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This study discusses the seasonal variations in surficial sediment grain size and their implications for sediment transport driven by the hydrodynamics in the East China Sea, based on grain size analysis of surficial sediments and salinity data collected from the East China Sea continental shelf during two cruises in 2011. The results show that the grain size distribution on the East China Sea continental shelf presents apparent spatial and seasonal variations. The mud area exhibits more variation than the sand area, which indicates that the sediment supply is the main factor controlling the surficial sediment grain size distribution on the East China Sea continental shelf. The grain size near the Yangtze River Estuary is relatively coarse in summer, because of the inherited characteristics from the previous winter, whereas it is much finer in autumn, due to the input of fine-grained materials during the flood period of the Yangtze River. A high fine-grained sediment concentration was found along the Zhejiang-Fujian coast in autumn when the Zhejiang-Fujian Coastal Current forms. The sediments in the northeast of the study region (the mud patch southwest of Cheju Island) are much coarser, and the fine-grained area is narrower in autumn than in summer because of seasonal variations in the Yellow Sea Coastal Current and the frequency of storms. Simultaneously, the tongue-shaped fine-grained cross shelf front located along the Zhejiang-Fujian coast occurs farther to the south in autumn than in summer. However, the surficial grain size distribution patterns on the middle and outer shelf are similar in the two seasons.

Changing sediment provenance and related paleoenvironmental evolution since marine isotope stages (MIS) 3 have been investigated based on accelerator mass spectrometry (AMS) 14C and optically stimulated luminescence (OSL) dating of core CSDP-01, recovered from the western South Yellow Sea (SYS). Based on our results, sea level fluctuations and monsoonal climate variations are identified as the principal factors driving these changes. Sea level fluctuations determined the accommodation space in the shelf area, while the monsoonal climate controlled the sediment supply capacity from river to sea. Mineral and Sr Nd isotopic records reveal the major contribution of the paleo-Changjiang River (Yangtze River) to the study core area during the early-mid MIS 3, which likely defined the northern limit of the paleo-Changjiang delta at that time. High sediment supply and limited accommodation space led to the development of sediment-fed systems on the SYS shelf, resulting in a high preservation potential for thick-stacking and overlapping deltaic sediments. Along with deltaic progradation, core sediment provenance gradually transformed from the paleo-Changjiang River to the paleo-Huanghe River (Yellow River) near the late MIS 3, implying that the paleo-Huanghe River likely emptied into the SYS and built a large delta during the MIS 3 interval. A strong summer monsoon during the early MIS 1 interval was favorable for the Changjiang to deliver abundant sediments to the study core area. A weak summer monsoon during the mid-late MIS 1 when the coastline had retreated to nearly its present-day position decreased the Changjiang and Huanghe supply to the study area. Low sediment supply and sufficient accommodation space gave rise to the development of sediment-starved systems during this period. ɛNd values fluctuated between the Changjiang and Huanghe sources at that time, suggesting that sea bed erosion materials are the main sediment contribution to the study area. In general, sedimentary evolution in the western SYS since MIS 3 is a good example of river-sea interaction in the marginal seas of Southeast Asia, in which sea level and monsoonal climate changes should play an important role.

Reconstructing the Plio-Pleistocene sedimentary history of the Yellow Sea, is important for understanding the long-term influence of the Yellow River (Huanghe) and/or Yangtze River (Changjiang) on the Asian marginal seas and to further constrain any links between river development, regional paleoenvironmental change, tectonic deformation and/or global climate change. Here we present the first high-resolution clay mineral record combined with Sr-Nd isotopic compositions from a 300-m long sediment core recovered in the western South Yellow Sea. Our study suggests that large-scale transgression in the Yellow Sea occurred after ∼0.8 Ma, possibly related to tectonic subsidence of eastern China coast and the Min-Zhe Uplift. In contrast, the sedimentary environment of Bohai and Yellow Seas was mainly dominated by fluvial/lacustrine deposits at 3.5–0.8 Ma. Provenance analysis suggests a major change in sediment provenance from the Yangtze River to the Yellow River at ∼0.8 Ma, which corresponds to the timing of the final integration of the Yellow River in its present form. At the same time the major channels of the Yangtze River migrated from the South Yellow Sea to the modern Yangtze River delta due to the subsidence of east China coast. The consistence in timing of the provenance transition and large-scale regional marine transgression suggests that tectonic deformation, rather than climate change, is the first-order control on the evolution of the Yellow and Yangtze Rivers and sedimentary environmental change in the Bohai and Yellow Seas.

