The Sources and Transport Patterns of Modern Sediments in Hangzhou Bay: Evidence from Clay Minerals

Clay mineral compositions of 199 offshore surface sediment samples collected from the Hangzhou Bay have been analyzed. The clay minerals in the sediments from the Hangzhou Bay are dominated by illite(58.7%, on average), followed by chlorite(20.3%), kaolinite(16.9%) and smectite(4.1%). Two provinces were classified by Q-mode cluster analysis. Class Ⅰ with relatively low amounts of illite and smectite is widely distributed in the Hangzhou Bay, especially concentrated in the top and mouth of the bay, and the northern and southern nearshore areas. Class Ⅱ with comparatively high amounts of illite and smectite is mainly concentrated in the central part of the bay with the water depth of 8–10 m. By comparing clay mineral compositions with the neighbouring regions, we can find that the sediments in the Hangzhou Bay are mainly influenced by the resuspension and repeated deposition of particles from the Yangtze River due to the strong dynamic environment. In particular, the clay fraction of Class Ⅰ is mainly supplied by the Yangtze River, while the sediments of Class Ⅱ are mixture of the clay minerals carried by the Yangtze River and Qiantang River. In general, the distributions of clay minerals in the northern bay are affected by Yangtze River runoff, coastal current and flood tide together, and in the southern they are mainly affected by the Qiantang River runoff and ebb tide.     

Mesozoic Deformation and Its Geological Significance in the Southern Margin of the South China Sea

The pre-Eocene history of the region around the present South China Sea is not well known. New multi-channel seismic profiles provide valuable insights into the probable Mesozoic history of this region. Detailed structural and stratigraphic interpretations of the multi-channel seismic profiles, calibrated with relevant drilling and dredging data, show major Mesozoic structural features. A structural restoration was done to remove the Cenozoic tectonic influence and calculate the Mesozoic tectonic compression ratios. The results indicate that two groups of compressive stress with diametrically opposite orientations, S(S)E– N(N)W and N(N)W–S(S)E, were active during the Mesozoic. The compression ratio values gradually decrease from north to south and from west to east in each stress orientation. The phenomena may be related to the opening of the proto-South China Sea(then located in south of the Nansha block) and the rate at which the Nansha block drifted northward in the late Jurassic to late Cretaceous. The Nansha block drifted northward until it collided and sutured with the southern China margin. The opening of the present South China Sea may be related to this suture zone, which was a tectonic zone of weakness.     

Modeling of embankment beneath marine deposited soft sensitive clays considering straightforward creep degradation

Abstract

One method straightforwardly describing the creep degradation behavior of soft marine clay is proposed and applied to the embankment modeling. Based on the experimental phenomena, the evolution of creep coefficient of soft structured clay is identified comparing with reconstituted clay, and formulated using the creep coefficient of reconstituted clay and a creep-based structure parameter relating to the inter-particle bonding. The contributions of inter-particle bonding and debonding to creep coefficient are thus considered and the creep degradation behavior is then captured straightforwardly. The creep coefficient is extended to 3D and incorporated into a newly developed elasto-viscoplastic model to describe the creep degradation in a direct way. Based on the correlations, the liquid limit is adopted as the viscosity related input parameter. The model is derived using Newton–Raphson algorithm and implemented into a Finite Element code for coupled consolidation analysis. The general applicability on creep degradation of the model is validated by simulating 1D creep, 1D CRS (constant strain rate) and 3D undrained creep tests. Finally, the enhanced model considering creep degradation is applied and validated by simulating one test embankment and one test fill on marine deposited soft sensitive clays.     

The Relationship between Propagation Time and Sound Velocity Profile for Positioning Seafloor Reference Points

This paper focuses on the relationship between the propagation time and the integral of the sound velocity profile (SVP) with respect to depth (SVP area for short) for positioning seafloor reference points. We proved a linear relationship between the propagation time and the SVP area and defined its mathematical expression (ST law). We showed in three simulations of possible variations in SVPs (random errors, internal waves, or a combination of both) that this ST law is verified. Using this new law in a simulated experiment, the ranging residuals due to sound velocity change through time are significantly improved. With this method, monitoring the SVP while acquiring travel times to a submerged transponder can significantly reduce the positioning errors of the transponder.     

Research of Power Take-off System for “Sharp Eagle Ⅱ” Wave Energy Converter

The "Sharp Eagle" device is a wave energy converter of a hinged double floating body. The wave-absorbing floating body hinges on the semi-submerged floating body structure. Under the action of wave, the wave-absorbing floating body rotates around the hinge point, and the wave energy can be converted into kinetic energy. In this paper, the power take-off system of "Sharp Eagle II" wave energy converter(the second generation of "Sharp Eagle") was studied, which adopts the hydraulic type power take-off system. The 0-1 power generation mode was applied in this system to make the "Sharp Eagle II" operate under various wave conditions. The principle of power generation was introduced in detail, and the power take-off system was simulated. Three groups of different movement period inputs were used to simulate three kinds of wave conditions, and the simulation results were obtained under three different working conditions. In addition, the prototype of "Sharp Eagle II" wave energy converter was tested on land and in real sea conditions. The experimental data have been collected, and the experimental data and simulation results were compared and validated. This work has laid a foundation for the design and application of the following "Sharp Eagle" series of devices.     

