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National Geologic Map Database
Geologic Unit: Umtanum
Map showing publication footprint
  • Usage in publication:
    • Umtanum unit
  • Modifications:
    • [Informally named]
  • AAPG geologic province:
    • Eastern Columbia basin
Publication:

Reidel, S.P., Tolan, T.L., Hooper, P.R., Beeson, M.H., Fecht, K.R., Bentley, R.D., and Anderson, J.L., 1989, The Grande Ronde Basalt, Columbia River Basalt Group; Stratigraphic description and correlations in Washington, Oregon, and Idaho, IN Reidel, S.P., and Hooper, P.R., eds., Volcanism and tectonism in the Columbia River flood-basalt province: Geological Society of America Special Paper, 239, p. 21-54.


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.


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