Regional-scale lithostratigraphic mapping of the entire Paleozoic succession in northeastern Alberta was undertaken to support the production of a high-resolution 500 x 500 m grid-cell 3-dimensional (3D) model. The stratigraphic dataset comprises formation- and member-level picks from 1307 wells covering 874 townships in an area encompassing the Lower Athabasca Regional Plan (LARP) area. The LARP area is of critical importance to the provincial and federal governments of Canada due to vast bitumen and other hydrocarbon deposits, and the industrial footprint associated with the extraction of these resources.

Paleozoic stratigraphy in the area includes: 1) the lower part of the Middle Cambrian System, 2) the Elk Point Group, 3) the Beaverhill Lake Group, 4) the Woodbend Group, 5) the Winterburn Group, and 6) the Wabamun Group. Cambrian deposits subcrop beneath Devonian strata (sub-Devonian unconformity surface). Strata from the lower part of the Elk Point Subgroup are restricted to a number of sub-basins within the study area, whereas the rest of the overlying Devonian strata are more laterally extensive and form the subcrop at the sub-Cretaceous unconformity surface. The Paleozoic succession is floored by the Precambrian crystalline basement, which in the study area crops out in the far northeast as part of the Athabasca Basin and the Marguerite River Complex, beyond the Phanerozoic basin margin.

Detailed mapping of the Prairie Evaporite Formation was undertaken to redefine the location and extent of the Prairie Evaporite halite scarp, which is a well-known intrastratal dissolution feature that runs NNW-SSE through the study area. The dissolution of greater than 200 m of halite from within the Prairie Evaporite Formation resulted in structural compensation and collapse of the overlying Devonian succession. The resulting structural depression created substantial accommodation space that was the locale for deposition of much of the lower part of the Lower Cretaceous Mannville Group siliciclastics. Redefining the location and extent of the Prairie Evaporite halite dissolution scarp was accomplished through detailed mapping of internal member and marker bed stratigraphy, combined with net evaporite mapping of halite and anhydrite using modern log suites.

The top of the Paleozoic succession in the study area is the sub-Cretaceous unconformity; an angular unconformity. This surface forms the interface between Paleozoic and Mesozoic strata, and its proper reconstruction is integral in understanding depositional trends in the latter, as well as basin hydrodynamics in northeastern Alberta. The deep regional well control used for stratigraphic mapping was also employed to produce a detailed model predicting the location of Devonian subcrop belts at the sub-Cretaceous unconformity surface. Delineation of the unconformity surface was supplemented with an additional 7188 picks, most of which just "tag" the Devonian, as part of the Mesozoic mapping component that completed the Phanerozoic mapping for the 3D model in the LARP area.

NTS Keywords

Hauck, T.E., MacCormack, K.E. and Babakhani, M. (2018): Regional stratigraphic mapping and 3D modelling of the Paleozoic succession in northeastern Alberta (townships 59 - 104, ranges 1 - 19, west of the Fourth Meridian); Alberta Energy Regulator, AER/AGS Report 95, 38 p.