Aeolian dust input exerts significant influence on oceanic biogeochemical cycles and further potentially controls atmospheric CO2 concentrations. However, the possible link between long-term aeolian dust supply and primary productivity in the western North Pacific remains poorly understood. Here, we present a comprehensive study of major and trace elements and total organic carbon (TOC) concentrations of sediments from Integrated Ocean Drilling Program (IODP) Site U1430 in the southern Japan Sea, in order to reconstruct oceanic palaeoproductivity evolution and test its possible link to Asian dust input since 4 Ma. Palaeoproductivity proxies indicate remarkable increases in productivity at ∼3–2 Ma followed by high-frequency oscillations in productivity since 1.2 Ma. We suggest that higher dust-derived iron supply from Central Asia at 3–2 Ma, which was likely driven by the growth of the Northern Hemisphere ice sheets, could account for enhanced primary productivity and export production in the Japan Sea. Such increased oceanic palaeoproductivity could enhance organic carbon burial, which might contribute to the decrease in atmospheric CO2 concentrations, and provide a positive feedback to the global cooling. However, the Tsushima Warm Current (TSWC) intrusion via the southern Tsushima Strait, which was controlled by glacioeustatic sea level changes, has been the principal cause of the rapid changes in primary productivity and benthic redox condition since 1.2 Ma, regardless of continuously increased Asian dust input.

The southwestern South Yellow Sea (SYS) is influenced by tremendous sediment loads derived from the Yellow River (Huanghe) and the Yangtze River (Changjiang). However, the influence of Yangtze River sediments and their transport mechanism in this area remain unresolved. In this study, we present the grain size, clay minerals, and elemental compositions of surface sediments from the southwestern SYS, together with an analysis of field observation seawater salinity and suspended sediment data, to investigate the provenance and transport mechanism of the sediments. Discrimination diagrams of clay minerals, Cr/Th vs. Sc/Al, and rare earth elements (REEs) indicate that the southwestern SYS sediments are mainly derived from the old Yellow River subaqueous delta and the Yangtze River. Interestingly, Yangtze sediments enter the SYS in ways that differ seasonally. In summer, Yangtze sediments may be transported into the central SYS by the dispersion of Changjiang Diluted Water (CDW) and may also be transported northwestward by the Subei Coastal Current (SCC) to the area off the Jiangsu coast. In winter, the Yangtze-derived sediments deposited off the Jiangsu coast in summer are transported into the central and/or even north SYS under the combined effects of the SCC, Yellow Sea Coastal Current (YSCC), and Yellow Sea Warm Current (YSWC). Throughout the transport processes, there is an alternation between a source and sink of Yangtze sediments off the Jiangsu coast; the coast serves as a sink of Yangtze sediments in summer but as a source of SYS sedimentation in winter. The depositional and transport mechanisms of Yangtze-derived sediments are closely associated with seasonal variations in the circulation system of the SYS.

Highlights • Yangtze and Yellow River sediments can be distinguished with SrNd isotope. • Okinawa Trough (OT) sediments derived from the Yangtze River from 18.0 to 10.5 ka. • Yangtze and Yellow River contributed sediment to the OT from 10.5 to 7.0 ka. • Kuroshio Current control Taiwan sediment to the OT after 7.0 ka. • Yellow River sediment was transported to the OT by the coastal current in the last 10.5 ka. Abstract The Okinawa Trough (OT) is a large sink of sediments supplied by the East Asian continent. Identifying the provenance of the OT sediments is key to reconstructing the temporal and spatial variations of the terrigenous supply to this area and is important for understanding the impact of paleoclimatic and paleoceanographic variability on the sediment supply to this marginal sea over the late Quaternary. In this contribution, we show that radiogenic strontium (Sr) and neodymium (Nd) isotopes allow to efficiently distinguish Yellow and Yangtze/Taiwan River detrital sediments, and can be used to reconstruct distinct changes in the provenance of the detrital fraction of marine sediments from the middle and northern OT since the last deglaciation. The Sr and Nd isotope signatures are compared to those of the potential sediment sources, namely the Yellow and Yangtze Rivers, the Taiwan orogen, and volcanic material from the OT and nearby islands, and the relative contributions of these sources are reconstructed. The Sr and Nd isotope compositions of the detrital fraction in the two sediment cores recovered from the middle and northern OT show that the sediments mainly originated from the Yangtze River between 18 and 10.5 ka, which was caused by low sea level and a widely developed channel system on the continental shelf. During the period between 10.5 and 7.0 ka, the rising sea level resulted in elevated Yangtze and Yellow Rivers sediment input into the OT. Simultaneously, large-scale volcanic activity also contributed significant amounts of material to the OT. During the last 7.0 ka, besides important contributions from the Yellow River, the intensification of the Kuroshio Current resulted in increased delivery of sediment from Taiwan to the OT.

Sedimentary responses to the cross-shelf transport on the East China Sea continental shelf are ascertained based on analyses of the sediment grain size and detrital mineral components of surficial sediments. Sedimentological data show that fine-grained sediments can be transported across the continental shelf and have formed a tongue-shaped zone with an axis located near 29°N that extends from the coast to 124°40′E or beyond. The sediments in this tongue-shaped zone are rich in very fine silt and clay, as are the dominant sediment fractions discharged by the modern Yangtze River indicating a modern terrigenous source. Sediment with grain sizes 7–9 Φ is the main fraction that is transported across the continental shelf. In contrast to the regions in the same longitude, in the tongue-shaped zone the relatively low heavy mineral content, high schistose mineral content and high dolomite content and the mixture of fresh and weathered minerals show that modern Yangtze River sediment has been widely transported to this region. Meanwhile, the simultaneous existence of the fine-grained tongue and a coarse-grained area immediately south of the base of the tongue coincident with the nearshore Kuroshio branch current intrusion area indicate that the Kuroshio intrusion plays an important role in triggering the cross-shelf flows.

