Abstract Detailed study based on sample determinations of 12 wells, one of which is in Saskatchewan and 11 in the plains of Alberta shows a sequence of strata of questionable age that is herein referred to as the Elk Point formation. The formation underlies a thick section of Upper Devonian strata and in turn lies on Ordovician, Cambrian, or pre-Cambrian rocks. It generally consists of two conspicuous red shales, anhydritic dolomites, and thin slightly fossiliferous argillaceous silty limestones, in addition to one to three salt members. Maximum thickness of the entire formation is 1,557 (plus or minus) feet. The age of the Elk Point formation is considered Silurian. However, recent evidence suggests at least the upper part of the formation to be Middle Devonian. (On the basis of new evidence, the tentative “Silurian” correlation of the Elk Point formation is abandoned in favor of a Middle Devonian age designation. J.R.M., September, 1952.) A detailed composite geological log of Elk Point area is presented.

Abstract The name, Elk Point formation, has been applied to the deposits, mainly evaporite, below the Waterways formation in the Anglo-Canadian Elk Point boreholes 1, 2, and 3, located in east central Alberta. It has long been a question as to whether the formation is Silurian or Devonian. Data from a newer hole in the same vicinity permit more complete description of the formation, and its subdivision into nine members. The formation as a whole, or its equivalents, extends widely in the Western Canada sedimentary basin, and the individual members are traceable through lithologic variations over much of this basin. The Elk Point is equivalent to Elm Point and Winnipegosan formations, and the newly-established Mafeking formation, of the Manitoba outcrop section. It is correlative with Pine Point and Presqu’ile formations of the Great Slave Lake section and with Ramparts formation of the Mackenzie Valley. In the Elk Point are found two faunas, Stringocephalus in the upper part, A try pa arctica in the lower. Two new names are given to recently discovered brachiopods which may prove of value as guide-fossils:

Abstract 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.