The purpose of this thesis was to determine the stratigraphic relationships between the Lyleton formation and the red beds of the Amaranth formation in southwestern Manitoba, and to determine their distinguishing lithologic characteristics.

Red beds consisting of anhydrite, dolomitic siltstone, shale, and sandstone constitute the basal unit of the Amaranth formation and are defined as the Lower Amaranth Member. This member forms a thin relatively uniform blanket of sediments overlying eroded Paleozoic strata, principally of Devonian

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and Mississippian age. The thickness of the unit is determined by the topography of the erosion surface, which is controlled in turn primarily by structures in the underlying Mississippian strata. The Lower Amaranth is believed to be Jurassic in age.

The Lyleton formation consists of red and green shales, with some dolomite. It contains very little coarse clastic material such as is found in the Lower Amaranth, and because of this the Lyleton can usually be distinguished from the Lower Amaranth lithologically. The Lyleton occurs only between strata of known Mississippian and known Devonian age, and is itself believed to be of Devonian age. It shows a uniform thinning towards the east until it is truncated by the pre-Amaranth erosion surface.

Detailed lithologic characteristics, environments of deposition, correlation problems, structural control of thickness in relation to oil production, and economic importance of the units are also discussed.

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