A seismic and gravity study of the western part of the Cretaceous-Tertiary sedimentary basin of central West Greenland

Abstract

In the summer of 1972 a GGU seismic group working on land measured the thickness of sediments in the western part of the Nugssuaq peninsula, West Greenland, by explosion reflection and refraction seismic methods. In the region crudely bounded by Ikorfat, Ubekendt Bjland and Hareøen Cretaeeous-Tertiary sediments extend about 1-3 km below sea level and rest on the granodioritie gneiss basement. The basin shallows gradually toward the west where it is sharply hidden beneath Tertiary basalts. There is strong evidence for continuity of the Cretaeeous-Tertiary sediments aeross Umanak Fjord as far as Ubekendt Bjland. The most distinctive feature of the basement strueture is a ridge, running roughly N-S through the western part of the area, and rising about 2 km above the deeper parts of the basin. This ridge appears as a northerly continuation of the Disko gneiss ridge. The gravity pattern over a 100 km X 50 km strip centred on the western part of the basin shows rapid westward thinning of the earth's crust, and suggests that the basin has its origin in an incompletely rifted structure marginal to the crustal rifting responsible for Baffin Bay.