Award Date

12-1-2016

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

First Committee Member

Andrew D. Hanson

Second Committee Member

Terry Spell

Third Committee Member

Wanda J. Taylor

Fourth Committee Member

Andrew Andres

Number of Pages

77

Abstract

The Onion Creek salt wall in Fisher Valley, Utah is an exposed salt structure that lies adjacent to sandstones of the Permian age Cutler Group. The thermal conductivity of salt is two to four times greater than other sedimentary rocks and has been shown to act as a regional conduit for heat flow which has implications for petroleum systems in hydrocarbon exploration. Numerical models predict that thermal anomalies should extend 1.5 times the radius of a salt structure into adjacent strata. I hypothesized that an elevated paleothermal anomaly exists in sandstones of the Cutler Group where they are located near the top of the salt wall. If the hypothesis is correct, thermochronologic ages should increase as distance from the salt wall increases because of elevated temperatures near salt. Additionally, the occurrence of silica cements should decrease with increasing distance away from salt. Apatite/zircon-He ages were determined for nine samples to test for a paleothermal anomaly. I also conducted an analysis of cementation in samples collected along a transect perpendicular to the salt wall. Apatite-He ages range from 33.3 ± 0.8 Ma to 17.9 ± 3.5 Ma and zircon-He ages range from 721 ± 15 Ma to 204 ± 147 Ma. Few silica cements were observed in the samples and the vast majority of cements are calcite which have no implications for paleotemperatures. The data show no definitive evidence for a paleothermal anomaly in the Cutler Group based on either the thermochronologic ages or the cementation analysis. I infer that both thermohaline convection of pore fluids and heterogeneous salt wall compositions may have masked the presence of a thermal anomaly if one existed. Apatite-He ages are reset but uniquely old given their location within the Colorado Plateau and suggest exhumation due to uplift associated with emplacement of the La Sal laccolith (~ 25 Ma). Zircon-He ages reflect exhumation in the Neoproterozoic possibly related to rifting of the supercontinent Rodinia.

Keywords

Onion Creek; Salt Tectonics; Salt Thermal Anomalies; Salt Wall; Thermochronology; Zircon

Disciplines

Geology

Language

English

Available for download on Wednesday, December 15, 2021


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