MACROFOSSIL EVIDENCE FOR MIDDLE TO LATE HOLOCENE VEGETATION SHIFTS AT IONA ISLAND MARSH, HUDSON RIVER ESTUARY, NY

With their geographic location and hydrologic connection between the ocean and continent, estuaries reflect the environmental change of both. Using 202 macrofossil samples and 198 loss-on-ignition samples spanning a 900 cm sediment core, a high resolution paleoenvironmental record is constructed for the brackish tidal Iona Island Marsh of the Hudson River National Estuarine Research Reserve (HNERR). Seven macrofossil samples were dated using accelerator mass spectrometry (AMS) radiocarbon, and a sedimentation rate graph reveals shifts in accumulation rates over time. The sediment core contains 6 distinct paleoecological zones with a basal date of 4384 BCE. Shifts in climate, including the Medieval Warm Interval at 800 to 1300 CE, are inferred from changes in plant species composition. Results are interpreted along with previous palynological work from the study site and data from other Hudson River estuarine and regional studies.