Publication Date

1996

Document Type

Dissertation/Thesis

First Advisor

Stoddard, Paul

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Geology

LCSH

Geology--South Dakota--Fall River County; Sandstone--South Dakota--Fall River County

Abstract

The sandstone structures that occur within the Skull Creek and Mowry shale units in Fall River County, South Dakota, and throughout the southern Black Hills uplift have been the subject of very few studies. The origin of the sediments and the nature of the forces that caused the structures to form has been disputed since Darton first discovered them in 1901. The sediments have been determined to have been derived from a discontinuous sandstone bed that occurs within the Mowry shale. The morphology of the lenses and dikes indicates that they are the result of the fluidization of the discontinuous sandstone bed. This fluidization occurred as the result of either overpressuring of the sediments from the compaction of the surrounding shale, or cyclic loading due to seismic shaking. It has not yet been determined which of these processes caused the liquefication, or if the liquefication was the result of a combination of both processes. The lenses and dikes have also been subjected to secondary structural and mineralogic alteration. The orientation of the dikes and the joints within the lenses can be related to the regional fracture systems, and have been inferred to have occurred contemporaneously with the formation of the regional joint system, after the emplacement and lithification of the lenses and dikes. Also, the replacement of the cementing agents in the sediments by iron oxide has been observed. These observations and conclusions have provided a new, and very different, explanation of the sandstone lenses and dikes that occur within the study area and throughout the southern Black Hills uplift.

Comments

Includes bibliographical references (pages [86]-88)

Extent

xi, 133 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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