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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Late Pleistocene-Holocene river dynamics at the Trent-Soar confluence, England, UK
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Late Pleistocene-Holocene river dynamics at the Trent-Soar confluence, England, UK

机译：英国英格兰特伦特-苏拉合流处晚更新世-全新世河流动力学

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Although river confluences have received geomorphic attention in recent years it is difficult to upscale these studies, so confluence-dominated reaches are commonly presumed to be either: (1) braided; or (2) meandering and characterized by laterally migrating channels. If the geomorphology of a confluence zone is to be considered over longer timescales, changes in river style need to be taken into account. This paper uses a combination of remote sensing techniques (LiDAR, GPR, ER), borehole survey and chronometric dating to test this differentiation in the confluence-zone of a medium-sized, mixed-load, temperate river system (Trent, UK), which on the basis of planform evidence appears to conform to the meandering model. However, the analysis of 'confluence sediment body stratigraphy' demonstrates that the confluence does not correspond with a simple meander migration model and chronostratigraphic data suggests it has undergone two major transformations. Firstly, from a high-energy braid-plain confluence in the Lateglacial (25-13Kyrs cal BP), to a lower-energy braided confluence in the early to middle Holocene (early Holocene-2.4 kyr BP), which created a compound terrace. Second, incision into this terrace, creating a single-channel confluence (2.4-0.5 kyr cal BP) with a high sinuosity south bank tributary (the River Soar). The confluence sediment-body stratigraphy is characterized by a basal suite of Late Pleistocene gravels bisected by younger channel fills, which grade into the intervening levee and overbank sediments. The best explanation for the confluence sediment body stratigraphy encountered is that frequent switching (soft-avulsions sensu Edmonds et al., 2011) of the tributary are responsible for the downstream movement of the channel confluence (at an average rate of approximately 0.5m per year) dissecting and reworking older braid-plain sediments. The late Holocene evolution of the confluence can be seen as a variant of the incisional-frequent channel reorganization (avulsion) model with sequential downstream migration of the reattachment point.
机译：尽管近年来河流汇合已受到地貌学的关注，但很难进行这些研究的规模化，因此通常认为汇合为主的河段是：（1）辫状;或（2）蜿蜒曲折，以横向迁移通道为特征。如果要在更长的时间范围内考虑汇合区的地貌，则需要考虑河流样式的变化。本文结合了遥感技术（LiDAR，GPR，ER），钻孔测量和测年测年法来测试中型，混合负荷，温带河流系统（英国特伦特）汇合区的这种差异，在平面证据的基础上，这似乎符合曲折模型。然而，对“汇合沉积物地层学”的分析表明，汇合不符合简单的曲折迁移模型，年代地层数据表明它已经经历了两个主要转变。首先，从晚冰期（25-13Kyrs cal BP）的高能辫状平原汇合处，到全新世早期到中期的低能辫状汇合处（早期全新世-2.4 kyr BP），形成了一个复合阶地。其次，切入该阶地，形成单通道汇合（2.4-0.5千瓦卡尔BP），具有高弯曲度的南岸支流（River Soar）。汇流沉积物-地层的特征是晚更新世砾石的基层被较年轻的河道填充物平分，这些河道分为中间的堤坝和岸上沉积物。对于所遇到的汇流沉积物地层的最好解释是，支流的频繁转换（软断层sensu Edmonds等人，2011）是导致河道汇流下游运动的原因（每年平均约为0.5m） ）解剖和修复较旧的辫状平原沉积物。汇合的全新世晚期演化可以看作是切开-频繁通道重组（撕脱）模型的一种变体，具有重新连接点的顺序向下游迁移。

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