Abstract

At Mount Haultain, 16 miles north of Jasper, Alberta, the undolomitized condition of abundant stromatoporoids at the south flank of the Ancient Wall “reef” complex of Frasnian Age, makes study of their palaeoecology possible. The role of the stromatoporoids in the carbonate facies and in the zone of interfingering of the carbonate and argillaceous basin facies can be studied here. Four different fossil communities successively inhabited the south flank of the Ancient Wall complex during the deposition of the Cairn and Southesk Formations. 1. The building of the bank associated with the Cairn Formation is associated with a community of stromatoporoids dominated by a species of Actinostroma and Hammatostroma but including also abundant thick pillared Trupetostroma, Hermatostroma, Syringostroma? confertum, and Stromatopora cf. S. cygnea. 2. A community characterized by Syringostroma? confertum and Stromatopora cf. S. cygnea lived on the steeper slopes of the carbonate front in early Southesk time and constitutes the fauna of a coarse debris bed at the base of the Mount Hawk Formation. 3. The stromatoporoids were replaced in middle Southesk time by a coral fauna at the margin of the bank. 4. The stromatoporoids recurred at the end of Southesk time when lime sands extended across the basin facies. This last community is characterized by a species of Trupetostroma with large galleries and by Syringostroma? confertum.