Publication Date

Summer 2017

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

Advisor

Emmanuel Gabet

Keywords

ancient, Eocene-Oligocene, gold, gravels, paleochannels, Sierras

Subject Areas

Geomorphology; Geology

Abstract

The Tertiary gravels deposited along the western flank of the Sierra Nevada mountains elucidate the nature of the paleochannels and paleotopography of the range in the Eocene-Oligocene epochs. Numerous geologic maps and studies were compiled to place existing Tertiary gravels onto topographic maps and cross-sections extracted from ArcGIS. Based on the remnant deposits, the extent of deposition of the gravels during the Eocene-Oligocene epoch was inferred, and average end-area values were measured from the cross-sections to calculate the volume of the Tertiary gravels that was originally deposited. The map of the inferred deposits was also used to measure surface gradients of the gravels and compare them to deposits of active fluvial systems. This study calculated that 197-290 km3 of gravels were originally deposited and that surface gradients ranged from 0.004 to 0.034 (0.229° to 1.95°). The map shows that the gravels were widely distributed across the west sloping ramp of the north and central Sierras, and the cross-sections suggest that the river valleys were deeply incised and filled with Tertiary gravels. The early Cenozoic Sierran landscape consisted of a tall, rugged mountain range carved by paleochannels that were subsequently buried by gold-bearing gravels during the Eocene and Oligocene epochs.

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