Elements of a genetic framework for inclined heterolithic strata of the McMurray Formation, northeast Alberta

The Lower Cretaceous McMurray Formation hosts a major portion of the bitumen present in the Athabasca Oil Sand deposit. High-grade reservoirs are often associated with inclined heterolithic strata (IHS), which are interpreted to have been deposited through channel bank accretion. McMurray Formation IHS from twenty-eight well cores and several outcrops have been examined and classified based on sedimentological and ichnological character. A model is presented to explain variation in IHS character along the fluvial to marine gradient of a riverine estuary. Additionally, a distinctive facies of IHS pervasively bioturbated with diminutive helical ichnofossils is presented and its paleogeographic significance discussed. As these ichnofossils are taxonomically distinct from established forms, a new ichnotaxon, Spirascensus conferti has been proposed.