Date of Award:

5-2013

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

Tammy M. Rittenour

Committee

Tammy M. Rittenour

Committee

Joel Peterson

Committee

Patrick Belmont

Abstract

Arroyos are steeply entrenched channels that form by incision into weakly consolidated valley-fill alluvium. This study attempts to offers clues into the processes behind their formation by dating arroyo sediments using luminescence and radiocarbon techniques. The importance of understanding arroyo formation is due to a possible linkage with decadal to centennial-scale climate fluctuations. In the 1800s and early 1900s, many of the shallow, perennial streams throughout southern Utah that used for a variety of agricultural and domestic uses were incised up to ~30 m into their alluvium by frequent and high-magnitude flood events. The economical and ecological effects of these floods were substantial, and a possible link to changes in climate could provide insight to future implications.

To better understand the possible influence of climate change to arroyo formation over the last ~7,500 years, field and lab work focused on identifying, describing, and dating sediments from arroyo outcrops in Kitchen Corral Wash, southern Utah. Arroyo outcrops were identified based on cross-cutting relationships in the stratigraphy. Using luminescence and radiocarbon dating to obtain the age of arroyo sediments allows us to reconstruct the alluvial history of Kitchen Corral Wash. To estimate the possible effects of climate change, this study compared the alluvial history of Kitchen Corral Wash with other regional arroyos in southern Utah to identify similarities and differences in the timing of sediment deposition or flood-related incision.

A similar timing in deposition and incision might suggest a stronger climate effect, whereas a different timing in these processes might suggest a geologic threshold within each regional arroyo. Findings in this study indicate that climate effects and geological thresholds both play an important role in the processes of arroyo formation. Funding for this project was obtained from the National Science Foundation grant (NSF-EAR 1057192), a research grant from the Colorado Scientific Society Memorial Funds, and awards from the Utah State University Department of Geology.

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