The Canada Basin: Aeromagnetic constraints on structure and evolution

Abstract

Aeromagnetic data over the Canada Basin and Alpha Ridge-Ellesmere Island junction are re-examined together with available bathymetry, free-air gravity and magnetic source depths calculated from the aeromagnetics. The plate tectonic evolution of this area remains largely conjectural; for example, the data from the basin and the adjacent continental margins have not settled the Alaska rotation controversy. Did the Canada Basin open by a rotation of the Alaska and Chukchi blocks away from the Canadian Arctic margin, or did the southern Canada Basin open by motion of the Chukchi block parallel to the Alaska North Slope? What we do conclude is: 1. (1) The southern Canada Basin consists of oceanic crust produced by spreading from a now-extinct axis marked by a gravity high and magnetic low. The opening took place largely or entirely during the time of the M-Series (155-115 m.y. B.P.) although the lineations are too few and too irregular to allow certain correlation to the reversal time scale. 2. (2) The central Canada Basin, north of Prince Patrick Island, probably opened by spreading normal to the margin. The segmented character of the magnetics and perhaps topography, suggests small transform faults (ca. 100 km spacing) extending at least several hundred kilometers into the basin. If these trends are real, major subsequent motion parallel to the Canadian Arctic margin can be ruled out. 3. (3) We speculate that the southern Canada Basin extinct axis extended to a triple junction near 79°N, 140°W, with one rift trending toward Ellesmere Is and the other into the Mendeleev Abyssal Plain. 4. (4) The transition between the low magnetic amplitudes of the southern Canada Basin to the high amplitudes of the northern Canada Basin-Alpha Mendeleev Ridge province is gradual and linear anomalies extend through the transition. 5. (5) The area north of Ellesmere Island can be divided into five discrete magnetic anomaly provinces, some of them sharply demarcated by major lineaments (faults?) which may provide plate kinematic constraints. The Alpha Ridge basement is depressed by 3–4 km along a 100 km wide magnetic basement trough along the Alpha Ridge-Ellesmere Is. margin.