During the Quaternary, global sea level was characterized by large fluctuations in amplitude and increased frequency. However, the eastern marginal seas of China, especially the northern East China Sea and Yellow Sea did not experience large-scale transgression until the middle Pleistocene. The Zhe-Min (Zhejiang-Fujian) Uplift was an important barrier in the East China Sea preventing transgression of sea water into the northern marginal seas of China, but its Quaternary evolution is still poorly constrained. Here we present a thick sand layer record (the top age is ~416 ka) of the Integrated Ocean Drilling Program (IODP) Site U1428 from the northern Okinawa Trough to reconstruct the history of the Zhe-Min Uplift since the middle Pleistocene. Provenance analysis indicates that sediments from both sand and imbedded fine-grained calcareous-rich clay layers at the study site were mainly derived from the Yellow River, which for the first time indicates that the Yellow River sediments could influence the northern Okinawa Trough since at least the middle Pleistocene. Significant change of lithology at IODP Site U1428 at ~416 ka was attributed to the large-scale subsidence of the Zhe-Min Uplift, which is probably due to the rapid uplifting of Tibet during 0.52–0.38 Ma. Before ~416 ka, obstacle of the emersed Zhe-Min Uplift induced extremely severe reworking and promoted sand ridge formation in the shelf edge of southeastern Yellow Sea, and supplied sand sediments to the northern Okinawa Trough during transgression and high sea-level stages. After the subsidence of the Zhe-Min Uplift at ~416 ka, westward of tidal sand ridge and Yellow River mouth with the process of shelf transgressions favored fine-grained sediments input to the northern Okinawa Trough. Even during low sea-level stages, the flat terrain of the East Asian marginal sea shelf and low rainfall amount resulted in low discharge of Yellow River, and supplied fine-grained particles to the northern Okinawa Trough.

Eolian dust deposition is crucial to paleoclimate reconstructions of dust source areas and may have played an important role in the climate during the mid-Pleistocene transition (MPT). Here, we present the radiogenic Sr and Nd isotopic composition and excess barium (Baxs) of a sediment core that was recovered from the Parece Vela Basin (PVB) in the northwestern Pacific. The new record indicates that these detrital sediments are primarily composed of dust from western and central Chinese deserts and volcanic materials from the islands in and around the PVB. A two end-member Sr isotope model was applied to distinguish Asian dust from volcanic materials and to reconstruct the mass accumulation rates (MARs) of dust over the last 2.1 Myr. Starting at ~1.2 Myr, the dust MARs doubled relative to those in the Early Pleistocene, which was coupled with the frequent congruence of minimum eccentricity and low obliquity. We argue that the congruent minimum eccentricity and low obliquity may have triggered the climate change before and during the MPT and resulted in the aridity of East Asia and increased dust input. The coupling of dust MAR, Baxs MAR and atmospheric CO2 concentration and their rapid increase since the MPT strongly suggest that the internal positive feedback of dust input might be another mechanism behind dust input to the PVB since the MPT.

Isotopic compositions of coeval sulfide and sulfate have been widely employed to reconstruct the seawater chemistry evolution over geologic time; however, these signals can be modulated by other factors, such as the sedimentation rate. Here, we present a data set of pyrite sulfur isotopes (δ34Spy) derived from 60-m drilled core sediments deposited on the inner shelf of the East China Sea since 16.5 ka. The resulting δ34Spy values range from −38.2 to 15.0‰ (Vienna Canyon Diablo Troilite; V-CDT), representing a range of 53.2‰. Freshwater deposition before 12.3 ka produced a limited pyrite abundance and δ34Spy values that fall within the typical range of freshwater environments. After the marine incursion in the study area at 12.3 ka, variations in the δ34Spy values become significantly correlated with sedimentation rates (SRs; r = 0.78, p 0‰), suggesting that SRs exert controls on δ34Spy values. We propose that these sedimentary controls are expressed by modulating the connectivity between porewaters and the overlying seawater. Low SRs tend to form an open diagenetic system, in which the pyrites are able to preserve the large biological fractionations associated with microbial sulfate reduction (and disproportionation). In contrast, high SRs favour a restricted diagenetic system, in which the distillation of porewater sulfate produces pyrites enriched in 34S, masking the magnitude of biological fractionation during microbial sulfur cycling. These findings highlight the critical effect of the local sedimentation regime on pyrite sulfur isotopic compositions, especially within shallow depositional environments, over geologic time.

