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The principle of the common heritage of mankind (CHM principle), as enshrined in Part XI of the United Nations Convention on the Law of the Sea, is the fundamental principle of sharing the resources of the international seabed area. The International Seabed Authority (the Authority) is the international institution that implements Part XI of the Convention and has the dual task of managing the exploration and exploitation of resources in the international seabed area and protecting the marine environment. This article dives into a deep analysis of the problems that have arisen in the course of the development of the sharing mechanism for resources in the international seabed area by the Authority, and further engages in the discussion on China's domestic legislative strategies for the mechanism for sharing of resources in the international seabed area. It is argued in this article that China's domestic deep-sea legal regime is an important part of global deep-sea governance, and has the potential to apply a 'corrective' function to the 'institutional misalignment' that occurs in the operation of the international seabed regime with the aim of promoting the sharing of resources in the international seabed area. [ABSTRACT FROM AUTHOR]

Existing seawalls along the eastern coast of China are increasingly becoming the focus of upgrade operations. Concerns arise regarding the settling and stability of seawalls built on soft clayey seabed during upgrade operations. Pore water pressure (PWP) and horizontal displacement accumulations induced by combined tide and wave loadings are observed in in-situ measurements of the clayey seabed underneath the seawall. The measurement results show clear correlations between the oscillations of excess PWP and variations in the tidal height. To reproduce the quasi-static interaction behaviors of the gravity-type seawall and clayey seabed under combined cyclic loadings from waves and currents, a finite element model has been built after incorporating a stiffness degradation law that is evaluated from laboratory triaxial tests on the seabed soil. Demonstrably, with a suitable stiffness degradation law for the seabed soil, the accumulative behaviors can be reasonably reproduced using finite-element modeling. [ABSTRACT FROM AUTHOR]

It has long been established that plastic flow in the asthenosphere interacts constantly with the overlying lithosphere and plays a pivotal role in controlling the occurrence of geohazards such as earthquakes and volcanic eruptions. Unfortunately, accurately characterizing the direction and lateral extents of the mantle flow field is notoriously difficult, especially in oceanic areas where deployment of ocean bottom seismometers (OBSs) is expensive and thus rare. In this study, by applying shear wave splitting analyses to a dataset recorded by an OBS array that we deployed between mid-2019 and mid-2020 in the South China Sea (SCS), we show that the dominant mantle flow field has a NNW–SSE orientation, which can be attributed to mantle flow extruded from the Tibetan Plateau by the ongoing Indian–Eurasian collision. In addition, the results suggest that E–W oriented flow fields observed in South China and the Indochina Peninsula do not extend to the central SCS. [ABSTRACT FROM AUTHOR]

Large-scale constructions of offshore wind power are carried out in southeast coast of China, where the seabed is covered in weathered granite. However, the bearing capacity and failure mechanism of monopile foundation in weathered-granite seabed are rarely researched. In this paper, the stress-strain characteristics and strength parameters of granite with different weathering degrees were obtained through laboratory tests, and the pre-strain test method was used to study mechanical parameter variation of moderately weathered granite in the crushing process. Experiment found that the strength parameters decrease mainly after the strain reaching 50% of the ultimate strain of moderately weathered granite. In addition, the bearing capacity and failure mode of rock-socketed monopile under unidirectional horizontal loading was investigated numerically. Analysis showed that the failure mode of rock-socketed monopile under unidirectional horizontal loading is progressive and presents two obvious failure zones. More critical, the existence of vertical loading effectively improves the horizontal bearing capacity of monopile foundation in the weathered rock seabed, and the failure envelope of the monopile foundation in H-V loading space is elliptic-shaped. This provides further understanding of the mechanical properties of submarine weathered granite, and the helpful reference for stability evaluation of rock-socketed monopile foundation in weathered granite seabed. [ABSTRACT FROM AUTHOR]

Based on a substantial number of seabed sediment samples and corresponding acoustic characteristic and physical property test data collected in the continental shelf area of the northwestern South China Sea, this study employed a sound speed ratio correction model to analyze the correlation between the sound speed ratio of seabed sediments and parameters such as porosity, density, mean grain size, and water content. This study resulted in the development of both single-parameter and double-parameter empirical formulas for the sound speed ratio of seabed sediments in this marine region. The determination coefficients (r2) for the single-parameter empirical formulas based on physical properties, excluding the mean grain size (r2 ≤ 0.75), were all above 0.78, indicating a strong correlation. Additionally, the fitting curve at 100 kHz was slightly greater than that at 50 kHz, consistent with the acoustic dispersion characteristics of sediments. To assess the applicability of the empirical formulas to different maritime areas, the formulas derived from the South Yellow Sea, East China Sea, and South China Sea were compared with those of the study area. The results indicated that the empirical formulas for the sound speed ratio established in this study have general applicability, especially for sediments with low porosity, high density, and low mean grain size. In addition, the determination coefficient of the dual-parameter empirical formula for the sound speed ratio–porosity–mean grain size is superior to that of the single-parameter empirical formula for the sound speed ratio–mean grain size. Through comparative studies with other marine areas, it was found that there are certain differences in the relationships between porosity and mean grain size established in different marine areas. Therefore, based on the rough sphere model, this study transforms the GS model into a single-parameter model built on either porosity or mean grain size. The error analysis results indicate that the single-parameter GS model has a smaller error than the measured data. However, the GS model controlled by a single parameter performs poorly compared to the predicted curves of the sound speed ratio–porosity and the sound speed ratio–mean grain size fitted in this study. This discrepancy may be attributed to the fact that the input parameters of the GS model are reference values, emphasizing the need for further research to determine suitable input parameters for the GS model in this marine area. • The empirical equations for the sound speed ratio were developed in this study in different marine regions. • The established empirical equations for the study area were compared with those for the South Yellow Sea, East China Sea, and other marine regions. • This study compared the empirical equations with the grain shearing (GS) theoretical model. [ABSTRACT FROM AUTHOR]

The Tianshan in western China is rich in ore resources, but its tectonic uplift and exhumation history closely related to the resource exploration is still controversial. This study provides a new strategy to uncover the tectonic uplift processes in southern Tianshan by combining the morphological characteristics and thermochronological ages of detrital zircons in the Tarim Basin. The morphology of the Meso-Cenozoic detrital zircons in the Kuqa Foreland Basin, a secondary tectonic unit of the Tarim Basin, is dominated by three types of P, S, and G, and their average alkaline and temperature indexes are 668.0−677.2 and 347.6−413.5, respectively. Moreover, the U-Pb ages of these detrital zircons are primarily divided into two groups of 270−330 and 380−470 Ma. These features indicate that the Early Carboniferous-Early Permian and Middle Ordovician-Middle Devonian alkaline granites distributed in the South Tianshan and southern Central Tianshan were the main sources of the detrital zircons in the Kuqa Foreland Basin. The decomposition of the detrital zircon fission track ages further reveals that the provenances of the Kuqa Foreland Basin primarily consisted of the southern Central Tianshan, the eastern South Tianshan, and the central South Tianshan during Meso-Cenozoic. Among them, the eastern South Tianshan played a dominant role in the material supply. The synthesis of the decomposed zircon fission track (ZFT) ages and the lag-time evolution pattern indicated that the South Tianshan and the southern Central Tianshan mainly experienced five stages of tectonic uplifting that occurred in the Devonian, the Permian, the Middle Triassic-Middle Jurassic, the Cretaceous, and since the Miocene, respectively. They were related to the subduction of the South Tianshan Ocean northward to the bottom of the Central Tianshan, the compression and accretion after the closure of the South Tianshan Ocean, and a series of collisions between the Qiangtang-Lassa-India plates and the southern margin of the Eurasia plate in the Meso-Cenozoic, respectively. This study provides a new provenance analysis method, which was successfully applied in the Tianshan, and also develops a new way to study Central Asia's tectonic evolution. [ABSTRACT FROM AUTHOR]

