Award Date

1-1-1989

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

First Committee Member

Margaret N. Rees

Number of Pages

156

Abstract

The basal conglomerate of the Willow Tank Formation is the initial foreland basin sediment that was derived from highlands created by the Sevier thrust belt and dispersed across an irregular surface of Jurassic Aztec Sandstone in southern Nevada. The conglomerate varies from 5.5 to 34.5 m in thickness and is composed of two compositionally distinct units. The lower conglomerate is composed of Precambrian and Ordovician metaquartz-arenites, and Triassic and Jurassic sedimentary clasts, and its sandstone interbeds and matrix are chert-arenite. This unit represents the initial uplift and erosion of the Gass Peak and William Tank thrusts. The predominance of Paleozoic limestone clasts in the upper conglomerate suggests subsequent erosion of Arrow Canyon, Dry Lake or Muddy Mountain thrusts. The relative timing of movement on these latter three thrusts cannot be determined from the conglomerate composition because they all carry similar Paleozoic limestone sequences; Conglomerate and sandstone lithofacies represent deposition by aggrading and migrating longitudinal bars, dunes, ripples and horizontal plane beds in a braided stream system. Comparison of the vertical and lateral distribution of these lithofacies suggests that the sediments were part of a large proximal braid-plain complex. Measurements of imbricated clasts indicate a predominant west-northwest to east-southeast transport direction.

Keywords

Basin; Clark County; Conglomerate; Cretaceous; Deposition; Foreland; Formation; Initial; Nevada; Sevier; Southern; Tank; Willow

Controlled Subject

Geology

File Format

pdf

File Size

4997.12 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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