The sea-level curve during the last deglaciation is characterized by two episodes of rapid sea-level rise, termed Meltwater Pulses (MWPs) 1A (14.6–14.3 kyr BP) and 1B (11.45–11.1 kyr BP), as well as an episode of relatively slow sea-level rise during the Younger Dryas stadial (YD; 12.85–11.65 kyr BP). However, the relative sea-level changes during the YD and MWP-1B periods are still not well defined. Here, we use precisely dated intertidal sediments derived from 6 sediment cores on the tectonically stable continental shelf of the East China Sea (ECS) to reconstruct a high-resolution sea-level curve between 14.0 kyr BP and 10.0 kyr BP. Although linear regression analysis suggests that the sea level rose continuously, with an average rate of 10.6 ± 0.6 mm/yr (r = −0.87, p(a)

The suspended sediment transport in the inner shelf of the East China Sea (ECS) varies seasonally, and most of the suspended sediments are transported southward in winter. However, the influence of typhoons, which usually take place in summer, on the marine environments and sediment transport processes in the mud wedge area of the ECS inner shelf has not been elucidated. An in-situ monitoring platform moored approximately 440 km south of the Yangtze River mouth at a water depth of 40 m was resting on the seabed of the ECS inner shelf when Typhoon Chan-hom passed through the area. A 49-day data set of the temperature, suspended sediment concentration (SSC), chlorophyll a (chl a) concentration, and currents was recorded from this platform and analyzed in this study to characterize Typhoon Chan-hom and evaluate the associated sediment transport. The analysis of the data obtained shows that during the typhoon passage, the temperature decreased by approximately 0.8 °C, the maximum near-bottom current reached 152.0 cm/s, an average SSC of 919 mg/L was observed with peak hourly values exceeding 1785 mg/L, and the SSC and chl a concentrations reached approximately 50 and 10 times the corresponding values during the pre-typhoon period, respectively. During the typhoon passage, most of the suspended particles near the seabed were derived from the resuspension of bottom surface sediments. The chl a concentration near the seabed increased greatly because of surface sediment resuspension and the input of additional terrigenous nutrients transported by the typhoon passage. The net suspended sediment flux (SSF) associated with the passage of Typhoon Chan-hom was directed southwestward and landward. Sediment transport during Chan-hom accounted for approximately 89% of the total southwestward SSF and 44% of the total landward SSF during the whole observation period. Analysis of the wavelet power spectra reveals that in the upper water layers, the semidiurnal tidal currents prevailed before and after the typhoon passage; however, this dominant factor disappeared during the typhoon passage. Compared with winter storms in the ECS, summer typhoons such as Chan-hom mainly transport locally resuspended sediments, and sediment flux is landward in the across-shelf direction. Our study highlights the significant role of typhoons in the resuspension and redistribution of sediments and transport of suspended matter from north to south in the mud wedge area of the ECS.

Gypsum (CaSO4 center dot 2H(2)O) precipitated in nonevaporative marine environments is rarely reported, and the related diagenetic process and its implications for the sulfur cycle (e.g., sulfide reoxidation) are still not well known. We employ coupled sulfur and oxygen isotopes of authigenic gypsum, as well as sulfur isotopic compositions of pyrite, from core EC2005, which is drilled on the inner shelf of the East China Sea, to constrain the sulfur and oxygen sources for gypsum precipitation. The delta S-34(gypsum) values range from -24.8 to -12.2 parts per thousand, which are much more depleted in S-34 than modem seawater sulfate, suggesting additional S-34-depleted sulfur sources, i.e., coexisting pyrites produced by microbial sulfate reduction. According to a mixing model for paired sulfur isotopes of gypsum and pyrite, > 70% of gypsum sulfur is derived from pyrite reoxidation. The delta O-18(gypsum) values, ranging from 1.1 to 4.6 parts per thousand, suggest that the oxygen isotopes of porewater sulfate should fall between -2.4 and 1.1 parts per thousand, which are more depleted than seawater sulfate in O-18. Two mechanisms are proposed to explain the reoxidation of pyrite at different depths: in the lower section (10-4 m; Unit II), pyrite is oxidized by metal oxides under anaerobic conditions, producing O-18-depleted oxygen from seawater; while in the upper section (4-0 m; Unit I), pyrite reoxidation may occur under aerobic conditions, involving atmospheric oxygen. Either the aerobic or anaerobic mechanisms could cause drops in the porewater pH, leading to carbonate dissolution. These processes could therefore elevate the concentrations of sulfate and calcium ions in porewater, in which authigenic gypsum crystals are precipitated. In addition, both sulfur and oxygen isotopic signals of gypsum indicate a possible influence of methane on sulfate reduction in the mud sediments of core EC2005, which may be related to biogenic gas (dominated by CH4) in this region. Our new findings thus indicate that sulfide reoxidation in marine sediments plays an important role in the biogeochemical sulfur cycle on the continental margin.

