Post-orogenic tectonic and thermal history of a rifted continental margin: the Scoresby Sund area, East Greenland

Abstract

Fission track (FT) analysis of zircon, sphene and apatite from crystalline basement in the Scoresby Sund area, East Greenland, and FT modelling reveal information about the cooling and uplift paths for individual tectonic blocks since the Caledonian orogeneny. Up to c. 325 Ma the area cooled and behaved as a single unit. However, it subsequently broke into several fault-bounded blocks, each block moving independently of adjacent blocks. Net uplift since 325 Ma was of a similar magnitude (8 km, assuming a geothermal gradient of 30°C/km) along the crest of the Devonian fault zone for the southern blocks, but about 9 km for the Stauning Alper; and these blocks were probably tilted away from the rifted continental margin. The relief evolution accompanying uplift in the Caledonian basement is closely related to Mesozoic basin formation, subsidence and infilling in the area. FT modelling reveals fast cooling from c. 70°C to surface temperatures during the last 55 m.y., probably as a result of Tertiary rifting and magmatic activity in the area.