Date of Award:

12-2019

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

Joel Pederson

Committee

Joel Pederson

Committee

Tammy Rittenour

Committee

Patrick Belmont

Abstract

Since the earliest explorations of the Colorado Plateau, geologists have suspected that cliffs are retreating back laterally. Clarence Dutton envisioned “the beds thus dissolving edge wise until after the lapse of millions of centuries their terminal cliffs stand a hundred miles or more back from their original position” when he wrote about the landscape in 1882. While many geologic studies have determined how fast rivers cut down through the Plateau, only a few studies have calculated how quickly cliffs retreat laterally, and geologists have been arguing since the 1940’s what exactly drives cliffs to retreat in the first place. We study the Book Cliffs in central Utah, and in particular remnant landforms and deposits related to a 120,000-year history of erosion and deposition, which we date by optically stimulated luminescence methods. Our dataset shows that deposits along the Book Cliffs are preserved especially during times of climate instability, which suggests that escarpment retreat locally is driven by climatic disturbances. This disproves older hypotheses suggesting escarpments retreat in response to local factors regardless of shifts in climate, and it is consistent with the few other well-studied escarpment records globally. We also constrain the rates of cliff retreat via a new measurement approach and luminescence age control, showing that the Book Cliffs have retreated at 1-3 meters per thousand years while local toeslope drainages have incised at about 0.5 meters per thousand years, which confirms that cliffs of shallow-dipping, layered rock retreat laterally faster than streams lower the landscape vertically.

Checksum

c37d5263b9a8f0dc01a5d79e9c0a5d95

Download

Included in

Geology Commons

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .