2021 Volume 77 Issue 2 Pages I_349-I_354
Sediment samples and beach edges were collected and measured at several locations in Sesoko Island and Ada Beach in Okinawa known as coral reef beaches. The sediments were classified into coral fragments, foraminifera, shell fragments, minerals and sea urchin spines, while foraminifera were classified into Baculogypsina spaerulata, Calcarina gaudichaudii and others. In addition to the grain size and circularity, high-dimensional information obtained by Fourier analysis was newly used as sediment characteristics. The direction of movement of the sediment was investigated based on these physical characteristics.
Results of the foraminifera shape evaluation indicates that the high harmonic number component decreases with the progress of star sand abrasion, the spectral intensity also decreases, and the grain size becomes smaller. The NE direction of the sediment transport was predominant in using the whole sediment, while the SW direction was principal in using the star sand, which was consistent with previous aerial photographs and existing reports, respectively. By quantitatively evaluating foraminiferal shape changes, it is possible to discuss the direction of the sediment transport in coral reef beaches.
