Experimental study of estimation for paleohydraulic conditions based on grain-size of deposits

根据沉积物的粒度组成，人们提出了许多估算古水力条件的方法。在这个研究项目中，我试图通过实验方法来澄清这一现象。不存在由运输引起的普遍的粒度分布，相反，粒度分布强烈地受实验中使用的沙子的粒度分布的影响。个别运输模式的粒度分布和纹理的“原砂”之间的关系是最好的证明与“原砂”的粒度分布的归一化数据。对实验数据进行归一化处理的结果表明，颗粒能否悬浮，对颗粒大小有着相当严格的选择。但是悬浮过程并不优选可以悬浮的颗粒中的特定尺寸;即，悬浮物中存在的每种尺寸的颗粒以与“原砂”中相同的比例表示。此外，水槽中沉积的浊积岩显示出与标准化获得的悬浮砂相同的尺寸模式。然而，崩落和跃移砂的特征粒度分布即使经过短距离搬运也会发生改变，因此，我们不能直接从沉积物的粒度组成信息来估计古水力条件。

Many methods for the estimation of paleohydraulic condition have been proposed based on grain-size composition of deposits. In this research project I tried to clarify the phenomena using by experimental approaches.There is no universal size-distributions induced by transport, and instead, that the size distributions are strongly governed by the size distribution of the sand used in the experiments. Relationships between the grain-size distributions of individual transport modes and the texture of the "original sand" are best demonstrated by normalizing data with the size distribution of the "original sand". The results of normalizing of experimental data suggest that there is rather strict selection as to grain size whether a grain can be suspended. But the suspension process does not prefer a peculiar size among the grains which can be suspended ; i.e., grains of every size present in the suspended load are represented in the same proportion as in the "original sand". Moreover, turbidites deposited in flume show a same size pattern to suspended sands obtained from the normalizing. Avalanching and saltating sands, however, have their characteristic grain-size distributions modified even by short-distance transport.In conclusion we can not estimate the paleohydraulic condition directly from the information of grain-size compositions of deposits!