Sediment deposition in the northern basins of the North Atlantic and characteristic variations in shelf sedimentation along the East Greenland margin

New seismic data off East Greenland were acquired in the summer of 2002, between 77 degrees N and 81 degrees N, north of the Greenland Fracture zone. The data were combined with results from the Greenland Basin and ODP site 909, and indicate a pronounced middle Miocene unconformity within the deep sea basins between 72 degrees N and 81 degrees N. Seismic unit NA-1 consists of sediments older than middle Miocene age and unit NA-2 contains sediments younger than the middle Miocene. Classification of a thinly bedded succession in the Molloy Basin resulted in a subdivision into four units (unit I, unit II, unit IIIA and unit IIIB). A comparison of volume estimations and sediment thickness maps between 72 degrees N and 81 degrees N indicates differences in sediment accumulation in the Greenland, Boreas and Molloy basins. Important controls on the variation of accumulation included different opening times of the basins, as well as tectonic conditions and varying sources of sediment transport. Due to prominent basement structures and the varying reflection character of the sediments along the entire East Greenland margin, we defined an age model of shelf sediments on the basis of similar sediment deposit geometry and known results from other regions. The seismic sequences on the shelf up to an age of middle Miocene are divided into three sub-units along the East Greenland margin: middle Miocene-middle late Miocene (SU-3), middle late Miocene-Pleistocene (SU-2), Pleistocene (SU-1). The differences in the geometry of the sequences show more ice stream related sedimentation between 72 degrees N and 77 degrees N and more ice sheet related sedimentation north of 78 degrees N. The region south of 68 degrees N is dominated by more aggradational sedimentary strata so that a glacio-fluvial drainage seems the main transport mechanism. Due to the Greenland Inland-ice borderlines, we assume the glaciers between the Scoresby Sund and 68 degrees N did not reach the shelf break. A first comparison of the sediment structure of the Northeast Greenland margin with the Southeast Greenland margin made it possible to demonstrate significant differences in sedimentation along this margin. (C) 2009 Elsevier Ltd. All rights reserved.