U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2013-5127

Prepared in cooperation with the Santa Barbara County Water Agency

Construction of 3-D Geologic Framework and Textural 

Models for Cuyama Valley Groundwater Basin, California
Cover. Looking northwest from the south side of Cuyama Valley to the Caliente Range. Photograph taken by Donald S. Sweetkind, 

U.S. Geological Survey, August 2, 2011.
Construction of 3-D Geologic Framework 

and Textural Models for Cuyama Valley 

Groundwater Basin, California

By Donald S. Sweetkind, Claudia C. Faunt, and Randall T. Hanson

Prepared in cooperation with the Santa Barbara County Water Agency

Scientific Investigations Report 2013–5127

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Sally Jewell, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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Suggested citation:

Sweetkind, D.S., Faunt, C.C., and Hanson, R.T., 2013, Construction of 3-D geologic framework and textural models for 

Cuyama Valley groundwater basin, California: U.S. Geological Survey Scientific Investigations Report 2013–5127, 46 p.
iii

Contents

Abstract ......................................................................................................................................................... 1

Introduction ................................................................................................................................................... 1

Purpose and Scope ..................................................................................................................................... 2

Geologic Setting ........................................................................................................................................... 4

Stratigraphic Units .............................................................................................................................. 4

Structural Setting ................................................................................................................................ 7

Faults and the Groundwater Flow System ...................................................................................... 7

Regional Tectonics and Uplift Rates ................................................................................................ 8

Compilation of Surface and Subsurface Data ......................................................................................... 9

Surface Geologic Map Data .............................................................................................................. 9

Subsurface Data .................................................................................................................................. 9

Oil and Gas Wells ....................................................................................................................... 9

Water Wells ............................................................................................................................... 10

Interpretation of Subsurface Data.................................................................................................. 10

Oil and Gas Wells ..................................................................................................................... 10

Water Wells ............................................................................................................................... 12

Compilation of Stratigraphic Tops from Well Data ...................................................................... 12

3-D Geologic Framework Model............................................................................................................... 15

Modeling Approach........................................................................................................................... 15

Construction of Gridded Surfaces .................................................................................................. 17

Younger Allvium, Qya ............................................................................................................... 17

Older Alluvium, Qoa.................................................................................................................. 19

Morales Formation, QTm ......................................................................................................... 20

Pre-Morales Formation (QTm) Bedrock................................................................................ 21

3-D Geologic Framework Model Results ....................................................................................... 22

Textural Analysis of Basin-Filling Unit..................................................................................................... 27

Textural Variations Observed in Outcrop....................................................................................... 27

Texture Derived from Drill-Hole Data ............................................................................................. 29

Oil and Gas Wells...................................................................................................................... 29

Water Wells ............................................................................................................................... 31

2-D and 3-D Models of Textural Data ............................................................................................. 31

3-D Model of Textural Data from Oil Wells ........................................................................... 31

2-D Models of Textural Data ................................................................................................... 33

Summary....................................................................................................................................................... 39

References Cited......................................................................................................................................... 40

Appendix 1. Interpreted depth to top of geologic units in oil and gas wells, Cuyama Valley ....... 43

Appendix 2. Interpreted depth to top of geologic units in water wells, Cuyama Valley ................ 44

Appendix 3. Sediment textural characteristics interpreted from electric logs from oil and 

gas wells, Cuyama Valley ............................................................................................................ 45

Appendix 4. Sediment textural characteristics interpreted from drillers’ lithologic logs from 

water wells, Cuyama Valley ........................................................................................................ 45
iv

Figures

1. Map showing location of Cuyama Valley within the California Coast Ranges ..................... 2

2. Map showing the Cuyama Valley study area .............................................................................. 3

3. Generalized stratigraphic diagram of the Cuyama Valley study area .................................... 4

4. Map showing generalized geology of the Cuyama Valley study area .................................... 5

5. Composite electric log from the Cuyama Valley study area .................................................. 11

6. Correlation of electric logs from the central part of the Cuyama Valley study area ......... 13

7. Three-dimensional (3-D) perspective view of geologic units in water wells and oil 

and gas wells in Cuyama Valley ............................................................................................. 14

8. Diagrammatic cross section showing relative elevation of stratigraphic unit tops 

and resultant thickness within the framework model ........................................................ 16

9. Conceptualization of the elevation and thickness of unit Qoa within the geologic 

framework model for the western part of the study area .................................................. 17

10. Map showing modeled thickness of the younger alluvium, Qya ........................................... 18

11. Map showing the modeled elevation of the top of the older alluvium, Qoa ........................ 19

12. Map showing geologic data used to map the top of the Morales Formation, QTm ........... 20

13. Map showing modeled elevation of the top of the Morales Foramtion, QTm ..................... 21

14. Map showing geologic data used to map the top of the pre-Morales Formation 

(QTm) bedrock ........................................................................................................................... 22

15. Map showing modeled elevation of the top of bedrock ......................................................... 23

16. Perspective views of vertical slices through the geologic framework model .....................24

17. Cross sections showing previous hydrogeologic interpretation and elevation of 

stratigraphic unit tops from the geologic framework model. A, east-west 

section A-A’; B, north-south section B-B’ ............................................................................ 25

18. Map showing location of wells used for textural analysis in Cuyama Valley ..................... 27

19. Photographs showing outcrop expression of textural variations in basin-filling 

units: A, Morales Formation; B, Older alluvium ................................................................... 28

20. Example electric log from oil and gas well showing derivation of textural data ................ 30

21. Perspective view showing results of 3-D textural modeling from oil and gas 

well data ..................................................................................................................................... 32

22. Map showing kriged result of textural analysis for younger alluvium, Qya ........................ 35

23. Map showing kriged result of textural analysis for older alluvium, Qoa ............................. 36

24. Map showing kriged result of textural analysis for the Morales Formation, QTm ............. 37

25. Perspective view showing result of kriged textural models for the younger 

alluvium, older alluvium, and Morales Formation units (Qya, Qoa, and QTm) 

along two vertical sections ..................................................................................................... 38

Tables

1. Correspondence between map units from source geologic maps to geologic units .......... 6

2. Geologic units affected by Cuyama Valley faults ..................................................................... 17

3. Summary of logs used for textural analysis by geologic unit . ............................................... 33

4. Kriging parameters used for textural analysis . ........................................................................ 34
v

Conversion Factors, Datums, and Abbreviated Water-Quality Units

Inch/Pound to SI

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Volume

barrel (bbl), (petroleum, 1 barrel=42 gal) 0.1590 cubic meter (m3

) 

Flow rate

gallon per minute (gal/min) 0.06309 liter per second (L/s)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Specific capacity

gallon per minute per foot [(gal/min)/ft)] 0.2070 liter per second per meter [(L/s)/m]

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1988 

(NGVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.
vi

Abbreviations

2-D two-dimensional 

3-D three-dimensional 

API American Petroleum Institute

BR1 bedrock unit 1

BR2 bedrock unit 2 

CA DOGGR California Department of Conservation, Division of Oil, Gas, and Geothermal 

Resources 

CA DWR California Division of Water Resources 

DEM Digital Evaluation Model 

ESRI Environmental Science Research Institute 

GIS geographic information system 

GPS Global Positioning System 

GT greater than

HUF Hydrogeologic-Unit Flow 

InSAR Interferometric Synthetic Aperture Radar 

LT less than

Ma mega-annum 

NAD 83 North American Datum of 1983

NGVD88 National Geodedic Vertical Datum of 1988

NWIS National Water Information System 

Qc Active stream deposits 

Qoa Older alluvium 

QTm Morales Formation 

Qya Younger alluvium 

SBCF Santa Barbara Canyon fault 

SP spontaneous potential

Tq Quatal Formation 

USGS U.S. Geological Survey 
vii

Acknowledgments

Emily Taylor, U.S. Geological Survey, Denver; Meghan Patterson, Metropolitan State College of Colorado; and Lauren Shumaker, University of California-Santa Cruz, transcribed paper 

drill-hole records into digital files, and Shumaker assigned textural parameters to down-hole 

lithologic intervals on the basis of analysis of geophysical electric logs. 

Staff at the U.S. Geological Survey California Water Science Center, San Diego District 

Office, digitized electric logs, georeferenced scanned large-format plates, and provided accurate 

locations for water wells in the valley. In addition to U.S. Geological Survey technical reviews, 

a draft of this report was improved by comments and insight and informal reviews from Victoria Langenhiem and Daniel Scheirer of the U.S. Geological Survey and from Dennis Gibbs of 

Santa Barbara County Department of Public Works, California. Funding for this study provided 

in part from the U.S. Geological Survey National Cooperative Geologic Mapping Program. 
viii
Construction of 3-D Geologic Framework and Textural 

Models for Cuyama Valley Groundwater Basin, California

By Donald S. Sweetkind, Claudia C. Faunt, and Randall T. Hanson 

Introduction 

Cuyama Valley is a rural agricultural area about 55 kilometers (km) north of Santa Barbara and approximately 65 km 

southwest of Bakersfield, California, in the southeasternmost 

part of the Coast Ranges of California (fig. 1). It lies west of 

the San Joaquin Valley and north of the west-trending Transverse Ranges (fig. 1). The valley is bounded on the north by 

the Caliente Range and on the southwest by the Sierra Madre 

Mountains, and it is drained by the Cuyama River (fig. 2). 

Cuyama Valley sits at the intersection of four counties: most 

of the valley is within Santa Barbara and San Luis Obispo 

Counties, regions near the headwaters of the Cuyama River lie 

in Ventura County, and a small eastern part of the Valley lies 

within Kern County (fig. 2). Although located within the Coast 

Ranges, Cuyama Valley has many of the climatic features of 

a desert basin because it is far from the coast and surrounded 

by relatively high mountains. The main economic activities 

in Cuyama Valley are ranching, agriculture, and oil and gas 

production.

Topographically, Cuyama Valley overlies and is part of a 

broader geologic domain, which was a depocenter for marine 

and nonmarine sediments during the Oligocene and Miocene 

epochs (Lagoe, 1984, 1987; Bazeley, 1988; Fritsche, 1988) 

and for continental deposits and alluvial sediments several 

hundred meters-thick during the Pliocene and Pleistocene 

epochs (Vedder and Repenning, 1975; Ellis and others, 

1993). These continental deposits and alluvial sediments 

constitute the principal groundwater aquifer of the Cuyama 

Valley groundwater basin (California Department of Water 

Resources, 2003; fig. 2). Groundwater is currently the sole 

source of water supply for Cuyama Valley. Groundwater 

withdrawal, mainly for the irrigation of crops, has resulted 

in water-level declines of as much as 100 meters (m) since 

the 1940s (Singer and Swarzenski, 1970; Pierotti and Lewy, 

1998). Groundwater is found in permeable Holocene alluvial 

fill and underlying less permeable Pliocene-Pleistocene continental deposits (Upson and Worts, 1951; California Department of Water Resources, 2003). In areas where drawdown 

is greatest, water-level declines have left the more productive 

shallow aquifers unsaturated and have dropped the water table 

into the less-productive, deeper aquifers. In response to these 

changes, the U.S. Geological Survey (USGS), in cooperation 

with the Water Agency Division of the Santa Barbara County 

Abstract

Groundwater is the sole source of water supply in Cuyama 

Valley, a rural agricultural area in Santa Barbara County, 

California, in the southeasternmost part of the Coast Ranges of 

California. Continued groundwater withdrawals and associated water-resource management concerns have prompted an 

evaluation of the hydrogeology and water availability for the 

Cuyama Valley groundwater basin by the U.S. Geological 

Survey, in cooperation with the Water Agency Division of the 

Santa Barbara County Department of Public Works. As a part 

of the overall groundwater evaluation, this report documents 

the construction of a digital three-dimensional geologic framework model of the groundwater basin suitable for use within a 

numerical hydrologic-flow model. The report also includes an 

analysis of the spatial variability of lithology and grain size, 

which forms the geologic basis for estimating aquifer hydraulic properties.

The geologic framework was constructed as a digital 

representation of the interpreted geometry and thickness of the 

principal stratigraphic units within the Cuyama Valley groundwater basin, which include younger alluvium, older alluvium, 

and the Morales Formation, and underlying consolidated 

bedrock. The framework model was constructed by creating 

gridded surfaces representing the altitude of the top of each 

stratigraphic unit from various input data, including lithologic 

and electric logs from oil and gas wells and water wells, cross 

sections, and geologic maps. 

Sediment grain-size data were analyzed in both two and 

three dimensions to help define textural variations in the 

Cuyama Valley groundwater basin and identify areas with 

similar geologic materials that potentially have fairly uniform 

hydraulic properties. Sediment grain size was used to construct three-dimensional textural models that employed simple 

interpolation between drill holes and two-dimensional textural 

models for each stratigraphic unit that incorporated spatial 

structure of the textural data.
2 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

Department of Public Works, is evaluating the hydrogeology 

and water availability of the groundwater basin. The intent of 

the overall study is to develop a greater understanding of the 

occurrence and availability of groundwater and to evaluate the 

potential effects of future groundwater withdrawals on different parts of the valley.

An evaluation and simulation of groundwater resources 

are most effectively achieved through an understanding of 

the subsurface geologic framework through which the water 

moves. As a part of the overall groundwater evaluation of 

Cuyama Valley, this report provides a conceptual understanding of the geologic setting of the Cuyama Valley groundwater 

basin and documents the construction of three-dimensional 

(3-D) digital models of the geologic framework and grainsize variations within the study area. These data provide the 

physical geologic framework that is used within a numerical 

hydrologic-flow model being developed concurrently (Randall 

Hanson, U.S. Geological Survey, written commun., 2013).

Purpose and Scope

This report describes the geology in the vicinity of Cuyama 

Valley, with an emphasis on the Pliocene through Holocene 

terrestrial sediments that have the greatest bearing on the 

Cuyama Valley groundwater basin. This report documents the 

use of surface and subsurface geologic data in the construction of a digital 3-D geologic framework model of the basin. 

The 3-D model is the digital representation of the interpreted 

geometry and thickness of subsurface geologic units and 

the geometry of folds and faults that bound the basin and lie 

within it. Previous work has outlined the overall shape of 

the basin and geometry of faulting along specific geologic 

profiles across the basin (Singer and Swarzenski, 1970; Vedder and Repenning, 1975; Davis and others, 1988), but the 

3-D geometry of the geologic units must be defined for the 

purposes of the numerical flow model. Most previous geologic 

Figure 1. Location of Cuyama Valley within the California Coast Ranges.

41

1

1

166

166

154

150

119

126

46

43

33

33

58

58

65

99

101

101

5

5

Limited access highway

Fault

Highway

Major road

City

EXPLANATION

Boundary of geologic-

 framework model

Study-area boundary

Boundary of groundwater-

 flow model

0 10 20 Miles

0 10 20 Kilometers

Pacific Ocean

Cuyama Valley

San

Joaquin

Valley Area shown

 on figure 2

Transverse Ranges

C o a s t R a n g e s

Santa Barbara

Bakersfield

Santa 

Maria

121° 120°30’ 120° 119°30’ 119°

35°

30’

35°

34°

30’

5

33

154

San Andreas fault

Shaded relief base from ESRI ArcGIS Online Map Service 

http://services.arcgisonline.com/arcgis/services: ESRI_ShadedRelief_World_2D

Roads from Cal-Atlas Geospatial Clearinghouse http://atlas.ca.gov/download.html

Place names sourced from USGS Geographic Names Information System, 1974–2009

San Andreas fault from Bryant (2005)

Albers Projection, NAD83

CALIFORNIA

Location of

map area

Bakersfield

Santa

 Barbara

San Francsico

Los Angeles

Pacific Ocean
Purpose and Scope 3

Figure 2. The Cuyama Valley study area. 

investigations in Cuyama Valley have focused on the deeper, 

oil-bearing rocks (Hill and others, 1958; Lagoe, 1987; Bartow, 

1990). Here, the geologic framework model uses information 

from a variety of datasets, including existing lithologic and 

electrical geophysical logs from oil and gas wells and water 

wells, cross sections, and geologic maps, to delineate the 

volumes of the aquifer system bounded by faults and relevant 

depositional or formational boundaries.

This report also documents the development of the 3-D 

spatial distribution of grain size of the basin-filling deposits. 

Textural characteristics such as grain size form the basis by 

which aquifer hydraulic properties are assigned within the 

numerical hydrologic-flow model (Hanson and others, 2003, 

2004; Faunt, 2009). Previous USGS studies of Cuyama Valley 

(Upson and Worts, 1951; Singer and Swarzenski, 1970) delineated aquifers in the saturated parts of the younger and older 

alluvium, which are the units that, historically, have yielded 

most of the water pumped in the study area. Since these studies were completed, water levels have declined in some areas 

into the deeper formations, such as the Morales Formation, 

that were not previously investigated in detail, requiring an 

investigation of the geometry and water-bearing properties of 

all of the basin-filling units, including the deeper stratigraphic 

sections of the groundwater basin. 

