NO SIGNIFICANT CHANGES IN MICROBIVALVE AND OSTRACODE DIVERSITY OR ON PREDATION BY GASTROPODS ACROSS PLIOCENE-PLEISTOCENE BOUNDARY IN SOUTHEASTERN NORTH CAROLINA

The Pliocene-Pleistocene boundary in the Atlantic Coastal Plain of North America is characterized by a significant extinction of mollusks, including a decrease in predatory gastropods that feed on bivalves by boring through the shell. Microbivalves and ostracodes were collected from five localities that span the Pliocene-Pleistocene boundary in southeastern North Carolina: Natural Well and Tar Heel from the late Pliocene (3.0 Ma) Duplin Formation, Acme and Register Quarry from the early Pleistocene (2.0-1.8 Ma) lower Waccamaw Formation, and Walker’s Bluff from the mid Pleistocene (1.5 Ma) upper Waccamaw Formation. Species of microbivalves and ostracodes were identified, diversity of microbivalves and ostracodes were calculated, and the number of bored valves determined. Ostracode diversity (Simpson Diversity Coefficient) ranged from 3.4 to 6.8, with perhaps an increase in the Pleistocene; microbivalve diversity ranged from 4.0 to 12.1, with the significant increase in the mid Pleistocene at Walker’s Bluff. There was no consistent change in diversity of the microfauna from the Pliocene to Pleistocene samples as compared to macrofauna. Borings by predatory gastropods was higher in microbivalves, up to 24% of valves were bored at Register Quarry, but percent of valves bored varied between localities independent of the Pliocene- Pleistocene boundary, suggesting that facies and preservation need to be considered in evaluation of changes across the boundary.

Additional authors: Over, D. Jeffrey, SUNY-Geneseo and Dietl, Gregory, PRI-MOTE, Trumansburg, NY