Upper-crustal structure beneath the Columbia River Basalt Group, Washington: Gravity interpretation controlled by borehole and seismic studies

Abstract

Research Article| September 01, 1993 Upper-crustal structure beneath the Columbia River Basalt Group, Washington: Gravity interpretation controlled by borehole and seismic studies R. W. SALTUS R. W. SALTUS 1U.S. Geological Survey, Federal Center, M.S. 964, Denver, Colorado 80225-0046 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1993) 105 (9): 1247–1259. https://doi.org/10.1130/0016-7606(1993)105<1247:UCSBTC>2.3.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 R. W. SALTUS; Upper-crustal structure beneath the Columbia River Basalt Group, Washington: Gravity interpretation controlled by borehole and seismic studies. GSA Bulletin 1993;; 105 (9): 1247–1259. doi: https://doi.org/10.1130/0016-7606(1993)105<1247:UCSBTC>2.3.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 A three-dimensional gravity model based on deep-borehole stratigraphy, densities from borehole gravimetry, and crustal structure from deep seismic and electrical surveys puts limits on sub-basalt crustal structure in the northwest quadrant of the Columbia Plateau, Washington. The gravity model indicates that the Miocene Columbia River Basalt Group (CRBG) overlies a broad basin filled with sedimentary rocks that reach thicknesses in excess of 5 km; thickest sub-basalt sedimentary rocks are beneath the late Cenozoic Yakima basin. Analysis of residual gravity shows that the Eocene Chiwaukum graben does not continue beneath the CRBG and that sub-basalt sedimentary rocks are not thrust into the cores of the basalt anticlines in the Yakima fold belt. A gravity high that trends north-south in the center of the CRBG is probably caused by a broad basement ridge marked by thinner sedimentary rocks beneath the Columbia River basalts; the western edge of the north-south basement high is traced at the surface by the Hog Ranch-Naneum Ridge. A major crustal feature, the Olympic- Wallowa lineament, is expressed in the gravity field; the lineament crosses the north-south basement high but does not offset it, suggesting that any strike- slip motion on the lineament preceded development of the north-south basement high. An alternative interpretation of the north-south gravity high, based on a previous seismic study, relates it to a high-density structure in the crystalline basement, perhaps associated with a failed continental rift. 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.