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Abstract

The Geological Survey of Greenland has completed the first 3 years of a 5-year mapping campaign in the Scoresby Sund region, which includes the southernmost part of the Caledonian fold belt of East Greenland.

The preliminary results show that it is possible to distinguish the following main geologic units in the Caledonian fold belt: (1) a Precambrian crystalline basement with a cover of Precambrian metasedimentary and meta-volcanic rocks; these rocks have been affected to varied degrees by Caledonian folding; (2) a metamorphosed but nonmigmatized supracrustal complex composed of psam-mitic and pelitic rocks containing scattered bands of calcareous rocks and totaling several kilometers in thickness; these rocks represent Caledonian geosynclinal deposits of miogeosynclinal aspect and are probably of very late Precambrian age; (3) a Caledonian infracrustal complex of mainly gneisses, migmatites, and synkinematic granites; this unit was formed by migmatization of Caledonian geosynclinal deposits; and (4) late to post-Caledonian intrusions mainly of granitic type.

Westward-directed thrust sheets with a displacement of several tens of kilometers are present along the western rim of the fold belt. They comprise largely Caledonian supracrustal rocks, but locally basement rocks are also incorporated in the thrust sheets. The central part of the north-south-directed fold belt is characterized by infracrustal rocks with simple low-dipping macroscopic structures; in some parts of the area these structures can be shown to be the limbs of major recumbent folds.

The Caledonian supracrustal rocks in the western part of the region were metamorphosed under high-pressure conditions and are characterized by kyanite-bearing rocks. In contrast, the rocks of the central migmatitic part of the region were formed under low-pressure conditions and are characterized by cordierite-bearing assemblages.

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