THE QUATERNARY CORAL-REEF TRACTS OF HATERUMA, RYUKYU-ISLANDS, JAPAN

The island of Hateruma is located at the southwestern end of the Ryuky u Island chain and covers an area of about 15 km(2) with its highest p oint at 59.5 m.a.s.l. The morphology of Hateruma is characterized by a n eight-step staircase (I to VIII after Ota et al., 1982) most of whic h eroded into the previously formed coral reefs (II and IV to Vm). Thi s study presents 100 age estimations on 43 coral samples using electro n spin resonance (ESR), alpha- and mass spectrometric U-series methods . The dating results imply that the Ryukyu Limestone was predominantly formed during oxygen isotope stages 7 and 5e. Two age estimates of ar ound 300 ka suggest an earlier reef-building period. The main problem for establishing the Quaternary history of Hateruma lies in the fact t hat the coral ages and the staircase morphology do not correlate. Addi tionally, it is difficult to distinguish autochthonous from allochthon ous samples, the latter having possibly been relocated by tsunamis. Co rals relating to substages 5a and 5c (around 75 and 105 ka, respective ly) are found in the immediate vicinity of much older samples. The res ults of this study prove the disappointing fact that Hateruma cannot y et be used as a tool for reconstructing palaeo sea levels.