Abstract

In the spring of 1973, 3 days of simultaneous geomagnetic observations were obtained at six recording sites over the central Arctic Islands. The northern site, Isachsen, displayed the strong suppression of the amplitudes of short-period temporal variations in the vertical component that has been observed at Mould Bay, about 500 km to the southwest. One-dimensional conductivity models suggest high conductivities in the upper crust. Parkinson's arrows for short periods point to the inter-island channels of sea water but for long periods the arrows rotate to point to the deep Arctic Ocean. A large spatial variation of the in-phase correlated Z/H ratios is also observed along a profile across the central Arctic Islands. These ratios peak at the Cameron Island site, which is near the Sverdrup Basin – Franklinian Geosyncline geological boundary. In well-log resistivity data, a conductivity contrast of two orders of magnitude is observed across this margin. Electric currents therefore flow in the conductive sediments of the Sverdrup Basin and in the sea water in the inter-island channels. The electromagnetic response is similar to that near an ocean–continent margin but the peak response occurs "inland" by 300–400 km. Consequently, the margin of the resistive continent is located near the Franklinian – Sverdrup Basin boundary in the central Arctic Islands.

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