Age model and oxygen isotope stratigraphy of site ODP1202 in the southern Okinawa Trough, northwestern Pacific

Abstract

The two sedimentary sequences drilled at Holes 1202B and 1202D were correlated based upon direct lithologic observation, shipboard logging of magnetic susceptibility, and bulk density to form a stacked record of 410 m in length. Calcareous nannofossil and planktic foraminiferal occurrences confine the bottom of the record to be younger than 85 ka, whereas the sediments in the interval ∼225 - 280 mbsf in Hole 1202D are apparently of turbidite origin. Eleven AMS carbon-14 datings of planktic foraminifera and scaphopod samples from Hole 1202B suggest that the upper 110 m has a continuous record dating back over the past 28 thousand years. An oxygen isotope stratigraphy based upon planktic fora minifera Neogloboquadrina dutertrei was established from the stacked sequence. The upper part of the δ 18 O profile can be well correlated to that from the central Okinawa Trough site DGKS9603 (Li et al. 2001) in both trend and absolute values whereas the lower part is considered to belong to marine oxygen isotope stage 4. The sedimentation rates have been always high at this site, ranging from 1.5 to 16 meters per thousand years.