This study examines how geochemical signals regarding the source and transformation in suspended particles are transported in the marine portion of the sediment dispersal system. In the source-to-sink sedimentary continuum of a world major river, the Changjiang (Yangtze) River, is used to demonstrate the close coupling between the marine physical processes and the geochemical signals carried by suspended particles. A sediment trap mooring configured with a non-sequential sediment trap, a downward-looking ADCP, CTD, LISST-100× were deployed for 29 days in the winter of 2014 off the coast of Zhejiang Province, China in water depth of 22.5 m. The mooring rendered two types of data. Physical processes included temporal changes of water depth, currents at 11 depths, temperature at two depths, and salinity at one depth. There was 15-cm accumulation of captured particles in the trap, which rendered the total mass flux of 233.3 g/cm2/day. The trap material was analyzed for grain-size composition, total 210Pb, minerals including mica/illite, kaolinite, chlorite, k-feldspar, plagioclase, quartz, and dolomite. Organic material (TOC, TN) and carbon isotope δ13C were also measured. The range of terrestrial fraction (Ft) of the trap material was between 45–60%. EOF analysis was used to examine the covariability in both data sets. For the physical data set, 37 variables were used in the analysis. For the sediment trap material, 15 variables were used. The EOF results of the physical processes indicate the tidal flow was the most important physical forcing for the transport of suspended particles and water masses that carried marine- and terrestrial-sourced particles. Wave and current combined resuspension entrained reworked sediment off the seabed, which was then transported landward or seaward. The most important covariability of the particle properties in the sediment trap was caused by hydrodynamic sorting that separated the clay from silt and sand sizes. Geochemical signals of the particles were carried by clay and the particle mass (dry weight) was associated with silt and sand. The temporal characteristics of the sorting show the spring-neap tidal cycle. The next major distinction was the contrast between terrestrial- and marine-sourced materials. The EOF analysis further distinguish contributions from the distal Changjiang River and proximal small rivers at the tertiary level of the covariability. The coverabilities in both data sets show close correspondence. Our findings give firm evidence to show marine processes dominated the transport of land-derived fluvial sediment and the incorporation of marine-sourced particles into the dispersal system. There is complexity in both physical processes and geochemical signals of suspended particles. However, our study points out the close coupling between the two.

Surface sediment and box core samples collected from the East China Sea (ECS) inner shelf mud area before and after Typhoon Talim (2017) were analyzed for grain size, chemical elements, and heavy metals (Cr, Ni, Cu, Zn, and Pb). By comparing the results of the survey in May with those in September, we distinguished the possible sources of heavy metals, assessed heavy metal contamination status, and elucidated the impacts of summer typhoons on the distribution of heavy metals. The results of the enrichment factor (EF) and geoaccumulation index (Igeo) showed that Cr, Ni, Zn and Pb were mainly derived from natural sources, while Cu was partly influenced by anthropogenic activities and showed minor to moderate pollution. The difference between the minimum and maximum values of heavy metals became larger after the typhoon. The distribution of heavy metals in surface sediments was positively correlated with grain sizes of 11–18 μm, while the distribution in box cores was positively correlated with grain sizes of 0.8–12 μm. Additionally, the correlation between heavy metals (except Cu in box cores) and specific grain sizes increased after the typhoon passage. The thickness of the storm layer caused by Typhoon Talim was 16 cm, and the erosion depth was 4 cm. The stations with high and low values of the enrichment factor of typhoons (EFt) were separated from each other, indicating that heavy metal pollution increased at some stations and decreased at others after Typhoon Talim. The impact of typhoons on heavy metal pollution is related to seabed erosion and deposition. Summer typhoons can play a great role in the redistribution and burial of heavy metals, which is significant in the marine environment of the ECS.

The East China Sea continental shelf is a unique area for the study of land-sea interactions and paleoenvironmental change because it receives a large amount of terrestrial material inputs. In recent decades, human activities and global climate change have greatly affected river discharges into the sea. However, changes in the deposition process caused by these factors in the East China Sea continental shelf are unclear. We collected eight short sediment cores from the East China Sea inner shelf (ECSIS) using a box core sampler in 2012 and 2015. The grainsize, 210 Pb, and 137 Cs of these cores were analyzed in order to reconstruct the deposition history since the 1950s, and to reveal human activity and climate change influences on sediment deposition in the ECSIS. Results indicated that sediment grain size became finer after 1969, turned coarser after 1987, and then further coarser since 2003, corresponding well to the three steps of sediment load drop in the Changjiang (Yangtze) River, which are mainly caused by human activities (particularly the closure of the Three Gorges Dam). Simultaneously, the East Asian Monsoon influenced the deposition process in the ECSIS by changing the intensity of coastal currents. Mean grain size variations in the fine-grained population (divided by grain size vs. standard deviation method) coincided with that of the East Asian Winter Monsoon strength and reflected its weakness in 1987. Abrupt changes in sediment grain size over a short time scale in these sediment cores were generally caused by floods and typhoons. Spectral analyses of the sediment cores showed periodicities of 10–11 and 20–22 years, corresponding to the periodicity of solar activity (Schwabe cycle and Hale cycle). Mean grain size time series also displayed a 3–8 year periodicity corresponding to El Nino Southern Oscillation periodic change.

