Newly Discovered Outcrops of the Viking Formation in the Central Foothills of Alberta: Potential Analogs for Subsurface Reservoirs

Xavier Roca
University of Western Ontario, Department of Earth Sciences
London, Canada
xrocaarg@uwo.ca

The Late Albian Viking Formation, a marine-estuarine sand-prone succession interbedded between transgressive black shale units, is one of the major hydrocarbon reservoirs of the Alberta foreland basin. Although present throughout the subsurface in the Alberta plains and western Saskatchewan, Viking outcrops were not recognized in the adjacent western thrust-and-fold belt prior to 2000. As part of my PhD project, 10 new outcrops of the Viking Formation have been discovered between townships 37 and 39. In these localities, the Viking Formation consists of lower to upper shoreface hummocky and swaley cross-stratified sandstones and interbedded mudstones, that are everywhere erosively capped by a chert and quartzite conglomerate. The conglomeratic unit reaches a maximum thickness of >7 m in Fall Creek, and is characterized by locally steep erosive basal contact, horizontal bedding, accretion surfaces and alternating open and closed-work conglomerate. To the NW, the conglomerate unit gradually thins out over 30 km, disappearing in Gap Creek, where paleosols capping Viking shoreface successions are recognized. The inferred fluvial origin of the conglomerate (with possible marine reworking) and potential adjacent interfluve areas support its interpretation as the fill of a wide, shallow valley of late Viking age. If this is the case, the newly discovered outcrops could represent an analog for the Viking Crystal Field paleo-valley, one of the most prolific Viking pools in the subsurface.