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The carbonate content of bulk samples was analyzed for the sediment cores of MD06-3050 taken from Benham Rise,western Philippine Sea.The fluctuations in carbonate content for the past 150 ka show a general pattern of the "Atlantic type" of carbonate cycle,i.e.lower in glacials and higher in interglacials.Both sediment coarse fractions and foraminifera fragment ratios were used as indicators of the dissolution intensity of carbonate,and show a similar pattern to carbonate content change since 150 ka.TOC content in bulk samples was also measured,which showed a good consistency with carbonate content.In contrast,the primary productivities derived from the relative abundance of coccolith species F.profunda,yield significantly different trend.By comparison of above proxies,it is inferred that there may be multiple factors controlling the variation in carbonate content,but dissolution is certainly the most important.This dissolution pattern maybe related to the Corg/CaCO3 rain ratio and the ventilation of deep water.

Core MD06-3052 was taken from the continental slope off the Luzon Island in the western Philippine Sea.Multiple proxies such as AMS14C dating,sediment grain size and foraminiferal oxygen isotope were used to reveal the 5 turbidite events since 150 kaBP.The turbidites have coarser grain size than the normal layers,mostly composing of sand and silt.The occurrence time of the 5 turbidite events was calculated by AMS14C dating and oxygen isotope as 13.3,20.4,34.3,41.7 and 121.8 kaBP,separately,of which the latter 4 ones occurred in the low sealevel stages of the last glacial,especially in MIS 2-3,and the earliest one at the relatively low sealevel stage in MIS 5e,indicating that rapid sealevel oscillation during low sealevel stages was probably the main cause of the turbidite events.However,the steep slope may be a favorable topography for the sediment instabilities in Core MD06-3052.

Major elements were studied for reconstruction of sediment provenance and paleoenvironment over the last 24 kaBP with the samples collected from Core PC-1 in the northern Okinawa Trough.In addition to major elements,grain size of 402 samples and planktonic foraminifer δ18O of 344 samples have been analyzed that leads to an average resolution at centennial scale.The study offers a new high resolution material for reconstructing the history and main control factors of the sediment input in the northern Okinawa Trough over the last 24 ka.In according to the variation in major element compositions,the core could be divided into three distinct depositional units,separated by two volcanic layers at 7.3 and 12.7 cal kaBP respectively.Both provenance discriminating plot and R-mode factor analysis indicate that vertical changes in major elements are mainly contributed by the nearby terrestrial materials,whereas the contribution from hydrothermal activity,marine biologic deposition,and volcanism are minor.In particular,the contribution of nearby terrestrial materials show an obvious change trend and can be well correlated with the sea level fluctuation and the evolution of the Tsushima Warm Current.It seems that paleoclimate renders no significant impact on the change in terrigenous sediment provenance.

Synthetic analyses on typical element ratio and source discrimination function were carried out for a sediment core with high sedimentary rate collected along the Tsushima Warm Current(TWC) main stream on the southwestern slope of Japan Sea,in order to trace the sediment provenance change of the study area in the Holocene.Data suggest that the Nakdong River of Korea and Changjiang of China are the main source of the studied sediments.Affected by the TWC strength evolution and sea level rise,their contributions changed with time.There are five stages.In the early Holocene(9.6-6.5 kaBP),especially during the two Melt Water Pulse(MWP) stages including MWP-1C(9.4-8.7 kaBP) and MWP-1D(7.8-7.4 kaBP),the contribution of these rivers was high.Their contribution became lower during 6.5-3.0 kaBP and 2.0-0.7 kaBP,corresponding to the temporally weakening of TWC in the northern East China Sea and southwestern Japan Sea.In 3.0-2.0 kaBP and 0.7-0 kaBP,TWC was strengthened and more fluvial materials from the Nakdong River and Changjiang River were deposited in the study area.

Synthetic analyses on sedimentology and geochemistry of a sediment core with high deposition rate collected under the Tsushima Warm Current (TWC) axis on the southwestern slope of East/Japan Sea were carried out,in order to discuss the formation and evolution of TWC during the Holocene. Based on them,we got very similar results to those from paleoceanographical method in nearby areas. Thus,sedimentological and geochemical methods were offered for the future study on TWC evolution in the study area. Totally,there were five main evolution periods of TWC recorded in the study core. In the early Holocene,that is 9.6 kaBP,TWC began to weakly enter into the East/Japan Sea,together with the East China Sea Coast Water (ECSCW) enriched in nutrient matter,which led to the transfer of bottom environment from anoxic to oxic. At 6.5 kaBP,the modern current mode dominated by TWC in the southern East/Japan Sea finally formed,whereas the influence of ECSCW almost disappeared. After that,TWC obviously weakened. At 3.0 kaBP,TWC strengthened again to almost reach its present level,since then the circulation structure has been relatively stable,except for a weak depression of TWC during 2.0~0.7 kaBP.