HOLOCENE HYDROLOGIC AND CLIMATE VARIABILITY NEAR THE AISHIHIK LAKE AREA, SOUTHWESTERN YUKON, CANADA

Paleolimnological records from small, closed-basin lakes in arid and semi-arid regions of Western Canada can be used to infer Holocene climatic and hydrologic histories of these areas. Paleoecological studies and field observations in the Aishihik Valley of southwestern Yukon suggest long-term hydrologic fluctuations may have occurred during the last 10,000 years. This study applies a multi-proxy approach using microfossils from lake sediments to determine the timing and duration of possible paleo-drought events. Analyses of sediment organic and carbonate content from three lakes suggest oscillations between moist and arid conditions. Ostracod assemblages were analyzed in a sediment core and, when compared to a modern freshwater ostracod calibration set, suggest the possibility of potential modern analogues throughout the length of the core. Climate reconstructions based on fossil ostracod assemblages reveal changes in carbonate ¹³C and ¹⁸O, Mg/Ca, mean July air temperature and water depth through time. These changes are consistent with oscillations in organic and carbonate content. Drought events lasting between 500 and 1,000 years likely took place at approximately 5,000, 3,500 and 1,500 cal years BP.