In this paper coal rank trends on both sides of the Pine Mountain thrust in eastern Kentucky are used to place constraints on thrust evolution. Vitrinite reflectance () measurements on a single Pennsylvanian coal horizon (Fire Clay coal) in eastern Kentucky increase from 0.5% in the north to about 1.0% toward the SE in front of the Pine Mountain thrust. The same horizon in the hangingwall of the thrust displays lower Rmax values (0.8-0.85%). The reflectance isograds are subparallel to the thrust within approximately 10 km of the trace of the fault. We attribute thermal maturation to (1) pre-orogenic maturation by burial to a depth of about 2 km followed by (2) maturation due to conductive relaxation in the footwall after thrusting. Isotherms would not have been offset unless the thrust velocity was >> 10km / Mα. Assuming no erosion, the emergent thrust would have been approximately 3 km thick. In order to explain the relatively low reflectance values observed in the footwall, rapid uplift (>3 km/Ma) after thrust emplacement is required. Alternatively, if erosion kept pace with thrusting, the thrust sheet would have been substantially thinner (<1 >km), and thermal equilibrium would be rapidly attained in the footwall. Localized frictional heating may have caused elevated reflectance values observed in sheared coals from outcrop scale faults.

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Published in The Journal of Geology, v. 98, no. 1, p. 43-51.

© 1990 by The University of Chicago. All rights reserved.

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Work at the Center for Applied Energy Research supported by grants from the Kentucky Energy cabinet, Commonwealth of Kentucky.

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