Uplift Rates Estimated from Relative Heights of Fluvial Terrace Surfaces and Valley Bottoms
Uplift Rates Estimated from Relative Heights of Fluvial Terrace Surfaces and Valley Bottoms
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根据河流台地表面和谷底的相对高度估算的抬升率
DOI：
10.5026/jgeography.104.6_809
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发表时间：
1995
影响因子：
3.1
通讯作者：
M. Yanagida
中科院分区：
文献类型：
--
作者：
A. Yoshiyama;M. Yanagida
本文讨论了利用河流阶地面和存款基底定量估算内陆地区隆升速率的新方法。以往的研究表明，河流剖面随气候和海平面的周期性变化而发生规律性变化，因此，在间冰期（海洋同位素第5e阶段和现在），形成了类似的剖面，具有较大的盐度，而在冰期（第6阶段和第2阶段），则出现了相反的线性剖面。在河流上游，5e期谷底被随后冰期积累的存款所充填。根据这些观测结果，认为第5e阶段燃烧谷底与目前河床之间的相对高度值（BV值）表明这些阶段（120-130 ky）的抬升。根据阶地发育和火山灰年代学的研究成果，对日本主要河流沿着的BV值和TT值进行了评述。在大多数河流中游，同一站点的TT和BV值是一致的。尽管上游或支流的TT值没有降低，但BV值在上游显著降低。这意味着目前的河流剖面没有完全处于平衡状态，上游和支流正在退化。作为长期隆升速率的指标，TT值与BV值相比具有适用于上游和现场数据可用性的优势。然而，在河流阶地不发育的上游或支流，这些方法是不可能应用的。迄今为止，山区的抬升速率是根据山脉的轮廓高度或水库中截留的侵蚀物质的量来推测的，但还没有用直接的数据来检验。用TT值和BV值计算的大部分站点的抬升速率为0.10.8mm/年，但这些站点并不位于极高的山区。根据中部山区北方黑部河流域的TT值，估计了大于1 mm/年的大抬升速率。
In this paper the new methodology for quantitative estimation of uplift rates at inland region was discussed using fluvial terrace surfaces and deposit bases. Previous studies have revealed that river profiles regularly changed according to the cyclic fluctuation of climate and sealevel ; therefore, in the interglacial ages (the marine isotope stage 5e and the present) similar profiles with large concavity formed, and in the glacial ages (stage 6 and 2) linear profiles appeared on the contrary. In upper reaches of rivers, stage 5e valley bottoms were filled with the deposit accumulated in the subsequent glacial stages. Based on these observations, the value of relative height between the stage 5e burned valley bottom and the present river floor (BV value) is considered to indicate uplift during those stages (120-130 ky). Similarly, the value of relative height between the stage 6 terrace and the stage 2 terrace (TT value) can be used as an indicator of uplift during the period between those two stages.The BV values and TT values distributed along Japanese major rivers were reviewed on the basis of previous studies on terrace development and tephro-chronology. In middle reaches of most of rivers, the TT and BV values at the same sites are concordant to each other. The BV values remarkably decrease upstream in spite of no reduction of the TT values in the upper reaches or branches. This implies that present river profiles have not completely been in equilibrium and are now degrading in the upper streams and branches. As an indicator of long-term uplift rate, the TT values have the advantage of applicability to upper reaches and availability of field data in comparison to the BV value. However, it is impossible to apply these methods in the upper reaches or branches where fluvial terraces are not well developed.Up until now, the uplift rates in mountainous region were presumed from the outlined altitude of mountains or the amount of eroded material trapped in reservoirs, but have not been examined by direct data. The uplift rates obtained by using TT values and BV values are 0.10.8 mm/year in large number of sites, which are not located in very high mountainous area. Large uplift rates more than 1 mm/year were estimated from TT values at the Kurobe river basin, in the northern part of Chubu mountainous region.