INSIGHTS ON TIMING OF HYDROCARBON GENERATION AND HISTORY OF OROGENIC UNROOFING GAINED FROM PALYNOLOGICAL AGE DETERMINATION OF REWORKED SEDIMENTS IN UPPER CRETACEOUS STRATA OF THE MACKENZIE VALLEY, NORTHWESTERN CANADA

Canada’s energy future will be moving north, necessitating the evaluation of unconventional petroleum potential in the Mackenzie Valley. An established geologic framework is critical for successful resource assessment. The Mackenzie Valley is filled with palynomorph bearing Upper Cretaceous strata of the Trevor (Cenomanian-Turonian), Slater River (Cenomanian-?Coniacian), Little Bear (Santonian-Campanian) and East Fork (Campanian-Maastrichtian) formations. Palynomorph biostratigraphy in conjunction with seismic and well log data offers a potential solution by the accurate definition of sediment age enabling lateral correlation of petroleum bearing rock units, which is essential to developing a robust geologic framework. Additionally, the maturation of organic matter in Upper Cretaceous rocks of the Mackenzie Valley, as indicated by Rock-Eval pyrolysis (T_max), provides constraints on potential oil generation. Existing data indicate that either Cretaceous strata generated hydrocarbons in the Paleogene or that Cretaceous strata are actually immature with extensive recycling and high T_max values derived from reworked organic material. The origin of these T_max data has huge implications for the oil and gas potential in the region as it determines the timing of hydrocarbon generation. The objectives of this study are to determine the best subsurface correlation model as well as the age and extent of sediment recycling using relative changes in the quantity of reworked palynomorphs as a proxy. Preliminary results indicate that there is extensive Paleozoic reworking in the uppermost Cretaceous strata of this well. Therefore, the high T_max values were likely produced from reworked organic material rather than generated by in situ organic material. The age distribution of recycled palynomophs suggest that orogenic unroofing involved the reworking of Carboniferous to Cretaceous source strata into the Little Bear Formation and the reworking of Devonian to Cretaceous source strata into the East Fork Formation. The implications of this study for organic geochemistry and thermal maturity will provide insight on the timing of hydrocarbon generation. Insights on the history of orogenic unroofing may contribute to future regional tectonic studies.