The focus of this investigation is the alluvial basin that 

underlies the valley and constitutes the principal groundwater reservoir beneath Cuyama Valley and adjacent areas at 

the basin margins, where Pliocene and younger continental 

sediments are exposed in outcrop and could serve as active 

recharge areas for the groundwater basin. The study area of 

interest thus includes the agricultural areas between the town 

of New Cuyama on the west and State Highway 33 on the east 

(fig. 2) and the part of the Cuyama River drainage extending 

southeastward along the Cuyama River to its headwaters south 

166

166

33

33

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

0 5 10 Miles

0 5 10 Kilometers

EXPLANATION Shaded relief base created from 30-m digital elevation model from USGS 

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

2009 Imagery from National Agriculture Imagery Program (NAIP) from Cal-Atlas

Spatial Data Clearinghouse, http://www.atlas.ca.gov/

Albers Projection, NAD83

Morales

Canyon

Quatal

Canyon Cottonwood

Canyon

166

New

Cuyama Cuyama

Ventucopa

Maricopa

Carrizo

Plain San Joaquin Valley

Cuyama

Badlands

Caliente Range

Cuyama Valley

Cuyama River

KERN COUNTY

SAN LUIS 

OBISPO COUNTY

SANTA BARBARACOUNTY

VENTURA COUNTY

Study-area boundary

Line of section from figure 3

Boundary of groundwater-flow model

Cuyama Valley groundwater basin

County boundary

Road

City or town

A A’

A

A’
4 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

of the Cuyama Badlands (fig. 2). The western boundary of the 

study area is located in the vicinity of the tributary washes of 

Morales Canyon on the north and Cottonwood Canyon on the 

south (fig. 2) to include all thick occurrences of young alluvium (Upson and Worts, 1951; Vedder and Repenning, 1975). 

Although the Cuyama Valley groundwater basin is the primary interest of this study, for computational reasons the geologic framework model covers a large rectangular area slightly 

larger than the boundaries of figure 2, and thus includes much 

bedrock of little hydrologic interest. The overall hydrogeologic evaluation of Cuyama Valley involves the use of a 

numerical hydrologic-flow model and a linked watershed 

model; the boundary of this numerical simulation forms an 

elongate, northwest-trending rectangular polygon aligned with 

the valley axis (fig. 2).

Geologic Setting

Aquifer units within the Cuyama Valley groundwater basin 

include unconsolidated Pleistocene and Holocene alluvial 

deposits and fluvial deposits of the Cuyama River drainage 

and the underlying partly consolidated nonmarine Morales 

Formation of Pliocene to Pleistocene age (Upson and Worts, 

1951; Singer and Swarzenski, 1970). These deposits unconformably overlie a late Cretaceous to middle Cenozoic succession of consolidated marine and nonmarine sedimentary rocks, 

which themselves overlie crystalline granitic and gneissic 

rocks (Hill and others, 1958; Dibblee, 1982; Lagoe, 1987; 

Bazeley, 1988; fig. 3).

Cuyama Valley has cumulative production plus reserves 

of about 290 million barrels of oil (Stanley, 1995; California 

Department of Conservation, 2009). Most of the production 

comes from the South Cuyama and Russell Ranch fields, 

located next to the Russell fault (fig. 4; Stanley, 1995). Abundant subsurface geologic data for this study have come from 

oil and gas wells from these fields and from exploration holes 

scattered across the valley (Nevins, 1982; Schwing, 1984; 

Calhoun, 1986; Spitz, 1986; Sweetkind and others, 2013).

Stratigraphic Units

The shallow alluvial section is subdivided into three units: 

Qc, fluvial channel deposits associated with the Cuyama 

River; Qya, younger alluvium; and Qoa, older alluvium 

(figs. 3 and 4; table 1). Previous studies did not separate the 

younger and older alluvium as separate units (Upson and 

Worts, 1951; Singer and Swarzenski, 1970), but the two are 

distinguishable as mappable units at the surface (fig. 4) and, 

in the subsurface, can often be identified by differences in 

electric log signature. 

Younger alluvium (Qya, figs. 3 and 4) consists of unconsolidated sand, gravel, and boulders, with some clay, deposited 

as alluvium in stream channels, floodplains, alluvial fans, 

and stream terraces. The unit is mainly Holocene in age, but 

locally can be late Pleistocene in part. Active stream deposits 

(Qc, figs. 3 and 4) consist of river-bed gravels of the Cuyama 

River and other active channels (Vedder and Repenning, 1975; 

DeLong and others, 2008, 2011). These deposits are incorporated into Qya within the geologic framework model.

DIAGRAMMATIC, NOT TO SCALE Adapted from Dibblee (1995)

Approximate line of section

 shown on figure 2

Caliente Formation

Morales Formation

Monterey Formation

Vaqueros Formation

Santa Margarita Formation

Crystalline

basement

rocks Oligocene and pre-Oligocene

siliciclastic rocks

Branch

Canyon

ss

Quatal Formation

Older alluvium Younger alluvium Alluvial channel

A A’

NW Cuyama Valley Cuyama Valley Cuyama Badlands Quatal Canyon

BR2

BR1

QTm

Northwest Qoa Qc Qya Southeast

Figure 3. Generalized stratigraphic diagram of the Cuyama Valley study area.
Geologic Setting 5

Older alluvium (Qoa, figs. 3 and 4) consists of unconsolidated to partly consolidated sand, gravel, and boulders, with 

some clay, and the percentage of clay increases in the western 

part of the valley (Singer and Swarzenski, 1970; Vedder and 

Repenning, 1975; DeLong and others, 2008). Interpretation of 

geophysical logs from oil-exploration wells indicates that this 

unit is typically 125 to 200 m thick, but as thick as 300 m near 

the axis of Cuyama Valley (Schwing, 1984; Spitz, 1986). In 

the study area, older alluvium includes dissected alluvial fans, 

colluvial deposits, and sediments on multiple terraces and 

alluvial surfaces (Hill and others, 1958; DeLong and others, 

2008). Older alluvium is exposed on uplifted alluvial surfaces 

along the south side of Cuyama Valley and in the center of 

the valley along the Turkey Trap and Graveyard Ridge faults 

(fig. 4; Vedder and Repenning, 1975; DeLong and others, 

2008). A greater degree of consolidation, dissection, and local 

deformation distinguishes the older alluvial deposits from 

young alluvium in outcrop.

The Pliocene-Pleistocene Morales Formation (QTm, figs. 3 

and 4) is an alluvial and fluvial deposit throughout most of the 

study area. The unit is as thick as 1,500 m and consists of massive- to thick-bedded, partly consolidated deposits of gravelly 

Figure 4. Generalized geology of the Cuyama Valley study area. 

A

A’

B’

B

M

M

M

M

166

166

33

33

Shaded relief base created from 30-m digital elevation model from USGS 

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

San Andreas fault from Bryant (2005). Albers Projection, NAD83

New

Cuyama Cuyama

Ventucopa

Maricopa

 Sierra Madre Mountains

Carrizo

Plain

San Joaquin Valley

Cuyama

Badlands

Caliente Range

Cuyama River

KERN COUNTY

SAN LUIS 

OBISPO COUNTY

SANTA BARBARACOUNTY

VENTURA COUNTY

M

EXPLANATION

Generalized stratigraphic units

Qc, active channel

Qya, young alluvium

Qoa, older alluvium

QTm, Morales Formation

BR1, Quatal Formation

BR1, Caliente Formation

BR2, bedrock unit 2

Normal fault

Thrust fault

Strike-slip fault

Thrust fault,

 concealed Syncline, concealed

Study-area boundary

GRF, Graveyard Ridge fault;

SBCF, Santa Barbara Canyon fault;

TTRF, Turkey Trap Ridge fault

Oil field

Line of section

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

0 5 10 Miles

0 5 10 Kilometers

South Cuyama fault

fault

Russell

Morales

fault

Cuyama

syncline

South

Cuyama

field

Russell

Ranch

field

Whiterock fault

GRF

TTRF

SBCF

Rehoboth

fault

San Andreas fault

Santa Barbara

Canyon

Ballinger

Canyon

Salisbury

Canyon

A A’

Syncline, showing 

plunge direction
6 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

arkosic sand with local gravel beds and siltstone (Hill and 

others, 1958; Ellis and others, 1993; DeLong and others, 2008, 

2011; Kellogg and others, 2008). In the western part of the 

study area, the unit is predominantly fine-grained and consists 

chiefly of lacustrine clay (Upson and Worts, 1951; Dibblee 

and Minch, 2005d; DeLong and others, 2008). The Morales 

Formation is widely exposed as badland topography east of 

the Cuyama River (fig. 4; Dibblee, 1982; Dibblee and Minch, 

2005a, 2006; Kellogg and others, 2008). 

For the purposes of this study, non-water-bearing consolidated rocks that lie beneath the Morales Formation are 

divided into two generalized geologic units: BR1 and BR2. 

Most of the middle Miocene and older consolidated rocks 

were included in the deeper unit, bedrock unit 2 (BR2; figs. 3 

and 4; table 1). This unit forms the bedrock highlands on the 

north, south, and east sides of the study area and includes 

consolidated marine and continental deposits of great thickness. Stratigraphic units that compose BR2 include the Santa 

Margarita Formation, the Branch Canyon Sandstone, the 

Monterey Formation, the Vaqueros Formation, and older rocks 

(fig. 3; table 1). 

Continental sedimentary rocks of the Caliente Formation 

and the Quatal Formation were retained as a separate bedrock 

unit (BR1; figs. 3 and 4; table 1) because they are significantly 

less consolidated than the underlying units, which can result in 

different water-transmitting properties. The Quatal Formation 

is a nonmarine claystone and sandstone sequence that conformably underlies the Morales Formation (Hill and others, 

1958). At its type locality in the Cuyama Badlands, it consists 

of about 250 m of gypsiferous claystone, although elsewhere 

in the study area, nonmarine sandstones are interbedded with 

the claystone (Vedder, 1968; Kellogg and others, 2008). The 

unit is readily identified in the subsurface throughout the eastern part of the study area as a distinctive interval on electric 

logs; it thins westward and pinches out beneath the central part 

of Cuyama Valley (fig. 3; Ellis and Spitz, 1987; Ellis, 1994). 

The Quatal Formation is not part of the active groundwater 

flow system. It is highlighted on the geologic map because, in 

the eastern and central parts of the study area, it is a distinctive stratigraphic marker that defines the base of the Morales 

Formation and the base of the groundwater system (figs. 3 and 

4; table 1).

Historically, most of the water pumped from the study area 

was obtained from the younger and older alluvium (Singer 

and Swarzenski, 1970). Large-capacity wells perforated in 

the alluvium yield 1,000–3,000 gallons per minute (gpm) and 

have specific capacities in the range from 100 to 200 gpm per 

foot (gpm/ft; Singer and Swarzenski, 1970). The water-bearing 

properties of the Morales Formation are not well defined, but 

available data indicate that hydraulic conductivity, the ease 

Table 1. Correspondence between map units from source geologic maps to geologic units.

Geologic unit 

(abbreviation) Unit description Corresponding geologic units

 (Kellogg and others, 2008)

Corresponding geologic units

(Graham and others, 1999)

Quaternary channel 

deposits (Qc)

Includes active channel of the Cuyama River and 

recent meander cutoffs.

Qa, active alluvium. Not shown

Younger alluvium 

(Qya)

Young unconsolidated alluvium on valley floor and in 

tributary washes.

Qya, younger (inactive) alluvium. Qa, alluvium

Older alluvium 

(Qoa)

Older alluvial deposits, partly consolidated. Dissected 

and deformed into gentle folds.

Qoa, older alluvium;

QTa, old alluvium, locally deformed.

Qoa, older alluvium

Morales Formation 

(QTm)

Weakly to moderately indurated arkosic, lithic sandstone and conglomerate. Fine-grained lacustrine 

facies in western part of study area.

QTm and subunits, Morales Formation;

QTt, Tulare Formation

Tmo, Morales Formation;

QTp, Paso Robles Formation

Quatal Formation 

(Tq)

Predominantly fine-grained fluvial to lacustrine 

siltstone and fine-grained sandstone. Underlies 

Morales Formation in eastern half of the study area, 

pinches to zero thickness in the vicinity of the town 

of Cuyama.

Tq and subunits, Quatal Formation;

Tlc, Lockwood Clay.

Tq, Quatal Formation.

Bedrock unit 1 

(BR1)

Continental sedimentary rocks of the Caliente Formation. In the subsurface the Caliente Formation interfingers westward with Middle Miocene consolidated 

marine rocks.

Tc and subunits, Caliente Formation. Tc, Caliente Formation.

Bedrock unit 2 

(BR2)

Includes all Miocene and older consolidated bedrock 

units (except for continental Caliente Formation). 

Tertiary basalts that are interbedded with Caliente 

Formation in the Caliente Range were included in 

this unit.

Tcb, Alkalic olivine basalt flow;

Ti, Intrusive olivine diabase;

Tsm and subunits, Santa Margarita 

Sandstone;

Tb and subunits, Branch Canyon 

Sandstone;

Tm and subunits, Monterey Formation;

Tv and subunits, Vaqueros Formation; 

all older units.

Tb, basalt; 

Tsm and subunits, Santa Margarita 

Formation;

Tbs, Branch Canyon Sandstone;

Tm and subunits, Monterey Formation;

Tv and subunits, Vaqueros Formation; 

all older units.
Geologic Setting 7

with which water passes through the formation, varies greatly 

both areally and with depth. Wells perforated in the Morales 

Formation along the northern margin of the central valley 

have specific capacities of 25–50 gpm/ft; wells perforated in 

the finer-grained facies in the western part of the valley have 

specific capacities of 5 to 25 gpm/ft (Singer and Swarzenski, 

1970). Inspection of available geologic and geophysical logs 

indicate that the hydraulic conductivity of the Morales Formation decreases with depth.

Structural Setting

In the Cuyama Valley region, Oligocene extension and 

Miocene strike-slip faulting are overprinted and obscured 

by Pliocene- to Pleistocene-aged thrust faults that bound the 

ranges surrounding the current topographic valley (Calhoun, 

1986; Davis and others, 1988). Rocks of Miocene age and 

older are known from deep oil and gas wells to be affected 

by older, now inactive faults largely buried by the Morales 

Formation and younger units (Yeats and others, 1989). The 

most significant of these older faults is the Russell fault at the 

west edge of the study area (fig. 4). This fault localizes the oilproducing fields in Cuyama Valley by trapping petroleum in 

faulted updip ends of sandstones within the Miocene Vaqueros 

Formation (Stanley, 1995). Up to 29 km of right-lateral offset 

has been documented on the northwest-striking Russell fault in 

the northwest part of Cuyama Valley to have occurred between 

23 and 4 mega-annum (Ma), but the fault has little to no offset 

in Morales Formation or younger units (Yeats and others, 

1989; Ellis and others, 1993). 

During Pliocene time, the deformational style in Cuyama 

Valley changed to a predominantly compressional mode during the deposition of the Morales Formation (Ellis and others, 

1993; Ellis, 1994). Resultant deformation has created the 

Cuyama structural basin and produced the converging thrust 

faults that bound Cuyama Valley: the south-directed Whiterock and Morales faults on the north and the north-directed 

South Cuyama fault on the south (fig. 4; Vedder and Repenning, 1975; Davis and others, 1988). Based on the magnetostratigraphy of the Morales Formation, uplift of the Caliente 

Range began between 3.0 and 2.6 Ma (Ellis and others, 1993; 

Ellis, 1994). Thrust motion continued into Quaternary time, 

with Miocene-aged rocks of the Caliente Range to the north 

of Cuyama Valley being thrust southward over Quaternary 

alluvium on the Morales fault (Vedder and Repenning, 1975). 

DeLong and others (2008) report thrust-fault interaction with 

Quaternary piedmont deposits in the western part of the study 

area indicateing ongoing contraction through 0.1 Ma.

Contraction of the Cuyama structural basin is driven by 

transpressional forces resulting from northwest-directed transport of the crustal block containing Cuyama Valley around the 

Big Bend of the San Andreas fault system to the east (Argus 

and Gordon, 2001; Hardebeck and Michael, 2004). Geodetic 

results from various models indicate that the San Andreas fault 

system and central California Coast Ranges accommodate 

northwest-directed motion relative to the North American 

plate of about 39 mm/yr, mainly by strike-slip faulting (Meade 

and Hager, 2005), with a small and variable amount of faultperpendicular convergence (Argus and Gordon, 2001). The 

greatest amount of convergence along the length of the San 

Andreas fault system is in the vicinity of the Big Bend of the 

San Andreas fault (Argus and Gordon, 2001), an area that 

includes Cuyama Valley. Inversion of focal mechanisms of 

small earthquakes near the San Andreas fault showed that the 

direction of maximum horizontal compressive stress in the 

vicinity of the Big Bend of the San Andreas fault is between 

40 and 60 degrees to the strike of the fault (Hardebeck and 

Michael, 2004). In the vicinity of Cuyama Valley, this direction is approximately perpendicular to the valley axis and 

tectonically consistent with the orientation of thrust faults that 

bound the north and south sides of the valley. 

The Morales Formation and older alluvium are folded into 

tight synclines along the north and south margins of the valley near the bounding thrust faults (Spitz, 1986; Kellogg and 

others, 2008). The Cuyama syncline plunges northwestward 

beneath the valley from the Cuyama Badlands to the southeast (fig. 4; Dibblee, 1982; Ellis and Spitz, 1987; Dibblee and 

Minch, 2005a; 2006; Kellogg and others, 2008). It is exposed 

in the Ventucopa area and the Cuyama Badlands (fig. 4; Dibblee and Minch, 2005a; 2006; Kellogg and others, 2008) and 

is known from subsurface data from oil exploration wells 

beneath the valley itself (Spitz, 1986; Ellis and Spitz, 1987; 

Ellis, 1994).

Faults and the Groundwater Flow System

Faults of hydrologic significance in Cuyama Valley area 

are those that involve the aquifers. Such faults occur at the 

basin margin, where fault offset juxtaposes basin-fill sediments against older consolidated rocks, and within the basin, 

where basin-fill units of differing water-transmitting ability are 

juxtaposed. Faults that offset the consolidated rocks are known 

principally from oil and gas exploration; faults within the 

basin fill have been recognized previously as being associated 

with historic surface springs or changes in groundwater elevations (Singer and Swarzenski, 1970). Three faults within the 

basin offset the basin-filling deposits and are associated with 

known water-level changes (Upson and Worts, 1951, Singer 

and Swarzenski, 1970): the thrust faults that bound Turkey 

Trap and Graveyard Ridges, the Santa Barbara Canyon fault, 

and the Rehoboth fault (fig. 4).

Graveyard and Turkey Trap Ridges in the center of Cuyama 

Valley, north of Highway 166, trend slightly north of west, 

are oriented in a left-stepping, en echelon pattern and contain 

exposures of older alluvium (Qoa; fig. 4). Geologic mapping 

and north-south seismic reflection profiles collected across 

these ridges showed that these ridges are bounded by northdipping, south-directed, reverse faults along their south sides 

(Upson and Worts, 1951; Vedder and Repenning, 1975; Ellis, 

1994). Upson and Worts (1951) reported the presence of 
8 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

springs and seeps along the base of Turkey Trap and Graveyard Ridges in 1946. Singer and Swarenski (1970) reported 

water-level drawdowns of 80 to 100 feet (ft) in the area near 

these ridges and indicated that water removed by pumping 

from this region was slow to replenish because faults restrict 

movement of water from neighboring areas. The impediment 

to flow could be related to the hydraulic properties of the fault 

itself or fault juxtaposition of older, slightly less permeable 

Qoa, to the north, against Qya to the south of the faults.

A fault, here called the Santa Barbara Canyon fault (SBCF, 

fig. 4), was suggested by Singer and Swarzenski (1970) to 

be the cause of a steep hydraulic gradient in the southeastern 

part of Cuyama Valley, where water levels in the vicinity of 

Ventucopa are at least 30 m higher than water levels 3 km to 

the north. Singer and Swarzenski (1970) suggest that this fault 

could be a projection of east-northeast-striking faults mapped 

west of Santa Barbara Canyon by Dibblee and Minch (2007) 

on the basis of anomalous topographic lineaments in older 

alluvium. No geologic evidence bearing on sense or amount of 

offset has been found in the field, although some confirmation 

of faulting is provided by truncation of distinctive gravel beds 

in the older alluvium along the west wall of Santa Barbara 

Canyon, near its mouth, on trend with the lineaments. Very 

minor throw, southeast-side down, is indicated by distinctive 

markers in the Morales Formation on geophysical logs from 

wells on either side of the lineaments, and Dibblee and Minch 

(2007) showed about 1,500 m of left-lateral offset on fold axes 

across the lineaments. Such lateral slip on east-northeast-striking faults is consistent with the present northward-directed 

compressive tectonic regime of Cuyama Valley. Although a 

single fault is shown on figure 4, the topographic lineaments 

mapped in the piedmont upland and the width of the zone 

where there are water-level changes indicate that there could 

be a zone of subparallel faults. No deep-well data constrain 

how these faults project northeastward across the Cuyama 

River; analysis of formation contacts, dip amounts, and dip 

directions in Ballinger Canyon on the east side of the Cuyama 

River reveals no obvious continuation of this fault trend. The 

relatively small amount of vertical offset on the Santa Barbara 

Canyon fault indicate that changes in water levels across this 

fault documented in previous studies are perhaps the result of 

distinct fault-zone properties, rather than juxtaposition of units 

of differing water-transmitting ability.

Another fault, here called the Rehoboth fault (fig. 4), is 

inferred from water-level changes in the west-central part of 

the valley. The fault is interpreted to trend southeastward near 

the town of Cuyama and to project beneath the Salisbury Canyon drainage (Lane-Western Company, written commun. to 

developers of Rehoboth Farms property, 1982). Comparison of 

the elevation of distinctive marker horizons within the Morales 

Formation on geophysical logs of exploration wells drilled 

on either side of the fault indicates that the top of the Morales 

Formation is offset about 50 m down on the northeast side of 

the fault; offset at the base of the Morales Formation is greater. 

Surface exposures of Qoa do not appear to be offset along the 

trace of the fault, indicating that motion on this fault may have 

ceased prior to deposition of the youngest part of Qoa.

Regional Tectonics and Uplift Rates

Geologic evidence indicates that Cuyama Valley has been 

the site of contractile deformation for the past 4 Ma (Ellis 

and others, 1993). Geologic relations along the southern 

flank of the Caliente Range, which forms the northern margin 

of Cuyama Valley, indicate contraction until as recently as 

100,000 yr (Ellis and others, 1993; DeLong and others, 2008). 

In addition to this shortening, ongoing compression manifests 

itself by broad regional tectonic uplift. Although the valley 

is low relative to the surrounding thrust-bounded ranges, it 

is elevated by 500–700 m relative to the San Joaquin Valley 

to the northeast of the San Andreas fault (Argus and Gordon, 

2001). The Pliocene and Pleistocene Morales Formation was 

deposited within Cuyama Valley structural basin as a result of 

uplift along valley-margin structures, erosion of those marginal rocks, and sedimentation in the basin (Spitz, 1986; Ellis, 

1994). As regional uplift continued, and the axial part of the 

valley narrowed, the Morales Formation and older Quaternary 

alluvium were themselves uplifted, exposed to fluvial erosion, 

and moderately deformed (Spitz, 1986; DeLong and others, 

2008). On the south side of Cuyama Valley, young Quaternary 

deposits unconformably overlie deformed older Quaternary 

deposits and the Morales Formation as a result of ongoing 

tectonic uplift and erosion (DeLong and others, 2008; Kellogg 

and others, 2008). The Cuyama River and its major tributaries 

are currently incised into Holocene alluvium in the axial part 

of the valley as a result of progressive regional tectonic uplift 

(DeLong and others, 2008, 2011).

Continuously monitored global positioning system (GPS) 

stations are located in Cuyama Valley and surrounding uplands 

as part of an integrated GPS Network designed to monitor 

deformation throughout southern California (Hudnut and others, 2002; Meade and Hager, 2005). The GPS stations record 

variations in position and elevation that can result from either 

tectonic motions or from deformation associated with anthropogenic activities such as groundwater withdrawal. Landsurface position was recorded at two GPS monitoring stations 

within the valley—at Cuyama High School near the center of 

the valley and near Ventucopa in the southeastern part of the 

valley—and three stations in the uplands to the east, south, 

and southwest of the valley (Everett and others, 2013). Running 31-day averages of GPS observations acquired between 

2000 and 2012 (2008–2012 for one of the upland stations) 

indicated a slight net upward motion at Ventucopa and the 

three upland stations outside the valley (Everett and others, 

2013). In contrast, land surface position for the GPS station 

at Cuyama High School records a long-term downward trend 

between 2000 and 2012 with cyclic, annual seasonal variations 

in elevation. This cyclic variation correlates with pumping 

records and variations in water levels measured in nearby 

wells (Everett and others, 2013). It is likely that the long-term 
Compilation of Surface and Subsurface Data 9

trend in subsidence at Cuyama High School represents inelastic, irreversible deformation of the underlying aquifer as a 

result of permanent changes in the pore volume and resulting 

loss of storage capacity within the aquifer, whereas shortterm seasonal trends represent elastic deformation associated 

with seasonal groundwater withdrawals (Everett and others, 

2013). The magnitude of subsidence between 2002 to 2008 

was estimated at five points in the central part of the valley 

from analysis of satellite interferometric synthetic aperture 

radar (InSAR) images, a remote sensing technique that can 

detect centimeter-level elevation changes (Everett and others, 

2013). Point analysis of the InSAR images confirmed downward movement throughout the central subregions of the basin 

where groundwater pumpage and related water-level declines 

are largest (Everett and others, 2013).

Compilation of Surface and 

Subsurface Data

Construction of the geologic framework model utilized 

data from multiple sources to define the top surface and extent 

of each geologic unit. Input data sources include topographic 

data, geologic maps, stratigraphic tops interpreted from 

borehole data, and structure contour maps. Textural properties 

of the basin-filling deposits were interpreted from borehole 

lithologic and electric logs.

Surface Geologic Map Data

A generalized geologic map of the study area (fig. 4) was 

compiled through the merging of two main digital data sets: 

(1) a 1:100,000-scale geologic map of the eastern threequarters of the Cuyama 30′ x 60′ quadrangle (Kellogg and 

others, 2008) that covers the main part of Cuyama Valley, the 

Cuyama Badlands, and the bedrock geology in a wide area to 

the south and east of Cuyama Valley, and (2) a 1:125,000-scale 

geologic compilation of geology along the San Andreas faults 

(Dibblee, 1973), as rendered digitally by Graham and others 

(1999), that was used to compile the geology at the northwest 

end of Cuyama Valley and in the Caliente Range. Larger-scale, 

non-digital geologic maps of parts of the basin were consulted 

for local geologic relations (Vedder, 1968; Vedder and Repenning, 1975; Calhoun, 1986; Dibblee and Minch, 2005a, 2005b, 

2005c, 2005d, 2006, 2007). 

Source geologic data were given a common map projection, 

and correlative geologic units from each of the source maps 

were merged in a geographic information system. Mapped 

geologic units were then combined into the limited number of 

geologic units of table 1. 

Stream-channel deposits in the northwestern part of the 

area were digitized from Vedder and Repenning (1975) and 

from satellite imagery. Numerous landslide deposits on 

bedrock units were merged with the underlying bedrock unit. 

Landslide deposits are generally thin (10–20 m thick) and are 

composed primarily of rubble from of the underlying bedrock.

Data points representing the location and elevation of 

stratigraphic contacts exposed in outcrop were generated 

from the geologic map in combination with a 1 arc-second 

(approximately 30-m resolution) National Elevation Dataset 

digital elevation model (Cal-Atlas Geospatial Clearinghouse; 

http://atlas.ca.gov/download.html). Regularly spaced points 

were digitized along a stratigraphic contact within a geographic information system (GIS). These points were assigned 

coordinate locations from the map base and elevations from 

the digital evaluation model (DEM) and exported as a series of 

files, one for each stratigraphic unit, containing x,y, and z data 

that were subsequently used in gridding the stratigraphic unit 

tops.

Subsurface Data

Oil and Gas Wells

Stratigraphic information from oil and gas exploration and 

development wells from Cuyama Valley, Calif., and surrounding areas have recently been compiled by Sweetkind 

and others (2013). Most of the oil wells in Cuyama Valley 

are clustered within two fields with historic and continuing production: the Russell Ranch field (Barger and Zulberti, 1952) at the west edge of the study area and the South 

Cuyama oil field (Zulberti, 1954) at the southwest edge of the 

study area (fig. 4). Production wells in those fields are very 

closely spaced; selected wells were used to represent geologic 

conditions in the vicinity of the producing fields. Exploratory 

wells were drilled away from the fields at widely scattered 

locations across Cuyama Valley. Data from every one of these 

exploratory wells were compiled for this study. Information 

on subsurface stratigraphy and lithology from over 200 oil and 

gas exploration wells was selected for use in the current study.

The California Department of Conservation, Division of 

Oil, Gas, and Geothermal Resources (CA DOGGR) maintains 

paper copies of electric logs on file for most of the oil and 

gas exploration holes in Cuyama Valley. Initially, logs were 

obtained directly from the CA DOGGR district office in Santa 

Maria, Calif., by physically scanning paper copies of the electric logs. The CA DOGGR has subsequently made some of the 

electric logs available on-line (http://owr.conservation.ca.gov/

WellSearch/WellSearch.aspx). 

In the 1980s four masters theses (Nevins, 1982; Schwing, 

1984; Calhoun, 1986; Spitz, 1986) and one Ph.D. dissertation 

(Ellis, 1994) were produced at Oregon State University under 

the guidance of Professor Robert Yeats. These works, and 

related publications (Schwing, 1982; Ellis and Spitz, 1987; 

Yeats and others, 1989), discussed the subsurface geology of 

Cuyama Valley and focused on the mapping of subsurface 

formations by using data from oil exploration holes, in particular electric logs. Each thesis contained several stratigraphic 

cross sections that correlated subsurface formations across the 
10 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

valley (Sweetkind and others, 2013). Although the focus was 

primarily on the Miocene section, the cross sections showed 

the interpreted base of the Morales Formation and, occasionally, showed correlation of distinctive marker units within 

the Morales. These sections served as a starting point for the 

electric log interpretations of formation tops in this study.

Water Wells

Downhole lithologic data from water-well drillers’ logs, 

used here to interpret formation tops and sediment grain size 

and sorting parameters, were derived from three sources: 

a U.S. Geological Survey Water-Supply paper on Cuyama 

Valley (Upson and Worts, 1951), lithologic data associated 

with well records obtained from the USGS National Water 

Information System (NWIS), and well data obtained from 

the State of California Department of Water Resources (CA 

DWR). Lithologic data from all wells reported by Upson and 

Worts (1951) were transcribed from the paper report. The 

location map that accompanied that report was georeferenced 

in a GIS, and well locations were digitized. Lithologic data 

associated with NWIS records and from CA DWR were also 

transcribed and tied to reported site locations. CA DWR wells 

were located according to descriptive information included on 

the well completion reports submitted to the State of California. The specific location of each well differed from GPS 

locations recently confirmed in the field with differential GPS 

systems to sketched maps or township, range, section, and 

quarter-quarter-section information on the well completion 

reports. Wells that had sufficiently detailed sketch maps were 

assigned a latitude-longitude by comparing the sketch maps 

with georeferenced aerial photos in a GIS. Latitude-longitude 

locations were established for wells listing only the township, range, section and quarter-quarter section locations on 

the drillers’ logs by calculating the center position of the most 

detailed part of the township and range location. Ultimately, 

all well locations were cross-checked against locations in the 

NWIS database, with well compilations for hydrologic data 

compiled for Cuyama Valley (Everett and others, 2013) and 

with field-checked locations. 

Of the water wells compiled for stratigraphic information, 

21 were from Upson and Worts (1951), and 56 wells came 

from the State of California and other sources. Of the water 

wells compiled for lithologic information and subsequent textural analysis, 41 were from Upson and Worts (1951), and 110 

wells were from the State of California and other sources.

Interpretation of Subsurface Data

Stratigraphic contacts, including the top of Qoa and the top 

and base of the QTm were interpreted from electric logs and 

drillers’ lithologic logs. For the oil and gas wells, formation 

tops were almost invariably interpreted from electric logs. 

Lithologic logs from the oil and gas exploration holes were 

not helpful in the shallow alluvial section, which was not of 

interest to the well-site geologists. Lithology in the shallow 

parts of these holes was typically logged with a single descriptor, such as “sand and gravel,” that might apply to hundreds 

of meters of section. Similarly, the tops of Qoa and the QTm 

were typically not recorded by these geologists; formation tops 

were reported only for consolidated rocks below the Morales 

Formation. In contrast to the oil and gas exploration wells, 

very few water wells had electric logs. Stratigraphic tops 

generally were interpreted in the water wells from drillers’ 

lithologic descriptions.

Oil and Gas Wells

An electric log typically consists of a spontaneous potential, or SP, curve placed alongside one or more resistivity 

curves (fig. 5). Many of the oil and gas exploration wells in 

Cuyama Valley were drilled in the 1940s and 1950s (Stanley, 

1995), when these particular logs were commonly the only 

geophysical logs run. They are valuable for correlating geologic units between wells, determining unit or bed thickness, 

distinguishing porous and non-porous rocks in shale-sandstone 

sequences, and identifying beds containing fresh water (Keys 

and MacCary, 1971).

Stratigraphic units, and lithologic variations within stratigraphic units, are interpreted on the basis of their characteristic electric log response (Keys and MacCary, 1971; Johnson 

and Pile, 2002); interpretations are tied, where possible, to 

lithologic descriptions of cuttings and core and to nearby outcrops. High-porosity quartz-bearing units, such as sandstone 

and sand and gravel, typically show leftward deflections of the 

SP-curve (toward more negative values) and rightward deflections of the resistivity curves (toward larger resistivity values). 

Low-porosity, shaly units tend to have the opposite electric 

log response, with rightward deflections of the SP-curve 

(toward more positive values) and leftward deflections of the 

resistivity curves (toward smaller resistivity values; Keys and 

MacCary, 1971; Johnson and Pile, 2002). In thin-bedded units, 

the poor vertical resolution of the SP-logging tool produces an 

average log response from multiple lithologic units rather than 

separating the units. Because SP- and resistivity logs measure 

a response only where the borehole contains fluids—either 

drilling mud or formation waters—the upper few hundred feet 

of section potentially would not be captured by these methods 

(fig. 5), and, in certain wells, the shallowest stratigraphic units 

were not recorded by the electric logs.

Qya has generally high, but irregular, resistivity values 

characterized by high amplitude, short wavelength, resistivity 

peaks (fig. 5). This response is a result of large clast size, poor 

sorting, and abundant channel deposits of gravelly material 

inset into finer-grained overbank deposits that create abrupt 

lithologic contrasts and generate a strong resistivity-log 

response. The subdued nature of the SP-log response could be 

the result of thin bedding.

Qoa tends to have a more subdued resistivity-log response 

when compared to Qya (fig. 5), although some wells have 

resistivity peaks of moderately-high amplitude and short 

wavelength when compared to the underlying section. The 

contact with the underlying Morales Formation is typically 
Compilation of Surface and Subsurface Data 11

Figure 5. Composite electric log from the Cuyama Valley study area.

08303364

Spontaneous

potential,

in millivolts25

50

0

−50−25

Lateral

resistivity,

in ohm-m 102030

40

0

Spontaneous

potential,

in millivolts25

50

0

−50−25

Lateral

resistivity,

in ohm-m 102030

40

0

2,400

2,200

2,000

1,800

1,600

1,400

1,200

1,000

800

600

400

200

0

DEPTH, IN FEET

2,400

2,200

2,000

1,800

1,600

1,400

1,200

1,000

800

600

400

200

0

DEPTH, IN FEET

07900187

Qoa

Qya

BR1 (Tq)

QTm

QTm

BR2

Two electric logs from oil and gas exploration 

drill holes in Cuyama Valley penetrate the 

upper and lower parts of the valley fill, 

forming a composite log for the basin. Log 

traces digitized from electric logs obtained 

from California Department of Conservation, 

Division of Oil, Gas, and Geothermal 

Resources. Left track of each log represents 

spontaneous potential (SP), the two tracks on 

the right side of each log are resistivity logs. 

