Amundsen Sea sediment drifts: Archives of modifications in oceanographic and climatic conditions

Drift deposits document stages of particular dynamic bottom-currents and associated sedimentary transport activities. The analysis of seismic reflection data from the Amundsen Sea, southern Pacific Ocean, reveals sediment drift formation already in Eocene/Oligocene times. This observation indicates bottom current activity and hence a cold climate for the late Palaeogene in an area, which today lies under the influence of Antarctic Bottom Water (AABW) originating in the Ross Sea. The generation of sediment drifts is accompanied by the occurrence of mass transport deposits leading to the identification of a phase of strong ice sheet expansion (15–4 Ma), which due to a change in ice regime from wet- to dry-based was followed by less material input during the last ~ 4 Ma.

► Four depositional stages related to changes in oceanography/climate for the Cenozoic.
► Sediment drifts indicate bottom current activity already in Eocene/Oligocene times.
► Intensified bottom currents during the period 21–15 Ma.
► Increased sediment input following 15 Ma represents the major onset of glaciations.
► A change in ice regime from wet- to dry-based after 4 Ma