Award Date

6-1966

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

Number of Pages

69

Abstract

The Las Vegas 15-minute quadrangle, located in the south part of the state of Nevada, includes about 240 square miles in and around the city of Las Vegas; it is in the basin and range province. The quadrangle includes a broad valley floor that was once a lake bottom, a bordering area of badlands and rolling hills developed in Tertiary and Quaternary deposits, an outer marginal area of alluvial fans, and the surrounding mountains.

The mountains constitute about three per cent of the total land surface and are composed of rock ranging in are from Precambrian to Tertiary. The remainder of the area is underlain with Pliocene(?), Pleistocene, and Recent "unconsolidated" sediments. The lowermost of these deposits is the Pliocene(?) Muddy Creek Formation which is composed largely of sand and silt with some clay, gravel, and evaporites. Much of the sand and silt is indurated to form caliche. A fanglomerate of Pleistocene(?) are is the oldest unit exposed above the Muddy Creek Formation.

In late Pleistocene time a deep lake occupied Las Vegas Valley. According to C.V. Haynes (1965), beds deposited by this lake have yielded radiocarbon dates ranging from 35,000 B.P. to 15,000 B.P. C.R. Longwell and others have named these beds the Las Vegas Formation. The youngest deposits in the area are very late Pleistocene and Recent gravels and eolian sand.

Several prominent escarpments are seen on the surface of the Las Vegas and Muddy Creek Formations. These scarps apparently are of either fault or wave-cut origin or perhaps were formed by a combination of faulting and erosion. evidence available at the present time does not conclusively prove their origin.

Sand and gravel for construction use is obtained from eolian sand and Recent alluvium. Building foundation conditions are, in general, very good, but local problems are created by expansive soil and sulfate salts. The area's water supply is derived almost entirely from wells. The Las Vegas valley floor has subsided more than two feet during the past 20 years, and since 1960 localized fissuring of the land surface has occurred. Malmberg (1964) presented evidence which indicates that these land movements are due to the withdrawal of ground water.

Keywords

Geomorphology; Geology; Nevada – Las Vegas Valley; Sedimentology

Disciplines

Geology | Geomorphology | Sedimentology | Soil Science

Language

English

Comments

Signatures have been redacted for privacy and security measures.


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