Depth scales are for the individual wells, in 

feet below land surface. 

Subsurface

formation

Correlation of

marker bed

within QTm

OA19

OA19—Lateral resistivity log;

 19-foot electrode spacing.

OA10—Lateral resistivity log;

 10-foot electrode spacing.

OA10

Qya, young alluvium

Qoa, older alluvium

QTm, Morales Formation

BR1 (Tq), Quatal Formation

BR2, bedrock unit 2

Geologic unit
12 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

marked by a thin zone with inward deflections of the SP-curve 

(rightward, toward more positive values) and the resistivity 

curves (leftward, toward smaller resistivity values) (fig. 5; 

1,100-ft depth, log 07900187).

 The QTm can be broadly subdivided into an upper part 

that has a generally subdued electric log response in both the 

SP- and resistivity curves (fig. 5; between 1,100 and 2,350-ft 

depth, log 07900187) and a lower part that has several distinct 

coarse-grained intervals (fig. 5, log 08303364). In outcrop, 

this upper unit is poorly-sorted, consisting of pebbles and 

cobbles in a fine sand matrix (Dibblee and Minch, 2005a, 

2006; Kellogg and others, 2008). The subdued log response 

in the upper part of the QTm could be the result of the lack of 

distinct bedding and lithologic contrast between beds of differing grain size. In this interval, the Morales Formation tends to 

be a massively-bedded arkosic clayey sandstone derived from 

granitic and metamorphic rocks (Hill and others, 1958). In the 

lower part of the QTm, boulder trains and gravelly channel 

deposits create deflections to lower values on both SP- and 

resistivity logs (fig. 5, log 08303364). The Quatal Formation 

(Tq, fig. 5, log 08303364) below the QTm is picked as a distinctive interval characterized by inward deflection of both the 

SP- and resistivity curves. 

Ideally, an oil and gas exploration well would intersect 

a partial thickness of Qya and the full thickness of Qoa and 

the QTm (fig. 5). As a result of the variable stratigraphic 

and structural setting across the basin, few individual wells 

encounter all of these stratigraphic units (fig. 6). Exploration wells drilled in upland areas to the south of the valley 

are spudded in Qoa, such that only the top and base of the 

QTm are intersected. In some cases, the electric logging 

begins below the top of the QTm, such that only the base of 

the unit is recorded (fig. 6). Previous workers (Nevins, 1982; 

Schwing, 1984; Calhoun, 1986; Spitz, 1986), who interpreted 

electric-log data in Cuyama Valley, tended not to pick the 

top of the Morales Formation but, instead, identified distinctive marker beds within the Morales Formation that allowed 

correlation between wells in the upper part of the sedimentary 

section (fig. 6). The most readily identifiable horizons within 

the Morales Formation are distinctive fine-grained units that 

represent periods of depositional quiescence across parts of 

the basin. Similarly, coarse sand bodies can be correlated over 

more limited areas, but the fine-grained units tend to be more 

widely distributed and can be correlated over broad areas 

(fig. 6). These fine-grained units serve as stratigraphic marker 

horizons within the Morales Formation and serve as guides to 

the relative elevations of the top and base of the formation in 

any borehole.

Water Wells

Water well drillers’ lithologic descriptions were highly 

variable in terms of the number and thickness of subsurface 

intervals described, the detail of the descriptions, and the 

words used to describe specific sediment types and textures. 

The descriptions required geologic interpretation to obtain 

consistency between wells and to identify the unit penetrated. 

Key descriptive elements used to identify stratigraphic units 

included the degree of cementation and relative amount of 

clay; color was considered a secondary element, but was 

not used as a primary discriminator. Degree of cementation was used to distinguish Qoa from Qya where, in many 

cases, deeper intervals encountered during drilling would be 

described as “hard” or “slow drilling,” or the intervals would 

be described as sandstone and conglomerate, instead of sand 

and gravel, respectively. The Morales Formation was often 

distinguished from the overlying older alluvium by an abrupt 

increase in the number of clayey intervals. The clayey, arkosic 

sands of the Morale Formation were often described by drillers as “decomposed granite,” in contrast to overlying intervals 

described as sand and gravel. Thin intervals described as being 

yellow, orange, or red in color, where present within a thick 

interval described by another color, were interpreted as possible paleosols that record an episode of exposure and surficial 

weathering. These intervals were interpreted as boundaries between units where supported by other factors, such as 

degree of cementation.

Compilation of Stratigraphic Tops from 

Well Data

Stratigraphic tops from the oil and gas and water wells 

were assembled in a single database and checked for internal 

consistency. The spatial distribution of these tops is shown in 

a perspective view looking from above and north to the south 

in figure 7. In this view, water wells appear as a cluster of relatively shallow wells along the center of the basin that mostly 

intercept the Qya. Oil and gas exploration wells predominantly 

intercept the Qoa and QTm units. Wells in the far southeast 

part of the study area (upper left part of figure 7) penetrate 

thin sections of younger alluvium overlying bedrock units. 

Stratigraphy was not interpreted for every downhole interval 

in every well. Where stratigraphic units were not interpreted 

for specific downhole intervals, they are shown as a thin vertical line (fig. 7).

Contacts interpreted from borehole lithologic and electric 

logs were assigned x,y, and z coordinate locations for use in 

the geologic framework model. All boreholes were assumed 

to be vertical, so that all contacts from a well were assigned 

the x,y coordinates of the well’s surface location. Stratigraphic 

unit contacts, originally compiled as depth below land surface 

from the source data, were converted to elevation values by 

subtracting measured depth from the land-surface altitude at 

the well. Two types of data were generated from the borehole 

records: points where the stratigraphic top was explicitly 

picked from the data and points that only define limiting 

values for the elevation of the top. Limiting values are defined 

for cases where the top of the formation is above the start of 

the electrical geophysical log, such that the top of the log only 

provides a maximum value for the drilled depth to the top of 

the stratigraphic unit.
Compilation of Surface and Subsurface Data 13

Figure 6. Correlation of electric logs from the central part of the Cuyama Valley study area.

0

100

200

300

400

500

600

700

800

900

1,000

100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

0 100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

1,400

0

100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

1,400

1,500

0

08304143

08304149

08304266

08304552

top

Morales Fm

Depth, in meters

base

Morales Fm

Marker G1

Marker G2

Marker G3

top Morales Fm

above top of

electric log

Qoa

Qya

BR1 (Tq)

QTm

BR2

Representative electric logs from Cuyama Valley, obtained 

from California Department of Conservation, Division of Oil, 

Gas, and Geothermal Resources. Left track of each log 

represents spontaneous potential (SP), the two tracks on 

the right side of each log are resistivity logs.

Fm is Formation

0

0 1 2

1 2 Miles

Kilometers

Cuyama

River

New

Cuyama

Cuyama

08304143

08304149

08304266 08304552

Qoa

Qoa Qya

Qya

BR2

BR2

119°45’ 119°40’ 119°35’

35°

34°

55’

166

Qya, young alluvium

Qoa, older alluvium

QTm, Morales Formation

Geologic unit

BR1 (Tq), Quatal Formation

BR2, bedrock unit 2
14 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

Figure 7. Three-dimensional (3-D) perspective view of geologic units in water wells and oil and gas wells in Cuyama Valley.

EASTING, IN METERS

NORTHING, IN METERS

860,000

840,000

820,000

800,000

780,000

3,850,000

3,870,000

3,890,000

ELEVATION, IN METERS 3,830,000

2,000

1,000

-2,000

-1,000

0

EXPLANATION

Young alluvium (Qya)Young alluvium (Qya)Quatal Formation BR1 (Tq) ( )

Bedrock, undivided (BR)

Morales Formation (QTm)Old alluvium (Qoa)Active channel (Qc)Quatal Formation (BR1 (Tq))

Caliente Formation (BR1)Morales Formation (QTm)

Bedrock unit 2 (BR2)Old alluvium (Qoa)

Geologic units shown on map viewGeologic units shown on drill holes

Map base is a digital elevation model from U.S. Geological 

Survey, 1981. Universal Transverse Mercator Projection, 

Zone 10 North American Datum 1983.

View is from the northeast (020 degrees) looking to the southwest from an elevation of 30 degrees above the horizon. Map vertical exaggeration is 2X; wells have a vertical exaggeration of 8X. Horizonal and vertical scale is variable due to the effects of perspective view.

Colored cylinders represent stratigraphic units intercepted downhole

in oil and gas exploration holes and water wells. Thin vertical

lines represent parts of the borehole where stratigraphy

was not interpreted. Colors appear variable due to the

effects of illumination from below andsoutheast. South Cuyama

field Russell Ranch

field

South Cuyama

field

Russell Ranch

field

Water well

Oil and gas

exploration

well

Water well

Oil and gas

exploration

well

N
3-D Geologic Framework Model 15

3-D Geologic Framework Model

A 3-D geologic framework model was constructed to 

represent the subsurface geometry of the stratigraphic units, 

Qya, Qoa, QTm, and a composite pre-QTm bedrock unit. 

This digital model provides the fundamental geologic framework for the subsequent development of a transient numerical 

hydrologic-flow model of the study area (Randall Hanson, 

U.S. Geological Survey, written commun., 2013).

The geologic framework model was constructed by 

creating surfaces representing the altitude of the top of each 

stratigraphic unit from the input data and then combining these 

surfaces within a 3-D geologic modeling software package. 

Each surface is represented by a grid covering a rectangular 

area slightly larger than that shown in figure 2, with dimensions of 85,000 m in the east-west direction and 65,000 m in 

the north-south direction. Square grid cells are 200 m in size, 

resulting in 426 grid cells in the east-west direction and 326 

cells in the north-south direction. Software-based requirements 

for the grids and 3-D model to be aligned with the cardinal 

directions resulted in the inclusion of areas to the northeast 

and southwest of Cuyama Valley far outside the area of interest to this study. 

To construct the geologic framework model, spatial data, 

such as digital elevation, outcrop, and borehole information, were compiled using Environmental Science Research 

Institute (ESRI) ArcGIS® software. Interpolation of spatial 

data points into grids representing the stratigraphic unit tops 

was processed using Rockware Rockworks14® 3-D-modeling 

software. This software was designed to represent stratigraphic 

relations within sedimentary basins, including representation 

of depositional contacts and stratigraphic onlap, erosion, and 

unconformities. The 3-D-modeling software does not allow 

explicit entry of fault surfaces into the 3-D framework, so 

the effect of faulting was accomplished by inserting numerical discontinuities during the gridding of individual horizons. 

The resultant grids have steep inflections at the fault trace but 

remain as continuous surfaces within the geologic framework 

model.

Modeling Approach

The geologic framework model represents the altitude 

of the top of stratigraphic unit as a grid that spans the entire 

rectangular framework model domain. Because of the requirement for grids to be continuous, where stratigraphically lower 

units are exposed at land surface, one or more shallower units 

are required to have the same land-surface elevation but to 

have zero thickness (fig. 8). Four general cases describe the 

elevation and thickness of a particular stratigraphic horizon 

with respect to the elevations of other horizons in the geologic 

framework model (fig. 8):

(1) The top of the unit is present in the subsurface beneath 

other units, where the elevation of the unit top is defined by 

well data or by the thickness of the overlying unit and the 

thickness of the unit is defined by well data.

(2) The unit crops out at land surface, such that the eroded 

top of the unit is defined by the DEM, and the thickness of the 

unit is defined by well data.

(3) The unit of interest has an elevation defined by the 

DEM and zero thickness where an underlying unit crops out at 

the surface.

(4) The unit of interest can crop out at land surface, where 

the elevation of the top is defined by the DEM, or exist in the 

subsurface, where the elevation of the top is defined by well 

data, but thickness of the unit is an arbitrary or assigned value.

As an example, figure 9 depicts these general cases as they 

were applied to Qoa over the western half of the study area. 

In the center of the basin (region 1, fig. 9), Qoa is overlain by 

Qya, and the elevation of the top of Qoa is defined by well 

data. Where Qoa crops out at land surface (region 2, fig. 9), 

the top of the unit is defined by the DEM, and the thickness 

of the unit is defined by well data. The top of the unit in this 

case is a modeled top based on erosion at land surface, not the 

true stratigraphic top. In a relatively small area on the extreme 

eastern edge of the study area (region 3, fig. 9), map data and 

limited well data indicated the presence of Qoa, but the well 

data were too limited to create a satisfactory thickness grid, 

and the unit was assigned an arbitrary thickness (region 3, 

fig. 9). Finally, in areas of bedrock outcrop (region 4, fig. 9), 

the top of Qoa is assigned the elevation of land surface and a 

thickness of zero. Using the cases described above, the elevation grids for each stratigraphic unit were built in an iterative 

fashion. First, the parts of the unit present in the subsurface 

were gridded using the well data. These grids were then modified in areas where the unit cropped out or where underlying 

units were exposed at land surface.

Input data points were pre-processed with a declustering 

routine prior to surface gridding, such that multiple closelyspaced data points were assigned an averaged location and 

altitude value that was used as input to the surface-modeling 

routine. The optimal degree of pre-processing was one that 

eliminated extreme clusters of data (for example data from 

closely-spaced production wells in oil fields), but did not result 

in an overly smoothed trend where all local variation was 

eliminated. Data representing the altitude of a stratigraphic 

top were gridded using an inverse distance algorithm, where 
16 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

the value assigned to a grid node was computed as a distanceweighted average of the nearest 12 directionally-distributed 

neighbors. The value of each of the data points was exponentially weighted according to the inverse of its distance from 

the grid node; weighting was adjusted to balance the effects of 

strong, local control with a broader regional average. 

For computational convenience, all faults in the study 

area were generalized as vertical boundaries and dropped 

from their surface locations. Faults were inserted within the 

gridding algorithm as two-dimensional (2-D) boundaries that 

acted as a barrier to information flow during horizon gridding. 

When point data were gridded, elevation data on one side of a 

fault were not directly used when calculating grid node values 

on the other side of the fault. The resultant grids have sharp 

inflections where the altitude of the surface changes rapidly, 

but the gridded surface remains continuous and is not split into 

two segments by the fault. 

For the purposes of use within a numerical hydrologic-flow 

model, the faults were classified according to their recency and 

the stratigraphic units that each fault offsets (table 2). Motion 

on the Russell fault is documented to have ended during 

Morales Formation time, and the fault does not affect younger 

units (Yeats and others, 1989; Ellis and others, 1993). Well 

data indicated that the Morales and Santa Barbara Canyon 

faults create offset in the Morales Formation and the older 

alluvium (table 4). The thrust faults that bound the Turkey 

Trap Ridge and Graveyard Ridges (fig. 4) affect all stratigraphic units within the basin, as does the Rehoboth fault (fig. 

4, table 2).

Figure 8. Diagrammatic cross section showing relative elevation of stratigraphic unit tops and resultant thickness within the 

framework model.

Qoa

Qya

QTm Bedrock units,

 undivided

Top Qya = DEM

ThQya defined by well data

Top Qoa = (DEM - Qya thickness) Top Qoa = DEM; ThQoa = 0

Top Qya = DEM; ThQya = 0 Top Qya = DEM;

ThQya = 0

Top Qoa = DEM;

ThQoa = 0

Top QTm defined by well data

Top Qoa = DEM;

ThQoa defined

by well data

Base QTm (top of bedrock)

defined by well data

Base QTm = DEM;

ThQTm = 0

Top QTm = DEM;

ThQTm = 0 Top QTm = DEM; ThQTm = 0

Base QTm = 

Base Qoa

ThQTm = 0

Top Qya

Top Qoa

Top QTm

Base QTm

Bedrock units,

 undivided

DEM, Digital elevation model

Top Qya, elevation of the top of unit Qya

Top Qoa, elevation of the top of unit Qoa

Top QTm, elevation of the top of unit QTm

Base QTm, elevation of the base of unit QTm

(= elevation of top of bedrock)

ThQya , thickness of unit Qya

ThQoa , thickness of unit Qoa

ThQTm , thickness of unit QTm

DIAGRAMMATIC; NOT TO SCALE EXPLANATION

Qya, young alluvium

Qoa, older alluvium

QTm, Morales Formation

Geologic unit
3-D Geologic Framework Model 17

Construction of Gridded Surfaces

Gridded surfaces were interpolated from the data described 

in the previous sections. The approach for gridding the Qya 

and Qoa surfaces differed from that used for the QTm and 

bedrock surfaces as a result of differences and limitations of 

the data. The strategy for contouring each stratigraphic unit 

is presented in this section, and the final top altitude grids are 

presented.

Younger Allvium, Qya 

As the stratigraphically highest unit, the top of Qya is 

everywhere defined by the digital elevation model; the areal 

Figure 9. Conceptualization of the elevation and thickness of unit Qoa within the geologic framework model for the western part of the 

study area.

Qoa post-Qoa

pre-Qoa

pre-Qoa

1

Qoa

2

3

4

4

Study area boundary

Diagrammatic; not to scale EXPLANATION

Elevation of top of Qoa defined by thickness of Qya

Elevation of top of Qoa defined by DEM, thickness defined 

by well data

1

2

3

4

Elevation of top of Qoa defined by DEM, thickness defined 

arbitrarily at 175 m

Elevation of top of Qoa defined by DEM, thickness is zero

Qoa, outcrop of Qoa

post-Qoa, outcrop of units

 above Qoa (Qc and Qya)

pre-Qoa, outcrop of units below

 Qoa (QTm, BR1, and BR2)

Stratigraphic unit Definition of unit elevation and thickness

DEM, Digital elevation model

Qc, alluvial channel

Qya, young alluvium

Qoa, older alluvium

QTm, Morales Formation

BR1, Bedrock unit 1

BR2, Bedrock unit 2

Geologic unit

Table 2. Geologic units affected by Cuyama Valley faults.

