The crustal structure of Central East Greenland:results from combined land-sea seismic refraction experiments

Abstract

Summary We present results from the first combined marine–land seismic refraction survey in the area of the East Greenland Caledonides, together with gravimetric measurements. The seismic and gravimetric models show a consistent picture of the crustal structures. In the western area, which is part of the Caledonian mountains of East Greenland, crystalline rocks with P-wave velocities of about 5.5 km s− 1 occur at the surface. Seismic velocities increase continuously with depth and reach values of 6.6 km s− 1 at 12 km. The total thickness of the crust as revealed by the seismic measurements reaches high values of up to 48 km in the southwestern part of the region (28° W). Gravity data, which also cover the region west of the seismic lines, indicate a possible further increase of the crustal thickness. These high values raise questions about whether they represent a Caledonide crustal root, which would stand in strong contrast to the findings in the Caledonian areas of Europe, or whether the crustal thickening represents a pre-Caledonian structure and is affine rather to the older regions west of the Caledonides and adjacent to the Greenland inland ice. Towards the east crustal thickness decreases rapidly. It reaches a minimum of 22 km under the Late Palaeozoic–Mesozoic sedimentary basin of Jameson Land. The crustal thinning is the result of the stretching of East Greenland, which was produced by a general extensional tectonic regime and the collapse of the Caledonian mountain chain from Devonian time onwards. In the area of transition from thick to thin crust, the seismic data indicate a layered structure at the Moho. This region is interpreted as a zone of extensive intrusion or underplating during the rifting in the Tertiary.