BENTHIC FORAMINIFERAL COMMUNITY CHANGES ACROSS THE PLIOCENE YORKTOWN FORMATION, SOUTHEASTERN VIRGINIA

The Pliocene Yorktown Formation was deposited in a shallow marine to coastal setting along the U.S. mid-Atlantic margin at a time when global average temperatures were 2 - 3 °C higher than present, atmosphere CO₂ levels were similar to current, and sea level averaged ~25 meters higher than present. The Yorktown Formation consists of four distinct lithologic units, the Sunken Meadows Member, which corresponds to the Zanclean Stage, and the Rushmere, Morgarts Beach and Moore House Members all assigned to the Piacenzian Stage. These members record three marine transgressive sequences. The transition between Marine Isotope Stages (MIS) M2 and M1 (~3.30-3.24 Ma), the largest cool to warm transition during the Piacenzian, is preserved in the Rushmere and Morgarts Beach sediments. Thirty-three samples were collected from three replicate sequences at the lectotype section of the Yorktown Formation, along the James River near Rushmere, Virginia. We are analyzing samples for sedimentology and benthic foraminifer community changes within each member, as well as between the members. Our assemblage data are compared to a high resolution alkenone record to establish age control and to contrast changes in sea surface temperature and productivity with changes within the foraminifer communities. This study will advance the understanding of foraminiferal community changes in shallow marine environments in response to warming and sea level rise.