[Qya, Younger alluvium; Qoa, Older alluvium; QTm, Morales formation]

Fault name Affected Geologic Units

Whiterock fault QTm only

Russell fault QTm only

South Cuyama fault QTm only

Morales fault Qoa and QTm

Santa Barbara Canyon fault Qoa and QTm

Graveyard Ridge fault Qya, Qoa, and QTm

Turkey Trap Ridge fault Qya, Qoa, and QTm

Rehoboth fault Qya, Qoa, and QTm
18 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

166

166

33

33

Shaded relief base created from 30-m digital elevation model from USGS 

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

Albers Projection, NAD83

 Sierra Madre Mountains

Carrizo

Plain

Cuyama

Badlands

Caliente Range

EXPLANATION

GRF, Graveyard Ridge fault

SBCF, Santa Barbara Canyon fault

TTRF, Turkey Trap Ridge fault

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

0 5 10 Miles

0 5 10 Kilometers

South Cuyama fault

fault

Russell

Morales

fault

Whiterock fault

GRF

TTRF

SBCF

Rehoboth

fault

KERN COUNTY

SAN LUIS 

OBISPO COUNTY

SANTA BARBARA COUNTY

VENTURA COUNTY

Cuyama River

Study-area boundary

Boundary of groundwaterflow model

Normal fault

Thrust fault

Thrust fault, concealed

1 to 1.9

2 to 24.9

25 to 49.9

50 to 99.9

100 to 149.9

150 to 193

Thickness of Qya, in meters

Qya is absent where uncolored

Wells with Qya 

thickness data

Oil and gas well

Water well

extent of the unit is defined by the geologic map (fig. 4). 

In parts of the framework model area, for example in the 

upstream reach of the Cuyama River, Qya is unconformable 

on and incises into older units. Accurate portrayal of these 

stratigraphic relations is aided by the construction of a thickness map for Qya that can then be superimposed upon the 

older units within the framework model.

A map of the total areal extent of Qya was created by 

merging the mapped polygons of Qya and Qc in a GIS. Inside 

of the unit extent polygon, Qya thickness data from oil and 

gas wells and water wells (fig. 10) were contoured. In cases 

where a well bottomed within Qya, the thickness of Qya was 

constrained to be thicker than the total depth of the well at 

that location. This initial Qya thickness grid was hand-edited 

in alluvial channel areas that lacked well control as guided 

by thickness trends evident from well data along the main 

channel of the Cuyama River and its major tributaries. Qya 

thickness was assigned according to stream rank, such that the 

third-order stream of the Cuyama River channel was given the 

thickest sediments, second-order streams that were tributaries 

to the Cuyama River were given the next-greatest thickness, 

and first-order streams that were tributaries to the second-order 

streams were given the least thickness. The thickness grid was 

modified with the intent of connecting similar thickness values 

and creating smoothly-varying changes. The hand-edited grid 

was smoothed and then clipped with the unit extent boundary 

to create a final thickness map (fig. 10).

Figure 10. Map showing modeled thickness of 

the younger alluvium, Qya.
3-D Geologic Framework Model 19

Older Alluvium, Qoa

The elevation of the top of Qoa is defined by the base of 

Qya, so that the thickness of Qya was subtracted from the 

digital elevation model to yield the top of Qoa (fig. 11). The 

top defines a west-northwest to east southeast trending trough 

that is aligned with axis of the valley, but skewed toward the 

north side of the basin against the base of the Caliente Range. 

This pattern is reflected by the surficial geology, where Qoa 

is uplifted and exposed along the south side of the basin as 

upland alluvial terraces (fig. 4), but buried by younger materials on the north side of the basin. Local linear troughs are 

present at alluvial channels draining the Sierra Madre Mountains, such as Santa Barbara Canyon and Salisbury Canyon 

(fig. 11), and result from incision of the older alluvium by 

young stream courses during recent uplift of the Sierra Madre 

Mountains (DeLong and others, 2008, 2011).

Qoa crops out where it is structurally uplifted by the Turkey 

Trap Ridge and Graveyard Ridge faults (fig. 11). To the south 

of these faults, well data showed that the top of Qoa is buried 

by as much as 200 m of Qya. The Rehoboth fault and Santa 

Barbara Canyon fault do not have a discernible effect on 

the elevation of Qoa at the scale at which Qoa is contoured 

(fig. 11).

166

166

33

33

Shaded relief base created from 30-m digital elevation model from USGS 

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

Albers Projection, NAD83

 Sierra Madre Mountains

Carrizo

Plain

Cuyama

Badlands

Caliente Range

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

0 5 10 Miles

0 5 10 Kilometers

South Cuyama fault

fault

Russell

Morales

fault

Whiterock fault

GRF

TTRF

SBCF

Rehoboth

fault

KERN COUNTY

SAN LUIS 

OBISPO COUNTY

SANTA BARBARA COUNTY

VENTURA COUNTY

Cuyama River

EXPLANATION

GRF, Graveyard Ridge fault

SBCF, Santa Barbara Canyon fault

TTRF, Turkey Trap Ridge fault

Study-area boundary

Boundary of groundwater-flow model

Normal fault

Thrust fault

Thrust fault, concealed

Elevation of top of Qoa, in 

meters above NAVD 88

Qoa is absent where uncolored

less than 500

501 to 600

601 to 700

701 to 800

801 to 900

901 to 1,000

greater than 1,000

Figure 11. Map showing the modeled elevation of the top 

of the older alluvium, Qoa.
20 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

Morales Formation, QTm

Subsurface data for the QTm are clustered in the vicinity 

of the two producing oil and gas fields and are sparse in the 

southeastern part of the study area (black circles in fig. 12). 

A computer-contoured map of the top of the QTm, generated 

from only the well and outcrop data, produced unsatisfactory 

results that did not reflect the synclinal structure in the southeastern part of the study area. To improve horizon gridding, 

a generalized structural contour map of the top of the QTm 

was drawn by hand that honored the outcrop data and contact elevation from boreholes and that defined a broad, open 

syncline consistent with the map trace of the Cuyama syncline and with seismic reflection data (Ellis and Spitz, 1987; 

Ellis, 1994). Structure contours were converted to a series of 

regularly-spaced points, which were assigned coordinate locations and given the contoured elevation value (purple dots in 

fig. 12). These points became part of the input data for horizon 

gridding of the top of the QTm.

The top of the QTm generally defines an asymmetric westnorthwest to east southeast trending trough that is aligned with 

axis of the valley, such that the unit is deepest along the north 

side of the basin against the base of the Caliente Range and 

is shallowest along the south side of the valley (fig. 13). In 

Figure 12. Map showing geologic data used to map the top of the Morales Formation, QTm.

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

0 5 10 Miles

0 5 10 Kilometers

Shaded relief base created from 30-m digital elevation model from USGS

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

Albers Projection, NAD83

Cuyama River

 Sierra Madre Mountains

Caliente Range

Cuyama

Badlands

EXPLANATION

Geologic unit

Qc, alluvial channel

Qya, young alluvium

Qoa, older alluvium

QTm, Morales Formation

BR1, bedrock unit 1

BR2, bedrock unit 2

GRF, Graveyard Ridge fault

SBCF, Santa Barbara Canyon fault

TTRF, Turkey Trap Ridge fault

Study-area boundary

Normal fault

Thrust fault

Thrust fault, concealed

Generalized geologic units

All units above Morales 

Formation (Qc, Qya, Qoa)

QTm, Morales Formation

All units below Morales 

Formation (BR1, BR2)

Geologic data used to map the top of QTm

Mapped contact at surface

Subsurface contact from well data

Limiting value of contact elevation, 

from well data

Unit base elevation defined by 

structure contour
3-D Geologic Framework Model 21

the southeastern end of the valley, the trough trends parallel 

to the axis of the Cuyama syncline. The northwest-striking 

Russell and Rehoboth faults are both associated with relative 

highs in the top of the QTm (fig. 13). The unit is elevated on 

the southwest side of the Russell fault, whereas the Rehoboth 

fault roughly is centered on a structural high in the top of the 

QTm (fig. 13). The structurally elevated Morales Formation, 

next to the Russell and the Rehoboth faults, could be the result 

of transpression-related uplift as the tectonic regime changed 

from transcurrent to compressional faulting in the Pliocene. 

The small-offset Santa Barbara Canyon fault does not have a 

discernible effect on the elevation of the QTm at the scale at 

which the unit is contoured (fig. 13).

Pre-Morales Formation (QTm) Bedrock

Sparse well control on the elevation of pre-QTm bedrock 

was augmented by a generalized structural contour map of the 

base of the QTm that used the mapped trace of the Cuyama 

syncline to define the shape of the contour lines in the southeastern part of the study area (purple dots in fig. 14). Additional subsurface data (purple dots shown within thesis study 

areas, fig. 14) were obtained from detailed structure contour 

maps of the base of the QTm in the vicinity of the Russell 

Ranch oil field (Nevins, 1982) and the South Cuyama oil field 

(Schwing, 1984). Structure contours were converted to a series 

M

M

M

M

166

166

33

33

Shaded relief base created from 30-m digital elevation model from USGS 

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

Albers Projection, NAD83

 Sierra Madre Mountains

Carrizo

Plain

Cuyama

Badlands

Caliente Range

EXPLANATION

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

0 5 10 Miles

0 5 10 Kilometers

South Cuyama fault

fault

Russell

Morales

fault

Whiterock fault

GRF

TTRF

SBCF

Rehoboth

fault

KERN COUNTY

SAN LUIS 

OBISPO COUNTY

SANTA BARBARA COUNTY

VENTURA COUNTY

Cuyama River

M

Cuyama

syncline

GRF, Graveyard Ridge fault

SBCF, Santa Barbara Canyon fault

TTRF, Turkey Trap Ridge fault

Study-area boundary

Boundary of groundwater-flow model

Normal fault

Thrust fault

Thrust fault, concealed

201 to 400

401 to 600

601 to 800

801 to 1,000

1,001 to 1,200

1,201 to 1,400

1,401 to 1,600

1,601 to 1,800

Elevation of top of QTm, in 

meters above NAVD 88

QTm is absent where uncolored

Syncline, showing 

plunge direction

Syncline, concealed Figure 13. Modeled elevation of the top of the 

Morales Foramtion, QTm.
22 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

of regularly-spaced points that were assigned coordinate locations and given the contoured elevation value. These points 

became part of the input data for horizon gridding of the top of 

the pre-QTm bedrock (fig. 14).

The elevation of the top of the bedrock emphasizes the 

fault-bounded nature of the basin, where pre-QTm bedrock 

crops out to the north and south of the basin, but abruptly 

drops to great depths within the basin (fig. 15). The structural 

trough of the Cuyama syncline is evident in the eastern half of 

the basin and in the Cuyama Badlands (fig. 15). The Russell 

fault offsets the top of bedrock by as much as 500 m (Nevins, 

1982). The Rehoboth and Santa Barbara Canyon faults do not 

disrupt the contoured elevation of the top of bedrock at the 

contouring interval shown on figure 15.

3-D Geologic Framework Model Results

The final 3-D-geologic framework was compiled with the 

Rockworks 3-D modeling package, which allows individual 

gridded surfaces to be stacked in stratigraphic order. Unit 

Figure 14. Geologic data used to map the top of the pre-Morales Formation (QTm) bedrock.

M

M

M

M

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

0 5 10 Miles

0 5 10 Kilometers

Shaded relief base created from 30-m digital elevation model from USGS

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009 

Albers Projection, NAD83

Cuyama River

 Sierra Madre Mountains

Caliente Range

Cuyama

Badlands

Cuyama

syncline

EXPLANATION

M

Geologic unit

Qc, alluvial channel

Qya, young alluvium

Qoa, older alluvium

QTm, Morales Formation

BR1, bedrock unit 1

BR2, bedrock unit 2

Normal fault

Thrust fault

Thrust fault, concealed

Syncline, showing plunge direction

Syncline, concealed

Study-area boundary

Thesis study area, Nevins (1983)

Thesis study area, Schwing (1983)

Generalized geologic units

All units above Morales 

Formation (Qc, Qya, Qoa)

QTm, Morales Formation

All units below Morales 

Formation (BR1, BR2)

Geologic data used to map the top of 

pre-QTm bedrock

Mapped contact at surface

Subsurface contact from well data

Limiting value of contact elevation, 

from well data

Unit base elevation defined by 

structure contour
3-D Geologic Framework Model 23

thickness is represented by the difference between altitudes of 

successive stratigraphic tops, such that the altitude of the base 

of a unit is always equal to the altitude of the top of the unit 

directly below it in the stacking order. 

The results from the geologic framework model can be 

explored and visualized by slicing the model volume at any 

chosen location, as shown in a perspective view looking from 

above to the east (fig. 16). In the upper part of the figure, the 

Figure 15. Modeled elevation of the top of bedrock.

166

166

33

33

M

M

M

M

Shaded relief base created from 30-m digital elevation model from USGS 

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

Albers Projection, NAD83

 Sierra Madre Mountains

Carrizo

Plain

Cuyama

Badlands

Caliente Range

EXPLANATION

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

0 5 10 Miles

0 5 10 Kilometers

South Cuyama fault

fault

Russell

Morales

fault

Whiterock fault

GRF

TTRF

SBCF

Rehoboth

fault

KERN COUNTY

SAN LUIS 

OBISPO COUNTY

SANTA BARBARA COUNTY

VENTURA COUNTY

Cuyama River

Cuyama

syncline

QTm, Morales Formation

GRF, Graveyard Ridge fault

SBCF, Santa Barbara Canyon fault

TTRF, Turkey Trap Ridge fault

Study-area boundary

Boundary of groundwater-flow model

Normal fault

Thrust fault

Thrust fault, concealed

Syncline, showing plunge direction

Syncline, concealed

Elevation of top of bedrock, 

in meters above NAVD 88

less than −750

−749 to −500

−549 to −250

−249 to 0

1 to 250

251 to 500

501 to 750

751 to 1,000

1,001 to 1,250

greater than 1,250

QTm outcrops; top of QTm 

at land surface

QTm eroded; pre-QTm 

units at land surface

M
24 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

upper surface of the geologic framework is trimmed with a 

digital elevation model, creating a map of the geologic units 

predicted by the model to be present at land surface. The patterns of the geologic units at land surface are similar to the 

geologic map of the basin (fig. 4), providing a first-order check 

on the model’s validity. In this view, extensive outcrops of the 

QTm are present in the Cuyama Badlands and at the western 

edge of Cuyama Valley; both areas match known surface 

exposures. Outcrops of Qoa are extensive along the south side 

of Cuyama Valley and are also present as uplifted blocks at the 

two fault-bounded ridges at the north side of the valley. The 

modeled extent of young alluvial Qya occupies the center of 

the valley and outlines the trace of the Cuyama River channel to the west of the Cuyama Badlands, following mapped 

surface outcrops.

Figure 16. Perspective views of vertical slices through the geologic framework model.

EASTING, IN METERS

ELEVATION,

IN METERS

280,000

260,000

240,000

300,000

3,880,000

3,870,000

3,860,000 3,850,000

-1,000

1,000

0

EASTING, IN METERS

ELEVATION, 

IN METERS

280,000

260,000

240,000

300,000

3,880,000 3,870,000 3,860,000 3,850,000

-1,000

1,000

0

NORTHING, IN METERS

NORTHING, IN METERS

Colors appear variable because of the effects of lighting from the north

Young alluvium (Qya) Morales Formation (QTm)

Old alluvium (Qoa) Bedrock, undivided

N

Range Caliente

Sierra Madre

Mountains

Cuyama

Badlands

EXPLANATION

Cuyama Valley

Upper figure shows the upper surface of the geologic framework model 

trimmed with a digitial elevation model, such that the upper surface of the 

geologic framework approximates a geologic map of the study area. The 

lower figure shows vertical sections that are cut through the geologic 

framework model in the north-south and east-west directions, showing the 

configuration of stratigraphic unit tops within the model volume. 

View is from the west (280 degrees) looking to the east from an elevation of

20 degrees above the horizon. Upper figure has no vertical

exaggeration; lower figure has a vertical exaggeration of 3X.

Horizonal and vertical scales are variable

because of the effects of

perspective view.
3-D Geologic Framework Model 25

The lower part of figure 16 shows a series of 

east-west and north-south vertical sections cut 

through the geologic framework model; these 

vertical sections allow for the visualization of 

the modeled stratigraphic unit tops beneath the 

valley. This figure shows the thickness of Qya 

in the axis of the valley, underlain by Qoa. The 

Qoa dominates the southern part of the valley, 

beneath its outcrop exposures, with the QTm 

underlying it. The QTm predominates in the 

Cuyama Badlands area, where it is essentially the 

only permeable stratigraphic unit, except for thin 

younger alluvium along the trace of the Cuyama 

River channel. The QTm is also exposed at the 

surface in the western part of the valley, where 

it is locally overlain by thin deposits of alluvium 

in the channel of the Cuyama River. The effect 

of fault offset is not obvious at the scale of figure 

16, except for the appearance of Qoa at land surface at Graveyard Ridge and Turkey Trap Ridge 

(upper figure, fig. 16) and the abrupt change in 

elevation of Qoa beneath these ridges that can 

be identified in two vertical panels (lower figure, 

fig. 16).

