered by red iron oxide stained alluvium that are not shown on Russell’s geologic maps, or maps produced by subsequent researchers. This alluvium covers large parts of the study area and overlies the Tehama Formation along the lake shore and the Cretaceous rocks of the Great Valley

Group west of the study area.

No exposures of the Red Bluff Formation gravels were seen in the study area or west of The Orland Buttes. Two units of red, iron oxide stained alluvium are presently mapped in the study area. The Red Bluff Formation is a deposit of early Pleistocene sand and gravel which covers the Red Bluff Pediment. The Riverbank Formation is middle

Pleistocene alluvium which occurs as terrace deposits along modern streams and alluvial fans on the floor of the Sacramento Valley. The red gravels north and west of the Orland

Buttes are not a deposit of coarse grained alluvium of the Tehama Formation, nor are they Red Bluff Formation gravels. This study shows that the Iron-oxide stained alluvium north and west of the Orland Buttes is a fill terrace that was deposited into stream valleys that were eroded into the uplifted Red Bluff Pediment and the underlying Tehama

Formation during the middle Pleistocene. This alluvium is middle Pleistocene, and should be re-assigned to the Riverbank Formation.

These new interpretations of the stratigraphy in the study area will affect our understanding of the geology of the western side of the Sacramento Valley and the hydrologic properties of the Tehama Formation aquifer. This report demonstrates that large areas previously mapped as fine grained alluvium of the Tehama Formation actually consist of coarse grained sediments of the Pleistocene Riverbank Formation. The new interpretation of the geology and the differences in porosity and permeability of the rocks in the two geologic units may affect our understanding of the hydrologic properties of the aquifer. Many researchers extended faults into the study area as a result of Russel’s interpretation of the Black Butte fault. The Black Butte fault does not exist west of the

Orland Buttes, the present interpretation of structural features in the northern Sacramento

Valley will need to be re-evaluated.

xii

CHAPTER I

INTRODUCTION AND GEOLOGIC HISTORY

Introduction

Depletion of groundwater supplies continues as demand on groundwater

resources increases. Population growth and a changing environment are affecting our

ability to provide water for domestic use, agriculture, and natural resource conservation.

Long term environmental change and periodic drought raise concerns that the present

sources of fresh water are inadequate to meet future needs. It is important to thoroughly

understand the local and regional groundwater conditions in the management of water

supplies in the Sacramento Valley. A re-evaluation of the stratigraphy and geologic

structure of the western side of the northern Sacramento Valley will provide for more

accurate prediction of water resources.

In the northern Sacramento Valley the two aquifers that supply most of the

groundwater are found in sedimentary rocks of the Tuscan Formation and the Tehama

Formation (Olmsted and Davis, 1961). These stratigraphic units are composed primarily of terrestrial sediment that was deposited on the floor of the Sacramento Valley during the Pliocene. The Tehama Formation is the principal water-bearing geologic unit on the west side of the northern Sacramento Valley.

One of the main factors that determine the properties of groundwater aquifers is the geology of the aquifer and the surrounding region. The storativity and the hydraulic conductivity of an aquifer are determined by a combination of factors including the sedimentary parameters of porosity and permeability as well as the structural features that control the shape and subsurface extent of the aquifer. An accurate understanding of the geologic units in the region and the geographic extent of these units is necessary to predict the properties of the aquifer.

The forces affecting the geological structure of the western Sacramento Valley have been re-interpreted based on modern theories of plate tectonics. This new interpretation has altered our understanding of the forces affecting the uplift of the Coast

Ranges and deformation of the rocks of the Great Valley Group in response to the northward migration of the Mendocino Triple Junction (Dickinson and Snyder, 1979;

Harwood and Helley, 1987; Locke et al., 2006). Structural features on the west side of the Sacramento Valley need to be re-evaluated in light of these theories. Recent seismic reflection studies have provided detailed information resulting in a more accurate interpretation of the stratigraphy of the geological units and geologic structures underlying the Sacramento Valley (Costenius et al., 2000; McManus et al., 2014). An accurate understanding of the age and location of the structural features in the region is necessary to interpret the shape and extent of the deposits of the Paleogene and Neogene sedimentary rocks.

Geologic History of the Study Area

The study area has a complex geologic history dating back to the Mesozoic

period. The Mesozoic rocks of the western Sacramento Valley were are composed of

sediments that were deposited in a forearc basin that existed between the ancestral Sierra

Nevada Mountains to the east and a subduction zone to the west (Dickinson, 1970;

Dickinson and Rich, 1972; Ingersoll, 1978; and Dickinson and Seely, 1979). The

Mesozoic age rocks in the study area are composed of sandstone and shale with rare limestone (Kirby, 1943; Dickinson and Rich, 1972; Ingersoll, 1978). These sedimentary

rocks have been described as turbidites that were deposited on submarine fans in a deep

marine environment (Ingersoll, 1977).

The Coast Range Fault is a dominant structural feature on the western border

of the Sacramento Valley (Bailey et al., 1964; Jayko et al., 1987; see figure 1). The

Coast Range Fault has been interpreted as a both a thrust fault “Coast Range Thrust” and

as a normal fault. The Coast Range Fault represents a Mesozoic age subduction zone and

emplaces Jurassic and Cretaceous rocks of the Franciscan Complex and the Coast Range

Ophiolite against continental slope and deep marine deposits of The Great Valley Group,

(Bailey et al., 1964). Constenius et al. (2000) described The Coast Range Fault as a

normal fault that was formed by extension in the Late Jurassic and Early Cretaceous.

Constenius et al. (2000) described Early Cretaceous extension to the north which resulted

in normal faulting and displacement of the rocks of the Great Valley Group on the

Paskenta Fault, the Cold Fork Fault, and the Elder Creek Fault. The Salt Lake Fault and

the Cold Fork Fault Zone separate two lithostratigraphic units in the rocks of the Great

Valley Group (Brown and Rich, 1961; Blake et al., 1992). The Salt Lake Fault was

mapped south of the study area in the Lodoga Quadrangle (Brown and Rich, 1961; see

figure 1). The Salt Lake Fault was interpreted as a low angle thrust fault with east side up motion (Brown and Rich, 1961; Blake et al, 1992). The Cold Fork Fault Zone was mapped north of the study area (Jones and Irwin, 1971; Harwood and Helley, 1987;

Blake et al., 1992; see figure 1).

The Williams Submarine Canyon was incised and then filled during the Late

Cretaceous (Williams et al., 1998; see figure 1). The Mesozoic rocks of the Great Valley

Group have been tilted and folded on the western border of the Sacramento Valley as a

result of uplift in the Coast Ranges. Uplift in the Coast Ranges began during the

Paleocene (Unruh, 1991) and possibly as early as the middle to Late Cretaceous (Unruh,

1995). The age of formation of the Sites Anticline and the Fruto Syncline (see figure 1),

has been described from the Late Cretaceous to Eocene (Chuber, 1961; Williams et al.,

1998; Unruh, 2004).

During the Paleogene period, marine conditions were dominant in the

Sacramento Valley. Four Paleogene submarine canyons have been described in the

Sacramento Valley (Redwine, 1972). Three of these submarine canyons (the Martinez

Submarine canyon, the Meganos Submarine Canyon, and Markley Gorge) occur south

and west of the study area. The early Eocene lower Princeton Valley was described east

of the study area in the northern Sacramento Valley with the Capay Formation as the fill

in the lower Princeton Valley (Redwine, 1972).

Figure 1. Regional map of the northern Sacramento Valley. Regional map of the northern Sacramento Valley with locations and features noted in this thesis.

During the Neogene period terrestrial conditions were dominant in the

northern Sacramento Valley. Oligocene to early Miocene sedimentary rocks in the

study area are deposits of alluvium that occur below the Lovejoy Basalt at the Orland

Buttes. The age and origin of these sedimentary deposits are still uncertain. The

sediments have been interpreted as the upper Eocene Nord Formation (Van den Berge,

1968), the Eocene Markley Sandstone (Redwine, 1972), an un-named nonmarine unit

(Harding et al., 1960) and informally, the Black Butte formation in the study area (US

Army Corps of Engineers Foundation Report, 1963). The Lovejoy Basalt flowed from

the east across the ancestral Sacramento Valley during the middle Miocene (Page et

al., 1995; Garrison et al., 2008; and Busby and Wagner, 2004). The Lovejoy Basalt

followed river channels across the valley and in some areas filled the region

surrounding these paleo channels (Durell, 1959). Outcrops of the Lovejoy Basalt are

exposed 10 miles south of the study area (Stefanov, 1962; see figure 1), and as far

south as Lake Berryessa and Vacaville (Weaver, 1949).

The upper Princeton Valley was formed as the Lovejoy Basalt and underlying

stratigraphic units were eroded during the middle to late Miocene (Redwine, 1972). The

Lovejoy Basalt forms the rim rock for the upper Princeton Valley and large slump blocks of Lovejoy Basalt are common at the base of the upper Princeton Valley fill (Redwine,

1972). The upper Princeton Valley fill is a deposit of clay, sand, and gravel. Clasts in the coarser facies consist primarily of andesitic rocks, the clay and sand facies have been described as greenish-grey and sometimes locally dark grey to black when in the vicinity of the Lovejoy Basalt (Redwine, 1972). Redwine (1972) thought that the upper Princeton

Valley was incised and filled during the Oligocene period, and that the upper Princeton

Valley fill was likely coeval with the Valley Springs Formation. This interpretation was based on two factors; an Eocene age of the Lovejoy Basalt based on stratigraphic relationships (Durrell, 1959), and andesitic clasts in the sediments of the upper Princeton

Valley fill are similar to the Valley Springs Formation. However, the age of the Lovejoy

Basalt has subsequently been determined to be middle Miocene (Page et al., 1995;

Garrison et al., 2008; Busby and Wagner, 2004). The upper Princeton Valley fill occurs in a stratigraphic position above the Lovejoy Basalt; therefore the upper Princeton Valley fill must be at the oldest middle Miocene in age. A brief marine transgression occurred in the late Miocene resulting in deposition of the Neroly Formation south of the study area, followed by a final regression at the end of the Miocene (Redwine, 1972).

Uplift of the Coast Ranges resumed in the Pliocene (Taliferro, 1951, Harwood and Helley, 1987; Locke et al., 2006). The clay, silt, sand, and gravel of the Tehama

Formation were deposited during this period of uplift. Tehama Formation sediments are

present on the western side of the Sacramento Valley from Redding to Vacaville

(Anderson and Russell, 1939). On the eastern side of the northern Sacramento Valley,

the Tuscan Formation was deposited at the same time as the Tehama Formation (Diller,

1894; and Russell, 1931; see figure 2). The two formations interfinger near the center of

the Sacramento Valley (Russell, 1931; Marchand and Allwardt, 1981; McManus et al.,

2014). The Pliocene Laguna Formation was deposited on the east side of the southern

Sacramento Valley and the northern San Joaquin Valley at this time (Piper et all., 1939).

The Nomlaki Tuff is present near the base of The Tehama, Tuscan and Laguna

formations (Russell, 1931; Marchand and Allwardt, 1981; Busacca, 1989). The age of

the Nomlaki Tuff was determined by K/Ar dating at 3.27 Ma (Knott and Sarna-Wojcicki,

2001).

Uplift of the Coast Ranges and Sierra Nevada Mountains in the early

Pleistocene resulted in the formation of a regional pediment on the floor of the

Sacramento Valley. The pediment and associated sedimentary deposits were named the

“Red Lands” by Bryan (1923). The Red Lands extend from Redding south to the

Montezuma Hills on the west side of the Sacramento Valley and on the east side of the

Sacramento Valley to the Mokelumne River in the San Joaquin Valley. In northern

California this pediment is called the Red Bluff Pediment. The Red Bluff Pediment was formed approximately 0.5 to 1 Ma (Helley and Jaworoski, 1985). The alluvium that was deposited during formation of the pediment was named the Red Bluff Gravels (Diller,

1894). The Riverbank and Modesto formations were deposited as alluvial fans along the edges of the Sacramento Valley as uplift on both sides of the Sacramento Valley continued from the middle Pleistocene to Holocene (Steele, 1980; Marchand and

Allwardt, 1981; Helley and Harwood, 1985). In addition, east-west compression in the middle to late Pleistocene, formed the Corning Domes, the Corning Fault, and other structures below the valley floor (Helley and Harwood, 1985; Helley and Jaworoski,

1985).

CHAPTER II

GEOLOGIC SETTING AND STRATIGRAPHIC UNITS

Stratigraphic Units

The Franciscan Complex

A large portion of the Coast Ranges are composed of rocks of the Franciscan

Complex (Bailey et al., 1959). The Franciscan complex is composed of sandstone and

shale with minor amounts of conglomerate, chert, and limestone (Bailey et al., 1959).

The Mesozoic and Cenozoic rocks of the Franciscan Complex have been subdivided into

three informal units: the Eastern Belt, the Central Belt, and the Coastal Belt (Blake et al.,

1982). The divisions are based of differing metamorphic grade and lithology of the

rocks. West of the study area the rocks of the eastern belt of the Franciscan complex

consist of schist, meta-conglomerate, greywacke, meta-sandstone, and minor amounts of

meta-basalt (greenstone) and chert.

The Coast Range Ophiolite

The Coast Range Ophiolite is located between the Franciscan Complex and the Great Valley Group (Bailey et al., 1970). The Coast Range Ophiolite is composed of

9 basalt, diabase, gabbro, chert, and serpentine (Bailey et al., 1970). Rocks from the Coast

Range Ophiolite have a lower metamorphic grade than the rocks of the Eastern Belt of the Franciscan Complex to the west (Blake and Jones, 1970). West of the study area the

Coast Range Ophiolite consist of serpentine and meta-basalt (greenstone) with minor amounts of chert and intrusive igneous rocks.

The Great Valley Group

The rocks of the Great Valley Group consist of marine sedimentary sandstone and shale of Jurassic to Cretaceous age. The nomenclature for the rocks of the Great

Valley Group has been redefined multiple times in the past 130 years based upon differing interpretations of the geochemistry, the stratigraphy, the age of the units, and different interpretations of the regional geology over time. A brief summary of these changes is described in the following paragraphs.

The Great Valley Group was divided into two units: the Knoxville beds and the Horsetown beds (White, 1885). Later these rocks were divided into three geologic units; the Jurassic Knoxville Series, the Lower (Early) Cretaceous Shasta Series, and the

Upper (Late) Cretaceous Chico Series (Anderson, 1938).

The Upper Cretaceous rocks of the Chico Series (Anderson, 1938) were later divided into six formations by Kirby (1943) based upon the lithology of the units. These units from oldest to youngest were named: Venado Sandstone, Yolo Shale, Sites

Sandstone, Funks Shale, Guinda Sandstone, and Forbes Sandstone. Clay shale at the base of the Forbes Sandstone was later re-named the Dobbins Shale (Pessagno, 1976).

