Paper No. 21-3
Presentation Time: 8:45 AM
THE MISSING PUZZLE PIECE IN DETERMINING PAST LAKE LEVEL CONDITIONS AT THE ONLY UNREGULATED OUTLET IN THE GREAT LAKES PRESERVED IN THE STRATIGRAPHY OF THE IPPERWASH STRANDPLAIN
The Great Lakes connect the interior of North America to the Atlantic Ocean through a system of natural and engineered waterways. The Port Huron/Sarnia outlet drains Lake Huron and is the only unregulated outlet in the Great Lakes. Identifying natural decadal to millennial trends and patterns of past lake levels, glacial isostatic adjustment and outlet conveyance is required to make effective and informed decisions for the maintenance of the important Port Huron/Sarnia outlet and the stewardship of the Great Lakes as a whole. Clues to past conditions are preserved in depositional coastal landforms and provide insights into natural sedimentation rates, lake level history, and channel conveyance for the Port Huron/Sarnia outlet. The closest and most complete preserved coastal sequence is the Ipperwash strandplain, forty kilometers northeast of the Port Huron/Sarnia outlet between Kettle Point and Grand Bend, Ontario. The Ipperwash strandplain fills a portion of the ancient Thedford embayment with approximately forty beach ridges. Each beach ridge preserves lake level elevation and shoreline position at the time of deposition. Vibracoring will be used to determine past lake-level elevations, optically stimulated luminescence dating will be used to determine ages, and ground penetrating radar will be used to better understand shoreline behaviour. An Ipperwash strandplain paleohydrograph will then be reconstructed to provide the most detailed account of natural trends and patterns in lake level , glacial isostatic adjustment, and outlet conveyance for the Port Huron/Sarnia outlet. This will provide the background required to place previous beach ridge research in lakes Huron, Michigan, and Superior into context accounting for natural trends and patterns on the scale of decades to several millennia.