Singer and Swarzenski (1970) published two 

cross sections showing the configuration of the 

water-bearing units in Cuyama Valley as interpreted from well control. One cross section was 

aligned roughly east-west (A-A′, fig. 4), parallel to 

the trace of the interbasin thrust faults that bound 

the Turkey Trap Ridge and Graveyard Ridge, 

and a roughly north-south section was transverse 

to the major structural grain of the basin (B-B′, 

fig. 4). These sections were compared to the modeled elevation of the stratigraphic units from the 

geologic framework model along the same line of 

section (fig. 17).

The greatest difference between the previously 

published sections and the stratigraphic tops, as 

defined in the geologic framework model, is the 

elevation of the top of the QTm and the definition of Qoa. The QTm in the geologic framework model is almost everywhere 400 to 600 ft 

deeper than the previously published interpretation (figs. 17A and B). The previously published 

interpretation of the QTm as portrayed on the 

north-south section B-B′ (fig. 17B) followed the 

geologic mapping of Dibblee (Dibblee, 1973; 

Graham and others, 1999; Dibblee and Minch, 

2005b,c, 2007), which included all young, 

deformed, non-marine sediments of the Cuyama 

area in the Morales Formation. By using these 

criteria, the upland area that lies to the south of 

Cuyama Valley and north of the Sierra Madre 

Mountains was interpreted on the previously 

published section as being composed of exposed 

Figure 17. Cross sections showing previous hydrogeologic interpretation and elevation of stratigraphic unit tops from the geologic framework model. 

A, east-west section A-A’; 

B, north-south section B-B’.

pTn

pTn

Tm

Qya

Qoa

Qya, Qoa Qya, Qoa

Qya, Qoa

Qya

Qoa

Tm

Tm

Tm

?

Water level – 1966Water level – 2008

B-B’ Section 

Whiterock

fault

Russell

fault

Morales

fault

00 1 2 3 4 Kilometers

1 2 3 4 Miles

E

A'

A

W

3,0002,6002,2001,8001,4001,000

600200

Feet

Altitude, in feet above mean sea level A

Vertical exaggeration 26X Section location shown on figure 4

QTm

Qoa

Qya

Section subparallel to Whiterock and Turkey Trap Ridge faults

Faults

Fault, Singer and Swarzenski (1970) 

and this study

This study only

EXPLANATION

Hydrogeologic units

(Singer and Swarzenski, 1970)

Qya and Qoa, alluvium undividedTm, Morales FormationpTn, pre-Tertiary non-waterbearing rocks 

Stratigraphic units, this study

(lines represent the elevation of the top of 

unit from the geologic framework model)

Qya, younger alluviumQoa, older alluviumQTm, Morales Formation
26 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

outcrops of Morales Formation (fig. 17B). Subsequent workers 

(Vedder, 1968; Vedder and Repenning, 1975; Schwing, 1984; 

Spitz, 1986; Kellogg and others, 2008) classified the upper 

part of Dibblee’s mapped Morales Formation as “deformed 

older Quaternary alluvium,” thus putting the Morales Formation a few hundred meters in the subsurface on the south side 

of Cuyama Valley, rather than exposed at the surface. Data 

from electric logs that were used in the construction of the 

geologic framework consistently place the top of the QTm 

deeper than Singer and Swarzenski (1970).

A second difference between information from previous 

publications and the model output is the definition of the top 

of the older alluvial unit Qoa, which was not subdivided from 

younger alluvium in previously published sections (figs. 17A

and B). Qoa in the geologic framework model includes both 

the lower part of the previously defined undivided Qya/Qoa 

Figure 17. Cross sections showing previous hydrogeologic interpretation and elevation of stratigraphic unit tops from the geologic 

framework model. B, north-south section B-B’.—Continued

pTn

pTn

Tm

Tm

Qya

Qoa

Water level - 1966

Water level - 2008

Section A-A’

3,000

2,600

2,200

1,800

1,400

1,000

600

200

Sea level

Feet

Altitude, in feet above mean sea level

S

B B

N

B'

0

0 1 2 3 4 Kilometers

1 2 3 4 Miles Morales fault

South Cuyama fault

Faults

Fault, Singer and Swarzenski 

(1970) and this study

This study only

EXPLANATION

Vertical exaggeration 26X

Section location shown on figure 4

Hydrogeologic units

(Singer and Swarzenski, 1970)

Qya and Qoa, alluvium 

undivided

Tm, Morales Formation

pTn, pre-Tertiary nonwater-bearing rocks 

Stratigraphic units, this study 

(lines represent the elevation of the 

top of unit from the geologic 

framework model)

Qya, younger alluvium

Qoa, older alluvium

QTm, Morales Formation

QTm

Qoa

Qya

Rehoboth fault

and the upper part of the previously defined Morales Formation. For the geologic framework model, Qoa was subdivided 

from Qya primarily on the basis of degree of cementation. 

Differences in how such cementation was described in well 

drillers’ reports could account for some of the irregularities in 

the elevation on the top of Qoa seen in section A-A′ (fig. 17A). 

The topographic surface used for the previously published sections was generalized and ignored local irregularities, resulting in the shallow modeled unit tops appearing to go above 

the previously portrayed land surface on the western edge of 

section A-A′. The sections showed general agreement on the 

location and character of the main basin-bounding faults. The 

geologic framework model adds the Russell fault at depth on 

the west edge of section A-A′ and the Rehoboth fault on section B-B′ (fig. 16).
Textural Analysis of Basin-Filling Unit 27

Figure 18. Location of wells used for textural analysis in Cuyama Valley.

166

166

33

Carrizo 33

Plain San Joaquin Valley

Cuyama

Badlands

Caliente Range

Cuyama River

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

Sierra

Madre

Mountains

EXPLANATION

Shaded relief base created from 30-m digital elevation model from USGS 

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

Albers Projection, NAD83

Cuyama Valley

groundwater

basin

Study-area boundary

Wells used for sediment textural analysis

Oil and gas well

Water well

Geologic units

Qc, active channel

Qya, young alluvium

Qoa, older alluvium

QTm, Morales Formation

All units below Morales Formation 

(BR1, BR2)

0 5 10 Miles

0 5 10 Kilometers

Textural Analysis of Basin-Filling Unit

An analysis of variability of lithology and grain size was 

completed for the three principal basin-filling units, Qya, Qoa, 

and the QTm. Textural data, such as grain size, sorting, and 

bedding characteristics, form the geologic basis for estimating 

the hydraulic properties within a numerical hydrologic-flow 

model (Burow and others, 2004; Faunt and others, 2010). 

Textural variability in the basin-filling units is ultimately a 

function of the sedimentary facies, environment of deposition, and depositional history of the basin. Textural data were 

compiled from 65 oil and gas and 153 water wells in the study 

area (fig. 18).

Textural Variations Observed in Outcrop

The Morales Formation is composed of up to 1,500 m of 

weakly indurated fluvial and alluvial sediments deposited in an 

extensive valley area. The unit is exposed in the Cuyama Badlands, is present in the subsurface beneath Cuyama Valley, and 

is also exposed on the north flank of the Caliente Range along 

the edge of the Carrizo Plain (fig. 4), where it was deposited 

prior to the thrust-related uplift of the range. In outcrop, the 

Morales Formation can be informally divided into a more 

poorly sorted, generally coarse-grained upper unit and a wellsorted, generally finer-grained lower unit (Dibblee and Minch, 

2005a, 2006; Kellogg and others, 2008). The upper part of 

the Cuyama Badlands is about 700 m thick and is composed 

of weakly indurated, poorly sorted, matrix-supported cobblepebble conglomerate in a sandstone matrix (fig. 19A). The 
28 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

Figure 19. Outcrop expression of textural variations in basin-filling units: A, Morales Formation; B, Older alluvium.

Morales Formation, Quatal Canyon

Lower part of

Morales Formation

Channel

Channel

Channel

Boulder bed

Upper part of

Morales Formation

6 m

10 m

B. Qoa, along Highway 166, 5 kilometers west of New Cuyama

A. 

Photograph by Donald Sweetkind, U.S. Geological Survey

Photograph by Donald Sweetkind, U.S. Geological Survey
Textural Analysis of Basin-Filling Unit 29

lower part is composed of about 650 m of thick- to massivelybedded arkosic sands with interbeds of pebble conglomerate 

and sandy siltstone (fig. 19A). In western Cuyama Valley, the 

lower part of the Morales Formation consists of about 400 m 

of gypsiferous lacustrine claystones that are conformably 

overlain by 500 m of sand and gravel.

The great thickness of thick-bedded to massively bedded 

arkosic sands, large area of deposition, and general lack of 

matrix-supported gravel deposits or well-defined channels 

indicate that the Morales Formation could have been deposited 

in a large streamflow-dominated alluvial fan system. Comglomerate clasts are a mixture of granitic rocks, gneiss, schist, 

quartzite, andesite, and basalt, whose sources are outcrops of 

crystalline rocks near the San Andreas fault, 20–30 km southeast of Cuyama Valley (Dibblee, 1982; Ellis, 1994; Kellogg 

and others, 2008). These clasts are evidence of long-distance 

transport from sediment sources at the margins of the broad 

depositional basin. Well and seismic-reflection data indicated 

that fine-grained intervals within the Morales Formation can 

be correlated in the subsurface for several kilometers. 

Older alluvial deposits often consist of a sequence of 

boulder, clast-supported alluvial channel deposits separated by 

sandy interbeds (fig. 19B). Boulder clasts are typically of local 

origin and reflect nearby sources; deposits on the south side 

of Cuyama Valley often are dominated by clasts of Eocene 

sandstones derived from the Sierra Madre Mountains, whereas 

deposits on the northern side of the valley have a large proportion of Monterey shale clasts derived from the Caliente Range. 

Channel deposits are local-scale features that cannot be correlated for long distances. Younger alluvial deposits exposed 

in incised arroyos along the Cuyama River are dominated 

by tabular beds of fine to medium sand (DeLong and others, 

2011).

The spatial distribution and sediment characteristics of the 

three basin-filling units are related to the Pliocene and Pleistocene tectonic evolution and uplift of the basin, the progressive 

narrowing of the valley, and the gradually increasing channelization of the Cuyama River drainage. The QTm is a widespread unit that was deposited prior to the constriction of the 

basin by encroaching thrust faults. The sediment supply to the 

QTm was from relatively distant sources, and the unit appears 

to have been deposited by streams in which the channel system was broad and poorly bounded. The inception of Pliocene 

compression and uplift caused thrust-bounded bedrock highlands to impinge upon the valley, and the drainages became 

more restricted to channels and, perhaps, higher gradient. As a 

result of tectonic uplift, previously deposited Morales Formation was exposed and eroded, feeding reworked sediment into 

a narrower basin, which resulted in the deposition of Qoa. 

Qya is confined to the center of Cuyama Valley and alluvial 

channels tributary to the Cuyama River. Textural variations in 

Qya appear to be primarily climate-driven and reflect regional 

rainfall variations that control stream incision and aggradation.

Texture Derived from Drill-Hole Data

Textural data were derived by using drillers’ lithologic logs 

from water wells and by interpretation of electric logs from oil 

and gas wells. Water wells yielded data for lithologic intervals 

in the younger part of the section, primarily from Qya and the 

upper part of Qoa, whereas the oil wells yielded data primarily from QTm and the lower part of Qoa. The two types of 

wells produced different textural parameters; lithologic logs 

from water wells could be interpreted in terms of sediment 

grain size and the degree of sorting, whereas oil wells yielded 

textural parameters of grain size and bedding frequency.

Oil and Gas Wells

Textural data were derived from 65 oil and gas wells 

(fig. 18) by analyzing the electrical geophysical logs. The presence of fresh water as pore fluids in sand and gravel aquifers 

results in rightward deflections on resistivity logs to higher 

resistivity values and in leftward deflections to more negative 

values on the SP log; clays and shales are generally conductive 

and have low values of resistivity with rightward deflections 

to more positive values on the SP logs (Wyllie, 1957; Keys 

and MacCary, 1971; Johnson and Pile, 2002; fig. 20). Textural 

analysis used the deflection of the SP curve in the electric logs 

to approximate the sand-shale ratio, which is a technique often 

used in consolidated sand-shale sequences (Wyllie, 1957; 

Johnson and Pile, 2002), although not frequently applied to 

continental basin-fill deposits. Spontaneous potentials occur 

near boundaries between shale or clay and coarse-grained 

deposits. The polarity and amplitude of the SP-log deflection 

depend on lithology and the salinities of both the formation 

water and the borehole fluid. Assuming that coarse-grained 

and fine-grained beds within Qoa and QTm have similar 

formation water salinities, the sand-shale interpretations were 

made in reference to a shale baseline that was drawn on each 

electric log connecting the SP-log deflections to the most positive values. This shale baseline was defined by using SP-log 

deflections for the entire thickness of QTm and the underlying 

fine-grained Quatal Formation below. A sand line was constructed roughly parallel to the shale baseline by connecting 

the maximum deflections to negative values on the SP log. 

Variation of the SP curve between the maximum deflections is 

due to a variety of factors, including the relative clay content 

of the formation and the damping effect of thin beds, which 

tend to reduce the SP deflection even in cases of clean sands 

interbedded with pure shale (Wyllie, 1957; Keys and MacCary, 1971; Johnson and Pile, 2002). 

The 100-mV scale of the SP curve was divided into 

four categories that corresponded to relative-size fractions, 

described as coarse, medium, fine and very fine (fig. 20). The 

finest and coarsest relative-size fractions were each assigned 

a 30-mV range (six vertical divisions, fig. 20); the middle 

two relative-size categories each occupied 20-mV range on 

either side of the zero value. These divisions were assigned 

on the basis of the maximum SP-log deflections observed in 
30 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

Figure 20. Example electric log from oil and gas well showing derivation of textural data.

4,900

4,800

4,700

4,600

4,500

4,400

4,300

4,200

4,100

4,000

3,900

3,800

3,700

3,600

3,500

3,400

3,300

3,200

3,100

3,000

0 -25-50 50250 403020100

Resistivity,

in Ohm-meters

Spontaneous

potential,

in millivolts

C M F VF

C, coarse; M, medium; 

F, fine; VF, very fine.

100

Percentage

sand

10x scale change.

Texture

class

Fine

massive

Fine 

interbedded

Very fine

interbedded

Very fine

massive

Explanation of

texture class

Depth, in feet below land surface

Clay, predominantly kaolinite; minor quartz 

sand.

Clay, with minor very fine to very coarse 

quartz sand.

Dark gray sandy siltstone.

Core: Very fine to very coarse massive 

micaceous quartz sandstone.

Very fine to very coarse quartz sand with 

minor clay.

Very fine to coarse quartz sand, clay and 

minor micaceous siltstone.

Very fine to coarse quartz sand and minor 

micaceous siltstone.

Red brown siltstone.

Yellow clay and sandy siltstone.

Light gray clay and siltstone.

Very fine to coarse quartz micaceous sand 

and minor quartz pebbles.

Sand; SP log probably affected by presence of 

fresh water in formation.

Description from mudlog and core

Core: Micaceous sandy siltstone.
Textural Analysis of Basin-Filling Unit 31

the Miocene rocks beneath the Morales Formation, where 

shale and sandstone were penetrated. The upper parts of the 

boreholes were logged by using the same SP-log scale as 

the deeper section, so that the magnitude of the deflection 

could be roughly calibrated to a known grain size. Down-hole 

intervals were then assigned a relative grain size on the basis 

of the location of the SP-log curve with respect to the category 

boundaries. Qoa tended to be characterized by numerous 

intervals that had SP-log deflections to large negative values 

that were described as coarse or medium relative-size fractions, whereas QTm tended to be characterized by relatively 

monotonous SP-log response in the fine to fine relative-size 

fractions.

Down-hole intervals were also classified by bedding 

frequency and described as either massive or interbedded 

(fig. 20). Massively bedded intervals were those where the 

SP curve remained within a relative-size category for at least 

20 ft; interbedded intervals were characterized by frequent 

alternation between relative-size fractions at the scale of 

several feet in thickness. Thin beds tend to dampen the full 

response of the SP logging tool because the tool spans the 

thickness of multiple beds and integrates the spontaneous 

potentials developed at multiple unit contacts. For these units, 

the SP curve was augmented by the higher-resolution peaks 

of the resistivity curves to qualitatively discriminate between 

massively bedded units and thinly interbedded units.

The relative-size fractions derived from SP-log analysis 

compared favorably to mud-log descriptions, percentage 

sand analysis, and descriptions from sidewall cores (fig. 20). 

Although mud-log descriptions include a wide range of grain 

sizes, intervals described as siltstone corresponded to rightward deflections to more positive values on the SP logs that 

were classified as very fine, whereas sand-bearing intervals 

were consistently interpreted in the fine grain size class 

(fig. 20). Where lithologic descriptions were more general or 

applied to a large downhole interval, there was a general correspondence between the logged sand percentage and the SPlog results, such that sand-poor intervals corresponded to an 

interpreted grain-size class of very fine (fig. 20). Correspondence between observed lithology and interpreted grain-size 

class was strongest where relatively thick beds of uniformly 

coarse material were penetrated. Thin-bedded deposits tended 

to be described as mixtures of grain-size fractions in the mud 

logs. Shale or clay intervals recorded in the mud log rarely 

correlated well with a clear shale line on the SP-log, which, 

perhaps, was a result of the interbedded nature of the deposits 

or of the lag in cutting return coming up the drill hole. In some 

cases, the fine-grained fraction could have been underrepresented in the mud log when the drill cuttings were washed to 

remove drilling mud and fluids.

