NW African hydrology and vegetation during the Last Glacial cycle reflected in plant-wax-specific hydrogen and carbon isotopes
NW African hydrology and vegetation during the Last Glacial cycle reflected in plant-wax-specific hydrogen and carbon isotopes
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DOI：
10.1016/j.quascirev.2013.10.013
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发表时间：
2013-12-15
影响因子：
4
通讯作者：
Wefer, G.
中科院分区：
文献类型：
--
作者：
Kuechler, R. R.;Schefuss, E.;Wefer, G.
我们介绍了撒哈拉-萨赫勒过渡的水文重建，涵盖了整个最后一次冰川周期(130ka)，基于植物蜡特有的氢(增量D)和碳同位素(PC)的组合。来自非洲西北部的ODP659点的长链正构烷烃的增量D和增量C-13特征显示出显著的反相关性。作为对已发表的花粉数据的补充，我们推断这一植物蜡信号反映了植被覆盖对萨赫勒地区降水变化的敏感反应，以及东北信风(NetW)对撒哈拉北部生物群(C-3域)的不同贡献。在干旱时期，特别是萨赫勒北部地区可能经历了严重的水分胁迫，导致植被明显萎缩，从而减少了该地区C-4植物蜡质的数量。干旱期间净水强度的增加进一步促进了来自北非C-3植物区的更明显的C-3-植物蜡信号。在湿润时期，以C-4为主的萨赫勒环境向北扩展到撒哈拉地区，同时C-3植物蜡净输入较低。由植物-蜡质三角洲D导出的干旱湿循环与不同主量元素分布所反映的风化强度的变化相一致。环境变化通常与北半球夏季日照的大幅波动有关。在海洋同位素阶段2和阶段3，当太阳辐射变率很低时，水文状况与基于烯酮的东北大西洋海面温度估计之间的耦合变得明显。(C)2013爱思唯尔有限公司。保留所有权利。
We present a hydrologic reconstruction of the Sahara-Sahel transition, covering the complete Last Glacial cycle (130 ka), based on a combination of plant-wax-specific hydrogen (delta D) and carbon isotopes (PC). The delta D and delta C-13 signatures of long-chain n-alkanes from ODP Site 659 off NW Africa reveal a significant anti-correlation. Complementary to published pollen data, we infer that this plant-wax signal reflects sensitive responses of the vegetation cover to precipitation changes in the Sahel region, as well as varying contributions from biomes north of the Sahara (C-3 domain) by North-East Trade Winds (NETW). During arid phases, especially the northern parts of the Sahel likely experienced crucial water stress, which resulted in a pronounced contraction of the vegetation cover, thus reducing the amount of C-4 plant waxes from the region. The increase in NETW strength during dry periods further promoted a more pronounced C-3-plant-wax signal derived from the North African C-3 plant domain. During humid periods, the C-4-dominated Sahelian environments spread northward into the Saharan realm, in association with lower NETW inputs of C-3 plant waxes. Arid humid cycles deduced from plant-wax delta D are in accordance with concomitant changes in weathering intensity reflected in varying major element distributions. Environmental shifts are generally linked to periods with large fluctuations in Northern Hemisphere summer insolation. During Marine Isotope Stages 2 and 3, when insolation variability was low, coupling of the hydrologic regime to alkenone-based estimates of NE Atlantic sea-surface temperatures becomes apparent. (C) 2013 Elsevier Ltd. All rights reserved.