DACRYOCONARID FAUNAS OF THE BASAL EIFELIAN-TO-CHOTEC BIOEVENT INTERVAL IN THE NORTH AND CENTRAL APPALACHIAN BASIN

In the northern and central Appalachian Basin, the Edgecliff and Nedrow members (Onondaga Fm.) and equivalent lower two divisions of the Selinsgrove Member (Needmore Fm.) record an interval that extends from the base of the Eifelian stage through the global Chotec bioevent; dacryoconarid faunas progressively diversify within the T-R Cycle Ic transgressive systems tract only to abruptly collapse and be succeeded by new forms at the maximum flooding surface of that cycle. The lower Edgecliff (Clarence facies) fauna includes the lowermost known occurrences of a distinctive form of Viriatellina with 16-20 costae on a semi-circumference, as well as one type of Striatostyliolina, two forms of Costulatostyliolina, and the tentaculitid Tentaculites scalariformis. This fauna diversifies near the top of the Edgecliff through the addition of a second form of Striatostyliolina, a third Costulatostyliolina varient, and a form of Styliolina that is distinct from the supposedly ubiquitous S. fissurella. Tentaculites scalariformis becomes notably abundant in the lower Nedrow beds where the dacryoconarids further diversify through the addition of a second form of Viriatellina and a third type of Costulatostyliolina. This fauna does not carry over into the Chotec equivalent black beds at the top of Nedrow, which contain an entirely new set of Viriatellina and Costulatostyliolina, as well as the lowermost currently known occurrence of Metastyliolina in the Appalachian Basin.