Date of Award:

8-2022

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Committee Chair(s)

Alexis K. Ault

Committee

Alexis K. Ault

Committee

Kelly K. Bradbury

Committee

James P. Evans

Abstract

Fault slip relieves stress in the shallow crust by slipping suddenly during earthquakes, but some faults also slip slowly in between earthquakes. Exhumed faults, brought up to the Earth’s surface from depth, preserve a record of fault processes and slip rates informed by fault rock structures, textures, and chemistry. Hematite, a common iron oxide mineral that precipitates on fault surfaces, exhibits crystal textures that potentially indicate past slip rate. Hematite can be dated using the radioisotopic system of (U-Th)/He thermochronometry, which constrains the time when He is trapped within a crystal, a process that is a function of temperature. Exhumed faults that are parallel and connect to the San Andreas Fault (southernmost California) at depth cut crystalline rock and contain networks of small, hematite-coated faults. Here, hematite displays crystal morphology and structures that indicate hematite formed episodically a formation, repeatedly slipped at slow rates. Hematite (U-Th)/He dates show hematite formed at shallow depths (

Checksum

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Included in

Geology Commons

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