Location and Age of Foraminifer Samples 

Examined by Chevron Petroleum Company 

Paleontologists from More Than 2,500 Oil Test 

Wells in California

By Earl E. Brabb

Open-File Report 2011–1262

U.S. Department of the Interior 

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

KEN SALAZAR, Secretary 

U.S. Geological Survey 

Marsha K. McNutt, Director 

U.S. Geological Survey, Reston, Virginia: 2011

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For more information concerning this publication, contact: 

Earl E. Brabb, USGS Western Geology and Geophysics Team, 

345 Middlefield Road, Mail Stop 975, Menlo Park, CA 94025 

916-315-8811, ebrabb@usgs.gov. 

Suggested citation: 

Brabb, E.E., 2011, Location and age of foraminifer samples examined by Chevron 

Petroleum Company paleontologists from more than 2,500 oil test wells in 

California: U.S. Geological Survey Open-File Report, 2011-1262, 4 p. and data files, 

available at http://pubs.usgs.gov/of/2011/1262/. 

Any use of trade, product, or firm names is for descriptive purposes only and does 

not imply endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the 

individual copyright owners to reproduce any copyrighted material contained within 

this report

Cover: An example of one of the hand-annotated logs (1-A-1) 
iii

Contents

Introduction and Background............................................................................................................. 1

Information Provided.......................................................................................................................... 1

Ages of Foraminifers.......................................................................................................................... 2

Acknowledgments.............................................................................................................................. 3

References Cited ............................................................................................................................... 3

Data Sets

 1. Scanned images for each of the 2,516 paleologs

.................. http://pubs.usgs.gov/of/2011/1262/of2011-1262_data_set1_filecabinets/

 2. Spreadsheet database with information about each well

.........................http://pubs.usgs.gov/of/2011/1262/of2011-1262_data_set2_database/

Readme file..................................http://pubs.usgs.gov/of/2011/1262/of2011-1262_readme.txt

 Data Set 1. Scanned images for each of the 2,516 paleologs

 Data Set 2. Spreadsheet database with information about each well

Figure

1. Map of California showing the approximate location of the 407 U.S. Geological Survey 7.5-

minute quadrangles with the 2,516 well logs in this report. .......................................................... 4
Introduction and Background

Chevron Petroleum Company in 2001 donated an estimated 50,000 foraminifer slides, 

5,000 well logs, geologic and surface locality maps, and paleontologic reports to the 

California Academy of Sciences and Stanford University for safekeeping, because they 

stopped or cut back exploration for petroleum deposits in California. The material was 

loaned to Earl Brabb temporarily so that information useful to the U.S. Geological 

Survey could be extracted. Among the estimated 5,000 well logs, more than 2,500 were 

printed on fragile Ozalid paper that had deteriorated by turning brown and hardening so 

that they could be easily damaged. These 2,516 well logs were scanned to provide a 

digital copy of the information (data set 1, posted separately at 

http://pubs.usgs.gov/of/2011/1262/of2011-1262_data_set1_filecabinets/).

The 2,516 wells extend over an area from Eureka in Humboldt County south to the 

Imperial Valley and from the Pacific Ocean east to the eastern side of the Great Valley 

and the Los Angeles Basin (fig. 1). The wells are located in 410 7.5-minute quadrangle 

maps in 42 counties. The digital information herein preserves the data, makes the logs 

easily distributed to others interested in subsurface geology, and makes previously 

proprietary information widely available to the public for the first time. 

Information Provided

The information in the accompanying spreadsheet database for nearly all of the wells was 

taken, in part, from one of the six California Division of Oil, Gas and Geothermal 

Resources (DOGGR, formerly called the Division of Oil and Gas) District databases. 

District 6 is divided into two parts (6a and 6b) so that the total number of Districts in this 

report is regarded as seven. The rest of the information came from the original well logs. 

Identification data for the wells is somewhat complicated. Many of the Chevron well logs 

did not have the American Petroleum Institute (API) number, which hardly ever changes 

and is the most useful parameter in searching DOGGR databases. A search of other 

information on the well log was needed. Both the operator and lease names change over 

time as the well is sold or transferred to another owner, so these names in the DOGGR 

database may not even faintly resemble the original name on the well log. Similarly, the 

well number may change as wells are transferred or sold. The latitude and longitude are 

not consistently provided in most of the seven DOGGR databases, nor are the total 

depths. Finding a particular well in the DOGGR database, therefore, requires persistence 

and some luck in tracking down several factors related to the well description. Some 

errors in the spreadsheet database are likely.

All of the 2,516 wells in the spreadsheet database included with this report are 

accompanied by a scanned image of the original well record. This image can be located 

using a code in column A that indicates where the image is stored. The scanned images 

are divided into 10 parts or boxes (1, 2, 3, 4, 5, 6, 7, 19, 20, and 21). Each box is divided 

into at least 2 drawers (A through E for some boxes) that correspond to the file cabinet 

drawers where the hard copies of the wells were originally stored. The drawers may be 

further divided into parts or folders if the number of images in a drawer is large. An 

image with a code of 1A17, for example, is stored in box 1, drawer A, within a folder 
2

with numbers 1 to 69, image 17. An image with a code of 19A23 is stored in Box 19, 

drawer A, folder 1 to 48, item 23. The search process is started by clicking on the box 

number that corresponds to the first number of the code in the spreadsheet database and 

then successively on the drawer letter (A, B, C D, or E), on the folder with the range of 

numbers that includes the image number wanted, and then on the specific image wanted. 

