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Shelf mud is an important sink for fluvial sediment, and it is sensitive to variations in river discharge and ocean circulation, which are significantly influenced by climate change. However, the evolution of shelf mud in response to climate change during the Holocene is poorly understood. Here, we present high‐resolution sedimentary records of heavy minerals and mass accumulation rates (MARs) from the East China Sea shelf to study the response mechanisms of the Holocene shelf mud supply, transport, and sedimentation to the climate‐driven variations in fluvial discharge and ocean currents. The results indicate that the shelf mud primarily originates from the Changjiang (Yangtze) River and has been mainly transported by wind‐driven longshore currents in suspension since approximately 8.0 ka. A comparison of the MARs with several shelf mud sedimentation‐rate records and climate changes during the Holocene on millennial timescales showed that strong (weak) precipitation in the river basin, which is positively linked with Asian summer monsoon and El Niño‐driven storms, could intensify (weaken) the fluvial sediment supply, thereby increasing (decreasing) the shelf mud deposition flux. On multicentennial timescales, changes in the relative intensities of different ocean currents due to climate oscillations during the Holocene could generate frequent migrations of the current shear front (a hydrodynamic barrier), which has trapped an abundance of suspended materials on the shoreward side and resulted in rapid mud sedimentation (~2.3 g/cm2/year) at different sites during different periods. Therefore, our study highlights that the Holocene shelf mud evolution responds sensitively to climate changes on different timescales. Key Points: The Changjiang River mud has been mainly carried southward by wind‐driven longshore currents since 8.0 kaHolocene shelf mud supply is modulated by precipitation from summer monsoons and El Niño‐related stormsHolocene rapid shelf mud sedimentation is directly linked with climate‐driven migrations of ocean currents [ABSTRACT FROM AUTHOR]

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. Plain Language Summary: The modern East Asian winter monsoon (EAWM) is influenced by the combined effects of both the high‐latitude Northern Hemisphere (e.g., Siberian High) and the low‐latitude Western Pacific (e.g., El Niño–Southern Oscillation) and plays a major role in regulating atmospheric energy of East Asia and even the Northern Hemisphere. Its anomalies may cause extremely cold/warm winter weather or climate events, which result in profound societal and economic influences on the densely populated region of East Asia. Especially, some studies found the EAWM displays spatial discrepancies in northern and southern East Asia and can result in a colder/warmer north corresponding to a warmer/colder south. Our study shows anticorrelations of EAWM evolution between the northern East Asian marginal sea and the South China Sea since the late Quaternary. We suggest that such spatial discrepancies of EAWM evolution were controlled by El Niño–Southern Oscillation‐like processes in the tropical Pacific. During El Niño‐like conditions, the anomalous northwesterlies in the northern East Asian marginal sea led to a strengthened EAWM in this region. In contrast, anomalous southwesterlies in the South China Sea favored the occurrence of a weakened EAWM. The opposite situation occurred under La Niña‐like conditions. Key Points: Clay minerals in northern Okinawa Trough were derived from Yellow River and KyushuReversed EAWM evolution in the northern and southern East Asian marginal sea was revealedENSO‐like processes cause spatial discrepancy of Quaternary EAWM evolution [ABSTRACT FROM AUTHOR]

Abstract 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. Graphical abstract Unlabelled Image Highlights • Sedimentological data demonstrate cross-shelf transport in the East China Sea. • Sediment grain size and mineral distributions show apparent cross-shelf transport. • Cross-shelf transport occurs in a relatively fixed location near 29°N. • Fine-grained sediment can be transported cross-shelf to 124°40′E or even farther. • Kuroshio intrusion is an important factor that triggers the cross-shelf flows. [ABSTRACT FROM AUTHOR]

