Sedimentology and stable isotope ratios of planktonic foraminifera from two cores off Northeastern Brazil

The stable isotope composition of planktonic foraminifera correlates with evidence for pulses of terrigenous sediment in a sediment core from the upper continental slope off northeastern Brazil. Stable oxygen isotope records of the planktonic foraminiferal species Globigerinoides sacculifer and Globigerinoides ruber (pink) reveal sub-Milankovitch changes in sea-surface hydrography during the last 85,000 yr. Warming of the surface water coincided with terrigenous sedimentation pulses that are inferred from high XRF intensities of Ti and Fe, and which suggest humid conditions in northeast Brazil. These tropical signals correlate with climatic oscillations recorded in Greenland ice cores (Dansgaard-Oeschger cycles) and in sediment cores from the North Atlantic (Heinrich events). Trade winds may have caused changes in the North Brazil Current that altered heat and salt flux into the North Atlantic, thus affecting the growth and decay of the large glacial ice sheets.

浮游有孔虫的稳定同位素组成与巴西东北部大陆斜坡沉积岩心中陆源沉积脉冲的证据相关。浮游有孔虫物种 Globigerinoides sacculifer 和 Globigerinoides ruber（粉红色）的稳定氧同位素记录揭示了在过去 85,000 年间海面水文状况的亚米尔科维奇变化。表层水的变暖与来自钛和铁高XRF强度的陆源沉积脉冲相吻合，这表明巴西东北部的湿润条件。这些热带信号与格陵兰冰芯（丹斯加德-奥谢格周期）和北大西洋沉积岩芯（海因里希事件）中记录的气候振荡相关。贸易风可能导致了巴西暖流的变化，从而改变了热量和盐分通量进入北大西洋，进而影响了大型冰川冰盖的生长与衰亡。