Quaternary upper plate deformation in coastal Oregon

Abstract

Research Article| July 01, 1996 Quaternary upper plate deformation in coastal Oregon Harvey M. Kelsey; Harvey M. Kelsey 1Department of Geology, Humboldt State University, Arcata, California 95521 Search for other works by this author on: GSW Google Scholar Robert L. Ticknor; Robert L. Ticknor 274 Russell Avenue, Watertown, Massachusetts 02172 Search for other works by this author on: GSW Google Scholar James G. Bockheim; James G. Bockheim 3Department of Soil Science, University of Wisconsin, Madison, Wisconsin 53706 Clifton Search for other works by this author on: GSW Google Scholar E. Mitchell E. Mitchell 4Science Department, Lane Community College, Eugene, Oregon 97403-0640 Search for other works by this author on: GSW Google Scholar Author and Article Information Harvey M. Kelsey 1Department of Geology, Humboldt State University, Arcata, California 95521 Robert L. Ticknor 274 Russell Avenue, Watertown, Massachusetts 02172 James G. Bockheim 3Department of Soil Science, University of Wisconsin, Madison, Wisconsin 53706 Clifton E. Mitchell 4Science Department, Lane Community College, Eugene, Oregon 97403-0640 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1996) 108 (7): 843–860. https://doi.org/10.1130/0016-7606(1996)108<0843:QUPDIC>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 Email Permissions Search Site Citation Harvey M. Kelsey, Robert L. Ticknor, James G. Bockheim, E. Mitchell; Quaternary upper plate deformation in coastal Oregon. GSA Bulletin 1996;; 108 (7): 843–860. doi: https://doi.org/10.1130/0016-7606(1996)108<0843:QUPDIC>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 The leading edge of the North American plate along the Cascadia subduction zone is deforming and rotating clockwise as a consequence of both underthrusting of the Gorda- Juan de Fuca plate and collision of the North American plate with the Pacific plate. The details of late Quaternary (≤125 ka) upper-plate deformation resulting from these plate interactions are largely obscured because the most recent deformation overprints earlier deformation in the Tertiary rocks of the Coast Range. However, by mapping uplifted wave-cut platforms formed during times of high sea level in the past ≈500 000 yr, we identify faults and folds active in the late Quaternary in central coastal Oregon. Through a long-coast correlation of these platforms using elevation and soil development, we infer that several major faults have vertically offset platforms at rates as high as 0.6 m/k.y. for the past 125 k.y. We regionally extend our analysis by incorporating all known faults and folds in southern and central coastal Oregon that deform wave-cut platforms. Most platforms along the southern and central Oregon coast have been uplifted at rates of 0.1–0.3 m/k.y. since the late Pleistocene; however, platform uplift rates approach 1 m/k.y. in the vicinity of faults. The trend and distribution of these upper-plate coastal faults are consistent with their interpreted role as left-lateral, strike-slip, block-bounding structures accommodating clockwise rotation. We speculate that these upper-plate faults have a component of dip slip because of their association, in many instances, with localized uplift. If these faults bound rotating blocks, the dip-slip component of displacement may be either contractional or extensional, depending on the orientation of the fault relative to the north-south trend of the plate margin. 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.