Geologic Unit: Roza

Usage:

Roza Member of Wanapum Basalt of Columbia River Basalt Group (OR*,WA*)
Roza Member of Wanapum Basalt of /Yakima basalt subgroup [informal] of Columbia River Basalt Group (OR*,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 (middle Miocene)*

Type section, locality, area and/or origin of name:

Type locality: scarp on east side of Yakima River opposite Roza Station [in sec. 16, T. 15 N., R. 19 E., Badger Pocket 15-min quadrangle], Kittitas Co., south-central WA (Mackin, 1961).
Principal reference section: about 460 m elevation, in SE/4 sec. 16, T. 15 N., R. 19 E., Wymer 7.5-min quadrangle, south-central WA (Swanson and others, 1979).
Reference localities (see Swanson and others, 1979):
(1) head of Frenchman Springs Coulee [Frenchman Coulee] (Mackin, 1961, pls. 5B and 6);
(2) head of Devils Canyon (Bingham and Walters, 1965, Swanson and Wright, 1976b);
(3) head of Horton Grade, in sec. 11, T. 14 N., R. 40 E., near Penawawa;
(4) north part of Colfax, along Highway 195;
(5) Highway 12 at Alpowa Summit, 15 km southeast of Pomeroy;
(6) Anatone Butte along the vent system (Swanson and others, 1975, table 1, No. 17); and
(7) the lower Grand Coulee area, in which Lefebvre (1970) conducted a detailed investigation of the Roza.

AAPG geologic province:

Eastern Columbia basin*