Constraints on the emplacement and uplift history of the Pine Mountain thrust sheet, eastern Kentucky: evidence from coal rank trends

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 (%R_max) measurements on a single Pennsylvanian coal horizon (Fire Clay coal) in eastern Kentucky increase from 0.5% in the north to ~1.0% toward the SE in front of the Pine Mountain thrust. The same horizon in the hangingwall of the thrust displays lower R_max values (0.8-0.85%). Assuming no erosion, the emergent thrust would have been ~3km thick. In order to explain the relatively low reflectance values observed in the footwall, rapid uplift (>3km/Ma) after thrust emplacment is required. Alternatively, if erosion kept pace with thrusting, the thrust sheet would have been substantially thinner (<1km), and thermal equilibrium would be rapidly attained in the footwall. -from Authors