Late Quaternary palaeoceanography of the Tasman Sea: the benthic foraminiferal view

The benthic foraminiferal content of four gravity cores from the East Tasman Plateau (2450 m and 2667 m water depth) and the Lord Howe Rise (1349 m and 1448 m water depth) was examined in order to determine Late Quaternary palaeoceanographic changes in the Tasman Sea. cores, benthic foraminifera demonstrate the glacial/interglacial cyclicity through changes in assemblages and abundance. Abundances range from about 400 to 1200 specimens per gram of dry sediment over the last 400 kyr. Abundance patterns differ between the northern (between 31°S and 33°S) and the southern sites (between 43°S and 44°S). In the southern cores a significantly increased benthic foraminiferal abundance indicates high nutrient flux (and quality perhaps) continuously during Stage 5. The northern cores, on the other hand, display this signal for Stage 6. This reversed pattern is recognizable for other glacial episodes, as well as for interglacials, but the trend is less distinctive. ed sea-surface productivity in the Tasman Sea during the last glacial cycle is recognized from benthic foraminiferal assemblages, but the pattern appears highly variable and complex. The data suggest that for the past relocation of Recent high productive oceanographic features (sensu Yoder et al., 1994) in the Tasman Sea such as the Tasman Front, the Subtropical Convergence, the East Australian Current and perhaps the East Australian Eddy Field (Tranter et al., 1982), are reflected in the benthic formainiferal abundances in the cores. Increased foraminiferal abundance during glacials on the Lord Howe Rise indicate a slight northward shift of the Tasman Front. Data from the East Tasman Plateau show a more complex situation. The faunal pattern in the cores probably reflect a southward shift of the eddy field during glacials and a slight northward shift of the Subtropical Convergence during interglacials.