The CM carbonaceous chondrite regolith Diepenveen

A carbonaceous chondrite was recovered immediately after the fall near the village of Diepenveen in the Netherlands on October 27, 1873, but came to light only in 2012. Analysis of sodium and poly‐aromatic hydrocarbon content suggests little contamination from handling. Diepenveen is a regolith breccia with an overall petrology consistent with a CM classification. Unlike most other CM chondrites, the bulk oxygen isotopes are extremely ¹⁶O rich, apparently dominated by the signature of anhydrous minerals, distributed on a steep slope pointing to the domain of intrinsic CM water. A small subset plots closer to the normal CM regime, on a parallel line 2 ‰ lower in δ¹⁷O. Different lithologies in Diepenveen experienced varying levels of aqueous alteration processing, being less aqueously altered at places rather than more heated. The presence of an agglutinate grain and the properties of methanol‐soluble organic compounds point to active impact processing of some of the clasts. Diepenveen belongs to a CM clan with ~5 Ma CRE age, longer than most other CM chondrites, and has a relatively young K‐Ar resetting age of ~1.5 Ga. As a CM chondrite, Diepenveen may be representative of samples soon to be returned from the surface of asteroid (162173) Ryugu by the Hayabusa2 spacecraft.     

辽河口沉积物中古菌和细菌群落结构分析

本研究旨在了解辽河口表层沉积物中古菌和细菌的群落结构组成、多样性及其与环境因子之间的相关性。采用构建古菌和细菌16S rRNA基因文库的方法,应用Illumina Miseq测序技术进行序列分析。结果表明:辽河口表层沉积物中细菌多样性高于古菌多样性,近岸细菌和古菌多样性高于远岸,即河相区（0.8~7.04）细菌多样性高于混合区（13.1~20.7）和海相区（24.2~31.5）;主要古菌群落为奇古菌门（Thaumarchaeota,72.73%）和广古菌门（Euryarchaeota,25.05%）,其中泉古菌门（Crenarchaeota,0.001%）只在河相区站位被发现;细菌群落组成中变形菌门（Proteobacteria,61.94%）为该河口的优势菌群,其次为拟杆菌门（Bacteroidetes,11.21%）和酸杆菌门（Acidobacteria,5.59%）,其他门类如蓝藻门（Cyanobacteria,3.03%）等比例较小。与环境因子的冗余度分析表明:影响表层沉积物中古菌群落分布的主要环境因子依次为氨盐、泥、酸碱度、盐度、电导率和砂,而细菌群落的分布主要受到溶氧、泥、砂、黏土和总磷的影响。由此可见,不同环境条件下微生物的群落结构存在空间异质性,不同微生物对同一环境条件的响应亦不同。     

利用资料同化方法优化观测系统的空间布局:以泰国湾为例

海洋观测费用高昂,设计科学高效的观测系统可以充分发挥观测的效能。本文以泰国湾高频地波雷达观测系统为例,利用数据同化方法对观测系统进行了最优布局。首先基于FVCOM海洋数值模式建立了泰国湾海域高分辨率三维斜压水动力模式,在此基础上利用一种改进的高效集合卡曼滤波同化方法对岸基高频地波雷达表层海流观测系统开展观测效能评估数值实验。通过观测区域的不同组合方式将3个区域的雷达表层海流数据同化到数值模式中,实验结果表明,岸基高频地波雷达表层海流观测系统可有效降低高分辨数值模式的海流模拟误差。但不同观测区域的组合提供的观测数据对改善海流模拟的作用存在明显差别,泰国湾现有观测系统雷达站位布设方式应进一步优化。本文最后给出了研究区域最优观测站位的布局方案,可作为下一步观测系统进行布局调整的指导。     

威海南部近岸泥质区晚更新世以来的重矿物组合特征及对物源的指示

对威海南部近岸泥质区WHZK01孔（孔深25.1 m）岩心开展重矿物分析,结果表明,WHZK01孔主要以普通角闪石（22.1%）、磁铁矿（20.0%）和绿帘石（17.7%）为主,晚更新世以来自下而上可分为3个矿物组合带。氧同位素3期晚期河流相沉积（DU3）主要矿物组合为普通角闪石-绿帘石。末次冰后期河漫滩-河口湾相沉积（DU2）主要矿物组合为普通角闪石-绿帘石-钛铁矿-褐铁矿。全新世滨-浅海相沉积（DU1）主要矿物组合为磁铁矿-绿帘石-片状矿物-自生黄铁矿。重矿物物源判别表明,DU3和DU2层沉积物主要来自山东半岛南部沿岸河流输入。DU1层沉积物主要来自沿岸流输运的大量黄河细粒物质,沿岸河流物质和岛屿侵蚀物也有少量贡献。     

Potential deposition of biogenic silica source sediment in the Paleo-Yangtze Grand Underwater Delta estimated with satellite remote sensing

Biogenic silica sediment constitutes one of the critical sources of particle income in the oceans. In this paper, satellite remote sensing of primary production, sinking flux, and molar ratio of Si/C were utilized to elucidate potential biogenic silica sediment in the Paleo-Yangtze Grand Underwater Delta. Primary production retrieval showed that daily primary production in the Paleo-Yangtze Grand Delta was 3.3–10.8?Mt?d^?1, with 5.8?Mt?d^?1 on average. Sinking flux, retrieved with in situ observations and satellite remote sensing, was within the range of 109–657?mg?Cm^?2?d^?1, or about 23% of total primary production, on average. A molar ratio of Si/C of 0.11–0.45 interval was used in the area, for the Paleo-Yangtze Grand Delta was similar to coastal water and affected by many factors. Considering that phytoplankton in the Paleo-Yangtze Grand Underwater Delta is mainly diatom (80% on average), about 0.21–0.88 billion tons of biogenic silica source sediment is produced in the area annually. With the reduction of land source sediment occurring in recent years in the area, biogenic silica sediment may be one of the dominant sediment sources for maintaining the future stability of the Paleo-Yangtze Grand Underwater Delta.