Abstract

Within deposits of the Cardium Formation at the Pembina field two formal lithostratigraphic units are recognized: the Pembina River Member and the Cardium Zone Member: they identify the reservoir and the top seal respectively. Rocks that comprise these two members are characterized by five lithofacies: 1. bioturbated dark grey shale; 2. bioturbated, thin and very thin bedded shale, siltstone and fine grained sandstone; 3. thin and very thin bedded fine grained sandstone, siltstone and black shale; 4. medium to thick bedded, very fine and fine grained sandstone; and 5. conglomerate. These lithofacies are typical of a marine shelf molded by frequent storm events. Complex patterns of sedimentation and scour define the upper, high-energy portion of the Pembina River Member. Sediment could have been transported offshore episodically not only by downwelling coastal currents during storms, but also by large seasonal river floods. These latter deposits would have been subsequently reworked and redistributed by multiple storm events. Sediments may also have been supplied during changes in sea-level stand to be re-molded and re-sedimented by storms during a succeeding sea-level stand.