DETRITAL ZIRCON GEOCHRONOLOGY OF UPPER CRETACEOUS AND PALEOGENE STRATA, ALBERTA BASIN, CANADA: IMPLICATIONS FOR PROVENANCE AND TECTONIC EVOLUTION
Regional isopach mapping reveals asymmetric sedimentary foreland basin deposits, initiated at the onset of Belly River Group deposition at 78.85 ±1.95Ma. From this time until ~66.8 Ma, thick successions of siliciclastics are preserved in the foreland basin, recording denudation of the uplifted orogenic belt. Detrital zircon geochronology of Cretaceous deposits provide a proxy for the volume of magmatism in the Omineca belt (N = 15 samples; n = 3176 ages, total), indicating a magmatic peak at 73.5 Ma. Peak magmatism 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. Peak magmatism and faulting post-dates initial basin subsidence by 4-6 Ma. Collectively, these data provide crucial age-constraints to processes commonly calculated with numerical models or speculated upon by theoretical models.