Latest pleistocene to holocene alluvial basin construction: An example from the Nara Basin, central Japan.
Latest pleistocene to holocene alluvial basin construction: An example from the Nara Basin, central Japan.
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最新更新世至全新世冲积盆地构造：以日本中部奈良盆地为例。
DOI：
10.1016/j.quaint.2017.06.016
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发表时间：
2017
影响因子：
2.2
通讯作者：
Hori Kazuhisa and Takada Masashi
中科院分区：
文献类型：
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作者：
Itoh Nobuaki;Hori Kazuhisa and Takada Masashi
与邻近的沿海平原相比，位于海洋沉积极限上游的冲积平原或盆地对海平面和气候变化等外来强迫的响应很少受到关注。本研究调查的冲积盆地的地层和演变的奈良，日本，形成沿着中游的大和河及其支流，因为在末次盛冰期（LGM），基于新收集的放射性碳定年沉积物岩心分析和整理现有的钻孔日志，放射性碳年龄，和埋藏深度的考古遗迹。在末次盛冰期附近的海平面低水位期间，盆地内没有发生大的河流下切作用。此外，与位于河流下游的大坂平原南部相比，最新更新世至全新世地层（厚度<5 m）非常薄。这些观测结果表明，海平面变化引起的基准面波动，以及与周围山脉活动断裂有关的构造沉降，自末次盛冰期以来对盆地的沉积几乎没有影响，盆地一直是沉积物转移或运输的区域。过时的考古遗迹的埋藏深度表明，过去2000年积累的沉积物厚度在盆地的大部分地区，每年的降雨量约为1-2 m。历史时期人为干扰引起的次生林扩张，以及流域出口下游多次滑坡引起的河床抬升，可能促进了流域的洪水淤积。
The response of alluvial plains or basins located upstream from the limit of marine deposition to allogenic forcing, such as sea level and climate change, has received little attention compared with adjacent coastal plains. This study investigates the stratigraphy and evolution of an alluvial basin in Nara, Japan, which has formed along the middle reaches of the Yamato River and its tributaries since around the Last Glacial Maximum (LGM), based on the analysis of newly collected radiocarbon-dated sediment cores and by collating existing borehole logs, radiocarbon ages, and burial depths of dated archaeological remains. Major fluvial incision did not occur in the basin during the sea-level lowstand around the LGM. In addition, the latest Pleistocene to Holocene strata (<5 m thick) are extremely thin compared with the southern part of the Osaka Plain, which is located in the lower reaches of the river. These observations indicate that the base level fluctuations caused by eustatic sea level change, and tectonic subsidence related to active faults in the surrounding mountains, have had little influence on deposition in the basin since around the LGM and that the basin has been a zone of sediment transfer or transport.The burial depths of dated archaeological remains suggest that the thickness of sediment that has accumulated over the last 2000 years is around 1–2 m across large areas of the basin. The expansion of secondary forest caused by human disturbance in the historical period, and repeated landslide-induced river-bed uplift downstream from the outlet of the basin, may have promoted flood deposition in the basin.