The last 1 million years of the extinct genus Discoaster: Plio–Pleistocene environment and productivity at Site U1476 (Mozambique Channel)

the Expedition 361 Shipboard Scientific Party

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Abstract

A detailed paleoenvironment reconstruction from the Mozambique Channel, western Indian Ocean, based on the calcareous nannoplankton assemblages was conducted for the interval between 2.85 and 1.85 Myr. This study covers the period during which the successive extinction of the last five species of discoasters occurred. New productivity data obtained from the abundances of the Discoaster species (Discoaster brouweri, D. triradiatus, D. pentaradiatus, D. surculus, and D. tamalis) and other indicative calcareous nannoplankton taxa showed abundance variations, which were at paced with the 100, 41, and 23 kyr astronomical periodicities. A shift in the productivity and water-column stratification proxies occurred at ~2.4 Ma, after the onset of the Northern Hemisphere glaciation. Here we propose that the variability recorded at International Ocean Discovery Program Site U1476 reflects the interplay between forcing associated with warm tropical Pacific and cold southern ocean influences. The former is shown by consistent occurrence of warm water taxa (Calcidiscus leptoporus, Oolithotus spp., Rhabdosphaera clavigera, Syracosphaera spp., Umbellosphaera spp.), typical of Indonesian Throughflow surface waters. On the other hand, the occurrence of Coccolithus pelagicus indicates the influence of cold, nutrient-rich sub-Antarctic surface waters. A more mixed water column initiated at ~2.4 Ma, and a consequent productivity increase led to the gradual reduction of the Discoaster species, until their extinction at 1.91 Ma. This period was characterized by the low values of the Florisphaera profunda index and high abundances of upper photic zone flora, indicative of nutrient-rich surface water conditions. High productivity at the location during this period could have also been amplified by localized upwelling events driven by the Mozambique Channel eddies.

Original languageEnglish
Pages (from-to)187-197
Number of pages11
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume505
Early online date2 Jun 2018
DOIs
Publication statusPublished - 15 Sept 2018

Funding

This research used samples and data provided by the International Ocean Discovery Program (IODP). We are thankful for much support from the crew of the R/V JOIDES Resolution and the IODP staff. This work is part of the project Ocean and Climate 2: Land-ocean interaction and climate variability in low latitudes funded thru the German Science Foundation ( DFG ) Research Center/Cluster of Excellence “The Ocean in the Earth System” MARUM (Grant 49926684 ). This manuscript benefited from the editorial handling of Thierry Correge, and Jeremy Young and an anonymous reviewer who provided critical and constructive comments and suggestions. All the data from this manuscript will be archived in the PANGAEA database ( www.pangaea.de ). Appendix A

FundersFunder number
German Science Foundation
California Department of Fish and Wildlife49926684
Natural Environment Research CouncilNE/P000037/1
Deutsche Forschungsgemeinschaft

    Keywords

    • Calcareous nannofossils
    • Expedition 361
    • Nannoplankton
    • Western Indian Ocean

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