Geologic Unit: Saddle Mountains

Usage:

Saddle Mountains Basalt of Columbia River Basalt Group (ID*,OR*,WA*)
Saddle Mountains Basalt of /Yakima basalt subgroup [informal] of Columbia River Basalt Group (ID*,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).]

Subunits:

(alphabetical): Asotin Member (ID*,WA*), Buford Member (OR*,WA*), Craigmont Member (ID-local), Elephant Mountain Member (ID*,OR*,WA*), Esquatzel Member (WA*), Grangeville Member (ID-local), Ice Harbor Member (WA*), Icicle Flat Member (ID-local), Lower Monumental Member (ID*,WA*), Pomona Member (ID*,OR*,WA*), Swamp Creek Member (ID-local), Umatilla Member (ID*,OR*,WA*), Weissenfels Ridge Member (ID*,WA*), Wilbur Creek Member (ID*,WA*).

Geologic age:

late Tertiary (middle to late Miocene)*

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

Type locality: scarp on east side of Sentinel Gap between Vantage and Priest Rapids [Beverly quadrangle], southern Grant Co., central southern WA (Mackin, 1961).
Reference localities in WA include (see Swanson and others, 1979):
(1) roadcuts along Highway 17, in and north of Mesa, 40 km north of Pasco in Esquatzel Coulee;
(2) upper part of bluff on west side of Wallula Gap;
(3) roadcuts along Mabton-Bickleton Road;
(4) Devils Canyon;
(5) Cloverland Grade, 6 km west of Asotin; and
(6) railroad cuts, about 2 km northeast of Ice Harbor Dam.

AAPG geologic province:

Eastern Columbia basin*