Seismic stratigraphy and sediment thickness of the Nansen Basin, Arctic Ocean

Abstract

SUMMARY A Norwegian expedition to the western Nansen Basin, Yermak Plateau and the Hinlopen margin in 2001 acquired about 1100 km of 2-D multichannel seismic profiles and 50 wideangle sonobuoy record sections. Analysis of these data establishes a regional seismic stratigraphic framework for the western Nansen Basin integrating previously published stratigraphic schemes. P-wave velocities and sediment thickness were derived within 7–8 per cent uncertainty from 2-D seismic ray tracing models of each sonobuoy section. Sediment thickness reaches 2 km in the studied area and increases towards the depocentre of the giant FranzVictoria fan on the Barents–Kara continental margin. High-relief oceanic crystalline crust with 3.7 km s −1 average near-top velocity is infilled by four seismic sediment units with typical velocities 2.4, 2.2, 2.0 and 1.8 km s −1 . A prominent regional seismic horizon between units 2 and 3 is tentatively correlated by basement onlap and sedimentation rates to a Miocene (∼10 Ma) palaeoceanographic event, possibly the opening of the Fram Strait. The youngest unit is correlated to prograding sequences on the margin and to the onset of major slope failure caused by intensified glacio-fluvial drainage and ice sheet erosion during Northern Hemisphere glaciations (2.6–0.01 Ma).