Biogenic sediments and their paleoceanographic implication in West Pacific Warm Pool during the Pleistocene

Abstract

Primary productivity has played an important role in the global carbon cycle during the Quaternary. The average Corg/N ratio was 7.0 from the core MD97-2140 in the West Pacific Warm Pool (WPWP) over the last 1 755 ka, which indicates a main contribution of marine organic carbon to the organic matter in the sediments. Large fluctuations in mass accumulation rates (MARs) of biogenics and lithogenics from this core since the marine isotope stage (MIS) 6 reflected the moderate variability in oceanographic condition, while little fluctuations in MAR-biogenics and -lithogenics from the MIS 59 to MIS 7 implied the relatively stable and uniform oceanographic condition, although the sea surface temperatures (SSTs) probably fluctuated by ca. 5 °C. MAR-organic since the MIS 6 increased evidently during the glacial periods, which ascribed to terrestrial inputs, including lithogenic matter and dissolved nutrient, which also contribute to stimulating primary productivity. The results compared among the four cores in the WPWP since the MIS 9 indicate that in the western sector with the shallow thermocline, high primary productivity during the glacial periods was controlled by wind-induced surface water mixing, upwelling, and terrestrial inputs, while in the central and eastern sectors, the little different medium to low productivity might have been made by more intense upwelling driven by strong winds because the thicker warm surface water pool and the deeper thermocline prevented nutrient-bearing water from upwelling to upper water column even during the glacial times.