混濁流堆積物粒度分布の時空変化(河川・湖沼・沿岸環境(2),一般講演)

概要

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It has been known that turbidity currents are the major transport process of sediments from shallow marine to deep-sea floor. However, hydraulic conditions of the currents have been rarely measured because the currents occur in subaqueous environments so that it is quite difficult to observe directly. Here, we attempted to establish a method to estimate hydraulic conditions of turbidity currents by inverse analysis of ancient turbidites based on downstream variation of their characteristics that reflects behavior of turbidity currents. We assumed that sediments in turbidity currents are composed of sand and silt mixtures, and one-dimensional model was employed as a forward model. The result of inverse analysis suggested that the turbidity current that formed the turbidite in the Otadai Formation, Chiba Prefecture, was 0.176m/s in flow velocity, 500m in flow thickness, and 501166s in flow duration time.
2010-09-09