Event layers in the Japanese Lake Suigetsu 'SG06' sediment core: description, interpretation and climatic implications
Event layers in the Japanese Lake Suigetsu 'SG06' sediment core: description, interpretation and climatic implications
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DOI：
10.1016/j.quascirev.2013.10.026
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发表时间：
2014
影响因子：
4
通讯作者：
G. Schlolaut;A. Brauer;M. Marshall;T. Nakagawa;R. Staff;C. Ramsey;H. Lamb;C. Bryant;R. Naumann-R.-Nau
中科院分区：
文献类型：
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作者：
G. Schlolaut;A. Brauer;M. Marshall;T. Nakagawa;R. Staff;C. Ramsey;H. Lamb;C. Bryant;R. Naumann-R.-Nau
湖泊沉积物中的事件层是过去极端事件的标志，主要是洪水或地震的结果。对地层的详细描述可以区分所涉及的沉积过程，如地表径流、滑坡或水下边坡破坏。这些过程然后可以解释其触发机制。在这里，我们提出了一个40万年的事件层年表，日本水月湖。事件层的特点是使用多代理方法，采用光学显微镜和μXRF微相分析。水月湖的绝大多数事件层都是由洪水事件（369个中的362个）产生的，这使得该地区首次建立了长期、定量（相对于重现性）和日期明确的洪水年表。洪水层的频率显示了很高的变化，在过去的40万年，它似乎是极端降水事件解耦的平均长期降水。例如，洪水层的频率是最高的冰川在25 ka BP左右，当时日本正在经历一个普遍寒冷和干燥的气候。其他冷事件，如海因里希事件1或晚冰期stadial，显示出较低的洪水层频率。这两个观测结果都排除了与平均降水量和温度的简单直接关系。我们认为，特别是在冰期，台风成因/台风路径的变化是最有可能控制洪水层频率，而不是在季风锋或积雪融化的变化。洪水年表的频谱分析显示，百年和千年的时间尺度上的周期性变化，220年，450年和2000年的周期性最明显。然而，洪水层的频率似乎不仅受到气候变化的影响，而且还受到地震等造成的侵蚀率变化的影响。
Event layers in lake sediments are indicators of past extreme events, mostly the results of floods or earthquakes. Detailed characterisation of the layers allows the discrimination of the sedimentation processes involved, such as surface runoff, landslides or subaqueous slope failures. These processes can then be interpreted in terms of their triggering mechanisms. Here we present a 40 ka event layer chronology from Lake Suigetsu, Japan. The event layers were characterised using a multi-proxy approach, employing light microscopy and μXRF for microfacies analysis. The vast majority of event layers in Lake Suigetsu was produced by flood events (362 out of 369), allowing the construction of the first long-term, quantitative (with respect to recurrence) and well dated flood chronology from the region. The flood layer frequency shows a high variability over the last 40 ka, and it appears that extreme precipitation events were decoupled from the average long-term precipitation. For instance, the flood layer frequency is highest in the Glacial at around 25 ka BP, at which time Japan was experiencing a generally cold and dry climate. Other cold episodes, such as Heinrich Event 1 or the Late Glacial stadial, show a low flood layer frequency. Both observations together exclude a simple, straightforward relationship with average precipitation and temperature. We argue that, especially during Glacial times, changes in typhoon genesis/typhoon tracks are the most likely control on the flood layer frequency, rather than changes in the monsoon front or snow melts. Spectral analysis of the flood chronology revealed periodic variations on centennial and millennial time scales, with 220 yr, 450 yr and a 2000 yr cyclicity most pronounced. However, the flood layer frequency appears to have not only been influenced by climate changes, but also by changes in erosion rates due to, for instance, earthquakes.