Geologic Unit: Priest Rapids

Usage:

Priest Rapids Member of Wanapum Basalt of Columbia River Basalt Group (ID*,OR*,WA*)
Priest Rapids Member of Wanapum Basalt of /Yakima basalt subgroup [informal] of Columbia River Basalt Group (ID*,OR*,WA*)
(†Priest Rapids Member of Wanapum Basalt not used by the OR Geol. Survey.)

[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).]

Subunits:

Mabton interbed (WA).

Geologic age:

late Tertiary (middle Miocene)*

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

Named from 4 flows at Priest Rapids Dam, exposed in south-dipping anticline on west side of reservoir [Priest Rapids Lake], Columbia River, [Priest Rapids 7.5-min quadrangle, Yakima Co.], south-central WA (GNU records, USGS DDS-6; Menlo GNULEX).
Principal reference section (subsurface): cores from two holes PRE-1 and PRE-3 [exact location?] below the Priest Rapids Dam (Swanson and others, 1979).
Reference localites in eastern part of plateau (Swanson and others, 1979):
(1) roadcut along Pasco-Kahlotus Highway at head of Devils Canyon, WA;
(2) Whitlow quarry along Pullman-Moscow Highway, in SE/4 SW/4 sec. 4, T. 14 N., R. 45 E., Pullman quadrangle;
(3) roadcut 1.5 km southwest of Malden, WA;
(4) outcrop about 3 km south of Cavendish, ID, along highway to Ahsahka, in NE/4 SW/4 sec. 22, T. 37 N., R. 1 W., Ahsahka quadrangle; and
(5) roadcuts along Highway 95A above 741 m elevation (2,430 ft), 8 to 13 km southeast of St. Maries. ID, in secs. 6 through 8, and 18, T. 45 N., R. 1 W., St. Maries, St. Joe, and Emida quadrangles.
Reference localites in western part of plateau (Swanson and others, 1979):
(1) southeast side of Sentinel Gap, 15 km north of type locality;
(2) south end of Union Gap, WA, along Thorpe Road;
(3) roadcuts along U.S. Interstate Highway I-80 just west of Arlington, OR; and
(4) roadcuts along Highway 14 about 7 km east of Bingen, WA.

AAPG geologic province:

Eastern Columbia basin*
Idaho Mountains province*