TEMPORAL AND SPATIAL EVOLUTION OF UPPER CRETACEOUS-PALEOGENE SEDIMENT PROVENANCE: CORDILLERAN PROCESSES REFLECTED IN THE ALBERTA BASIN, CANADA

The Upper Cretaceous-Paleogene stratigraphic wedge of the Alberta foreland basin records the final major contractional period of uplift and deformation in the Canadian Cordillera. Recent work has emphasized the usefulness of U-Pb geochronology to better constrain orogenic belt uplift and denudation based on the analysis of sedimentary units in the associated foreland. In this study, we employ detrital zircon geochronology to consider: (1) The relationship between Cordilleran tectonics and associated foreland strata during the final stages of Rocky Mountain development; (2) The provenance of Cretaceous-Paleogene wedge sediments; and (3) The relative timing of events in the orogen and the foreland basin. Geochronology data are subject to statistical similarity analysis and considered with respect to detrital spectra of potential source regions and recently obtained thrust-fault ages.

Cretaceous-Paleogene strata of the Alberta basin (N = 15 samples; n = 3176 dates, total) cluster into 4 distinct groups using statistical analysis, which are largely distinguished based on proportions of recycled North American passive margin-derived ages and Cordilleran Mesozoic ages. We interpret detrital zircon spectra trends in the foredeep to record the progressive erosion of a thick succession of orogenic wedge-top strata, beginning at ca. 81 Ma. A flux of recycled material within the K-Pg stratigraphic wedge, characterized by a diverse passive margin spectra, was coincident with thrusting (72.3-75.6 Ma) based on recently acquired radiometric fault gauge ages. We interpret this to record a major phase of orogenesis in the hinterland (ca. 76-68 Ma). We infer a lag period between the end of hinterland thrusting and the exposure of orogenic wedge passive margin strata to be a minimum of 4 Ma. Collectively these data provide important insight into hinterland uplift and denudation during the final stage of Cordilleran development.