Named as uppermost unit of Martinez group, south of Simi Valley, Ventura Co, CA. Martinez marine member occurs on both sides of main fault. Consists of medium- to fine-grained sandstones with occasional beds of coarse-grained sandstone in lower portion and about 200 feet of light gray shale in upper part. Contains concretions in places. Is from 800 to 2400 feet thick. Grades laterally and vertically into underlying Las Virgenes sandstone and Simi conglomerate (both new) of Martinez group. Underlies Santa Susana shale (new). Is early Eocene age based on marine fossils (extensive list, descriptions and localities included).
Source: GNU records (USGS DDS-6; Menlo GNULEX).
Detailed mapping by Zinsmeister (1974) of "Martinez marine member" of Nelson (1925) has shown member is composed of three distinct tongues of fine-grained sandstone interbedded with medium- to light-gray siltstones; tongues thin gradually to east, being replaced by siltstones of Santa Susana Formation. Gradational contacts and thinning of tongues indicate "Martinez marine member" represents shallow-water nearshore facies of Santa Susana Formation and does not merit formational rank. Lower sandy facies of Santa Susana Formation in Simi Hills is late Paleocene (Thanetian) age.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).