Abstract

The post-Caledonian basins of East Greenland were initiated by rifting in Carboniferous and Permian time. The tectonic activity increased through Mesozoic time and a number of well-dated tectonic phases can be recognized. Active sea-floor spreading finally occurred in late Paleocene time.

The Mesozoic rift is orientated north-south. It is cut by major NW-SE cross faults and opened in the Jurassic from the south by progressive downfaulting of blocks. The combined effect of the tectonism and of eustatic sea-level changes was a stepwise basin extension and submergence of the rifted basin. Triassic rift deposition was mainly continental and the Triassic-Jurassic boundary was characterized by a change from arid to humid climate and from continental to marine deposition. During Jurassic time the environments changed from a tidal bay over a shallow siliciclastic shelf sea to a wide muddy shelf. An important tectonic episode at the Jurassic-Cretaceous boundary resulted in fragmentation and collapse of the shelf by antithetic block-faulting, and coalescent submarine fans were formed along the fault scarps.

The Aptian sea transgressed an irregularly erosional relief surface and the remaining part of Cretaceous time was characterized by outer shelf and slope mudstones interrupted by deposition of coarser elastics during periods of block faulting. The Tertiary rocks comprise pre-drift sediments overlain by 1-7 km of late Paleocene basaltic lavas extruded immediately prior to active spreading. Subsequent subsidence of the shelf led to accumulation of 2-8 km of post-basaltic sediments offshore whereas the land area was uplifted 1-2 km. Initiation of spreading along the Kolbeinsey Ridge during late Oligocene time was accompanied by renewed tectonism within the middle part of the margin. Finally the shelf was characterized by strong progradation during Miocene time.