Location and age of foraminifer samples collected by Chevron Petroleum geologists in California

Open-File Report 2003-167
By:  and 



Most of the geologic maps published for parts of central California in the past century have been made without the benefit of ages from microfossils. The ages of Jurassic, Cretaceous and Tertiary rocks in the mostly poorly exposed and structurally complex sedimentary rocks represented in the Coast Ranges are critical in determining stratigraphic succession or lack of it, and in determining whether the juxtaposition of similar appearing but different age formations means that a fault is present. Since the 1940's, at least, oil company geologists have used microfossils to assist them in geologic mapping and in determining the environments of deposition of the sedimentary rocks containing them. This information had been so confidential that even the names of species were coded by some paleontologists to prevent disclosure. In the past 20 years, however, the attitude of petroleum companies about this information has changed, and many of the formerly confidential materials and reports are now available. We report here on an estimated 50,000 Chevron foraminifer samples from surface localities in more than 600 U.S. Geological Survey 7.5' quadrangles in California. Ages are provided for more than 27,000 of these samples which have been donated by Chevron, along with locality maps, paleontology reports, and other data, to the California Academy of Sciences. To our knowledge, this collection is the largest ever released to the public by a petroleum company for the West Coast. The information from the slides can be used to update geologic maps prepared without the benefit of microfossils, to study foraminifers of Jurassic, Cretaceous and Tertiary age collected from a variety of geologic environments, to analyze the depth and temperature of ocean water covering parts of California during these periods, and for solving nomenclature and other scientific problems.

Publication type Report
Publication Subtype USGS Numbered Series
Title Location and age of foraminifer samples collected by Chevron Petroleum geologists in California
Series title Open-File Report
Series number 2003-167
DOI 10.3133/ofr03167
Edition Version 2.0; Revised April 15, 2005 (originally published 2003)
Year Published 2003
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 13 p.
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