Special Report 061

Special Report 061

SPE 061

Phases 1 to 4 Extech Study of the Early Proterozoic Athabasca Group, Northeastern Alberta

Author(s) Ramaekers, P. Date 2003-12-01

Fifty-five diamond drillholes (DDH) within the Alberta portion of the Athabasca Basin were reviewed.

The Athabasca Group is subdivided into six formations within Alberta, which are, from base to top, the Fair Point, Manitou Falls, Lazenby Lake, Wolverine Point, Locker Lake and Otherside formations. These lithostratigraphic units are overlain in places by Devonian strata and ubiquitously by Quaternary and Recent surficial unconsolidated sediments. A basal coarse-grained lag (slightly reworked regolith) is variably present at the base of the Fair Point (FP) and the Manitou Falls (MF) formations, where each overlies the basement. The Fair Point Formation is divided into three regionally mappable units on the basis of maximum grain size and percentage of granules/pebbles. The Manitou Falls Formation contains thick, well-sorted sandstones of the MFc member, with the pebbly MFb member absent in the southern third of the basin. Thin siltstone units at the base of the FP and MF indicate the variable presence of a basal fine-grained unit (FPa, MFa). The Lazenby Lake Formation (LzL) is restricted to the southern twothirds of the basin and forms a wedge thinning to the north. Two new mappable stratigraphic units were identified in the Wolverine Point Formation (WP), which shows progressive thinning to the south due to erosion or non-deposition. The disconformably overlying, pebbly Locker Lake Formation (LL) thickens to the north and shows a middle coarser member. The Otherside Formation overlies the Locker Lake Formation in the north central half of the study area, but is not present in any of the drillcore examined in this study. The Paleozoic section, Devonian with perhaps some older units at its base, intermittently overlies the southern quarter of the Athabasca Basin in Alberta. It consists largely of fine-grained clastics with minor amounts of carbonates at the top, where coarser clastics are restricted to the base and along the southwest margin of the basin.

Ramaekers, P. (2003): Phases I to IV Extech IV study of the early Proterozoic Athabasca Group, northeastern Alberta; Alberta Energy and Utilities Board, EUB/AGS Special Report 61, 35 p.