The Mississippian sediments of Southern Alberta Plains region, known only from the subsurface, are described as to lithology, thickness, rock units, their correlation with adjacent areas, and history of deposition.

The section thins from west to east due to post-Paleozoic erosion and to less degree by reason of depositional thinning. In the extreme western part of the map area, there remains approximately 1,400 feet which is one-third of the total Mississippian measured in the mountains.

The rock units and member names defined and introduced by Douglas in 1953 and the more recently emended subdivisions and new names being proposed by the Mississippian Committee for the Foothills area in the vicinity of Turner Valley oil field are defined, for adjacent Plains region, in Shell-Anglo Pine Creek well. The formation names, Bakken, Banff, Pekisko, Shunda, Turner Valley, and Lower Mount Head, are used for this general area. It is further proposed to introduce the name Elkton for the commercial gas zone of the Elkton well. This zone is regarded as correlative of the Crystalline and Lower Porous of Turner Valley field usage.

The correlation of these rock units is illustrated on cross sections from the Pine Creek well to the northeast, toward the Big Valley fields, southeast to Saskatchewan and south to Kevin-Sunburst area in Montana. The Banff of Pine Creek well is correlated with the Mc+Mb2 (Lodgepole) of the Kevin

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Sunburst area; the Pekisko and Shunda plus Elkton member of the Turner Valley with Mb1 (Mission Canyon); and the upper part of the Turner Valley with the Ma unit.

The typical lithological units of the Bakken formation of Montana and the Dakotas are present in the southeastern part of the map area. The formation thins to near zero toward the west as a depositional edge due to epeirogenic movements prior to Mississippian deposition. To the north, the lower black shale only is present as a distinguishable rock unit and the name Exshaw is applicable. The upper part of the formation changes to gray shale that is not readily distinguished from the overlying Banff shale.

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