Seasonal-Scale Paleoclimate Reconstruction of the Mid-Pliocene Warm Period Using High-Resolution Stable Isotope, Trace Element, and Clumped-Isotope Analysis of Fossil Molluscan Carbonate from the Yorktown Formation, Virginia

Abstract

The mid-Pliocene Warm Period (mPWP) is an interval in Earth’s climatic history characterized by warm conditions and atmospheric CO2 concentrations comparable to the present. Because of this, the mPWP offers a critical analogue for understanding future global warming. This study examines the paleoclimate of the mPWP on a seasonal-scale by employing high resolution isotopic and trace element analysis of the marine bivalve Mercenaria from the mid-Pliocene age Yorktown Formation in Virginia. δ18O and δ13C records show seasonal variation and act as a proxy for past sea surface temperatures. A reduction in seasonal temperature variations is observed in the mPWP (10.6°C) compared to present (21.1°C), accounted for by warmer winter and cooler summer conditions. Further analysis of trace elements (Sr/Ca, Mg/Ca, Ba/Ca, Mn/Ca, Fe/Ca, and Zn/Ca) provide additional constraints on paleoenvironmental reconstructions and suggest the potential influence of upwelling. Preliminary clumped-isotope analyses contrast with the upwelling hypothesis and are suggestive of riverine input of freshwater. Future work will continue to make use of clumped isotope analysis to better constrain paleotemperatures and δ18O𝑠w values for the mid-Pliocene.