East China Sea Continental Shelf Research Articles

First report of plastic and non-plastic microparticles in stomach of slandertail lanternshark and shortspine spurdog from the edge of East China Sea

This study investigates the presence of plastic and non-plastic microparticles in the gastrointestinal tracts of two deep-sea sharks, Etmopterus molleri (n = 118) and Squalus mitsukurii (n = 6), bycatch from the East China Sea continental shelf. We found a total of 117 microparticles, predominantly fibres (67.52 %), with blue (31.62 %) and black (23.94 %) being the most prevalent colours. E. molleri contained 70 microparticles (0.63 ± 0.93 items/shark), 61.42 % non-plastics like viscose and cotton, while plastics included polyethylene, polyethylene terephthalate, and acrylic. Despite S. mitsukurii's limited sample size, the results show that it takes in a lot of microparticles (47 microparticles, 7.83 ± 2.64 items/shark), 57.44 % non-plastics (viscose, cotton, and ethyl cellulose), and 42.56 % plastics. A positive correlation between microparticle presence and total length was observed for E. molleri. These results provide initial data on microparticle ingestion by these species, highlighting potential ecological risks and trophic transfer implications in deep-sea ecosystems.

Eocene to Miocene sediment provenance features and evolution history of the western slope area in the Xihu Sag of the East China Sea Continental Shelf Basin

Rift basins are commonly characterised by multiple sediment sources (e.g. transverse and longitudinal) that change over time during different rifting evolution stages. Therefore, tracing sediment provenance to decipher the sedimentary source-to-sink analyses processes in rift basins is important to predict sandy reservoirs. The Xihu Sag in the East China Sea Shelf Basin, particularly its western slope, features large-scale sand bodies of unclear origin. We used petrography, heavy minerals and geochemistry to study sediment provenance in the Eocene Baoshi to Miocene Longjing formations. Our work suggests there are three distinct areas (namely zones A, B and C) affected by different source areas. Zone A, influenced by the Hupijiao uplift, primarily contains metamorphic rock minerals; Zone B, affected by the Haijiao and Hupijiao uplifts, contains igneous and metamorphic rock minerals; and Zone C, dominated by the Haijiao uplift, features igneous with some metamorphic sources, which increase over time, indicating stronger sediment input from the northern Hupijiao uplift. Rare earth element analysis suggests a continental margin and island arc setting, primarily with intermediate–acid felsic rock sources. However, a Eu negative anomaly in Eocene upper Pinghu Formation to the Miocene Longjing Formation indicates some basic source contributions, possibly from a volcanic belt east of the South Yellow Sea. This intermediate–basic volcanic rock belt is located to the northwest of the Hupijiao uplift and may provide clasts for zones A and B through axial channels. These findings indicate that varied sediment sources in the different zones and basin evolution stages with a growing extra-basinal contribution from the Eocene to Miocene, which align with the tectonic shift from the rifting to post-rift period, are essential for understanding the sedimentary filling in this area.

Geochemical controls on the distribution and bioavailability of heavy metals in sediments from Yangtze River to the East China Sea: Assessed by sequential extraction versus diffusive gradients in thin-films (DGT) technique

This study conducted a comprehensive investigation on the distribution and bioavailability of heavy metals (Cr, Co, Ni, Cu, Zn, Cd and Pb) in sediments along two typical transects from Yangtze River to the East China Sea continental shelf that spanning large physicochemical gradients. Heavy metals were mainly associated with the fine-grained sediments (enriched with organic matter), exhibiting decreasing trends from nearshore to offshore sites. The turbidity maximum zone showed the highest metal concentrations, which evaluated as polluted for some tested metals (especially Cd) using the geo-accumulation index. Based on the modified BCR procedure, the non-residual fractions of Cu, Zn and Pb were higher within the turbidity maximum zone, and significantly negatively correlated with bottom water salinity. The DGT-labile metals all positively correlated with the acid-soluble metal fraction (especially for Cd, Zn and Cr), and negatively correlated with salinity (except Co). Therefore, our results suggest salinity as the key factor controlling metal bioavailability, which could further modulate metal diffusive fluxes at the sediment-water interface. Considering that DGT probes could readily capture the bioavailable metal fractions, and reflect the impacts of salinity, we suggest DGT technique can be used as a robust predictor for metal bioavailability and mobility in estuary sediments.

