CONTROLS ON LATE QUATERNARY SEDIMENTATION OF THE SOUTH TASMAN RISE

The South Tasman Rise is a submarine continental plateau of about 1000 -3000 m depth, in the Southern Ocean south of and separated from Tasma nia by a saddle more than 3000 m deep. Its palaeoceanographic importan ce is that it lies between the subtropical convergence and the polar f ront and that latitudinal migration of these oceanographic features sh ould be recorded in the calcareous oozes deposited on the rise. Late Q uaternary sediment cores collected from the South Tasman Rise record c limatically and current-controlled changes in sedimentation. Accelerat or mass spectrometry C-14 dating of down-core variations in the carbon ate concentration demonstrates that the core-top carbonate maxima are Holocene and down-core minima are successive glacial intervals. During glaciations the percentage of carbonate decreases, whereas the percen tage of detrital minerals (terrestrial input) increases. The magnitude of climatically related signatures expressed in the sediments is a fu nction both of proximity to terrestrial input from the north and of ov erlying water depth. Cores from the saddle separating the South Tasman Rise from Tasmania have large terrestrial input and high variations i n carbonate concentration. Shallower water cores from the rise are con sistently and strongly influenced by winnowing in both glacial and int erglacial intervals, whereas deeper cores appear to be more influenced by carbonate dissolution during glaciations.