PETROLOGY AND DIAGENESIS OF THE RAINES CORNER LIMESTONE MEMBER OF THE BLUEFIELD FORMATION, SOUTHEASTERN WEST VIRGINIA

The Raines Corner Limestone is the basal unit of one of the transgressive-regressive cycles that makes up the Bluefield Formation in the central Appalachian Basin. Raines Corner outcrops in Monroe County, WV, are about 3 meters thick. The unit consists of stacked meter-scale fining-upwards/ shallowing-upwards cycles of mixed carbonate-siliciclastic sediment. The lower part of each cycle is a skeletal wackestone with a typical shallow marine assemblage of bivalves, brachiopods, gastropods, bryozoans, echinoderms, foraminifers and ostracodes in a matrix of carbonate and terrigenous mud. The upper part is a laminated mudstone (carbonate and terrigenous mud) with a sparse fauna of smaller size and lower diversity. The percentage of terrigenous material is greater in cycles higher in the section. Deposition of the Raines Corner Limestone was in a nearshore environment where terrigenous sediment influx and carbonate production were nearly equivalent. Diagenesis of the Raines Corner Limestone includes cementation of the sediment by both sparry calcite and micrite, infilling of porosity by granular to blocky spar, recrystallization of bioclasts, minor dolomitization, formation of stylolites and solution seams, and fracturing and subsequent infilling by carbonate.