| Summary: | application/pdf Surface sediment samplings were made using a piston corer at six sites in the central grabens of the Okinawa Trough during the DELP88 leg. 2 cruises on the Kaiko-Maru No. 5. Three sites (P-1, P-2 and P-3B) were located in the southern Okinawa Trough, and the other three sites (P-5, P-6 and P-7) in the Natsushima 84 Deep which is a basin with a hydrothermal activity in the middle Okinawa Trough. These sediment samples consist mainly of gray (7.5Y4/1) silty clay without characteristic sedimentary structure except for the P-1 sample, which is composed of some turbidite layers showing a graded bedding. The sedimentation rate estimated from the analysis of radioactive isotopes is 100cm/1000yr (P-2 and P-5), 130cm/1000yr (P-6) and 200cm/1000yr (P-7). Age determination given by the planktonic foraminifera indicates that all the sediment samples are Recent in age. 第5海工丸を用い沖縄トラフで実施されたDELP 1988年度第2次航海では柱状採流器を用いて6地点から柱状表層堆積物試料を採取した｡ 3地点は南部沖縄トラフ, 3点は中部沖縄トラフの熱水活動が盛んな""なつしま84海盆""に位置する.試料は主に均質な灰色(7.5Y4/1)シルト質粘土から成り,顕著な堆積構造は級化層理を示す乱泥流堆積層からなるP-1試料を除いて見られない. departmental bulletin paper
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