Usage:
Alum Rock Rhyolite (CA-recognized locally in type area)
Geologic age:
Tertiary
Type section, locality, area and/or origin of name:
Type area: San Jose-Mount Hamilton area in Coast Ranges about 50 mi southeast of San Francisco. Mapped area is on west slope of Diablo Range. Rhyolite is intrusive body about 1000 feet wide and 400 feet long which crops out in lower Alum Rock Canyon, [Calaveras Reservoir 7.5-min quadrangle, Santa Clara Co., western CA] (Crittenden, 1951).
AAPG geologic province:
Northern Coast Range province
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 ([ ]).