The principal construction-area of offshore wind farm (OWF) in China has shifted from the soil-based seabed area to the weathered rock-based area. The current studies about construction materials of OWF mainly focus on the submarine soft-clay or sandy soil seabed, resulting in the design and construction of OWF in rock-based area cannot directly refer to the existing research conclusions and results recommended in standards. Therefore, this paper concentrates on the investigation of cyclic behavior of submarine completely weathered granite of offshore wind farms in rock-based sea area under cyclic loadings. The experiments analyze the cyclic stress-strain and stress path behavior, revealing two unique development modes under different dynamic loadings, i.e., the stable development mode and the destructive development mode. A unified forecasting model of pore water pressure with different development modes is established, and further research investigates insight critical failure stage by concentrating on pore water pressure. More critical, the unique mechanical properties and microscopic characteristics of completely weathered granite are clearly expounded by comparing with submarine soft clay and sandy soil. This gives the engineering suggestion of design value of OWT foundation in completely weathered granite seabed, and is a helpful reference for the construction of OWF in rock-based sea area. • Two unique development modes of completely weathered granite under different dynamic loading are put forward. • A new discrimination method of critical failure stage is proposed based on development of pore water pressure under different cyclic loading. • The unique mechanical properties and microscopic characteristics of submarine completely weathered granite are clearly revealed by comparing with submarine soft clay and sandy soil. [ABSTRACT FROM AUTHOR]

Foraminifera are important components of tropical marine benthic ecosystems and their recovery pattern from the end-Permian mass extinction can yield insights into the Mesozoic history of this group. Here we report the calcareous and agglutinated foraminifera recovered from five measured stratigraphic sections on the Great Bank of Guizhou, an uppermost Permian to Upper Triassic isolated carbonate platform in the Nanpanjiang Basin, south China. The material contains >100 Triassic species, including three that are newly described (Arenovidalina weii n. sp., Meandrospira? enosi n. sp., and Spinoendotebanella lehrmanni n. gen., n. sp.), ranging from Griesbachian (Induan) to Cordevolian (Carnian) age. The species belong to the classes Miliolata, Textulariata, Fusulinata, Nodosariata, and to an unknown class housing all aragonitic forms of the orders Involutinida and Robertinida. Based on previously established conodont zones and carbon isotope chemostratigraphy, the Griesbachian (early Induan) through Illyrian (late Anisian) interval has been subdivided into 12 foraminiferal zones and two unnamed intervals devoid of foraminifera. Following the extinction at the Permian-Triassic boundary, habitable ecological niches of Griesbachian age were invaded by disaster taxa that subsequently became extinct during the Dienerian (late Induan) and left no younger descendants. The disaster taxa were replaced by Lazarus taxa with Permian origins, which were then decimated by the Smithian-Spathian (mid-Olenekian) boundary crisis. The tempo of recovery appears to have been modulated by environmental changes during the Griesbachian through Smithian that involved both climate change and expansion of anoxic ocean bottom waters. Uninterrupted and lasting recovery of benthic foraminifera did not begin until the Spathian. UUID: http://zoobank.org/2a6e9061-b163-402a-9098-8765a80576b3 [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) finite difference (FD) model with formal fourth-order accuracy has been developed for the ocean acoustic Helmholtz equation (HE), which can be used to address arbitrary bathymetry and provide more accurate benchmark solutions for other 3D underwater acoustic approximate models. The derivatives in the acoustic HE are numerically discretized based on regular grids, and the perfectly matched layer is introduced to absorb unphysical reflections from the boundaries where Sommerfeld radiation conditions are deployed. The system of linear equations is solved using a parallel matrix-free geometric multigrid preconditioned biconjugate gradient stabilized iteration method, and the code (named COACH) is run on the Tianhe-2 supercomputer in China. Four 3D topographic benchmark acoustic cases—a wedge waveguide, Gaussian canyon, conical seamount, and corrugated seabed—are simulated to test the present FD model, and the maximum number of grid points reaches 33.15 × 109 in the wedge waveguide case, running in parallel with 988 central processing unit cores. Furthermore, the accuracy and generality of the present model have been verified by solution comparisons with other available 3D acoustic propagation models, and the two-dimensional and 3D transmission loss contours are presented to facilitate the distinguishing among the acoustic field features of these cases. [ABSTRACT FROM AUTHOR]

Both India and China are 'Pioneer investor' nations for Deep Seabed Mining (DSM). Both these nations commenced their exploration quest of the deep seabed at nearly the same time and today are one of the few nations persisting with DSM. These notwithstanding, the developments made by China in this comparative period are many magnitudes more than that made by India. While India has limited its research to the Indian Ocean Region (IOR), China has gone global to win five exploration contracts from the International Seabed Authority (ISA). China is also rated as the first country that would commence exploitation once the exploitation rules are promulgated by the ISA. In going global, China has the exploration rights in the Indian Ocean for polymetallic sulphides with efforts to acquire some more Area in this oceanic space. While China grows technologically in the field of DSM and deploys its assets in the IOR, it is adding to the already skewed threat perception thereby becoming a matter of security concern for India. It is with this understanding that the article aims to look at the developments made and the involvement of China in the IOR for DSM and their resultant security implications for India. [ABSTRACT FROM AUTHOR]

Li, M.; Li, W.; Xie, M., and Xu, T., 2021. Morphodynamic responses to the Hong Kong–Zhuhai–Macao Bridge in the Pearl River estuary, China. Journal of Coastal Research, 37(1), 168–178. Coconut Creek (Florida), ISSN 0749-0208. Human activities such as constructing large bridges, performing land reclamation, and creating harbors in complex tidal estuaries can result in severe and undesirable morphodynamic responses. This study investigates morphodynamic responses to the construction of the Hong Kong–Zhuhai–Macao Bridge (HZMB) in Lingdingyang Bay of the Pearl River estuary (LBPRE). The LBPRE in China is an important estuary with unique geomorphic features, complex hydrodynamic sediment conditions, dense shipping routes, high ship density, and a high navigation grade. The HZMB, a major sea-crossing transportation project consisting of bridges, a tunnel, and man-made islands, is being designed to cross the LBPRE. The morphodynamic responses resulting from the HZMB are likely to be significant. Therefore, it is necessary to carry out studies to optimize the HZMB design to minimize its impacts on hydrodynamics, sediment environment, harbors, and navigational channels as much as possible. In this article, the natural hydrodynamic and sediment conditions are first analyzed on the basis of in situ data. Next, a numerical model of tidal current, sediment movement, and seabed deformation based on TK-2D software is set up with an irregular triangular grid. The model is calibrated with in situ data, and the results show that the calculated tidal levels, tidal currents, suspended load concentrations, and seabed deformations are all in good agreement with field data. The model is then applied to carry out high-resolution simulations for design optimization of the HZMB from the perspective of its impacts on morphodynamics and hydrodynamics, as well as on harbors and channels. The study shows that the proposed HZMB design is feasible in terms of the morphodynamic responses. The conclusions provide an important foundation for the construction of the HZMB project. [ABSTRACT FROM AUTHOR]

Aiming at the problems of high risk, high investment, low quality and low benefit in offshore geotechnical engineering survey, we have carried out a series of key technology innovation and research of exploration platform in order enhance the international competitiveness of China's waterway engineering survey technology. This paper focuses on the modularization, integration, safety, multi-purpose, recycling and other aspects of exploration platform series design innovation, and introduces the design innovation of offshore engineering survey ship borne "dynamic" platform, seabed type "static" platform and " dynamic static" double platform. The results have been used in a series of domestic and foreign engineering survey sampling and in-situ testing projects from intertidal to offshore waters, which solves the problems of high cost and low quality of offshore exploration, and reduces the factors affecting the exploration by sea conditions. [ABSTRACT FROM AUTHOR]

Net enclosure aquaculture is a newly developed eco-friendly marine aquaculture method and has been applied extensively in China because of the advantages of large water body, wide space for fish activities, closer to nature culture environment and closer to wild culture objects. Pile-type and floating-rope-type are two main construction types of enclosure engineering, and the pile-type is more preferable owing to its higher performance in withstanding harsh ocean environment. The pile-type aquaculture engineering consists of net panel system and pile system configured in mono or multi rows. In practice, the overturn and breakage of the piles have occurred and lead to the escape of cultured fishes, resulting in great economic loss. In order to solve these problems and improve the stability and safety of piles, the mechanical characteristics of piles in marine dynamic environment were analyzed in this study, and the pile-type aquaculture site located at Taohua island, Zhoushan was chosen as the study case. The subgrade reaction method, representing the soil surrounding of the pile by a series of discrete horizontal springs was adopted to investigate the effects of water depth, current velocity, wave height and combined action of wave and current, together with the embedded depth on the dynamic response of piles. The results showed that the maximum displacement was found at the top of the pile and increased with the increase of current velocity, wave height and water depth, and decreased with the increase of embedded depth. The positive and negative bending moment in the sides of the vertical line of zero bending moment increased first and then decreased along the pile, showing a shape of symmetrical S. The maximum bending moment was found about 2 m underneath the sea bed and exhibited a similar dynamic tendency to that of the maximum lateral deflection. As for the case of pure current, the piles kept stable and safety at the current velocity of 0.8, 1.0, 1.2 and 1.5 m/s. However, it could be damaged when the wave height exceeded 5 m or in the combined action of wave height of 3.0 m and current velocity of 1.0 m/s. For the engineering case in this study, the embedded depth should be larger than 17 m when the wave height of 5 m was considered as the lateral loading. In addition, a ratio of the length above the sea bed surface and embedded in the sea bed of the pile not more than 0.8 was advisable. Filed observation of the piles lateral deflection and stress force should be monitored in a long period so as to improve the analytical method specially used for net enclosure engineering. The results can provide guidance for the net enclosure design and construction. [ABSTRACT FROM AUTHOR]

