LITHOFACIES CHARACTERIZATION AND PLACER GOLD POTENTIAL OF THE MANNVILLE GROUP (CRETACEOUS), NORTH-CENTRAL SASKATCHEWAN, CANADA

The Cretaceous (Albian to Aptian) Mannville Group comprises one of the oldest sequences in a southeastward thinning siliciclastic sedimentary wedge that spans the entirety of the Western Interior Sedimentary Basin (WISB). Mannville sediments were deposited during a major episode of subsidence and sedimentation controlled by the Laramide Orogeny to the west. Due to their wide geographic distribution and varied depositional controls, stratigraphic nomenclature varies throughout the WISB in Alberta and Saskatchewan. In Saskatchewan the Mannville Group is disconformity bound, broadly consisting of the Cantaur Formation (fluvial to marginal marine) overlain by the Pense Formation (marginal marine to marine). Each formation is disconformity bound, with geographic regions consisting of distinct members reflecting regional controls on sedimentation and base level. The Mannville Group has been a prolific oil and gas producer in Western Canada but has rarely been considered for alternative economic resources. The purpose of this study is to utilize the Mannville Group as a case study in expanding the economic potential of well known deposits to previously unconsidered resources.

In the study area Mannville Group sediments crop out along the Bow and Nipikamew Rivers, the southwestern shore of Wapawekka Lake, the northern flanks of the Wapawekka Hills, and south at Ennis and East Trout lakes in northcentral Saskatchewan. Due to relatively poor exposure and accessibility, few studies have focused on comprehensive lithology, stratigraphy, and economic potential of the Mannville Group in this area. Detailed sedimentologic data including facies analysis and trace fossil associations, paleocurrent indicators, palynology samples, and targeted bulk assay sampling has been undertaken from outcrop and available drill core. Paleocurrent indicators suggest paleodrainage trended north to south, with sediments sourced from gold-bearing Precambrian rocks of the La Ronge and Glennie domains in northern Saskatchewan. This study presents seeks to 1) interpret the sedimentology and depositional history of the Group in the study area; 2) establish a stratigraphic and biostratigraphic framework to correlate deposits to other regions in the basin; 3) expand on a previous report of paleoplacer gold occurrences in Mannville sediments south of the Precambrian-Phanerozoic boundary.