Cordilleran tectonics

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This research aims to elucidate some of the processes involved in the formation of mountain belts as exemplified by the Canadian Cordillera. The focus is on the origin and evolution of the Cordilleran foreland thrust-and-fold belt in southern Canada and northern Montana, which formed during convergence between ancestral North America and subduction zones along its western margin. The thrust-and-fold belt consists of sheets and slices of supracrustal strata that have been scraped off the under-riding ancestral North American continent and its western margin by an over-riding tectonic collage of accreted, mainly ocean-basin, volcanic rocks called "Intermontane terrane". The research involves preparation of "restored" paleogeological structure sections and maps that portray the supracrustal rocks in the locations and configurations in which they existed prior to the thrusting and the folding. Three deep sedimentary basins from which most of the displaced rocks came (Belt-Purcell, Windermere, and Cordilleran miogeocline) will be restored to their original relationships with each other and with the deep crustal structures in the Paleoproterozoic basement of North America that extends under the Cordillera. The reconstructions will be based mainly on geological maps and balanced deep structure sections. Five additional 1:50,000-scale geologic maps, with structure sections and two new regional. deep, balanced structure sections will be completed from available field data to close a critical information gap in the centre of the region. Deep seismic imaging, together with gravity and magnetic anomaly maps, geological maps, and thermochronometric and geobarometric data from metamorphic and igneous rocks will provide constraints on regional and temporal variations in deformation and on the deep crustal and lithospheric structure. Preliminary analyses indicate that the cumulative displacement across the belt is >300 km. The results of this research can be expected to clarify how, when, and why the southeastern Canadian Cordillera and its rich fossil fuel and mineral resources formed, and also to inform the many people whose fascination with the Rockies arouses their curiousity about the mountains came to be.