Two new free-living marine nematode species of the genus Antomicron Cobb, 1920 belonging to the family Leptolaimidae are described from the seabed sediment of Jiaozhou Bay of the Yellow Sea. Antomicron holovachovi sp. nov. is characterised by loop-shaped amphideal fovea; male with five straight tubular and 41 alveolar supplements; short cephalic setae; slightly curved slender spicule with cephalated proximal end and tapered distal end; and rectangular gubernaculum with a short dorsal caudal apophysis. Antomicron chinensis sp. nov. is particularly characterised by loop-shaped amphideal fovea; male with only alveolar supplements, without tubular supplement; slender and slightly inverted S-shaped spicule with cephalated proximal end and tapered distal end; and rectangular gubernaculum with a slender dorsal caudal apophysis. An updated identification key to species of the genus Antomicron is also provided. [ABSTRACT FROM AUTHOR]

In this study, shear wave speed and related physical properties were measured for 21 seafloor sediment cores collected in the northern South China Sea. Results reveal that the shear wave speed in this study area ranges between 15.57 and 75.55 m/s and demonstrates a pattern of regional distribution. The sediment in the continental shelf area shows characteristics of high shear wave speed, high wet bulk density, low porosity, and large grain size. Contrarily, the sediment in the continental slope area exhibits characteristics of low shear wave speed, low wet bulk density, high porosity, and fine particles. Accordingly, the correlation between shear wave speed and physical properties such as porosity, wet bulk density, water content, and average grain size was studied. Prediction formulas of shear wave speed of sediments in this study area containing single and double physical parameters were established via regression analysis. The comparison between single‐parameter and double‐parameter prediction formulas indicates that the determined coefficient of the double‐parameter prediction formulas based on porosity and average grain size is higher than that of single‐parameter prediction formulas. It indicates that the double‐parameter prediction formulas based on porosity and average grain size have better prediction performance. Moreover, the prediction formulas established in this study were further compared with those of other study areas, and their differences were analyzed accordingly. Plain Language Summary: The shear wave speed of seafloor sediments is the velocity of shear wave propagating in seafloor sediments. Shear wave speed is one of the critical acoustic properties of seabed sediments, which is very useful in many fields such as exploration and exploitation of seabed resources, precise prediction of the acoustic field, and prediction of stability with regard to engineering geology. In view of the importance of shear wave speed, the correlation between shear wave speed and physical properties such as porosity, wet bulk density, water content, and average grain size were analyzed, and the prediction formulas of shear wave speed were established in this study. Key Points: Shear wave speed and physical properties of sediments in the continental shelf were compared with those in the continental slopePrediction formulas of shear wave speed based on porosity, density, water content, average grain size were establishedThe prediction formulas established in this study were compared with those of other study areas, and their differences were analyzed [ABSTRACT FROM AUTHOR]

Lingding Bay has two main huh ports and connected deep water waterways in South China. Maintaining the stable pattern of "three heaches and two troughs" is the key hasis for the Western trough deepwater waterways development in Cuangzhou Port. Since 2008, due to artificial sand digging on the middle beach, three huge sand pits with total volume of 7 × 108 m3 has been formed, which directly affects the evolution of the beach and trough in Lingding Bay. By means of field investigation and numerical simulation, the influence of sand mining on surrounding water body and topography is analyzed. It is pointed out that the sediment concentration in the sediment digging area can increase greatly from 0.2 kg/m3 to 1.5-2.8 kg/m3 (up to 5 kg/m3). This will increase the deposition of the nearby seabed and also affect the waters of the Hong Kong-Zhuhai-Maeao Bridge. The influence of hydrological factors on the formation of sand pits are calculated. The results show that the main changes of tide level, tidal current and tidal volume are in the sand pit and its adjacent waters. The main changes are the tidal level decreases (less than 1cm), the tidal current decreases, and sediment deposition is mainly in the sand pit (33 cm/a). The seabed around the pit is scoured, and the scour in the south side is larger. At present, sand pits are mainly silted up, and the time of silting back is expected to take 20 years. When 2#, 3# sand pits or 2#, 4# sand pits are connected, it is possible to form a new tidal current channel, change the existing pattern of "three beaches and two troughs", and have a negative impact on the existing channel maintenance and port production. [ABSTRACT FROM AUTHOR]

The Yurtus Formation is generally believed as one of the most potential hydrocarbon source rocks under the Cambrian gypsum-salt bed in the Tarim Basin of China. This formation exhibits unique geochemical characteristics during the Ediacaran-Cambrian transition period. In this study, we investigated the lower and upper black shales from the Yurtus Formation for the high-resolution geochemical analysis in order to further characterize the prevailing redox conditions and sedimentary mechanisms involved in the organic matter accumulation process. During the deposition of the lower black shale with high TOC in Unit2, the high concentrations of phosphorite and barite, and the REE geochemistry manifested a mixture of hydrothermal fluid and seawater. Through in-situ laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS), we explored the element distribution of the drill-core-preserved phosphate nodule, indicating that the phosphogenesis may be related to the involvement of bacteria activities under intermittently oxic bottom waters or consistently free oxygen conditions. Biomarker evidence by the identification of green sulfur bacteria demonstrated the occurrence of photic zone euxinia (PZE), and the trace metal patterns revealed intermittently bottom water oxygenation and stratified ocean which was consistent with the scenario of phosphate nodule formation. In contrast, the upper black shale with relatively low TOC was characterized by a detrital input, with significantly decreasing redox-sensitive trace mental enrichment (U EF , Mo EF , V EF) and positive excursion of carbon isotopes, as well as a positive relationship between ∑REE and Al. The present study provides more explicit insights into not only the sedimentary mechanism of the black shale, but also the evolution of the Earth system at the key interval of the early Cambrian. • The lower and upper black shales from the Yurtus Formation were deposited. • The high-resolution geochemical characteristics of the lower Cambrian black shales have been investigated. • The stratified ocean with bottom water oxygenation contribute to the high-TOC black shales deposition. [ABSTRACT FROM AUTHOR]

Abstract The analysis of innovations and technologies aimed at improving the sustainability of mining activity has become important in recent decades. The main objective of this article is to evaluate the dynamics of this line of research worldwide between 1998 and 2017. A bibliometric analysis and a systematic review of a sample of 2,562 articles was developed along with an analytical framework based on the mine life cycle and the three areas of sustainability (economic, social and environmental). The results show that sustainability research has grown at a much higher rate than that of mining and minerals research. The three journals that have published the most articles on this line of research are Journal of Cleaner Production, Environmental Science and Technology, and Gornyi Zhurnal , and the three countries with the highest number of published articles are the USA, China, and Germany. Some 60.9%, 30.9%, and 8.2% of the analysed mining innovations impact environmental, economic, and social sustainability, respectively, and some 7.1% affect the exploration phase, 84.8% the exploitation phase, and 8.1% the closure phase. The analysis of issues related to environmental sustainability becomes more relevant as the exploration phase moves on to exploitation and closure. The primary challenges and future lines of research are in reducing energy use and increasing the use of renewable sources, analysing the social sustainability of current mining activities, and achieving clean production in the development of new mining activity environments (ice-covered areas and the ocean floor). This work provides new perspectives on the analysis and integral assessment of innovations and technologies aimed at making mining activity more sustainable, particularly where the contributions to the environmental, economic, and social fields are valued. Graphical abstract Image 109 Higlights • Innovation and technology are key factors for mining sustainability. • A systematic review and bibliometric analysis have been performed on 2562 articles. • Mining expansion to icy and ocean soil presents challenges to cleaner production. • The pending subject of mining activity related to sustainability is social field. [ABSTRACT FROM AUTHOR]

