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Abstract: Clay mineral assemblage of the core MD06-3047 in the western Philippine Sea has been used to trace sediment provenance and transport process and thus to constrain the East Asian monsoon evolution as well as its forcing mechanism over the past 700kyr. Clay minerals mainly consist of smectite (61%) and illite (23%), with minor chlorite (10%) and kaolinite (6%). Provenance analyses suggest that the smectite originates predominantly from the alteration of nearby Luzon volcanic rocks. Illite is primarily derived from the Asian continent with eolian origin. Illite contents show strong glacial/interglacial cyclicity as constrained by oxygen isotope stratigraphy. Variations of illite contents are ultimately controlled by the East Asian monsoon evolution, characterized by higher illite values during glacials with relatively stronger East Asian winter monsoon but weaker East Asian summer monsoon. During interglacials, enhanced East Asian summer monsoon and rainfall could produce more smectite with poor crystallinity from Luzon to the study core. Spectral analyses of illite content and smectite crystallinity display a strong periodicity at 100kyr for the East Asian winter monsoon and 100kyr, 30kyr, and 23kyr periodicities for the East Asian summer monsoon, respectively, suggesting the unique forcing processes of the East Asian winter monsoon from high-latitudes (i.e., ice volume) and the East Asian summer monsoon from both high-latitudes and low-latitudes (i.e., tropical Pacific). [Copyright &y& Elsevier]

We analyzed rare earth elements (REEs) and Sr Nd isotope compositions of siliciclastic components in a sediment core from the middle Okinawa Trough (OT), to elucidate spatiotemporal variations in the sediment provenance, and their underlying mechanisms for the last 20 ky. Our results show that the trough deposits were characterized by different proportions of Changjiang- and Taiwan-derived (especially, the western rivers) sediments over time, from which we infer dramatic changes in sea-level, intensity of the Kuroshio Current (KC) inflow, and the East Asian monsoon since the last glacial maximum (LGM). In contrast to previous studies, the sea-level lowstand proximity of the paleo-Changjiang to the middle OT, and the contemporaneous enhancement of the East Asian winter monsoon (EAWM) may have played pivotal roles in supplying terrigenous inputs and forming middle OT deposits during the last glacial period, whereas the paleo-Huanghe was of lesser importance. After the early Holocene (especially the late Holocene cold period between ~4.8 and ~2.7 cal ky BP), a remarkable shift in the combined records of REEs and Nd isotopes reveals a causal link between variations in the Taiwan source and the KC inflow, coupled with climate changes in the East China Sea (ECS). This study suggests that Sr Nd isotope compositions and REEs are useful proxies for understanding the links between river development and paleoenvironmental/paleoclimatic changes in East Asian marginal regions. • Sr Nd isotopic records provide new insights into the sediment source in Okinawa Trough (OT). • Changjiang has played a leading role in forming the middle OT deposits during the last glacial period. • Taiwan-sourced sediments in the OT deposits are linked to Kuroshio/Taiwan Warm Current dynamics. • Our study provides that the comprehensive accumulation history of OT deposits over the last 20 ky. [ABSTRACT FROM AUTHOR]

Clay mineralogical analysis and scanning electron microscope (SEM) analysis were performed on deep-sea sediments cored on the Benham Rise (core MD06-3050) in order to reconstruct long-term evolution of East Asian Summer Monsoon (EASM) rainfall in the period since 2.36 Ma. Clay mineralogical variations are due to changes in the ratios of smectite, which derive from weathering of volcanic rocks in Luzon Island during intervals of intensive monsoon rainfall, and illite- and chlorite-rich dusts, which are transported from East Asia by winds associated with the East Asian Winter Monsoon (EAWM). Since Luzon is the main source of smectite to the Benham Rise, long-term consistent variations in the smectite/(illite + chlorite) ratio in core MD06-3050 as well as ODP site 1146 in the Northern South China Sea suggest that minor contributions of eolian dust played a role in the variability of this mineralogical ratio and indicate strengthening EASM precipitation in SE Asia during time intervals from 2360 to 1900 kyr, 1200 to 600 kyr, and after 200 kyr. The EASM rainfall record displays a 30 kyr periodicity suggesting the influence of El Niño–Southern Oscillation (ENSO). These intervals of rainfall intensification on Luzon Island are coeval with a reduction in precipitation over central China and an increase in zonal SST gradient in the equatorial Pacific Ocean, implying a reinforcement of La Niña-like conditions. In contrast, periods of reduced rainfall on Luzon Island are associated with higher precipitation in central China and a weakening zonal SST gradient in the equatorial Pacific Ocean, thereby suggesting the development of dominant El Niño-like conditions. Our study, therefore, highlights for the first time a long-term temporal and spatial co-evolution of monsoonal precipitation in East Asia and of the tropical Pacific ENSO system over the past 2.36 Ma. [ABSTRACT FROM AUTHOR]