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The Columbia River flood basalt province: Stratigraphy, areal extent, volume, and physical volcanology

By
Stephen P. Reidel
Stephen P. Reidel
School of the Environment, Washington State University–Tri-Cities, 2710 Crimson Way, Richland, Washington 99354, USA
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Victor E. Camp
Victor E. Camp
Department of Geological Sciences, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA
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Terry L. Tolan
Terry L. Tolan
Department of Geology, Portland State University, Portland, Oregon 97201, USA
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Barton S. Martin
Barton S. Martin
Department of Geology and Geography, Ohio Wesleyan University, 61 South Sandusky Street, Delaware, Ohio 43015, USA
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Published:
August 01, 2013

The middle Miocene Columbia River Basalt Group is the youngest and smallest continental flood basalt province on Earth, covering over 210,000 km2 of mainly Oregon, Washington, and Idaho, with an estimated basalt volume of ~210,000 km3. A well-established regional stratigraphic framework built upon six formations contains numerous flows and groups of flows that can be readily distinguished by their physical and compositional characteristics, thus producing mappable units, the areal extent and volume of which can be calculated and correlated with their respective feeder dikes. The distinct physical features that help to define these units originated during their emplacement and solidification, as the result of variations in cooling rates, degassing, thermal contraction, and interaction with their paleoenvironment. Columbia River Basalt Group flows can be subdivided into two basic flow geometries. Sheet flows dominate the basalt pile, but the earliest flows comprising the Steens Basalt and some of the Saddle Mountains Basalt flows are compound flows with elongated bodies composed of numerous, local, discontinuous, and relatively thin lobes of basalt lava. The internal physical characteristics of the voluminous sheet flows are recognizable throughout their extent, thus allowing mechanistic models to be developed for their emplacement. The emplacement and distribution of individual Columbia River Basalt Group flows resulted from the interplay among the regional structure, contemporaneous deformation, eruption rate, preexisting topography, and the development of paleodrainage systems. These processes and their associated erosional and structural features also influenced the nature of late Neogene sedimentation during and after the Columbia River Basalt Group eruptions. In this paper, we describe and revise the stratigraphic framework of the province, provide current estimates on the areal extent and volume of the flows, and summarize their physical features and compositional characteristics.

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GSA Special Papers

The Columbia River Flood Basalt Province

Stephen P. Reidel
Stephen P. Reidel
School of the Environment, Washington State University-Tri-Cities, 2710 Crimson Way, Richland, Washington 99354, USA
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Victor E. Camp
Victor E. Camp
Department of Geological Sciences, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA
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Martin E. Ross
Martin E. Ross
Department of Marine and Environmental Sciences, Northeastern University, Boston, Massachusetts 02115, USA
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John A. Wolff
John A. Wolff
School of the Environment, Washington State University, Pullman, Washington 99164, USA
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Barton S. Martin
Barton S. Martin
Department of Geology and Geography, Ohio Wesleyan University, 61 South Sandusky Street, Delaware, Ohio 43015, USA
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Terry L. Tolan
Terry L. Tolan
Department of Geology, Portland State University, Portland, Oregon 97201, USA
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Ray E. Wells
Ray E. Wells
U.S. Geological Survey, 345 Middlefield Road, MS 973, Menlo Park, California 94025, USA
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Geological Society of America
Volume
497
ISBN print:
9780813724973
Publication date:
August 01, 2013

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