Abstract Gypsum (CaSO 4 ∙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 δ34S gypsum values range from −24.8 to −12.2‰, which are much more depleted in 34S than modern seawater sulfate, suggesting additional 34S-depleted sulfur sources, i.e., co-existing 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 δ18O gypsum values, ranging from 1.1 to 4.6‰, suggest that the oxygen isotopes of porewater sulfate should fall between −2.4 and 1.1‰, which are more depleted than seawater sulfate in 18O. 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 18O-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 CH 4) 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. Highlights • Coexistence of pyrite and gypsum in mud sediments on the East China Sea shelf. • Pyrite oxidation is the primary sulfur source for gypsum precipitation. • Gypsum oxygen derived from seawater oxygen rather than seawater sulfate. • Gypsum formation accompanied by carbonate dissolution caused by sulfide oxidation. [ABSTRACT FROM AUTHOR]

Surface sediment samples collected from the South Yellow Sea and northern part of the East China Sea during spring and autumn, respectively, were analyzed for grain size, aluminum, and heavy metals (Cr, Ni, Cu, Zn, and Pb) to evaluate heavy metal levels and the contamination status. The results showed that all of the heavy metal concentrations met the standard criteria of the Chinese National Standard Criteria for Marine Sediment Quality. Both the EFs and a multivariate analysis (PCA) indicated that Cr, Ni, Cu, and Zn were mainly from natural contributions, while Pb was influenced by anthropogenic inputs, especially during autumn. The geoaccumulation index of Pb near the mouth of the Yangtze River suggested that the pollution degree in autumn was heavier than that in spring, which might be caused by the greater river discharge in summer and more heavy metal adsorption with finer grain sizes. [ABSTRACT FROM AUTHOR]

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 (I geo) 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 (EF t) 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. ● Grain size and heavy metals were analyzed before and after Typhoon Talim. ● Copper was partly influenced by anthropogenic activities. ● The thickness of the storm layer caused by Typhoon Talim was 16 cm. ● The typhoon impact on heavy metals was related to seabed erosion and deposition. [ABSTRACT FROM AUTHOR]

Abstract: Surficial grain-size and down-core clay mineralogical data show that sediment along the inner-most part of the continental shelf in East China Sea is mainly derived from the Yangtze River (Changjiang), spanning from the Yangtze mouth (33°N) ~1000km southward to the southwestern corner of the Taiwan Strait (24°N). High-resolution CHIRP seismic profiles reveal an elongated mud wedge extending along the inner shelf, with a northern depocenter on the modern Yangtze delta and a southern depocenter at 27.5°N. Four distinct acoustic units are delineated within the mud wedge (from bottom up): unit I (late-Pleistocene, mainly valley fills), unit II (formed by transgressions, thin strata), unit III (11–2kyr BP, downlapping strata) and unit IV (2–0kyr BP, flat and opaque strata). Incised valleys, up to 15-m deep, are filled by flat-lying or inclined strata in unit I. The thin (<3m) and acoustically transparent unit II is only seen between 30 and 26°N in water depths between 40 and 90m. Separated by acoustically opaque strata or unconformities, units III and IV are widely distributed. During the past 11kyr Yangtze sediment accumulation has been unsteady, showing two high and one low accumulation-rate periods. The high-accumulation period at 5–8kyr BP may be related to maximum East Asian summer monsoon precipitation in the Yangtze basin; the other high-accumulation period, 0–2kyr BP, probably reflects intensive human activities in the river''s watershed. The low-accumulation-rate period at 2–5kyr BP, which is seen in both northern and southern Yangtze depocenters, is probably related to low river discharge and/or intensified Taiwan Warm Current and China Coastal Current. [Copyright &y& Elsevier]

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. • Grain sizes of surface sediments were analyzed before and after Typhoon Talim. • Three grain-size end members were discerned by EMMA analysis. • The cross-shelf transport of sediments could be interrupted by summer typhoons. • Summer typhoons promoted the exchange of sediments on the ECS shelf. [ABSTRACT FROM AUTHOR]