Cretaceous-aged rocks including the Cretaceous Shasta Series and Chico

Series (Anderson, 1938) including the seven formations of Kirby (1943) and Pessagno

(1976) were later grouped into three formations based on the mineralogy and geochemistry of the rocks (Dickinson and Rich, 1972; Ingersoll et al., 1977). The Boxer

Formation included the Clark Valley mudstone and the Julian Rocks conglomerate of

Chuber (1961). The Cortina Formation included the lower Venado Sandstone, Yolo

Shale, Sites Sandstone, and Funks Sandstone. The Rumsey Formation included the upper

Funks Sandstone, Guinda Sandstone, Dobbins Shale, and the Forbes Sandstone.

The Great Valley Group was later divided into two units, the Elder Creek

Terrane and the Great Valley Sequence, based on the origin of the clasts in the rocks and

the basement unit upon which each sequence rests (Blake et al., 1992). The Jurassic to

Late Cretaceous Elder Creek Terrane sediments were deposited on oceanic basement

rocks of the Coast Range Ophiolite. The Middle to Late Cretaceous Great Valley

Sequence overlies Klamath basement north of Paskenta, and Sierran Basement on the

valley floor to the south and east of the study area. These two units are separated by the

Salt Lake Fault in the Lodoga Quadrangle south of the study area (Brown and Rich,

1961), and the Cold Fork Fault Zone north of the study area (Jones and Irwin, 1971;

Harwood and Helley, 1987; Blake et al., 1992). The Salt Lake Fault has not been

described in the study area.

The formation names proposed by Kirby (1943) and Pessagno (1976) will be used in this study. The descriptions are based on lithology and field observation rather than mineralogy or other criteria that would be difficult to identify in the field.

Venado Sandstone. The Venado Sandstone is described as sandstone with

minor amounts of siltstone and shale, with conglomerate becoming common near the base of the unit (Kirby, 1943). The thickness of the unit varies from over 3000 feet (915

m) in the north to 2000 feet (610 m) to the south (Kirby, 1943). The Venado Sandstone

is the only one of the Upper Cretaceous formations that thickens to the north (Kirby,

1943).

Yolo Shale. The Yolo Shale is described as well-bedded, greenish grey or

light drab siltstones with numerous thin layers of fine flaggy sandstone. Sandstone

becomes common toward the base of the unit. (Kirby, 1943). The thickness of the unit

varies from 500 feet (153 m) to the south to 100 feet (30 m) to the north and thins to the north (Kirby, 1943)

Sites Sandstone. The Sites Sandstone is described as massive to well-bedded,

concretionary, greenish gray to light drab sandstone (Kirby, 1943). The thickness of the

unit varies from 125 feet (38 m) in the north to 3500 feet (1067 m) to the south (Kirby,

1943). Kirby described the Sites Sandstone in its type area south of the study area.

Kirby (1943) stated that the Sites Sandstone pinches out a few miles north of Logan

Creek in southern Glenn County. North of this location the Sites Sandstone is absent and the Funks Shale directly overlies the Yolo Shale.

Funks Shale. The Funks Shale is described as 620 feet (189 m) of greenish

gray clay shale and siltstone (Kirby 1943). The shale and siltstone thicken to the south to

as much as 2500 feet (762 m) (Kirby 1943).

Guinda Sandstone. The Guinda Sandstone is described as 1000 feet (305 m)

of massive to well-bedded, fine to medium-grained, gray to buff concretionary sandstone.

A 150 foot thick unit of thinly-bedded gray carbonaceous shale and siltstone with rounded limestone concretions occurs near the middle of the section (Kirby, 1943).

Dobbins Shale. Kirby (1943) described a 250 to 300 foot (76 to 91 m) thick

unit of gray to bluish gray clay shale at the base of the Forbes Formation. This shale at

the base of the Forbes Formation was later re-named the Dobbins Shale (Pessagno,

1976). A submarine canyon of Santonian age was identified in the foothills west of the

town of Williams (Williams et al., 1998). The Dobbins Shale is the basal fill in the

Williams Submarine Canyon (Williams et al., 1998).

Forbes Sandstone. The Forbes Sandstone is described as 1300 feet (396 m) of

well-bedded to massive, light greenish gray to gray, carbonaceous siltstone and silty

shale, with thin beds of fine-grained to coarse-grained pebbly sandstone (Kirby, 1943).

The Black Butte formation

The Black Butte formation was discovered during construction of Black Butte

Dam. This sedimentary unit was informally named the Black Butte formation by the

Army Corps of Engineers (1963). This alluvium occupies a stratigraphic position below

the Lovejoy Basalt at the dam site (Hancock et al., 1986).

The Black Butte formation is described as massive, grayish green to blue gray

volcanic clay and sand with a thickness of over 100 feet (30 m) below Black Butte Dam

(Hancock et al., 1986). A coarse facies of sand and conglomerate up to 70 feet (21 m)

13 thick occurs at the base of the exposure on the north side of Black Butte Dam (Hancock et al., 1986). The sand and conglomerate interfinger with the clay in the lower part of the section (Hancock et al., 1986). Clasts of quartzite, chert, “volcanic rocks”, jasper, vein quartz and metamorphic rocks up to 6 inches in diameter were reported from this coarse facies during construction of Black Butte Dam (Hancock et al., 1986). The sediments of the Black Butte formation alluvium are similar in color and composition to the Tehama

Formation alluvium. However the fine sediments are arkosic and the coarse clasts have an origin from both the Coast Ranges and the Sierra Nevada or Klamath Mountains. A

‘Baked Zone’ is present at the top of this unit at the contact with the overlying Lovejoy

Basalt. Gravel benches with clasts of Sierran origin were reported at an elevation of 900 feet on the western side of Middle Butte (Hancock et al., 1986). Though these gravels occur in the same stratigraphic position as the Black Butte formation, they were interpreted as a fluvial deposit that was not related to the Black Butte formation (Hancock et al., 1986).

The Black Butte formation is present below the Lovejoy Basalt in the same stratigraphic position as the auiferous gravels in the Sierra Nevada Mountains. Garside

(2005) discussed auriferous gravels in the Susanville area that were both Eocene and

Miocene age. The Black Butte formation is interpreted as Oligocene to early Miocene age (Hancock et al., 1986). Alluvial units in a stratigraphic position below the Lovejoy

Basalt have been described from gas wells in Sacramento Valley as the upper Eocene

Nord Formation (Van den Berge, 1968), the Eocene Markley Sandstone (Redwine,

1972), and an un-named nonmarine unit (Harding et al., 1960). Coarse grained alluvium

below the Tuscan Formation and the Lovejoy Basalt have been reported from a few

locations on the east side of the Sacramento Valley including the New Era Formation

(Creely, 1956). The sandstone and conglomerate of the New Era Formation contain

clasts derived from the Lovejoy Basalt so they are of the same age or younger than the

basalt. Street (2009) described conglomerate with a similar composition as the Black

Butte formation below the Lovejoy Basalt at Oroville Table Mountain. Three lithologic units, a cross-bedded sandstone and two conglomerate units were described from a location near Phantom Falls at the end of Coal Canyon. The sandstone was described as

“…light brown, well-sorted, medium-grained, cross-bedded sandstone, likely derived from a granitic source…” which conformably overlies an unconsolidated conglomerate.

The conglomerate contained clasts of volcanic and metamorphic rocks including quartz pebbles and cobbles up to a foot in diameter. A second conglomerate contains clasts of basalt and was interpreted to have been eroded from the overlying Lovejoy Basalt. The

sandstone and the first conglomerate are similar to the Black Butte formation, the second

conglomerate would likely be the New Era Formation of Creeley, (1959).

Lovejoy Basalt

The Orland Buttes are capped by black aphanitic basalt that has been

identified as a western exposure of the Lovejoy Basalt (Durrell, 1959). Putnam Peak north of Vacaville is the southernmost exposure of the Lovejoy Basalt (Weaver, 1949).

The Lovejoy Basalt is found in natural gas wells east of the study area (Russell, 1931).

Seismic reflection surveys have also identified Lovejoy Basalt below the floor of the

Sacramento Valley (Redwine, 1972; McManus et al., 2014). Below the valley floor the

Lovejoy Basalt caps stratigraphic high regions with up to 400 feet of relief (McManus et

al., 2014). The basalt flows were eroded into a series of plateaus and buttes during the

formation of the middle to late Miocene, upper Princeton Valley (Redwine, 1972). Two

outcrops of the Lovejoy Basalt are present approximately 10 miles south of the Orland

Buttes, north of Hwy 162 and west of the town of Willows (Stefanov, 1962; see figure 1).

Beneath the Sacramento Valley the basalt reaches a maximum thickness of approximately 245 meters (800 feet), (Garrison et al., 2008). At the Orland Buttes the basalt reaches a maximum thickness of 70 feet (21 m) and thins to 40 feet (12 m) in some areas (Hancock et al., 1986). Earlier researchers considered the basalt late Eocene to early Oligocene in age (Durrell, 1959). Recent K-Ar and Ar-Ar dating has identified a middle Miocene age, 15.4 Ma (Page et al., 1995; Garrison et al., 2008,) and 16 Ma

(Busby and Wagner, 2004).

Russell (1931) described the basalt at the Orland Buttes as a flow of basalt that was deposited onto rocks of the Great Valley Group. Alluvium of the Tehama

Formation was later deposited on the basalt. A fault was assumed to exist west of the

Orland Buttes and was the source of the basalt (Russell, 1931). The fault was later informally named the Black Butte fault. The basalt at the Orland Buttes was later

identified as a western exposure of the Lovejoy Basalt (Durrell, 1969). The location or even the existence of the Black Butte fault has been questioned by some researchers

(Hancock et al., 1986) among others.

Tehama Formation

Sedimentary units attributed to the Ione Formation and Tuscan Formation by Diller

(1894) were re-named the Tehama Formation (Russell, 1931; Russell and Van Der Hoof,

1931; Anderson and Russell 1939). These deposits of alluvium were described as a

separate unit from the Tuscan Formation based upon the lithology of the clasts in the

sediments. The alluvium on the west side of the Sacramento Valley was derived from the

Coast Ranges and was named the Tehama Formation (Russell, 1931). The alluvium on the east side of the Sacramento Valley is the Tuscan Formation. Sediments in the Tuscan

Formation are volcanic in origin and originate from a source area in the Sierra Nevada

Mountains (Russell, 1931). Deposits of Pliocene alluvium that were not included in the original description of the Tehama Formation occur in the Rumsey Hills (Russell, 1931).

Russell (1931) proposed the name of Capay Formation for this Pliocene alluvium, but the name was adopted for the Paleocene to Eocene marine deposits in the Capay Valley

(Crook and Kirby, 1935). The Pliocene alluvium in the Rumsey Hills was later included in the Tehama Formation (Anderson and Russell, 1939).

The Tehama Formation consists of as much as 2,000 feet (600 m) of pale greenish-gray to tan, silty, sandy clay with cross-bedded sand and gravel conglomerate

(Russell, 1931). Conglomerate is common toward the apices of the alluvial fans and near the base of the Tehama Formation (Russell, 1931). Caliche is present in claystone throughout the unit but is more common near the base of the formation (Russell, 1931).

Two units of tuff, the Nomlaki Tuff and the Putah Tuff, are present near the base of the

Tehama Formation. Tuffaceous clay is also common near the base of the Tehama

Formation and is associated with the Nomlaki Tuff (Russell, 1931).

The Tehama Formation is composed of alluvium that was deposited on a relatively flat lying surface (Russell, 1931). The Tehama Formation was deposited during a time when the Coast Ranges were lower in elevation and the climate was milder than at present, with warmer winters and cooler wetter summers (Russell, 1931). Fossil plants discovered in stratigraphic units that are the same age as the Tehama Formation represent species that require a climate with warmer winters and cooler, wetter summers

(Dorf, 1933).

Geologic maps produced by Russell (1931) show exposures of the Tehama

Formation over large areas north and west of the Orland Buttes. Russell (1931) explained that Tehama Formation sediments were overlain by Red Bluff Formation gravels over large portions of the map. These deposits were not plotted on the maps produced by Russell in 1931 because there was insufficient time to accurately document the extent of these Pleistocene sediments, Russell in 1931 stated:

Unfortunately time was not available for the differentiation of the Pleistocene Red Bluff gravels in the mapping, and it must be borne in mind that patches of the Red Bluff cap the Tehama and overlap on the Cretaceous throughout much of the region, near the eastern edge of the area mapped as Tehama, the Red Bluff is almost continuous and outcrops of the Tehama only occur in the deeper stream cuts.

Subsequent researchers have not taken this information into account during later studies and in preparation of geologic maps of the region. Outcrops of the Tehama

Formation are less extensive than many recent maps would imply. The Tehama 18

Formation is found on the western side of Sacramento Valley from Redding in the north

to Vacaville in the south (Anderson and Russell, 1939; see figure 2). The Tehama

Formation is composed of a series of alluvial fans that coalesce into a single continuous

unit flanking the Coast Ranges. This bajada is now being eroded by the modern streams and Tehama Formation sediments are present in stream beds and at the base of strath terraces in some drainages. The Tehama Formation lies unconformably on Mesozoic rocks of the Great Valley Group and older Cenozoic stratigraphic units including the

Lovejoy Basalt east of the Orland Buttes (Russell, 1931), and the upper Princeton Valley fill (Redwine, 1972). The Tehama Formation is overlain by Pleistocene alluvium of the

Red Bluff Formation, the Riverbank Formation, and the Modesto Formation (Russell,

1931; Helley and Harwood, 1985; Helley and Jaworoski, 1985).

Nomlaki Tuff and Putah Tuff

Volcanic ash on the west side of the Sacramento Valley that was originally

named the Tuscan Tuff (Diller, 1894) was renamed the Nomlaki Tuff by (Russell, 1931).

The Nomlaki Tuff is a light gray to pink, massive pumice lapilli tuff (Russel, 1931;

Anderson and Russell, 1939). The stratigraphic position of the Nomlaki Tuff can range

from 700 feet (214 m) above the base of the Tehama Formation on the valley floor to the

base of the Tehama Formation toward the mountain front (Russell, 1931). The age of the

Nomlaki Tuff was determined by K/Ar dating at 3.4 Ma (Everden et al., 1964), and

recently, 3.27 Ma (Knott and Sarna-Wojcicki, 2001). The Latour Volcanic Center,

located 25 km northwest of Lassen Peak, is the most likely source of the Nomlaki Tuff

based on the mineral composition of the tuff (Hull et al., 2008).

Figure 2. Extent of the Tehama Formation in the Sacramento Valley. Map of the extent of the Tehama Formation, the Tuscan Formation, and surficial deposits of the Laguna Formation in the Sacramento Valley, California. Source: McManus, D., Stanton K., Spangler, D., 2014, Geology of the northern Sacramento Valley: California Department of Water Resources, 77 pgs.

