ABSTRACT

The late Paleozoic succession in the vicinity of Wapiti Lake, northeastern British Columbia, 90 mi (150 km) southwest of Grand Prairie, Alberta, consists of strata referable to the Permian Ishbel Group that rest unconformably on the eroded surface of the Mississippian Rundle Group, the contact being marked by a spectacular basal limestone/chert submarine talus breccio-conglomerate. An unusual light grey to white porous dolomite unit which caps the fossiliferous Rundle succession was the primary prospective reservoir rock in an anticlinal trap believed to exist beneath folded and overthrust lower Paleozoic strata near Window Lakes; it was tested by the wildcat well Texas Gulf Sulphur et al. Narraway C-86-G in 93-I-7. The Permian Ishbel group consists of three formations. In ascending order these are: 1) the Belcourt Formation, a cherty dolomite with Schwagerinid foraminifera of Wolfcampian to Lower Leonardian age; 2) the feature-forming Ranger Canyon Formation chert rock, here of Guadalupian age on the basis of brachiopod content, which is found in virtually every Permian section from the Liard and Tetsa Rivers in the north to the Crowsnest area 1500 km to the south, and resting here, as elsewhere, on a thin phosphatic chert conglomerate and regional unconformity within the Permian; and 3) the Mowitch Formation, a porous brown sandstone, also of Late Permian age, which is paraconformably overlain by recessive dark grey siltstones of the Triassic Spray River Group. The Belcourt Formation carbonate facies is unique to this area, being the age equivalent of fine-grained clastic phosphatic sequences elsewhere, such as the "Mt. Greene Beds" on Peace River, correlative strata in Pine Pass, the Johnston Canyon Formation of the Banff area and further south, and the lower part of the fossiliferous phosphatic succession west of the Elk Valley in southeastern British Columbia.