ABSTRACT Ji, Z.Z.; You, Z.J.; Hou, Z.Q., and Wei, Y., 2018. Development of generalized model for estimation of sediment siltation in coastal waterways of China. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1221–1225. Coconut Creek (Florida), ISSN 0749-0208. Coastal sediment siltation has long been a major problem for design and construction of coastal large-scale ports in the world. Silty sediment siltation often occurs in coastal waterways of China especially during storm events, in which silty sediment is stirred up from the seabed and re-suspended into the water column by storm-induced waves, and transported into the waterways by currents in three forms of suspended load, bedload and sheet-flow load. This study is to derive a generalized model for estimation of sediment siltation rates under both non-storm and storm conditions based on 6-year field data collected in the outer navigation channel of Huanghua Harbor. The sediment siltation data were collected by directly measuring the seabed elevation changes along the port navigation channel from 2002 to 2007. In analyzing the field data collected, a semi-empirical model between effective wind energy and sediment siltation rate is also presented, and found that the newly derived model yields satisfactory agreement with the siltation data collected during the coastal storm events. [ABSTRACT FROM AUTHOR]

Reliable fossil record regarding symbiotic relationship is a key to understanding the ecology and environment in Cambrian. Herein, we exhibited an exceptionally well preserved hyolithid with intact stalked eocrinoids attaching on the operculum and conch venter, indicating the symbiotic relationship between hyolithids and eocrinoids. By that we carried out a reconstruction for their epibiotic relationship on the Cambrian sea floor. The ontogenetic features of two eocrinoids on the operculum indicated they were immature (in the early stage of ontogeny). And considering the correlation between the orientation of eocrinoids and the mud flow in event-induced rapid burial, we proposed the orientation of eocrinoids implies the direction of mud flow. Additionally, based on specimens with signs of transport, we found that taphonomical factors besides ecological factors could also lead eocrinoids to preferentially attach on the dorsal or dorso-lateral surface of the conch, which was usually interpreted as a mutualism in previous reports though. [Display omitted] [ABSTRACT FROM AUTHOR]

Seabed sediment classification has important applications in ocean engineering and submarine pipeline design. This paper proposed the dimension-invariant residual network to improve the seabed sediments classification accuracy. The dimension of each channel of the feature extracted from the dimension-invariant residual block is the same as the original image. Compared with down-sampling, each feature vector has more feature parameters, which can improve the accuracy of seabed sediments classification. Shortcut connections were introduced in the proposed network, which can make the network easier to optimize and achieve good performance by using only a not very deep network. It also has a lower complexity compared to powerful classifiers like Transformer and has a better performance in small-scale seabed sediment classification. And to improve the accuracy of seabed sediment classification without consuming too much time for training the classifier, the network parameters optimization method was proposed in this paper. Recording the classification accuracy and training time of the network with these different parameters. Determining the parameters of the network by the proposed optimization method. The proposed classification model and optimization method were validated by using the side-scan sonar images, acquired from the area around the Shandong Peninsula of China. The layers and convolutional kernel sizes were determined to be 8 and 3, respectively. The classification accuracy of overall, rock, sand, and mud of the dimension-invariant residual network model were 97.83%, 94.04%, 97.80%, and 98.02% respectively. In comparison with state-of-the-art classifiers, the experimental results demonstrated that the proposed classification model achieved better performance, and the network parameters optimization method enables the network to achieve satisfactory classification accuracy while spending less time. The proposed classification model and network parameters optimization method show great potential in seabed sediments classification, which can also be extended to the task of underwater target recognition in future research. • The dimension-invariant residual network identifies seabed sediments more accurately. • The dimension-invariant residual block can retain more features than the traditional. • Network parameter optimization methods can balance the training time and performance. [ABSTRACT FROM AUTHOR]

Kelp aquaculture activities occupy large nearshore areas with significant effects on sediment properties, primarily caused by the influence of the suspended kelp on local hydrodynamics. Changes in sediment composition and grain-size distributions were investigated prior to and following the commencement of kelp aquaculture activities in Heini Bay in eastern China. Seabed sediment types and the particulate matter in suspension during the kelp seeding and harvesting periods, and in sediment cores, were analyzed. While suspended sediment in the kelp aquaculture area was up to 20% organic material, sediment organic content on the seabed remained at similar levels as areas lacking aquaculture. The composition of the seabed sediment in the kelp aquaculture area became finer-grained by the capture of fine particles. Within the kelp aquaculture area, the sediments are poorly sorted and positively skewed, whereas at the shoreward and seaward of the aquaculture area the sediments are relatively coarse-grained, well-sorted and nearly symmetrically distributed. Therefore, the kelp aquaculture activities not only increase the fine particulate fraction in the sediments within the aquaculture area, but also result in similar deposits seaward of it, indicating that seabed erosion and accretion is also controlled by the sediment source and the hydrodynamic conditions. The analysis of sediment cores showed that kelp culturing refines the sediment by preferentially capturing particles in the 38–40 μm size class, while having no effect on the <32 μm fractions, as evidenced by the positive skew of the surficial sediments. The captured particle size class became well mixed into the sediment, thereby changing the composition of the sediment in the uppermost layer of the core, indicating the existence of continuous and stable hydrodynamic conditions within the kelp aquaculture area. The same effect was observed in the seabed sediments seaward of the aquaculture area. [ABSTRACT FROM AUTHOR]

Due to extraordinary natural geographical features, seabed topography, and sediment sources, wave-induced silt liquefaction is a common occurrence in the subaqueous delta of the Yellow River, China. When liquefaction occurs, the original sedimentary structure of silt is destroyed; after liquefaction, the sediment particles are rearranged and reconsolidated, resulting in distinct physical and mechanical differences between the liquefied material and the nearby adjacent strata that have not been subjected to liquefaction. Based on data from geotechnical testing (GT), scanning electron microscope (SEM) images, and sub-bottom profiling (SBP), the physical and acoustical characteristics of silt remoulded by wave-induced liquefaction (SRL) in the Yellow River subaqueous delta are determined. According to the GT results, liquefaction resulted in distinct decreases in the water content (2.6%), the void ratio (0.056), and the clay content (4.52%), as well as slight increases in the wet density (0.01 g/cm3), the dry density (0.05 g/cm3), and the grain size (d 50) (0.015 mm). Per our SEM analyses, the SRL material is denser than the unremoulded silt, attributed to the rearrangement and reconsolidation of the silt particles. As can be determined from the high-resolution SBP data, that acoustically, the SRL is distinctly different from the adjacent intact strata. The smooth funnel-shaped features demarcate the extent of the region that has been subjected to a specific liquefaction and silt reconsolidation event. Due to the presence of a fault-like uplifted reflection event in the underlying strata, the SRL produces positive sound velocity anomalies on the order of 53–127 m/s. Analyses of the physical and acoustical characteristics of the SRL provides valuable insight into the engineering properties of seabed silt. • Focusing on physical and acoustic properties of silt after being remoulded by wave-induced liquefaction. • Both the physical features from borehole and SEM images and the acoustical features from high-resolution SBP prove that the liquefaction and remoulding process significantly improves the engineering properties of the seabed silt. • The positive sound velocity anomalies are estimated to have magnitude of 53–127 m/s. [ABSTRACT FROM AUTHOR]

Globally variable ocean and atmospheric dynamics lead to spatially complex seasonal cycles in sea level. The China Seas, that is the Bohai, Yellow, East China and the South China seas, is a region with strong seasonal amplitudes, and straddles the transition between tropical and temperature zones, monsoonal and westerlies, shelf and deep ocean zones. Here we investigate the drivers for seasonal variability in sea level from tide gauge records, satellite altimetry along with output from the NEMO (Nucleus for European Modeling of the Ocean) model including sea surface height and ocean bottom pressure along with meteorological data in the China Seas. The seasonal cycle accounts for 37% - 94% of monthly sea level variability in 81 tide gauge records, ranging from 18 to 59 cm. We divided the seasonal cycles into four types: 1) an asymmetric sinusoid; 2) a clearly defined peak on a flat background; 3) a relatively flat signal; 4) a symmetric co-sinusoid. Type 1 is found in northern China and Taiwan, Korea, Japan and The Philippines where Inverse Barometer (IB) effects dominates seasonality along with a steric contribution. The seasonal monsoon associated with barotropic response and freshwater exchange play important roles in type 2, (eastern and southern Chinese coasts), type 3 (East Malaysia) and type 4 (Vietnam and Gulf of Thailand). IB corrected seasonal cycle amplitudes are larger in continental shelf areas than the deep ocean, with a maximum in the Gulf of Thailand, and NEMO underestimates the seasonal amplitude along the coast by nearly 50%. • Seasonal sea level in the China seas can be divided into 4 types according driving factor. • Inverse Barometer dominates in northern China, Taiwan, Korea, Japan & The Philippines. • Seasonal monsoon dominates southern China, East Malaysia, Vietnam & Gulf of Thailand. • NEMO sea surface height underestimates the annual amplitude by up to 12 cm. [ABSTRACT FROM AUTHOR]

