PALYNOLOGICAL EVIDENCE OF PALEODROUGHT IN THE GREAT LAKES REGION

Vegetation and water level are good proxies of moisture availability and water budgets. Insolation-driven arid conditions are recorded for the early Holocene in the Great Lakes region. An increase in herb pollen has been noted in pollen diagrams from the Midwest and Great Lakes regions, and a Boreal Parkland flora has been reconstructed for the region northeast of Georgian Bay during the early Holocene. Aridity produced closed basin conditions during the late Lake Hough phase of Georgian Bay, as water levels fell below the controlling sill following the removal of meltwater and Lake Agassiz overflow from the water budget of the Upper Great Lakes. Closed basin lowstand conditions are supported by lacustrine microfossils, notably a thecamoebian assemblage recording slightly saline bottom waters. This drought, which apparently resulted from a slight shift in prevalence of the three dominant airmasses, appears to have impacted First Nations people, whose oral history includes references to salty water. This work has implications for this region whose economy is strongly linked to modern lake levels and water quality.