SEDIMENTOLOGICAL EXAMINATION OF LITHOFACIES ASSOCIATED WITH COAL SEAMS OF THE LINTON AND PETERSBURG FORMATIONS (PENNSYLVANIAN) IN VANDERBURGH COUNTY, INDIANA: IMPLICATIONS FOR COAL FORMATION AND ORIGINS OF COAL-BED METHANE

Four intervals of core were collected from the Linton and Petersburg formations (Pennsylvanian) from an exploration well drilled on the campus of the University of Southern Indiana. The well is part of an economic and geologic assessment that examined potential for Coal-Bed Methane (CBM) production. These cores contain, in stratigraphic succession, the Seelyville, Survant, Houchin Creek, and Springfield coals. The purpose of this research is to complete a sedimentological study of the bedding, sedimentary structures, and fossil content of lithofacies above and below these coal seams to assess coal formation and potential origins of CBM.

The Seelyville coal was cored from 668 to 664 feet. This coal is underlain by a grey to tan mudrock with 1-cm diameter siderite concretions and overlain by light grey, laminated mudrock with 1-cm siderite concretions. The Survant coal was cored from 558 to 556 feet. This coal is underlain by 15-cm of organic-rich shale capping a well sorted, mica-bearing, quartz arenite and overlain by grey, laminated mudrock with 2-cm diameter siderite concretions. The Houchin Creek coal was cored from 505 to 507 feet. The Houchin Creek coal is underlain by ripple cross-laminated to flaser bedded sandstones grading upward into irregular bedded, green-grey, silty sandstones with concretions and overlain by black, organic-rich, laminated mudrock. The Springfield coal was cored from 414 to 410 feet. This coal is underlain by light grey, marcasite-bearing, mudrock and overlain by black, organic-rich, laminated mudrock with disseminated marcasite and bands of 1-cm diameter siderite concretions grading upward over two feet into a laminated mudrock containing abundant Lingula carbonaria and ostracodes.

The lithofacies associated with coal seams in these formations attest to varying paleoenvironmental conditions prior to and after coal formation. In all four intervals, coals are capped by laminated mudrock, with marine fauna present above the Houchin Creek and Springfield coals. The lithofacies below the four coals vary from laminated mudrock to tidally influenced sandstones. This suggests the existence of variable depositional environments prior to coal formation, but preservation by marine flooding. The varying lithofacies below these coal seams may impact the potential for CBM.