Usage:
Pomona Member of Saddle Mountains Basalt of Columbia River Basalt Group (ID*,OR*,WA*)
Pomona Member of 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).]
Geologic age:
late Tertiary (middle Miocene)*
Type section, locality, area and/or origin of name:
Type locality: roadcuts along Canyon Road (old Highway 97) [Route 821] and a nearby quarry, in NE/4 sec. 17, T. 14 N., R. 19 E., near town of Pomona, Pomona 7.5-min quadrangle, Yakima Co., south-central WA [approx. Lat. 46 deg. 42 min. 20 sec. N., Long. 120 deg. 28 min. 15 sec. W.] (Swanson and others, 1979).
Reference sections, all in south-central WA (Swanson and others, 1979):
(1) roadcuts along Highway 17, 1 km north of Mesa [approx. Lat. 46 deg. 35 min. 15 sec. N., Long. 119 deg. 00 min. 15 sec. W., Mesa West 7.5-min quadrangle, Franklin Co.];
(2) railroad cuts and natural exposures 3 to 6 km upstream from Ice Harbor Dam on north side of Snake River, from center sec. 18 upriver to W/2 sec. 4, T. 9 N., R. 32 E., Levey SE [Levey] 7.5-min quadrangle [from approx. Lat. 46 deg. 15 min. 40 sec. N., Long. 118 deg. 51 min. 30 sec. W. to Lat. 46 deg. 17 min. 30 sec. N., Long. 118 deg. 49 min. 15 sec. W., Franklin Co.];
(3) roadcut and roadside quarry along Hastings Hill Road, in NE/4 NE/4 sec. 3, T. 13 N., R. 40 E., Hay [Central Ferry] 7.5-min quadrangle [approx. Lat. 46 deg. 38 min. 45 sec. N., Long. 117 deg. 46 min. 03 sec. W., Garfield Co.]; and
(4) in quarry just east of Silcott, in SW/4 sec. 21, T. 11 N., R. 45 E., Silcott [Silcott Island] 7.5-min quadrangle [approx. Lat. 46 deg. 25 min. 00 sec. N., Long. 117 deg. 10 min. 55 sec. W., Asotin Co.].
Named from town of Pomona on Yakima River, north of Yakima, WA (Schmincke, 1965a,b).
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 ([ ]).