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Abstract 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) < 0.01, n = 95), the mode of sea-level rise differs before, during, and after the YD stadial. A rapid sea-level rise of 30.5 ± 4.9 mm/yr (r = −0.79, p(a) < 0.05, n = 25) occurred during 14.0–12.85 kyr BP. Subsequently, the rate of sea-level rise decreased significantly in response to the YD stadial, and it increased smoothly to 12.0 ± 1.4 mm/yr (r = −0.86, p(a) < 0.01, n = 29) from 11.65–10.0 kyr BP, indicating that MWP-1B was absent on the ECS shelf. Furthermore, based on comparisons of these data with other high-resolution curves of sea level or elevation at different latitudes, we suggest that the poleward seawater migration from intertropical broad oceans occurred because glacial isostatic adjustment could have generated a relatively consistent global sea-level height during the last deglaciation, especially during the YD, when the rate of sea-level rise was slowed. Highlights • Sea-level rise is constrained by East China Sea intertidal sediments. • A possible rapid sea-level rise occurred during 13.6–13.0 kyr BP. • Sea-level rise slowed remarkably in response to the Younger Dryas. • Meltwater Pulse 1B is not recorded on the East China Sea shelf. • The poleward migration of seawater can lead to global sea levels remaining the same. [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]

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. [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]

Abstract: Major and trace elements, loss on ignition (LOI), and grain-size distributions were determined on 190 surface sediment samples collected from the continental shelf, slope and the north Okinawa Trough in the East China Sea, at water depths of 100–200, 200–600 and more than 600m respectively. The sediments are composed mainly of sand and silt, generally low clay contents (average 10.5%), increasing over the range of 0.12–53.6% from the shelf and slope to the trough. Sediments were sandier on the continental shelf, particularly in the northern shelf sector. Spatial distributions in chemical compositions show that the contents of SiO2, CaO, Sr, and LOI values were relatively high on the sandy continental shelf. By contrast, the contents of Al2O3, MgO, Na2O, MnO, FeO, TiO2, Cu, Zn, Co, Ni and Cr were relatively high in the trough and along the central western shelf margin, where the sediments were composed mainly of silt. Fe2O3, P2O5 and Zr enrichment was highest in the slope sediments. Three factors were extracted by means of an R-mode factor analysis of chemical composition. Factor 1 has two inversely correlated elemental assemblages: (1) SiO2, K2O, TiO2, Al2O3 and Zr, which can be associated with terrigenous debris input and show high positive factor scores in the southern sector of the shelf; and (2) CaO, Sr, and LOI, which can be related with biogenic debris enrichment and show high negative factor scores in the northern shelf sector as well as in a more restricted area along the slope. CaO, SiO2, K2O and Sr represent the element assemblage of the shelf. Factor 2 comprises Na2O, FeO, Al2O3, TiO2, Cu, Zn and Ni, and shows high scores in the trough sediments. Na2O, Cu, Zn and Ni represent the elemental assemblage of the Okinawa Trough, and can be associated with volcanic matter. Factor 3 comprises Fe2O3, MgO, Cr and Co, with high factor scores on the slope and along the central western shelf margin of the study area, due to upwelling-induced enrichments in nutrients and biogenic shells. Fe2O3 and MgO are the slope elements. Based on the results of the distribution of the chemical compositions and the elemental assemblage of the surface sediment in the source-to-sink system, the influence of the Yellow River on the continental shelf is stronger than that of the Yangtze River. From the continental shelf and slope to the trough, the influence of the Yellow River decreased. From north to south in the Okinawa Trough, the sediment from the Yellow River decreases and from the Yangtze River increases, and the chemical compositions changed. [Copyright &y& Elsevier]

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]

Abstract: The Kuroshio Current (KC) has strong effects on local paleoclimate fluctuations and the paleoenvironmental evolution of the East China Sea (ECS). In the Okinawa Trough, the changes in the spatial position of its long axis and/or current strength since the last glacial stage have been a controversial topic. A multi-proxy study, including both magnetic and non-magnetic (grain-size measurements and AMS 14C dating) approaches, has been carried out on samples from core Y179 (2.53 m long) recovered from the central Okinawa Trough to investigate the possible KC-related Holocene paleoenvironmental changes in the trough. The core spans about the last 12,000 years and comprises dominantly clayey silt and silt. Magnetic measurements indicate that pseudo-single domain (PSD) magnetite of terrigenous origin is the main magnetic carriers with no apparent alteration due to early diagenesis. Based on physical properties, the core can be divided into three zones: I (0–1.05 m, <7.0 cal kyr BP), II (1.05–1.10 m, between 7.0 and 7.2 cal kyr BP) and III (1.10–2.53 m, >7.2 cal kyr BP). Compared with zone III, zone I contains less abundant but coarser magnetite particles and shows notable differences in magnetic and non-magnetic mineral components. Zone II shows transitional features between zones I and III in terms of magnetic properties. Constrained by 14C ages, zone II coincides with the middle-Holocene paleoenvironmental event in the Okinawa Trough (∼7.3–7.0 cal kyr BP) which was either previously identified to be associated with the re-entering of the KC into the trough after its shifting away during the Last Glacial Maximum (LGM) or interpreted as the KC strengthening at the same time. The down-core variations of magnetic properties in core Y179 agree well with the environmental changes caused by the middle-Holocene KC-related event in the Okinawa Trough. Therefore, our new results provide environmental magnetic evidence for the middle-Holocene event in the trough. [Copyright &y& Elsevier]