Usage:
Blue Gulch Mudstone Member of Hornbrook Formation (CA*,OR*)
Subunits:
(alphabetical): Hilt Bed (CA*,OR*), Rancheria Gulch Sandstone Beds (CA*,OR*).
Geologic age:
Late Cretaceous (Campanian to Maastrichtian)
Type section, locality, area and/or origin of name:
Type section (composite): five localities near Blue Gulch, Rancheria Gulch, and Hilt; all in T. 47 N., R. 6 W., Hornbrook 15-min quadrangle, Siskiyou Co., CA: (1) in SE/4 SW/4 sec. 20; (2) in SW/4 SE/4 sec. 21; (3) in NE/4 sec. 33 and NW/4 sec. 34; (4) in SW/4 SE/4 sec. 21; and (5) in NE/4 NE/4 sec. 34 and in SE/4 sec. 27. Named from Blue Gulch, southeast of Klamath River, 4 km south of Hornbrook (Nilsen, 1984).
AAPG geologic province:
Klamath 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 ([ ]).