Tephrochronology of Late Quaternary Strath Terraces and Their Implications to Neotectonic Movements in the Shitada and Tochio Regions of the Niigata Basin, Central Japan
Tephrochronology of Late Quaternary Strath Terraces and Their Implications to Neotectonic Movements in the Shitada and Tochio Regions of the Niigata Basin, Central Japan
复制标题
日本中部新泻盆地下田和栃尾地区晚第四纪地层阶地的年代学及其对新构造运动的意义
DOI：
10.4116/jaqua.39.521
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
A. Urabe
中科院分区：
文献类型：
--
作者：
T. Choi;N. Takahama;A. Urabe
为了阐明新泻盆地中东部边缘Shitada(Ikarashi River)和Tochio(Kariyada River)地区晚第四纪地层阶地的年代学及其对新构造运动的意义，对其进行了研究。根据地貌形态和标志层与阶地之间的盖层关系对阶地进行了划分。在覆盖阶地沉积的壤土和黑土中发现了6个Tephra层(ST1-ST6)。ST4与广泛分布的Tephra AS-K相关(13ka)，ST5与AT相关(25ka)，ST6与DKP相关(50ka)。Shitada地区的阶地依次为Sh-D、Sh-C、Sh-B、Sh-A3、Sh-A2和Sh-A1阶地，Tochio地区为TO-D、TO-C、TO-B、TO-A4、TO-A3、TO-A2和TO-A1阶地。相同年龄的阶地在NNE-SSW和NW-SE向活动断裂上与现今河床的相对高度不同。这些不连续不能简单地用活动褶皱造成的倾斜来解释。我们认为，NNE-SSW和NW-SE向断裂系统是块体分割的结果，这是50ka以来Shitada和Tochio地区隆升运动的特征。
Late Quaternary strath terraces younger than 50ka were investigated in the Shitada (Ikarashi River) and Tochio (Kariyada River) regions, central eastern margin of the Niigata Basin, in order to clarify their chronology and implications to neotectonic movements. The terraces were classified based on geomorphologic configuration and tephro-stratigraphic relation between marker tephra horizons and the terraces. Six tephra horizons (ST 1-ST 6) were found in the loam and black soil, which overlie terrace deposits. ST 4 is correlated with the widespread tephra As-K (13ka), ST 5 with AT (25ka) and ST 6 with Dkp (50ka). The terraces are in chronologic order Sh-D, Sh-C, Sh-B, Sh-A3, Sh-A2 and Sh-A1 terraces for the Shitada region and To-D, To-C, To-B, To-A4, To-A3, To-A2 and To-A1 terraces for the Tochio region.The presence of strath terraces since the post-glacial transgression indicates that intermittent local and/or regional uplift initiated terrace development. Same aged terraces had different relative heights from the present riverbed across NNE-SSW and NW-SE trending active faults. These discontinuities cannot be simply explained by tilting due to active folding. We propose that the NNE-SSW and NW-SE trending fault systems have been active as the result of block segmentation, which characterize the uplift movement of the Shitada and Tochio regions since 50ka.