Distribution and off–shelf transport of dissolved manganese in the East China Sea

To gain a better understanding of the geochemical behavior of dissolved manganese (Mn) in the marginal seas with respect to distribution and exchange fluxes, more than 200 water samples were collected in the East China Sea (ECS) in May, August, and October of 2013. The concentration of dissolved Mn in the ECS ranged from 1.1 to 81.5 nM, with a gradual decrease with distance from the shore. Seasonal distribution of dissolved Mn varies significantly in the Changjiang estuary, mainly regulated by freshwater input from the Changjiang (Yangtze River) and redox variations. The ECS continental shelf is an important source of Mn for adjacent waters, and the export of Mn–rich coastal waters had an important effect on its re-distribution and internal cycling. The dynamic variation fluxes of water and dissolved Mn across the 100– and 200–m isobaths in the ECS were calculated with an aid of the Finite−Volume Coastal Ocean Model (FVCOM). The ECS continental shelf exported (5.69 ± 1.14) × 108 mol/yr of Mn into the East/Japan Sea from the Tsushima Strait. The Kuroshio surface waters receive an additional (1.02 ± 3.12) × 108 mol/yr of Mn from the ECS continental shelf through a cross–shelf exchange process, which could potentially affect dissolved Mn in the Northwest Pacific. Our data suggest that off-shelf transport from the ECS continental shelf is essential for understanding the biogeochemical cycles of trace metals in the Northwest Pacific Ocean and the East/Japan Sea.

Transport of trace metals and their bioaccumulation in zooplankton from Changjiang (Yangtze River) to the East China Sea

The present study conducted a comprehensive field investigation on the transport and bioaccumulation of six trace metals (Cr, Cd, Pb, Mn, Ni, Cu) along a transect from Changjiang (Yangtze River) to the East China Sea continental shelf, which exhibited large variations in physiochemical properties (salinity, turbidity, pH, chlorophyll a, total nitrogen, dissolved oxygen, dissolved and particulate organic matter). From riverine sites to marine sites, dissolved Cr and Cd significantly increased, dissolved Pb and Mn showed less variations, while dissolved Cu and Ni showed complex spatial distribution patterns. Particulate trace metals (for Cr, Mn, Ni and Cu) were significantly negatively correlated with salinity. As a result, partition coefficients of trace metals (except Pb) were all significantly negatively correlated with salinity, indicating high salinity facilitated desorption/dissolution of metals from particulate phase. Additionally, the Changjiang derived particulate Pb, Mn, Ni and Cu sharply decreased (particularly for Mn) at the downstream of turbidity maximum zone, suggesting the efficient trapping of metals within this region. We further investigated the site-specific bioaccumulation of trace metals in size-fractionated zooplankton. Metal contents in macro-zooplankton were lower than micro- and meso-zooplankton owing to size-dependent zooplankton communities, while site-specific metal bioaccumulation mainly driven by site-specific zooplankton communities and salinity. The bioaccumulation factors of metals (Cr, Cd, Ni and Cu) were significantly negatively correlated with salinity, indicating high salinity hampered metal uptake which might attribute to competition of cations and formation of less bioavailable inorganic complexes with anions. Overall, high salinity generated two-sided effects (elevated dissolved metal concentrations Vs. reduced metal bioaccumulation) on metal contents in zooplankton (especially for Cr, Cd, Ni, and Cu), resulting in metal- and site-specific metal contents. We noticed relatively higher metal contents in zooplankton at hypoxia sites which could further transfer to predators in the East China Sea, and the underlying mechanisms still require future investigation.

