Chironomid and pollen evidence for climate fluctuations during the Last Glacial Termination in NW Patagonia

We present chironomid and pollen records from the Huelmo site (similar to 41 degrees 30'S), NW Patagonia, to examine in detail the timing and structure of climate changes during the Last Glacial Termination in the southern mid-latitudes. The chironomid record has the highest temporal and taxonomic resolution for this critical interval, and constitutes the first account of midge faunas at the culmination of the Last Glacial Maximum (LGM) for the region. The chironomid record suggests cold and wet conditions during the LGM, followed by deglacial warming between 17.6 and 16.8 cal kyr BR Relatively warm conditions prevailed between similar to 15-14 Cal kyr BR followed by a reversal in trend with cooling pulses at similar to 14 and 13.5 Cal kyr BP, and warming at the beginning of the Holocene. Cool-temperate conditions prevailed during the Huelmo Mascardi Cold Reversal (HMCR) which, according to chironomid data, exhibits a wet phase (13.5-12.8 cal kyr BP) followed by a conspicuous drier phase (12.8-11.5 cal kyr BP). The chironomid and pollen records from the Huelmo site indicate step-wise deglacial warming beginning at 17.6 cal kyr BP, in agreement with other paleoclimate records from NW Patagonia and isotopic signals from Antarctic ice cores. Peak warmth during the Last Glacial Termination was achieved by similar to 14.5 Cal kyr BP, followed by a cooling trend that commenced during the Antarctic Cold Reversal, which later intensified and persisted during the HMCR (13.5-11.5 cal kyr BP). We observe a shift toward drier conditions at similar to 12.8 cal kyr BP superimposed upon the HMCR, coeval with intense fire activity and vegetation disturbance during Younger Dryas time. (C) 2008 Elsevier Ltd. All rights reserved.