HESTER, NORMAN C., Indiana Geological Survey, Bloomington, IN

If reliable models for peat-forming environments can be developed, the coal mining industry will be better prepared to predict areas where the best-quality coals occur and where the potential for problems with roof control exist. Because lithologies of the roof rock vary with depositional settings, improved methods for recognizing and coding the various lithologies and facies of the rock core will contribute significantly to the mine-planning process.
An analysis of facies and stratigraphic relationships of the Springfield Coal Member of the Petersburg Formation (Pennsylvanian) and encasing facies in the Illinois Basin indicate the existence of a lowland river valley (Galatia paleochannel) that was penecontemporaneous with paleosol which underlies the Springfield coal. This channel was inundated and converted to a fluvio-estuarine system by a rising sea level that buried the fringing peat marsh with rhythmic-bedded fine-grained siliciclastics. Rapid sedimentation resulting from tidal-driven processes preserved the low-sulfur quality of the peat but also contributes to unstable roof conditions. More work needs to be performed using mine data from areas associated with the Galatia paleochannel and fill. It appears, however, that by using a model based on transgression and tidally driven sedimentation, the distribution of the quality of coal and roof rock lithologies can be predicted. Applying this model, coupled with the use of the Corebook of Pennsylvanian Rocks in the Illinois Basin, should provide valuable assistance to coal mining geologists and mining engineers for mine planning throughout the Illinois Basin.

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