The Liuguhe River mouth sand ridges in the Liaodong Bay, Bohai Sea, provide a good example for further understanding the sedimentation of small-scale tidal sand ridges. However, little is known about their morphological and sedimentary characteristics. This paper presents a comprehensive study of these sand ridges using survey data from sub-bottom profiling, side-scan sonar mapping, and acoustic doppler current profiling, along with piston core analyses of grain-size and heavy minerals. The sand ridges span widths of 1-2.5 km and heights of 4-16 m, with diminishing heights toward the sea. Their cross-sections are asymmetrical, featuring gentler and steeper slope angles of less than 1.5 degrees and up to 4.5 degrees, respectively. Sand waves are widely superimposed on the sand ridges, exhibiting wavelengths of 0.7-62.3 m and heights of 0.11-3.12 m. The ridge sediment consists of well sorted medium sand, while the trough sediment consists of very poorly sorted silty sand, indicating that the ridges are coarser and better sorted than the troughs. The tidal deposits are characterized by high levels of magnetite and hematite. Provenance discrimination based on heavy mineral assemblages indicates that the sediment is mainly derived from the Liuguhe River. The sand ridges have been formed since the middle Holocene and are still active at present. The tidal currents are rectilinear. Near-bed currents exceeding the critical velocity of sediment motion account for 20 % of a tidal cycle, implying that the tidal currents are capable of maintaining the development of bedforms. The longitudinal axes of the sand ridges exhibit anticlockwise rotation relative to the direction of the maximum tidal current, with an angle of up to 30 degrees. The steeper slopes of the sand waves on both flanks of the sand ridges point to ridge crestlines, implying a tendency for sand streams to converge on the ridge crestlines. The sand ridges and adjacent troughs consist entirely of modern tidal deposits in the shoreward area, while the troughs are incised in the underlying strata with a thin layer of modern tidal deposits covering on the surface in the seaward area. Seaward decrease in sediment supplies may explain the seaward changes in ridge structures and heights.

通过对东海外陆坡–冲绳海槽GSW1孔沉积物孔隙水δ13C、δ18O、δ11B、δ37Cl同位素和C1?、SO2-4、K+、Na+等离子指标的分析,探讨了沉积物早期成岩作用、流体来源、迁移和氧化环境的变化.研究发现,GSW1孔孔隙水溶解无机碳主要来自海水和有机质,SO2-4浓度随深度下降比较平缓,C1?浓度远低于海水,该孔表层沉积物中硫酸盐消耗主要由有机质硫酸盐还原作用(OSR)所控制,甲烷厌氧氧化作用(AOM)发生在4 m以下更深的层位.OSR产生的H2S向上扩散富集并被氧化,是导致GSW1孔110～360 cm处SO2-4浓度未明显下降的主要因素.孔隙水SO2-4浓度整体随着深度增加呈减小的趋势,表明GSW1孔沉积环境由氧化、次氧化环境逐渐转变为还原环境.δ11B、δ37C1值垂向变化波动较大,一方面受到早期成岩阶段有机质降解的影响,也可能与孔隙流体扩散以及沉积物/孔隙水相互作用有关.

This study constrains the petrogenesis and regional tectono-magmatic evolution of volcanic rocks from Fuying and Dayushan Islands, northeast Fujian Province, southeast (SE) China, using petrological, zircon U-Pb geochronological, whole-rock geochemical and Sr-Nd-Pb isotopic data. New zircon U-Pb data show that volcanism occurred between 118 and 99 Ma. The volcanic rocks are dominantly alkalic to alkali-calcic, ferroan, and peraluminous in composition, and are characterized by strongly fractionated LREE and HREE, with depletion in Nb, Ta, Sr, and Eu. These features, together with their relatively enriched Sr-Nd-Pb isotopic compositions, imply that the volcanic rocks were derived from ancient lower crust and experienced extensive assimilation and fractional crystallization in the shallow crust. Taking into account previously published data, we conclude that the Fuying and Dayushan volcanic rocks were generated in a back-arc extensional setting in response to episodic slab rollback after flat subduction of the paleo-Pacific plate during the Cretaceous.CO 2021 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

沉积物中氧化还原敏感元素(Redox Sensitive Element,RSE)含量变化是上覆水体氧化还原环境良好的替代指标.本文通过冲绳海槽中南部两个柱状沉积物(深度:30 cm)粒度、总有机碳、总氮及其同位素含量和氧化还原敏感元素含量等指标,探究复杂环境背景下冲绳海槽柱状沉积物中RSE的赋存机理与环境指示意义.研究发现,柱状沉积物中除了Cr亏损,其他RSE均显示有不同程度的富集."粒控效应"对冲绳海槽柱状沉积物的RSE含量影响较小;分析可知,海水表层生产力是影响沉积物氧化还原环境的主要因素,通过Mn(氢)氧化物的吸附或解吸附作用实现RSE的富集与亏损.δCe、V/Cr、Ni/Co和V/(V+Ni)等指标指示沉积物整体处于氧化?弱氧化环境.沉积物中Mn元素通过还原作用以Mn2+形式向上扩散,在25～30 cm处被含氧间隙水氧化富集形成锰峰,指示柱状沉积物0～25 cm处为氧化环境,25～30 cm处为弱氧化环境.

