| Assessments of global Pliocene climate using conventional proxies indicate prevalent warmth at mid to high latitudes. However, it remains poorly understood how these climate changes were manifested on a regional basis and on annual timescales. Oxygen isotope ratios (delta18O) of fossil Mercenaria spp. (bivalve) shells enable reconstruction of growth temperature to estimate sea surface temperature (SST) at seasonal resolution, and comparing growth characteristics of fossil and modern populations can provide independent SST estimates. Fossil shells selected from the Yorktown Formation (Pliocene, early Piacenzian, ∼3.3-3.0 Ma, warm interval) and the Chowan River Formation (Pleistocene, Gelasian, 2.4-1.8 Ma, subsequent cooling) of the US Mid Atlantic Coastal Plain document warmth and reduced seasonality relative to modern. Growth analyses of fossil populations likely exclude the possibility of more extreme (>25°C) average annual conditions. These results support model results of increased meridional heat transport during the Pliocene. |
