A Lava Flow without a Source: The Cohassett Flow and Its Compositional Components, Sentinel Bluffs Member, Columbia River Basalt Group

Abstract

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Potential for Natural Gas Storage in Deep Basalt Formations at Canoe Ridge, Washington State: A Hydrogeologic Assessment

“…The Grande Ronde Basalt subdivisions are consistent with regional stratigraphic relationships developed from other deep boreholes in the Columbia Plateau (Reidel et al 1989). The member of Sentinel Bluffs stratigraphy follows the revisions by Reidel (2005). Because of this high-density sampling, a high level of reliability can be assigned to the Grande Ronde Basalt stratigraphy identified at the borehole.…”

“…As a whole, Grande Ronde Basalt flows are difficult to distinguish visually in the field, because of their very similar appearance (Reidel et al 1989;Reidel 2005). Because of this visual similarity and the need to be able to distinguish specific target reservoir and caprock horizons in the subsurface, flows were closely sampled for detailed XRF analysis (Table A.1) to develop a detailed stratigraphy for the 100 Circles #1 borehole.…”

Paleoseismology of a newly discovered scarp in the Yakima fold-and-thrust belt, Kittitas County, Washington

“…The most informative of the two, the Horned Lizard trench (46.959N., 120.347W.) was measured and described in detail using a 0.5-square-meter grid ( fig. 2) The Horned Lizard trench exposed a shallow basalt unit that was previously mapped as one of several flows making up the Grande Ronde Basalt by Schuster (1994); laboratory paleomagnetic analyses of oriented hand samples collected from the trench correlate this basalt unit with the youngest flow of the Grande Ronde Basalt: the informally named Museum flow of the Sentinel Bluffs Member (Reidel, 2005; Ray Wells and Jonathan Hagstrum, U.S. Geological Survey, written. commun., 2011), which is about 15.5 million years old (mega-annum, or Ma) (Swanson and others, 1979;Reidel and others, 1989).…”

A tunnel runs through it — An inside view of the Tualatin Mountains, Oregon

“…A detailed stratigraphy of the Columbia River Basalt Group has been defined on the basis of geologic mapping, geochemistry, and paleomagnetism (Swanson and others, 1979;Beeson and others, 1985;Reidel and others, 1989;Reidel, 2005). Many of these flows entered the northern Willamette Valley, where two formations, the Grande Ronde Basalt and the overlying Wanapum Basalt are recognized.…”

“…The Frenchman Springs Member of the Wanapum Basalt is represented by the basalt of Sand Hollow (Twfs) and the basalt of Ginkgo (Twfg) of Mackin (1961). The Grande Ronde Basalt is represented by three flows of the Sentinel Bluffs Member (Tgsb) of Reidel (2005), which overlies three flows of the Winter Water member (Tgww) of Tolan and others (2009) and Reidel and others (1989). Exposed in boreholes below the tunnel is a flow of the underlying Ortley member (Tgo) of Tolan and others (2009) and Reidel and others (1989).…”