The 14 December 2021 Mw 4.9 Offshore Jeju Island, Korea, Earthquake: Seismological Observation of an Intraplate Earthquake Provides Insight into Regional Seismotectonics

AbstractThe Mw 4.9 Offshore Jeju Island, Korea, earthquake of 14 December 2021 is the most significant event that occurred close to the young intraplate volcano on the continental shelf south of the Korean Peninsula. About 185 small earthquakes occurred during nine days following the mainshock. We accurately located 39 events despite limited station azimuthal coverage. We found that the mainshock ruptured along a ∼1.4 km long fault striking east–west (275°) and triggered two distinct clusters in the north–northeast direction. The mainshock is pure strike-slip faulting on the vertical plane. Its horizontal P axis strikes 50°, which differs substantially from the average trend of ∼70° for earthquakes in the southern Korean Peninsula. However, it is consistent with the P-axes orientation of shallow earthquakes in the offshore western Kyushu and along Okinawa trough. The 2021 Offshore Jeju Island earthquake may be the first significant earthquake in southern Korea–East China Sea continental shelf to date, whose causative fault is well constrained by accurate aftershock locations and detailed space–time analysis of the earthquake sequence. This earthquake may represent intraplate deformation in response to the tectonic evolution of the Philippine Sea plate, which is manifested through volcanic activities.

Distribution and chemical speciation of iron on the outer edge of the Changjiang diluted water plume of the East China Sea

In this study, we investigated the distribution of dissolved iron (DFe) and organic iron-binding ligands (LFe) in the area of contact between the Changjiang diluted water (CDW) plume and the branch of the Kuroshio Current during the early summer. Our objective was to evaluate how the interaction of these water masses affects the iron chemistry in this region. The upper 20 m of the stations on the northwestern sides was characterized by water of relatively low salinity (<33), which was influenced by the CDW. The northward branch of the Kuroshio Current likely flowed below this low-salinity water, at approximately 30–40 m. On the East China Sea continental shelf, low-oxygen water developed in the bottom water and advected horizontally towards the shelf slope on the isopycnic surface. The surface water, influenced by the CDW, contained relatively high concentrations of DFe and humic-like substances of riverine origin. However, the concentration of LFe in this water mass was not significantly different from that in the surrounding water masses. In low-oxygen water, the DFe concentration was high, and the concentration of humic-like substances was lower than that in the water from the upper layers. In addition to the LFe found in the oxygenated water, LFe with weaker affinities for ferric ions were also detected in this low-oxygen water, and the total concentration of LFe (>2 nM) was significantly higher than that in the other water masses. These results suggest that LFe released through biological decomposition of organic matter is more important for iron complexation in this area than humic-like substances. Therefore, it is essential to quantify diapycnal mixing with deep water on the continental shelf and shelf edge to evaluate the Kuroshio branch as a transporter of iron and LFe to the Sea of Japan.

An Objective Method with a Continuity Constraint for Improving Surface Velocity Estimates from the Geostationary Ocean Color Imager

Mapping surface currents with high spatiotemporal resolution over a wide coverage is crucial for understanding ocean dynamics and associated biogeochemical processes. The most widely used algorithm for estimating surface velocities from sequential satellite observations is the maximum cross-correlation (MCC) method. However, many unrealistic vectors still exist, despite the utilization of various filtering techniques. In this study, an objective method has been developed through the combination of MCC and multivariate optimum interpolation (MOI) analysis under a continuity constraint. The MCC method, with and without MOI, is applied to sequences of simulated sea surface temperature (SST) fields with a 1/48° spatial resolution over the East China Sea continental shelf. Integration of MOI into MCC reduces the average absolute differences between the model’s ‘actual’ velocity and the SST-derived velocity by 19% in relative magnitude and 22% in direction, respectively. Application of the proposed method to Geostationary Ocean Color Imager (GOCI) satellite observations produces good agreement between derived surface velocities and the Oregon State University (OSU) regional tidal model outputs. Our results demonstrate that the incorporation of MOI into MCC can provide a significant improvement in the reliability and accuracy of satellite-derived velocity fields.

Impact of Typhoon Talim on surface sediment records on the East China Sea continental shelf

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.