The spreadsheet database (data set 2) is posted separately at 

http://pubs.usgs.gov/of/2011/1262/of2011-1262_data_set2_database/ in several file 

formats.

This spreadsheet database provides information about well locations (columns E, F, G, H 

J, K and L), total depth of the well (column R), date when the Chevron paleontologist 

completed the age analysis (column M), name of the operator who drilled the well

(column B), name of the land-owner or lease-holder (column C), lithology age, and depth 

of various geologic units in the well (column Q), the American Petroleum Institute (API) 

file number (column I), and the number of the DOGGR District digital file (column O). 

District 4 is divided into part 1 and part 2 because the files are so large.

Logs showing the distribution of heavy minerals, electrical logs with no paleontologic 

information, reports about the petrography of sandstones, and reports by paleontologists 

about fossils in the well are not provided here but are in many of the well files. These can 

be accessed at the Branner Library, Stanford University. Other companies drilled many of 

these wells but their slides with foraminifers were examined and dated by Chevron 

paleontologists. Most of the wells were drilled in the 1950s and 1960s but some of the

wells were drilled in the 1930s and 1940s and some as late as the 1980s. 

Ages of Foraminifers

Foraminifers were the principal fossil group used to date the rocks in the 1950’s and 

1960’s when most of the wells were drilled. The zones defined by Goudkoff (1945) were 

used for the Cretaceous and those by Kleinpell (1938) and Laiming (1940) for the 

Tertiary. Cretaceous zones were extended and modified by Berry (1974) who used these 

new definitions to revise the ages for many of the wells.

Correlation of Tertiary foraminifers has changed substantially in the last 50 years. Poore 

(1980) pointed out that many of the zones and stages are time-transgressive when 

compared with zonations of calcareous plankton used in international standards. 

Kleinpell (1980) provided a new correlation of California stages that extensively 

modifies his 1936 correlations. His new classification was used to change Zemorrian ages 

from the early Miocene used by Chevron paleontologists to Oligocene. McDougall 

(2007) has restudied the type sections used by Laiming (1940) and refined the taxonomy 

of the foraminifers to establish better correlations between the California benthic stages 

and zones and the standards for nannoplankton and planktic foraminifers. Her scheme for 

correlating Paleogene foraminifers is substantially different from that of Kleinpell (1980)

and is used in this report to change some of the Chevron ages. Some information from the 

report by Almgren and others (1988) was also used. These changes are only a temporary 

and arbitrary age assignment until the Chevron faunas are restudied. The scanned images 
3

of each well can always be checked to determine what age was originally used by 

Chevron paleontologists.

Acknowledgments

I am most grateful to the paleontologists, geologists, and managers with Chevron 

Petroleum Company who provided the materials for this report. I am also greatly 

indebted to Carl Wentworth and Joel Robinson who worked with the well database in 

GIS format to determine if the quadrangle names were correct. Carl also kindly pointed 

out a reference for the Sun Lepori well near Point Arena. Lew Rosenberg was helpful in 

providing simplified copies of digital well data from the seven DOGGR Districts. 

Century Graphics in North Highlands and El Dorado Hills scanned the well logs, some of 

them exceeding 10 ft in length, and provided the images used in this report.

References Cited

Almgren, A.A., Filewicz, M.V., and Heitman, H.L., 1988, Lower Tertiary foraminiferal 

and calcareous nannoplankton zonation of California; an overview and 

recommendation, in Filewicz, M.V., and Squires, R.L., eds., Paleogene 

stratigraphy, West Coast of North America: Pacific Section, S.E.P.M., West Coast 

Paleogene Symposium, v. 58, p. 83–105.

Berry, K.D., 1974, Mesozoic foraminiferal zonation, Turonian to Tithonian Stages, 

Pacific Coast Province: Pacific Coast S.E.P.M. Annual Meeting, San Diego, 

p. 1–29.

Goudkoff, O.S., 1945, Stratigraphic relations of the Upper Cretaceous in the Great Valley 

of California: American Association of Petroleum Geologists Bulletin v. 29, 

p. 956–1007.

Kleinpell, R.M., 1938, Miocene stratigraphy of California: Tulsa, OK, American 

Association of Petroleum Geologists, 450 p.

Kleinpell, R.M., 1980, The Miocene stratigraphy of California revisited: Tulsa, OK, 

American Association of Petroleum Geologists, Studies in Geology 11, p. 1–182.

Laiming, Boris, 1940, Foraminiferal correlations in Eocene of San Joaquin Valley, 

California: American Association of Petroleum Geologists Bulletin v. 24, 

p. 1923–1939.

McDougall, Kristin, 2007, California Cenozoic biostratigraphy—Paleogene, in Hosford 

Scheirer, A., ed., Petroleum systems and geologic assessment of oil and gas in the

San Joaquin Basin province: U.S. Geological Survey Professional Paper 1713, 

Chapter 4, p. 1–56, available at http://pubs.usgs.gov/pp/pp1713/.

Poore, R.Z., 1980, Age and correlation of California Paleogene benthic foraminiferal 

stages: U.S. Geological Survey Professional Paper 1162–C.
4

Figure 1. Map of California showing the approximate location of the 410 U.S. 

Geological Survey 7.5-minute quadrangles that contain the 2,516 well logs in this 

report.