大潟海岸の堆積過程 -とくに底質の構成集団による検討-

Abstract

Although analysis of size-frequency distributions of the sediments by the technique of partitioning size distributions has provided much information regarding the sedimentary process characteristics of depositional environments, few detailed studies have been done on the suaqueous beach. The aim of this study was characterize the sediments in a barred coast by conducting a detailed anslysis of the size-frequency curves using the graphical dissection technique to develop field-based models for coastal sedimentary processes.Depositional patterns of the constituent populations of bottom sediments are summarized as follows. The mean size of the dominant population of each sediment decreased seaward in a stepwise manner at the beach face, the landward slope of the bar, and the offshore zone. The proportion of the dominant population increased seaward as alternate increases and decreases in the nearshore zone, and exibited nearly unchanged large values in the offshore zone. The depositional patterns suggest that the seaward changes of the bottom sediment occur as repeating decreases of coarser population which are inversely proportional to increases of adjacent finer population.These characteristics are related to the generation mechanism of bar system.