Basement-cover relationships and regional structure in the Grandjean Fjord - Bessel Fjord region (75°–76°N), North-East Greenland

Abstract

Geological mapping and isotopic investigations demonstrate that the Grandjean Fjord – Bessel Fjord region can be divided into three rock groups: (1) a Lower Proterozoic basement gneiss complex; (2) a Middle Proterozoic supracrustal cover (Smallefjord sequence); and (3) Upper Proterozoic metasediments (Eleonore Bay Supergroup). The basement gneiss complex largely comprises c. 2.0–1.7 Ga calc-alkaline granitoid orthogneisses with intercalated migmatitic supracrustal rocks. The complex is deformed by at least two sets of approximately coaxial folds which may be either Proterozoic or Caledonian in age. The Smallefjord sequence is comprised mostly of migmatitic schists and gneisses which underwent high-grade metamorphism during the late Middle Proterozoic. The dominant deformation structures within the Smallefjord sequence are associated with the development of ductile shear zones along the boundaries of all the major tectonostratigraphic units and are thought to be Caledonian in age.