Geologic Unit: Fields Spring

Usage:

Fields Spring member (informal) of Grande Ronde Basalt of Columbia River Basalt Group (WA*)
Fields Spring member (informal) of Grande Ronde Basalt of /Yakima basalt subgroup [informal] of Columbia River Basalt Group (WA*)
Misspelled Field Springs and Fields Springs in some reports.

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:

Named from exposures near [Fields Spring State Park (named after Mr. Fields, an early settler who developed the spring for himself and his neighbors), in secs. 16 and 21, T. 7 N., R. 45 E., Fields Spring 7.5-min quadrangle, Asotin Co.], Grande Ronde Valley, southeastern WA (see Reidel and others, 1989).
Reference localities: (1) Grande Ronde Canyon rim south of Big Butte, in SW/4 SW/4 sec. 1, T. 7 N., R. 44 E., [Fields Spring 7.5-min quadrangle], WA; and (2) Marengo grade, in NE/4 sec. 12, T. 11 N., R. 40 E., Zumwalt 7.5-min quadrangle, [Columbia Co., southeastern WA] (Reidel and others, 1989).

AAPG geologic province:

Eastern Columbia basin*