Intensity of African Humid Periods Estimated from Saharan Dust Fluxes.
Intensity of African Humid Periods Estimated from Saharan Dust Fluxes.
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从撒哈拉尘埃通量估算的非洲潮湿时期的强度。
DOI：
10.1371/journal.pone.0170989
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发表时间：
2017
期刊：
影响因子：
3.7
通讯作者：
Krüger S
中科院分区：
文献类型：
--
作者：
Ehrmann W;Schmiedl G;Beuscher S;Krüger S
北非经历了巨大的变化，水文和植被在第四纪后期驱动的太阳辐射引起的热带雨带的变化，并进一步调制千年尺度的干旱和植被气候反馈。虽然大多数过去的代理和建模研究集中在时间和空间动态的最后一个非洲潮湿的时期，很少有人知道的强度和特点的前全新世潮湿的时期。在这里，我们提出了一个高分辨率的记录，细粒东撒哈拉的灰尘从东地中海跨越过去的180 kyr，这是基于海洋沉积物的粘土矿物组成，特别是高岭石/高岭土的比例。最低风成高岭石运输发生在非洲潮湿的时期，因为高岭石通缩阻碍了湿度和植被覆盖的增加。相反，在这些时期，含高岭石的新生代岩石中的高岭石风化储存在湖盆、河床和土壤中。在随后的干燥阶段，细粒粉尘从干燥的湖泊，河流和土壤中动员起来，导致最大的风成吸收和运输高岭石。当这些沉积物源耗尽时，高岭石的输运再次减少。我们的结论是，吹出撒哈拉沙漠到东地中海的粘土大小的灰尘量是成比例的强度的高岭石风化和积累在土壤和湖泊沉积物，从而强度的前湿润期。这些潮湿的时期为现代人类迁移出非洲提供了窗口，正如以前所假设的那样。最强的湿润期发生在Eemian，其次是两个较弱的阶段，集中在约。100卡和CA。80 ka.
North Africa experienced dramatic changes in hydrology and vegetation during the late Quaternary driven by insolation-induced shifts of the tropical rain belt and further modulated by millennial-scale droughts and vegetation-climate feedbacks. While most past proxy and modelling studies concentrated on the temporal and spatial dynamics of the last African humid period, little is known about the intensities and characteristics of pre-Holocene humid periods. Here we present a high-resolution record of fine-grained eastern Saharan dust from the Eastern Mediterranean Sea spanning the last 180 kyr, which is based on the clay mineral composition of the marine sediments, especially the kaolinite/chlorite ratio. Minimum aeolian kaolinite transport occurred during the African Humid Periods because kaolinite deflation was hampered by increased humidity and vegetation cover. Instead, kaolinite weathering from kaolinite-bearing Cenozoic rocks was stored in lake basins, river beds and soils during these periods. During the subsequent dry phases, fine-grained dust was mobilised from the desiccated lakes, rivers and soils resulting in maximum aeolian uptake and transport of kaolinite. The kaolinite transport decreased again when these sediment sources exhausted. We conclude that the amount of clay-sized dust blown out of the Sahara into the Eastern Mediterranean Sea is proportional to the intensity of the kaolinite weathering and accumulation in soils and lake sediments, and thus to the strength of the preceding humid period. These humid periods provided the windows for the migration of modern humans out of Africa, as postulated previously. The strongest humid period occurred during the Eemian and was followed by two weaker phases centred at ca. 100 ka and ca. 80 ka.