REVERSAL OF THE LATE YOUNGER DRYAS WARMING TREND INDICATED BY TREE RINGS AND STABLE ISOTOPES IN THE EASTERN LAKE ONTARIO LOWLANDS, NEW YORK STATE

Spruce wood found in Bell Creek on the lowlands south of eastern Lake Ontario date from the late Younger Dryas (YD) into the early Holocene (~12,100-11,300 cal yr BP) following the drainage of glacial Lake Iroquois. A tree-ring chronology using 15 spruce trees was built that spans 284 years, but the flatness of the radiocarbon calibration curve in the late YD makes it very difficult to place the chronology accurately in time and determine if the chronology spans the YD-Holocene transition. The ¹³C and ¹⁸O values for two segments of the chronology indicate significant oscillations in temperature but not much change in the source of the precipitation. One abrupt event is evident, indicating a significant drop in temperature with a minor change in source of precipitation, and the proxy data indicate a cold climate followed the event for 60-80 years in this region, suggesting a period of reversal to the predominantly warming trend during the late YD. The proximity and movement of the margin of the Laurentide ice sheet and its meltwater drainage may have contributed to this reversal.