Late-glacial to Holocene climate variability and drought in the mid-Hudson Valley region of New York state

Sediment cores from Lakes Minnewaska and Mohonk in the Shawangunk Mountains of southeastern New York were analyzed for pollen, plant macrofossils, macroscopic charcoal, organic carbon content, carbon isotopic composition, carbon/nitrogen ratio, and lithologic changes to determine the vegetation and landscape history of the mid-Hudson Valley region since deglaciation. Pollen stratigraphy generally matches the New England pollen zones identified by Deevey (1939) and Davis (1969), with boreal genera (Picea, Abies) present during the late Pleistocene yielding to a mixed Pinus, Quercus and Tsuga forest in the early Holocene. Lake Minnewaska sediments record the Younger Dryas and possibly the 8.2 cal kyr BP climatic events in pollen and sediment chemistry along with an ~1100 cal yr interval of wet conditions (increasing Tsuga and declining Quercus) centered about 6400 cal yr BP (5600 14C yrs BP). Mohonk Lake reveals a protracted drought interval in the middle Holocene ~5900-4700 cal yr BP (~4900-3900 14C yrs BP), during which Pinus rigida colonized the watershed, lake level fell, and frequent fires led to enhanced hillslope erosion. Together, the records show at least three wet-dry cycles throughout the Holocene and both similarities and differences to records in New England and western New York. Drought intervals may reflect a combination of enhanced La Niña, negative phase NAO, and positive phase PNA climatic patterns and/or northward shifts of storm tracks. AMS radiocarbon dates determined at the onset of organic deposition in each lake contribute to the ongoing development of the Laurentide deglaciation chronology in the region.