Abstract

A total of 13 conodont zones and 11 rugose coral faunal assemblages currently provides a subdivision of the Frasnian of the Western Canada Sedimentary Basin. The conodont zonation adopted is that first developed in the Montagne Noire area of southern France and subsequently found to have widespread applicability, especially when supplemented through the use of graphic correlation. The rugose coral faunal scheme is based on the overlapping ranges of species with wide geographic distribution, but with relatively short stratigraphic duration. Integration of these faunal schemes allows for more precise biostratigraphic control and provides a basis for refined correlation of the sequences of basin fill. As all fossil groups have varying degrees of facies control on their distribution, we do not have conodont and coral biostratigraphic data for all units in the basin. Significant conodont data have been obtained mainly from the margins of the larger bank and reef complexes, rather than their relatively shallow water interiors, and from the basinal strata enclosing them. These data generally support a reciprocal process of reef and off-reef sedimentation throughout the Frasnian. Rugose corals are most commonly developed within the reef and bank complexes (especially the Winterburn Group and equivalents), and particularly near their margins. They are rarer and of less biostratigraphic value in basinal strata. Some of the more significant formational time spans, expressed in terms of Montagne Noire (MN) Frasnian conodont zones, are summarized as follows. The Beaverhill Lake Group of Alberta ranges from the norrisi Zone of the latest Middle Devonian to lower Zone 5. The succeeding Cooking Lake-Majeau Lake interval is in Zone 5 to possibly lower Zone 6, and the overlying Duvernay Formation extends into Zone 10. The Perdrix Formation in outcrop of the Rockies is largely equivalent in age to the Cooking Lake-Majeau Lake-Duvernay, but locally at least ranges into lower Zone 11. The black/grey shale facies of District of Mackenzie and northeast British Columbia (Canol Formation, Horn River Group) ranges at least as high as Zone 6 and locally as high as Zone 10. The Ireton, Leduc, Peechee, lower Mount Hawk interval of Alberta extends through Zone 11, while most of the Nisku, Arcs/Grotto and upper Mount Hawk lie within Zone 12. The "Z-marker" within the clastic basin fill of subsurface Alberta lies approximately at the boundary of Zones 11 and 12. In the southern District of Mackenzie and northeast British Columbia, the Jean-Marie Member and equivalents are in Zone 12. Finally, the Blue Ridge, Simla, Kakisa and equivalents lie primarily within Zone 13.

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