Low-latitude Plio-Pleistocene temporal abundance variations in the radiolarian Cycladophora davisiana Ehrenberg: stratigraphic and palaeoceanographic significance

Abstract

Abstract The abundance variation of the radiolarian Cycladophora davisiana was recorded throughout the Plio-Pleistocene Olduvai Time-slab of Ocean Drilling Program (ODP) Sites 677, 709, 847, 850 and 851, in the equatorial Pacific and Indian Oceans. Data were plotted on independently erected timescales. Twelve peak-abundance events were recognized, although not all events were recognized at all the sites. Most of the events, where they are recorded at different sites, were synchronous. However, events recorded at Site 709 in the Indian Ocean were found to be approximately 15 ka older than those events recorded at Pacific sites. This age difference may be due to either diachronous C. davisiana events or a slight inaccuracy in the erected timescale for ODP Site 709 compared with those of the eastern Pacific. The previously demonstrated synchroneity of C. davisiana events in the Late Quaternary leads us to believe that the ODP Site 709 timescale may be inaccurate. Thus, recognition of correlatable C. davisiana events in the equatorial Pacific and Indian Oceans permits the further evaluation and fine-tuning of high-resolution timescales, enabling accurate comparisons to be made of sediment sequences on a regional, and possibly oceanic and interoceanic scale. Of the 12 C. davisiana events recognized, only one event occurred at all the investigated sites. This event occurred at c. 1.8 Ma and immediately above the internationally defined Pliocene-Pleistocene boundary, and may thus prove to be a new useful biostratigraphic marker for the Tertiary/Quaternary boundary. C. davisiana is primarily characteristic of high-latitude water masses, therefore the cyclical abundance peaks of this species noted at the low-latitude sites investigated here, represent the injection of deep cold water of high-latitude origin.