An exceptional record of the sedimentology and biostratigraphy of the Montney and Doig formations in British Columbia

Abstract

Abstract The Talisman Altares 16-17-083-25W6M well in British Columbia penetrates the entirety of the Triassic Montney Formation and possesses core coverage of most of it, including the basal contact with the underlying Permian Belloy Formation and its upper contact with the base of the Triassic Doig Formation. The Montney Formation in British Columbia is punctuated by several flooding surfaces and is bound top and bottom by two sequence boundaries: one at the Belloy-Montney formation boundary and one at the Montney-Doig boundary. These two surfaces can be correlated throughout wells in British Columbia and into Alberta. Conodont data from British Columbia shows that the lower-middle Montney boundary is Smithian in age, and the middle-upper Montney boundary approximates the Smithian-Spathian boundary. These age determinations are significantly younger than previous estimates for the equivalent boundaries in Alberta, underscoring the inherent diachroneity of lower Mesozoic lithostratigraphic subdivisions in Western Canada. The Montney-Doig boundary occurs within the Spathian in this well, and is therefore older here than in other wells in northeastern British Columbia. It is also older than previous estimates for the age of the boundary that have ranged from the Anisian to the Ladinian.