Abstract
We reinvestigated the Pleistocene calcareous nannofossil biostratigraphy of Site U1431D (International Ocean Discovery Program (IODP) Expedition 349) in the South China Sea (SCS). Twelve calcareous nannofossil Pleistocene datums are identified in the site. The analysis confirms that the last occurrence (LO) of Calcidiscus macintyrei is below the first occurrence (FO) of large Gephyrocapsa spp. (>5.5 μm). The FO of medium Gephyrocapsa spp. (4–5.5 μm) is also identified in the samples through morphometric measurements, which was unreported in shipboard results. Magnetobiochronologic calibrations of the numerical ages of LO of Pseudoemiliania lacunosa and FO of Emiliania huxleyi are underestimated and need reassessment. Other potential markers such as a morphological turnover of circular to elliptical variants of Pseudoemiliania lacunosa and a small Gephyrocapsa acme almost synchronous with the FO of Emiliania huxleyi may offer biostratigraphic significance in the SCS. The morphologic changes in Gephyrocapsa coccoliths are also examined for the first time in Site U1431D. Placolith length and bridge angle changes are comparable with other ocean basins, suggesting that morphologic changes are most likely evolutionary novelties rather than being caused by local climate anomalies.
Highlights
The Pleistocene is characterized by worldwide sea level lows and highs due to increased amplitudes of glacial and interglacial episodes, respectively [1,2,3]
Twelve (12) calcareous nannofossil datums were detected for the Pleistocene section of Site
Samples barren of nannofossils were dominated by detrital materials such as clay in the first
Summary
The Pleistocene is characterized by worldwide sea level lows and highs due to increased amplitudes of glacial and interglacial episodes, respectively [1,2,3]. Ice volume fluctuations are well represented in deep sea sedimentary sequences by variations in proxies such as sediment properties, fossil assemblages, and/or isotope concentrations. Several periods in the Pleistocene are thought to be analogs to the modern-day climate, such as Marine Isotope Stage (MIS) 11 [4,5] and may contribute to a further understanding of past and future climate change dynamics. These climatic events can be put into geologic context through relative dating by using calcareous nannofossils
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