Biostratigraphy and sedimentology of Triassic hydrocarbon-bearing rocks in northeastern British Columbia

• Main Author: Golding, Martyn Lee
• Format: Text
• Language: English
• Published: University of British Columbia 2014
• Subjects: Arctic; Yukon; Liard; Montney
• Online Access: https://dx.doi.org/10.14288/1.0166904; https://doi.library.ubc.ca/10.14288/1.0166904

The Triassic Montney and Doig formations in the subsurface of northeastern British Columbia are important hydrocarbon reserves for the province. However the age and tectonic setting of these formations, and their outcrop equivalents (Grayling, Toad and Liard formations), are poorly constrained. The collection of conodont and detrital zircon samples from outcrop sections, and from core taken from subsurface hydrocarbon wells, has allowed the biostratigraphy of these formations to be improved, and the tectonic setting to be inferred. The study of new conodont samples, together with re-examination of existing collections, has led to the recognition of more than thirty new species and morphotypes within the Anisian (Middle Triassic) of British Columbia. These new taxa have in turn allowed the recognition of 11 new faunal assemblages that further refine the conodont biostratigraphic scale for the Anisian of British Columbia. Conodont biostratigraphy of the Montney and Doig formations in the subsurface has allowed correlation of these formations with those of surface sections, and also for the first time provided an age for the boundary between them. The boundary is recognised to be diachronous, and it is oldest in the centre of the study area. The basal Doig Formation is condensed, and shows most condensation at the edges of the study area. Both observations imply the presence of palaeo-highs to the west as well as to the east during the Triassic. This conclusion is supported by detrital zircon geochronology, which demonstrates the presence of sediment derived from the Arctic and from the pericratonic Yukon-Tanana terrane in the Triassic rocks of northeastern British Columbia. Previous hypotheses of Permo-Triassic accretion of this terrane onto the North American margin (the Klondike Orogeny) are supported by this study, and the Triassic sediments of northeastern British Columbia are interpreted to have been deposited in the foreland basin of this orogeny.