Abstract: AMS14C dating and grain-size analysis for Core PC-6, located in the middle of a mud area on the inner shelf of the East China Sea (ECS), were used to rebuild the Holocene history of the East Asian winter monsoon (EAWM). The 7.5-m core recorded the history of environmental changes during the postglacial transgression. The core’s mud section (the upper 450 cm) has been formed mainly by suspended sediment delivered from the Yangtze River mouth by the ECS Winter Coastal Current (ECSWCC) since 7.6 kyr BP. Using a mathematical method called “grain size vs. standard deviation”, we can divide the Core PC-6’s grain-size distribution into two populations at about 28 μm. The fine population (<28 μm) is considered to be transported by the ECSWCC as suspended loads. Content of the fine population changes little and represents a stable sedimentary environment in accord with the present situation. Thus, variation of mean grain-size from the fine population would reflect the strength of ECSWCC, which is mainly controlled by the East Asian winter monsoon. Abrupt increasing mean grain size in the mud section is inferred to be transported by sudden strengthened ECSWCC, which was caused by the strengthened EAWM. Thus, the high resolution mean grain-size variation might serve as a proxy for reconstruction of the EAWM. A good correlation between sunspot change and the mean grain-size of suspended fine population suggests that one of the primary controls on centennial- to decadal-scale changes of the EAWM in the past 8 ka is the variations of sun irradiance, i.e., the EAWM will increase in intensity when the number of sunspots decreases. Spectral analyses of the mean grain-size time series of Core PC-6 show statistically significant periodicities centering on 2463, 1368, 128, 106, 100, 88-91, 76-78, and 70-72 years. The EAWM and the East Asian summer monsoon (EASM) agree with each other well on these cycles, and the East Asian Monsoon (EAM) and the Indian Monsoon also share in concurrent cycles in Holocene, which are in accord with the changes of the sun irradiance. [Copyright &y& Elsevier]

Both the East Asian winter monsoon (EAWM) and El Niño (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. • Holocene millennial-scale oscillation of the EAWM is recorded by grain size data. • Anti-phase interaction between EAWM and tropical Pacific rainfall since 5.8 ka. • The intensified EAWM could suppress the tropical Pacific precipitation. • The high El Niño activities enhance the western Pacific rainfall by weakening the EAWM. [ABSTRACT FROM AUTHOR]

[Display omitted] • Al/Si ratios can be used to correct CIA values to avoid the influence of grain-size sorting. • CIA values decreased during the YD, 8.2 ka, and 4.2 ka cold events during the Holocene. • Chemical weathering could be enhanced due to shelf exposure when the sea level is low. • Chemical weathering shelf sediments could rapidly respond to abrupt climate events. Chemical weathering of shelf sediments is important in driving the global elemental cycle and climate to maintain the earth's habitability. However, the response mechanism between chemical weathering of shelf sediments and climate and sea-level changes is still unclear. This study focuses on core ECMZ located in the mud area of the East China Sea (ECS) inner shelf. The results indicate that the mechanisms controlling chemical weathering in the sediment of the ECS inner shelf differ at different timescales. On the orbital time scale, the Chemical Index of Alteration (CIA) indicates that the intensity of chemical weathering in sediments during the deglacial period was significantly higher than that during the Holocene. This was caused by shelf exposure during low sea-level periods when the sediments were fully exposed and the residence time in the weathering zone was long, leading the shelf sediments to undergo consistent and complete weathering under supply-limited conditions. In comparison, during cold events on the millennium-centennial time scale, such as Younger Dryas, 8.2 ka, and 4.2 ka, chemical weathering was weaker (lower CIA values) due to accelerated erosion as a result of lower temperatures and higher precipitation, which shortened the rocks' residence in the weathering zone, resulting in the control of chemical weathering shifted from supply factors to kinetic ones, such as temperature and precipitation. Our findings suggest that on the orbital time scale, glacial shelf exposure could enhance chemical weathering, thereby reducing atmospheric CO 2 ; on the millennium-centennial time scale, chemical weathering could rapidly respond to abrupt climate events. [ABSTRACT FROM AUTHOR]

