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GEOREF RECORD

The Grande Ronde Basalt, Columbia River Basalt Group

Stephen P. Reidel and Terry L. Tolan
The Grande Ronde Basalt, Columbia River Basalt Group (in The Columbia River flood basalt province, Stephen P. Reidel (editor), Victor E. Camp (editor), Martin E. Ross (editor), John A. Wolff (editor), Barton S. Martin (editor), Terry L. Tolan (editor) and Ray E. Wells (editor))
Special Paper - Geological Society of America (2013) 497: 117-153

Abstract

We examined Grande Ronde Basalt lava flows from surface sections and boreholes throughout Washington, Oregon, and Idaho to determine chemical and physical properties that would allow the recognition and mapping of these flows on a regional scale. We estimate there are approximately 100 flows covering nearly 170,000 km (super 2) , with a total volume of approximately 150,400 km (super 3) , that were erupted over four polarity intervals (reverse 1, normal 1, reverse 2, and normal 2) in approximately 0.42 m.y. These flows are the largest known on Earth, with individual volumes ranging from approximately 100 km (super 3) to greater than 10,000 km (super 3) . Although all known Grande Ronde Basalt flows erupted in the eastern part of the Columbia River flood basalt province, the thickest and most complete sections (>3 km) occur in the central Columbia Basin. From the center of the basin, the number of flows decreases outward, resulting in a nearly complete stratigraphy in the interior and an abbreviated and variable stratigraphy along the margins. The areal extent of many flows suggests that the Chief Joseph dike swarm greatly expanded after Imnaha Basalt time, and now many dikes are buried beneath younger flows in the eastern part of the province. The Grande Ronde Basalt has a relatively uniform lithology with only a few distinctive flows. However, when compositions are combined with paleomagnetic polarity, lithology, and stratigraphic position, the Grande Ronde Basalt can be subdivided into at least 25 mappable units. Grande Ronde Basalt flows are siliceous, with typically SiO (sub 2) >54 wt%, MgO contents ranging from approximately 2.5 to 6.5 wt%, and TiO (sub 2) ranging from 1.6 to 2.8 wt%, with an enrichment in iron and incompatible elements relative to mid-ocean-ridge basalt. Although most Grande Ronde Basalt flows have homogeneous compositions, some are heterogeneous. Dikes that fed the heterogeneous flows show that the first composition erupted was not typical of the flow, but as the eruption progressed, the compositions gradually evolved to the bulk composition of flow. The average effusion rate was approximately 0.3 km (super 3) /yr, with basalt volume peaking during the R2 polarity with the eruption of the Wapshilla Ridge Member. Eruption and emplacement rates for the flows are controversial, but available data collected from the field suggest that many of the flows could have been emplaced in a few years to perhaps a decade.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 497
Title: The Grande Ronde Basalt, Columbia River Basalt Group
Title: The Columbia River flood basalt province
Author(s): Reidel, Stephen P.Tolan, Terry L.
Author(s): Reidel, Stephen P.editor
Author(s): Camp, Victor E.editor
Author(s): Ross, Martin E.editor
Author(s): Wolff, John A.editor
Author(s): Martin, Barton S.editor
Author(s): Tolan, Terry L.editor
Author(s): Wells, Ray E.editor
Affiliation: Washington State University, School of the Environment, Richland, WA, United States
Affiliation: Washington State University, School of the Environment, Richland, WA, United States
Pages: 117-153
Published: 2013
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 978-0-8137-2497-3
References: 99
Accession Number: 2013-086824
Categories: Igneous and metamorphic petrologyStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., 3 tables, geol. sketch maps
N43°00'00" - N48°30'00", W124°00'00" - W116°00'00"
Secondary Affiliation: San Diego State University, USA, United StatesNortheastern University, USA, United StatesOhio Wesleyan University, USA, United StatesPortland State University, USA, United StatesU. S. Geological Survey, USA, United StatesPortland State University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201351
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