PALEOECOLOGY OF ZIPFELDBERG BOG, SOUTHEASTERN NEW YORK, AND IMPLICATIONS FOR LATE PLEISTOCENE AND HOLOCENE HYDROLOGICAL CHANGES DRIVEN BY CLIMATE

A 9.82-m-long sediment core from Zipfeldberg Bog near Rhinebeck, New York was analyzed for organic matter, pollen, plant macrofossils, and charcoal to reconstruct vegetation and climate history since the retreat of the Laurentide ice sheet. The 1.6 ha Sphagnum-dominated bog overlies limestones of the Cambrian Germantown formation, making its acidic pH unusual and suggesting that it might be a sensitive recorder of climatologically controlled hydrologic variability. The site also contains several rare plant species, making a detailed history important for conservation. Preliminary results of the investigation reveal the typical Northeastern US pollen zones first identified by Deevey (1939), including high percentages of boreal conifers (Picea, Abies) near the base of the core, Younger Dryas-related increases in Alnus and Betula pollen, and an early Holocene peak in Pinus, followed by increases in deciduous species that signify the onset of Holocene warmth (e.g., Quercus). Basal sediments of gyttja are underlain by clay, revealing a limnic environment with earliest organic sediments containing Picea macrofossils radiocarbon dated at 14,256 +/- 315 ka at 9.65 m depth. Oogonia of Chara are present in the gyttja, indicating an alkaline environment. Sphagnum rises in abundance at 6.3 m, coinciding with a decline in Pinus and a rise in Fagus and Carya pollen that we tentatively suggest occurred at ~8.5 ka based on nearby records. The well-recognized mid-Holocene Tsuga decline, which appears at 4.4 m depth and is tentatively dated to ~5.25 ka based on regional correlation, coincides with more alkaline conditions, evidenced by the re-appearance of oogonia of Chara and declines in Sphagnum, and with less moisture, shown by the presence of Scirpus followed by Dulichium arundinaceum seeds at the site. Despite lower moisture, charcoal is no more abundant during this period in the Zipfeldberg Bog record than prior to or after the Tsuga decline. Subsequent increases in Sphagnum, commencing with Tsuga recovery and continuing up to the present, indicate moisture increases in the late Holocene.