AN UNUSUAL PYRITIZED CHARCOAL LAYER IN A COAL FROM THE PENNSYLVANIAN BREATHITT GROUP, NEAR JACKSON, KENTUCKY

The Pennsylvanian Breathitt group has numerous coals and represents a classic coal geology region. A coal in the lower part of the group exposed near Jackson, Kentucky shows an unusual pyritized texture. The section in which the coal layer is lithified is representative of numerous near coastal environments in the region. The base of the outcrop is a massive exposed sandstone bed measuring one meter in height. Above the sandstone bed there is a sharp contact, which is overlain by 1.5 meters of thinly laminated (1 mm-1.0 cm) tidal sandy siltstone, primarily grey in color but has some black shale layers interbedded within the rest of the siltstone. The siltstone is rich in muscovite. The section begins to gradationally change from thinly laminated siltstone layers into a paleosol, which is orange-yellow to brown in color. The paleosol is roughly 90 cm in height from the contact with the siltstone below it. The paleosol has a more of a clay texture than a sandy texture. The coal is positioned directly above the paleosol layer and is extended laterally throughout the section. The bottom section of the coal layer measures 15cm in thickness and has rich iron-oxide staining. The center section contains a very rare high concentration of iron sulfide replaced charcoal which is almost exclusively concentrated in the medium section of the coal layer. This lithology is approximately 5 cm thick and is characteristically very dense. This lithology has well preserved charcoal fragments that are a few mm to approximately 2.5 cm in diameter and are sub-angular to angular in shape. Samples were analyzed with a Zeiss 35VP Scanning Electron Microscope. Imaging indicates that iron sulfide fills charcoal cell interiors but does not replace cell walls. SEM imaging indicates that most of the iron sulfide appears to be individual crystals and the surfaces of the crystals are smooth, with some presence of pitting interpreted to be weathering. This unusual lithology may serve as a local marker horizon and further investigation is warranted.