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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]

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: 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]

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]

Abstract: Recent floodplain soft soil is widespread along the lower reaches of the Yangtze River in western Nanjing, China, an area of new residential development and underground space utilisation such as subway lines and tunnels under rivers in Nanjing city. Construction experience in this area in the last two decades shows that ground and underground engineering are susceptible to accidents. The accidents are fundamentally due to the lack of a clear and detailed understanding of the geotechnical and geological properties, in particular the differential consolidation settlement of the soft soil. In this context, this paper studies the behaviour and engineering implications of such soil. First, we present the soil''s geological background and sedimentary features, test its geotechnical properties, and identify its material composition by X-ray diffraction and SEM. Then, we investigate changes of microstructure at different depths and under different applied loadings, and corresponding engineering implications under consolidation and compression. Finally, by referring to a microstructure classification system for marine sediment, we suggest a combined type of microstructure for the floodplain soft soil. [Copyright &y& Elsevier]

Study indicates that the elements rich in marine floor hydrothermal fluids have a positive influence, not only on total organic carbon (TOC), but also on the abundance of SiO2 in some Middle-Upper Proterozoic strata. The TOC bears a better positive correlation with abundance of SiO2. By the correlation analysis between organic matter and sea-floor hot fluid characterized trace elements such as P, Cu, Zn, Ni, Ba, etc in marine carbonate rocks, we conclude that organic matter enrichment of carbonate rocks were related to marine floor hydrothermal activity in a part of layers. Some thin-layered cherts, which were thought to be the indicators of hydrothermal activity, frequently occurring in Gaoyuzhuang, Wumishan, Tieling and Xiamaling formation support our conclusion. With the increasing of trace elements in marine carbonate rocks, the TOC and Fe/Ti ratio is creasing. In contrast, the Al/(Al+Fe+Mn) ratio is usually decreasing. [ABSTRACT FROM AUTHOR]