A study on sediment characteristics and transportation processes of carbonate sand grains in Gimnyeong coastal dunes, Jeju Islands, Republic of Korea

초록

Gimnyeong coastal dunes in Gujwa-eup, Jeju Islands, are a very important aeolian sedimentary landforms based on its rarity and specificity among coastal dunes distributed in Korea. Most of the previous researches on Gimnyeong coastal dunes have been focused on the development of large scale topography and the time periods of dune formations. In this study, authors have tried to delineate the sediment migration processes and the fractionation of carbonate particles in Gimnyeong coastal dunes. For this purpose, the sediment samples were collected from the present dune surface along a sideline between Gimnyeong Beach and the location of 2 km inland. These samples have been used to be performed sieve analysis, particle identification and point counting, scanning electron microscope (SEM) and X-ray diffraction analysis (XRD). As a result of the particle size analysis, it was found that fine to medium sand grains of 1.0 to 2.7 F accounted for about 81 to 92% (the mean size of 2.08 F). While the mean size did not show a significant change in the dune area, the sorting became better toward the inland, and the skewness gradually showed negative skewness, indicating the relative dominance of fine grains in the landward. Most importantly, the separation of particles along the movement direction of the dunes was clearly observed, and this is attributed to the inherent morphological structure between red algae and mollusks which induced the difference in transport efficiency. Therefore, the results of this study suggest that the characteristics of hydrodynamic behaviors according to the shape of carbonate bioclastic particles can be also applied to the current aeolian deposits of Jeju Islands.

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