Monsoon‐Facilitated Off‐Shelf Transport of Dissolved Aluminum Across the East China Sea During Summer

AbstractThe continental shelf pump is believed to be important in transporting terrestrial materials across the East China Sea (ECS). More than 300 water samples collected from the ECS and a numerical model were used to identify the cross‐shelf exchanges of dissolved aluminum (Al) in the ECS in summer. The results indicated that dissolved Al concentrations ranged from &lt;1.0 to 242 nM, with the highest concentrations observed in the Zhe‐Min coastal waters, while the lowest concentrations were determined to be in Kuroshio deep waters. The Kuroshio surface waters receive additional dissolved Al from the ECS continental shelf through a cross‐shelf exchange process. By using dissolved Al as a tracer, evidence was found about the cross‐shelf transport of Al in the ECS. Cross‐shelf transport of dissolved Al was associated with fluctuations in the Taiwan Strait Warm Water, and the driving mechanisms were analyzed using a momentum equation. Ekman transport promoted by the summer monsoon was the key physical mechanism controlling the off‐shelf transport of dissolved Al. Quantitative calculations showed that the ECS was a net source of dissolved Al to adjacent waters, of which almost 65% of the output entered the East/Japan Sea, while the remaining 35% entered the Kuroshio currents. Our results highlight the importance of cross‐shelf transport processes to the distribution and cycling of biogenic elements within the marginal seas of China, and highlight the wider implications for biogeochemical cycles throughout the western Pacific Ocean.

Mineralogical and geochemical characteristics and ore-forming mechanism of hydrothermal sediments in the middle and southern Okinawa Trough

In this study, analysis of mineralogy and geochemistry of fifteen surface sediment samples from four hydrothermal fields in the middle and southern Okinawa Trough is presented. Sediment samples can be divided into two types: (1) Metalliferous group (MS group) containing large amounts of sulfides and sulfate are enriched in Pb, Zn, Cu, Fe, Au, Ag, Ba, As, Hg, Se, Sb, Mo, slightly enriched in U, V, and have rare earth elements (REE) patterns similar to those of hydrothermal vent fluids and sulfides, indicating formation by a complex combination of wasting and erosion primary massive sulfide deposits and plume fallout of sulfides and sulfate. The occurrence of sphalerite with high contents of Fe and of co-existing pyrrhotite as major Fe-sulfide indicate that these minerals are formed at high temperature with low-sulfur fugacity in the Clam and Jade hydrothermal sites. The enrichment of Pb, Zn, Cu, Au, Ag, Ba, As, Hg, Se, Sb, and Mo is related to the presence of galena, sphalerite, Cu-sulfides, stibnite, and realgar in the sediments. (2) Non-metalliferous group (non-MS group) containing small amounts of pyrite are slightly enriched in Pb, Zn, Cu, Au, Ag, As, Hg, Se, Sb, and Mo relative to the East China Sea (ECS) continental shelf sediments, with REE exhibiting a “shale-like flat” patterns and close to Taiwan sediments in a REE discrimination plot, indicating formation by a large amount of terrigenous materials originated from Taiwan Island and a small amount of particles of sulfides in the hydrothermal nonbuoyant plume. The slight enrichment of Pb, Zn, Cu, Au, Ag, As, Hg, Se, Sb, and Mo maybe caused by co-precipitation with the fine-grained sulfides settling from the nonbuoyant plume. The positive relationships between the HREE fractionation index (Gd/Yb)N, heavy mineral proportion, and δEu suggest that (Gd/Yb)N can be used as a sensitive indicator for reflecting the effect of hydrothermal activity on the sediments.

Abnormal reverse intrusion of the Kuroshio Branch Current induced by super typhoon soudelor

The Kuroshio Current has a considerable impact on the environmental characteristics and dynamic of the East China Sea (ECS). On the ECS continental shelf within the study area of (124°E-126°E, 25°N-27°N), the Kuroshio Branch Current (KBC) exists in a stable state and flows towards the main Kuroshio axis. The significant difference in potential vorticity is on both sides of the Kuroshio main axis, which makes it difficult for the seawater on the right side of the Kuroshio main axis to intrude the ECS continental shelf. Based on Argo data, satellite data and reanalysis data, an abnormal reverse intrusion of the KBC was observed during the passage of super typhoon Soudelor in 2015. The mean reverse volume transport during the period of Soudelor reached about 0.56 Sv, and the daily mean volume transport on August 9 reached up to 1.29 Sv. Soudelor inputted additional positive potential vorticity fluxes on the right side of the Kuroshio main axis and counteracted the significant potential vorticity difference on both sides of the Kuroshio main axis, which provided a channel for the apparently reverse enhanced ocean current. The significant Ekman downwelling and changes of the upper ocean stratification also promoted the reverse intrusion of KBC. This study offers new insights into the influence of typhoons on the intrusion of the Kuroshio onto the ECS continental shelf.

