Sulfur variability and petrology of the Lower Block Coal Member (Pennsylvanian) in Southwest Indiana

The Lower Block Coal Member (Pennsylvanian-Atokan, Westphalian C) is an eco nomic low-to medium-sulfur, low-ash coal resource in the Illinois Basin. Su lfur content is generally low (averaging 1.0%) in the study area, but varie s over short distances. Higher sulfur areas occur as isolated pods and epig enetic pyrite increases significantly in the upper third of the selected co lumns in higher sulfur areas. Sulfur variations cannot be predicted by typi cal geologic characteristics such as roof lithology, seam thickness, or sea m elevation. Petrographic analysis shows that pyrite is generally associate d with brighter microlithotypes, except in higher sulfur areas where infill ing pyrite forms are associated with inertite. Higher sulfur areas reflect the water chemistry of the paleomire during and shortly after peat accumula tion. Locally, abundant pyrofusinite provided additional pore space for pyr ite precipitation. (C) 1999 Elsevier Science B.V. All rights reserved.