STRUCTURE OF THE BEAUFORT SEA CONTINENTAL MARGIN

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Abstract
An airlifted gravity survey was conducted in 1968 in the Beaufort Sea between Barter Island and Banks Island, south into the Mackenzie River Delta area and northward to about 74° latitude. The 1968 gravity data were combined with data from previous airlifted surveys and ice island T‐3. The major feature of the free‐air anomaly gravity map of this area is a more or less continuous 100 mgal high paralleling the coast from Barrow, Alaska, to the edge of the survey area north of Banks Island. The gravity high is explained by a thinning of the crust and a ridge in the basement rocks at about the 200 m isobath. This linear anomaly is broken by saddles off the Colville, Mackenzie, and Bernard Rivers, which are interpreted to reflect sedimentary fans built by the discharge of these rivers. Two‐dimensional crustal models constructed from gravity profiles indicate a narrow transition zone from ocean to continental crustal thickness, 55 km to 100 km shoreward of the 2000 m isobath. In a review of continental margin structure, Worzel (1968) found the transition zone to be centered under the 2000 m isobath. The departure from “normal” in the Beaufort Sea area may be explained by a greater accumulation of sediments seaward of the “structural” continental margins. This accumulation implies a faster rate of sedimentation and/or a greater age for the Beaufort Sea continental margins than for those analyzed by Worzel.

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