Résumé
The tectonic evolution of the Beaufort Sea continental margin has contributed to the maturation of these rocks into a major petroleum reservoir. Recent shallow offshore seismic reflection data suggest that Banks Island represents thin crust along a rifted margin established during the opening of the Arctic Ocean. In this case, rifting of the margin caused Banks Island to subside and accumulate sediments rich in petroleum source material. The cooling history and further subsidence of these sediments is important for understanding the thermal maturation of petroleum products. Recently published surface-wave velocity models of North America indicate seismic velocities at 100-150 km depths similar to those beneath Canada's diamond mines in the central Slave craton north of Yellowknife. These results imply that Banks Island is part of the Canadian Shield and that any kimberlites found thereon might contain diamonds. However, the fast velocities are inconsistent with this being a tectonically disrupted and thinned lithosphere along the Arctic margin of the Canada Basin. The problem is therefore to reconcile mantle structure typical of the Canadian Shield with crust typical of a rifted passive margin. Possibly related seismicity beneath the Mackenize River Delta and offshore in the Beaufort Sea has been observed for decades but its origin remains unknown, although has been suggested as due to incipient subduction of oceanic lithosphere beneath the North American craton. Resolving these questions requires high-resolution 3-D seismic models obtained from an array of broadband seismograph stations. Here we present preliminary results on the structure of the crust and uppermost mantle underlying the western Canadian Arctic. These results are generated using new data from the Banks Island Seismograph Network (BISN), three stations installed over the summer of 2014 and 2015; augmented with several USArray Transportable Array stations and older POLARIS and CNSN stations on neighbouring Arctic Islands.