The Putah Tuff occupies a similar stratigraphic position as the Nomlaki Tuff

in the Rumsey Hills. The Putah Tuff is not found north of the Rumsey Hills (Miller,

1966). The age of the Putah Tuff was determined by K/Ar dating at 3.3 Ma (Simms and

Sarna-Wojcicki, 1975). Though the two units of tuff are of a similar age, and occupy a

similar stratigraphic position within the Tehama Formation, they have different mineral

compositions and different origins (Miller, 1966; and Sarna-Wojcicki, 1970).

Red Bluff Pediment and Red Bluff Formation

The Red Bluff Formation was named after the red gravels found north of the town of Red Bluff (Diller, 1894). The Red Bluff Formation is described as a 1 to 10 meter (3.2 to 32 feet) thick unit of bright red sandy gravel that was deposited during the formation of the Red Bluff Pediment (Steele, 1980; Helley and Jaworoski, 1985). The

Red Bluff pediment gravels overlie Tehama Formation alluvium and Cretaceous rocks of

the Great Valley Group (Steele, 1980; Helley and Jaworoski, 1985). The Red Bluff

Pediment was formed in the early Pleistocene.

In the northern Sacramento Valley the pediment is present on both sides of the

valley as a relatively flat surface that is inclined toward the center of the valley (Steele,

1980; Helley and Jaworoski, 1985). In many parts of the Sacramento Valley the

pediment has been completely removed by erosion, in some areas dissected remnants of

the pediment remain (Steele, 1980; Helley and Jaworoski, 1985). Mima mounds are

present on the flat surface at the top of the pediment gravels and on eroded slopes on the

edges of the pediment that are underlain by Red Bluff gravels (Helley and Jaworoski,

1985).

Steele (1980) mapped the Red Bluff Pediment by contouring the flat surface at

the top of the pediment gravels. Helley and Jaworoski (1985) developed elevation

contours of the top of the Red Bluff gravels and the Modesto Formation terraces.

Changes in relative elevation of these two units were used to determine where subsequent

deformation of the Red Bluff Pediment has occurred. Deformation of the pediment

surface was used to determine the location of faults and domes that have formed after the

Red Bluff Formation gravels were deposited (Helley and Jaworoski, 1985).

The age of the Red Bluff pediment has been determined based on the

stratigraphic position of two volcanic units, the Olivine Basalt of Deer Creek and the

Rockland Ash. The Red Bluff Formation gravels overlie the Olivine Basalt of Deer

Creek which has been dated at approximately 1.08 Ma (Harwood and Doukas, 1981;

Helley and Jaworoski, 1985). The Rockland Ash overlies the Red Bluff Formation

gravels and has been dated at 0.45 Ma (Harwood and Doukas, 1981; Sarna-Wojcicki,

1985). The stratigraphic position of these two units in relation to the Red Bluff Pediment shows that the pediment was formed between 1.08 Ma and 0.45 Ma

In the northern San Joaquin Valley, sedimentary units of similar age and

stratigraphic position as the Red Bluff Formation are named the Arroyo Seco gravels

(Piper et al., 1939), and the Merced gravels (Arkley, 1952; Marchand and Allwardt,

1981). These gravels both overly a pediment; the Arroyo Seco dissected pediment (Piper

et al., 1939) and the North Merced Pediment (Arkley, 1952; Marchand and Allwardt,

1981). These pediments were formed on sediments of the Pliocene Laguna Formation

and are overlain by the Turlock Lake, Riverbank, and Modesto formations. The age of

the Arroyo Seco Pediment and Merced Gravels is reported between 1 Ma and 730 Ka

(Marchand and Allwardt, 1981) based on the age of the Deer Creek Basalt and the Bishop

Tuff .

Turlock Lake Formation

The middle Pleistocene Turlock Lake Formation is described as well sorted, brown to tan arkosic clay, silt, and sand that grades upward into coarse sand and gravel that were deposited on the valley floor on the east side of the San Joaquin Valley (Arkley,

1954; Davis and Hall, 1959; Marchand and Allwardt, 1981). The Turlock Lake

Formation was divided into two informal units: upper and lower based on the stratigraphic position of the units and on the presence of paleosols (Marchand and

Allwardt, 1981; Helley and Harwood, 1985). Two prominent marker beds, the Corchran

Clay and the Friant Tuff, are found in the Turlock Lake Formation. The age of the

Turlock Lake Formation was determined to be between 730,000 and 500,000 years BP

(Marchand and Allwardt, 1981) based on the age of buried soils and the age of the Friant

Tuff and the Bishop Tuff.

The Turlock Lake Formation has not been reported from surface exposures

north of the Yuba River (Creely, 1965; Busacca, 1982, 1989). The Turlock Lake

Formation and a tuff that has been correlated with the Friant Tuff have been reported

from well logs north of the Sutter Buttes (Springhorn, 2008). Exposures of the Turlock

Lake Formation have not been reported in the field area (Helley and Harwood, 1985).

The Turlock Lake Formation occurs in a stratigraphic position below the Riverbank

Formation on the eastern side of the southern Sacramento Valley and northern San

Joaquin Valley, and above a pediment that is the same age as the Red Bluff Pediment. In the northern Sacramento Valley an erosional unconformity occurs in the same stratigraphic position as the Turlock Lake Formation.

Riverbank Formation

The middle Pleistocene Riverbank Formation is described as reddish brown silt, sand, and gravel composing a series of alluvial fans deposited on the valley floor on the east side of the San Joaquin Valley (Davis and Hall, 1959; Marchand and Allwardt,

1981). The Riverbank Formation was divided into three informal units: the upper, middle, and lower based on the stratigraphic position of the units and on the presence of paleosols (Marchand and Allwardt, 1981). The age of the Riverbank Formation was determined to be between 450,000 and 130,000 years BP (Marchand and Allwardt,

1981).

The three units of the Riverbank Formation described by Marchand and

Allwardt (1981) are not present in the study area (Helley and Harwood, 1985). The

Riverbank Formation is divided into two units in the study area, and east of the study area on the Stony Creek Fan. The upper Riverbank Formation is described as unconsolidated but compact, dark brown to red alluvium composed of gravel, sand silt and with minor clay (Helley and Harwood, 1985). The lower Riverbank Formation is described as red semi-consolidated gravel, sand, and silt (Helley and Harwood, 1985). Alluvium of the middle Pleistocene Riverbank Formation has been described as terrace deposits along

Stony Creek and smaller streams in the study area (Steele, 1980; and Helley and

Harwood, 1985). In many places in the northern Sacramento Valley, alluvium that was

24 mapped as Red Bluff Formation gravels (Diller, 1894; Russell, 1931) has been interpreted by later researchers as the Riverbank Formation (Helley and Harwood, 1985).

Modesto Formation

The late Pleistocene Modesto Formation is described as yellowish brown sandstone and siltstone; and unconsolidated, poorly sorted sandstone and siltstone (Davis and Hall, 1959; Marchand and Allwardt, 1981). The Modesto Formation forms the lowest terraces along rivers draining the Sierra Nevada Mountains on the east side of the

San Joaquin Valley (Marchand and Allwardt, 1981). The age of the Modesto Formation was determined to be between 42,000 and 12,000 years BP (Marchand and Allwardt,

1981).

The Modesto Formation is divided into two units east of the study area on the

Stony Creek Fan. The upper unit of the Modesto Formation is described as unconsolidated unweathered gravel, sand silt and clay (Helley and Harwood, 1985). The lower unit of the Modesto Formation is described as unconsolidated slightly weathered gravel, sand, and clay (Helley and Harwood, 1985).

Present Model of the Geology of the Study Area

The most recent geologic map of northern California was produced by the

Department of Water Resources in 2014 (see figure 3). The map was compiled from the

“Geologic map of the late Cenozoic Deposits of the Sacramento Valley and northern

Sierran Foothills, California” (Helley and Harwood, 1985). The area west of the Orland

Figure 3. Geologic Map of the Study Area and Surrounding Region. Sources: Map modified from: Helley, E.J., and Harwood, D.S., 1985, Geologic map of the late Cenozoic deposits of the Sacramento Valley and northern Sierran Foothills, California: Miscellaneous Field Studies Map MF-1790, scale 1:62 500, 5 sheets, 24 p. text. McManus, D., Stanton K., Spangler, D., 2014, Geology of the northern Sacramento Valley: California Department of Water Resources, 77 pgs.

Buttes is covered by deposits of the Tehama Formation (tan). The Riverbank Formation

is present as uplifted terraces on the margins of the existing streams (dark green).

Modesto Formation sediments are visible on the valley floor (light green). Red Bluff

Formation sediments cover the Red Bluff Pediment west of the lake (red).

The apex of the Stony Creek Fan is visible on the eastern side of the map.

The Black Butte fault is located west of the Orland Buttes. The Black Butte fault trends

southeast and connects with the Willows Fault south and east of the map area. West of

Black Butte Lake, the Paskenta Fault trends northwest across the map area. The Paskenta

Fault connects with the Willows fault south of Black Butte Lake.

To better understand the complex relationships between these geologic units

and the underlying structures, this thesis investigates the surficial geology of Black Butte

Reservoir, in Glenn and Tehama counties. Underlying structures recorded by previous

seismic surveys were analyzed to build a better picture of the depositional environments.

Location of the Study Area

The study area is located at the Black Butte Lake Recreation Area on the western side of the northern Sacramento Valley. The Sacramento Valley is located in the

northern third of the Great Valley Physiographic Province (California Geological Survey,

2002). The Great Valley is a structural trough located between the Coast Ranges

Physiographic Province on the west, and the Sierra Nevada Physiographic Province on

the east. The study area at Black Butte Lake is 9 miles (14 km) west of the town of

Orland and Interstate Highway 5 in western Glenn and Tehama counties (see figure 4 and

27 figure 5). Black Butte Lake can be located on the U.S. Geological Survey (U.S.G.S.)

Black Butte Dam, Sehorn Creek, Fruto, and Julian Rocks, 7.5 minute (1:24,000 scale)

Quadrangles.

Figure 4. Regional Map of the Northern Sacramento Valley and the Study Area.

Figure 5. Map of the Study Area at Black Butte Lake. Map of study area at Black Butte Lake with descriptions of locations and geographic features noted in report.

Methods and Sources of Data

Field Surveys

Field surveys were conducted during the summer, fall and winter of 2015.

Surveys continued into the spring of 2016 to take advantage of low water levels during

the drought. The low water levels left additional shoreline exposed; as a result, geologic

structures and features that would be inundated most years were accessible.

Surveys included “ground truthing” published maps of the region.

Stratigraphic contacts and geological structures that were observed were plotted on

USGS 7.5 minute quadrangle maps. A description of the lithology of the geologic units

was recorded during field surveys. Stratigraphic sections were measured using a metric

scale Jacobs Staff and a Brunton compass. Elevation was determined using a Garmin

Rhino 530 HCx GPS unit and by correlating the base of the measured sections to the

published lake levels on the California Department of Water Resources website. Data from field surveys were used to field check existing maps of the area and compile updated geologic maps and stratigraphic sections. Stratigraphic sections were measured in meters and converted to feet, elevation was recorded in feet above sea level, and

stratigraphic thickness reported by previous researchers is presented in feet and converted

to meters.

Clast Composition Surveys/Pebble Counts

The clasts in the Pliocene and Pleistocene alluvium show that the alluvium has

an origin from the Coast Ranges of California (Russell, 1931). According to Russell

(1931), the relative composition of the clasts varies from the units of different ages.

This variation in the lithology of the sediments may reflect changes in the

bedrock in the drainages that were the source for these sediments. A change in the

bedrock lithology of the source area of a drainage over time due to headward erosion and

30 stream capture can change the composition of the clasts in the sediments. A change in the composition of the sediments over time can be identified by conducting pebble counts/clast composition surveys.

Pebble counts/clast composition surveys were conducted to determine if there was a difference in the lithology of the clasts between the alluvial units in the study area.

The location of each pebble count was chosen to either verify conclusions of other researchers, or to identify and correlate sedimentary outcrops at differing parts of the study area. The location of each count was determined using a Garmin Rhino 530 HCx

GPS unit and locations were recorded for reference.

Pebble counts/clast composition surveys involve collecting a measured volume of clastic sediment and processing the sample through a sieve to remove the fine grained sediments. The sieve used for this study is a 3/4 inch mesh USA Standard mesh sieve produced by the Humboldt Manufacturing Company. Processing the sediments through the sieve removes pebbles smaller than 3/4 inch in diameter. A sufficient volume of pebbles is reserved to supply at least 100 individual pebbles. The pebbles are divided into four or more smaller piles that are counted individually before counting the next pile. This assures that there is no bias by size or other criteria on the part of the person performing the pebble count. The percent composition, standard deviation, and range of the lithology of the pebbles is calculated for comparison with other samples.

Stratigraphic Sections and Geologic Cross Sections

General stratigraphic sections were compiled during the literature review.

Detailed stratigraphic sections were compiled from data collected during field surveys.

Geologic cross sections were compiled from field measurements to illustrate the spatial relationships of the geologic units.

CHAPTER III

RESULTS OF FIELD SURVEYS

Description of the Stratigraphic Units in the Study Area

The Yolo Shale and Venado Sandstone

The Yolo Shale and Venado Sandstone in the study area are green to tan shale

interbedded with green sandstone. The orientation of the bedding in the shale on the

ridge between the two arms of the lake show an anticline is present in the Cretaceous

rocks, this is the Sites Anticline. Vertical bedding in the shale north of the Equestrian

Parking Area (see figure 6, location #1) is a surface exposure of the Sites Thrust. West of

the Equestrian Parking Area, at Steuben Bridge (see figure 5), and in the late Pleistocene

strath terrace north of Steuben Bridge (see figure 6 location #3) the beds of the sandstone

and shale dip to the west. East of the Equestrian Parking Area sandstone was observed in

two stream beds on the southern side of the ridge between Stony Creek and the North

Fork of Stony Creek (see figure 6, location #2). These outcrops of sandstone occur in

isolated locations where small ephemeral streams have eroded through the overlying

alluvium. Shale was reported in stream beds west of the Grizzly Flat Recreation area (see figure 6, location #25) the beds of the sandstone and shale dip to the east at this location

(Hancock et al., 1986). These exposures are on private property and were not surveyed

during the study.

Figure 6. Map of the Study Area Showing the Location of Geologic Features. Map of study area at Black Butte Lake with the location of geologic features in that are noted is this thesis.

Outcrops of Cretaceous rocks have been reported west of the study area at the base of a late Pleistocene age strath terrace along the North Fork of Stony Creek (see figure 6, location #4) and at the base of the upper Riverbank Formation terrace north of the North Fork of Stoney Creek (Hancock et al., 1986; see figure 6, location #24). These

Cretaceous rocks are located west of the study area and are on private property and were

not surveyed during the study. No exposures of the Cretaceous rocks were observed in

the study area on the North Fork of Stony Creek arm of Black Butte Lake.

