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Geologic Unit: Gualala

Gualala Formation (CA)

Cretaceous, Late
Geologic Province:
California Coast Ranges province
Areal Extent:

Type Locality:
Not stated. Occurs in Point Arena-Fort Ross region in Mendocino and Sonoma Cos., northwestern CA. Named from town of Gualala at mouth of Gualala River, Mendocino Co., CA (Weaver, 1941). [From US geologic names lexicon, USGS Bull. 1200]

(alphabetical) --all in CA: Anchor Bay Member, Stewarts Point Member.

Unit Name History:
Called Wallala beds (G.F. Becker, 1885, USGS Bull. 19, p. 7-17); Wallala group (C.A. White, 1885, USGS Bull. 22, p. 8) [not synopsized].
Named Gualala series (Weaver, 1941).
Age modified (Weaver, 1943; 1944; Durham and Kirk, 1950).
Revised to Gualala Group (Weaver, 1944).
Revised to Gualala Formation, divided into (ascending) Stewarts Point and Anchor Bay members (Wentworth, 1967).
Mapped (Wagner and Bortugno, 1982).
Overview (Ross and others, 1973).
[When referring to the Gualala series of Weaver (1941), please use informally. The practice of employing "series" for lithostratigraphic or lithodemic nomenclature is now regarded as improper (see ACSN, 1961, 1970; NACSN, 1983). The term "Series" is applied formally only to chronostratigraphic units.]

Note: If you need more information, please contact Nancy Stamm (
Asterisks (*) indicate usage by the U.S. Geological Survey. Other usages by state geological surveys.

"No current usage" implies that a name has been abandoned or that it has fallen into disuse. Former usage and, if known, replacement name given in parentheses ().

Slashes (/) indicate unit name usage violates the 1983 North American Stratigraphic Code. This violation may be explained within brackets ([ ]).

U.S. Department of the Interior, U.S. Geological Survey, Reston, VA, USA
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Last modified: 15-Jan-2013