大田市仁摩町琴ヶ浜の海浜砂に含まれる有孔虫群集

Kotogahama beach in Oda City, Shimane Prefecture is one of the famous singing-sand beaches of Japan. We conducted foraminiferal faunal analyses on sand samples collected at Kotogahama and surrounding beaches. Foraminiferal assemblages in this study area are mainly composed of species that inhabit rock reefs. Such rock reef species might be transported from adjacent rock reef regions and accumulate into beach sands. The foraminiferal assemblages at the singing-sand beaches, namely, Kotogahama and Otsube, were dominated by the exclusive occurrence of Amphistegina spp. The spacial distribution patterns of foraminifera and sand grain size suggest that the main direction of sand grain transportation along the coastline might be southwest to northeast at Kotogahama beach, and foraminiferal shells except Amphistegina spp. might be removed from beach sands into an offshore area with finer-grained materials. Consequently, the shells of Amphistegina spp. might be concentrated in beach sands because of an outstanding sorting process at the singing-sand beaches owing to their large and robust shell.