Biostratigraphy of crinoids from the Wymps Gap member of the Greenbrier Formation (Mississippian, Chesterian) in northern West Virginia

Abstract

Crowns of four crinoid species, Talarocrinus planus Weller, 1920, Phacelocrinus longidactylus (McChesney, 1860), Ampelocrinus mundus? Kirk, 1942, and Phanocrinus maniformis (Yandell and Shumard, 1847) are reported from the limestones of the Wymps Gap Member of the Greenbrier Formation in northern West Virginia. Collectively these species indicate an early Chesterian age for the Wymps Gap Member, with the occurrence of T. planus indicating correlation with the Ridenhower (Paint Creek) Formation of the Illinois Basin. A review of the 17 species currently placed in Talarocrinus suggests that the Talarocrinus zone ranges no higher than the Ridenhower Formation in the Upper Gnathodus bilineatus conodont zone of the late Visean. The new occurrence of A. mundus extends its range upwards from the Genevievian substage of the Chesterian. Previous studies have used sequence stratigraphy to correlate the Wymps Gap Member with the lower part of the Union Limestone Formation of the Greenbrier Group in southern West Virginia, which in turn has been correlated with the Ridenhower Formation. The occurrence of T. planus in the Wymps Gap Member provides independent confirmation of the correlations based on sequence stratigraphy between the Appalachian and Illinois basins. Correlation of the overlying Reynolds Member of the Mauch Chunk Formation with the Glen Dean Formation of the Illinois Basin suggests a significant unconformity between the Greenbrier Formation and Mauch Chunk Formation in northern West Virginia.