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Date Permissions Signed
Date of Award
Master of Science (MS)
Amos, Colin B.
Schermer, Elizabeth, 1959-
Clark, Douglas H., 1961-
New geomorphic mapping and cosmogenic 3He geochronology on the Western Klamath Lake fault zone in southern Oregon reveals moderate, but resolvable changes in the rate of normal-fault slip rates over the past ~170 kyr. We focus on a sequence of glacial and post-glacial surfaces that record progressive offset by the fault zone over multiple time intervals. Thirty-nine new cosmogenic 3He surface exposure dates and a cosmogenic nuclide depth profile establish the first late-Pleistocene glacial chronology in the Cascade Range of Oregon and constrains the timing of the last two major glacial advances in the region at 17.6 ± 2.1 ka and 97.6 ± 12.1 ka. Additionally, these data provide an estimate for the timing of an older glacial advance, likely coincident with MIS 6. Measurements of fault scarp profiles from high resolution airborne lidar provide insights into the structure of the Klamath Basin and suggest that despite a complex surface expression, individual fault strands likely merge to a single fault at depth. These measurements, coupled with the new surface chronology, allow the reconstruction of slip rates across the Western Klamath Lake fault zone over intervals of ~104 – 105 years. Our calculations indicate dip slip rates of ~0.3 mm/yr since ~100 ka, which may represent an increase from < 0.1 mm/yr prior to ~100 ka.
Western Washington University
Subject – LCSH
Faults (Geology)--Oregon--Klamath Basin; Strike-slip faults (Geology)--Oregon--Klamath Basin; Geomorphological mapping--Oregon--Klamath Basin; Geological time; Cosmogenic nuclides; Geology, Structural
Klamath Basin (Or.)
Copying of this thesis in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Speth, Gunnar, "Testing the time dependence of slip on the western Klamath Lake fault zone, Oregon" (2017). WWU Graduate School Collection. 598.