Date of Award:

8-2024

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Geosciences

Committee Chair(s)

Tammy M. Rittenour

Committee

Tammy M. Rittenour

Committee

Joel L. Pederson

Committee

Evey Gannaway-Dalton

Committee

Frank J. Pazzaglia

Committee

Colin B. Phillips

Abstract

Landscapes change over time in response to movements of the Earth’s crust and the effects of climate. This dissertation examines how these factors shape different landscapes, focusing on erosion of river canyons in elevated plateaus, how the transport history in quartz sand may be encoded in its properties, and how a paleo-delta has formed in response to sea-level change and fault displacement. I use dating techniques, field methods, and topographic analyses to offer insight into erosional patterns and rates in different landscapes.

Rivers can take a long time to adjust to changes in boundary conditions, even after those changes have ceased. I studied the Colorado River incision history in the tectonically stable central Colorado Plateau of Utah, to understand the timing, spatial variability, and controls on canyon carving. The incision history and topography of the region show remarkable variability in erosion across the region and through time, with significant rapid incision of ~250 meters in the last 350,000 years. Results suggest this rapid erosion is a signal derived from baselevel fall by the Colorado River in the Grand Canyon region 5 million years ago. This study shows that even without major tectonic or climate change, landscapes can still maintain complex erosion patterns.

Optically stimulated luminescence sensitivity is a new technique used to study Earth’s surface processes. However, the geologic processes that induce a luminescence phenomenon in quartz are still unknown. I investigate the geologic controls on the luminescence sensitivity of quartz sand using rocks and modern and paleo- river sediments in a small mountainous catchment in northern Utah, USA. The results indicate that the luminescence phenomena in quartz is enhanced with the time spent at the Earth’s surface as the sand grain weathers, erodes, and is transported along hillslopes to river systems.

The Pagliara fan-delta in northeastern Sicily provides a unique opportunity to study how coastal sediments stack through time in response to climate and sea-level change and tectonic history. Dating of the delta using luminescence techniques, reveals that the delta formed 300 – 220 thousand years ago when accommodation space was generated by sea-level fall and subsidence from fault movement. After this time, river and shore processes began to excavate the delta, indicating a shift from sediment accumulation in the delta to tectonic uplift. Despite the change in tectonic stress revealed in the delta stratigraphy, the uplift and erosion rates of the region have remained relatively constant over the past 300,000 years.

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