New Constraints on Crust and Mantle Structure Surrounding the Beaufort Sea, Western Canadian Arctic

Date: 4/26/2019

Time: 06:00 PM

Room: Grand Ballroom

The formation and evolution of the western Canadian Arctic Archipelago represents a long-standing tectonic puzzle. The eastern Beaufort Sea juxtaposes young Arctic Ocean with Paleo-Proterozoic Canadian Shield. Controlled source off-shore seismic data suggest that Banks Island represents the western edge of the rifted margin established during the opening of the Arctic Ocean. In this scenario rifting caused Banks Island to subside and accumulate sediments rich in petroleum source material. Conversely, surface-wave based velocity models of North America indicate velocities at 100-150 km depths similar to those beneath Canada’s diamond mines in the central Slave craton. These results suggest Banks Island basement is part of the Canadian Shield and any kimberlites are promising diamond candidates. Furthermore, the southern Beaufort Sea Mackenzie Delta margin represents a well-developed fold and thrust belt <=65 Myrs old but has only been recently recognized as likely active. This belt accommodates either slow thrusting of continental crust over the oceanic crust, or underthrusting of the oceanic crust beneath the margin.

We exploit data from new land seismic networks to investigate crustal structure and seismicity of the Beaufort Sea and surroundings. A key question is how mantle structure typical of the Canadian Shield is reconciled with crust of a rifted passive margin. Specifically, inference of thick cratonic-like lithosphere underlying Banks Island is incompatible with a tectonically disrupted and thinned margin of the Canada Basin. Preliminary results of crust and mantle structure from dispersion analysis, 1D inversion, and receiver function analyses, indicate a ~30 km deep Moho beneath the Beaufort Sea and Banks Island, with slight thinning northwards towards Prince Patrick and Melville Islands. Mantle velocities remain elevated, indicative of cooler lithosphere. Anisotropy orientations from SKS splitting indicate margin parallel fabrics, perpendicular to those expected for a tectonically extended margin; however, their source depths remain elusive.

Presenting Author: Andrew J. Schaeffer

Authors