The Holocene History of Lake Victoria
The Holocene History of Lake Victoria
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DOI：
10.1579/0044-7447-29.1.2
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发表时间：
2000-02
期刊：
影响因子：
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通讯作者：
T. Johnson;K. Kelts;E. Odada
中科院分区：
文献类型：
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作者：
T. Johnson;K. Kelts;E. Odada
摘要东非湖泊国际十年（IDEAL）最近的调查大大提高了我们对维多利亚湖历史的认识。地震反射剖面证实了该湖的起源是区域倾斜的结果，并提供了湖盆40万年的估计年龄。地震记录中记录了三次主要的干燥化事件，它们可能反映了10万年米兰科维奇周期的气候强迫。最近的干旱期导致先前存在的湖泊完全干涸。维多利亚湖起源于14600年前（14.6 ka）的干燥景观。在最初的500年里，随着湖泊水位的上升，初级生产力非常高，这是由洪水景观的大量营养物质所滋养的。几种慈鲷和其他鱼类从它们的河流避难所游出来，在新的湖泊中定居，在随后的14000年里产生了数百种新的特有物种。湖平面上升，直到14.2 ka至13.6 ka的一个短暂的溢出事件。在新仙女木事件期间，封闭盆地条件恢复到11.2 ka，此时主要的外流和开放盆地条件永久建立。湖泊经历了逐步加强分层和水柱稳定性，通过上半年的全新世，硅藻生产力下降到最低点，从9.8到约7.5万年。这一时期与世界各地许多全新世记录中观察到的8.2 ka气候事件相吻合，但要长得多。在过去的6000年里，水柱混合的程度似乎稳步增加。从开放的湖泊中提取的短岩心记录了从20世纪30年代开始的湖泊条件的变化，这种变化发展到20世纪80年代初的主要生态系统崩溃。1930年代沉积物性质的变化与人口和农业活动的迅速扩张同时发生，这表明了因果关系。可以想象，在大约9800年至7500年前，由于自然原因，该湖经历了类似的条件。
Abstract Recent investigations by the International Decade for the East African Lakes (IDEAL) have significantly advanced our knowledge on the history of Lake Victoria. Seismic reflection profiles confirm the origin of the lake as a result of regional tilting and provide an estimated age of 400 000 years for the lake basin. Three major desiccation events are recorded in the seismic records that may reflect the 100 000 year Milankovitch cycle of climate forcing. The most recent arid period resulted in complete desiccation of the pre-existing lake. Lake Victoria arose from a dry landscape 14 600 calendar years ago (14.6 ka). Primary production was extremely high as lake level rose in its first 500 years, nourished by the high input of nutrients from the flooded landscape. A few species of cichlids and other fish swam out of their fluvial refugia to colonize the new lake, generating hundreds of new endemic species over the ensuing 14 000 years. Lake level rose until a brief overflow event at about 14.2 ka to 13.6 ka. Closed-basin conditions returned during the Younger Dryas until 11.2 ka, when major outflow and open-basin conditions were permanently established. The lake experienced progressively stronger stratification and water-column stability through the first half of the Holocene, and diatom productivity dropped to a minimum from 9.8 to about 7.5 ka. This period coincides with, but is much longer than, the 8.2 ka climatic event that has been observed in many Holocene records from throughout the world. The degree of water-column mixing appears to have steadily increased over the last 6000 years. Short cores from the open lake, document a shift in lake conditions beginning in the 1930s that progressed to the major ecosystem collapse of the early 1980s. The coincidence of the shift in sediment properties in the 1930s with the beginning of rapid expansion of human population and agricultural activity suggests cause and effect. It is conceivable that the lake experienced similar conditions due to natural causes between about 9800 and 7500 years ago.