Stable hydrogen isotopic composition (dD) and stable carbon isotopic composition (δ¹³C) of sediment core GeoB9508-5 off Senegal

To reconstruct variability of the West African monsoon and associated vegetation changes on precessional and millennial time scales, we analyzed a marine sediment core from the continental slope off Senegal spanning the past 44,000 years (44 ka). We used the stable hydrogen isotopic composition (dD) of individual terrestrial plant wax n-alkanes as a proxy for past rainfall variability. The abundance and stable carbon isotopic composition (d13C) of the same compounds were analyzed to assess changes in vegetation composition (C3/C4 plants) and density. The dD record reveals two wet periods that coincide with local maximum summer insolation from 38 to 28 ka and 15 to 4 ka and that are separated by a less wet period during minimum summer insolation. Our data indicate that rainfall intensity during the rainy season throughout both wet humid periods was similar, whereas the length of the rainy season was presumably shorter during the last glacial than during the Holocene. […]

为重建西非季风及其相关植被在岁差和千年时间尺度上的变异性，我们对塞内加尔大陆坡下过去44,000年（44千年前）的海洋沉积岩心进行了分析。我们采用单个陆地植物蜡n-烷的稳定氢同位素组成（δD）作为过去降雨变率的替代指标。通过对同一化合物的丰度和稳定碳同位素组成（δ13C）的分析，评估了植被组成（C3/C4植物）和密度变化。δD记录揭示了两个湿润期，它们分别与38至28千年前和15至4千年前当地的夏季最大日照量相对应，并被夏季日照量最少的较干燥期所分隔。我们的数据显示，在这两个湿润湿润期，雨季的降雨强度相似，而根据推测，在最后一个冰期期间，雨季的长度可能比全新世期间更短。