Contrasting styles and rates of tectonic uplift of coral reef terraces in the Ryukyu and Daito Islands, southwestern Japan

Abstract

Coral reef terraces on Kikai, Hateruma and Yonaguni in the Ryukyu Islands on the Eurasian lithospheric Plate and those of Kita-Daito and Minami-Daito Islands on the Philippine Sea Plate indicate three distinct patterns of coral reef terrace formation and preservation, primarily reflecting different uplift rates. The Kikai-type, which includes many terraces from Oxygen Isotope Stages 5e to 1, is a result of high uplift rate of ca. 1.8 m/kyr on the fore-arc rise of a Chilean-type subduction zone. Arcward (westward) tilting and faulting are also characteristic of the Kikai-type. The Hateruma-type is characterized by two coral reef terraces younger than the Stage 5e terrace and they are arranged in a concentric annular pattern. Slow uplift rate of ca. 0.3 m/kyr, adjacent to a Mariana-type subduction margin is typical of the Hateruma-type. The emergence of Kikai and Hateruma Islands is recent, younger than Isotope Stage 5e and 7, respectively, reflecting the active deformations of the leading edge at the overriding Eurasian Plate. In the Daito-type, atolls surrounded by fringing reefs have been uplifted very slowly (less than 0.05 m/kyr), but over a time period of at least several million years. Slow uplift and long history of Daito-type islands is the result of up-bulging of the Philippine Sea Plate as it migrates toward the Ryukyu Trench.