Variability of the nutrient stream near Kuroshio's origin

The Kuroshio—literally “the Black Stream”—is the most substantial current in the Pacific Ocean. It was called the Black Stream because this oligotrophic current is so nutrient-poor in its euphotic zone that the water appears black without the influence of phytoplankton and the associated, often colored dissolved organic matter. Yet, below the euphotic layer, nutrient concentrations increase with depth while current speed declines. Consequently, a core of maximum nutrient flux, the so-called nutrient stream, develops at a depth of roughly between 200 and 800 m. This poorly studied nutrient stream transports nutrients to and supports high productivity and fisheries on the East China Sea continental shelf; it also transports nutrients to and promotes increased productivity and fisheries in the Kuroshio Extension and the subarctic Pacific Ocean. Three modes of the Kuroshio nutrient stream are detected off SE Taiwan for the first time: one has a single-core; one has two cores that are apparently separated by the ridge at 120.6–122° E, and one has two cores that are separated by a southward flow above the ridge. More importantly, northward nutrient transports seem to have been increasing since 2015 as a result of a 30% increase in subsurface water transport, which began in 2013. Such a nutrient stream supports the Kuroshio's high productivity, such as on the East China Sea continental shelf and in the Kuroshio Extension SE of Japan.

Kuroshio fractions in the southwestern sea of Japan; implications from radium isotopes

To understand complicated current systems, we examined the 228Ra activities and 228Ra/226Ra activity ratios in 290 surface waters in the southwestern Sea of Japan from 2015 to 2020. The 228Ra/226Ra ratios exhibited large seasonal variation, showing higher ratios in July–September (1.5–2.5) than in other months. The fractions of the Kuroshio Current from the Pacific Ocean (fK), based on the 228Ra activities and salinity, in the western part of the study area were lowest in July after the steep decrease in the fK from May to July (0.95–0.6). This is due to the water mixing ratio of the East China Sea continental shelf side waters to the Kuroshio Current, reflecting the seasonal change and local water circulations.

Earth's surface responses during geodynamic evolution: Numerical insight from the southern East China Sea Continental Shelf Basin, West Pacific

The interaction between the Earth's surface and deep geodynamic processes has a great influence on sedimentary patterns and characteristics of sedimentary systems, especially in the continental margin, such as the southern part of the East China Sea Continental Shelf Basin (ECSCSB). However, the exact processes and dynamics are poorly understood. The numerical tool (Badlands) was adopted to simulate the geological evolution of the southern ECSCSB during the Mesozoic transitional regime of the West Pacific continental margin, between 200 and 100 Ma. The numerical model involving four-dimensional (4D) sequence stratigraphy was validated by comparing with the tectono-morphology, sedimentary environments and sediment distribution. According to our findings, the transition was mainly controlled by three structural stages. The first transitional stage of the southern ECSCSB was mainly controlled by lithospheric-scale tectonic evolution. In the second stage, the dynamic topography contributed to slow regional uplift, while the last stage showed mantle-induced dynamic subsidence. The model results on 4D geomorphic characteristics, sediment distribution of basin evolution and deep dynamic topography, provided a quantitative image for geological evolution of the West Pacific continental margin in the Mesozoic.

