Primary Production Changes for the Past 60, 000 Years

Deduced by the Analyses on a Piston Core from the Ryukyu Trench Slope, Northwest Pacific Ocean

Abstract

A piston core (RN95-PC4) collected from the central Ryukyu Trench slope is investigated concerning the down-core fluctuations in planktic and benthic δ¹⁸O and δ¹³C values, total organic carbon contents (TOC), organic carbon/nitrogen (C/N) ratios, calcium carbonate contents, benthic foraminiferal crops, and planktic foraminiferal fauna. Based upon the oxygen isotope stratigraphy and three AMS¹⁴C dates, this core reveals a continued sedimentation for the past -60ka; from the early oxygen isotope Stage 3 to the present. The primary production in surface water increased during the last glacial period, particularly in Stage 2, judging from the significant signals in down-core changes of benthic δ¹³C values, TOC, C/N ratios, and so on. Analysis of planktic foraminiferal fauna suggests that the increased primary production in Stage 2 might be ascribed to relative development of upwelling with cold water invasion.