CRETACEOUS AND PLIOCENE MICROFOSSILS FROM GREENS MILL RUN, NORTH CAROLINA, USA

Cretaceous sediments are disconformably overlain by Pliocene sediments along the banks of Greens Mill Run, Greenville, North Carolina. Greens Mill Run is a tributary of the Tar River, located in the central coastal plain of North Carolina and underlain by a structural low referred to as the Albemarle Embayment. The Cretaceous unit, composed of glauconitic sand, has been considered part of the Maastrichtian Peedee Formation. The Pliocene sediments belong to two members of the Yorktown Formation: The Rushmere Member (shelly sand) overlain by the Morgarts Beach Member (shell-poor, sandy mud). We document the foraminifera of these outcrops for the first time and, using calcareous nannofossils, show that the Cretaceous sediments belong to the upper Campanian Donoho Creek Formation.

Eleven sediment samples were collected along Greens Mill Run, two from the Cretaceous unit and nine from the Yorktown Formation. Preliminary results indicate the presence of abundant foraminifera in the Cretaceous unit; planktonic foraminifera dominate. Benthic foraminifera dominate the Pliocene Rushmere Member; the Morgarts Beach Member, characterized by abundant molds of bivalves, is barren of foraminifera. The foraminiferal assemblage of the Rushmere Member is similar to assemblages in correlative strata in the southern Albemarle Embayment - for example, Hanzawaia concentrica is present suggesting deposition in a middle to outer neritic environment. This species is absent from the type section of the Rushmere Member in the Salisbury Embayment to the north, suggesting a shallower neritic environment.

The age of the Cretaceous unit is late Campanian (Zone CC22c), as indicated by the co-occurrence of the calcareous nannofossils Reinhardtites levis and Reinhardtites anthophorus. Thus, these deposits are assigned to the Donoho Creek Formation of the Black Creek Group rather than to the lithologically similar and younger Peedee Formation.