New Radiolarian Palaeoclimatic Index in the Plio-Pleistocene of the Southern Ocean

Abstract

PLIOCENE-PLEISTOCENE palaeoclimatic investigations in the Southern Ocean have been carried out using five groups of microfossils: foraminifera^1,2, calcareous nannofossils³, Radiolaria^4–9, diatoms¹⁰, and silicoflagellates¹¹. Radiolarian methods are particularly valuable in higher latitudes where carbonate sediments are susceptible to dissolution even in relatively shallow waters^12,13. Established radiolarian techniques are based on oscillations of cold-water (Antarctic) relative to warmer-water radiolarian assemblages, established by determining their distribution in Recent sediments relative to the Antarctic Convergence (Polar Front)⁴. The cold-water assemblage used in these palaeotemperature determinations consists of eight species, whereas the warm-water assemblage consists of nine species^4,9. Of the several dozen species known in Southern Ocean Quaternary sediments, these seventeen species represent more than 75% of the individuals⁴.