Abstract

Canada and the United States collaborated in geophysical survey operations in the Amerasia Basin from 2007 to 2011 using the Canadian icebreaker CCGS Louis S. St. Laurent and the US icebreaker USCGC Healy. Over 15000 km of bathymetry, sub-bottom profiles, and 16-channel seismic reflection data were acquired over the Canada Basin and Alpha Ridge. Expendable sonobuoys were deployed to collect P-wave refraction and wide angle reflection data to define the regional velocity structure of the sedimentary successions. Although the new seismic profiles tie with existing GSC multichannel seismic lines on the Beaufort Shelf, water-bottom multiples obscure direct correlation of deeper stratigraphic horizons and (at best) basement is poorly imaged.

We present a 2-D gravity and magnetic model for the southern Canada Basin margin and Beaufort-Mackenzie Basin integrating the new LSSL data with an existing deep crustal seismic reflection profile. The model crosses the slope region, where bathymetry shallows, base-of-sediments is deep, and basement is not imaged because of the water-bottom multiple. The density values used in the model are constrained by empirical relationships between velocity and density rock properties; however, magnetic susceptibility values are based on typical values for the inferred crustal lithologies. Velocity analyses of the new sonobuoy data provide constraints on the composition of the sediments, and enable quantitative mapping of continental, oceanic, and transitional domains within the Canada Basin. The 2-D gravity and magnetic forward model provides estimates for basement and Moho depths, the distribution and depths of magnetic sources, and visualization of the underlying crustal architecture controlling basin formation.

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