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Sedimentation of Tidal Currents

潮流的沉积

基本信息

批准号：
01540624
负责人：
MAKINO Yasuhiko
金额：
$ 0.64万
依托单位：
Ibaraki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

In the last year of my project, I did research on sedimentation of intertidal sandbars in the Ariake Sea, and Pleistocene intertidal sediments near Ajigaura beach along the Pacific coast.1. In the Ariake Sea (Bay), muddy tidal flat sediments are widely distributed at the inner part, and sandy tidal flat sediments are developing along the coast of the outer part in Kumamoto Prefecture. At Toguchiura beach, the Uto Peninsula, we can see ten and more ridges of intertidal sandbars. Their ridges are sinuous in phase and subparallel to the beach. Many wave ripples are constructed on the intertidal sandbars by waves in a wind during high tide. The crest line of wave ripples is oblique to the ridge of these sandbars.The peaked crests of wave ripples on a seaward slope of these bars are eroded with weak wave action just before emergence of wave ripples, and become rounded or flattened. Wave ripples on a landward slope are very little deformed by waves. As the result, the attitude of wave ripples is characteristics at the position of intertidal sandbars. Their difference is very important as a criterion for discriminating the seaward direction.2. We found out Pleistocene step sediments at Ajigaura beach. When a longshore bar moves to the beach under fair weather, it becomes a beach-attached (welded) bar. The backrushing water sliding down the surface of the beach deforms welded bar sediments to make step. We can know the step-base depth (h) from the step depth (Z : the thickness of step sediments) at that time ; h=1.8 Z. As description on step sediments is very few, I am going to describe on step sediments.

在我项目的最后一年，我研究了有明海潮间带沙洲的沉积，以及太平洋沿岸Ajigaura海滩附近的更新世潮间带沉积物。在有明海（湾）内，泥质潮滩沉积物广泛分布，熊本县外沿海岸发育砂质潮滩沉积物。在宇户半岛的土口村海滩，我们可以看到十多个潮间带沙洲的山脊。它们的山脊在相位上是弯曲的，几乎与海滩平行。潮间带沙洲在涨潮时，波浪在风中形成了许多波浪波纹。波浪波纹的波峰线斜向这些沙洲的山脊。这些沙洲向海斜坡上的波浪波峰在波浪波纹出现之前受到弱波浪作用的侵蚀，变得圆润或扁平。向陆坡上的波浪波纹受波浪的影响很小。结果表明，潮间带沙洲位置波浪波纹的姿态具有一定的特征。它们的差异是判别向海方向的重要标准。我们在Ajigaura海滩发现了更新世台阶沉积物。当一个海岸沙洲在晴朗的天气下移动到海滩上时，它就变成了一个附着在海滩上的（焊接）沙洲。逆冲水沿着海滩表面滑下，使焊接杆状沉积物变形形成台阶。由当时的台阶深度（Z：台阶沉积物厚度）可知台阶基底深度(h)；h=1.8 Z.由于阶跃沉积物的描述很少，我将描述阶跃沉积物。