Water Wells

Textural data were derived from drillers’ lithologic logs 

from 153 water wells in the study area (fig. 18). Drillers’ 

descriptions are generally short phrases that accompany a 

significant lithologic change. Typically, descriptions range 

from one to ten words that describe a change recognized by 

the driller as the drill penetrates a different unit; for example, 

descriptions can include information on grain size, presence 

or absence of gravel or large rocks, degree of consolidation, 

and rock type or abrupt color changes. Each lithologic log was 

divided into a discrete binary texture classification of either 

“coarse grained” or “fine grained” intervals on the basis of the 

description in the log. In this study, coarse-grained sediment 

is defined as consisting of sand, gravel, pebbles, boulders, 

cobbles, or conglomerate. Fine-grained sediment is defined as 

consisting principally of clay, lime, loam, mud, or silt. These 

definitions of “coarse grained” and “fine grained” are similar to those originally defined by Page (1986) and later used 

by Laudon and Belitz (1991), Belitz and others (1993), and 

Burow and others (2004).

2-D and 3-D Models of Textural Data

Numerical hydrologic-flow models must represent the 

hydraulic conductivity of aquifers throughout the model volume. This can be accomplished through a 3-D array of values 

(Burow and others, 2004; Faunt, 2009) or as a 2-D representation in plan view where the model domain is subdivided into 

zones that represent areas with the same hydraulic properties 

within individual aquifers (Faunt, Blainey, and others, 2010). 

Textural data were analyzed in both 2-D and 3-D to help 

define textural variations in the Cuyama Valley groundwater 

basin in ways potentially useful for a numerical hydrologicflow model. Ultimately, sediment grain size, a textural parameter common to both the oil and water well data, was modeled 

by using geostatistical methods to produce 2-D estimates of 

grain-size variability for each principal basin-filling unit.

3-D Model of Textural Data from Oil Wells

The interpreted grain-size and bedding-frequency parameters derived from the oil and gas exploration holes were used 

to construct a 3-D solid model of textural variations within the 

basin by extrapolating data away from boreholes by using a 

nearest-neighbor 3-D-gridding process within a 3-D software 

modeling package (fig. 21). The 3-D-gridding process is a 

cell-based modeling approach where solid-model cell nodes 

are sequentially assigned properties outward horizontally from 

each borehole in circles of increasing diameter. The approach 

is a simple spatial interpolation method that does not consider 

spatial structure of the data. Cell dimensions for the modeling 

were 500 m in the horizontal dimensions and 10 m in the vertical dimension. The x,y cell dimensions were chosen to mimic 

the closest spacing of the oil and gas wells, and the vertical 

dimension was chosen to preserve the textural detail obtained 

from the SP-log analysis. The extrapolated lithologic data in 

the resulting solid model have the appearance of stratigraphic 

units with aspect ratios that emphasize the horizontal dimension relative to the vertical dimension.

A series of vertical northwest-southeast and northeastsouthwest sections through the 3-D solid lithologic model 
32 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

EASTING, IN METERS

NORTHING, IN METERS

820,000

810,000

800,000

3,880,000

ELEVATION, IN METERS

1,000

-1,000

0

3,870,000

3,860,000

1,000

-1,000

0

-2,000

Universal Transverse Mercator Projection, Zone 10 North American Datum 1983.

View is from the northeast (250 degrees) looking to the east

from an elevation of 60 degrees above the horizon. Vertical

exaggeration is 3X. Horizonal and vertical scale 

is variable because of the effects of perspective view.

N

Colored cylinders represent textural intervals from oil 

and gas wells. Vertical panels are slices through soild 3D

textural model. Wells and model are colored by textural 

class. Colors appear variable because of the effects of

lighting from above and the southeast.

Qoa

QTm

Coarse, massive

Coarse, interbedded

Medium, massive

Medium, interbedded

Fine, massive

Fine, interbedded

Very fine, massive

Top of QTm

Very fine, interbedded

EXPLANATION

Texture units

Qoa, older alluviumQTm, Morales Formation

Geologic unit

0 5 1 2 3 4 Miles

0 1 2 3 4 5 Kilometers

Well with  textural data

Line of section

Location map of oil and gas wells used intextural anaylsis and vertical sectionscut through 3D textural model

Geologic units as in figure 4

Figure 21. Perspective view showing results of 3-D textural modeling from oil and gas well data.
Textural Analysis of Basin-Filling Unit 33

portray the lithologic variability of the basin fill in the Cuyama 

Valley region as extrapolated from the oil and gas borehole 

data (fig. 21). The upper surface of the 3-D solid lithologic 

model is clipped at the topographic surface by using a digital 

elevation model; the base of the model is clipped with the 

modeled base of QTm. Mountainous regions that are underlain 

by bedrock around the basin margins are uncolored (fig. 21). 

The 3-D solid model shows the relative extents of coarseand fine-grained sediments in the shallow subsurface and 

highlights textural differences between the Qoa and QTm units 

(fig. 21). Qoa is generally coarser than the QTm and has more 

numerous medium- and coarse-grained lenses, which probably 

represent alluvial channel deposits. The QTm has relatively 

few coarse-grained intervals and is characterized by relatively 

fine-grained material, particularly in the axis of the valley 

where Qoa contains some of the coarsest intervals. The QTm 

becomes more coarse-grained along the southern flank of the 

valley and to the southeast, perhaps reflecting available sediment supply from uplifting areas outside the valley.

The 3-D modeling approach was ultimately limited by the 

extrapolation methodology. The method preserved the local 

variability of the lithology where data were abundant, but 

resulted in poorer extrapolation where drill holes were widely 

spaced and the outlying points influenced a large part of the 

model volume. A series of plan-view zones of texture variation was envisioned as input for the numerical flow model, and 

2-D extrapolation methods, described in the following section, 

were ultimately used rather than the 3-D approach.

2-D Models of Textural Data

Geologic or hydrogeologic units are the basis for assigning 

horizontal hydraulic conductivity to the cells of a numerical flow model grid within the groundwater modeling code 

MODFLOW-2000 (Anderman and Hill, 2000, 2003). Lateral 

variations in horizontal hydraulic-conductivity,or the material’s capacity to transmit water in the x-y plane parallel to 

bedding, can be assigned through the use of the zonation 

capability of the Hydrogeologic-Unit Flow (HUF) package 

of MODFLOW-2000 (Anderman and Hill, 2000). Zones are 

used to define areas with similar properties within individual 

geologic or hydrogeologic units. For eventual use within a 

numerical hydrologic-flow model, 2-D (map view) models of 

textural data from both oil and water wells were created for 

the geologic units, Qya, Qoa, and the QTm, to define areas 

with similar geologic materials that are likely to have fairly 

uniform hydraulic properties.

Similar to previous studies (Phillips and Belitz, 1991; 

Burow and others, 2004; Faunt, 2009), the primary variable 

used in the textural analysis was sediment grain size, tabulated 

as percentage of coarse-grained texture. Down-hole intervals 

from both oil and water wells were classified as either coarse 

or fine grained. For water wells, coarse-grained deposits 

were those dominated by gravel and sand-size clasts with no 

clay matrix; all other lithology classes were considered finegrained. Even units that had a considerable fraction of large 

clasts were classified as fine-grained if the clasts tended to be 

suspended in a fine-grained matrix. For oil wells, coarse and 

medium texture classes derived from the SP-log curve were 

assigned as coarse grained; fine and very fine classes were 

assigned as fine grained. The binary classification of intervals 

as either coarse or fine grained helped account for the lack of 

an exact correspondence between grain size as described in 

drillers’ lithologic logs and the relative size classes derived 

from SP-log analysis. For use in statistical and geostatistical analysis, the percentage of coarse-grained sediment was 

calculated for the entire thickness of each geologic unit for 

218 wells (table 3). The percentage of coarse-grained sediment was calculated as the total thickness of coarse-grained 

intervals divided by the total thickness of the geologic unit. 

The global mean percentage of coarse-grained texture was 34 

percent, with young alluvium being significantly more coarse 

than older alluvium or the Morales Formation (table 3).

Because the hydrologic-flow model was subdivided on the 

bassis of three geologic units, sediment texture was estimated 

at the nodes of a 2-D grid for each unit. The textural parameter 

represents an average value that applies to the entire thickness 

of the geologic unit. This grid node-based averaging provides 

a measure of spatial variability for the unit in the x,y dimensions, but eliminates any portrayal of textural variability in the 

z direction within the unit. The density of wells in the center 

of the groundwater basin is sufficient to model the texture of 

each geologic unit on a 250-m horizontal grid. Data density 

throughout the study region varied on the basis of the availability of data. This variable sample density did not appear 

to bias the statistics used to describe the x,y,z values. The 

data were not declustered prior to the geostatistical modeling. 

The grid was oriented with the long axis roughly parallel to 

Cuyama Valley axis and has a uniform cell spacing of 250 m 

in the x and y directions consisting of 300 cells in the x-direction and 135 in the y-direction. The textural data at wells 

represented x,y point values for each geologic unit.

Coarse-grained texture was extrapolated away from the 

well data for each geologic unit by using the geostatistical 

Table 3. Summary of logs used for textural analysis by geologic 

unit.

[Qya, Younger alluvium; Qoa, Older alluvium; QTm, Morales formation]

Geologic unit

(abbreviation)

Number 

of records1

Maximum 

thickness

(feet)

Average

thickness

(feet)

Percentage 

coarse

Younger alluvium 

(Qya) 119 193 92 59

Older alluvium 

(Qoa) 154 354 171 36

Morales Formation 

(QTm) 120 1,384 754 31

All 235 1,637 868 34

1

Records for each unit do not sum to the total shown in “All” because wells can penetrate 

more than one unit down hole.
34 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

method of ordinary kriging in a similar fashion to methods 

used by Burow and others (2004) and Faunt and others (2010). 

An advantage of using geostatistics instead of simple spatial 

interpolation methods, such as inverse-distance weighted 

interpolation, is that the geostatistical model is fitted to the 

observed spatial correlation structure, whereas simple interpolation methods are based on an assumed spatial correlation 

structure. Kriging is based on the assumption that the parameter being interpolated varies in a continuous manner from one 

location to the next, such that points that are near each other 

have a certain degree of spatial correlation, but points that are 

widely separated are not spatially correlated (Journel and Huijbregts, 1978; Isaaks and Srivastava, 1989). Anisotropy, or the 

directional component of the spatial dependence, in the spatial 

correlation structure can be obtained by combining several different models aligned along its principal axis to form a nested 

set of models. 

2-D semivariograms that displayed differences in the percentage of coarse-grained sediment between pairs of points at 

different distances were developed in order to investigate the 

spatial correlation of the textural data (table 4). The semivariograms reflected the geometry and depositional environment of 

Cuyama Valley in that they typically have a horizontal range 

in kilometers along the axis of the valley and half that perpendicular to the valley axis (table 4). Typically, the semivariograms displayed a nugget, or variance at very close sample 

spacing, indicating textural variability at scales smaller than 

the distance between neighboring well data. Semivariograms 

were calculated by using a moving window with at least two 

nearest neighbors and an optimum of five nearest neighbors. 

The semivariograms were fitted with curves or variogram 

models that best fit the data. Each model included a nugget 

and used an exponential variogram model; in some cases the 

data were best fit using multiple, or nested, variagram models. Anisotropy that was observed in the semivariograms was 

best fit by setting the major anisotropic axis close to the trend 

of the valley axis, parallel to the main river channel, and the 

minor anisotropic axis perpendicular to this axis, close to the 

trend of the tributaries and fans (table 4).

2-D kriging was used to extrapolate coarse-grained texture 

to each x,y grid node for the entire thickness of the geologic 

unit. To augment the textural parameter for alluvial units Qya 

and Qoa, the digital elevation model was introduced as a second data set, and texture was computed by using co-kriging. 

Textural data for Qya and Qoa exhibited some correlation with 

elevation where these deposits were in channels or on alluvial 

fans. Co-kriging tended to improve the textural interpolation, 

especially in drainages with few or no well data, such that the 

primary texture variable was considerably undersampled. 

The spatial dimensions of the search neighborhood were 

not constrained; therefore, for locations of the estimation grid 

having densely-spaced wells, the effective search neighborhood was relatively small. For locations of the estimation grid 

that contained widely-spaced wells, the effective search neighborhood expanded laterally until at least two texture values 

were reached. Although the estimation neighborhood used at 

least two values for each kriged estimate, most estimates in the 

corners and along the boundaries of the grid were extrapolated 

rather than interpolated values.

As is indicated by the nugget and range of the variograms, 

the assumption that texture at any point in heterogeneous 

alluvial sediments is related to texture at surrounding points 

several kilometers away might not always be valid. Therefore, 

in areas of sparse data, the texture maps are to be regarded 

as only showing general trends and averages. Conversely, in 

areas where nearby data are variable and there is a significant 

relative nugget in the variogram model, the 3-D kriging can 

produce smoothed estimates. This results because the kriging 

algorithm aims to find a least-squares estimate of the expected 

value; therefore, the more data that are included in the estimate, the smoother the estimate will be.

The spatial patterns of the percentage of coarse-grained 

texture are shown in texture maps of the three basin-fill units 

(figs. 22–24). The 2-D kriged estimates of percentage of 

coarse-grained texture showed significant heterogeneity in the 

texture of the sediments that reflects the depositional environment and the geomorphic evolution of the region since the 

Pliocene. The spatial structure of the kriged textural model for 

the young alluvium can be attributed to the alignment of the 

active drainages, whereas the textural models of the older units 

were less correlated to modern topography.

Table 4. Kriging parameters used for textural analysis.

[—, second dataset not used; DEM, digital elevation model; m, meters]

Geologic unit (abbreviation) Method Second 

dataset

Major1

(meters)

Minor2

(meters)

Direction3

(degrees)

Sill,

(percent) Lag Nugget,

(percent)

Younger alluvium (Qya) Co-kriging DEM 19,200 11,500 105 10 12 lags of 

1,600 m

6

Older alluvium (Qoa) Co-kriging DEM 14,400 8,900 107 3.5 12 lags of 

1,200 m

9

Morales Formation (QTm) Kriging — 8,000 2,715 80 4.2 8 lags of 

1,000 m

7

1

 Distance to the sill or correlation length along the major anisotropic axis.

2

 Distance to the sill or correlation length along the minor anisotropic axis.

3

 Direction reported in degrees measured clockwise from north. 
Textural Analysis of Basin-Filling Unit 35

166

166

33

Carrizo 33

Plain San Joaquin Valley

Cuyama

Badlands

Caliente Range

Cuyama River

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

0 5 10 Miles

0 5 10 Kilometers

Sierra

Madre

Mountains

EXPLANATION

Study-area boundary

Shaded relief base created from 30-m digital elevation model from USGS 

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

Albers Projection, NAD83 Well texture data

Percentage coarse Percentage coarse

Calculated texture

Cuyama Valley

groundwater

basin

0 to 10

10.001 to 20

20.001 to 30

30.001 to 40

40.001 to 50

50.001 to 60

60.001 to 70

70.001 to 80

80.001 to 90

90.001 to 100

0 to 10

10.001 to 20

20.001 to 30

30.001 to 40

40.001 to 50

50.001 to 60

60.001 to 70

70.001 to 80

80.001 to 90

90.001 to 100

Figure 22. Kriged result of textural analysis for younger 

alluvium, Qya.

The texture model of Qya had the highest percentage of 

coarse deposits of the three units (fig. 22). The coarse-grained 

nature of the Qya reflects a number of factors, including the 

short distances between the sediment sources in the surrounding uplands and the sites of sediment deposition as well as the 

high-energy nature of Cuyama River and tributary creeks that 

transport sediments during winter storms and summer monsoonal rains. Because the basin is relatively small, the Cuyama 

River is able to carry a large bed load long distances through a 

large percentage of the valley. Coarse-grained sediment input 

also comes from several tributary drainages in the southeastern part of the study area that have relatively large catchment 

areas (fig. 22). 

The texture model for Qoa differs in spatial structure from 

Qya in being overall much finer-grained and generally unrelated to the modern active drainages (fig. 23). Much of Qoa 
36 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

166

166

33

Carrizo 33

Plain San Joaquin Valley

Cuyama

Badlands

Caliente Range

Cuyama River

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

0 5 10 Miles

0 5 10 Kilometers

Sierra

Madre

Mountains

Shaded relief base created from 30-m digital elevation model from USGS 

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

Albers Projection, NAD83

Cuyama Valley

groundwater

basin

EXPLANATION

Well texture data Study-area boundary

Percentage coarse Percentage coarse

Calculated texture

0 to 10

10.001 to 20

20.001 to 30

30.001 to 40

40.001 to 50

50.001 to 60

60.001 to 70

70.001 to 80

80.001 to 90

90.001 to 100

0 to 10

10.001 to 20

20.001 to 30

30.001 to 40

40.001 to 50

50.001 to 60

60.001 to 70

70.001 to 80

80.001 to 90

90.001 to 100

is derived from erosional reworking of uplifted parts of the 

Morales Formation. This reworking of previously-deposited 

sediment could account for the generally fine-grained nature 

of Qoa in the western half of the study area (fig. 23). Many of 

the wells throughout the valley are variable in their percentage of coarse-grained deposits in the Qoa, which could reflect 

the presence of local coarse-grained channels that affects the 

percentage of coarse-grained material when averaged over the 

entire thickness of the unit. A region of consistently coarsegrained material exists in the eastern part of the study area and 

could reflect an older stream channel alignment or the depositional site of sediments shed to the northwest off the uplifting 

Cuyama Badlands (fig. 23).

The QTm is much finer-grained than the overlying units 

(fig. 24). The QTm is particularly fine grained in the western half of Cuyama Valley, where surface geologic mapping 

identifies a lacustrine facies in this unit (Upson and Worts, 

1951; Dibblee and Minch, 2005d; DeLong and others, 2008). 

This region of fine-grained material, and distinct fine-grained 

intervals within the Morales Formation, could reflect a 

Figure 23. Kriged result of textural analysis for older 

alluvium, Qoa.
Textural Analysis of Basin-Filling Unit 37

relatively distant sediment supply and temporary disruption of 

sediment transport in the Cuyama River drainage as a result of 

episodic uplift of the Sierra Madre Mountains at the west end 

of the valley (Dibblee, 1976). There are broad regions of relatively coarse material in the vicinity of the Cuyama Badlands 

(fig. 24). These areas are generally unrelated to the modern 

active drainages and represent deposition of alluvial materials 

prior to the development of modern topography. 