High resolution multi-proxy records, including geochemical and grain-size data from detrital sediments of IODP Site U1429 in the northern Okinawa Trough, provide reliable evidence for constraining sediment source and transport processes. They also allow silicate weathering and erosion controlled by sea-level change and East Asian summer monsoon evolution since 34 ka to be reconstructed. Provenance proxies indicated that sediments in the northern Okinawa Trough were mainly supplied by the Yellow River middle reach at ~ 34–8 ka. The low sea level and proximity of paleo-Yellow River mouth to the northern Okinawa Trough were the causes of the dominant Yellow River input. After ~ 8 ka, a retreated Yellow River mouth coupled with the blocking effect of the Kuroshio Current and its branches, together with strong East Asian summer monsoon precipitation resulted in relatively strong sediment input from Kyushu to the northern Okinawa Trough. Meanwhile, Yellow River upper reach supplied more sediments to the study site than that during the ~ 34–8 ka. On glacial-interglacial scale, silicate weathering proxies indicate that the core sediment was more weathered during the last glacial and deglacial than that in the modern Yellow River. We attribute this to the increased upper reach sediment input, which supplied more weak weathered sediment to the study site during the Holocene. Besides, composite effect of weathering during glacial and deglacial sediment production and additional weathering upon subaerial exposure of shelf deposits during low sea-level stage, as well as older weathered sediments reworking during sea-level rise could also account for this weathering regime. On multi-millennial scale, from ~ 34 to 18.5 ka, silicate weathering was mainly controlled by the East Asian summer monsoon, with a cooling and drying climate associated with weakened summer monsoon activity. This is consistent with the reduced alteration of sediments eroded from the Yellow River basin. From ~ 18.5 to 8 ka, strong reworking of older weathered sediments overwhelmed the East Asian summer monsoon in controlling silicate weathering, which induced a continuous increase in chemical alteration of the sediments during this period.

In the past decade, the 800 km elongated mud belt off Zhejiang-Fujian coast, East China Sea (ECS), has been extensively studied for understanding the source to sink processes on the East Asian continental margin in the context of the Asian monsoon. However, to better understand the sediment source and dispersal pattern, the existing mineralogical and geochemical data of adjacent river systems, including the Changjiang River (CJR) and local rivers in Zhejiang, Fujian and Taiwan, need to be systematically reviewed. Therefore, various indicators from published literatures for the provenance discrimination in the mud belt have been summarised in this article. The results show that high diversity of clay mineral assemblages in fluvial sediments being supplied into the mud belt, e.g., dominant illite and chlorite in the CJR, absence of smectite in Taiwan rivers, similar amounts of the four clay mineral species in Zhejiang rivers, and dominant kaolinite in Fujian rivers. On heavy mineralogy, the CJR is dominated by dolomite, hornblende, and flaky minerals; and among of them, dolomite is distinctive for the CJR. For geochemical approaches, elemental compositions, combined with strontium and neodymium isotopes, reflect strong provenance control. However, geochemical and mineralogical compositions are found to vary with grain size, and thus extra caution should be taken when using these parameters as provenance indicator to discriminate the marine sediments with variety of grain-size fractions. In addition, pyrrhotite, occurred in fluvial sediments from western Taiwan, has not been found in sediments derived from mainland China, indicating that magnetic parameters could be used to discriminate sediment provenance. The mud belt formed during sea-level highstand, when modern current system in the ECS has been established, resulting in sediments derived from the CJR have been transported southward since 8 ka. In addition, sediment provenances have not been constant since initiation of the mud belt in response to climatic and oceanographic changes during the Holocene, which has been documented by mineral and geochemical signals. Nevertheless significant studies have been carried out, to better understand the formation mechanism for the mud belt and its implications for environmental changes, further studies on sediment provenance throughout the Holocene, in situ observation, and sedimentation dynamical modelling are required.

The heavy mineral composition and sensitive grain size changes from core SS4 retrieved from the mud wedge on the East China Sea inner shelf have been studied for better understanding provenance variations in the sediment and climate changes during the last ~1500 yr. High dolomite content and occurrence of ubiquitous polysynthetic mica indicate that the sediments in core SS4 were mainly derived from the Yangtze River, while the relatively high epidote content represent the contribution of small local rivers from Zhejiang and Fujian provinces. The substantial decrease in the epidote/hornblende ratio since ~730 yr BP manifests a decline in the relative contribution of sediment from the small local rivers to the core. We propose that the changes in drought/flood conditions in response to the East Asian winter monsoon (EAWM) and human activities might have been mainly responsible for changes in sedimentary characteristics. During 1400–730 yr BP, the core sediments were characterized by relatively finer sensitive grain size and high epidote/hornblende ratio, due to a possibly weaker EAWM (i.e., less Yangtze River-derived sediment transported by the southward coast current). This time interval coincides with the Sui-Tang Warm Period (1400–1130 yr BP) in China and the Medieval Warm Period (1000–730 yr BP) on a broader regional scale. The prolonged warm periods were, however, interrupted by three short cold phases at 1350–1280 yr BP, 1130–1000 yr BP and 870–750 yr BP, characterized by coarse sensitive grain size and decreased epidote/hornblende ratio. Between 360 and 150 yr BP, the sensitive grain size significantly coarsened, which corresponded to the Little Ice Age. Our new findings suggest that sedimentation processes of mud wedge formation are responsive to natural environmental change and human activity.

