Graduation Date

Spring 2022

Document Type

Thesis

Program

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

Committee Chair Name

Melanie Michalak

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Harvey Kelsey

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Tyler Ladinsky

Third Committee Member Affiliation

Community Member or Outside Professional

Fourth Committee Member Name

Robert Witter

Fourth Committee Member Affiliation

Community Member or Outside Professional

Subject Categories

Geology

Abstract

Upper-plate deformation in the southern Cascadia subduction zone is dynamic and complex, situated in the transition between northward translation to westward convergence. Rock uplift and incision rates characteristic of this dynamic region are preserved in suites of fluvial and marine terraces. Fluvial terraces at the Yager Creek–Van Duzen River confluence record fluvial incision rates, and are crosscut by the understudied Goose Lake fault, an upper plate structure. In this work, I use high resolution lidar imagery to map terrace surfaces, and use optically stimulated luminescence, radiocarbon, and Beryllium-10 geochronology to bracket terrace ages and calculate incision and slip rates. With GIS analysis, I mapped 21 fluvial terrace suites and calculated slope aspect for each surface. I mapped three strands of the Goose Lake fault, and calculated vertical separation across each strand. Results show terrace surfaces tilt northward up to 8.6°, and the Goose Lake fault progressively vertically separates terrace surfaces up to 16.6 m up to the south. Age determinations for ten samples from five terraces reveal depositional ages for terrace cover sediment ranging from at least ~47 to ~9 ka. Channel incision rates range from 2.3 to 5.2 mm/yr, and vertical slip rates on the Goose Lake fault range from 0.03 to 0.87 mm/yr. Incision rates, interpreted as rock uplift, indicate regionally rapid uplift in the lower Van Duzen River valley. In contrast, relatively slow slip rates of the Goose Lake fault indicate a distinct and less significant mechanism.

Citation Style

MLA

Included in

Geology Commons

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