Guinda Sandstone

Sandstone and shale of the Guinda Sandstone in the study area occur as tan to

grey sandstone interbedded with reddish brown shale. The sandstone beds are massive

and vary in thickness from less than 0.3 m (1 foot) to 1.3 m (4 feet) over most of the

section. At the top of the unit two of the beds exceed 3.6 meters (12 feet) in thickness.

Parallel lamination is common near the base of the sandstone beds and convoluted

laminations are common near the top of the beds. Bouma sequence stages A, B, C, and D

are present in the thicker sandstone beds. The interbedded shale also varies in thickness

up to 15 cm (6 inches). The shale beds likely represents Bouma sequence stage E. The

strike of bedding is approximately 350 degrees dipping to the east at 32 degrees. Cliffs

have been formed by wave action on exposures of the Guinda sandstone on the western

slope of the Middle Butte and the south slope of North Butte at Eagle Pass (see figure 6,

location #5).

Dobbins Shale

The Dobbins Shale in the study area is black to reddish brown shale. The

strike of the bedding is approximately 350 degrees dipping to the east at 28 degrees. The upper part of the Dobbins Shale is blue-black clay shale with concretions. The concretions weather white to pale yellow and range in size from a few inches to a few feet in diameter. The lower part of the Dobbins shale is reddish brown to black shale

with reddish brown concretions that range in size from a few inches to a foot in diameter.

The Dobbins Shale crops out on both sides of Eagle Pass, west of the Eagle Pass

Recreation Area (see figure 5).

Forbes Sandstone

The Forbes Sandstone at Black Butte Lake is bedded green to yellow sandstone interbedded with green, tan, and gray shale. Sandstone and shale of the Forbes

Sandstone is exposed at the Eagle Pass Recreation Area (see figure 5), both along the lake shoreline and as an erosion resistant ridge immediately west of the recreation area.

Shale is common and reddish brown concretions with a yellow oxidized exterior are present in the shale beds. The strike of bedding is approximately 350 degrees dipping to the east at 25 degrees. Between the Eagle Pass Recreation Area and Black Butte Dam sandstone and shale of the Forbes Sandstone are exposed in small windows through the talus that was eroded from the overlying Lovejoy Basalt. On the south slope of North

Butte shale is common at the lower part of the Forbes Sandstone and sandstone becomes common upsection.

Yellow sandstone and shale of the Forbes Sandstone is exposed in a road cut on the access road to the Eagle Pass Recreation area (see figure 6, location #6).

Sandstone and shale of the Forbes Sandstone is exposed in road cuts on the north side of

County Road 206 as it passes between Middle Butte and South Butte (see figure 6, location #7). This outcrop was described by Russell (1931) in his dissertation on the

Tehama Formation.

The Black Butte formation

The Black Butte formation was reported from 4 locations at Black Butte Lake

(Hancock et al., 1986). Outcrops were reported at the base of the dam, at the overflow spillway outlet, at the base of the control tower, and as gravel benches at an elevation of

900 feet on the western side of Middle Butte. During field surveys additional outcrops were located on the northern and southern slopes of North Butte.

The deposit of Black Butte formation claystone that was reported at the base of the dam is not accessible. Black Butte formation clay is present at the inlet for the overflow spillway immediately west of the dam on the south side of North Butte (see figure 6, location #8) and continues west along the south side of North Butte. The sediments are greenish gray clay that has been altered to a dark brown to black porcelain- like material in a “baked zone” immediately below the contact with the overlying

Lovejoy Basalt in the overflow spillway. The lower part of the Black Butte formation alluvium is present along the lake shore west of the overflow spillway on the south side of North Butte (see figure 7). This outcrop is present as wave cut benches at the high water level and scattered exposures below the high water level where the cover of talus from the Lovejoy Basalt is absent. The sediments are greenish tan clay, silt, sand, and gravel conglomerate (see figure 7). The fine-grained sediments are poorly indurated and are almost indistinguishable from the claystone of the Tehama Formation. The gravel units contain clasts of quartzite, brown silicified sandstone and conglomerate, granite, gneiss, chert, and silicified wood.

Figure 7. Black Butte Formation Sediments on the South Side of North Butte. Black Butte formation sediments in wave cut bench at high water level on the south side of North Butte. Jacobs Staff marked at 1dm increments.

The outlet from the overflow spillway was surveyed. The pebble conglomerate described by (Hancock et al., 1986) was present at this location. The conglomerate that occurs at this locality is lacking plutonic rocks that are common in the Black Butte formation. A large spoils pile south of the overflow spillway outlet does contain clasts from both the Lovejoy Basalt and Black Butte formation.

The outcrop south of the intake tower is greenish gray to yellow-green bedded claystone that extends from an elevation of 485 feet (147.8m) to below the low water level at an elevation of at least 437 feet (133m), (see figure 6, location #9). The outcrop of claystone extends west for an unknown distance. West of the intake tower the outcrop

is covered by talus from the overlying Lovejoy Basalt. The tops of the claystone beds have paleosols a two to three inches thick with root molds to 1 mm in diameter. At the top of this outcrop the clay is altered to a dark brown to black porcelain-like material in a

“baked zone” that is immediately below the contact with the overlying Lovejoy Basalt.

Gravel benches that were described at an elevation of 900 feet on the western side of Middle Butte (Hancock et al., 1986) were not observed. The top of Middle Butte is on private property and the outcrops were not surveyed during this study. During surveys of the western side of Middle Butte numerous rounded cobbles were found mixed with the rubble of Lovejoy Basalt that covers the slope. The cobbles were composed of quartzite, massive quartz, conglomerate, brown and black porphyritic basalt, granite, gneiss and silicified wood. Many of the clasts of quartzite were oxidized red or yellow on the weathered surfaces.

A new exposure of Black Butte formation pebbly sandstone was seen in a small drainage just south of a coffer dam on the north side of North Butte (see figure 6,

location #10). This outcrop is pebbly sand that is identical to the outcrop along the lake

shore on the southern side of North Butte. This area was mapped as Tehama Formation

by Russell (1931).

Lovejoy Basalt

The Miocene Lovejoy Basalt is an erosion-resistant unit that caps the Orland

Buttes forming flat-topped plateaus. Cliffs on the eroded edges of the plateaus can reach heights of 60 feet (18 m). Large slump blocks of basalt and a talus of volcanic rubble

39 that has been eroded from the cliffs of basalt covers the slopes of the buttes and obscures the underlying geologic units in many places. The base of the Lovejoy Basalt is commonly obscured by the talus but is exposed below the bridge to the outflow tower on the southern side of Black Butte Dam and at the overflow spillway on the north side of the dam (see figure 6, location #8 and #9). At both locations vesicular structures are common in the base of the basalt. The two flows of the Lovejoy Basalt that were reported by Hancock et al., (1986) are visible in the excavation for the overflow spillway.

Tehama Formation

There are two common facies of sediments of the Tehama Formation in the study area. Poorly to moderately indurated claystone and silty claystone are the more common of the two facies (see figure 8). The beds vary in thickness from 0.3 meter to

1.5 meters (1 foot to 5 feet). The color of the claystone varies from tan to greenish gray

(Munsell 5Y 6/2 to 8/3) and light brown (Munsell 10YR 8/3) in the lower part of the

Tehama Formation at one location on the south shoreline of the lake (see figure 6, location #11). Paleosols are common at the top of the beds as lighter colored claystone with common root molds and root casts to 1mm in diameter at the top of the paleosols.

Caliche-filled root casts up to 10 cm (4 in) long and 2.5 cm (1in) wide are common in a few claystone beds below the conglomerate. Caliche is common in the claystone as pedogenic caliche (forming in the soils), nodular caliche, and root molds. Veins of calcrete have been deposited between the beds or capping the beds at many locations.

The second facies of the Tehama Formation is moderately to well indurated, tan to light greenish grey, cross-bedded pebble conglomerate (see figure 10). Clasts in

40 the conglomerate are sub-rounded to rounded, and vary in size from pebbles to small cobbles that rarely exceed 10 cm (4 inches) in diameter. The clasts are mostly greywacke with metamorphic rocks, quartz and chert. The conglomerate is not as common as the claystone in the study area, but it is the most common facies present on the shoreline of the lake. The conglomerate bed varies in thickness from 0.5 m to 5 m in (2 feet to 15 feet). The conglomerate bed continues for miles along the lakeshore.

Figure 8. Claystone Facies of the Tehama Formation. Claystone facies of the Tehama Formation on the west slope of Middle Butte. Photograph shows wave cut benches below the high water level and beds of greenish claystone and dark caliche rich claystone.

Figure 9. Conglomerate Facies of the Tehama Formation. Conglomerate facies of the Tehama Formation exposed in wave cut cliffs on the north side of the point between the Stony Creek and North Fork of Stoney Creek arms of the lake. 1.7 meter Jacobs staff for scale.

The thickest exposures of the Tehama Formation in the study area are present on the southern shoreline of Black Butte Lake. Tehama Formation claystone and conglomerate extend from the elevation of the lake bottom to 70 feet (21 m) above the lake high water level as perched terraces on the slope of Middle Butte (see figure 6, location #12). Tehama Formation sediments are present along the southern shoreline of the lake in bluffs that are 40 feet (12 m) above the high water level at the Orland Buttes

Campground (see figure 5). Claystone and silty claystone are the dominant facies and

have been eroded into wave cut cliffs along the shoreline of the lake. Pedogenic caliche,

nodular caliche, root casts, and calcrete are common in the claystone below the

Conglomerate. The claystone beds also dip a few degrees more steeply to the east than the overlying conglomerate and claystone. Prominent wave cut benches have been formed on these caliche-cemented beds of claystone below the high water level of the lake (see figure 8). From the Orland Buttes Campground and east to Middle Butte, gravel conglomerate is present at the elevation of the highest wave cut bench. The gravel that is eroded from the conglomerate covers the shoreline in many places and obscures the underlying claystone. Tehama Formation sediments are dominant in the cliffs west of the Orland Buttes Campground for approximately a mile and then pinch out abruptly (see figure 6, location #13, also cross-section A-A’ in figure 20).

The total measured stratigraphic thickness of the Tehama Formation on the south shore of Black Butte Lake is 40 meters (133 feet). 19 meters (63 feet) of claystone was observed below the prominent conglomerate bed and an additional 12 meters (40 feet) of claystone was measured from the top of the conglomerate bed to the top of the wave cut cliffs on the south shoreline of the lake. A generalized stratigraphic section was measured and compiled from field measurements (see figure 10). An unknown thickness of rocks below the base of the section was omitted due to lack of exposure and alluvial cover, and approximately 9 meters (30 feet) was omitted from the top of the section due to a lack of observable outcrops on the perched terraces on the west slope of Middle

Butte.

Figure 10. Measured Stratigraphic Section of the Rocks of the Tehama Formation.

Measured stratigraphic section compiled during field surveys. Section describes the rocks exposed along the Shoreline and in wave cut cliffs along the southern shoreline of Black Butte Lake.

Clasts of Lovejoy Basalt were present in two claystone beds of the Tehama

Formation on the south shore of the lake (see figure 6, location #14). The claystone was exposed at 3.2 meters (10.5 feet) and 4.6 meters (15 feet) below the highest wave cut bench on the western side of Middle Butte. Pedogenic caliche and nodular caliche are common in these two units and caliche coats the clasts of basalt (see figure 11).

Figure 11. Lovejoy Basalt Clasts in Tehama Formation Claystone. Caliche coated clasts of Lovejoy Basalt in Tehama Formation claystone on the west slope of Middle Butte. Location is at the base slope in photo of claystone facies (figure 8). 3 decimeter ruler for scale.

The westernmost Tehama Formation exposures on the lakeshore occur in a

creek bank south of the Burris Creek Bridge at the Burris creek Recreation Area (see figure 5). Pebble conglomerate is exposed about 3 feet (1 meter) above lake high water level in a cut bank on the east side of Burris Creek. East of the Burris Creek Bridge the conglomerate bed dips down to the east and decreases in elevation toward the point between the two arms of the lake. The gravel conglomerate beds are eroded into cliffs that are exposed on the northern shoreline of the point when the water levels are low (see figure 6, location #15). The conglomerate at this location is cross-bedded and interbedded with sand and clay (see figure 9). Gravel that has been eroded from the conglomerate obscures the underlying claystone beds along the shoreline but at a few locations the claystone can be seen when the lake level is low.

Sediments of the Tehama Formation are present above the lake high water

level on the northern shoreline of Black Butte Lake in the western part of the study area.

North of the Burris Creek Bridge and west to the Newville Road Bridge the conglomerate

is exposed at the base of south-facing cut banks along the North Fork of Stony Creek (see

figure 6, location #16). The thickness of the conglomerate exceeds 10 feet (3 meters)

above the modern stream bed. The conglomerate also underlies the valley of the North

Fork of Stony Creek at this location. The conglomerate bed dips down to the east and

decreases in elevation to the high water level at the Buckhorn Recreation Area.

Claystone and silty claystone are common in stream beds north of the

Buckhorn Recreation Area. Conglomerate is the dominant facies at the high water level

west of the Buckhorn Recreation Area. West of the Buckhorn Recreation Area the

conglomerate exceeds 12 feet (3.6 meters) in thickness and underlies an upper Riverbank

Formation cut-in-fill terrace. Tehama Formation conglomerate is exposed on the western slope of North Butte below the lake high water level. Claystone is exposed above the conglomerate as perched terraces on the west side of North Butte. East of the boat ramp at the Buckhorn Recreation Area (see figure 6, location #17), the gravel conglomerate is present below lake high water level and green claystone is exposed above the conglomerate. The gravel conglomerate is 2 to 4 meters (6.5 to 13 feet) thick, and overlies green claystone which extends below the conglomerate to the lowest water levels. The claystone is greenish gray with pedogenic caliche, root casts, calcrete veins and paleosols. These claystone beds are similar to claystone beds exposed below the conglomerate on the south side of the lake. These beds also dip a few degrees more steeply to the east than the overlying conglomerate and claystone.

Nomlaki Tuff

The Nomlaki Tuff was not seen in-situ during field surveys. Tuffaceous clasts were present in an upper Riverbank Formation terrace deposit on the southern shore of the lake.

Red Bluff Pediment / Red Bluff Formation

The nearest exposures of the Red Bluff Formation are 1.5 miles northeast of

Black Butte Dam. The sloping surface of the Red Bluff Pediment is present northeast of the study area as a series of flat topped linear ridges covered in eucalyptus trees (Steele,

1980; Blake et al., 1992; Helley and Harwood, 1985). The Red Bluff Pediment north of

Thomes Creek can be seen north of Black Butte Lake from a hill along Black Butte road

(see figure 1). From this location the Red Bluff Pediment is present on the horizon to the

north of Thomes Creek as a flat surface that is tilted down to the east (see figure 12). The

pediment north of Thomes Creek has been mapped in detail by Steele (1980) and Helley

and Jaworoski (1985). The Red Bluff Pediment has been removed by erosion in the

study area and in the region between Thomes Creek and the study area (see figure 1).

