C.V. Campbell, 1992. "Upper Elk Point Megasequence", Devonian-Early Mississippian Carbonates of the Western Canada Sedimentary Basin: A Sequence Stratigraphic Framework, Jack Wendte, Frank A. Stoakes, Clarence V. Campbell
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The Upper Elk Point Subgroup is comprised of a succession of shallow-water carbonates, (mainly basin-filling) evaporites and some siliciclastics up to over 400 m in thickness. This succession represents the initial open-marine inundation of the Alberta "Basin". Upper Elk Point strata overlie a more restricted assemblage of shallow-water carbonates, evaporites and siliciclastics of the Lower Elk Point Subgroup and are overlain by deposits of the Beaverhill Lake Group (discussed in Chapter 7). It is particularly well known for two reasons. Firstly, isolate reefs of the Keg River and more recently Winnipegosis formations provide significant hydrocarbon reservoirs sealed by evaporitic successions. Keg River reefs of the Rainbow area in northern Alberta are particularly well known. Secondly, deposits of the Muskeg and Prairie formations comprise one of the most widespread and thick evaporite successions in the world. Evaporites vary in composition from calcium carbonate to potash salts.
Most of the succession, up to the base of the Watt Mountain Formation, is interpreted to comprise part of a Devonian first-order cycle, as discussed in Chapter 2. The position of the base of this megacycle is unknown, but questionably occurs at the base of the Cold Lake salt. Anhydrites and restricted carbonates of the Chinchaga Formation, overlying the Cold Lake salt, would then be part of the transgressive phase of the Upper Elk Point megacycle. The overlying Watt Mountain Formation, a succession of dominantly siliciclastics, is the uppermost unit of the Upper Elk Point Subgroup, but is interpreted by us to be part of the Beaverhill Lake megasequence. This succession, therefore, is discussed in the ensuing Beaverhill Lake chapter.
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Devonian-Early Mississippian Carbonates of the Western Canada Sedimentary Basin: A Sequence Stratigraphic Framework
The Devonian and early Mississippian strata in the Western Canada Sedimentary Basin include a wide diversity of shallow-water carbonate and basin filling carbonate, shale and evaporite facies. Of these, the large Devonian platform-reef complexes are the most spectacular. They occur in magnificent exposures in the Front Ranges of the Canadian Rockies and in the subsurface of Alberta. In the subsurface, these complexes pool many of the largest oil and gas accumulations in Western Canada. This short course is intended to provide a summary of Devonian and early Mississippian deposits in the subsurface of the Western Canada Sedimentary Basin. One of the major goals is to present the evolution of these strata in a sequence-stratigraphic context. The role of sea-level, tectonic and depositional controls on “stacking” and facies patterns are considered. A second major goal is to relate the occurrence of hydrocarbon pools to this sequence-stratigraphic framework.