EVALUATING TERRANE DISPLACEMENT, FOLD-THRUST BELT GROWTH, AND SEDIMENT DISPERSAL IN THE CANADIAN ROCKY MOUNTAIN FORELAND BASIN (Invited Presentation)

Questions remain over the paleolatitude of the Intermontane and Insular terranes in the late Mesozoic, as well as the temporal evolution of exhumation across major thrust sheets in the Canadian Cordillera. Batholiths in the Coast Mountains (active ~175-50 Ma) intrude the Intermontane and Insular terranes; their now eroded volcanic edifice would have served as a potentially mobile zircon factory during purported terrane displacement. Here, we test if near syndepositional zircons derived from the Coast Mountains contributed to the autochthonous Jurassic-Paleocene Alberta foreland basin, along with documenting the exhumation of thrust sheets through time. Detrital age spectra show inter-sample variability, but most spectra show prominent age modes at ca. 1.8-1.6 Ga, 1.3-1.0 Ga, 500-300 Ma, and 250-65 Ma. In many samples from the basin, the 250-65 Ma age modes include populations that overlap with biostratigraphic age constraints, suggesting the presence of roughly syndepositional zircons. We use Lu-Hf isotopes and trace element geochemistry on the near syndepositional grains to determine their most likely ­­­source. Possible sources include magmatic centers in the Omineca belt, Coast Mountains, and southerly regions, including the Idaho and Boulder batholiths and associated volcanic centers. We couple these results with isopachs, paleocurrent datasets, sandstone petrography, and compiled detrital zircon U-Pb geochronology datasets to explore the spatio-temporal evolution of exhumation and foreland sedimentation in the Alberta foreland basin.