Aerogeophysical Evidence for the Rotational Opening of the Canada Basin

By

J.M. Brozena (Naval Research Laboratory), L.A. Lawver (University of Texas), L.C. Kovacs, and V.A. Childers (Naval Research Laboratory)

The availability of airborne gravimetry motivated the Navy’s return to the Arctic to augment previous long-range aeromagnetic surveys of the ice-covered ocean basins. Additionally the new aerogeophysical surveys densify and obliquely cross the old tracks, allowing for a joint magnetics leveling. The improved maps provide insights into the tectonic evolution of the region.

The gravity over the Canada Basin shows the same general structures as seen in the ERS derived gravity, but with somewhat better resolution. The linear central gravity low is located asymmetrically eastward of the center of a broad, wedge-shaped high in the center of the southern Canada basin. A bilaterally symmetric pattern of magnetic lineations 300 km wide flank the gravity low, strengthening the claim that this represents an extinct spreading axis. However, the fossil axis appears to have propagated southward into the basin replacing an earlier spreading center to the west. The asymmetry in location of the fossil axis with respect to the margins and the high gravity wedge are explained by this change in spreading pattern. The magnetic and gravity fabric changes again in the region between the Alaska margin and the southern Chukchi Borderlands, implying at least three stages of opening. In spite of the complexities, the overall pattern is consistent with the formation of the southern Canada Basin by rotation of the North Slope away from the Canadian margin, initially around a pole near the Mackenzie Delta, then some 500 km to the southwest, and finally 500 km south of the Delta.

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.