CALIBRATION OF VERTEBRATE FAUNAL REMAINS AS AN ADDITIONAL TOOL TO PROVIDE A TEMPORAL FRAMEWORK FOR THE TIMING OF DEGLACIATION IN NEW YORK STATE AFTER THE LAST GLACIAL MAXIMUM

Precisely determining the temporal chronology of deglaciation has clear implications for Quaternary geology, but can also inform how and when species assemble within new environments. Unfortunately, obtaining a precise chronology is not always possible depending on the location and materials preserved. Here, we present a methodology to use dated vertebrate fauna as a tool to provide a conservative chronological framework for determining the initiation of deglaciation in New York State (NYS). At the Last Glacial Maximum, nearly all of NYS was covered by the Laurentide Ice Sheet (LIS), and subsequent recession, the result of global warming, opened the landscape for colonization by flora and fauna. To determine the timing of deglaciation we examine dated mammalian megafauna. Within this study, we generated and analyzed over 40 AMS radiocarbon dates from the most abundant and wide-spread mammalian megafaunal species within NYS including, caribou (Rangifer tarandus), mammoth (Mammuthus sp.), and mastodon (Mammut americanum). Preparation of samples followed standard techniques and analyses were performed at the National Ocean Sciences AMS (NOSAMS) facility at Woods Hole, MA. Because of taphonomy, the earliest or latest occurrence of a fossil likely does not represent the earliest or latest occurring individual from an ancient population. In order to calibrate the timing of earliest and latest occurrences for the analyzed megafauna, we used two methodologies including a Bayesian calibration of radiocarbon dates as well as a more recently developed sighting method–based technique called the Gaussian resampled inversely weighted McInerney et al. (GRIWM) methodology. The results from both techniques were consistent, and showed that megafauna first colonize NYS after about 18ka and are extirpated near the end of the Pleistocene. These results show that dated vertebrate remains can be utilized as an additional tool to calculate the timing of glacial events, such as the initiation of deglaciation in particular regions.