Earth and Planetary Sciences ETDs

Publication Date

Spring 5-18-2020

Abstract

The advent of plate tectonic theory satisfactorily explained a number of deformation belts around the world. However intracontinental deformation (deformation inboard of a plate margin) remains poorly understood in plate tectonic models. In order to further our understanding of intracontinental tectonics and its effects, this dissertation examines paleotectonic and neotectonic settings within the interior western USA.

Chapter 1 focuses on late Miocene–Recent deformation inboard of the San Andreas plate margin fault and its role on the integration history of the lower Colorado River. The neotectonic analysis included geometric and kinematic fault data collected in key geologic units to characterize the timing and style of deformation in an area that has commonly been considered to lack young deformation. It is found that post-12 Ma deformation in the region is cumulatively significant and persisted before, during, and after deposition of the Bouse Formation – a unit that represents the first arrival of the Colorado River – in a (possibly active) zone of inboard transtension.

The remaining chapters focus on Late Cretaceous and younger tectonism within the Laramide foreland region, a world class study area that is still vigorously debated after over 100 years. Chapter 2 utilizes apatite thermochronology to addresses the timing of Cretaceous (Laramide) and Miocene–Recent tectonism recorded in distinctly situated samples within the Zuni Mountains of west-central New Mexico. Chapter 3, through integrated apatite thermochronology and basin stratigraphy, interprets a ca. 95–70 Ma eastward sweep of Laramide onset of deformation (when it began) across northern Arizona–New Mexico. Chapter 4 scales up the methodology of Chapter 3 with a regional scale compilation effort to interpret an east-northeast directed sweep of time transgressive onset of Laramide deformation from Montana–South Dakota to Arizona–New Mexico during the Late Cretaceous–Paleogene.

These studies contribute to our understanding of plate tectonics and the role that intracontinental deformation plays. Inboard plate margin deformation and its role on river system integration and potential ongoing deformation are described. Likewise, the timing and spatiotemporal patterns of deformation shed light on the tectonic processes that operated during the Laramide orogeny, as well as additional Cenozoic exhumation related to epeirogenic uplift of the western and southwestern United States.

Degree Name

Earth and Planetary Sciences

Level of Degree

Doctoral

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Dr. Karl E. Karlstrom

Second Committee Member

Dr. Laura J. Crossey

Third Committee Member

Dr. Brandon Schmandt

Fourth Committee Member

Dr. Shari A. Kelley

Fifth Committee Member

Dr. Blair Wolf

Keywords

Laramide, Tectonics, Deformation, Transtension, Thermochronology, Stratigraphy

Document Type

Dissertation

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