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.
Highlights
Geological mapping and isotopic investigations demonstrate that the Grandjean FjordBessel Fjord region ean be divided into three rock groups: (I) a Lower Proterozoic basement gneiss complex; (2) aMiddle Proterozoic supracrustal cover (Smallefjord sequence); and (3) Upper Proterozoic metasediments (Eleonore Bay Supergroup)
The part of the East Greenland Caledonian fold belt between Grandjean Fjord and Bessel Fjord (75°-76°N; Fig. 1) comprises the northem part of the 'Grandjean Fjord metamorphic complex' of Haller (1970, 1971). This incorporates a metamorphic complex of infracmstal and supracrustal rocks, which occurs on both sides of the graben-like enclave of Upper Proterozoic Eleonore Bay Supergroup (EBG) rocks centred on Ardencaple Fjord and Bredefjord (Fig. 1)
Infracrustal rocks occur in an arcuate belt running from the inner part of Grandjean Fjord northwards along the margin of the Inland Ice to inner Bessel Fjord, curving to follow the north side of Bessel Fjord
Summary
Topic data, which place constraints an the ages af these correlations with ather parts af the Caledonian belt in units, this allows critical evaluation af passibie regional East Greenland. I)PC" 111 Ihe I:.Jnar MIUeI-.ell Glel!oChcr - Be
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