Date of Award:

8-2013

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

Joel L. Pederson

Committee

Joel L. Pederson

Committee

Patrick Belmont

Committee

Tammy M. Rittenour

Abstract

The history of rivers is laid down as sediment in all landscapes, typically as a function of climate, geologic structures, and/or changes in sea level. When a river abandons its floodplain, this sediment collectively constitutes a landform called a fluvial terrace. Terraces are used to unlock prior characteristics of a river flowing through a given area at both local and regional scales. Dating terrace sediment allows comparison to known changes in climate and geologic deformation, two significant controls on the hydraulics of rivers and the deposition of their sediment loads.

The importance of terraces lies in their utility as markers of climate change and geologic deformation. By constructing a record of terrace formation by large rivers such as the Colorado, we develop the capacity of predict how a river system will respond to changing climate or geologic events such as the rupturing of faults or the uplift of the Earth's surface. These capabilities permit informed decisions wherever humans live along or otherwise depend on rivers, including water management and floodplain zoning.

We describe the history of the Colorado River upstream of Moab, Utah over the last 100,000 years. By dating terrace sediment and taking topographic surveys of terrace shape and form, we identify patterns in climate change and geologic deformation related to subsurface salt deposits. Our findings imply that the Colorado River is sensitive to both of these controls, especially in terms of where it deposits its sediment load, how much sediment is deposited, and the timing of floodplain abandonment.

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