To better understand the depositional constraints on the sulfate reduction process, we present a set of sulfur isotope data for hand-picked pyrites (δ34S pyr) from the coarse fraction (63–250 μm) of bulk sediments, coupled with the contents of carbonate, total organic carbon (TOC) and nitrogen (TN), as well as δ13C values of the TOC, from sediments of core EC2005 on the inner shelf of the East China Sea (ECS) since 16.4 ka. Our results show that core sediments were deposited in a terrestrial environment before 13.1 ka (stage I) when pyrite rarely occurred. During stages II (13.1–12.3 ka) and III (12.3–12.1 ka) seawater began to influence the core location, forming a tidal flat environment where abundant pyrites are well preserved. Then the inner shelf of the ECS was fully flooded, and two intervals with high (stage IV:12.1–6.0 ka; stage VI: 5.2–1.5 ka) and low sedimentation rate (stage V: 6.0–5.2; stage VII: 1.5 ka-present) are identified respectively. When compared with previous δ34S values of chromium-reducible sulfur (δ34S CRS) derived from the bulk sediments, δ34S pyr values are usually higher, indicating the macroscopic pyrites form in the later stages of sedimentary diagenesis when ongoing sulfate reduction has distilled porewater sulfate to a high degree. Considering the wide occurrence of biogenic shallow gas (dominated by CH 4) in these sediments, sulfate-driven anaerobic oxidation of methane (SO 4 -AOM) and organoclastic sulfate reduction (OSR) are expected to be two competitive pathways for sulfate reduction. We propose that the changes in sedimentation rate controls the pace of migration of the sulfate methane transition zone (SMTZ). When sedimentation rate is low, the SMTZ may be fixed in a certain depth (e.g., sediments deposited in stage III and V), where H 2 S is produced by SO 4 -AOM. In contrast, when sedimentation rate is very high (> 1 cm/yr), the SMTZ would be deep, and H 2 S is mostly produced by OSR. Further, our results imply that sulfur diagenesis in recent (since 1.5 ka) ECS mud sediments might be influenced by physical reworking (e.g., typhoon) and/or biological activity (bioturbation), resulting in partial reoxidation of pyrite crystals in fluid mud. Our findings therefore demonstrate that pyrite sulfur isotope compositions (bulk δ34S CRS & hand-picked δ34S pyr) are sensitive to local environmental evolution and the combined use of these two indicators can provide new insights into pathway of sulfate reduction in unsteady environments. • Constructing the depositional evolution of the East China Sea since16.4 ka. • Extreme pyrite sulfur isotopic fluctuation regulated by sedimentation rate. • Sulfur isotope of coarse pyrite is heavier than that of bulk sediments (CRS). • Sulfate reduction (OSR vs. AOM) is controlled by the pace of SMTZ migration. [ABSTRACT FROM AUTHOR]

Abstract 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 (δ34S py) derived from 60-m drilled core sediments deposited on the inner shelf of the East China Sea since 16.5 ka. The resulting δ34S py 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 δ34S py 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 δ34S py values become significantly correlated with sedimentation rates (SRs; r = 0.78, p < 0.01), which were controlled by the intensity of coastal currents in response to the East Asian winter monsoon. Specifically, pyrite sulfur is markedly depleted in 34S during the intervals with low SRs (δ34S py < −30‰) relative to that observed during the intervals with high SRs (δ34S py > 0‰), suggesting that SRs exert controls on δ34S py 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. [ABSTRACT FROM AUTHOR]

