Masters Theses

Date of Award

12-2018

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Robert D. Hatcher Jr.

Committee Members

Micah J. Jessup, Peter J. Lemiszki

Abstract

The Great Smoky fault is a major Alleghanian thrust fault in the southern Appalachians that separates the highly deformed and metamorphosed Blue Ridge to the east from the less deformed and unmetamorphosed Valley and Ridge to the west. The trace of the frontal Blue Ridge, as defined by the Great Smoky fault, displays a change in strike from ~010° to ~045° in or near the Parksville 7.5-minute quadrangle in southeastern Tennessee. This change in strike defines the southern arc of the Tennessee salient, which is a convex-to-the-foreland curve in the structural front of the southern Appalachians. Along the Great Smoky fault in the Parksville quadrangle are two large horses of Lower Cambrian Chilhowee Group rocks that could have affected the emplacement of the Great Smoky thrust sheet and caused the change in strike. Detailed geologic mapping of the Parksville quadrangle has shown that the northernmost horse is comprised of a section of Nebo Sandstone thrust over a section of Cochran Formation along a previously unmapped fault, with the intervening Nichols Shale removed. The southernmost horse is comprised of Cochran Formation and displays pervasive tectonic quartz veining. Analysis of hand samples and thin sections suggest that the horses were subjected to relatively low-temperature deformational conditions between approximately 300-400°C. Intense brittle and semi-ductile to ductile deformation occurs within the immediate vicinity of the Great Smoky fault zone but is not seen elsewhere in the horses, where primarily brittle deformation is observed. The lack of penetrative brittle and ductile deformation, the constraints on deformational temperatures, and the structural orientation of the Chilhowee Group horses suggests they were derived from the hanging wall of the Great Smoky thrust sheet. The emplacement of the horses likely did not affect the development of the southern limb of the Tennessee salient. Numerous horses occur along the Great Smoky fault, but no systematic change in geometry is observed where horses occur. Instead, the curvature of the Tennessee salient was likely controlled primarily by the irregular shape of the crystalline indenter, which, in the southern Appalachians, was the Blue Ridge-Piedmont megathrust sheet.

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