This paper presents a fully coupled flow deformation model to characterize the nonlinear seismic site response of liquefiable marine sediments, considering the ocean wave environment. Emphasis is placed on extending a simplified soil hysteresis model for the effective stress analysis of nonlinear site seismic response. The proposed model addresses the limitations of existing one-dimensional (1D) hyperbolic soil models to simultaneously capture the 3D hysteretic stress–strain behavior and the accumulated volumetric deformation of soil skeleton. The volume strain formulation of soil skeleton is included in the Biot's volumetric compatibility equation as the source term for excess pore water pressure buildup. The proposed method is implemented into an explicit time matching finite difference analysis platform, and validated against the recordings of the KSRH10 site for North–South (NS) direction of KiK-net borehole arrays in Japan. Finally, the influences of ocean wave loading upon the seismic wave propagation behavior in liquefiable marine sediments are examined with reference to the Bohai Strait site condition, China. The obtained results indicate that the ocean wave environment has significant effect on the nonlinear seismic site response of liquefiable seabed at shallow depth. • A fully coupled flow deformation model is presented for the simulation of seabed liquefaction. • A simplified soil hysteresis model is extended for the fully coupled seismic site response analysis. • Model calibrations are carried out against the recordings of the KSRH10 site from the KiK-net. • Influences of ocean wave on the seismic response of liquefiable marine sediments are investigated. [ABSTRACT FROM AUTHOR]

Since the launch of China’s first altimetry and scatterometry satellite, Haiyang-2A (HY-2A), various validation studies of HY-2A radar altimetry using preliminary data products have been conducted. Here, we present the first comprehensive result assessing HY-2A’s altimeter data quality and the altimetry system performance using an improved HY-2A Geophysical Data Record (GDR) product (Institute of Geodesy and Geophysics reprocessed GDR product version A, GDR_IGGA). The main improvements include altimeter timing and waveform retracking, and tropospheric, ionospheric, and sea-state bias (SSB) corrections, which resulted in more accurate HY-2A sea surface height observations. Jason-2 altimeter observations are used for the cross calibration of the HY-2A altimeter over the oceans between ±60° latitude bounds, primarily due to the limitation of Jason-2 coverage. The statistical results from single- and dual-satellite altimeter crossover analysis demonstrated that HY-2A fulfills its mission requirements. We uncovered a mean relative bias of −0.21 cm (with respect to Jason-2), and a standard deviation of 6.98 cm from dual-satellite crossover analysis. In addition, we present the results of a detailed analysis on variance reduction studies for the various geophysical corrections from HY-2A and compared them with Jason-2. The wave-number spectra of HY-2A and Jason-2 sea-level anomalies show similar spectral content, verifying the performance of HY-2A altimetry to be similar to Jason-2. Open issues and the remaining HY-2A data problems have been identified, allowing prospective future studies for further improvement of its accuracy. [ABSTRACT FROM AUTHOR]

Seawalls play an important role in protecting coastal regions by resisting storm surge and waves. However, a seawall can cause seabed erosion at its foot by facilitating hydrodynamic scouring, but the effects of seabed scour on wave loads have not been sufficiently considered. This paper presents a case study of increased wave load on the Gudong seawall in the Huanghe delta, China, which has experienced serious erosion since its construction. Four commonly-used empirical formulas, which were also verified through our physical simulation experiments, were used to calculate the wave loads on the crown wall of the seawall based on observed wave conditions. The maximum allowable wave load on the seawall was also determined based on historical extreme sea conditions that caused severe damage to the seawall. Our calculations showed that, the wave load has increased at least two times since the seawall's construction due to seabed scour, and the present crown wall cannot resist large waves with a 5-year return period, much less than the 50-year return period it was designed to resist. This suggested that the reasonable design of seawalls needs to adequately consider seabed scour as well as the associated increase in of wave loads. • The seabed in front of the Gudong seawall experienced serious erosion since its construction. • The wave force on the seawall increased greatly due to seabed scouring in front of the seawall. • The seawall is now unable to withstand extreme waves with return period of 5-years. • It is necessary to consider increased wave load induced by deepening water depth in seawall design. [ABSTRACT FROM AUTHOR]

• The cohesive model was adopted to stimulate the off-bottom process. • The suction force and mat-soil interaction was investigated. • The negative pore pressure increases firstly and then dissipates when uplifting. • The effects of OCR, soil structural, clay depth and eccentricity are significant. A deep layer of soft clay is widely present on the seabed in the offshore area of China. The traditional jack-up spudcan faces the problem of difficult insertion and extraction in clay seabed. Jack-up mat foundation is more suitable in soft clay than spudcan for its lower requirements on bearing capacity. Due to the poor permeability of clay, the uplifting process of the mat foundation needs to overcome a large soil suction force. In this study, three-dimensional numerical model is established to investigate the suction force of jack-up mat foundation on marine clay seabed. The elastoplastic constitutive model, which can describe the structural and over-consolidation of soft marine clay seabed, was embedded in commercial software ABAQUS through UMAT subroutine. The cohesive contact model was adopted to stimulate the interaction between mat foundation and the seabed soil. Field test was conducted to verify the accuracy of the numerical model. Then, the effects of degree of over-consolidation, degree of structural, depth of clay, interface stiffness and eccentric uplift loading on suction force are studied in detail. Numerical results show that the effects of degree of over-consolidation and structural of soil have significant influence on the suction force. The suction force first increases rapidly and then decrease gradually as the thickness of the upper dimensionless clay layer increases. With the increase of the uplift eccentricity, the suction force reduces continuously. [ABSTRACT FROM AUTHOR]

The monocaisson foundation has become an important choice with the increasing demand of offshore wind turbines constructed in silt and sand seabeds in China. To guarantee the normal operation of the wind turbine, the angular rotation of the foundation should be strictly controlled. It is necessary to predict the bearing capacity of caisson foundations at an allowable angular rotation. Several series of model tests were carried out in sandy silt under 1g gravity on suction caissons with different sizes subjected to overturning loading. The test results revealed the effect of the diameter, aspect ratio, and loading eccentricity on normalized moment capacity of caissons. The instantaneous rotation centers of model caissons were simplified to be at the depth of about four-fifths of the skirt length, almost directly below the lid center. Apart from the available ultimate moment capacity prediction approaches, a new calculation approach of deflection-based bearing capacity was proposed based on the mechanisms of soil-structure interaction and deflection of the caisson. Furthermore, determination of the model parameters is discussed. The present analytical approach can predict the moment-rotation curves of the model tests in silt and of the field test in a sand well. This deflection-based approach makes it possible to calculate bearing capacity at any allowable angular rotation. Further studies show that soil pressures and friction on the outer skirt at the passive zone contribute most to the moment capacity of the caisson, specifically the aspect ratio and the horizontal subgrade reaction constant. Finally, design charts of monocaisson foundations in silt and sand for offshore wind turbines are given. [ABSTRACT FROM AUTHOR]

