STUDY OF OKINAWA TROUGH SEDIMENTATION RATES AND PALEOENVIRONMENT BASED ON URANIUM SERIES ISOTOPE

摘要

Spectrometry of ~(238)U, ~(234)U, ~(230)Th and, ~(232)Th in three Okinawa Trough cores showed that, based on the ~(230)Th/~(232)Th activity ratio, the sedimentation rates were about 2.5 cm/ka, 2.8 cm/ka and 8.5 cm/ka respectively during the Holoceneand about 20.1 cm/ka, 12.29 cm/ka, 8.8 cm/ka and 12.6 cm/ka respectively during the Wurm glacial. To examine the past global climatic and oceanographic changes, the stable oxygen isotopes δ~(18)O and CaCO_3were measured. The Th content and Th/U ratio showed that variations of terrigenous material input from the continental shelf were associated with glacial and interglacial changes and sea level fluctuations.