- Usage in publication:
-
- Umtanum unit
- Modifications:
-
- [Informally named]
- AAPG geologic province:
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- Eastern Columbia basin
Summary:
Pg. 23 (fig. 1), 39 (table 2), 43-44. Umtanum unit (informal) in Grande Ronde Basalt of Columbia River Basalt Group. Consists of 2 flows (4 flow lobes); typically aphyric, has distinctive entablature/colonnade jointing. Has normal magnetic polarity (in N2 magnetostratigraphic unit). Confined to southern part of Columbia Plateau. Lies above Ortley unit (informal) and below Field Springs [Fields Spring] unit (informal); both in Grande Ronde Basalt. Age is middle Miocene.
Reference localities: Umtanum Ridge above Priest Rapids dam, in sec. 12, T. 13 N., R. 23 E., [Priest Rapids 15-min quadrangle, Yakima Co., central southern WA]; and (2) Saddle Mountains, in sec. 2, T. 15 N., R. 23 E., [Beverly 15-min quadrangle, Grant Co., central southern WA].
[Additional locality information from USGS historical topographic map collection TopoView; accessed September 15, 2013.]
Source: Publication.
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
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