Date of Award:

1987

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geology

Advisor/Chair:

James P. McCalpin

Abstract

The Smithfield 7.5' quadrangle is located about 13.8 kilometers (8.6 miles) south of the Utah-Idaho State Line and occupies the central portion of the eastern side of Cache Valley, Utah. The mapped area contains more than 55 square miles. The Bear River Range on the eastern side of the quadrangle contains stratigraphic units ranging from Precambrian to Quaternary age. Cache Valley contains deposits of Tertiary and Quaternary age. Quaternary units in the Smithfield quadrangle are subdivided into thirty-two map units based on age and genesis. Five ages of Quaternary units are identified, and these units are assigned to one of fourteen genetic types. The East Cache fault zone is mapped along the western edge of the Bear River Range.

Early Quaternary time was principally a period of pediment formation, followed by normal faulting, erosion, and alluvial-fan deposition. Cache Valley was later occupied by a pre-Bonneville cycle lake which is tentatively correlated with the Little Valley lake cycle. This lacustrine cycle was followed by more erosion and alluvial-fan deposition. The current Cache Valley landscape is dominated by the sediments and geomorphic features of Pleistocene Lake Bonneville. Alluvial-fan deposition has been the principal geologic process in post-Lake Bonneville time.

Geologic hazards in the Smithfield quadrangle include flooding, landslides, debris flows, rock fall, problem soils, shallow ground water, earthquake ground shaking, surface fault rupture, and liquefaction. Some of the areas affected by these hazards and measures for mitigating the hazards are identified. Bonneville lake cycle fine-grained offshore deposits and the Tertiary Salt Lake Formation are the primary geologic units susceptible to landsliding.

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