RECONSTRUCTING THE LATE PLEISTOCENE PALEOENVIRONMENT AND POPULATION ECOLOGY OF THE EASTERN OYSTER (CRASSOSTREA VIRGINICA) AT HOLLAND POINT, VIRGINIA
The deposit is divided into a larger, eastern section (17 meters long with a maximum height of 2.47 meters) and a smaller, western section (8 meters long with a maximum height of 2.04 meters). Fifteen bulk samples were collected along horizontal and vertical transects. Ages of the oysters were determined through two methods: counting the number of growth lines in the cross-section of the oyster hinge and counting the number of bumps on the hinges (“bump counting”). Preliminary data suggest that Pleistocene oyster populations had much higher concentrations of spat and juvenile oysters (x̄=31.4mm) and much higher population densities (x̄=6,212 oysters/m2) than modern reefs (300-500 oyster/m2). Calculated growth rates for the Pleistocene oysters were slower (x̄= 20.26 mm/yr) than the growth rates of the modern (x̄=21.6 mm/yr), but the difference was not statistically significant.
Amino acid racemization was applied to multiple specimens of Crassostrea and Mercenaria, yielding estimates ranging from 80-120 ky for this deposit. We attempted to reconstruct paleotidal current direction by comparing the orientation measurements of articulated oysters preserved in the reef, but no major trends were revealed. Salinity tolerances of 21 non-oyster species suggest a higher salinity environment (15 to 32 ppt) than the modern Piankatank River (6 to 23 ppt). Clumped isotope thermometry of Mercenaria specimens support a warmer environment than the modern temperature range. These factors suggest a more estuarine environment for the Pleistocene Holland Point reef than its current position on the modern Piankatank River.