Document Type

Thesis

Abstract

The Fish Lake Plateau in central Utah provides a unique opportunity to study the interactions between tectonic and surficial processes. Cedarless Flat Basin, an ~ 3 km long and 1 km wide topographic basin ~ 15 km to the SE of Fish Lake bounded by two NE-SW striking normal faults. These faults appear to truncate the previously existing drainage network of Brigg’s Hollow. Brigg’s Hollow is divided into two sections by Cedarless Flat; the upstream section that has its headwaters NW of Cedarless Flat and flows SE into Cedarless Flat and the downstream section SE of Cedarless Flat that flows into the Mill Meadow Reservoir. The NW section of Brigg’s Hollow is ~8.3 km long and has a drainage area of ~30 km’ and appears to deposit a layer of sediment into Cedarless Flat. To understand the structural geometry of Cedarless Flat we mapped ~20 km? centered around the Cedarless Flat basin. The area is underlain by three volcanic units (from bottom to top): 1) phenocryst-rich andesite, 2) phenocryst poor trachyte, and 3) the Osiris Dacite. Displacement of ~110 m is accommodated by the faults. Gravity surveys were conducted along both the SW-NE and NW-SE trending axes of the Cedarless Flat basin in an effort to determine the thickness of the alluvial deposit. Modeling of the resulting Bouguer anomalies shows that sediment thickness varies throughout the graben with the thickest deposits of sediment being ~50 m in the NE and the thinnest being ~5 m near the center. *He exposure ages of an adjacent paleo-surface allow for relative dating of the initiation of the faulting that formed Cedarless Flat. The exposure ages reveal that faulting must have began no earlier than ~900 ka as the paleo-surface has been incised by Brigg’s Hollow, which has in turn been truncated by Cedarless Flat. This leads to a minimum rate of faulting of ~0.012 cm yr-1.

Date Awarded

2006

Department

Geology

Advisor 1

Christopher M. Bailey

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