The modeled percentage of coarse-grained sediment for 

each of the three basin-filling units is shown in perspective 

view in figure 25 along the two lines of section from Singer 

and Swarzenski (1970; fig. 17). The percentage of coarsegrained sediment was calculated for the entire thickness of 

each basin-filling unit for 250-m grid cells throughout the 

Cuyama Valley study area. The modeled result is portrayed in 

figure 25 for only those grid nodes that fall along the two lines 

of section. In this view, the kriged textural results are portrayed in grid cells that have fixed x,y dimensions, but variable 

height that is governed by the modeled elevation of the top 

and base of each unit within the geologic framework model 

166

166

33

Carrizo 33

Plain San Joaquin Valley

Cuyama

Badlands

Caliente Range

Cuyama River

119°50’ 119°40’ 119°30’ 119°20’ 119°10’

35°

34°

50’

34°

40’

0 5 10 Miles

0 5 10 Kilometers

Sierra

Madre

Mountains

Shaded relief base created from 30-m digital elevation model from USGS 

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

Albers Projection, NAD83

Cuyama Valley

groundwater

basin

EXPLANATION

Well texture data Study-area boundary

Percentage coarse Percentage coarse

Calculated texture

0 to 10

10.001 to 20

20.001 to 30

30.001 to 40

40.001 to 50

50.001 to 60

60.001 to 70

70.001 to 80

80.001 to 90

90.001 to 100

0 to 10

10.001 to 20

20.001 to 30

30.001 to 40

40.001 to 50

50.001 to 60

60.001 to 70

70.001 to 80

80.001 to 90

90.001 to 100

Figure 24. Kriged result of textural analysis for the 

Morales Formation, QTm.
38 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

(fig. 25). Numerical effects resulting from the sampling of the 

stratigraphic unit tops and the textural models along the lines 

of section cause minor local gaps between grid cells between 

units. The geologic map and the map trace of the section are 

shown at an arbitrary depth below the modeled texture result 

for locational purposes (fig. 25).

Qya has the coarsest modeled grain size of the three basinfilling units; it is the coarsest in the vicinity of the active 

Cuyama River channel. Kriged textural results from Qoa 

are moderately coarse-grained in the eastern half of Cuyama 

Valley, but transition to fine-grained at the western end of 

the valley. Modeled texture results for the QTm portray it as 

being generally fine-grained, particularly at the west end of the 

valley (fig. 25). The south end of section B-B’ shows a slight 

relative increase in the modeled percentage of coarse-grained 

sediment, which could reflect proximity to sediment sources 

along the uplifted southern edge of the basin.

Figure 25. Perspective view showing result of kriged textural models for the younger alluvium, older alluvium, and Morales Formation 

units (Qya, Qoa, and QTm) along two vertical sections.

Cuyama Valley

Cuyama River

Sierra Madre Mountains

A

A'

B'

B

A

A'

B

QTm

Qoa

Qya

QTm Qoa

QTm

Qoa

N

Cells along two lines of

section are attributed with

modeled texture result for

Qya, Qoa, and QTm.

Colors appear variable as

due to the effects of

illumination from the

south and above.

View is from the southeast looking to the northwest from an 

elevation of 60 degrees above the horizon. Horizontal and vertical

scale is variable because of the effects of perspective view.

EXPLANATION

Study-area boundary

Line of section

Generalized geologic units

shown on base map

Qc, active channel

Qya, young alluvium

Qoa, older alluvium

QTm, Morales Formation

BR1, Quatal Formation

BR1, Caliente Formation

BR2, bedrock unit 2

A A'

Percentage coarse

Calculated texture

0 to 10

10.001 to 20

20.001 to 30

30.001 to 40

40.001 to 50

50.001 to 60

60.001 to 70

70.001 to 80

80.001 to 90

90.001 to 100

Shaded relief base created from 30-m digital elevation model from USGS 

National Elevation Dataset (NED); North American Vertical Datum 1983 (NAVD83)

Hydrology sourced from 1:24,000-scale National Hydrography Dataset, 1974–2009

Place names sourced from USGS Geographic Names Information System, 1974–2009

Albers Projection, NAD83
Summary 39

Summary

Water-resource management concerns have prompted an 

evaluation of the hydrogeology and water availability of the 

Cuyama Valley groundwater basin by the U.S. Geological Survey (USGS), in cooperation with the Water Agency Division 

of the Santa Barbara County Department of Public Works. 

The eventual construction and use of a numerical hydrologicflow model of the basin drives the need for (a) a conceptual 

understanding of the geologic setting of the Cuyama Valley 

groundwater basin; (b) the construction of three-dimensional 

digital models of the geologic framework of the basin; and (c) 

an analysis of the spatial variability of lithology and grain size 

to form the geologic basis for estimating the aquifer hydraulic properties. Previous work has outlined the overall shape 

of the basin, located many of the faults, and delineated and 

characterized aquifers in the saturated parts of the younger and 

older alluvium—units that historically have yielded most of 

the water pumped in the study area. This report builds on that 

work by creating three-dimensional digital datasets suitable 

for incorporation within a numerical hydrologic-flow model 

and includes greater detail for the deeper stratigraphic units of 

the groundwater basin, which were not previously investigated 

in detail.

A several hundred meter-thick section of Pliocene continental deposits and Pleistocene alluvial sediments constitutes the 

principal groundwater aquifer of the Cuyama Valley groundwater basin. This section can be subdivided into three principal stratigraphic units: Qya, younger alluvium; Qoa, older 

alluvium; and QTm, the Morales Formation. The two alluvial 

units are distinguished on the basis of degree of cementation and the amount of dissection and deformation. The QTm 

is an alluvial and fluvial deposit characterized by relatively 

fine-grain size, general lack of coarse channel deposits, and 

greater amounts of clay compared to the overlying section. 

Consolidated rocks that lie beneath the Morales Formation are 

generally non-water bearing.

A geologic framework model was constructed to represent 

the subsurface geometry of the stratigraphic units, Qya, Qoa, 

QTm, and a composite pre-QTm bedrock unit, by extracting and combining information from a variety of datasets, 

including existing lithologic and electrical geophysical logs 

from oil and gas wells and water wells, cross sections, and 

geologic maps. The framework model was constructed by 

creating gridded surfaces that represented the altitude of the 

top of each stratigraphic unit from the input data and then 

combining these surfaces within a three-dimensional geologic 

modeling software package. Data from electrical geophysical 

logs throughout the basin were combined with recent geologic mapping of the Cuyama area to consistently identify the 

Morales Formation and place the top of the unit within the 

geologic framework model some 400 to 600 feet deeper than 

previously published interpretations. The older alluvial unit, 

Qoa, was not subdivided from younger alluvium on previously 

published sections. Within the geologic framework model, 

Qoa is a locally thick unit that includes the lower parts of the 

previously defined undivided Qya and Qoa and the upper part 

of the previously defined Morales Formation.

Sediment grain-size data were analyzed in both two and 

three dimensions to help define textural variations in the 

Cuyama Valley groundwater basin and to identify areas with 

similar geologic materials that potentially have fairly uniform hydraulic properties. Sediment grain size was used to 

construct three-dimensional textural models that employed 

simple interpolation between drill holes and to construct twodimensional textural models for each stratigraphic unit that 

incorporated spatial structure of the textural data. The percentage of coarse-grained sediment was calculated from well data 

for the entire thickness of the Qya, Qoa, and QTm units. These 

data were extrapolated away from the well data across the 

study area at 250-meter spacing by using geostatistical methods. The resultant textural models portrayed a coarse-grained 

younger alluvial unit localized along the Cuyama River and 

several tributary drainages and a finer-grained older alluvial 

unit whose textural variations were less tied to the location 

of the modern drainages. The underlying Morales Formation 

displayed a broad west-to-east transition from coarse to finegrained deposits. The spatial distribution and modeled textural 

characteristics of the three basin-filling units are related to the 

Pliocene and Pleistocene tectonic evolution and uplift of the 

basin, the progressive narrowing of the valley, and the gradually increasing channelization of the Cuyama River drainage. 
40 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

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2000–342, 89 p.

Anderman, E.R., and Hill, M.C., 2003, MODFLOW-2000, 

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(HUF) package—Alternative storage for the uppermost 

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modflow2000.html.

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central California: Geological Society of America Bulletin, 

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Appendix 1. 43

Appendix

Appendix 1.

Interpreted depth to top of geologic units in oil 

and gas wells, Cuyama Valley

Data compiled within appendix 1 include well location 

information and subsurface geologic information, such as 

depths to the geologic unit tops, from oil and gas wells in 

the Cuyama Valley and surrounding areas. Well names and 

location data were obtained in a digital well-location database 

from the California Department of Conservation, Division of Oil, Gas and Geothermal Resources (CA DOGGR) 

(ftp://ftp.consrv.ca.gov/pub/oil/GIS/ accessed February 2010). 

Oil and gas exploration holes in the database, and in this 

report, are referenced by American Petroleum Institute (API) 

well number, a unique, permanent, numeric identifier assigned 

to each well drilled for oil and gas in the United States. The 

numbers reported here are abbreviated versions of the full API 

well-number and consist of a three-digit county code followed 

in sequence by a five-digit unique well identification number 

within the county. County codes are as follows: 079, San Luis 

Obispo County; 083, Santa Barbara County; 111, Ventura 

County. Two wells do not have API numbers. The information 

contained in the CA DOGGR database includes API well number; operator; lease name and well number; section, township, 

and range; and latitude and longitude. Wells in appendix 1 are 

identified by API number and a well identifier, which was created by merging the lease name and well number. 

Well locations, in meters, are reported in Albers projected 

coordinate system, North American Datum of 1983 (NAD 83), 

GRS 80 spheroid. Elevation at the well location, in feet, is 

reported relative to mean sea level. Values are reported in feet 

to maintain consistency with source geologic and geophysical 

data for which depths are reported in feet.

All geologic unit tops are reported in appendix 1 as measured depth—the depth as measured along the length of the 

borehole. Geologic unit tops with a depth of zero are exposed 

at land surface and indicate that the well spudded in the listed 

formation. Subsurface geologic units are listed in stratigraphic 

order, with stratigraphically highest units on the left and successively lower units to the right. Data columns for some formation tops are preceded by a “less than” symbol in a separate 

column (LT) that is used to denote cases where the top of the 

formation is above the start of the electric log, such that the 

top of the log only provides a maximum value for the drilled 

depth to the top of the stratigraphic unit. The symbol is listed 

in a separate column to avoid the appearance of non-numeric 

characters within the formation tops data column, facilitating 

use of these data within a geographic information system. 

Data compiled within appendix 1 are presented as an 

EXCEL file that has the following information:

•	 API number.

•	 Well identifier.

•	 Easting, referenced to North American Datum of 1983 

(NAD83).

•	 Northing, referenced to NAD83.

•	 Elevation of land surface at the well location, referenced 

to National Geodedic Vertical Datum of 1988 (NGVD88).

•	 Total depth of the well.

•	 Drilled depth to older alluvium, Qoa.

•	 Drilled depth to the Morales Formation, QTm.

•	 Drilled depth to the Quatal Formation, Tq.

•	 Drilled depth to bedrock units 1 or 2, BR1 or BR2.
44 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California

Appendix 2.

Interpreted depth to top of geologic units in 

water wells, Cuyama Valley

Data compiled within appendix 2 include well location 

information and depths to geologic unit tops for older alluvium, Qoa, and the Morales Formation, QTm from water wells 

in the Cuyama Valley and surrounding areas. Well location 

data were obtained in a digital form from the US Geological 

Survey (USGS) National Water Information System web page 

(NWIS Web, http://waterdata.usgs.gov/nwis/ accessed July 

2012). Wells in appendix 2 are identified by a well identifier 

that take one of the following forms: (1) a well name, such as 

10/25-19P1, from Upson and Worts (1951); (2) a well name, 

such as PT-18 or CUY-40, from Everett and others (2013); 

or (3) a well name, such as CUY-G-05, that is unique to this 

report. Some wells appear in both Upson and Worts (1951) 

and Everett and others and are given identifiers from both 

reports. 

Well locations, in meters, are reported in Albers projected 

coordinate system, North American Datum of 1983 (NAD 83), 

GRS 80 spheroid. Elevation at the well location, in feet, is 

reported relative to mean sea level. Values are reported in feet 

to maintain consistency with source geologic and geophysical 

data for which depths are reported in feet.

All geologic unit tops are reported in appendix 2 as measured depth, the depth as measured along the length of the 

borehole. Geologic unit tops with a depth of zero are exposed 

at land surface and indicate that the well spudded in the listed 

formation. Some wells are interpreted to have bottomed within 

younger alluvium (Qya), such that the total depth of the log 

provides a minimum value for the drilled depth to the top of 

the underlying unit, Qoa. For these wells, interpreted depth 

to the top of Qoa is preceded by a “greater than” symbol in a 

separate column (GT) that is used to denote cases where the 

top of the formation is interpreted to lie below the bottom of 

the well. The symbol is listed in a separate column to avoid 

the appearance of non-numeric characters within the formation tops data column, facilitating use of these data within a 

geographic information system. 

Data compiled within appendix 2 are presented as an 

EXCEL file that has the following information:

•	 Well identifier.

•	 Easting, referenced to North American Datum of 1983 

(NAD83).

•	 Northing, referenced to NAD83.

•	 Elevation of land surface at the well location, referenced 

to National Geodedic Vertical Datum of 1988 (NGVD88).

•	 Total depth of the well.

•	 Drilled depth to older alluvium, Qoa.

•	 Drilled depth to the Morales Formation, QTm.

•	 Source of lithologic data.

References Cited

Everett, R.R., Gibbs, D.R., Hanson, R.T., Sweetkind, D.S., 

Brandt, J.T., Falk, S.E. and Harich, C.R., 2013, Geology,

water-quality, hydrology, and geomechanics of the 

Cuyama Valley groundwater basin, California, 2008–12: 

U.S. Geological Survey Scientific Investigations Report 

2013–5108, 62 p. 
Appendix 4. 45

Appendix 3.

Sediment textural characteristics interpreted 

from electric logs from oil and gas wells, 

Cuyama Valley 

Data compiled within appendix 3 include well location 

information and sediment textural characteristics as interpreted 

from electric logs from oil and gas wells in Cuyama Valley 

and surrounding areas. Well names and location data were 

obtained in a digital well location database from California 

Department of Conservation, Division of Oil, Gas and Geothermal Resources as described in appendix 1.

Interpreted sediment texture for down-hole intervals is 

reported along with a corresponding grain-size class. The geologic unit predicted to be present at each depth was determined 

by vertically intersecting the geologic framework model at the 

location of each well.

The EXCEL file that contains the sediment textural characteristics from oil and gas wells in Cuyama Valley has two 

worksheets. The first worksheet is labeled “Table A3_1 Well 

location” and contains the following information:

•	 American Petroleum Institute (API) well number.

•	 Well identifier, created by merging the lease name and 

well number.

•	 Easting, referenced to North American Datum of 1983 

(NAD83).

•	 Northing, referenced to NAD83.

•	 Elevation of land surface at the well location, referenced 

to National Geodedic Vertical Datum of 1988 (NGVD88).

•	 Total depth of the well.

The second worksheet is labeled “Table A3_2 Texture” and 

contains the following information:

•	 API number.

•	 Interpreted lithology.

•	 Grain-size class.

•	 Top of interval.

•	 Base of interval.

•	 Interval thickness.

•	 Geologic unit from Framework.

Appendix 4.

Sediment textural characteristics interpreted 

from drillers’ lithologic logs from water wells, 

Cuyama Valley 

Data compiled within appendix 4 include well location 

information and sediment textural characteristics as interpreted 

from drillers’ lithologic logs from water wells in Cuyama Valley and surrounding areas. Well names and location data were 

assigned in the fashion described in appendix 2.

The drillers’ lithologic description for down-hole intervals 

is reported along with a corresponding grain-size class and 

sorting parameter. Records for water wells obtained from the 

California Department of Water Resources are confidential. 

For these wells, the drillers’ lithologic descriptions were not 

tabulated; only the grain-size class and sorting parameter interpreted from the descriptions were tabulated. The stratigraphic 

unit predicted to be present at each depth was determined by 

vertically intersecting the geologic framework model at the 

location of each well.

The EXCEL file that contains the sediment textural characteristics from oil and gas wells in Cuyama Valley has two 

worksheets. The first worksheet is labeled “Table A4_1 Well 

location” and contains the following information:

•	 Well identifier.

•	 Easting, referenced to North American Datum of 1983 

(NAD83).

•	 Northing, referenced to NAD83.

•	 Elevation of land surface at the well location, referenced 

to National Geodedic Vertical Datum of 1988 (NGVD88).

•	 Total depth of the well.

•	 Source of lithologic data.

The second worksheet is labeled “Table A4_2 Texture” and 

contains the following information:

•	 Well identifier. 

•	 Top of interval.

•	 Base of interval.

•	 Interval thickness.

•	 Lithologic description.

•	 Grain-size class.

•	 Sorting.

•	 Geologic unit from Framework. 
46 Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California
Prepared by the Sacremento Publishing Service Center.

For more information concerning this report, contact:

Director

U.S. Geological Survey

California Water Science Center

6000 J Street, Placer Hall

Sacramento, CA 95819

dc_ca@usgs.gov

or visit our Web site at:

http://ca.water.usgs.gov
Sweetkind and others—Construction of 3-D Geologic Framework and Textural Models for Cuyama Valley Groundwater Basin, California—SIR 2013-5127