Modern source-to-sink processes in the southern South China Sea (SCS) remain poorly understood. In this study, clay minerals and magnetic properties are used to identify the sources and transport pathways of surface sediments in the southern SCS. The distributions of four clay mineral species in the deep southern SCS are mainly controlled by sediment sources, while clay minerals on the outer Sunda Shelf mostly reflect reworking/recycling of older weathered sediments. Clay mineral analyses indicate that the Mekong River is the predominant contributor of clay minerals to the southern SCS, with minor contributions from Luzon and/or Palawan and northern Borneo. The contribution from the Luzon and/or Palawan arc to the southern SCS is semi-quantitatively evaluated as 20% and is mainly smectite. Most sediments in the southern SCS are magnetically dominated by mixtures of magnetite, hematite and goethite in variable proportions. Concentration-dependent magnetic parameters decrease gradually seaward and then sharply towards the outer deep sea. The grain size of magnetite particles also shows a significant fining trend with distance from the southwestern sources. In addition, the magnetic minerals change from hematite- and goethite-dominated to magnetite-dominated type as going further offshore. These magnetic characteristics suggest that the magnetic minerals in the southern SCS are mainly sourced from the southwest through summer monsoon-driven surface currents. Finally, combining the provenance signature indicated by clay minerals and the transport information revealed by magnetic properties, this study highlights that the Mekong River plays a major role in modern source-to-sink processes in the southern SCS. In brief, our study sets a good example for tracing sediment provenance and transport in other marginal seas worldwide.

The East China Sea (ECS) is susceptible to summer typhoons, which play an important role in sediment transport and reworking on the continental shelf. However, because observations during typhoon passage are difficult to carry out even at present, the influence of typhoons on sedimentary records in the ECS is not fully understood. In this study, we compared the elemental compositions and grain-size distributions of surface sediments collected before and after the passage of Typhoon Talim. Through end-member modeling algorithm (EMMA) analysis, the variations in sediment composition due to the typhoon passage were characterized, and the impacts of typhoons on sediment migration, redistribution and sedimentary records on the ECS continental shelf were elucidated. Comparison of the results revealed that after the passage of Typhoon Talim, the clay distributions were generally parallel to the coastline, the sand contents in the northeast and southeast of the study area decreased, and the sorting coefficient decreased in the inner shelf mud area and increased in the relict sand area. The three-end-member model was capable of adequately reproducing all variables, and the three end members were interpreted to be the fine-grained components of river terrigenous sediments (EM1), mixed sediments (EM2), and relict sands (EM3) according to the grain-size and chemical element composition characteristics of surface sediments. Summer typhoons can interrupt the cross-shelf transport of fine-grained sediments caused by cross-shelf penetrating fronts (CPFs) and can promote exchange between fine-grained sediments and relict sands on the ECS continental shelf. Thus, summer typhoons play a vital role in retaining the mud on the ECS inner shelf and redistributing the sediments on the ECS continental shelf.

Human–environment interactions across historical periods in China have been well reconstructed over the past decade; however, few studies have focused on southern China, particularly Hainan Island....

International audience; We present high-resolution analyses of clay mineral assemblages combined with analysis of Sr–Nd–Pb isotopic compositions of the

The late Quaternary paleoceanography and paleoenvironment of the South China Sea (SCS) have been well reconstructed over the last decade. In contrast, the provenance of the terrigenous sediments that have accumulated in the northwestern continental shelf mud area remains enigmatic. This study investigated the provenance of these sediments and the paleoenvironmental changes archived in Core X2 via the analysis of geochemical elements, grain size, and accelerator mass spectrometry (AMS) 14 C ages. Based on the upper continental crust (UCC)-normalized REE patterns and REE fractionation parameters, southwestern and western Taiwanese rivers and the Pearl River were identified as the main sources of the fine-grained sediment deposited in the northwestern shelf mud area off Hainan Island. This finding further confirms the long-distance transport (> 1000 km) of fine-grained sediment from Taiwanese rivers to the northern SCS shelf and slope. Obvious changes in the grain size and Chemical Index of Alteration (CIA) record occurred at approximately 4.0 cal kyr BP and were likely caused by increased Hainan Island inputs due to sea level changes.

