Chemical Variation Related to the Stratigraphy of the Columbia River Basalt

Abstract

Research Article| February 01, 1973 Chemical Variation Related to the Stratigraphy of the Columbia River Basalt THOMAS L. WRIGHT; THOMAS L. WRIGHT 1U.S. Geological Survey, Washington, D.C. 20242 Search for other works by this author on: GSW Google Scholar MAURICE J. GROLIER; MAURICE J. GROLIER 1U.S. Geological Survey, Washington, D.C. 20242 Search for other works by this author on: GSW Google Scholar DONALD A. SWANSON DONALD A. SWANSON 2U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1973) 84 (2): 371–386. https://doi.org/10.1130/0016-7606(1973)84<371:CVRTTS>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation THOMAS L. WRIGHT, MAURICE J. GROLIER, DONALD A. SWANSON; Chemical Variation Related to the Stratigraphy of the Columbia River Basalt. GSA Bulletin 1973;; 84 (2): 371–386. doi: https://doi.org/10.1130/0016-7606(1973)84<371:CVRTTS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Note: This paper is dedicated to Aaron and Elizabeth Waters on the occasion of Dr. Waters' retirement.Study of major element chemical analyses of Columbia River basalt leads to a grouping of most of the analyses into 11 chemical types which are distinguished with little overlap on a SiO2-MgO variation diagram. Other diagnostic variation diagrams are total iron (‘FeO’)-MgO, K2O-MgO, and TiO2-MgO.A four-unit informal stratigraphy has been adopted in order to define the relations between chemical composition and stratigraphic position. From oldest to youngest, the four stratigraphic units are (1) lower basalt of Bond (1963) and Picture Gorge basalt, (2) lower Yakima basalt, (3) middle Yakima basalt, and (4) upper Yakima basalt.Most of the Picture Gorge and lower basalt flows are relatively rich in MgO (approximately 4.5 to 7.1 percent) and are distinguished by intermediate SiO2 relative to MgO. Furthermore, the Picture Gorge basalt generally has low K2O relative to MgO. The lower Yakima basalt consists almost entirely of flows with relatively low MgO content (approximately 3.0 to 5.5 percent) and with the highest SiO2 relative to MgO of any flows of the Columbia River basalt. The middle Yakima basalt contains flows of three distinct chemical types, which together cover the same MgO range as the lower Yakima flows but which have considerably lower SiO2 and higher ‘FeO’ and TiO2 relative to MgO. Flows in the upper Yakima basalt are of diverse composition; two of the youngest flows are distinguished by having the lowest SiO2 and highest ‘FeO’, TiO2, and P2O5 relative to MgO of any analyzed Columbia River basalt.Flows of one or more chemical types may form the dominant lithology in a stratigraphic unit, but single flows of the same chemical types may occur in any stratigraphic unit.Some lava sampled in the eastern part of the plateau has more TiO2 than does lava of otherwise similar composition sampled in the western part of the plateau. This is tentatively interpreted as reflecting a heterogeneous composition for the mantle beneath the Columbia Plateau. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.