| In southern Ontario, extensive outcrops of glaciolacustrine muds and shoreface sands of Late Pleistocene age are exposed near Toronto, and were deformed by floating ice masses in an ancestral ice-dammed Lake Ontario. Outcrop mapping and a GPR survey identify ice scour structures up to 4 m, 10 m wide and at least several hundred metres; long and underlain by sub-scour sediment deformations up to 5 m below the scour. The scours also have ridged margins, as observed in modern scours.;Paleoenvironmental information can be derived from ancient ice-scoured strata using an FEM numerical model of sub-ice scour deformation. For the largest ice scour exposed at Scarborough, ice mass is 0.04 Mt, keel draft is 10 to 30 m and scouring force is 5 x 103 kN, consistent with a small ice berg or pressure-ridged lake ice. Estimates of ice mass dimensions are consistent with independent sedimentological reconstructions of paleobathymetry. |
