Earth science investigation in the area around the southern Ryukyu Islands - Report on RN03 cruise by TIS Nagasaki Maru -

As a part of the educational cruise (RN03 Cruise) for students of Faculty of Science, University of the Ryukyus, by TIS Nagasaki Maru, the scientific survey was carried out during May 26 to June 5, 2003. Geomagnetic and bathymetric surveys were carried out in the east off Ishigaki Island to investigate faults and basement structure. Two distinct faults, striking NW-SE and dipping SW, were found between Ishigaki Island and Tarama Island. In order to estimate the primary productivity of algal symbiont·bearing larger foraminifera in low-latitude shelf environments, surface sediments were quantitatively sampled from an island shelf off the west of Miyako Island. The planktic foraminiferal genus PuUeniatina is an important paleoceanographic proxy in the Ryukyu Arc region, indicating either the past Kuroshio Current or variations in winter sea surface temperature for the late Quaternary. Plankton tows and cm protlles in the upper 200 m depth were taken at three stations along 125°E to correlate the ecological distribution of PuUeniatina with hydrographic environmental properties. We dredged seafloor samples at the northern shelf off Ishigaki-jima and Iriomote-jima to confirm the location of "Iriomote Submarine Volcano" which erupted in 1924. No volcanic rocks were recovered from the shelf