Late Pliocene and Early Pleistocene Mollusca from the James City and Chowan River Formations at the Lee Creek Mine

Abstract

A molluscan fauna consisting of 194 species is described from the Chowan River (upper Pliocene) and James City (lower Pleistocene) formations at the Lee Creek Mine, Aurora, North Carolina. These two formations are as much as 7 m thick in the mine and unconformably overlie strata that correlate with the Yorktown Formation in its type area. The Chowan River and James City formations are separated by an unconformity. The mollusks of the Chowan River Formation are assigned to the <i>Glycymeris hummi-Turritella perexilis</i> assemblage-zone and the mollusks in the overlying James City Formation are assigned to the <i>Marvacrassatella kauffmani-Astarte berryi</i> assemblage-zone. Although mollusks in these zones lived in a subtropical thermal regime, they include some warm-temperate species not found in contemporaneous deposits farther south. The units represented by these assemblage zones were deposited mostly under open marine conditions at a maximum depth of about 25 m. The <i>Marvacrassatella kauffmani-Astarte berryi</i> assemblage at Lee Creek lived in association with an offshore bar system, which has some large unidirectional current-bedded shelly sands. Although more than 65 percent of the species in the assemblages are now extinct, the composition and diversity of the mollusks in the different beds is very similar to that of the <i>Argopecten gibbus</i> community presently living off the North Carolina coast.