Date of Award

6-1988

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Nicholas B. Woodward

Committee Members

Theodore Labotka & Steven Driese

Abstract

The Precambrian Thunderhead Sandstone, along the Greenbrier Fault and the Roundtop Klippe, records strain from two distinct episodes of deformation. The first strains are generally related to the emplacement of the Greenbrier Fault. These strains are probably due to simple shear along the base of the fault, and appear similar to the strain fabrics within in the Cades Sandstone to the southwest. This strain fabric is characterized by principle strain axes which lie subparallel to the orientation of the Greenbrier Fault. These strains were later effected by strains related to the emplacement of the Sinks Fault, a high angle thrust which displaced the Greenbrier Thrust Sheet. This fabric is probably also the result of simple shear on the Sinks and is similarly characterized by the subparallelism of the principal extension axes and the Sinks Fault plane.

Finite strains were calculated for 17 samples of Thunderhead Sandstone, using the Rf/o and Fry methods. Twelve samples show that uniaxial extension is dominant over flattening within the Thunderhead. In five samples flattening is dominant over uniaxial extension. The Greenbrier main sheet shows less strain in the same orientations than that seen in the Roundtop Klippe. King (1964, 1968) shows two interpretations of the area, one with the Sinks as a folded part of the Greenbrier and one with the Sinks as a later fault. Superposed strain patterns suggest that both are correct.

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