Amundsen Sea deep sea sediments: Archives of modifications in oceanographic and climatic conditions
Deep sea deposits document stages of particular material input, dynamic bottom-currents and associated sedimentary transport activities. The analysis of seismic reflection data from the Amundsen Sea, southern Pacific Ocean, reveals different stages in sediment input from the continent and sediment drift formation. Sediment was input from the continent via three troughs in Eocene/Oligocene times, but we also observe sediment drift formation for this period in the northwestern Amundsen Sea. This observation indicates bottom current activity and hence a cold climate for the late Paleogene in an area, which today lies under the influence of Antarctic Bottom Water (AABW) originating in the Ross Sea. The main depot centre shifted to the northeastern Amundsen Sea with a increased input via the Abbot Trough for the period 21-14.1 Ma, There the material was shaped into sediment drifts, which points towards a SW setting slope-parallel bottom current. This bottom current is also responsible for the formation of sediment drifts in the central Amundsen Sea as the result of a shift in main material input to the Western Pine Island Bay Trough during 14.1.-4 Ma. This was followed by less material input due to a change from wet- to dry-based ice conditions, but maintenance of the sediment drifts, during the last 4 Ma.
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