Surficial geology and stratigraphy of the Killarney-Holmfield area, southwestern Manitoba
Conley, Glenn G.
Seven tills, ranging in age from pre-Wisconsinan to late Wisconsinan, were identified in the Killarney-Holmfield area. The pre-Wisconsinan glaciations are represented by the Largs, Tee Lakes and Shell Formations, and the Early Wisconsinan glaciation, by the Minnedosa Formation. A widespread unconformity between the Shell and Minnedosa Formations is represented by a cobble lag. A second widespread unconformity between the early Wisconsinan Minnedosa Formation and the Late Wisconsinan Lennard Formation is represented by a boulder pavement in Saskatchewan, southwestern Manitoba and northeastern North Dakota. In the Tiger Hills upland the Late Wisconsinan Glenora and Belmont Formations overlie the Lennard Formation. Tentative correlations have been made with the tills of the Riding and Duck Mountain area (Klassen, 1979), northeastern North Dakota (Bluemle, 1984), northwestern Minnesota (Fenton et al, 1983; Harris et al., 1974) and southeastern Manitoba (Fenton, 1984; Fenton et al., 1983). Late Wisconsinan ice advanced into the Killarney-Holmfield area from the northwest, depositing the till of the Lennard Formation. The Keewatin ice reached western Iowa about 20 000 B.P. The glacier advanced and retreated several times before retreating north into the Killarney-Holmfield area, about 12 000 B.P. A brief readvance brought the glacier to the Cartwright moraine before the western ice retreated to the west for the last time. About 11 400 B.P., the Red River lobe advanced to the Darlingford-Edinburg moraine from the northeast, depositing the till of the Glenora Formation. The ice crossed the Pembina spillway at Swan Lake, blocking the drainage of meltwater to the east. As the ice retreated, the ponded waters of Lake Souris drained rapidly through the spillway to Lake Agassiz. About 11 200 B.P. the Red River lobe readvanced to the Darlingford-Edinburg moraine, depositing the till of the Belmont Formation. The Pembina spillway was blocked for a second time and the level of the ponded meltwater in the Killarney-Holmfield area rose to 465 m. The ice retreated to the north and the ponded meltwater drained rapidly through the spillway. A brief readvance brought the glacier to the Baldur thrust moraine. After a short time, the ice retreated to the north and the Glenboro outwash formed along the north edge of the escarpment. This lower outlet drained meltwater from the west and the Pembina spillway was soon abandoned.