Planktonic foraminifera record and SST reconstruction for the last 130 ka in the Western South Atlantic

This work reconstructs Late Quaternary paleoceanographic changes in the western South Atlantic Ocean based on sedimentary core GL-77, recovered from the lower continental slope in the Campos basin, offshore SE Brazil. The studied interval comprises the last 130 ka. Changes in sea surface temperature (SST) and paleoproductivity were estimated using the total planktonic foraminiferal fauna and oxygen isotope analyses. The age model was based on the oxygen isotope record, biostratigraphic datums and AMS 14C dating. It was observed that the Pleistocene/Holocene transition occurs within Globorotalia menardii Biozone Y, and is not coeval with the base of Biozone Z. The range between summer and winter SST estimates is larger during the glacial period compared to interglacials. Three peaks of low SST around 70, 50 - 45 and 20 ka coincided with periods of enhanced SE trade winds. Despite faunal differences between the last interglacial (MIS 5e) and the Holocene, our SST estimates suggest that SSTs did not differ significantly between these intervals.本研究依托从巴西东南部近海坎波斯盆地（Campos basin）大陆下斜坡采集的沉积岩芯GL-77，重建了南大西洋西部晚第四纪的古海洋演化历程。本次研究的地层跨度为过去130 ka。研究通过对全部浮游有孔虫类群与氧同位素的分析，估算了海面温度（sea surface temperature, SST）与古生产力的变化特征。年代框架的建立基于氧同位素记录、生物地层基准面以及AMS 14C测年（accelerator mass spectrometry carbon-14 dating）。研究结果显示，更新世/全新世转换事件发生于门纳德球室虫（Globorotalia menardii）生物带Y内，且与生物带Z的底界并非同时期。相较于间冰期，冰期时段的夏季与冬季海面温度估算值的差值更大。在约70 ka、50~45 ka以及20 ka三个时段出现的海面温度低值峰值，与东南信风增强的时期高度吻合。尽管末次间冰期（MIS 5e，海洋同位素阶段5e）与全新世的浮游有孔虫类群组合存在显著差异，但本次研究的海面温度估算结果表明，这两个时段的海面温度并无显著差别。