Figure 12. View of Red Bluff Pediment and Eroded Region North of the Study Area. View to the north from top of North Butte. Red Bluff Pediment north of Thomes Creek on horizon (arrow). Eroded region with common Riverbank Formation gravels between North Butte and Thomes Creek is in the foreground.

Lower Riverbank Formation

The lower Riverbank Formation alluvium in the study area is red-tan, strong brown (Munsell 7.5YR 5/6 to 5/8), bedded sand, silt and gravel (see figure 13). The

lower Riverbank Formation alluvium is less oxidized and less indurated than the upper

Riverbank Formation alluvium or the Red Bluff Formation gravels. Clasts within the

gravel conglomerate rarely exceed 10 cm (4 inches) in diameter. A cobble conglomerate

near the base of this alluvium contains clasts of chert and metamorphic rocks larger than

30 cm (12 inches) in diameter.

Figure 13. Lower Riverbank Formation Alluvium. Lower Riverbank alluvium in stream cut on point between Stony Creek and the North Fork of Stony Creek.

This alluvium is the Red Bluff gravels that were included with the Tehama

Formation on maps produced by Russell (1931). This deposit of alluvium was not recognized as a separate unit by subsequent researchers (Steele, 1980; Blake et al., 1992;

Helley and Harwood 1985). Hancock et al., (1986) did state that the Tehama Formation was coarser grained and had a higher degree of oxidation along the lakeshore. These alluvial fan and terrace deposits are in a stratigraphic position that is between the Perkins

Terrace (Steele, 1980) and the Red Bluff Pediment, the Redding High Floodplain of

(Steele 1980), and is the same age as terraces described as the Corning Terrace (Steele,

1980). The Corning Terrace has been dated at 195,000 years BP at Thomes Creek and

390,000 years BP at Elder Creek and Red Bank Creek (Steele, 1980; see figure 1). These ages are consistent with the published ages of the Riverbank Formation (Marchand and

Allwardt, 1981).

The base of the lower Riverbank Formation alluvium is exposed at the high water level on the northern shoreline of Black Butte Lake in wave cut benches west of the

Orland Buttes (see figure 14). The base of the lower Riverbank Formation alluvium is present over a conglomerate bed of the Tehama Formation in south facing stream cuts along the North Fork of Stony Creek in the western side of the study area (see figure 6, location #16). The lower Riverbank Formation alluvium north of Black Butte Lake has a thickness of up to 180 feet (55 m) on the western side of the study area (see figure 6, loc

#18) and thins to a maximum of 60 feet (18 m) north of the dam. The terrace deposit is thicker near the present valley floors and thins toward the ridges between Stony Creek and the North Fork of Stony Creek, and between the North Fork of Stony Creek and

Figure 14. Lower Riverbank Formation Terrace Deposit over Tehama Formation Claystone. Iron oxide stained gravels of the lower Riverbank Formation terrace over claystone and conglomerate of the Tehama Formation. Located in west side of cove adjacent to North Butte.

Sehorn Creek ( see cross sections C-C’ and E-E’ and figure 20). Lower Riverbank

Formation sediments occur as a fill terrace over Tehama Formation sediments north of

Black Butte Dam and between North Butte and Newville Road (County Road 200), (see

cross sections D-D’ in figure 20). This terrace is also present at the face of Black Butte

Dam and the eastern side of the Orland Buttes extending south onto the Stony Creek Fan

south of Newville Road (see figure 6). Two flat-topped hills west of the Park

Headquarters are a remnant of the top of this fill terrace (see figure 6, location #19).

The lower Riverbank Formation alluvium on the ridge between Stony Creek

and the North Fork of Stony Creek rests unconformably on Cretaceous sandstone and

shale and Tehama Formation claystone and conglomerate. Between the Stony Creek and

the North Fork of Stony Creek arms of the lake the thickness of the alluvium reaches 160 feet (49 m) south of the Burris Creek recreation area (see figure 5) and exceeds 140 feet

(43 m) north and west of the Grizzly Flat Recreation area. The alluvium decreases in thickness as the top of the underlying Tehama Formation sediments increase in elevation toward the ridge between the two arms of the lake (see cross sections E-E’ and figure 20).

North-east of the Grizzly Flat Recreation Area, the base of the lower Riverbank

Formation alluvium follows the elevation of the high water line along the shoreline toward the point between the two arms of the lake. South-west of the Grizzly Flat

Recreation Area, the base of the alluvium increases in elevation above the high water level and rests on a strath terrace on Cretaceous bedrock (see figure 6, location #3). The

base of the alluvium and the basal conglomerate are exposed on slopes north of the

Equestrian Parking Area (see figure 5 and figure 6, location #1).

On the south shore of the Black Butte Lake, the Riverbank Formation

alluvium also exceeds a thickness of 160 feet (149 m) at the western end of the lake (see

figure 6, location #20). From this location the deposit of alluvium thins to the east to

Middle Butte. Riverbank Formation sediments are present above the top of the eroded

cliffs along the lakeshore at the Orland Buttes Campground (see figure 5). West of the

Orland Buttes Campground the base of the Riverbank Formation alluvium is present in

the cliffs along the lake shore at approximately 500 feet in elevation. The lower

Riverbank Formation alluvium abruptly thickens 1 mile west of the boat ramp at the

Orland Buttes Campground as the underlying Tehama Formation pinches out (see figure

6, location #13). The deposit of lower Riverbank Formation alluvium thickens to approximately 160 feet (149 m) (see figure 6, location #20) and continues west to the edge of the study area where it pinches out against Upper Cretaceous sandstone of the

Venado Formation (see figure 6, location #21, and figure 21).

Upper Riverbank Formation

Two facies of upper Riverbank Formation alluvium are present in the study area. The common facies is highly oxidized, red to brick red (Munsell 10R 4/4 to 4/6), poorly sorted, sandy claystone with cross-bedded, pebble to cobble conglomerate (see figure 15). The alluvium of the upper Riverbank Formation has a higher level of induration than the sediments of the lower Riverbank Formation. Clasts of chert and metamorphic rocks larger than 30 cm (12 inches) in diameter are common. Calcrete is present at the contact with the underlying Tehama Formation claystone west of the boat ramp at the Buckhorn Recreation Area (see figure 6, location #17).

A second, less common facies of the upper Riverbank alluvium is present at several locations in the study area. The sediments are red to brick red (Munsell 10R 4/4 to 4/6), poorly-bedded to massive, clay and sandy clay with pebbles up to 5 cm (2 inches) in diameter. The coarse clasts are mostly angular to sub angular chert and quartz. This alluvium ranges in thickness from 1 foot to 3 feet (0.4 to 1 meters) on terraces where it covers rocks of the Tehama Formation and Great Valley Group.

Figure 15. Upper Riverbank Formation Conglomerate. Conglomerate facies of the upper Riverbank Formation exposed in wave cut cliffs on the north side of the point between the Stony Creek and North Fork of Stoney Creek arms of the lake. 1.7 meter Jacobs staff for scale.

The upper Riverbank Formation sediments occur as a layer of alluvium on a cut-in-fill terrace that formed on underlying sediments of the lower Riverbank Formation, the Tehama Formation, and as cover on a strath terrace on rocks of the Great Valley

Group.

On the north side of the North Fork of Stony Creek the terrace is elevated above the Modesto Formation terrace by approximately 25 feet (7.5 m) at the Buckhorn

Recreation Area (see figure 5). The terrace rises in elevation to the west to

approximately 60 feet (18 m) above the Modesto Formation terrace at the western side of

the study area (see figure 6, location #4). On the north side of Stony Creek the terrace is

elevated above the Modesto Formation terrace by approximately 20 feet (6 m) at the

point between the two arms of the lake. The terrace reaches an elevation of 50 feet (15

m) above the Modesto terrace north of the Equestrian Parking Area (see figure 6, location

#1). On both the Stony Creek and the North Fork of Stony Creek the upper Riverbank

Formation terraces are prominent on the northern side of the modern valley. On the

southern side of both stream valleys the terrace has been removed by erosion but

remnants of the terrace are present at a few locations. This terrace is elevated

approximately 25 feet (7.6 m) above the valley floor south and east of the study area at

the Graves Cemetery at the intersection of Newville Road and County Road 206 (see

figure 6, location #22). This terrace is also present east of the Orland Buttes on both

sides of Hambright Creek along County Road 206 (see figure 6, location #23). The upper

Riverbank Formation terrace deposits were named the Perkins Terrace by Steele (1980).

Modesto Formation

Pleistocene Modesto Formation sediments occur as alluvium covering terraces

that are elevated above the present stream beds of Stony Creek and the North Fork of

Stony Creek on the western side of the study area. The terrace is cut into Tehama

Formation claystone and a prominent conglomerate bed of the Tehama Formation on the

North Fork of Stony Creek. The terrace is elevated 15 feet (4.5meters) above the present

stream bed of the North Fork of Stony Creek at the Newville Road Bridge. The terrace is

cut into Cretaceous rocks of the Great Valley Group on Stony Creek. North of Steuben

Bridge the terrace is elevated up to 20 feet (6 meters) above the present stream bed of

Stony Creek (see figure 6, location #3). These terraces are covered by water in the

central and eastern part of the study area and are not accessible when the lake is full.

Composite Stratigraphic Section

Detailed descriptions of the lithologic units exposed in the study area were

recorded during field surveys. A composite stratigraphic section of the lithologic units

that were observed in the study area was compiled and is presented in figure 16.

Clast Composition Surveys

Russell (1931) performed pebble counts during his survey of the area and determined that the composition of the clasts of the Tehama Formation was different from the composition of the clasts in the Red Bluff Formation alluvium. Pebble counts were performed at eight locations in the study area. The location of each of the eight pebble counts was chosen to verify conclusions of Russell (1931) and to identify and correlate sedimentary outcrops in the study area. One sample was collected from a location east of the study area as a control to represent the Red Bluff Formation. The reference sample for the Red Bluff Formation was collected from a road cut on Hwy

99W between Orland and Corning (see figure 1). This locality is an eroded remnant of the Red Bluff Pediment. This location was chosen to insure that the sample was from the

Figure 16. Composite Section of the Stratigraphic Units Observed in the Study Area.

Red Bluff Formation. The general location of the samples is plotted on a map of the

study area (see figure 17), and detailed locality information is listed in table 1.

Black Butte formation sample

A sample of conglomerate from the Black Butte formation was collected to

help in identification of the Black Butte formation in the field and for comparison with the other clast composition samples. Sample #10 was collected from an exposure of

conglomerate above lake high water level on the south side of North Butte (see figure 17,

location #10). A pie chart was compiled to illustrate the composition of the clasts in the

sample (see figure 18). Quartzite is the most common clast type and is approximately

44% of the sample. Conglomerate is 18% and Sandstone and greywacke are

approximately 19% of the sample. Chert is 10.5% of the sample, intrusive and extrusive

igneous rocks are 11.3%, and greenstone is 6.3%. Quartz diorite, metamorphic quartz and

schist are absent.

Tehama Formation samples

Three samples (#5, #6, and #8) were collected from conglomerate beds in

alluvium mapped as Tehama Formation by previous researchers and identified as the

Tehama Formation during field surveys. The location of each sample is plotted on a map

of the study area (see figure 17), and is recorded in table 1. Sample #8 was collected

from a gravel conglomerate below the lower Riverbank Formation alluvium on the north

side of Black Butte Lake. The sample was collected from the west side of a gully located

Figure 17. Map of the Study Area Showing Location of Clast Composition Surveys/Pebble Counts.

west of the boat ramp at the Buckhorn Recreation Area. Samples #5 and #6 were collected from gravel conglomerate on the south side of Black Butte Lake at the end of

County Road 206 west of the Orland Buttes Campground. Sample #5 was collected from a conglomerate bed at high water level that was located above an unconformity in the

Tehama Formation. Sample #6 was collected from a conglomerate bed 20 feet (6 m)

below the unconformity at the same general location. The stratigraphic position of both

samples is noted on the measured section of the Tehama Formation (see figure 10).

A composite sample was produced from the calculated average of the three

samples (see figure 18). Pie charts of individual samples were compiled for comparison

(Appendix 1, figure 2). Sandstone and greywacke are the most common clasts

composing approximately 50% to 60% of the samples. Metamorphic quartz and

greenstone are the next most common clasts at around 15%. Chert and vein quartz

collectively make up approximately 13% to 15 % of the sample. Metamorphic rhyolite is

5% of the sample. Metamorphic conglomerates are 1.5% of the sample.

The standard deviation and range was calculated for the clast types from each

sample. Chert had a standard deviation from (0.1 to 1.1) and a range (0.7 to 2.3) showing

that the distribution of colored chert varied despite the small sample size. Rock types

from the Franciscan Complex had a range (1.5 to 2.9) and standard deviation values from

(1.1 to 1.5) schist and metamorphic quartz, and a range (11.2) and a standard deviation of

(5.7) for greywacke/sandstone. The higher standard deviation for greywacke/sandstone is

likely due to varying contribution of clasts from the Franciscan complex and the Great

Valley Group. Greenstone and serpentine showed the highest variation in the samples

with a range (11.2) and a standard deviation (5.9). The similarity of range and standard

deviation of greenstone, serpentine and sandstone/greywacke is likely due to contribution

of clasts from a similar source area in the Franciscan Complex and the Coast Range

Ophiolite.

Figure 18. Pie Charts of the Relative Composition of the Clasts in the Lithologic Units.

Table 1 Table of Clast Composition Survey/Pebble Count Locations.

Red Bluff Formation sample

Sample #3 was collected from a road cut on Hwy 99 West, five miles south of

Corning (see figure 1 and table 1). The sample was collected to provide a reference for

comparison with Riverbank Formation samples in the study area. A pie chart was

compiled to illustrate the composition of the clasts in the sample (see figure 18). Chert is

the most common clast type and is approximately 25% of the sample. Sandstone and

greywacke are approximately 21% of the sample. Metamorphic quartz also compose

approximately 21% of the sample. Greenstone is 13% of the sample and vein quartz is

10% of the sample. Metamorphic conglomerate is 4%, and metamorphic rhyolite is 1% of the sample.

