Award Date

2009

Degree Type

Thesis

Degree Name

Master of Science in Geoscience

Department

Geoscience

Advisor 1

Andrew Hanson, Committee Chair

First Committee Member

Stephen Rowland

Second Committee Member

Wanda Taylor

Graduate Faculty Representative

Vernon Hodge

Number of Pages

160

Abstract

The provenance, stratigraphy, and depositional history of the Miocene-Pliocene Muddy Creek Formation (MCF) in southern Nevada are poorly studied and poorly constrained. Previous studies of the MCF have concluded that the formation consists of lacustrine, eolian, and fluvial deposits. Currently the age of deposition is loosely constrained between 8.5 and 4.1 Ma. This study documents the evolution of one portion of the eastern extent of the MCF and determines its provenance and depositional history at Flat Top and Mormon Mesas in Nevada; and near Beaver Dam and Littlefield, Arizona.

This study intended to determine whether the MCF was deposited by a paleo-Colorado River that flowed through the Virgin River Gorge and into the Mesquite basin prior to ~5.5 Ma. Methods used in this study included petrographic analyses, detrital zircon analyses, facies analyses, paleocurrent indicators, and conglomerate clast counts. Detrital zircons from the MCF, a Pliocene unit near Littlefield, Arizona, and modern day Virgin River were compared to previously analyzed zircons from the Bidahochi Formation and known Colorado River zircons.

Results from the MCF in the Beaver Dam Wash and at Flat Top Mesa indicate paleotransport was to the south-southeast and south-southwest respectively and in an inset Pliocene unit near Littlefield, Arizona paleotransport was to the south-southwest. Based upon sedimentological data the MCF within the study area was deposited in a fluvial environment. Conglomerate clasts and sandstone petrography from the MCF at Mormon Mesa indicate mixed volcanic, metamorphic, and sedimentary sources for the sediment which is dissimilar to deposits at Flat Top Mesa and Beaver Dam Wash which were derived from a volcanic source. The provenance data indicate the MCF at Flat Top Mesa and Beaver Dam Wash were derived from the Caliente Caldera complex, while the deposits at Mormon Mesa were derived from both the Caliente Caldera complex and the Colorado Plateau, which was deposited by a paleo-Virgin River. Results from an inset Pliocene unit in the Beaver Dam Wash indicate this unit was derived from the Caliente Caldera complex. In contrast, results from an inset Pliocene unit near Littlefield, Arizona indicate it was derived from the Colorado Plateau and deposited by a paleo-Virgin River. Despite the MCF at Mormon Mesa having a partial Colorado Plateau provenance results are consistent with previous models that indicated that neither the younger units nor the portions of the MCF that were studied were deposited by a paleo-Colorado River.

Keywords

Caliente Caldera complex; Detrital zircon analysis; Geology; Miocene; Muddy Creek Formation; Nevada; Paleo-Colorado River; Pliocene; Provenance; Sedimentology; Virgin River Gorge

Disciplines

Geology

Language

English


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