Usage:
Lower Monumental Member of Saddle Mountains Basalt of Columbia River Basalt Group (ID*,WA*)
Lower Monumental Member of Saddle Mountains Basalt of /Yakima basalt subgroup [informal] of Columbia River Basalt Group (ID*,WA*)
[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 (late Miocene)*
Type section, locality, area and/or origin of name:
Type locality: prominent roadcut 1 km south of Lower Monumental Dam, Snake River, in NW/4 SE/4 sec. 3, T. 12 N., R. 34 E., Lower Monumental Dam quadrangle, Walla Walla Co., southeast WA (Swanson and others, 1979).
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 ([ ]).