Dynamic lithostratigraphy and paleecology of upper Mississippi (Chesterian) strata of the northcentral Appalachian Basin

Chesterian strata of the northcentral Appalachians consist of intertonguing marine carbonates and paralic to terrestrial clastics. The basal unit, the Loyalhanna, rests unconformably upon lower Mississippian Pocono sandstones and accumulated under conditions of episodic sea level transgression. The Loyalhanna, in most places is a festoon cross-bedded, sandy lime grainstone, but a nearshore interbedded carbonate-shale facies is also recognized. Minor oscillations in sea level resulted in a vertical repetition of marine and nonmarine rocks after which a major episodic marine transgression began which resulted in the deposition of the Wymps Gap Limestone. Two facies of the Wymps Gap developed; a calcareous sandstone and thinly interbedded wackestone and shale. Topographic relief created by a thick lobe of underlying clastics resulted in the formation of a local carbonate platform along the edge of which developed a carbonate sand shoal, containing grainstone.