Riverbank Formation samples

Five samples (#1, #2, #4, #7, and #9) were collected from conglomerate beds

in areas recognized as Riverbank Formation by previous researchers or identified as

Riverbank Formation alluvium during field surveys. The location of each sample is

plotted on a map of the study area (see figure 17) and is recorded in table 1. Sample #1

was collected from the north side of a road cut east of the intersection of Newville Road

and Black Butte Road. Sample #2 was collected from a road cut through a terrace

deposit along Newville Road north of the infiltration ponds below the dam. Sample #4

was collected from a road cut at a saddle on County Road 200A on the south side of the

lake near the western side of the study area. Sample #7 was collected from the west side

of a gully west of the boat ramp at the Buckhorn Recreation Area. Sample #9 was

collected from a road cut on Newville Road south and east of the study area (figure 17).

Table 2. Table of Clast Composition Survey/Pebble Count Results. Table of results of pebble counts/clast composition surveys with results including calculated percentages, Range, and Standard Deviation of the clasts in the sample. Clasts descriptions were chosen to aid in identification of the source area for the sediments.

A composite sample was produced from the calculated average of the five

samples (see figure 18). Pie charts of individual samples were compiled for comparison

(see Appendix A, figures 1 and 2). Sandstone and greywacke are the most common clasts composing approximately 37% of the samples. Metamorphic quartz and greenstone are the second most common clasts at 11% and 16% respectively. Chert at

9% and vein quartz at 4% collectively make up approximately 13% of the samples.

Metamorphic rhyolite is 1.6%. Metamorphic conglomerate is less than 1%.

The standard deviation and range was calculated for the clast types from each sample. Chert had a standard deviation from (1.0 to 2.0) and a range (3.3 to 3.5) showing that the distribution was relatively constant in the samples. Rock types from the

Franciscan Complex had a similar range (8.1) and standard deviation values from (3.9) for schist and metamorphic quartz to (6.3) for greywacke/sandstone. The higher standard deviation for greywacke/sandstone is likely due to varying contribution of clasts from the

Franciscan Complex and the Great Valley Group. Greenstone and serpentine showed the highest variation in the samples with a range (36.1) and standard deviation (13.1), this is likely due to varying contribution of clasts from the Franciscan Complex and the Coast

Range Ophiolite.

Comparison of samples

Quartz, chert, and metamorphic rocks that have a greater resistance to erosion

were more common in the Riverbank Formation than in the Tehama Formation. These

rocks are have an origin from the Franciscan Complex and the Coast Range Ophiolite.

Greywacke sandstone and conglomerate were less common in the Riverbank Formation

than in the Tehama Formation. These rocks have an origin from the Franciscan Complex or the Great Valley Group. The Riverbank Formation samples show a higher concentration of clasts from the Franciscan Complex and the Coast Range Ophiolite than the Tehama Formation samples.

Quartz, chert, and metamorphic rocks that have a greater resistance to erosion were more common in the Red Bluff Formation sample than in the Tehama Formation or

Riverbank Formation samples. These rock types are representative of an origin from the

Franciscan Complex or the Coast range Ophiolite. Greywacke sandstone and conglomerate were less common in the Red Bluff Formation sample than the Tehama

Formation or Riverbank Formation samples. These rock types can be representative of an origin from the Franciscan Complex or the Great Valley Group. The Red Bluff

Formation sediments have a higher concentration of clasts from the Franciscan Complex and the Coast Range Ophiolite than the underlying Tehama Formation or the overlying

Riverbank Formation.

The gravel clasts from the Black Butte formation showed an association with the Sierra Nevada Mountains or Klamath Mountains (52% of the clasts), and the

Franciscan Complex and the Coast Range Ophiolite (48% of the clasts). Quartz diorite, metamorphic quartz and schist from the Franciscan Complex were absent from the sample. The assumption that the Franciscan Complex contributed sediment to this unit may be incorrect, the rocks may come from ophiolites and subduction complexes in the

Sierra Nevada or Klamath Mountains.

CHAPTER IV

SUBSURFACE DISTRIBUTION OF STRATIGRAPHIC UNITS

Introduction

An updated geologic map of the study area was compiled after field surveys

were completed. The geologic map was drafted onto the U.S. Geological Survey (USGS)

Black Butte Dam, Sehorn Creek, Fruto, and Julian Rocks, 7.5 minute (1:24,000 scale)

quadrangles. Previous geologic maps produced by Steele (1981); Blake et al. (1982), and

Helley and Harwood (1985), were reviewed prior to compilation of the geologic map. In

many cases the areal extent of the outcrops described by previous researchers were

revised based on observation of the outcrops in the field area. The description of the

stratigraphic units were also revised based on the new interpretation of the sedimentary

deposits. Cross-sections were compiled at five locations to describe the subsurface

distribution of the sedimentary deposits in the study area (see figure 19).

Geologic Cross Sections

Cross section A-A´ (figure 20) is a northeast to southwest section that

parallels the lake shore on the south side of Black Butte Lake. On the western slope of

Middle Butte the Cretaceous Guinda Sandstone is covered by talus eroded from the overlying Lovejoy Basalt. Tehama Formation sediments are present above the talus of

basalt on the western slope of Middle Butte. An upper Riverbank Formation terrace

Figure 19. Map of the Study Area Showing the Location of Cross Sections.

deposit is present just above the high water level at the foot of Middle Butte. Tehama

Formation sediments are at the base of most of the section but pinch out about a mile east of the Orland Buttes Campground. A fill terrace of lower Riverbank Formation alluvium approximately follows the 500 foot elevation contour. The lower Riverbank Formation alluvium thickens abruptly in the western side of the section where the underlying

Tehama Formation sediments pinch out. This lower Riverbank Formation alluvium

unconformably overlies an erosional dip slope that was formed on the Cretaceous bedrock to the west (see figure 21) and a buttress unconformity in the Tehama Formation.

Cross section B-B´ (figure 20) is an east-west section across a high bluff east of the Orland Buttes Campground. Oxidized sand and gravel of the lower Riverbank

Formation fill terrace unconformably overlies the Tehama Formation claystone. The prominent gravel conglomerate of the Tehama Formation is exposed at the elevation of the high water level of Black Butte Lake.

Cross section C-C´ (figure 20) is a south-north section that extends from the boat ramp at the Buckhorn Recreation Area to a road cut at the intersection of Newville

Road and Black Butte Road. This section shows the sloping surface of the top of the

Tehama Formation claystone at the base of the lower Riverbank Formation fill terrace.

An upper Riverbank Formation cut-in-fill terrace is present below lake level on the southern side of the section.

Cross section D-D´ (figure 20) is a south-north cross section that was drawn approximately 100 feet (30 m) west of the overflow spillway entrance at the north side of

Black Butte Dam. The Lovejoy Basalt and Black Butte formation dip to the north and east. Black Butte formation sediments unconformably overly sandstone and shale of the

Forbes Formation. The Black Butte formation alluvium is approximately 65 feet (20 m) thick at this location. A fill terrace of lower Riverbank Formation alluvium overlies sediments of the Tehama Formation on the north side of North Butte. The broken line on the north side of North Butte shows the approximate location of the talus covered slope that formed on the side of the table mountain before the Tehama Formation was

deposited. The top of the flow of Lovejoy Basalt is below the approximated elevation of

the top of the Red Bluff Pediment where this cross section was compiled.

Cross section E-E´ (figure 20) is a northwest-southeast section across a part of the peninsula between the two arms of the lake. The section shows the unconformity between the Riverbank Formation conglomerate and the Tehama Formation claystone.

The sloping surface at the top of the Tehama Formation is the southern side of an early

Pleistocene ridge that existed between Stony Creek and the North Fork of Stony Creek.

A fill terrace of lower Riverbank Formation alluvium is present above the sloping surface at the top of the Tehama Formation. An upper Riverbank Formation cut-in-fill terrace is exposed below lake level on the southern side of the section.

Figure 20. Cross Sections Compiled from Field Surveys. 71

CHAPTER V

DISCUSSION OF RESULTS

Outcrops of the Tehama Formation in the study area are not as extensive as mapped by previous researchers. The primary reason for the discrepancy between the extent of the actual exposures and the mapped exposures is that the original mapping of the region was not complete. Russell (1931, pg. 29) explained that there were large areas of his map that were covered by Red Bluff Gravels but he had insufficient time to accurately map these exposures. Russell also failed to recognize the significance of a unit of alluvium on the northern slope of North Butte. This alluvium occurs below the

Lovejoy Basalt and is not part of the Tehama Formation.

Field surveys that were conducted as a part of this study revealed that sedimentary rocks of the Tehama Formation were removed during a period of erosion during the middle Pleistocene. Ancestral Stony Creek, the North Fork of Stony Creek,

and smaller streams incised valleys into the deposits of the Tehama Formation in the field area and north to Thomes Creek (see figure 12). In addition, Tehama Formation sediments have been completely removed by erosion from portions of the west side of the field area.

The most common facies of the rocks of the Tehama Formation in the study area is green to tan claystone and silty claystone. Claystone beds are exposed in wave cut cliffs and benches at the high water level on the south shoreline of the lake, as shallow

sloping hills north of the lake, and in the beds of streams that drain the hills around the lake. Russell (1931) explained that caliche was common in the lower part of the Tehama

Formation. Caliche is common in the claystone below a prominent conglomerate bed and below the high water level of the lake. Caliche is present in the claystone as pedogenic caliche, nodular caliche, root casts, and as veins of calcrete deposited between or capping the beds of claystone. The abundant caliche and a sequence of oxidized claystone beds near the base of the Tehama Formation on the south shore of the lake suggest that the climate was hotter and drier when the lower part of the Tehama Formation was deposited.

The second facies of the Tehama Formation is a bed of pebble conglomerate which is exposed at the approximate elevation of the high water level of the lake. The conglomerate bed dips to the east, foresets in the crossbeds also dip to the east. Outcrops of the conglomerate are continuous on the north shoreline of the Black Butte Lake. The conglomerate underlies the wide valley of the North Fork of Stony Creek in the study area and many of the streams valleys north of the study area. South of Stony Creek the conglomerate is present in cliffs along the south shoreline of the lake where the outcrop is discontinuous and thins to the west toward the mountains. Wide valleys and flat terraces are formed on the top of the conglomerate, steep slopes and cliffs are formed when streams erode through the conglomerate. Gravel that has been eroded from the conglomerate bed and the overlying Riverbank Formation covers the shoreline of the lake below high water level and obscures the underlying claystone in many areas. The conglomerate underlies the fill terraces of the lower Riverbank Formation, the cut-in-fill

terraces of the upper Riverbank Formation, and is the bedrock upon which Modesto

Formation sediments have been deposited in the modern stream beds.

This conglomerate was deposited over an unconformity in the Tehama

Formation. The claystone beds above this unconformity have an attitude that is similar to

the conglomerate. Below the conglomerate the dip of the claystone beds varies from 2 to

4 degrees steeper to the east than the overlying conglomerate. The variation in the dip of

the beds below this unconformity suggests that there was a period of uplift and erosion in

the study area during the Pliocene. An unconformity in the Tehama Formation sediments

in the study area should not be a surprise for two reasons. First, there would likely be

small scale unconformities along the margin of a depositional basin as streams meander

across the valley floor. Also, the Orland Buttes would likely deflect the relict streams resulting in erosion along the sides of the buttes. A large scale unconformity in the

Tehama Formation would be unexpected.

Tehama Formation claystone is present as perched terraces on the west slope of Middle Butte. The perched terraces reach elevations of 560 feet above sea level (70 feet above the shoreline of the lake) and may reach elevations of over 600 feet east of the

Orland Buttes Campground. These terraces are evidence that a large thickness of the

Tehama Formation was removed by erosion during the late Pliocene or early Pleistocene.

The Nomlaki Tuff was not seen in situ during field surveys, nor were clasts of tuff present in modern stream beds. Tuffaceous clasts were present at one location in an upper Riverbank Formation terrace deposit on the south side of the lake. South of the study area the Nomlaki Tuff is present at elevations of 600 to 700 feet above sea level

which is 200 feet above the base of the outcrop of the Tehama Formation in the study

area. Previous researchers have described outcrops of the Nomlaki Tuff north-west of the study area. These exposures occur at approximately 700 to 800 feet in elevation. The

Nomlaki Tuff that was present in the study area was at an elevation above the present ground surface and was most likely removed by erosion during the early Pleistocene.

Tehama Formation sediments pinch out along an unconformity on the Stony

Creek arm of the lake. One mile west of the Orland Buttes Campground on the south

shoreline, and west of the Grizzly Flat Recreation Area on the north shoreline Tehama

Formation sediments are absent and Pleistocene alluvium rests directly on bedrock of

Cretaceous sandstone and shale (see figure 21). Two explanations for this abrupt

thinning would be increased erosion at the mountain front resulting in removal of the

Tehama Formation sediments and exposure of the underlying Cretaceous rocks (see

figure 21). Also, erosion of relict stream valleys would have removed the Tehama

formation sediments causing a thinning of the deposit of Tehama Formation rocks on the

valley floor.

Clasts of Lovejoy Basalt are present in two claystone beds of the Tehama

Formation on the western slope of Middle Butte. Caliche coats the Lovejoy Basalt clasts

and is also common in the sediments. The basalt clasts are identical to basaltic talus that

covers the eroded slope of Middle Butte in the vicinity of the outcrop. The basalt clasts

show that the Tehama Formation claystone was deposited against the western slope of

Middle Butte. This contact is a buttress unconformity, previous researchers have proposed that there was a reverse fault at this location that facilitated the uplift of the

Orland Buttes during the Pliocene (Russell 1931). If the contact were a fault, then the

Lovejoy Basalt clasts would not be present in the claystone of the Tehama Formation.

Figure 21. Buttress Unconformity in the Tehama Formation. Buttress Unconformity in the Tehama Formation East of Middle Butte and Comparison to the Western Side of the Study Area. This provides an explanation for the missing Tehama formation sediments and the thick deposit of Riverbank Formation gravels.

Russell (1931) mapped alluvium on the north slope of North Butte as a part of the Tehama Formation. Outcrops in two gullies north of the coffer dam on the north side of North Butte were investigated during field surveys. These sediments contain clasts of oxidized quartzite, and plutonic rocks that are related to a source in the Klamath

Mountains or the Sierra Nevada Mountains. These clasts show that the sediments on the north side of North Butte are part of the Black Butte formation. The sediments are also in a stratigraphic position that is below the Lovejoy Basalt. Hancock et al., (1986) determined that the age of these sediments is Oligocene to early Miocene based on the stratigraphic position of the unit below the Lovejoy Basalt. Pollen analysis also suggests an Oligocene or Miocene age (Personal communication L. Fisk, 2015). Terrestrial alluvium below the Lovejoy Basalt has been correlated with various units by previous researchers including the Eocene age Nord Formation of Van Den Berge (1968).

Conglomerate and sandstone below the Lovejoy Basalt at Oroville Table Mountain was correlated with the Nord Formation (Street, 2009). The Black Butte formation is

Oligocene or Early Miocene so it is not the Nord Formation and is likely a new stratigraphic unit that occurs below the Lovejoy Basalt.

