Report on RN98 cruise by T/S Nagasaki Maru in the area around the southern Ryukyu Islands

概要

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Investigation of subbottom seismicity, grab sampling of surface sediments, and net sampling of planktonic organisms were carried out in the southern Okinawa Trough and off Miyako Island in November 1998. Four pop-up type ocean bottom seismographs (OBS) were settled on the seafloor of the southern Okinawa Trough to investigate subbottom seismicity of this area. All OBS' s were successfully retrieved after 4 days observation and numerous number of micro-earthquakes were recorded by them. Surface sediments collected from the island shelf and the adjacent slopes off the west coast of Miyako Island are composed mainly of bioclastic carbonate sand. Foraminifers occur dominantly in some samples and alive benthic organisms such as larger foraminifers, sponges, corals and molluscs were obtained from some samples. Neogene mudstone gravels were taken from the station on the fore-arc slope south of the island. Ten phyllosoma larvae of Palinurid lobster and Scyllarid lobster are collected by the large larval net (mouth diameter: 2.0 m) from the surface layer north of Iriomote Island. Each phyllosoma larva was kept in the 1 liter bottle, and they were transported to the laboratory to study the larval development.
琉球大学理学部の論文