SCLEROCHRONOLOGIC AND PALEOENVRIONMENTAL RECORDS IN MARINE BIVALVES FROM THE DUPLIN FORMATION, NORTH CAROLINA

Existing studies of Pliocene micro- and macrofossil assemblages along the eastern North American coast (Pinecrest, Duplin, and Yorktown Formations) suggest that during the Mid-Pliocene Warm Period (3.29-2.97 Ma) a more vigorous Florida Current, relative to today, facilitated a northward extension of subtropical fauna past the modern biogeographic boundary of Cape Hatteras (Ward et al., 1991; Williams et al., 2009). Evidence supporting this interpretation also includes high-resolution isotope and growth records from marine bivalves capable of (Krantz, 1990; Jones and Allmon, 1995; Goewert and Surge, 2007) and climate model reconstructions for the Early and Mid-Pliocene (Williams et al., 2009). Published estimates from the Lower Pinecrest (Florida) and Yorktown (Virginia) members indicate warmer waters and reduced seasonality, relative to modern instrumental records. However, molluscan temperature estimates from the Duplin Formation (Carolinas) remain uninvestigated.

This study presents growth increment and geochemical sclerochronological data from three marine bivalves, Carolinapecten eboreus, Glycymeris americana, and Mercenaria campechiensis, collected from the Duplin Formation along the Lumber River in southeastern North Carolina. The objectives of this study are and test the hypothesis that: (1) shells from the Duplin Formation recorded higher seawater temperature relative to today; and (2) to fill in a sclerochronologic data gap along the eastern North Atlantic . Preliminary results from Duplin shells show animals experienced growth rates and annual temperature ranges greater than and warmer than those in modern conditions, consistent with Yorktown bivalves, faunal assemblages and model interpretations. A larger validation using stable isotopes, along with a multi-species, multi-proxy comparison will soon provide better estimates of regional seasonality during the Mid-Pliocene Warm Period.