Usage:
Contra Costa Group (CA*)
Subunits:
(alphabetical) --all in CA: Bald Peak Basalt* or Bald Peak Formation*, Moraga Formation* or Moraga Tuff*, Mulholland Formation, Orinda Formation*, Siesta Formation*.
Geologic age:
late Tertiary (Miocene)
Type section, locality, area and/or origin of name:
Type locality not stated (US geologic names lexicon, USGS Bull. 1200).
[Constituent formations occur in Contra Costa Co., San Francisco Bay region, western CA.]
AAPG geologic province:
Sacramento basin*
Santa Cruz basin*
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 ([ ]).