ENVIRONMENTAL AFFINITIES AND DISTRIBUTION OF FOSSIL TAXA IN THE TACONIC FORELAND BASIN, TENNESSEE TO PENNSYLVANIA, USA

Environmental affinities and distributions of fossil taxa are key to understanding the processes that drive clade evolution and are also essential for understanding basin evolution. We investigated the environmental affinities and distributions of fossil taxa in the Late Ordovician Taconic foreland basin from Tennessee to Virginia. Our dataset consists primarily of Bretsky’s (1970) classic study plus new collections from central Pennsylvania. We performed cluster analysis and non-metric multidimensional scaling to identify environmental gradients in the foreland basin. Interpretation of multivariate analyses reveal a primary environmental gradient related to depth, and a secondary gradient related to carbonate content. The depth gradient is characterized from shallow to deep by the abundance of Lingula, bivalves, Rafinesquina, Onniella, Sowerbyella and is consistent with the interpretations of Springer and Bambach (1985). Along the axis of the Taconic foreland basin from Pennsylvania to Tennessee the basin shallows and also transitions to a mixed siliciclastic-carbonate ramp. The mixed siliciclastic-carbonate assemblages are characterized by Zygospira, Hebertella, bryozoans, and bivalves. Overall, the environmental distribution of taxa reflects the topography of the Taconic foreland basin with the center of subsidence and siliciclastic input in Pennsylvania. Our new sites in Pennsylvania that contain ophiuroids and conularids suggest these taxa preferred deep subtidal, siliciclastic environments generally below storm wavebase.