PALEOENVIRONMENTS OF THE DUPLIN (PLIOCENE) AND WACCAMAW (PLIO-PLEISTOCENE?) FORMATIONS IN SOUTHEASTERN NORTH CAROLINA INFERRED FROM MICROFOSSILS

The Plio-Pleistocene was a time of faunal decimation in the western Atlantic, but the causes, timing, and magnitude of extinction and the extent of the recovery are poorly understood in the Carolinas. In comparing macrofaunal assemblages during this time, it is necessary to investigate any fluctuations in paleoenvironments. Microfossils such as ostracods and foraminifers can be helpful in reconstructing paleoenvironments.

Bulk samples were collected from the Pliocene Duplin Formation on the Lumber River near Lumberton, NC, and from the Waccamaw Formation at Register Quarry near Old Dock, NC (following a late Pliocene phase of faunal turnover). In total, 900 ostracodes were picked for paleoenvironmental analysis, 300 from the Duplin and 300 from each of two beds of the lower Waccamaw at Register Quarry. Previous work by Howard (1974) suggests that Duplin microfauna should indicate an intermediate to inner-shelfal environment; Waccamaw microfossils should represent brackish to open-marine environments. Ostracod genera previously documented in these assemblages include Aurila, Brachycythere, Cushmanidea, Cytherura, Hulingsina, Murrayina, and Paracytheridea. Expected foraminifers comprise Ammonia, Amphistegina, Angulogerina, Cassidulina, Cibicides, Elphidium, Globigerina, Hanzawaia, Ruessella, and Rosalina (Howard, 1974).

Sorting of ostracods is in progress, but the most common species in each sample is Aurila conradi conradi. Other identified species include Haplocytheridea bradyi, Mutilus confragosa, Neocaudites triplistriata, and Paracytheridea vandenboldi. Preliminary work on foraminifers indicates the presence of globigerinids, miliolids, and textulariids. Howard (1974) distinguished 3 biofacies in both the Duplin and Waccamaw formations; future work shall compare the composition of microfossils in our samples to these biofacies. The results should aid in understanding Plio-Pleistocene extinctions by constraining paleoenvironmental variation.