Date of Award:

5-1972

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

Robert Q. Oaks, Jr.

Committee

Robert Q. Oaks, Jr.

Committee

Donald R. Olsen

Committee

J. Stewart Williams

Abstract

The Swan Peak Formation in north-central Utah thickens westward, from zero feet near Logan to 687 feet in the Promontory Range. The unit is subdivided into three distinct members: 1) A lower member of interbedded shales, limestones, and quartzites; 2) A middle member of interbedded shales and brown quartzites; and 3) An upper member of white quartzites. The Swan Peak thins southward toward the east-west-trending Tooele Arch in the area of study; this thinning probably reflects both lesser deposition and greater subsequent erosion there than elsewhere. The lower member in northern Utah probably was deposited in shallow-shelf and/or traditional shoreface-shelf environments. The middle member represents shoreface to intertidal environments. Western miogeosynclinal equivalents of the lower and middle members are more carbonate-rich, the results of their more basinward position and thus greater distance from terrigenous sediment sources. The upper member was deposited in a shallow-shelf to intertidal environment by strong, predominantly south-flowing currents.

The Eureka Quartzite in northwestern Utah thickens northward from 288 feet near the Tooele Arch to 542 feet in the Silver Island Mountains near the Nevada state line. It consists of unfossiliferous, white to medium light gray quartzite. The Eureka represents a shallow-shelf to intertidal environment swept by strong, predominantly south-flowing currents.

Correlation of the upper member of the Swan Peak Formation in north-central Utah and southeastern Idaho with the Eureka Quartzite in northwestern Utah appears well established, on the basis of: 1) A previously unrecognized low-angle regional unconformity at the base of the upper member; 2) Similar thicknesses of the easternmost Eureka and the westernmost upper member, first recognized by Webb (1956. Middle Ordovician detailed stratigraphic sections for western Utah and eastern Nevada. Utah Geol. and Mineral. Survey, Bull. 57, 77 p.); 3) Similar south-flowing paleocurrents for both; 4) Distinctive and identical trace fossils in both; 5) Identical lighologic characteristics; and 6) Similar stratigraphic position below the Fish Haven Dolomite, and above similar time-correlative faunal suites of Ross (1951. Stratigraphy of the Garden City Formation in northeastern Utah, and its trilobite faunas. Peabody Mus. Nat. Hist., Yale Univ., Bull. 6, 161p) and of Hintze (1952. Lower Ordovician trilobites from western Utah and eastern Nevada. Utah Geol. and Mineral. Survey, Bull. 48. 249 p.).

Fossil assemblages in the lower and middle members of the Swan Peak Formation are chiefly mixed and transported assemblages, although residual fossil communities persist locally. Diversity and density of trace fossils show that numerous unpreserved soft-bodied organisms contributed significantly to the community structure of the Swan Peak Formation and Eureka Quartzite in northern Utah.

Checksum

562bd6e13caf890b881977614ec5424a

Download

Included in

Geology Commons

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .