Precambrian metamorphic complexes in the East Greenland Caledonices (72°–74°N) – their relationship to the Eleonore Bay Group, and Caledonian orogenesis

Abstract

Results are presented of regional geological reconnaissance and local detailed studies. The new fjeld work, together with isotopic studies, has made possibie a provisional reassignment of metamorphic, plutonic and deformational events recorded in the different rock units to Archaean and Proterozoic, as well as Caledonian, orogenic episodes. The infracrustal elements of the 'central metamorphic complex' are considered to be essentiaIly Archaean - early Proterozoic basement gneiss complexes, and are overlain by middle Proterozoic metasedimentary sequences. The late Proterozoic and Lower Palaeozoic sediments have arestricted outcrop at present levels of exposure. During the Caledonian orogeny the late Proterozoic cover sequences appear to have become detatched from their older metamorphic 'basernent' along a decollement surface, but the nature of this contact is usually obscured by Caledonian metamorphic effects. The main characteristics of the different rock units are described. Detailed relationships are illustrated by studies of four areas: Nunatakgletscher-Eremitdal, Knækdalen and adjacent areas, Kap Hediund, and Tærskeldal-Forsblads Fjord-Randenæs.