NIPISSING BARRIER STRATIGRAPHY EXPOSED ALONG THE NOTTAWASAGA RIVER IN WASAGA BEACH, ONTARIO

Recent three-dimensional sediment mapping efforts in Simcoe County by the Ontario Geological Survey have reinvigorated interest in local postglacial sediment successions. A cut bank exposure along the Nottawasaga River in Wasaga Beach, Ontario, was studied to improve paleohydrographic reconstructions of the upper Great Lakes. This location provides a unique glimpse into the subsurface through an extensive prograding and aggrading lacustrine barrier system and helps refine the regional stratigraphic framework and lake-level rise to the highstand during the Nipissing Phase of the upper Great Lakes. The exposure was studied by hand-digging thirteen overlapping sediment pits. Sediments were described using standard sedimentological logging techniques, recording lithology, sedimentary structures, bed contacts and unit geometry. Elevations were collected from the top of each sediment pit using a total station and were calibrated to the International Great Lakes Datum (1985). The location of each pit was determined using GPS and aerial photographs. Numerous photographs were taken and sediment samples were collected for grain size analyses. Additional samples were collected beneath prominent unit contacts in the exposure to determine the age of sediments using optically stimulated luminescence. All data are being used to create a facies model for the entire riverbank section. Together, the sediments record a uniquely exposed aggradational sequence deposited during the rise to the last pre-modern highstand of the upper Great Lakes.