The crystalline rocks of East Greenland between latitudes 74°30' and 75°N

Abstract

Morphologically the Svejstrups area consists of two well-defined units, namely a peneplain surface at an altitude of from 1,000 to 1,500 m, and a system of fjords and related valleys. The peneplain slopes gently eastwards and is terminated in the coastal area by a series of north-south trending faults sometimes marked by prominent scarps. The fjords originated by glacial erosion along pre-existing river valleys; their formation cannot be ascribed to any direct tectonic causes.
The peneplain surface is covered by small ice-caps, remnants of a once continuous ice -sheet. The glaciers descending from these ice-caps are all retreating as is shown by abandoned moraine and other phenomena.
The amount of regression from the maximum advance position in postglacial times (probably late 18th. or early 19th. century) varies from 200 to 1200 m with an average of 700 m.
Crystalline rocks in this part of North-East Greenland occupy much of the country extending from the coast westwards to the inland-ice. Mesozoic sediments and Tertiary volcanics veneer the crystalline rocks of Clavering, Sabine, Pendulum, and Kuhn islands, and on Wollaston Forland.
Three main series of crystalline rocks are distinguished, namely the Basement Series, Tyroler Series, and the Eleonore Bay Formation (youngest). In the Kejser Franz Josephs Fjord region the Eleonore Bay Formation underlies fossiliferous Cambrian beds and has generally been accepted as of young Pre-Cambrian age. The sediments (now meta-sediments) of the Tyroler Series may also be of young Pre-Cambrian age.
The Basement Series consists predominantly of hornblende and hornblende-biotite orthogneisses and amphibolites. Meta-sediments are of subordinate occurrence. The Tyroler Series consists of psammitic and pelitic schists, subordinate calc-schists and limestones, and orthogneisses and schists. The Tyroler Series seems to show lithological equivalence to the Gregory Series of the Kejser Franz Josephs Fjord. The orthogneisses of the Svenstrups area can be closely matched by Scottish Lewisian types, the meta-sediments by rocks of the Moine Series.
The gneisses and schists of the Tyroler Series were formed during the Caledonian orogeny. The Basement gneisses were probably formed in Pre-Cambrian times and later affected by Caledonian folding.
The Caledonian movement was towards the west and overfolding occurs in this direction. In the Tyrolerdal and central Svejstrups Dal the gneisses and schists are disposed in a series of major open folds, the average distance between the fold-axes being 3-5 km. The fold-axes trend between N.E. and N.N.E. and pitch at angles of 5° to 30°. The dominant feature of the structure is the Payers Land syncline which extends from south Payers Land to at least as far as the Svejstrups Dal. The western limb of the syncline dips gently eastwards; the eastern limb is overturned. The syncline pitches gently towards the S.S.W. and brings in the Eleonore Bay Formation in south Payers Land and Stenos Land.
Post-crystalline thrust movements, of late Caledonian age, have occurred in the Svejstrups area and throughout the Caledonides of East Greenland. Post-Devonian normal faults with a general N.-S. trend intersect the crystalline block dropping it down towards the east. These faults are often marked by scarps.
The crystalline rocks of the Svejstrups area lie within a regional injection complex of Caledonian age. Within the complex the schists and gneisses have been soaked and injected by granitic material and pass into coarsely crystalline composite or migmatitic gneisses. Transgressive intrusions of pegmatite, aplite, and granite are of widespread occurrence. The regional injection took place in part contemporaneous with the Caledonian folding and before stress had ceased.
Metamorphism in the Svejstrups area is the result of increase of temperature, connected with the rise of granitic material, combined with contemporaneous Caledonian orogenic deformation. In the schists outside the injection complex almandine garnet is the characteristic mineral, and within it, sillimanite. Injection and metamorphism increase downwards. Uninjected phyllites, limestones and other weakly metamorphosed rocks of the Eleonore Bay Formation grade downwards into sillimanite gneisses and schists and other high grade regionally injected rocks of the Tyroler Series.