THE NORTH GREENLAND FOLD BELT AND ENVIRONS

Abstract

A review of our present knowledge of the North Greenland fold belt and environs is presented. Precambrian crystalline basement, which is exposed at places adjacent to the Inland Ice and can be expected to form larger areas now covered by its northern extremity, is overlain with marked angular unconformity by a Proterozoic to Lower Palaeozoic sedimentary pile. These sediments dip gently northwards forming a platform and hinterland to the North Greenland fold belt which occupies the extreme northern part of Greenland as a roughly E-W zone of deformation and metamorphism. In Peary Land, where the widest part of the zone occurs, the effects of deformation and metamorphism increase northwards towards the assumed centre of the erogenic belt. In eastern Peary Land, the folded Lower Palaeozoic sediments are unconformably overlain by strata of. Pennsylvanian, Permian, Triassic and CretaceousTertiary age. This sequence has been affected by Tertiary earth movements. Field evidence in Greenland, together with evidence from the Innuitian orogenic system in Arctic Canada, suggests that the main Palaeozoic diastrophism affected the sediments of 'the Greenland part of the Franklinian geosyncline between Late Silurian and Late Devonian time. Field work since 1965 on both the.folded and platform rocks of the fold belt has led to a reinterpretation of the structure and stratigraphy of North Greenland. Important results include: 1) the recognition in the western part of the platform of a Palaeozoic reef complex of regional extent with major facies changes between carbonates, and arenaceous and argillaceous sediments, leading to a criticism of the described Silurian unconformities and to a revision of the established Silurian stratigraphical nomenclature; 2) the lowering of the base of the Cambrian in the platform so that rocks which have been previously regarded as Precambrian or Eocambrian (and part of the so-called Thule Group) are now known to be Palaeozoic in age; 3) recognition that the thick Inuiteq So Formation composed of sandstones cut by basic intrusives (which is the oldest unmetamorphosed sedimentary formation in North Greenland) is at least 1000 m. y. old; 4) discovery of both shelly and graptolitic faunas in the folded sediments indicating the presence of Cambrian, Ordovician and Silurian strata in the folded zone; 5) indications that the sediments of the folded zone have passed through a long and complex orogenic history, suffering poly-