Open File Report 1996-05

Open File Report 1996-05

OFR 1996-05

Preliminary Mapping and Field Reconnaissance of the Lower to Upper Cretaceous (Middle Albian to Lower Turonian) Stratigraphy - Northeastern Alberta

Author(s) Cotterill, D.K. Berhane, H. Date 1996-02-14

As far as non-renewable resources are concerned, northeastern Alberta is known best for its enormous bitumen reserves contained within the Lower Cretaceous Mannville Group. The petroleum industry's principle interest continues to be the development of the oil sands within the McMurray Formation. Recent exploration by the mineral industry, in the region, has identified other sedimentary units that may potentially contain economic deposits of precious metals such as gold, silver and platinum. Initial exploration programs focused on Devonian carbonates that directly underlie the Cretaceous McMurray Formation. Anomalously high, isolated occurrences of gold were reported by several companies near Fort MacKay (Figure 1), a town situated along the Athabasca River, about 60 km north of Fort McMurray. Here, carbonate members of the Waterways Formation crop out along the Athabasca River and the tributaries that feed it. Speculation on the existence of economically recoverable gold and other metals from the Devonian carbonates prompted the leasing of large tracks of land in northeastern Alberta. As exploration programs expanded to other areas, additional sedimentary units were evaluated for their metallic potential.

This expansion led to a second stratigraphic target within the Upper Cretaceous succession. Most exploration activity has now shifted for the time being to Cretaceous units in the Birch Mountains, situated about 130 km northwest of Fort McMurray. Most tributaries, presently draining the northeast flank of the mountains, incise to Upper Cretaceous units. Stream sediment samples taken from the McIvor River valley, the most prominent drainage feature, revealed anomalous concentrations of sulphides. Very fine grains of pristine gold were also recovered and are thought to be locally derived. Gold collected, thus far, is believed to come from within the Labiche Formation, a thick succession of strata comprised dominantly of mudstone interbedded with thin siltstones and sandstones. Little geological documentation exists for the Labiche Formation as well as other Cretaceous strata in the area that bound this unit. Results from field reconnaissance sampling, over the past two summers, have identified several geochemical anomalies. Some of these targets may be drilled next summer (1996).