Post-collisional extension of the East Greenland Caledonides: a geophysical perspective

Abstract

Crustal extension during and following continental collision is well documented in the Arctic Caledonian fold belt. However, models for the post-collisional extension of the Caledonides are mainly based on geoscientific data from Scandinavia. For a more complete understanding of the evolution of the Caledonides, knowledge of the crustal structure of East Greenland is vital. Seismic and gravity studies have revealed a pronounced Moho topography and a west-dipping lower crustal reflector beneath the fjord region of East Greenland. These deep crustal structures are related to Late Caledonian extensional structures at the surface. The observations can be satisfactorily explained by applying simple shear or eduction models proposed for upper crustal extension in Scandinavia to the complementing lower crustal structures in East Greenland. However, exhumation of the Caledonian Northeast Greenland eclogite province cannot be accomplished by these models. Instead, a synthesis of geoscientific data has shown marked differences in the crustal structure of East Greenland north and south of about 76°N, indicating a different crustal evolution of the northern and southern parts of the East Greenland Caledonides.