C.V. Campbell, 1992. "Beaverhill Lake Megasequence", Devonian-Early Mississippian Carbonates of the Western Canada Sedimentary Basin: A Sequence Stratigraphic Framework, Jack Wendte, Frank A. Stoakes, Clarence V. Campbell
Download citation file:
This succession incorporates the entire Beaverhill Lake Group and the underlying Watt Mountain Formation. These units are interpreted to comprise a first-order cycle. Collectively, the progression of strata in this megasequence corresponds to an overall transgressive-regressive succession. Thicknesses of these strata range from nil along the Peace River Arch where these units onlap out, to over 200 m in east-central and northern Alberta. This pattern reflects greater rates of subsidence away from the Peace River and Western Alberta arches.
Figure 1 depicts the general paleogeography of the Beaverhill Lake megasequence in the WCSB. This map illustrates the distribution of both shallow-water and basinal facies. In Alberta the dominant element is a deep-water basin that extends as far south as south-central Alberta. Because of the truncation of Beaverhill Lake strata along the pre-Jurassic and pre-Cretaceous unconformities, the configuration of the connection of this basin to the deep-water seaway in the Northwest Territories is unknown.
The basin is fringed by shallow-water platform carbonates on both its east and west sides. The platform carbonates along the southeast side of the basin grade into the more restictive carbonate-evaporite successions of the Souris River Formation. Shallow-water carbonates along the west side of the basin and south of the Peace River Arch include backstepping platform and bank successions. These units onlap and ultimately cover the Western Alberta Arch. Of particular note in this area is the occurrence of the Swan Hills platform margin at Caroline. A giant gas-condensate pool was discovered here by Shell in 1985 which ranks as the most significant hydrocarbon discovery in Devonian rocks in the WCSB in the last quarter century. Further north, isolate Swan Hills reef complexes occur on a more areally extensive carbonate platform, basinward of time-synchronous bank development. Collectively, more oil is pooled in these reef complexes than any others in the WCSB.
Figures & Tables
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.