Usage:
basalt of Sillusi (informal) in Umatilla Member of Saddle Mountains Basalt of Columbia River Basalt Group (ID*,OR*,WA*)
basalt of Sillusi (informal) in Umatilla Member of Saddle Mountains Basalt of /Yakima basalt subgroup [informal] of Columbia River Basalt Group (ID*,OR*,WA*)
Also called flows of Sillusi (informal).
Informal. The rank or lithologic term should not be capitalized. [Yakima basalt subgroup considered informal and should not be capitalized. "Subgroup" not recognized as a formal stratigraphic rank term (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). Columbia River Basalt Group adopted by the ID, OR, and WA Geol. Surveys, and the USGS (rules suspended).]
Geologic age:
late Tertiary (middle Miocene)*
Type section, locality, area and/or origin of name:
Notable exposures [along Columbia River] on south face of Sillusi Butte near McNary Dam, [in sec. 4, T. 5 N., R. 28 E., Umatilla 7.5-min quadrangle, Benton Co., southern WA] (Laval, 1966).
AAPG geologic province:
Eastern Columbia basin*
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 ([ ]).