Graduation Date

Fall 2021

Document Type

Thesis

Program

Master of Science degree with a major in Environmental Systems, option Geology

Committee Chair Name

Dr. Melanie Michalak

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Dr. Susan Cashman

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Dr. Mark Hemphill-Haley

Third Committee Member Affiliation

HSU Faculty or Staff

Subject Categories

Geology

Abstract

The Klamath Mountains Province (KMP), located at the southern end of the forearc of the Cascadia Subduction Zone, displays a distinct topographic and geologic signature. Compared to the forearc in the north, the KMP comprises Paleozoic-Mesozoic basement rocks with relatively high modern elevation and relief. This study investigates the pattern of rock cooling in the KMP by using thermochronology on plutons exhumed by faults and plutons outside of mapped faults. In this study, I target three regions in the KMP: the Ashland pluton offset by the Siskiyou Summit fault in the northeast KMP, the Grayback pluton in the northwest KMP, and the China Creek pluton offset by the Browns Meadow fault in the southern KMP. Zircon (ZHe) and apatite (AHe) (U-Th)/He ages from these plutons record post emplacement cooling during the late Early Cretaceous and tectonic exhumation during the late Oligocene to early Miocene. Cooling ages from this study are compiled with available thermochronologic data to identify spatial and temporal patterns of exhumation. This comparison shows a late Oligocene to early Miocene cooling signal throughout the KMP, with the exception of a geographic cluster of late Eocene to early Oligocene AHe ages found in the south-central core of the KMP. This cluster of older cooling ages is bound by the Browns Meadow fault and La Grange fault, indicating Tertiary faulting influenced exhumation in the southern KMP. However, the pervasive late Oligocene to early Miocene cooling signal suggests regional erosion is a more important factor influencing rock cooling than previously thought.

Citation Style

GSA

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