Exposures of the Red Bluff Formation and the Red Bluff Pediment are not as extensive as mapped by previous researchers. Early maps of the study area and the west side of the Sacramento Valley did not accurately represent the extent of the Red Bluff

Formation gravels. The Red Bluff Pediment was formed as during a period of uplift of the Coast Ranges in the early Pleistocene. In many parts of the Sacramento Valley the

Red Bluff Pediment has been completely removed by erosion, in some areas only

dissected remnants of the pediment remain. During the middle Pleistocene, the western

edge of the Red Bluff Pediment was eroded by ancestral Stony Creek and the North Fork

of Stony Creek in the study area. Large portions of the western side of the Red Bluff

Pediment and underlying Tehama Formation alluvium were removed at this time.

Remnants of this middle Pleistocene erosional surface can be seen north of the

study area as a terrain of low rolling hills between Stony Creek and Thomes Creek to the

north. The terrain between the town of Tehama and the Glenn County line was described

by Bryan (1923) as “…a series of more or less detached knolls and ridges. Below the

rolling summits which give the plainlike character to the region are narrow flat-bottomed

valleys of the tributary streams, from 1 to 4 miles apart…”. This description refers to a

region north of the study area and east of Interstate Highway 5. North of the study area

and west of the Interstate Highway 5 the incision of the Pediment is more pronounced.

(see figure 12).

Topographic contours of the top of the pediment surface were mapped by

Steele (1980), and were extended south into the study area (see figure 22). The pediment did butt up against the sides of South Butte and Middle Butte. The sloping surface at the

top of the eastern side of North Butte, and at observation point on the south side of the

dam lie below the estimated elevation of the Red Bluff Pediment Surface and would have

been covered by the Red Bluff and possibly Tehama Formation sediments. At these

locations the Red Bluff gravels and Tehama Formation sediments were removed by

erosion during the middle Pleistocene. There are no exposures of the Red Bluff

Formation gravels overlying the Tehama Formation west of Black Butte Dam.

Figure 22. Map of the Extent of the Red Bluff Pediment. Map shows dissected remnants of the red Bluff Pediment (red) and elevation contours of the top of the Red Bluff Pediment compiled by Steele (1980), (solid line) extended into the study area (dashed line). The elevation of the pediment on the Orland Buttes circled in red. Sources:

Blake, M.C., Jr., Helley, E.J., Jayko, A.S., Jones, D.L., and Ohlin, H.N., 1992, Geologic map of the Willows 1:100,000 quadrangle, California: U.S. Geological Survey Open-File Report 92-271, scale 1:100 000, 1 sheet, 42 p text.

Steele, W.M., 1980, Quaternary stream terraces in the northwestern Sacramento Valley, Glenn, Tehama, and Shasta Counties: U.S. Geological Survey Open-File Report OF-80-512, scale 1:62 500, 1 sheet, 157 p text.

The Riverbank Formation alluvium and the Red Bluff Formation gravels have

similar lithology and a similar appearance. The Riverbank and Red Bluff Formations are

both composed of sandy gravel conglomerate, both are highly oxidized and are stained with iron oxide. The alluvium of the two units is similar in appearance, the primary criteria used to identify outcrops in the study area was the stratigraphic position of the

gravels. Riverbank Formation alluvium is present at elevations below the Red Bluff

Pediment. Deposits of iron oxide stained sand and gravel that were mapped as Red Bluff

Formation gravels by Russell (1931), Helley and Harwood (1985), and Blake et al.,

(1992) lie at an elevation that is below the sloping surface of the Red Bluff Pediment.

These iron oxide stained gravels are middle Pleistocene age alluvium and they correlate with the Riverbank Formation of Davis and Hall (1959), and Marchand and Allwardt

(1981).

The lower Riverbank Formation was deposited as alluvial fans close to the

Coast Ranges and as fill terraces in the middle Pleistocene valleys of Stony Creek and the

North Fork of Stony Creek. Flat terraces are present at the top of the eroded remnants of the alluvial fill at many locations north and east of the study area. The deposits of lower

Riverbank Formation alluvium are thicker near the modern valley floors of Stony Creek

and the North Fork of Stony Creek and thin toward the ridges that flank the valleys

showing that the alluvium was deposited onto the previously existing topography of the relict stream valleys. The lower Riverbank Formation alluvium directly overlies

Cretaceous bedrock on both sides of Stony Creek in the western part of the study area.

The thick deposit of the Riverbank Formation alluvium, and the absence of the Tehama Formation at the western side of the study area is a result of erosion of

Tehama Formation alluvium in the middle Pleistocene. A sloping surface was formed on the rocks of the Great Valley Group as the Tehama Formation sediments were eroded.

The Tehama Formation sediments thicken abruptly at the downslope side of this erosional surface and continue to thicken to the east. Alluvium of the Riverbank

Formation was later deposited over this sloping surface. A modern example of this topography can be seen between Newville Road and Middle Butte (south of location #6 in figure 6). Tehama Formation and Riverbank Formation alluvium have been removed by erosion down to Cretaceous bedrock along an east dipping slope. Tehama Formation and Riverbank Formation sediments thicken abruptly just east of this sloping surface (see figure 21).

Lower Riverbank Formation alluvium is present as dissected alluvial fans and terraces on the Stony Creek Fan and along the eastern slope of the Orland Buttes. These deposits of lower Riverbank Formation gravels have been misidentified by many previous researchers as Red Bluff Formation gravels. A prominent alluvial fan east of

South Butte between Hambright Creek and the South Fork of Walker Creek which has been described as Red Bluff Formation gravels is a deposit of lower Riverbank

Formation alluvium (see figure 6). This interpretation is based on the following observations: the terrace is lower in elevation than the Red Bluff Pediment, there are no

Mima mounds present at the top of the terrace, there is an upper Riverbank Formation terrace on the edges of this alluvium along Hambright Creek, and the slope of the

dissected alluvial fan is steeper, approximately 80 ft/mile to the southeast, than the slope of the Red Bluff Pediment which is approximately 40 ft/mile to the east on the north side

of Stoney Creek.

The composition of the clasts in the Tehama Formation and the Riverbank

Formation show that there were changes in the source area for the sediments from the

Pliocene to the Pleistocene. There are decreasing amounts of greywacke and

conglomerate and increasing amounts of clasts from the Franciscan Complex and Coast

Range Ophiolite during this time.

The change in clast composition is likely a result of increased erosion of the

Franciscan Complex as uplift of the Coast Ranges continued through time. In the

Pliocene, the Coast Ranges were lower in elevation and the streams were smaller. Rocks

from the Great Valley Group contributed a higher quantity of sediment to the streams

than the Franciscan Complex. As uplift continued into the Pleistocene and the Coast

Ranges increased in elevation, the streams increased in size and rocks of the Franciscan

Complex and Coast Range Ophiolite contributed larger amounts of sediment to the

streams.

The Orland Buttes are an eroded table mountain that is similar to Table

Mountain north of Oroville. Oligocene to Miocene alluvium unconformably overlies

Mesozoic marine sandstone and shale below the basalt that caps the buttes. The flows of

Lovejoy Basalt were eroded into a series of plateaus and buttes during the formation of

the middle to late Miocene upper Princeton Valley. Seismic reflection surveys have

shown that similar structures exist beneath the Sacramento Valley and have up to 400 feet

(120 m) of relief (McManus et al., 2014). Surface exposures of the Lovejoy Basalt occur

at a two locations approximately 10 miles to the south of the study area. These outcrops

are likely the tops of buried table mountains.

The rocks of the Great Valley Group are the bedrock in the study area. The

sequence of Cretaceous rocks exposed in the study area is similar to the sequence

described in the Lodoga Quadrangle south of the study area (Brown and Rich, 1961).

The topography of the study area is also similar to the area described by Brown and Rich

(1961), with a ridge formed on the Guinda Sandstone and Forbes sandstone, and a wide

valley with low relief west of the ridge that is underlain by the Yolo Shale and Venado

Sandstone.

The Venado Sandstone is exposed in modern stream cuts along Stony Creek at

Steuben Bridge on the western side of the study area. Bedded sandstone and shale are

visible in a late Pleistocene strath terrace north of Steuben Bridge. East of the Equestrian

Parking Area sandstone was observed in two stream beds. Shale that was reported north

of the Grizzly Flat Recreation area is on private land and was not observed during field

surveys. This shale is likely also from the Venado Sandstone but may be the Yolo Shale.

The series of Upper Cretaceous rocks that are exposed at the Orland Buttes on the eastern

side of the study area are well documented. The Forbes Sandstone, Dobbins Shale, and

Guinda Sandstone are exposed along the shoreline of the lake and underlie the Orland

Buttes. The Sites Formation and Yolo Formation may be present in the study area but were not observed in outcrop during field surveys.

The topography of the western side of the Sacramento Valley shows a trend of greater uplift to the south. Researchers have interpreted this pattern of uplift as a result of the northward migration of the Mendocino Triple Junction (Dickinson and Snyder, 1979;

Harwood and Helley, 1987; Locke et al., 2006), and thrust wedging of Franciscan

Complex rocks into or under the Great Valley Group (Uhruh and Moores, 1992; Unruh et al., 1991). A result of this uplift has been increased erosion of the Mesozoic rocks of the

Great Valley Group and removal of the Cenozoic sedimentary rocks that may have overlain the rocks of the Great Valley Group. The Orland Buttes are a remnant of this sedimentary sequence on the eastern flank of the Coast Ranges. The flow of Lovejoy

Basalt and the armored slopes of the Table Mountains are likely the only reason that this topography and geology have been preserved.

I did intend to include a discussion of the structural framework of the region and the structural features of the study area. The discussion of the structural features of the region in; Hancock et al., (1986), “Black Butte Lake Stony Creek California,

Geologic and Seismic Investigation”, by the U.S. Army Corps of Engineers, is more detailed than would have been possible in this study.

REFERENCES

REFERENCES.

Alkire, J.H., 1962, Willows-Beehive Bend gas field, California, in Bowen, O.E., Jr., ed., Geologic guides to the gas and oil fields of northern California: California Division of Mines and Geology Bulletin 181, p. 105-109.

Arkley, R. J., 1954, Soils of eastern Merced County: California University Agricultural Experimental Station, Soil Survey, no. 11, 17l/. p.

Arkley, R. J., 1962, The geology, geomorphology, and soils of the San Joaquin Valley in the vicinity of the Merced River, California in Geologic guide to the Merced Canyon and Yosemite Valley: Calif. Div. Mines and Geology Bull. 182, p. 25-31.

Arkley, R.J., 1964, Soil survey of the eastern Stanislaus area, California: U.S. Department of Agriculture, Soil Conservation Service, 160 p.

Anderson, F.M., 1938, Lower Cretaceous deposits in California and Oregon: Geological Society of America, Special Paper 16, p 1-331.

Anderson, C.A., and Russell, R.D., 1939, Tertiary formations of northern Sacramento Valley, California: California Journal of Mines and Geology, v. 35, no. 3, p. 219- 253.

Atwater, T., 1970, Implications of plate tectonics for the Cenozoic tectonic evolution of western North America: Geological Society of America, Bulletin v. 81, n. 11 p. 3513- 3536.

Atwater, T., Molnar, P., 1973, Relative motion of the Pacific and North American plates deduced from sea-floor spreading in the Atlantic, Indian, and South Pacific Ocean, in Proceedings of the conference on tectonic problems of the San Andreas fault system: Stanford, Calif., Stanford University Publications in Geological Sciences, v. 13, p. 136-148.

Bailey, E.H., Irwin, W.P., and Jones, D.L., 1964, Franciscan and related rocks and their significance in the geology of western California. California Div. Mines and Geology Bulletin 183, 177 p.

Bartow, J.A., 1991, The Cenozoic evolution of the San Joaquin Valley, California: U.S. Geological Survey Professional Paper 1501, 40 p.

Blake, M.C., Jr., Helley, E.J., Harwood, U.S., W.P., Irwin, Jayko, A.S., and Jones, D.L., 1992, Geologic map of the Red Bluff 30’X60’ quadrangle, California: U.S. Geological Survey Geological Investigation Series Map I-2542, scale 1:100 000, 1 sheet.

Bailey, E.H., Irwin, W.P., and Jones, P.L., 1964, Franciscan and related rocks and their significance in the geology of western California: California Division of Mines and Geology Bulletin 183, 177 p.

Blake, Jr., M.C., Irwin, W.P., and Coleman, R.G., 1967, Upside-down zonation, blueschist facies, along a regional thrust in California and Oregon: U.S. Geological Survey Professional Paper 575-C, p. C1-C9.

Bailey, E. H., Blake Jr, M. C., & Jones, D. L. 1970. On-land Mesozoic oceanic crust in California coast ranges. US Geological Survey Professional Paper, 700, C70-C81.

Blake, Jr., M.C., Howell, D.G., and Jones, D.L., 1982, Preliminary tectonostratigraphic terrane map of California: U.S. Geological Survey Open-File Report 82-593, 9 p.

Brown, R.D., and Rich, E.I., 1961, Geologic map of the Lodoga quadrangle, Glenn and Colusa Counties, California: U.S. Geological Survey, Oil and Gas Investigations Map OM-210, scale 1:48 000, 1 sheet.

Bryan, K., 1915, Groundwater for Irrigation in the Sacramento Valley, California: U.S. Geological Survey Water-supply Paper 375A, 49 p.

Bryan, K., 1923, Geology and groundwater resources of the Sacramento Valley, California: U.S. Geological Survey Water-supply Paper 425, 285 p.

Busby, C.J., Garrison, N.J., Gans, P.B., and Wagner, D.L., 2004, Mid-Miocene tholeiitic basalt in the ancestral Cascades Arc; geology, volcanology and geochronology of the Lovejoy Basalt: Geological Society of America Abstracts with Programs. v. 36, 97p.

Busacca, A.J., 1982, Geologic history and soil development, northeastern Sacramento Valley, California: Davis, University of California, Ph.D. thesis, 348 p.

Busaca A.J., 1989, Late Cenozoic stratigraphy of the Feather and Yuba Rivers area, California, with a section on soil development in mixed alluvium at Honcut Creek: U.S. Geological Survey, Bulletin 1590-G, 132 p.

California Geological Survey, 2002, California Geomorphic Provinces, Note 36, California Geological Survey, Sacramento, CA, U.S.A., 3 p.

Chuber, S., 1961, Late Mesozoic stratigraphy of the Elk Creek-Fruto area, Glenn County, California: Ph.D. dissertation, Stanford University. 115 pp. plus maps.”

Costenius, N. K., Johnson, R,A., Dickenson, W.R., Williams, T., 2000, Tectonic evolution of the Jurassic-Cretaceous Great Valley forearc, California: Implications for the Franciscan thrust-wedge hypothesis: Geological Society of America Bulletin, vol. 112, no. 11, p. 1703-1723.

Creely, R. S., 1965, Geology of the Oroville quadrangle, California: Calif. Div. Mines and Geol. Bull 184, 86 p.

