USING OSTRACODA AND FORAMINIFERA FOR PALEOENVIRONMENTAL ANALYSIS OF THE DUPLIN (PLIOCENE) AND WACCAMAW (PLEISTOCENE) FORMATIONS IN NORTH CAROLINA

Fossil-rich deposits in North Carolina provide an opportunity to examine extinction events in western Atlantic molluscs during the Plio-Pleistocene. When comparing assemblages from different formations and localities, paleoenvironments must be well-constrained as paleoecological analyses should be restricted to fauna from similar habitats. In this study, foraminifers and ostracods are used for paleoenvironmental reconstruction of units analyzed for molluscan diversity as part of a multiyear REU at UNCW.

Bulk samples were collected from three localities and processed for microfossils. The first locality in Tar Heel, NC, consists of the Duplin Formation. Localities at Acme, NC, and Holloman Pit in Whiteville, NC, represent the lower Waccamaw Formation. McGregor et al. (2011) dated the Duplin at Tar Heel as ~3.34Ma (late Pliocene, Piacenzian) and the lower Waccamaw at Acme as ~1.97Ma (early Pleistocene, Gelasian). Three hundred foraminifers and ostracods each were picked from these three samples and identified to genus.

Foraminifers include Rotaliina, Miliolina, Textulariina, Lagenina, Spirillinina, and Globigerinina. The Duplin sample is composed nearly entirely of the foraminifer Amphistegina; lower Waccamaw samples are dominated primarily by Amphistegina and Quinqueloculina. The most abundant ostracod in the Duplin sample is Aurila conradi conradi. This species makes up a large proportion of lower Waccamaw ostracods from Holloman Pit and Acme as well, but Mutilus confragosa is slightly more abundant at Acme.

Previous work by other REU students on microfossils from these units yielded similar results. Parnell et al. (2009) found the ostracods Aurila conradi conradi and Mutilus confragosa were common in the Duplin Fm on the Lumber River at Lumberton, NC, and lower Waccamaw Fm of Register Quarry near Old Dock, NC. Borges-Farfan et al. (2010) noted abundant Amphistegina foraminifers in the lower Waccamaw Fm on the Waccamaw River near Tilly Lake, SC. These results correspond well with our ongoing work and examination of microfossils from additional Plio-Pleistocene localities in NC and SC is planned. Thus far, genera indicate warm, shallow, normal marine, inner to middle shelf environments, in part based on the literature of microfossils from these units in the Carolinas (e.g., Swain, 1968; Howard, 1974).