The seismic-stratigraphic record of lake-level fluctuations in Lake Challa: Hydrological stability and change in equatorial East Africa over the last 140 kyr
The seismic-stratigraphic record of lake-level fluctuations in Lake Challa: Hydrological stability and change in equatorial East Africa over the last 140 kyr
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查拉湖湖面波动的地震地层记录：过去140 kyr赤道东非的水文稳定性和变化
DOI：
10.1016/j.epsl.2009.12.023
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发表时间：
2010
影响因子：
5.3
通讯作者：
M. Batist
中科院分区：
文献类型：
--
作者：
J. Moernaut;D. Verschuren;F. Charlet;I. Kristen;M. Fagot;M. Batist
地震反射数据从火山口湖查拉（山。基利曼哈罗，赤道东非）揭示了一个1210米厚的沉积填充物，其中包含晚第四纪湖平面波动的明显地震地层特征。外推的一个很好的约束年龄模型的核心上的一部分的序列表明，这些湖平面的波动代表了一个详细的和连续的记录，在过去的140 kyr在赤道东非的水分平衡变化。这一记录表明，最严重的干旱发生在128 kyr BP之前的倒数第二次冰期（与海因里希事件11同期）和1114 kyr BP至197 kyr BP之间的末次间冰期“megadbrought”时期;相比之下，末次冰期最大（LGM）干旱是适度的。在此之前，有75000年相对稳定和潮湿的气候条件，被11次短暂的干旱中断，其中5次与海因里希事件2至6的时间相匹配。东非赤道附近的气候历史反映了由轨道偏心率调制的季风降雨的岁差强迫的变化，但岁差驱动的水分波动不如在北方和热带非洲南部观察到的那样极端。在查拉湖记录中，从1997年到20.5万年，几乎连续的潮湿气候与在赤道西非记录的170 kyr BP之后更大的干旱趋势形成对比。这一长时间的潮湿的冰川气候和短期，相对温和的LGM干旱可以归因于更大的独立性西印度洋季风动力学北方高纬度冰川比那些在热带大西洋。这种相当持久的潮湿冰川气候制度可能有助于维持坦桑尼亚东弧山脉热带森林生态系统的高度生物多样性。
Seismic-reflection data from crater lake Challa (Mt. Kilimanjaro, equatorial East Africa) reveal a ∼210-m thick sedimentary infill containing distinct seismic-stratigraphic signatures of late-Quaternary lake-level fluctuations. Extrapolation of a well-constrained age model on the cored upper part of the sequence suggests that these lake-level fluctuations represent a detailed and continuous record of moisture-balance variation in equatorial East Africa over the last 140kyr. This record indicates that the most severe aridity occurred during peak Penultimate glaciation immediately before ∼128kyr BP (coeval with Heinrich event 11) and during a Last Interglacial ‘megadrought’ period between ∼114 and ∼97kyr BP; in comparison, Last Glacial Maximum (LGM) aridity was modest. It was preceded by ∼75000years of relatively stable and moist climate conditions interrupted by eleven short-lived dry spells, five of which match the timing of Heinrich events 2 to 6. Climate history near the East African equator reflects variation in the precessional forcing of monsoon rainfall modulated by orbital eccentricity, but precession-driven moisture fluctuations were less extreme than those observed in northern and southern tropical Africa. The near-continuous moist climate from ∼97 to 20.5kyr BP recorded in the Lake Challa record contrasts with the trend towards greater aridity after ∼70kyr BP documented in equatorial West Africa. This long period of moist glacial climate and a short, relatively modest LGM drought can be attributed to greater independence of western Indian Ocean monsoon dynamics from northern high-latitude glaciation than those in the tropical Atlantic Ocean. This rather persistent moist glacial climate regime may have helped maintain high biodiversity in the tropical forest ecosystems of the Eastern Arc mountains in Tanzania.