GEOCHEMISTRY OF POTENTIAL HYDROCARBON SOURCE ROCKS OF TRIASSIC AGE INTHE ROCKY-MOUNTAIN FOOTHILLS OF NORTHEASTERN BRITISH-COLUMBIA AND WEST-CENTRAL ALBERTA

Triassic strata in the Western Canada Sedimentary Basin contain signif icant quantities of petroleum. Potential sources for these hydrocarbon s are known for many, but not all, of the Triassic petroleum accumulat ions. This study documents: the geochemistry of potential hydrocarbon source rock intervals from outcrops of the Vega-Phroso, Whistler and L lama members of the Sulphur Mountain Formation and the Grayling, Toad and Pardonet formations. Total organic carbon contents 15 wt.% for the se units, which contain Type II marine kerogen. The biomarker composit ions of rock extracts from Lower and Middle Triassic, thermally mature , outcrop formations are similar in many respects; however it is sugge sted that a number of ratios (e.g., pristane/phytane, C-27 diasterane/ regular sterane, C-27/C-28 sterane ratios) may be used to distinguish oils from these various sources. It is anticipated that these biomarke r data will provide the basis for correlation to oils preserved in reg ions which are presently overmature with respect to hydrocarbon genera tion. A revised thermal maturity map for the Triassic is presented, ba sed on new thermal maturity data from the subsurface of British Columb ia. These new data indicate anomalous heat flow associated with the Ha y River Fault Zone, a basement feature which trends northeast-southwes t and extends from northeastern British Columbia to the Northwest Terr itories. The results presented here have significant implications for hydrocarbon exploration in northeastern British Columbia and west-cent ral Alberta. The occurrence of mature, oil-prone source rocks in regio ns considered prospective only for dry gas suggests new areas with liq uid hydrocarbon potential. The existence and discovery of such hydroca rbon occurrences will require integration of the data presented here w ith knowledge of the structure, reservoir units, seal rocks and timing of hydrocarbon generation and migration relative to trap formation in the area immediately east of the outcrop belt. This study also docume nts hydrocarbon source rock potential in Lower Triassic strata at outc rop. These oil-prone intervals are also believed to occur in subsurfac e regions to the east of the Foothills Belt and have likely provided t he source for local oil accumulations in Lower Triassic strata. Strati graphic studies, using sequence stratigraphic analysis, are currently in progress, with a view to predict the lateral distribution of these organic-rich intervals into sparsely explored regions. Finally, it is suggested that the organic-rich Pardonet Formation in northeastern Bri tish Columbia may represent a prospective fractured shale play in the Western Canada Sedimentary Basin.