The intersection of the Kyushu-Palau Ridge (KPR) and the Central Basin Rift (CBR) of the West Philippine Basin (WPB) is a relic of a trench-trench-rift (TTR) type triple-junction, which preserves some pivotal information on the cessation of the seafloor spreading of the WPB, the emplacement and disintegration of the proto-Izu-Bonin-Mariana (IBM) Arc, and the transition from initial rifting to steady-state spreading of the Parece Vela Basin (PVB). However, the structural characteristics of this triple-junction have not been thoroughly understood. In this paper, using the newly acquired multi-beam bathymetric, gravity, and magnetic data obtained by the Qingdao Institute of Marine Geology, China Geological Survey, the authors depict the topographic, gravity, and magnetic characteristics of the triple-junction and adjacent region. Calculations including the upward continuations and total horizontal derivatives of gravity anomaly are also performed to highlight the major structural features and discontinuities. Based on these works, the morphological and structural features and their formation mechanisms are analyzed. The results show that the last episode amagmatic extension along the CBR led to the formation of a deep rift valley, which extends eastward and incised the KPR. The morphological and structural fabrics of the KPR near and to the south of the triple-junction are consistent with those of the western PVB, manifesting as a series of NNE-SSW- and N-S-trending ridges and troughs, which were produced by the extensional faults associated with the initial rifting of the PVB. The superposition of the above two reasons induced the prominent discontinuity of the KPR in deep and shallow crustal structures between 15°N–15°30′N and 13°30′N–14°N. Combined with previous authors’ results, we propose that the stress produced by the early spreading of the PVB transmitted westward and promoted the final stage amagmatic extension of the CBR. The eastward propagation of the CBR destroyed the KPR, of which the magmatism had decayed or ceased at that time. The destruction mechanism of the KPR associated with the rifting of the PVB varies along strike the KPR. Adjacent to the triple-junction, the KPR was destroyed mainly due to the oblique intersection of the PVB rifting center. Whereas south of the triple-junction, the KPR was destroyed by the E-W-directional extensional faulting on its whole width.©2021 China Geology Editorial Office.

The concentrations of the heavy metals Cu, Pb, Zn, As, Cr, Co, and Ni of a total of 187 surface sediment samples collected from the western Taiwan Strait were analyzed. The distribution characteristics and degree of contamination of these elements were investigated. The mean concentrations of Cu, Pb, Zn, As, Cr, Co, and Ni in the surface sediments of the study area were 10.2 mg/kg, 18.3 mg/kg, 51.7 mg/kg, 7.5 mg/kg, 38.7 mg/kg, 8.0 mg/kg, and 16.5 mg/kg, respectively. The heavy metals in the study area were mainly from natural sources. The regional pollution load index (PLIzone) was 0.64, indicating that there was no contamination, and an area with a relatively high PLIzone was found in the northern part of the study area. Furthermore, the impacts of the rapid development of Fujian's marine economy on the marine environment in the past decade should be further compared and analyzed.

为研究北黄海北部沉积物中多环芳烃(PAHs)的分布特征及控制因素,于2016年7月在北黄海北部采集31个表层沉积物,并对沉积物中16种PAHs、总有机碳(TOC)和粒度进行分析测定.研究结果表明:该海区沉积物中多环芳烃的总含量范围在3.54 ～ 93.07 ng/g之间,平均含量34.50 ng/g,在辽东半岛东岸多环芳烃的分布呈由近岸向外海逐渐递减的趋势,总体看该区域PAHs的污染处于较低水平.主成分分析表明该海区沉积物中多环芳烃的主要来源是化石燃料燃烧源和石油源.该区域有机碳的分布受鸭绿江物质输入的影响,自东向西含量逐渐递减.粒度则呈现长山列岛以东,颗粒较粗;长山列岛以西,颗粒较细,空间变化相对较小.进一步分析表明,PAHs的分布主要受鸭绿江、辽东沿岸中小河流以及黄河的物质来源的影响;此外,该区水动力条件也是影响多环芳烃分布的重要因素.

世界大洋底蕴藏着丰富的金属矿产资源,其所含的锰、钴、镍、稀土等矿产是陆地含量的数十倍乃至数百倍或更高,因此是未来矿产资源的接替区.本文介绍了世界大洋多金属结核、富钴结壳、多金属硫化物及深海稀土等资源现状、分布及潜力,分析总结了21世纪以来国际海底区金属矿产勘查合同现状,并介绍了俄罗斯、巴布亚新几内亚、日本、中国等国家在其专属经济区内进行多金属结核、多金属硫化物开采实验的情况.由于世界大洋金属矿产资源丰富,潜力巨大,其勘查开发日益受到世界各国的重视,国际海底勘探合同不断增加,商业开发提上日程,但国际海底区的金属矿产资源开发仍面临技术、规章、环境等方面的制约和挑战.

