Cartier Furrow, a Major Structure along the Continental Margin of North-western Australia

Abstract

A COMPILATION of recent aeromagnetic surveys in offshore north-western Australia^1–4 (Fig. 1) reveals a furrow in the magnetic basement, which I propose to call the Cartier Furrow, after Cartier Island. The furrow is at least 1,250 km long, and 6 km deep, and is filled with sediment. It underlies the upper continental slope except where it crosses the Londonderry Rise, which is a spur in the continental shelf. The furrow is bounded on its south-eastern side by the offshore Bonaparte Gulf Basin in the north, by the offshore Canning Basin in the south, and, in between, by a prism of non-magnetic rocks which thin south-eastward towards the Pre-Cambrian Kimberley Block. The north-western side of the furrow is marked by the atolls of the Rowley Shoals, Scott Reef, and Seringapatam Reef, which rise from the continental slope; by the outer part of the Londonderry Rise, which is crowned by the reefs of Ashmore Island, Cartier Island and Hibernia Reef; and by the south-east slope of the Timor Trough. From a comparison with onshore surveys in the Bonaparte Gulf Basin, Veevers and van Andel⁵ identified the magnetic basement beneath the Sahul Shelf as either a layer or layers high in the Pre-Cambrian of the Kimberley Block, or Lower Cambrian volcanics. The magnetic basement in the landward part of the Canning Basin⁶, as shown by drill holes, is crystalline Pre-Cambrian rock (granite or metamorphics), so that the magnetic basement offshore probably coincides also with the surface of Pre-Cambrian rocks.