Crook, T.H., and Kirby, J.M., 1935, Capay Formation: Geological Society of America Proceedings for 1934, p. 334-335

Dalrymple, G.B., 1964, Cenozoic chronology of the Sierra Nevada, California: University of California Publications in Geological Sciences, v. 77, 41 p.

Davis, G.H., and Hall, F.R., 1959, Water quality of eastern Stanislaus and northern Merced Counties, California: Stanford University Publications, Geological Sciences, vol. 6, no. 1, p. 1-56.

Dickinson, W.R., and Rich, E.I., 1972, Petrologic intervals and petrofacies in the Great Valley Sequence, Sacramento Valley, California: Geological Society of America, Bulletin v. 83, p. 3007- 3024.

Dickinson, W.R., and Seely, D.R., 1979. Structure and stratigraphy of forearc regions. American Association of Petroleum Geologists, Bulletin 63, p 2-31.

Dickinson, W.R., and Snyder, W.S., 1979a, Geometry of triple junctions related to the San Andreas transform: Journal of Geophysical Research, v. 84, p. 561-572.

Diller, J.S., 1894, The Tertiary revolution in the topography of the Pacific coast: U.S. Geological Survey Fourteenth Annual Report, part II, p. 397-434.

Diller, J. S., 1894, Revolution in the topography of the pacific coast since the Auriferous Gravel period: The Journal of Geology, The University of Chicago Press, v 2, no. 1, p. 32-54.

Diller, J.S., 1906, Description of the Redding quadrangle, California: U.S. Geological Survey Geologic Atlas of the United States, Redding folio, no. 138, 14 p., scale 1:125,0001 sheet 14p text.

Dorf, E., 1933, Studies of the Pliocene paleobotany of California: Carnegie Institution of Washington, no.412, p. 1-108.

Durrell, C., 1959, The Lovejoy Formation of northern California: University of California Publications in Geological Sciences, v. 34, p. 193–220.

Everdeen, J.F., Savage, D.E., Curtis, G.H., and James, G.T.,1964, Potassium-argon dates and the Cenozoic mammalian chronology of North America: American Journal of Science, v. 262, no. 2. p 145-198.

Evitt, W.R., and Pierce, S.T., 1975, Early Tertiary ages from the coastal belt of the Franciscan Complex, northern California: Geology, vol. 3, no. 8, p.433-436.

Garrison, N.J., Busby, C.J., Gans, P.B., Putirka, K., and Wagner, D.L., 2008, A mantle plume beneath California? The mid-Miocene Lovejoy flood basalt, northern California: in Wright, J.E., and Shervais, J.W., eds., Ophiolites, Arcs, and Batholiths: A Tribute to Cliff Hopson: Geological Society of America Special Paper 438, p 551.

Garside, L.J., Henry, C.D., Faulds, J.E., and Hinz, N.H., 2005, The upper reaches of the Sierra Nevada auiferous gold channels, California and Nevada: Nevada Bureau of Mines and Geology, MS 178, University of Nevada Reno, Reno, Nev. 28 p., in Rhoden, H.N., Steininger, R.C., and Vikre, P.G., eds., Geological Society of Nevada Symposium 2005: Window to the World, Reno, Nevada, May 2005.

Grose, L.T., 1993, Geologic map of the Westwood 15-minute quadrangle, Lassen and Plumas Counties, California: California Division of Mines and Geology Open-File Report 89-34, scale 1:62 500, 1 sheet.

Haggart, J.W., and Ward, P.D., 1984, Late Cretaceous (Santonian-Campanian) stratigraphy of the northern Sacramento Valley, California: Geological Society of America Bulletin, v. 95, no. 5. P 618-627.

Hancock, W.E., and Lawrence, V.M., 1986, Black Butte Lake Stony Creek California, Geologic and Seismic Investigation: U.S. Army Corps of Engineers, West Seattle District, 226 p.

Harding, T.P., 1962, Perkins Lake gas field, California, in Bowen, O.E., Jr., ed., Geologic guides to the gas and oil fields of northern California: California Division of Mines and Geology Bulletin 181, p.105.

Harwood, D.S., Helley, E.J., and Doukas, M.P., 1981, Geologic map of the Chico monocline and northeastern part of the Sacramento Valley, California: U.S. Geological Survey Miscellaneous Investigations Map 1-1238, scale 1:62 500, 1 sheet.

Harwood, D.S., 1984, Evidence for late Cenozoic east-west compressive tectonism in the Sacramento Valley, California: in Crouch, J.K., and Bachman, S.B., eds., Tectonics and sedimentation along the California Margin: Pacific Section, Society of Economic Paleontologists and Minerologists, San Diego, California, 1984, v. 38, p. 87-100.

Harwood, D.S., and Helley, E.J., 1987, Late Cenozoic tectonism of the Sacramento Valley, California: U.S. Geological Survey Professional Paper 1359, 98 p.

Helley, E.J., and Harwood, D.S., 1985, Geologic map of the late Cenozoic deposits of the Sacramento Valley and northern Sierran Foothills, California: Miscellaneous Field Studies Map MF-1790, scale 1:62 500, 5 sheets, 24 p. text.

Helley, E.J., and Jaworowski, C., 1985, The Red Bluff Pediment; a datum plane for locating Quaternary structures in the Sacramento Valley, California: United States Geological Survey Bulletin 1628, 24 p.

Hinds, N.E.A., 1933, Geologic formations of the Redding-Weaverville districts, northern California: California Journal of Mines and Geology, v. 29, p. 76-122.

Hull, R., Spangler, E., Teasdale, R., Hausback, B., Clynne, Michael, A, and Poletski, S., 2008, Characterization and detailed description of the Nomlaki Tuff, Northern California: Geological Society of America Abstracts with Programs, v. 40, no. 1, 93p.

Ingersoll, R.V., Rich, E.E., and Dickinson, W.R., 1977, Field guide; Great Valley Sequence, Sacramento Valley: [Field trip no. 8]: Geological Society of America, Cordilleran Section, Guidebook for Field Trips, 73rd annual meeting, Sacramento, CA, April 5-7, 1977, 72 p.

Jayko, A.S., Blake, M.C., Jr., and Harms, T., 1987, Attenuation of the Coast Range Ophiolite by extensional faulting, and the nature of the Coast Range ‘‘thrust,’’ California: Tectonics, v. 6, p. 475–488.

Jayko, A.S., and Blake Jr., M.C., 1989, Deformation of the Eastern Franciscan Belt, northern California: Journal of Structural Geology, vol. 11, no. 4, p. 375-390.

Jennings, C.W., and Strand, R.G., 1960, Geologic map of California: Olaf P. Jenkins edition, Ukiah sheet, scale 1:250 000, 1 sheet.

Jones, D.L., and Imlay, R.W., 1969, Structural and stratigraphic significance of the Buchia zones in the Colyear Springs-Paskenta area, California: U.S. Geological Survey Professional Paper 647-A, 24 p.

Jones, D.L., and Irwin, W.P., 1971, Structural implications of an offset Early Cretaceous shoreline in northern California: Geological Society of America Bulletin, v. 82, p. 815-822.

Kirby, J.M., 1943, Upper Cretaceous stratigraphy of the west side of the Sacramento Valley south of Willows, Glenn County, California: American Association of Petroleum Geologists, Bulletin v. 27, no. 3, 286p.

Knott, J.R., and Sarna-Wojcicki, A.R., 2001, Field trip guide for day C, Central Death Valley; Stop C3, Late Pliocene tephrostratigraphy and geomorphic development of the Artist Drive structural block: U.S. Geological Survey Open-file report 01-51, P. 89-116.

Lock, J., Kelsey, H., Furlong, K., and Woolace, A., 2006, Late Neogene and Quaternary landscape evolution of the northern California Coast Ranges: Evidence for Mendocino triple junction tectonics: Geological Society of America Bulletin, vol. 118, no. 9/10, p. 1232-1246.

Marchand, D.E., and Allwardt, A., 1981, Late Cenozoic stratigraphic units, northeastern San Joaquin Valley, California: U. S. Geological Survey Bulletin 1470, 70 p.

McManus, D., Stanton K., Spangler, D., 2014, Geology of the northern Sacramento Valley: California Department of Water Resources, 77 pgs.

Miller, W.L., 1966, Petrology of the Putah Tuff member of the Tehama Formation, Yolo and Solano Counties, California [M.S. thesis]: Davis, University of California, 172 p.

Olmstead, F.H., and Davis, G.H., 1961, Geologic features and ground-water storage capacity of the Sacramento Valley California: U.S. Geological Survey Water-supply Paper 1497, 241 p.

Page, R.W., 1974, Base and thickness of the post-Eocene continental deposits in the Sacramento Valley, California: U.S. Geological Survey Water-Resources Investigations Report 73-45, 16 p.

Page, W.D., Sawyer, T.L., and Renne, P.R., 1995, Tectonic deformation of the Lovejoy basalt, a late Cenozoic strain gauge across the northern Sierra Nevada and Diamond Mountains, California, in W.D. Page, Leader, Quaternary Geology along the Boundary between the Modoc Plateau, Southern Cascades, and Northern Sierra Nevada: Friends of the Pleistocene, Pacific Cell Field Trip, 368 p.

Pessagno, E. A., 1976, Radiolarian zonation and stratigraphy of the Upper Cretaceous portion of the Great Valley Sequence, California Coast Ranges: Micropaleontology, Special Publication no. 2, 95 p.

Piper, A.M., Gale, H.S., and Thomas, H.E., 1939, Geology and ground-water hydrology of the Mokelumne area, California: U.S. Geological Survey Water-Supply Paper 780, 229 p., (incl. geologic map, scale 1:63 360, 1 sheet

Redwine, L.E., 1972, The Tertiary princeton submarine valley system beneath the Sacramento Valley, California [Ph.D. dissertation]: Los Angeles, University of California, 480 p.

Russell, R. D., 1931, The Tehama Formation of northern California [Ph.D. Thesis]: Berkley, University of California, 140 p.

Russell, R.D., and Vander Hoof, V.L., 1931, A vertebrate fauna from a new Pliocene formation in northern California: University of California Publications in Geological Sciences, v. 20, no. 2, p. 11-21.

Sarna-Wojcicki, A. M., 1970, Correlation of late Cenozoic pyroclastic deposits in the central Coast Ranges of California [Ph.D. Thesis]: Berkley, University of California, 30 p.

Sarna-Wojcicki, A.M., Meyer, C.E., Bowman, H.R., Hall, N.T., Russell, P.T., Woodward M.J., and Sate, J.L., 1985, Correlation of the Rockland ash bed, a mid- Pleistocene stratigraphic marker in northern and central California and western Nevada: Quaternary Research, v.23, p. 236-257.

Shlemon, R.J., 1972, The Lower American River Area, California: A model of Pleistocene landscape evolution: California. Yearbook of the Association of Pacific Coast Geographers, v. 34, p. 61-86.

Shlemon, R.J., Horner, T., Florsheim, J., 2000, Quaternary geology of the Sacramento Area: Association of Engineering Geologists, Sacramento Section, Guidebook for Field Trip, 25 March 2000, 25 p.

Shumway, D.O., 1997, Mineral land classification of concrete-grade aggregate resources in Glenn County, California: California Department of Conservation, Division of Mines and Geology Open-File Report 97-02, 50 p.

Sims, J.D., and Sarna-Wojcicki, A.M., 1975, New and revised stratigraphic names in the western Sacramento Valley, California: in, Cohee, G.V., and Wright, W.B., Changes in stratigraphic nomenclature by the U.S. Geological Survey, 1973: U.S. Geological Survey Bulletin 1395-A, p. A50-A55.

Springhorn, S.T., 2008, Stratigraphic analysis and hydrogeologic characterization of Cenozoic strata in the Sacramento Valley near the Sutter Buttes [M.S. thesis]: Sacramento, California State University, 186 p.

Stefanov, A., 1962, The Challenge of the Sacramento Valley, in Bowen, O.E., Jr., ed., Geologic guides to the gas and oil fields of northern California: California Division of Mines and Geology Bulletin 181, p. 77-97.

Street, Q.L., 2009, Regional paleo-topographic setting of the Lovejoy Basalt, Northern California [M.S. thesis]: Chico, California State University, 139p.

Taliaferro, N.L., 1951, Geologic Guidebook of the San Francisco Bay Counties: California Division of Mines and Geology, Bulletin no. 154

Unruh, J.R., Ramirez, V.R., Phillips, S. P., and Moores, E.M., 1991, Tectonic wedging beneath fore-arch basins: ancient and modern examples from California and the Lesser Antilles: GSA Today, vol. 1, no. 9, p. 185-190.

Unruh, J.R., Loewen, B.A., and Moores, E.M., 1995, Progressive arcward contraction of the Mesozoic - Tertiary fore-arc basin, southwestern Sacramento Valley, California: Geological Society of America, Bulletin, January 1995; v. 107; no. 1; p. 38–53

Unruh, J.R., O’Connel, D., and Block, L.V., 2004, Crustal structure of the ancestral northwestern California forearc region from seismic reflection imaging: implications for convergent margin Tectonics: Tectonophysics, v. 392, p. 219-240.

U.S. Army Corps of Engineers (COE), 1963. Foundation report, Black Butte Dam, Stony Creek, California. Sacramento District, Corps of Engineers.

Van den Berge, J. C., 1968, The paleo-geomorphological features of the Lovejoy Formation in the Sacramento Valley, California [M.S. thesis]: Davis, University of California, 144 p.

Wagner, D.L. and Saucedo, G.J., 1990a, Age and stratigraphic relationships of Miocene volcanic rocks along the eastern margin of the Sacramento Valley, California in Ingersoll, R.V. and Nilson, T.H. , eds, Sacramento Valley Symposium and Guidebook: Pacific Section S.E.P.M., v. 65, p. 143-151 .

Weaver, C.E., 1949, Geology of the Coast Ranges immediately north of San Francisco Bay Region, California: Geological Society of America Memoir 35, 242 p.

Wentworth, C. M., and Zoback, M. D., 1989, The style of late Cenozoic deformation at the eastern front of the California Coast Ranges: Tectonics, v. 8, p. 237–246. White, C. A., 1885, Notes on the Mesozoic and Cenozoic Paleontology of California: United States Geological Survey Bulletin 15, 32 p.

Williams, T.A., Graham S.A., Constenius K.N., 1998, Recognition of a Santonian submarine canyon, Great Valley Group, Sacramento Basin, California: Implications for petroleum exploration and sequence stratigraphy of deep-marine strata: AAPG bulletin. v. 82, iss 8, p. 1575 -1595.

Appendix A

Appendix A, figure 1. Pie charts showing the composition of the clasts in samples of the Tehama and Riverbank formations

Appendix A, figure 2. Pie charts showing the composition of the clasts in samples of the Riverbank Formation.

Appendix B