Sedimentary pyrite and the ratio between organic carbon and pyrite sulfur (C/S ratio) have been widely used as paleosalinity indicators to distinguish between marine and freshwater environments. However, in unsteady marine environments with strong physical reworking, the formation of pyrite is limited, leading to a high C/S ratio, as is the case in freshwater environments; thus, whether C/S ratios can identify unsteady marine environments in sedimentary strata is still a controversial topic. To calculate the availability of these classic indicators in unsteady environments, we analysed multiple indicators of core sediments obtained from the inner shelf of the East China Sea. Our results show that there are no pyrite aggregates in the sediments deposited under terrestrial conditions before 13.1 ka. During this period, the C/S ratios are higher than 2.8, representing the characteristics of sediment deposited in freshwater environments, which is also supported by low Sr/Ba ratios. When the core site was initially affected by seawater intrusion at approximately 13.1 ka, pyrite aggregates appeared for the first time, accompanied by a rapid decrease in C/S ratios, indicating a brackish tidal flat environment. We find that the C/S ratio overlaps between tidal flat and inner shelf environments, but the relatively high content of pyrite aggregates and fine-grained sediments in the shelf sediments can effectively separate these two environments. Our results further reveal that the mud depocentre initially developed at approximately 7.5 ka when the sea level reached its highstand. These new findings suggest that geochemical indicators should always be used in conjunction with sedimentary and paleoecological evidence to prevent biased conclusions. • Revisiting the depositional evolution history of the East China Sea inner shelf. • C/S ratios and formed pyrites indicate the timing of initial marine transgression. • Abundant sedimentary pyrites in sediments indicate sea-level highstand at 7.5 ka. • C/S ratio should be carefully used with other sedimentary and ecological parameters. [ABSTRACT FROM AUTHOR]

Abstract: X-ray diffraction (XRD) mineralogical and grain-size analyses indicate that inner continental shelf sediments in the East China Sea (ECS) represent a unique mixing of clays derived from the Yangtze River and silts/sands from small western Taiwanese rivers. Taiwanese (e.g., Choshui) clays (<2μm) display no smectite but the best illite crystallinity and are only distributed along southeastern Taiwan Strait. Both Yangtze and Taiwanese river clays are illite-dominated, but the poor illite crystallinity and the presence of smectite and kaolinite indicate that Taiwan Strait clays are mainly Yangtze-dominated. In contrast, medium silts (20–35μm) and very fine sands (63–90μm) in the Taiwan Strait are characterized by low feldspar/quartz, low K-feldspar/plagioclase and high kaolinite/quartz, indicating their provenance from Taiwanese rivers. Taiwanese silts and sands are introduced primarily by the way of typhoon-derived floods and transported northward by the Taiwan Warm Current during summer–fall months. Yangtze clays, in contrast, are widely dispersed southward about 1000km to the western Taiwan Strait, transported by the China Coastal Current during winter–spring months. Since most Taiwan Strait samples were collected in May 2006, clay results in this paper might only represent the winter–spring pattern of the dispersal of Yangtze sediments. [Copyright &y& Elsevier]

