In Search of Cordilleran Point Sources to the Southern McMurray Sub-Basin

In the east-central Alberta, isopach values of the McMurray Formation measured from the overlying Wabiskaw Marker datum show that paleotopographic relief on the sub-Cretaceous Unconformity is express by three paleo-valleys carved into the Grosmont-Wainwright Highlands. The paleo-valleys are named herein as: Grouse, Quail, and Ptarmigan. Mineralogical analysis of McMurray Formation sandstones in the paleo-valleys resolves subtle but recognisable vertical and spatial variations in composition. Feldspar contents decrease and lithic contents increase with stratigraphic depth. Based on petrographic analyses, McMurray Formation sandstones are sourced dominantly from a continental-scale drainage across the craton, with secondary input from uplifted sedimentary strata in the west as well as from the Canadian Shield in the east. Probable, paleo-tributaries can be superimposed on isopach maps of the McMurray Formation that, when coupled with net-sand maps, appear to bisect the highlands, suggesting that the Grosmont-Wainwright did not prevent some Cordillera sediment from entering the Ptarmigan and Quail paleo-valleys. This Cordillera-derived sediment was delivered via Edmonton Valley, and is calculated to constitute approximately 35% of the sediment supplied.