Usage:
Twin River Group (WA*)
Subunits:
(ascending) --all in WA*: Hoko River Formation, Makah Formation, Pyscht Formation.
Geologic age:
Tertiary
Eocene, late* to Miocene, early*
Type section, locality, area and/or origin of name:
Type section: at Deep Creek from point, 3600 ft S. 41 deg. W. from U.S. Forest Service road bridge across Deep Creek, northward to point on axis of east-trending syncline, 700 ft east, 5350 ft north of SW/4 sec. 20, T. 31 N., R. 10 W., Clallam Co., WA (Brown and Gower, 1958).
AAPG geologic province:
Olympic Mountains 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 ([ ]).