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National Geologic Map Database

Geologic Unit: Sonoma

Usage:

Sonoma Volcanics (CA*)


Subunits:

St. Helena Rhyolite Member (CA*).


Geologic age:

Pliocene*
Miocene*


Type section, locality, area and/or origin of name:

Named from typical exposures on west flanks of Sonoma Mountains, north of San Francisco Bay region, Sonoma Co., northern CA (Dickerson, 1922).


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 does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).