Yangshan Deep-water Port, the largest deep-water port in China, is located in the sea area of the Qiqu Archipelago adjacent to Hangzhou Bay. It goes deep into the ocean and far from the continent, and plays a key role in the economy and shipping of China. The evolution and stability of the seabed in the Yangshan Deep-water Port have potential influences on the security of port engineering. Based on GIS spatial analysis technology and MATLAB numerical analysis software, this study predicted the short-term evolution trend of the Yangshan Port frontier seabed terrain through the establishment of a modified power function model. The research included: (1) a systematic analysis of the characteristics of the terrain evolution before (1960-1997) and after (1998-2008) the construction of Yangshan Port by using terrain data from the study area; (2) based on the historical erosion and deposition characteristics of Yangshan Port, an improved power function model was established and the reliability of the model was validated to simulate the study area's frontier seabed evolution trend in 2015. The results show that: (1) before the construction of Yangshan Port, the seabed in the study area had a narrower variation in erosion and deposition, with the ratio of erosion and deposition of the stable region, erosion area and deposition area being 53.7 %, 18.3 % and 28.0 % respectively, overall the area showed a relatively stable erosion and deposition character; (2) after the construction of the port, the erosion and deposition variation ranges of the seabed were sharply amplified, obviously due to man-made interference being stronger than natural evolution. The stable region of erosion and deposition was only 22.7 %, erosion area was 53.8 %, and the deposition area was 23.4 %, which showed an erosion intensity that was larger than the deposition intensity; (3) the established improved power function model can be used in the short-term prediction of the Yangshan Port frontier seabed evolution trend with high prediction accuracy. The results can aid in decision making with regard to coastal protection and prospective construction schemes around Yangshan Port. [ABSTRACT FROM AUTHOR]

An inversion scheme based on time-warping is presented for estimating seabed sound attenuation from modal dispersion of close-range single-hydrophone data. The dispersion information is extracted directly from the warped signal spectrum. Seabed sound speed and density are inverted from the modal group velocity curves, and the attenuation is inverted from the normalized modal amplitudes. The method is applied to experimental data collected in the Yellow Sea of China during the winter of 2002. The inverted sound speed and density are consistent with the sand-silt-clay sediment at the site, and the attenuation is nonlinear over the frequency band from 125-500 Hz. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results of an experimental study in which the occurrence and evolution of inhomogeneity in the strength of a uniform-originated silty seabed were investigated. The pore pressure and penetration strength at different depths inside the seabed were observed during the experimental process under the weight of the soil and under the action of waves of different heights (H=5cm, 10cm, 15cm). We found that a well-mixed silty seabed consolidates under the stress of its own weight, and its strength gradually increases as a result. Small wave action consolidates and strengthens the seabed and sediment. When the seabed is exposed to progressively higher waves, a fluidised response characterised by an arc-shaped boundary surface occurs on the seabed, and this response further controls the occurrence and evolution of the strength inhomogeneity of a uniform-origin seabed. The analyses clearly illustrate that features of seabed erosion and mass-transportation activity previously ascribed to increasing wave-current bed shear stress are controlled primarily by the process of wave-induced inhomogeneity in the strength of seabed sediments originating in the preceding period. In addition, the implications of the mechanism are explored. [Copyright &y& Elsevier]

Abstract: Through a large-scale examination of the morpho-sedimentary features on sea floors in the Taiwan–Luzon convergent margin, we determined the main sediment dispersal system which stretches from 23°N to 20°N and displays as an aligned linear sediment pathway, consisting of the Penghu Canyon, the deep-sea Penghu Channel and northern Manila Trench. The seafloor of South China Sea north of 21°N are underlain by a triangle-shaped collision marine basin, resulting from oblique collision between the Luzon Arc and Chinese margin, and are mainly occupied by two juxtaposed slopes, the South China Sea and Kaoping Slopes, and a southward tilting basin axis located along the Penghu Canyon. Two major tributary canyons of the Formosa and Kaoping and small channels and gullies on both slopes join into the axial Penghu Canyon and form a dendritic canyon drainage system in this collision marine basin. The canyon drainage system is characteristic of lateral sediment supply from flank slopes and axial sediment transport down-canyon following the tilting basin axis. The significance of the collision marine basin in term of source to sink is that sediments derived from nearby orogen and continental margins are transported to and accumulated in the collision basin, serving as a temporary sediment sink and major marine transport route along the basin axis. The comparison of the Taiwan–South China Sea collision zone with the Papua New Guinea collision zone of the western Solomon Sea reveals remarkable similarities in tectonic settings and sedimentary processes that have resulted in similar sediment dispersal systems consisting of (1) a canyon drainage network mainly in the collision basin and (2) a longitudinal sediment transport system comprising a linear connection of submarine canyon, deep-sea channel and oceanic trench beyond the collision marine basin. [Copyright &y& Elsevier]

This study focuses on the stratigraphic sequences and the bounding surfaces in the upper Cambrian Series 3 to Furongian Gushan and Chaomidian formations in the Shandong region, China. The bounding surfaces are compared with those of the coeval succession in the Taebaek area, Korea. According to the vertical arrangement of the facies associations and the identification of the bounding surfaces, three stratigraphic sequences are recognized, representing dynamic changes in accommodation versus sedimentation. The bounding surfaces can be traced in the Shandong region for about 6,000 km in area, but cannot be correlated with those of the Taebaek area (eastern margin of the platform, about 1,000 km apart). Surface 1 is characterized by an abrupt facies change from carbonate to shale, representing a distinct drowning surface. The drowning surface is also diagnosed in the Taebaek area but highly diachronous. Surface 2 is a cryptic subaerial unconformity, reflected by an erosion surface, missing of a trilobite biozone ( Prochuangia Zone), and an abrupt increase in carbon isotope value. It is not identified in the Taebaek area where the Prochuangia Zone is present. Surface 3 is a marine flooding surface, indicated by a subtle transition from flat-bedded microbialite to domal microbialite (or grainstone). It may be correlated with that in the Taebaek area, which is, however, represented by an abrupt facies change from sandstone to limestone-shale alternation. The high variability of the sequence-bounding surfaces is indicative of variable regional factors such as topographic relief, carbonate production, siliciclastic input, and hydrodynamic conditions. It suggests that the sequence-bounding surfaces are invalid for a basin-scale correlation, especially in an epeiric carbonate platform. [ABSTRACT FROM AUTHOR]

The epidosites are interpreted to form in upflow zones at the base of ore-forming oceanic hydrothermal systems that vent as black smokers on the sea floor. This study presents new field, major and trace element, and oxygen isotope data for the recently discovered epidosites in the ca. 1.0 Ga Miaowan (庙湾) ophiolite located near the northern margin of the Yangtze craton. The epidosites occur mainly in the cores of strongly deformed, lensoidal amphibolites. Field observations, major and trace elements and oxygen isotopes suggest that the epidosites were formed by metasomatism of ocean floor basalts, diabase dykes, and gabbros during seafloor hydrothermal alteration. [ABSTRACT FROM AUTHOR]

Summary: Turbidity currents play a critical role in effective sediment and reservoir management in alluvial rivers. Yet previous estimations of reservoir turbidity currents are mostly based on simple empirical relations and it remains unclear how and to what extent physically based numerical models can resolve current evolution as compared against field observations. This paper presents a physically-based,process-resolved computational study of turbidity currents in the Xiaolangdi reservoir in the lower Yellow River, China. A coupled layer-averaged 2Dnumerical model is applied, which explicitly incorporates the interactions between the current, sediment transport and morphological evolution, and features a new well-balanced numerical scheme dealing with irregular topography. Two turbidity current events in July 2004 are numerically simulated to calibrate and validate the model. The current advance and the sediment transport rate computed by the model compare favourably with field measurements. These suggest the present model is a viable tool for determining the timing for operating the bottom outlets, which is critical for effective reservoir sediment management. The sediment entrainment flux and bed resistance are key factors dictating the evolution of turbidity current and warrant further investigations. [ABSTRACT FROM AUTHOR]

Abstract: Analysis of three-dimensional seismic data and multibeam data from the Pearl River Mouth Basin in the northern South China Sea, reveals numerous focused fluid flow features and associated widespread shallow gas from 500m to 2000m water depth. Shallow gas is usually indicated by acoustic anomalies, such as enhanced reflections, acoustic turbidity, and acoustic blanking. Two types of tectonically and stratigraphically controlled fluid flow related systems are identified. The first type can be observed in the deep strata, including gas chimneys, mud diapirs, mud volcanoes, pipes, and large normal faults, which are usually located over basement highs and are related to overpressure mainly caused by gas generation. The focused fluid flow structures serve as pathways for upward migration of thermogenic fluids from source rocks or gas reservoirs. The second type is a shallow fluid flow system consisting of minor normal faults, migrating canyons, mass transport deposits, contourite, and pockmarks. The minor faults and migrating canyons provide pathways for fluids of thermogenic origin transported by the deep fluid flow system and of biogenic origin generated in the shallow succession. The mass transport deposits and contourite mainly serve as caprock. Small-scale fluid seepage is observed at the modern seabed expressed as pockmarks located above shallow gas accumulations. The distribution of shallow gas is controlled by the combination of these two systems. The focused fluid flow features and shallow gas are poorly studied in the study area and we propose a 3D model of focused fluid flow and shallow gas distribution that can be used more widely in other passive and active continental margins. Our results are important to the understanding of resources (hydrocarbon and gas hydrate) exploration in such a petroliferous basin and they must be taken into account when assessing seabed stability. [Copyright &y& Elsevier]

