Formation and infilling of oxbow lakes in the Ishikari lowland, northern Japan
Formation and infilling of oxbow lakes in the Ishikari lowland, northern Japan
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DOI：
10.1016/j.quaint.2015.06.016
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发表时间：
2016-03
影响因子：
2.2
通讯作者：
Y. Ishii;K. Hori
中科院分区：
文献类型：
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作者：
Y. Ishii;K. Hori
牛轭湖是曲流河漫滩的常见地貌。尽管牛轭湖在洪泛区演变中可能具有重要意义，但人们对牛轭湖的沉积相和沉积速率、形成年龄及其在景观中的持久性知之甚少。我们分析了加密记录的解释钻孔岩心从四个牛轭湖在石狩低地，北方日本。钻孔沉积物被解释为基底粗粒河床沉积物（单元1），随后是完全断开前的河道充填物（单元2）和完全断开后的漫滩沉积物（单元3）。第2单元在一个核中很厚，但在其他核中非常薄或不存在。这种差异可能是由于截断时初期牛轭的转向角而不是截断机制（曲流截断或局部撕脱）造成的。基于14 C年龄、火山灰分析和137 Cs的详细年代学表明，牛轭湖形成于上个世纪，沉积速率在单元2中约为45-90 mm/y，在单元3中约为3.9-22.0 mm/y。石狩低地的牛轭湖可能会持续600-1300年的景观，因为开始切断。牛轭湖的生产率和它们的持续性之间的关系表明，牛轭湖的生产率在1899-1959年期间是高的。景观中牛轭湖的数量在几十年或世纪的时间尺度上可能是可变的，这取决于牛轭湖的生产率。
Oxbow lakes are common landforms in meandering river floodplains. Despite the possible importance of oxbow lakes in floodplain evolution, little is known about sedimentary facies and sedimentation rates of oxbow fills, their formation ages and their persistence in the landscape. We analyzed infilling records by interpretation of borehole cores from four oxbow lakes in the Ishikari lowland, northern Japan. The borehole sediments were interpreted as basal coarse-grained streambed sediments (Unit 1) succeeded by channel fills before complete disconnection (Unit 2) and overbank deposits after complete disconnection (Unit 3). Unit 2 is thick in one core but very thin or absent in the other cores. This difference may result from the diversion angles of the incipient oxbow at the time of cutoff rather than the cutoff mechanism (meander cutoff or local avulsion). Detailed chronology based on the14C ages, tephra analysis, and137Cs suggests that the oxbow lakes formed during the last centuries and the sedimentation rates are approximately 45–90 mm/y in Unit 2 and 3.9–22.0 mm/y in Unit 3. Oxbow lakes in the Ishikari lowland may persist in the landscape during 600–1300 years since the initiation of cutoff. The relationship between the production rate of oxbow lakes and their persistence suggests that the production rate of oxbow lakes was high during 1899–1959. The number of oxbow lakes in the landscape may be variable in time scales of several decades or a century depending on the production rate of oxbow lakes.