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Author Reidel, S. P.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword GEOSCIENCES ♦ ROCKS ♦ SOLIDIFICATION ♦ CHEMICAL ANALYSIS ♦ GEOCHEMISTRY ♦ BASALT ♦ LAVA ♦ VOLCANISM ♦ FLUID FLOW ♦ ERUPTION ♦ STRATIGRAPHY ♦ CHEMICAL COMPOSITION
Abstract Evidence is examined for the emplacement of the Umatilla, Wilbur Creek, and the Asotin Members of Columbia River Basalt Group. These flows erupted in the eastern part of the Columbia Plateau during the waning phases of volcanism. The Umatilla Member consists of two flows in the Lewiston basin area and southwestern Columbia Plateau. These flows mixed to form one flow in the central Columbia Plateau. The composition of the younger flow is preserved in the center and the composition of the older flow is at the top and bottom. There is a complete gradation between the two. Flows of the Wilbur Creek and Asotin Members erupted individually in the eastern Columbia Plateau and also mixed together in the central Columbia Plateau. Comparison of the emplacement patterns to intraflow structures and textures of the flows suggests that very little time elapsed between eruptions. In addition, the amount of crust that formed on the earlier flows prior to mixing also suggests rapid emplacement. Calculations of volumetric flow rates through constrictions in channels suggest emplacement times of weeks to months under fast laminar flow for all three members. A new model for the emplacement of Columbia River Basalt Group flows is proposed that suggests rapid eruption and emplacement for the main part of the flow and slower emplacement along the margins as the of the flow margin expands.
ISSN 01480227
Educational Use Research
Learning Resource Type Article
Publisher Date 1998-11-01
Publisher Place United States
Journal Journal of Geophysical Research
Volume Number 103
Issue Number B11


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