Sedimentary structure of the Nansen and Amundsen basins, Arctic Ocean

The first continuous multichannel seismic profile to investigate the deeper structure of the western Nansen Basin was acquired in 2001 with the German and US icebreakers RV Polarstern and USCGC Healy. The 550-km long profile provides detailed insight into the deeper structure of this part of the Arctic Ocean. The sediments are up to 4.5 km thick close to the North Svalbard margin. The sediments thin continuously towards the north. The topography of the oceanic basement in the Nansen Basin is very rough, and it crops out north of 84 degrees 43' N 22 degrees 05' E. Here, it prevents the deposition of thicker sediment units. The rift valley of the Gakkel Ridge, with water depths around 4830 m, was crossed at 85 degrees 36' N 16 degrees 41' E. The top of the basement along the profile can be fit by a theoretical subsidence curve. In the Amundsen Basin, sediments are only 1.7 - 2.0 km thick and oceanic basement younger than chron 13 shallows abruptly some 100 km north of the median valley. The contrasting basement structures are related in our interpretation to the differing depositional histories of the two basins, and to asymmetric spreading in Cenozoic times.