An Alternate Model for the Deposition of the Upper Ordovician Red River Formation (Bighorn Group; Canadocian/Ashgillian) in the Williston Basin of Southeast Saskatchewan, Canada.
The Red River Formation is traditionally inferred as a shallowing/brining upwards sequence (Kendall, 1976; Kent and Haidl, 1999; Pratt and Haidl, 2008). Hydrocarbons are restricted to positive features over structural basement highs (Kreis, 2000; Potter, 2002). An anomalous geothermal history allowed early maturation and migration of hydrocarbons (Osadetz, et al, 1989, 2006). This paper challenges the Red River doctrine and suggests a stratigraphic trapping/Sequence Stratigraphy approach to deposition and hydrocarbon trapping. The Red River was deposited in localized incised valleys similar to the Mississippian Midale Beds (Lake, 2015; Lake and Kent, 2016). The laminated muds and bedded anhydrite represent the restricted circulation of the initial flooding phase, followed by tidally influenced burrow-mottled muds and calcareous algae-rich tidal channels. These incised valley fills represent a marine transgression on an exposed shoreline, similar to Shark Bay, Western Australia (Davies, 1970) and Sabkha Faishakh, Qatar (Illing and Taylor, 1993). The incised valley fills deepen upwards into high energy tidal channel reservoir facies. The Red River valley fills are localized in scale rather than being basin-wide. Sedimentation was controlled by north-south trending structures associated with basement movement along the Superior/ Trans Hudson boundary and is part of the Great North American Carbonate Platform. The early maturation and predictable stratigraphic trapping suggests large reserves are trapped in the updip portion of the lowest structural locations where tidal energy was the greatest. Stratigraphic trapping in incised valleys would provide a healthy alternative to the structural model presently in vogue.
AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017