Restoring thrusting in the East Greenland Caledonides

Abstract

Three principal lithostructural domains are recognized within the southern part (70°–76°N) of the East Greenland Caledonides. At the deepest structural levels, within foreland windows, a thin Neoproterozoic–lower Paleozoic succession unconformably overlies older basement. The foreland is overridden by two major thrust sheets, a lower and an upper thrust sheet. Each of these comprise Paleoproterozoic or older crystalline basement rocks and their metasedimentary cover, and preserve evidence of both a pre-Caledonian (ca. 930 Ma) thermal event and the superimposed Caledonian orogenesis. Transport directions on major thrusts are top-to-the-west-northwest, and restoration of displacements with respect to the foreland windows permits reconstruction of a 500–700-km-wide sector of the pre-Caledonian Laurentian margin. One implication of the reconstruction is that the 18.5-km-thick Neoproterozoic–lower Paleozoic succession preserved in the upper thrust sheet accumulated in a basin that was at least 200 km east of the foreland where the equivalent succession totals only 250–400 m. Scandian (ca. 430 Ma) thrusting resulted in 40%–60% shortening to produce the present ∼300-km-wide orogenic belt in East Greenland.