Quaternary East Asian winter monsoon (EAWM) evolution has long been attributed to high-latitude Northern Hemisphere climate change. However, it cannot explain the distinct relationships of the EAWM in the northern and southern East Asian marginal sea in paleoclimatic records. Here we present an EAWM record of the northern East China Sea over the past 300 ka and a transient climate simulation with the Kiel Climate Model through the Holocene. Both proxy record and simulation suggest anticorrelated long-term EAWM evolution between the northern East China Sea and the South China Sea. We suggest that this spatial discrepancy of EAWM can be interpreted as El Niño–Southern Oscillation (ENSO)-like controlling, which generates cyclonic/anticyclonic wind anomalies in the northern/southern East Asian marginal sea. This research explains much of the controversy in nonorbital scale variability of Quaternary EAWM records in the East Asian marginal sea and supports a potent role of tropical forcing in East Asian winter climate change.

Both the East Asian winter monsoon (EAWM) and El Nino (EN) activities are vital climate modes that regulate the Pacific hydrologic cycle. However, the Holocene interactions among the EAWM, EN activities, and tropical Pacific precipitation remain unclear due to the lack of appropriate EAWM proxies. Here, we present high-resolution grain size records from the East China Sea shelf along with a transient climate model simulation to study the Holocene EAWM evolution and compare the findings with paleo-EN precipitation-related proxies records. The millennial-scale oscillations of grain size records, which are indicative of the intensity of the EAWM-driven coastal current, reveal an anti-phase coupling between the EAWM and EN-related tropical Pacific precipitation on a millennial timescale since 5.8 ka. These results, which are consistent with simulation results, indicate that the intensified EAWM could not only reduce equatorial western Pacific precipitation by reducing the sea surface temperature but also likely change boundary conditions in the tropical Pacific (i.e., the east-west Pacific temperature gradient and westerly anomaly) to favor the formation of subsequent intensive EN activities. The enhanced EN activities, inferred by the positive tropical eastern Pacific precipitation anomalies, could subsequently suppress the EAWM through anomalous low-level anticyclones and associated southerly anomalies, thereby generating intensified tropical western Pacific (mainly tropical monsoon areas) precipitation. Our study highlights these intrinsic interactions during the mid- to late Holocene and has useful implications for understanding this millennial-scale climate oscillation, which may represent periodic atmospheric exchange between high- and low-latitude climate systems by mediating the EAWM.

International audience; Reconstructing the Cenozoic sedimentary history of the Bay of Bengal (BoB) is significant for understanding the evolutionary history of South Asian river systems and the links between river development, tectonic deformation and global climate change. Here, we present the first long-term clay mineral record combined with Sr-Nd isotopic compositions from a 200-m-long sediment core from Ocean Drilling Program (ODP) Site 758 in the southern BoB to establish past variations in sediment sources and river evolution that have occurred since the late Eocene. Provenance analysis suggests that the contribution of the Himalayan source materials from the Irrawaddy and Brahmaputra Rivers to the study site became more important and stable since 22 Ma and 8 Ma, respectively. This new evidence indicates that the Brahmaputra and Irrawaddy Rivers were possibly initiated in the early Miocene (~22 Ma). Considering the timing of major tectonic and climatic evolution in South Asia, we conclude that the two phases of tectonic uplift of the Himalayan orogen that occurred in the early and late Miocene were the primary controls on river development in South Asia and provenance changes in the southern BoB. Global cooling and Indian drying after the late Miocene could also have strengthened Himalayan erosion and contributed more illite and chlorite to the South Asian margin.

The Kuroshio Current (KC) is the northward branch of the North Pacific subtropical gyre (NPG) and exerts influence on the exchange of physical, chemical, and biological properties of downstream regions in the Pacific Ocean. Resolving long-term changes in the flow of the KC water masses is, therefore, crucial for advancing our understanding of the Pacific's role in global ocean and climate variability. Here, we reconstruct changes in KC dynamics over the past 20 ka based on grain-size spectra, clay mineral, and Sr–Nd isotope constraints of sediments from the northern Okinawa Trough. Combined with published sediment records surrounding the NPG, we suggest that the KC remained in the Okinawa Trough throughout the Last Glacial Maximum. Together with Earth-System-Model simulations, our results additionally indicate that KC intensified considerably during the early Holocene (EH). The synchronous establishment of the KC “water barrier” and the modern circulation pattern during the EH highstand shaped the sediment transport patterns. This is ascribed to the precession-induced increase in the occurrence of La Nina-like state and the strength of the East Asian summer monsoon. The synchronicity of the shifts in the intensity of the KC, Kuroshio extension, and El Nino/La Nina-Southern Oscillation (ENSO) variability may further indicate that the western branch of the NPG has been subject to basin-scale changes in wind stress curl over the North Pacific in response to low-latitude insolation. Superimposed on this long-term trend are high-amplitude, large century, and millennial-scale variations during last 5 ka, which are ascribed to the advent of modern ENSO when the equatorial oceans experienced stronger insolation during the boreal winter.