Late Pleistocene and Holocene drought events at Lake Tana, the source of the Blue Nile
Late Pleistocene and Holocene drought events at Lake Tana, the source of the Blue Nile
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DOI：
10.1016/j.gloplacha.2011.06.004
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发表时间：
2011-08-01
影响因子：
3.9
通讯作者：
Bryant, Charlotte
中科院分区：
文献类型：
--
作者：
Marshall, Michael H.;Lamb, Henry F.;Bryant, Charlotte
过去17000年的磁性和地球化学岩心数据与埃塞俄比亚塔纳湖的新地震地层相关联。推断过去湖泊水位的变化，从而推断有效降水。数据证实，低水位与北大西洋的海因里希事件1 （H1）相吻合，正如先前从硅藻和花粉证据中显示的那样（Lamb et al., 2007）。在15.3千立方英尺的时候，湖水加深，突然恢复到淡水状态，湖水溢出进入青尼罗河。在13.0 ~ 12.5 cal kyr BP之间推断出低径流和湖泊水位以及降雨，这可能代表了新仙女木时期ITCZ和相关季风锋的南向抑制。发生在8.4和7.5 cal kyr BP的两次干旱事件也被解释为季风锋的南移。这些事件中的第一个似乎比8.2千万年BP更早，也更重要。虽然我们没有看到非洲湿润期的突然结束，但降水量在6.8千万年BP之后下降。这一时期在大约4.2亿年前的干旱时期达到顶峰，支持了尼罗河流量减少是古埃及王国灭亡的一个因素的观点。(C) 2011 Elsevier B.V.版权所有
Magnetic and geochemical core data spanning the last 17,000 years are correlated with new seismic stratigraphy from Lake Tana, Ethiopia. to infer past lake-level change and hence effective precipitation. The data confirm that low lake-level coincides with Heinrich Event 1 (H1) in the North Atlantic, as previously shown from diatom and pollen evidence (Lamb et al., 2007). The lake deepened at 15.3 cal kyr BP and abruptly returned to freshwater conditions, when the lake overflowed into the Blue Nile. Low runoff and lake levels and therefore rainfall are inferred between 13.0 and 12.5 cal kyr BP and may represent southerly suppression of the ITCZ and the associated monsoon front at the time of the Younger Dryas. Two drought episodes occurred at 8.4 and 7.5 cal kyr BP, and are also interpreted as a southward shift in the monsoon front. The first of these events appears to have preceded and been more significant than the 8.2 cal kyr BP. Precipitation declined after 6.8 cal kyr BP, although we do not see an abrupt end to the African Humid Period. This period culminated in a dry episode at similar to 4.2 cal kyr BP, supporting the view that reduced Nile flow was a contributing factor to the demise of the Egyptian Old Kingdom. (C) 2011 Elsevier B.V. All rights reserved.