Mid-Palaeozoic travels of Arctic–Alaska

Abstract

One of the most persistent proposals¹ for the origin of the Arctic sea floor is that Alaska, or parts thereof, broke away from polar Canada and rotated as much as 70° anticlockwise relative to the North American craton. Subsequent modifications^2–8 reduced the size of the rotated block (Fig. 1) and put the date of rotation at latest Jurassic–early Cretaceous (refs 4, 6, 7, 9, 10, and A. Grantz and S. May in preparation). Although restoration of the block provides a good geological fit between northern Alaska and the Arctic islands for late Palaeozoic and younger pre-rift age rocks,⁸ the character of Devonian and older Palaeozoic rocks across the restored boundary is anomalous, with deformed and thermally altered rocks of northern Alaska lying against unaltered sediments on Banks Island (Fig. 2b). Here I compare the known geology of mid-and early Palaeozoic rocks along the margins of the restored rift and explain the anomalous Arctic–Alaska terrane as a block that was displaced southwestwards in mid-Palaeozoic time by as much as 2,000 km from its initial orogenic site to the north and east of Ellesmere Island.