The control of coal bed decollement-related slickensides on roof falls in North American Late Paleozoic coal basins

Abstract

Slickensides cause potentially hazardous ground conditions in underground coal mines. Investigations by the Mine Safety and Health Administration's (MSHA) Roof Control Division indicate that many slickensides represent bedding plane faults and drag folds that formed during coal bed decollement, a style of bedding plane faulting that occurs in shale units above coal seams. These slickensides formed in response to regional tectonic stresses, rather than by differential compaction, and strike parallel to local and regional fold axes and thrust faults. This paper relates some slickensides in the Appalachian, Illinois, Arkoma, and Black Warrior basins to the structural grain developed during the Late Pennsylvanian–Permian Alleghanian orogeny, provides descriptions of slickensides, and advocates geologic mapping as a predictive method for identifying adverse ground conditions associated with tectonically formed slickensides.