Tectonic evolution of the Precambrian basement and structural analysis of the Western Canada Sedimentary Basin in southern Alberta, from seismic reflection and potential-field studies

Deep seismic reflection profiling of the Southern Alberta crystalline basement, namely the Archean Medicine Hat Block (MHB), is integrated with potential-field studies (bandpass filtering and gravity modeling) and published geochronological and surface geological data. Integration of these datasets has revealed that the crust is characterized by west- and southwest-dipping reflection fabrics, a layered lower crust and geometric cutoffs that are interpreted to be remnants of two episodes of continental collision in the Late Archean and Early Proterozoic. MHB potential-field fabrics are terminated to the north by anomalies associated with the Early Proterozoic Vulcan structure and to the east by those related to the Early Proterozoic Trans-Hudson orogen. MHB dipping basement fabrics are interpreted to have reactivated and controlled the positions of significant extensional faults within the Western Canada Sedimentary Basin in the Paleozoic and Mesozoic. Late Cretaceous to Paleocene(?) extensional faulting in the Phanerozoic strata occurs as far as 140 km east of the triangle zone and is interpreted to be associated with thrust loading during the Laramide orogeny.