The geological and hydrological environment of the Whitewater Lake Basin, Manitoba

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Kohut, Alan P.
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The Whitewater Lake Basin is located in southwestern Manitoba within the Interior Plains region of western Canada. The main hydrologic feature of the basin is Whitewater Lake, a shallow closed basin lake less than 5 feet deep occupying 25 square miles in the centre of the basin. The lake lies within the Boissevain Till Plain and is underlain by Cretaceous Shales of the Riding Mountain Formation. A Late Cretaceous- Tertiary outlier of Boissevain Formation sandstone overlain by sandstones and shales of the Turtle Mountain Formation occurs on Turtle Mountian immediately south of the lake. The origin of the basin is due to a collapse feature caused by the solution of salt from Devonian evaporite deposits and/or to a Pre-Jurassic erosion feature on the Mississippian "escarpment" underlying the basin. During Tertiary- Early PLeistocene time a major preglacial river existed under the present location of Whitewater Lake. Three ti11 sheets were deposited in the basin during the PlLeistocene separated by interglacial deposits of sand and gravel. During final deglaciation a glacial lake formed in the basin and extensive outwash deposits of sand and gravel were deposited on the north slope of Turtle Mountain. Recent sediments up to 18 inches (46 cm.) in thickness indicate post-glacial deposition has been slow and uniform. The accumulation of calcareous bioclasts and plant fraguents is an important bio-sedimentological process operating in the lake. The major portion of the annual precipitation falls as rain during the period April to August...