Fossil diatom assemblage changes due to paleoenvironment change, tsunami, and typhoon in southern Japan
Fossil diatom assemblage changes due to paleoenvironment change, tsunami, and typhoon in southern Japan
复制标题
DOI：
10.1111/iar.12476
复制
发表时间：
2023-01
期刊：
影响因子：
1.5
通讯作者：
A. Cho;K. Kashima;H. Baranes;C. Ladlow;K. Katsuki;J. Woodruff
中科院分区：
文献类型：
--
作者：
A. Cho;K. Kashima;H. Baranes;C. Ladlow;K. Katsuki;J. Woodruff
追踪古环境变化和过去的事件沉积对于在空间上评估自然灾害是非常重要的。本文论述了硅藻组合的变化对环境变化的影响，揭示了事件沉积的成因。为了研究古环境变化并确定海啸和台风沉积之间的差异，我们分析了日本南部两个沿海湖泊(川原湖和龙湖)的沉积物中的硅藻，这些湖泊的洪水沉积与历史上的台风和海啸事件有关。沉积岩心从公元前500年延伸到约公元1000年，而硅藻组合的岩心下部变化表明，在约公元500年至1700年之间，川原湖和龙湖都经历了一系列从咸水到更新鲜条件的转变。我们观察到以前被确认为海啸或台风成因的事件沉积物中的硅藻组合明显偏离。对于1707年海伊海啸保存在琉球湖的最显著的事件沉积物来说，海洋硅藻的沉积是海洋洪水的证据，而随后土壤和淡水硅藻的沉积表明陆源沉积物在回归海洋流动过程中被动员。相比之下，川原湖最显著的事件沉积物与公元1281年的神风台风造成的淡水洪水有关，含有非常低的硅藻丰度和淡水类群的峰值，其次是硅藻数量的峰值，这可能是由于事件期间营养物质的涌入和重新充氧导致的更大的生物活动。
Tracking paleoenvironmental change and past event deposits is very important to evaluate the natural hazard spatially. This paper presents how the environment changes and implies the event deposit depending on the diatom assemblage change. To investigate paleoenvironmental change and identify the difference between tsunami and typhoon deposits, we analyze diatoms from the sediments in two coastal lakes in southern Japan where flood deposits have been linked to historical typhoon and tsunami events (Lakes Kawahara and Ryuo). The sediment cores extend from B.C.E. 500 to approximately C.E. 1000 and the downcore variation in diatom assemblages indicates a series of transitions from saline to fresher conditions in both Lake Kawahara and Lake Ryuo between approximately C.E. 500 and 1700. We observe an obvious deviation in diatom assemblages in event deposits previously identified to be either of tsunami or typhoon in origin. For the most prominent event deposit preserved in Lake Ryuo by the Hoei tsunami of C.E. 1707, the deposition of marine diatoms serves as evidence of marine flooding, while the subsequent deposition of soil and freshwater diatoms indicates the mobilization of terrigenous sediment during returning seaward flows. In contrast, the most prominent event deposit in Lake Kawahara is associated with freshwater flooding by the Kamikaze typhoon of C.E. 1281 and contains very low diatom abundances and a peak of freshwater taxa, followed by a peak in diatom counts potentially due to greater biological activity induced by a resultant influx of nutrients and re‐oxygenation during the event.