Abstract
The Pleistocene Ryukyu Group composed mainly of shallow-marine carbonates was deposited with hig-amplitude and short-termed glacioeustatic sea-level changes in the Middle Pleistocene age. We carried out core observation, carbon and oxygen isotopic analyses and XRD analyses to recognize subaerially exposure surfaces (SES), and to make clear the precise sea-level changes in the Middle Pleistocene age. For the purpose, six boring cores in the southern part of Miyako Island, southwestern Japan, were examined. As a result, the followings are revealed; (1) the Ryukyu Group of the study area is divided into 6 units, (2) each unit can be subdivided into two to four subunits based on SES, (3) each subunit was deposited during the interstadial period such as 5a, 5c and 5e during the Marine Oxygen Isotope Stage 5.