Parametric Subharmonic Instability of the Semidiurnal Internal Tides at the East China Sea Shelf Slope

AbstractOn the basis of measurements from an observing mooring system, the observational evidence of parametric subharmonic instability (PSI) that transfers energy from semidiurnal internal tides (ITs) to the subharmonic waves at the East China Sea continental shelf slope is presented for the first time. Although the mooring station is very close to the energetic semidiurnal IT generation site, about 76% of the observed shear variance is contained in the near-inertial band, which is found to have comparable upward- and downward-propagating energy components. Bispectra and bicoherence estimates further confirm the occurrence of PSI transferring energy from the low-mode M2 ITs (vertical wavelength of ~1000 m) to high-mode subharmonic waves (vertical wavelength of ~200 m). The calculated energy transfer rate reveals an averaged net value of ~5 × 10−9 W kg−1. Strong temporal variation of is found that is not exactly in phase with the semidiurnal energy flux. After looking into the local vorticity fields, it is strongly suggested that the varying background relative vorticity associated with the evolving Kuroshio has modified the efficiency of PSI at the mooring location through changing the local effective inertial frequency.

A new perspective for the sediment provenance evolution of the middle Okinawa Trough since the last deglaciation based on integrated methods

The sediment in the Okinawa Trough (OT) preserves considerable information regarding land–ocean interactions and palaeoenvironmental evolution in the East Asian marginal seas. More specifically, the sediment provenance in the OT must be studied to recover this information. However, arguments about this remain, especially regarding the contribution of Yellow River (YR)-derived materials to middle OT depositions. To resolve this problem, we systematically investigated a gravity core (M063-05; 3.87 m in length, since the last deglaciation) collected from the middle OT by integrating environmental magnetism, diffuse reflectance spectroscopy, and transmission electron microscopy, as well as analyses of sediment grain size, clay mineralogy, and major elements. Our results indicated that sediment from the YR has contributed dominantly to this core since the last deglaciation. Limited contributions were also made from the Yangtze River and Taiwan rivers during the Holocene. Terrigenous inputs derived from the YR could be well characterized by the ratio of hematite/(hematite + goethite). Additionally, the Kuroshio Current (KC) activity since the last deglaciation, which is an important influencing factor for sediment provenance changes, was well deciphered using a new proxy RelDM (relative contribution of detrital ferrimagnetic minerals to bulk magnetic properties). Based on comprehensive analyses of our results and previously published studies, we hypothesised that, during the last deglaciation, abundant resuspended sediment from the palaeo-YR mouth was transported to the East China Sea (ECS) continental shelf edge and the northern OT through seaward bottom flow and further spread into the middle OT. Since the Middle to Late Holocene, the central mud area of the South Yellow Sea and the mud area southwest off Cheju Island may have become the main sources to provide YR-derived materials to the middle OT. However, the mud-area-derived sediment could only be restricted to a small range owing to the hindrance of the strengthened KC. This study provides a new perspective for sediment provenance evolution of the middle OT since the last deglaciation and proposes new methods and parameters for future research on palaeoenvironmental evolution in the ECS.

Seasonal variations in the surficial sediment grain size in the East China Sea continental shelf and their implications for terrigenous sediment transport

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.

New progress on the onshore-offshore seismic survey in East China Continental Margin

The East China Continental Margin (ECCM) is an exemplified natural laboratory not only for studying the origin and evolution of trench-arc-basin system, but also for investigating the deformation mechanism within continent and its margins. For a better understanding on the structure and evolution of the ECCM, a NW–SE trending onshore-offshore seismic profile was recently carried out there using controlled source wide-angle and passive broadband seismic experiments in combination. This 1050-km-long seismic profile transects the East China Sea Continental Shelf Basin (CSB), Zhemin Volcanic Belt, Lower Yangtze Block, and southern North China Craton from East China Sea to continental East China. Preliminary results, such as crustal reflected and refracted phases and P-wave receiver functions, show a good quality of the seismic data and tentatively delineate some first-order characteristics of the crustal structure of the ECCM. Expectably, more detailed crustal seismic velocity and geometric structures along the profile can be constructed by a further processing of the seismic data, and enable continuous and detailed comparisons of the crustal structure and inherent nature among different blocks, combined with other existing seismic profiles in the study region. And these further studies will provide reliable constraints on some controversial geologic issues, such as the origin of CSB, the contacting boundaries and collisional processes among Cathaysian Block, Yangtze and North China cratons.

Sedimentary responses to the cross-shelf transport of terrigenous material on the East China Sea continental shelf

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.