The Effect of Cambrian Paleogeography on the Distribution of the Overlying Beaverhill Lake Carbonate, Southern Alberta [Abstract]

ABSTRACT Facies mapping of the Cambrian in the subsurface of southern Alberta shows that the Cambrian paleogeography has a marked influence on the distribution of the Middle to Upper Devonian Beaverhill Lake carbonates. During the Cambrian, southern Alberta was a shallow marine basin surrounded by shoal areas on three sides. These shoal areas bordered the Peace River Arch to the north, the West Alberta Ridge to the west, and the Sweetgrass Arch to the south. Sedimentary rocks originating in the shallow basin consist of glauconitic sandstone and shale, quartzarenite, flat-pebble conglomerate, coquina and minor carbonate. Shoal areas are reflected predominantly by mottled dolomitic mudstone to packstone, oolitic grainstone, cryptalgalaminate, flat-pebble conglomerate and coquina. Mud cracks are abundant in places. Initial Cambrian paleogeography controlled the distribution of subsequent Cambrian sedimentation. Resultant facies distribution impacted on the paleotopography of the Cambrian. Carbonate facies in shoal areas were more resistant to pre-Devonian erosion than the basinal clastic facies. It is possible that the Cambrian clastic section has suffered more compaction than the carbonate section. The combination of these factors resulted during late Givetian, early Frasnian time in a topographic depression bordered by relatively high areas that exerted a primary control on sedimentation (Beaverhill Lake Formation). Beaverhill Lake paleogeography across southern Alberta was dominated by a carbonate bank composed of limestone, dolomite, and evaporites, a large shale basin, and a carbonate platform with reefal development (the Swan Hills reef complex). These major Beaverhill Lake paleogeographic features are closely related to the paleogeographic and lithofacies patterns of the underlying Cambrian rocks. End_of_Record - Last_Page 183-------