Carbon and sulfur preserved in estuary and shelf sediments play a critical role in controlling sediment diagenesis related to the global biogeochemical cycle. Their ratio (C/S = 2.8) in mud sediments has been widely used to distinguish freshwater from marine environments; however, this ratio can be influenced by depositional evolution, physical reworking, and other sedimentological parameters. We present a new C/S ratio data set from surface sediments of five rivers (Aojiang, Feiyunjiang, Jiaojiang, Oujiang, and Qiantangjiang Rivers), as well as core sediments offshore of the Oujiang Estuary (core EC2005, 60 m), to discuss how the evolution of the depositional environment influenced carbon and sulfur preservation since the last deglaciation. To this aim, we measured the contents of total organic carbon (TOC), total sulfur (TS), and carbonate in the collected samples. Our results demonstrate that a C/S ratio of 2.8 can effectively separate freshwater environments (river sediments and core sediments deposited before 13.1 ka), suggesting the initial impact of sulfate-enriched seawater on carbon and sulfur perseveration at ~13.1 ka. However, the TS content is independent of the TOC content after 13.1 ka, implying that pyrite sulfur is derived not only from organoclastic sulfate reduction (OSR) but also from sulfate-driven anaerobic oxidation of methane (AOM) under anoxic diagenetic conditions. In the shallowest core section (shallower than 5 m; < 1.5 ka), the C/S ratios gradually increase from 1 to 2.8, which corresponds to an interval with sulfide reoxidation under suboxic conditions caused by strong physical reworking. When the sediment is buried to a certain depth (deeper than 5 m; > 1.5 ka), a high sedimentation rate is conducive to an AOM reaction, resulting in the generation of a large amount of pyrite and finally causing the minimum value of the C/S ratio to be approximately 1. However, during the transitional period of 13.1–11.0 ka, sediments deposited in the tidal environment show overlap with those deposited in the marine shelf environment, and C/S ratios decrease from >10 to ~1. In addition, we propose that C/S and C/N ratios could be combined to reveal the depositional evolution from terrestrial to marine environments, which is sensitive to sea level and climatic changes. Therefore, our new findings suggest that the sedimentation process can modulate the diagenetic path of mud sediments (e.g., OSR versus AOM), and geochemical indicators of environmental evolution should be carefully used in combination with sedimentological parameters in shallow depositional environments. • We present a set of C/S data record from the East China See inner shelf since 16 ka. • C/S ratios could effectively distinguish between marine and freshwater environments. • The sedimentary process could affect the diagenetic process of authigenic pyrite. • C/S and C/N ratios could indicate the evolution of sedimentary environment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Quaternary East Asian summer rainfall evolution reconstructed with the Chinese speleothem δ18O records shows the consistency throughout the region of East Asia, and has long been considered equivalent to the monsoon intensity. Its variation and teleconnection with global climate were usually interpreted by the meridional shift of the intertropical convergence zone (ITCZ). However, many other proxy records, climate simulations and meteorological observations suggest the inconsistent rainfall patterns in the different regions of East Asia on multi-timescales. Such spatial heterogeneity in Quaternary East Asian summer rainfall indicates that the hydroclimate in this region is not fully paced by the migration of the ITCZ. Here, we report a sediment record of rainfall evolution during the last 400 ka in the northern East China Sea, and this record, in combination with a transient climate model simulation, indicates an out-of-phase relationship between rainfall over middle-southeastern East Asia and northern and southwestern East Asia on the precession band, with high boreal summer insolation corresponding to the increased rainfall intensity in the northern and southwestern East Asia, however, decreased rainfall intensity in the middle East Asia. We attribute this regional heterogeneity in East Asian rainfall to the reorganization of the Hadley circulation, including shifts in the ascending branch (ITCZ) and descending branch (subtropical westerly jet), in response to changes in the hemispheric meridional temperature gradient. Our results highlight the crucial role of the Hadley circulation in the East Asian hydroclimate and have important implications for future climate projections. • East Asian rainfall evolution was reconstructed from the sediment flux from the southern Japanese islands. • Heterogeneous phase of rainfall change in East Asia different regions on precession band has been found. • The spatial heterogeneity in East Asian rainfall was paced by the Hadley circulation reorganization. [ABSTRACT FROM AUTHOR]

A high-resolution fire history in the Yangtze River Basin over the past 7.0 ka BP is reconstructed based on the proxy of black carbon of sediment core ECMZ on the continental shelf of the East China Sea in order to reveal the interactions among fire, climate, vegetation and human activity on a regional scale. A comparison of fire activity with climatic and vegetation proxies suggests that changes in fire activity prior to 3.0 ka BP on both millennial- and centennial-timescales were closely related to variations in temperature and precipitation, with more fire during warm and humid periods, suggesting climatic control on regional fire activities. In contrast, the significant decoupling between fire and climate on multi-timescales since ∼3.0 ka BP implies increasing anthropogenic impact on regional fire activity. There is also a distinct response of fire activity to human disturbance at different time scales. Long-term reduction in regional fire activity since ∼3.0 ka BP was caused by a general decrease in forest cover with increasing human activity while short-term (centennial-timescale) enhancement in biomass burning usually coincides with periods characterized by increasing human activity associated with population migration or technological advances. • We reconstruct a regional fire history in the Yangtze River Basin since 7 ka. • Human impact changed the link of fire and climate in Yangtze Basin since 3 ka. • Human activity can suppress (promote) fire on millennial (centennial) timescale. [ABSTRACT FROM AUTHOR]