Geometrical and geological analysis of photogrammetrically measured deformed sediments of the fjord zone, central East Greenland

A mathematical modelling of folded surfaces has been developed. It involves the splitting of indivicual folds into approximately conical or cylindrical segments, projection of the surfaces of each fold segment onto a profile plane perpendicular to the fold axis, and approximation of each surface projection with a polynomium. When the surfaces have been modelled, best fitting deformation parameters for the fold segment can be calculated, assuming a simple deformation history for the fold. This involves first flexural slip folding, thereafter similar folding, and last.k homogeneous compression.

Computer programs have been developed that allow use of this modelling on folded surfaces measured via the Kern PG2 stereo restitution instrument of the Grønlands Geologiske Undersøgelse.

An area of Upper Proterozoic to Lower Palaeozoic sediments in central East Greenland, folded during the Caledonian orogeny, has been photo-interpreted and structurally analysed. Major north-south directed folds, east-west striking faults, and west-dipping low-angle tension faults are thought to be related to a westward translation of the sediment packet of at least 25 km during the Upper Ordovician. It is concluded, that the driving force behind the translation was gravity.

Major faulting in the western part of the area is related to a basement uplift of Middle Devonian age. En echelon folds, slides and crescent-shaped faults in the north-eastern part of the area may be related to dextral strike-slip faulting along the margin of the future Gauss Basin. Together these movements formed the relief present during the deposition of the Upper Middle Devonian Vilddal Supergroup