The sedimentary petrography and stratigraphy of the MIssissippian Whitewater Lake Member of Southwestern Manitoba

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Zakus, Paul David
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The Whitewater Lake Member of the Mississippian Lodgepole Formation is a subsurface unit which can be correlated over an area of about 1400 square miles in southwestern Manitoba. The member is divided into an upper and a lower unit, the lower unit being typically more argillaceous than the upper unit. The Whitewater Lake Member represents a well developed cycle of calcareous sedimentation similar to the underlying Virden Member. Whitewater Lake sedimentation began with and was ended by an influx of clay size terrigenous sediment. These argillaceous zones allow the member to be correlated but, however, they thin and are difficult to recognize to the west and correlations become unreliable in that direction. During Whitewater Lake times, a large, shallow, coastal shoal occurred in the Whitewater-Lulu Lake area. To the west and in the Virden area, deeper water, open marine shoal margin and shallow shelf conditions prevailed. The coastal shoal area is characterized by lump, colitic, and argillaceous limestones; the shelf and shoal margin area by micritic, skeletal, and argillaceous limestones. It is believed that the Whitewater Lake limestones were formed under conditions very similar to those under which calcareous sediments are forming on the present day Bahama Banks. The Whitewater Lake Member is in close proximity to the Mississippian-Jurassic unconformity and has undergone extensive dolomitization and anhydritization related to this unconformity particularly where the overlying Jurassic Amaranth Red Bed cover is less than twenty feet thick.