Based on a data base of multi-channel seismic profiles covered over Dongsha plateau of the northern South China Sea margin, we found that the sea bed morphology of northern South China Sea margin had been changed dramatically after Dongsha uplifting, that sedimentary layer since Miocene age had been eroded with maximum eroded thickness more than 1000 m, and that an erosive channel had been formed of 20 km in width and 200 km in length and several hundreds meters in depth on the outer shelf of northern South China Sea. The erosive channel is parallel to the 600 m isobath line, stretching from northeast to the southwest north of Dongsha uplift. The Kuroshio intrudes the South China Sea through Luzon Strait both in winter time and summer time, and in the northern South China Sea margin area, the intruded Kuroshio Branch takes the form of Pacific-Indian Ocean Through Flow (PITH) in winter time, while the Luzon Strait Subsurface Inflow (LSSIF) in summer time, the routes of both PITH and LSSIF coincide well with the distribution of the erosive channel. After climbing from the northern slope up to the northern shelf, and after joined by the southward flow from the middle northern shelf of South China Sea, the Kuroshio Branch is strengthened and thus is able to erode the sea floor, and the shape of the erosive channel is a result of the long-term interaction between the Kuroshio South China Sea Branch and the Dongsha outer shelf sea floor. [ABSTRACT FROM AUTHOR]

High-resolution sampling of more than 10,000 microfossils from seven Late Permian-Middle Triassic paleoequatorial sections in south China refutes claims for a 5 m.y. recovery delay after the end-Permian mass extinction. We show that level-bottom seafloor diversity began to recover in the early Smithian, little more than 1 m.y. after the mass extinction, while recovery of reef-building metazoans began 4 m.y. later, in the Anisian. A further mass extinction in the late Smithian, identified in the pelagic fossil record, is weakly manifest as a temporary pause in diversification among benthic communities. In the Early Triassic of south China, the offshore diversity increase began before then, in shallower settings. The recovery from the end-Permian mass extinction in south China was therefore significantly more rapid and environmentally more complex than hitherto known. [ABSTRACT FROM AUTHOR]

Abstract: Core DGKS9602 (931cm in length) was retrieved from the Middle Okinawa Trough. The age model was correlated with the adjacent core, DGKS9603 (Li et al., 2001), for the upper part and to the standard SPECMAP chronology down to ~60ka BP using marine oxygen isotope control points. Pollen analysis was carried out, and seven pollen zones were identified. The results showed that the pollen spectra in MIS 3 were very different to MIS 2 but comparable with the Holocene. The saccate pollen, principally Pinus, predominated in most parts of the core, except for the interval of the Last Glacial Maximum (LGM) and the late MIS 3 when Artemisia and other herbs increased prominently. The ratios of P/A (Pinus/Artemisia) and of PB/NAP (pollen with bladders versus non-arboreal pollen) were used as a proxy for sea-level change and for estimating distances from the coastline to the study site. The provenance study, using a modern analog technique based on the East Asian Modern Pollen Database and fossil pollen assemblages, revealed that the pollen were derived from diverse source areas during different stages since ~60ka BP. The pollen zones equivalent to MIS 1 and 3 were characterized by uncertain and disparate areas of provenance, and the surrounding continents, including Eastern Mainland China, Korea and Southern Japan, possibly made equivalent contributions, which may be the result of enhanced pollen transport by the northwesterly wind. However, the LGM represented in core DGKS9602 was distinguished by restricted sources from the exposed East China shelf, where the vegetation was quite similar with the herb coverage in the present-day North China Plain. The pollen assemblages sensitively reflected the coastline changes, marked by transport patterns between fluvial runoff and northwesterly winds plus ocean currents. Some pollen changes and limits of pollen zones coincided with the timing of Heinrich events, implying that the rapid climate fluctuations during MIS 3 and MIS 2 may have partially resulted in the forest changes in Eastern Asia. The pattern of relative abundance of subtropical and total arboreal taxa is consistent with that of δ18O from Hulu Cave, implying monsoonal climatic control over vegetation change. The estimated temperature (MAT) by the means of pollen ratios for the LGM was 5–8°C lower than that in the Changjiang River mouth today. [Copyright &y& Elsevier]

Abstract: This study focuses on the unique occurrence of an extensive microbialite bed (10–20m thick) in the Chaomidian Formation (Furongian) in Shandong Province, China in order to understand its paleoenvironmental implications. The microbialite bed can be traced for over 6000km2 in area. The microbialites are characterized by centimeter- to decimeter-scale branching maze-like constituents (maceriae) of microbial and muddy sediments with chaotic texture, including tabular maceriate microbialite (type 1), columnar maceriate microbialite (type 2), and columnar chaotic microbialite (type 3). Within the bed, each microbialite unit is generally well correlated for tens of kilometers. The entire bed is bounded by limestone–marlstone alternation at the base, and an erosional surface at the top that is subsequently overlain by a grainstone bed of various thicknesses. The microbialite bed formed when the seafloor reached suitable water depth for the microbial growth during sea-level rise accompanied with carbonate production. The maze-like maceria structures formed to acquire a larger surface area under a relatively large input of lime mud. The tabular maceriate microbialites initially formed in relatively deep-water environments and flourished on broad and flat seafloor, whereas the columnar microbialites (types 2 and 3) developed under the influence of strong waves and currents. The microbialite bed was eroded and terminated by frequent storm events and buried under the reworked grainstone. Further rise in sea level and increased metazoan activities afterwards limited the resurgence of microbes in the late Furongian. [Copyright &y& Elsevier]

Abstract: Radioisotopes from dry and wet atmospheric deposition (i.e., 7Be, 210Pb and 137Cs) can be used to determine the sources, fluxes and rates of internal processes in sedimentary compartments such as rivers, estuaries and oceans. The activities of 7Be, excess 210Pb (210Pbex) and 137Cs in surface sediments collected in the Changjiang Estuary during May and June of 2007 were measured to elucidate the routes and budgets of these radionuclides and the sediment transport. The ranges of the activities of 7Be, 210Pbex and 137Cs were 0.0–34.6, 0.39–2.90 and 8.0–214.0Bqkg−1, with averages of 9.8, 1.56 and 43.5Bqkg−1, respectively. Based on the material balance of inputs (riverine loading, atmospheric deposition) and outputs (decay, burial into sea bed) of 7Be, 210Pb and 137Cs, the calculated results indicate that around 35% of both the 210Pbex and 7Be total inputs in the Changjiang Estuary should be exported out of this area. However, the evaluated results showed that 83% of the 137Cs total input into the Changjiang Estuary should be from offshore and/or the south. These phenomena can be explained by the current structure of the water mass around this region. Changjiang Dilute Water (CDW), with sediment, is first moved to the south and northeast. Then, the Zhejiang–Fujian Coast Current (ZFCC), with sediment, can travel farther south. Moreover, the Jiangsu Coast Current (JCC), with sediment from the Yellow Sea, can approach the Changjiang Estuary. However, both the Taiwan Warm Current/upwelling and the ZFCC can carry fine sediment with 137Cs to the Changjiang Estuary. [ABSTRACT FROM AUTHOR]

Abstract: This study was conducted to examine the spatial variations in the exchange between near-bottom suspended and sea-bottom sediments in the Yangtze Estuary and adjacent region, as well as to explore the fate of suspended sediments in the study area. The relationship between the sand, silt, and clay contents of the sediments was analyzed by log-ratio analysis, which revealed a non-linear function for selective deposition and a wide range of grain-size distributions in the estuary. This finding does not conform to the nearly constant clay/silt ratios reported for other tidal basins around the world, due to non-linear sediment mixing under complex hydrodynamic conditions. The sediment exchange processes in the Yangtze Estuary were quantified based on the principle of mass balance. The average grain-size distribution of near-bottom suspended sediments from the estuary showed that approximately 49% of the riverine sediments accumulated in the mouth bar area, while the rest, which is primarily composed of fine-grained sediments, is transferred to the outer estuary and deposited in the form of flocs. The spatial distribution of the sediment exchange ratios demonstrated that small amounts of suspended sediment were deposited onto the seabed of the upper estuary (exchange ratio<0.1), because the fine-grained suspended sediments in this region were transported to the mouth bar area by the ebb-dominated tidal flow. The sediment exchange ratios in the outer estuary also showed very low values (<0.1) due to the oceanic currents offshore that prevented the diffusion of riverine sediments further seaward. Intensive sediment exchange occurred in the inner estuary due to the sand-mud mixing which was controlled by bidirectional tidal flows. In addition, a high sediment exchange ratio occurred in the muddy area (>0.8) seaward of the river mouth, which implies that this is the present-day depocenter of Yangtze mud. The sediment exchange rates obtained by combining the dimensionless exchange ratios and bulk sediment accumulation rates, were found to be 2–3cm/yr in the muddy depocenter, which extends to the south of the river mouth (from 122° E to 123° E longitude, at 31° N latitude). [Copyright &y& Elsevier]

