Benthic Foraminiferal and Sedimentologic Changes in the Pliocene Yorktown Formation, Virginia, USA

Abstract

ABSTRACT The Pliocene Yorktown Formation consists of four lithologic units that record three marine transgressive sequences along the U.S. mid-Atlantic margin. These units were deposited during a time when average sea-level and mean global temperatures were ∼25 m and ∼3°C higher than the pre-industrial, respectively, and global atmospheric CO2 concentrations were similar to present. Forty-five samples were collected along the James River near Rushmere, Virginia, and Spring Grove, Virginia, and were analyzed for benthic foraminifera community and sedimentological changes between each member of the formation. These data are useful for developing boundary conditions for shallow, near-shore environments for paleoclimate modeling. Foraminiferal analysis distinguishes six biofacies across the entire formation. The most notable change in grain-size occurs at the conformable boundary between the Rushmere and Morgarts Beach members, where the average percentage of sand decreases from ∼60% in the Rushmere Member to <40% in the Morgarts Beach Member.