干旱区生态环境知识资源中心

Previous studies have demonstrated long-term changes in effective moisture in sub-Saharan Africa. Here, we reconstruct Holocene environments using a similar to 7 m lake-sediment sequence recovered from the northeastern Nigerian Sahel and attempt to distinguish basin-specific changes from regional climatic variations. The sequence was analysed for sedimentological properties, mineral magnetism and pollen, and dated by Cs-137, Pb-210 excess and C-14. Extremely arid conditions of the terminal Pleistocene ended ca. 11 500 cal. BP (calendar years) when climate ameliorated and a lake developed until the occurrence of an arid event leading to lake desiccation at similar to 11 200 cal. BP. Following this, climate ameliorated and a water body re-emerged. Very wet conditions predominated 11 200-5600 cal. BP, followed by drought between 5600 and 5500 cal. BP and a return to moderate humidity from 5500 to 4000 cal. BP. After 4000 cal. BP, a marked deterioration occurred, culminating in lake desiccation at ca. 800 cal. BP. After this time the climate remained generally dry and the re-emerging lake was shallow. Comparison of these results with other well-dated sequences in the region demonstrates the importance of basin-specific influences on the palaeolimnological records in addition to regional climatic controls. Disentangling these different controls, as well as the reconstruction of Holocene climate, therefore requires a multiple-basin approach. Copyright (C) 2008 John Wiley & Sons, Ltd.