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A small limestone reef complex occurs in the Front Ranges of eastern Jasper Park. From exposures in three thrust sheets, reconstruction indicates a sub-rectangular outline with an area of about 30 square miles. The main reef sequence is in the order of 1,400 feet thick, circumscribed by a slightly thinner succession of shales and argillaceous carbonates. This reef is comparable to the moderate sized biostromal reef complexes of the Alberta basin.
The depositional history of the reef can be interpreted from the reef geometry and stratigraphy, well exposed reef margins, and carbonate petrology. The basal transgressive sediments are represented by a widespread, thin, argillaceous, fine calcarenitic, stromatoporoidal and Amphipora limestone (Flume) deposited over a flat erosion surface on Cambrian strata. Due to increasing rates of subsidence the de position of organic, biostromal carbonates (upper Cairn) was restricted to the areas underlain by a thicker development in the basal limestone of stromatoporoidal carbonates, presumably shoals. Stromatoporoid reefs with thin interbeds of Amphipora limestone and calcarenite form the main constituents of the Cairn biostromes. Fine calcarenites (Maligne) deposited adjacent to the biostrom s probably represent detritus eroded from their margins. Further increase in the rate of subsidence induced growth of bioherms around the margins of the stromatoporoid biostromes. These bioherms enclosed a central lagoon. In the central part of the Miette reef this resulted in a gradual change from dark-colored, stromatoporoidal carbonates (upper Cairn) to light-colored, fine, non-skeletal, granular limestone (lower Southesk). Black, pyritic shales (Perdrix) deposited during this period in the adjacent basin indicate stagnant, poorly circulated waters. More rapid subsidence appears to have drowned the reefs, and terrigenous muds reduced basin relief (lower Mount Hawk). Gradual emergence of the reef produced a small platform or bank above which non-skeletal lime sands (main part of Southe k) were deposited in the restricted and agitated waters. Carbonate muds derived from the bank were added to the terrigenous muds (middle and upper Mount Hawk), further reducing basin relief. Lime sands (upper Southesk) gradually spread over adjacent Mount Hawk muds. Scattered small coral reefs developed near the edges of the bank. During this final stage of slow sedimentation interspersed with periods of non-deposition, quartz silts were deposited over the region.
The Miette reef was localized above the positive pre-Devonian arch which parallels the eastern Front Ranges and Foothills. Growth of the Miette reef appears to have been largely controlled by continued differential subsidence above this arch and by shoals and stromatoporoid reefs in the upper part of the Flume.
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