Following the eruption of Mount Pinatubo on 15 June 1991, volcanic ash was transported westward to the South China Sea in an atmospheric plume, falling out and settling to the sea floor within days and forming an up to 10 cm thick layer on an area >400 000 km2. Immediately after deposition, surviving deep-burrowing animals re-opened their connection to the sea floor to obtain water for respiration and/or food take-up. Later, small-sized meiofauna and then macrofauna re-colonized the sea floor, mixing newly deposited organic fluff with the underlying ash. Consequently, ash deposits thinner than 1 mm have not often been observed as a continuous layer when cored six years after the eruption, while ash about 2 mm thick is now patchily bioturbated. In areas covered by ash thicker than 5 mm, mixing by benthic animals is controlled mainly by the adaptation of the burrowing fauna to variations in grain-size, the rate of background sedimentation, the availability of benthic food on and within the sediment and pore water oxygen levels. With respect to these factors, four provinces can be distinguished: (i) Along the Philippines margin run-off from land fuels primary production that, in turn, leads to a high benthic food content. The benthic fauna is adapted to a variable grain-size and rapid sedimentation. Therefore, mixing is intense and the preservation potential of the ash layer is low. (ii) In areas affected by deposition of hyperpycnites and turbidites, i.e. in canyons in front of river mouths and in the Manila Trench, the ash layer is preserved due to rapid burial. (iii) The area to the west to about 116° E receives low amounts of benthic food, benthic mixing is less intense and the preservation potential of the ash is high. (iv) The central South China Sea, where the ash is thinner than 3 cm, is affected by intense wind mixing and upwelling and the benthic food content is high; thus, the chance that the ash will be preserved as a sharp-based layer is low. Consequently, the style of ash preservation has palaeo-environmental significance. Older buried and burrowed event layers provide further information to elucidate the fate of the 1991 Pinatubo ash layer; in general their appearance fits with observations in the Recent. [ABSTRACT FROM AUTHOR]

A group of submerged ocean bottom sand ridges in the Bohai Sea, China, are shown in RADARSAT-1 and ENVISAT synthetic aperture radar (SAR) images. The sand ridges appear as fingerlike quasi-linear features in the SAR images. Examining the detailed local bathymetry chart, we find that these features coincide with the satellite images. The heights of the sand ridges are less than 10 m, and the water depth is between 10 and 30 m. The spacing of the sand ridges is about 10 km, and the length of the sand ridges is about 20 km. The same sand ridges are also visible on a Moderate Resolution Imaging Spectroradiometer (MODIS) true-color image. The semidiurnal and diurnal tidal currents in this area are almost parallel to the major axis of these sand ridges. These observations cannot be explained using the existing 1-D SAR imaging model, which is not applicable to sand ridges parallel to the tidal current. In this paper, we consider the shallow-water current bathymetry in a 2-D space. An analytical ocean model was applied to demonstrate the temporal variations of the current divergence and convergence that are induced by the along-sand-ridge-direction current and ridge interaction. A radar simulation model is used to simulate the variation of normalized radar cross section (NRCS) induced by the ocean surface current. The simulated NRCS variation is similar to that extracted from the calibrated SAR image. Simulation results also show that the NRCS variation becomes negligible when the ocean current is set to about half of the maximum tidal current. [ABSTRACT FROM AUTHOR]

The M2 tide in the Bohai, Yellow, and East China Seas (BYECS) is simulated by assimilating the TOPEX/Poseidon altimetry data with the adjoint method. The bottom friction coefficients (BFC) are supposed to be spatially varying. In this paper, the BFC at some grid points are chosen as the independent BFC and the BFC at the other grid points can be obtained through linear interpolation with these independent BFC. The independent BFC are selected uniformly over each 1° x 1° area and 120 independent BFC are obtained. Twin and practical experiments are carried out to discuss the spatially varying BFC. The results of twin experiments demonstrate that the adjoint method has a strong ability of inverting the prescribed BFC distributions combined with the spatially varying BFC. The prescribed BFC distributions are all successfully inverted. In practical experiments, the simulation precision has been highly increased by optimizing the spatially varying independent BFC. Three amphidromic points and a degenerate one appear in the cotidal charts of M2 tide and the results coincide with the observed M2 tide in BYECS fairly well. [ABSTRACT FROM AUTHOR]

In October 2002, staff from the Swire Institute of Marine Science (SWIMS), the University of Hong Kong, and the Natural History Museum (NHM), London, mounted a joint expedition to study submarine caves (zawns) off the eastern coast of Hong Kong, to test hypotheses that they may support either endemic or unusual communities, or they may act as refugia for such taxa. The present paper analyses the sedimentary macroinfaunal communities from that survey. Sampling was by hand-coring undertaken by SCUBA divers. Muddy-sand habitats within two caves were sampled in comparison with four control sites outside the caves, one of heterogeneous muddy sand, one of clean sand and two of fine mud; the samples were sieved across a 0.5 mm mesh. Sedimentary granulometry, water temperature, pH and dissolved oxygen were also measured. The benthic community within the caves showed a higher density and diversity than most of those described from non-cave sediments in Hong Kong waters. The community was distinct from that found at the control sites, partly owing to sediment granulometry differences. Thirty-three species were found only in the caves, some of which are known from elsewhere in non-cave habitats; six species are, to date, only known from these caves. It is concluded that the cave habitat conditions offer a stable and sheltered habitat which allows the development of a distinct community, although not representing an endemic fauna, as well as being a refuge for species under threat from anthropogenic or natural stresses outside the caves. [ABSTRACT FROM AUTHOR]

Some two hundred taxa have been recorded from Hong Kong's submarine caves. Of these, at least eleven are new to science. The majority of species occurring on the walls and roofs in particular, however, are not cave endemics and have been recorded from other habitats in Hong Kong and elsewhere. Unlike the Tethyan karsted limestone caves of Japan and the Philippines in the Asian region, and elsewhere, Hong Kong's cave fauna is similar to other local sea bed habitats at similar depths, probably because of their modernity. Although the sediments that make up the cave's floors appear more stable (in terms of their faunistic composition), there is evidence that they are periodically infilled and flushed out. This may be either on a seasonal basis or following severe tropical storm and typhoon events. It is therefore likely that the infaunal taxa of the cave's floors are partly sustained by episodic colonization. Notwithstanding the lack of an identifiable endemicity, the caves act as refugia for a number of otherwise rare taxa, for example, the ahermatypic corals Balanophyllia eguchii and Tubastrea falkneri, and fishes gain protection within them from locally intense fishing activities. The caves also appear to contain epifaunal communities that are representative of earlier, undisturbed times and environmental conditions in Hong Kong. It is recommended that (i) the two caves on Conic Island and Steep Island be designated as Sites of Special Scientific Interest; (ii) that other caves be searched for and studied and (iii) more long-term studies be made of their physical environments and the communities they support. [ABSTRACT FROM AUTHOR]

In recent years, increasing attention is being given to investigating the relationships between seafloor echo strength and sediment type. This aspect was assessed in a course of a marine survey conducted in Jiaozhou Bay near the city of Qingdao, China, where various sediment types are known to exist. Multi-beam echo data and sediment samples were acquired, processed and analyzed. The findings demonstrate that multi-beam echo strengths are strongly related to seabed types such as rock, sand and clay. Thus, echo strength increases progressively with the increase in sand content in gravely, sandy, and clayey sediments. However, echo strength is more sensitive to changes in sand content in fine-grained sediment and less sensitive in coarse-grained sediment. Also, high shell content of sediments greatly enhances the acoustic reflection. These findings help to predict seafloor sediment types by analyzing echo strength. [ABSTRACT FROM AUTHOR]