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Abstract

Free-air and Bouguer anomaly maps have been compiled from about 9,000 gravity measurements made throughout the Canadian Arctic Archipelago and the Arctic Ocean. These measurements form part of a major survey of the Arctic being carried out by the Canadian government.

Correlation of Bouguer anomalies with geologic and physiographic features shows that negative anomalies generally occur over sedimentary basins and mountainous regions and positive anomalies occur over fold belts and the ocean basin.

The major feature of the free-air anomaly map is a series of large, positive, elliptically shaped anomalies overlying the continental margin and striking parallel with the continental break. These anomalies, which are approximately 120 km in width and between 150 and 300 km in length, have amplitudes greater than 100 mgal and regional horizontal gradients as large as 2.5 mgal/km. Interpretation of the gravity data, using seismic and geologic data for control, indicates that these anomalies can be explained best by a composite structure consisting of a sedimentary layer up to 10 km in thickness and a crust which thins by as much as 17 km.

The average free-air anomaly of the relatively flat archipelago (mean elevation of 15 m) west of 90°W long, is about 7 mgal; this value indicates that the region is in approximate isostatic equilibrium

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