ABSTRACT

The Cardium Formation in the Kakwa region of west-central Alberta is subdivided into three members. The basal, sandstone-dominated Ram Member is a relatively uniform lithosome with northwest- to southeast-trending thin and thick zones. The middle Moosehound Member is an eastwardly thinning terrestrial mudstone and sandstone lithosome that merges with the marine, mudstone dominated, eastwardly thickening lithosome of the Cardium zone Member.

The Ram Member grades from bioturbated sandy mudstones at its base upward through a sequence of rhythmites and gutter casts, low-angle inclined, trough- and planar tabular- cross-stratified sandstones, which are capped by an extensively bioturbated swash crossbedded and massive sandstone with a rooted and pedogenically altered upper surface. The Moosehound Member consists of extensive deposits of carbonaceous and pelecypod-rich mudstone, interlaminated, commonly pedogenically altered, sandstone and mudstone, and wave and current bedded sandstone. The facies architecture of these two members is typical of a prograding, mesotidal barrier and backbarrier assemblage with modification by wave, storm and riverine processes.

The capping Cardium zone Member is characterized by extensive sandy mudstone deposits that are typically well bioturbated, and contain trace fossils belonging to ichnofacies ranging from Nereites through Skolithos. These dominantly mudstone deposits define a series of parasequences that geographically form either regional, sheet-like or local, elongate ridge-like features. The Cardium zone displays a facies architecture indicative of shallow-shelf to shoreface sedimentation along a relatively sand-starved, mud-dominated coastline.

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