Earth and Planetary Sciences ETDs

J. R. Morgan

Publication Date

12-1-1967

Abstract

The northern part of the South Virgin Mountains is within the transition zone between the Basin and Range Province and the High Plateaus of the Colorado Plateau. Sedimentary formations in the Paleozoic are represented by more than 6,800 feet of carbonate and elastic sediments. Ordovician rocks are thought to be present, but are not confirmed. Rocks of Silurian age are absent from the area. Triassic and Jurassic units, the Moenkopi Formation, Chinle Formation and the Aztec Sandstone, have a composite thickness of more than 3,700 feet. There are elastic and minor carbonate rocks, all of continental origin, that are of Cenozoic age. Basalt flows and alluvium are believed to be of Quaternary (?) age. Two north-trending Precambrian cored anticlines are believed to be the oldest structures in the area. The South Virgin Mountains probably were tilted to the east by major Basin and Range faults which impart a regional north strike and east dip in the area. Low-angle normal faults, dipping to the west along curved fault planes and cutting the basement rocks, appear to have formed during tilting of the range. After Basin and Range faulting, deformation believed to be related to the Las Vegas shear zone resulted in two major northeast-trending faults. These faults, the Gold Butte and Lime Ridge, are believed to have a strike-slip component as well as a known large dip-slip component. The two main faults divide the area into three fault blocks with left separation. The blocks are downfaulted to the north. A series of north-and northeast-trending faults, shears of the second order and complements of the second order shears, are thought to be related to the major faults. Two minor recent high-angle faults cut Quaternary (?) basalt flows in the area.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Lee A. Woodward

Second Committee Member

Vincent Cooper Kelley

Third Committee Member

Stuart Alvord Northrop

Fourth Committee Member

Charles B. Read

Language

English

Document Type

Thesis

Download

Included in

Geology Commons

Share

COinS