The Miocene Topanga Group of Southern California — A 100-Year History of Changes in Stratigraphic Nomenclature

Open-File Report 2007-1385
By: , and 

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Abstract

A review of selected literature summarizes the origin and chronology of changes in usage of 'Topanga' in the Miocene stratigraphic nomenclature of the Los Angeles Basin and adjacent areas in southern California. The review was done to summarize and reconcile some differences in Miocene stratigraphic nomenclature as applied to geologic map compilations of the Santa Ana (Morton, 2004), San Bernardino (Morton and Miller, 2003), Long Beach (Saucedo and others, 2003) and Los Angeles (Yerkes and Campbell, 2005) 30' x 60' quadrangles, all of which are products of the cooperative (California Geological Survey-U.S. Geological Survey) Southern California Areal Mapping Project (SCAMP). The deposition of the Topanga Group spans about 6 my (from as old as about 18 ma to as young as about 12 ma), and the sequence of included strata records changes in provenance and depositional environments that are contemporaneous with part of a major Miocene tectonic episode in southern California -- the 'basin-inception phase' in the evolution of the Neogene Los Angeles basin (Yerkes and others, 1965). The area of Topanga deposition extends to the southern, eastern, northern, and northwestern sides of the Los Angeles basin, as well as the southern part of the eastern Ventura Basin. Topanga beds are inferred to underlie the thick upper Miocene and Pliocene deposits of the central Los Angeles Basin and the southern part of the eastern Ventura Basin; however, they have been reached by drilling only in marginal areas, where the overlying deposits are relatively thin. Post-Topanga strata were deposited in more-restricted areas of rapid subsidence. Selected papers are summarized as they relate to the Topanga nomenclature, and are presented in chronological order.

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Publication type Report
Publication Subtype USGS Numbered Series
Title The Miocene Topanga group of southern California — A 100-year history of changes in stratigraphic nomenclature
Series title Open-File Report
Series number 2007-1385
DOI 10.3133/ofr20071385
Edition Version 1.1, Revised Nov 30, 2009
Year Published 2007
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Western Earth Surface Processes
Description iii, 36 p.
Country United States
State California
Other Geospatial Los Angeles Basin
Online Only (Y/N) Y
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