Quaternary ostracods as palaeoceanographic indicators: a case study off southern Australia

Abstract

Abstract There is increasing use of ostracods in palaeoceanographic interpretation, yet few comparisons have been made with existing foraminiferal indicators. This paper examines ostracod records from two cores taken off southern Australia and compares them with foraminiferal records of abundance and dissolution. Core E55-6 from the continental margin of Victoria is located in 2346 m water depth. Core E27-30, located south of Tasmania in a water depth of 3552 m, lies to the north of the present position of the Subtropical Convergence. While benthic foraminiferal abundances parallel ostracod abundances in core E55-6, this is not the case in core E27-30. In the latter core, peaks in ostracod abundance are offset from peaks in foraminiferal abundance. This is attributed to high phytodetrital input associated with the Subtropical Convergence. An ostracod-based dissolution index is compared with foraminiferal dissolution data from both cores. The ostracod dissolution index shows greater sensitivity than foraminiferal fragmentation in water depths well above the lysocline and suggests that carbonate dissolution at these depths may be underestimated using foraminiferal indices. The impact of dissolution on ostracods can also be seen as a reduction in abundance. This is evident in both cores, although the impact is greater in the shallower core, suggesting that carbonate saturation may be a factor in the distribution of ostracods in the deep sea. Further investigation of the effects of carbonate saturation on individual ostracod taxa will enhance their utility as palaeoceanographic tools.