The pleistocene calcareous nannoplankton of the subantarctic Pacific Ocean

Abstract

The stratigraphic distribution and relative frequencies of Pleistocene calcareous nannoplankton from eight subantarctic cores and one subotropical core have been determined. The extinction and first appearance of certain species allow the division of the Pleistocene into four zones. Two have been previously descibed ( Emiliania huxleyi and Gephyrocapsa Zone), one, the Cocclitius doronicoides Zone, is new, and another, the Pseudoemiliania lacunosa Zone, is redefined. Extrapolation from excess thorium-230 dates, and previously determined and dated radiolarian permit the dating of two nannoplankton zonal boundaries. The age of the Pseudoemiliania lacunosa/Gephyrocapsa datum is estimated at 520,000 to 580,000 years. The age of the Gephyrocapsa/Emiliania huxleyi datum in the subantarctic, is estimated at about 150,000 years. During the last 400,000 years, in the subantarctic, interglacial conditions have resulted in relatively high frequencies of Cyclococcolithus leptoporus and Coccolithus pelagicus. During glacial stages very low frequencies of these two species occured and the dominant coccolithophorid was the eurythermal Gephyrocapsa caribbeanica. A G. caribbeanica maximum, which occured at about 400,000–500,000 years ago and resulted in a coccolith ooze, is apparently due to optimum conditions attained during the relatively intense warming of the early ‘V’ interglacial zone of Ericson and Wollin (1968).