Marine mud sediment contains huge quantities of information concerning with catchment change,climate change and environment evolution.Therefore,analyzing the fine grain sized fraction of sediment is a crucial method to extract environment evolution information.The surficial sediments collected from north-central of the North Yellow Sea (NYS)were sieved and the fine fraction (<63 μm)were tested for rare earth elements (REE).The test results indicate that,as bounded by Changshan Islands,the discrepancies of REE concentration and distribu-tion patterns between the east and west sediments of the mud deposition of the eastern Liaodong Peninsula (MDELP)was observed.The sediments in east of Changshan Islands,dominated by Yalu River,are defective in Eu and rich in REE,especially in light rare earth elements (LREE).However,the REE contents are low in the west side of Changshan Island and their distribution patterns are flat.Meanwhile,attributing to the wildly use of contrast agent (Gd-DTPA)in the Magnetic Resonance Imaging (MRI),the Gd in the sediment of the study area is obviously enriched.Furthermore,new recognition concerning with the sediment transport and origin is acquired:previous study believed the sediment source of MDELP is mainly derived from the Yalu River.However,our re-search reveals that,due to the transport of shelf circulation,there exists sediment exchange between the MDELP and the mud deposition of the west NYS:the sediment source in east of MDELP is controlled by the Yalu River, and that in the west of MDELP is mainly dominated by the Yellow River;in addition,Yalu River-derived sedi-ment is supplied to the mud deposition of the west NYS.

A comparative comparative study on the detrital mineral composition of stream sediments of the Yangtze River (Changjiang) and Yellow River (Huanghe) shows that, light minerals of the Yangtze River basin were mainly quartz, feldspar, and detritus, the compositional characteristics of light minerals differed among tributaries, the main stream had a generally higher maturity index than tributaries; heavy mineral content tended to decrease progressively from the upper stream to lower stream of the Yangtze River, the primary assemblage was magnetite-hornblende-augite-garnet-epidote, and diagnostic minerals of different river basins were capable of indicating the nature and distribution of the source rock. Detrital mineral assemblages in sediments of tributaries and the main stream of the Yellow River were basically similar, Primary heavy mineral assemblage was opaque mineral-garnet-epidote-carbonate mineral and alteration mineral. Variations in the contents of garnet, opaque mineral, and hornblende mainly reflected the degree of sedimentary differentiation in suspended sediment and the hydrodynamic intensity of a drainage system. The heavy mineral differentiation index F revealed sedimentary differentiation of diagnostic detrital mineral composition due to changes in regional hydrodynamic intensity and can serve as an indicator for studying the dynamic sedimentary environment of a single-provenance river and the degree of sedimentary differentiation of its detrital minerals. Changes in detrital mineral content of the Yellow River was not completely controlled by provenance but reflected gravity sorting of the detrital mineral due to variations in the ephemeral river hydrodynamic intensity and sedimentary environment, however the index changing of Yangtze River were mainly influenced by the complex sediment sources. Therefore caution must be exercised in using the detrital mineral composition of marginal sea to determine the contribution of the Yangtze River and Yellow River.

As a typical small and medium-sized river,the source to sink process of fine sediment from the Yalu Riv-er catchment to the mud deposition of the offshore eastern Liaodong Peninsula is characterized by a unique mecha-nism.Among other methods,remote sensing is an effective means to understand the process and mechanism of sediment transport in estuarine-continental shelf.In this paper,we measured the surface suspended sediment con-centration (SSC)in the eastern coast offshore of the Liaodong Peninsula,and then established a relationship be-tween the measured SSC and the Remote Sensing Reflectance (Rrs)of GOCI images to retrieve the long-term spa-tio-temporal distribution of surface SSC (April 201 1 to March 201 7).The effect of tidal current,strong wind and flood on the variations of surface SSC is further analyzed.The SSC transport pattern from the Yalu River to the mud deposition along eastern coast offshore of Liaodong Peninsula is finally discussed.The results show that the distribution of the surface SSC in the study area displays great spatial differences.Near the estuary,the surface SSC is of highest value and is greater than 500 g/m3 .While in other areas,the SSC value is less than 20 g/m3 . Concerning the seasonal variation,the surface SSC value in the dry season is higher than that in the flood season, which is mainly due to the enhanced wind waves by strong winds in the dry season.Although the surface SSC value is low in the flood season,it still significantly increased during the flood period of the Yalu River catchment.In ad-dition,as a typical small and medium-sized source-sink conveying system,the sediment transport mechanism from the Yalu River to the mud deposition along eastern coast offshore of Liaodong Peninsula is generally characterized by "deposit in summer and transport in winter".

Elemental geochemical and Sr–Nd isotopic signatures are used to decipher terrigenous sediments provenances and transport mechanisms in the South Yellow Sea during the Holocene. 87Sr/86Sr ratios in the Chinese and Korean riverine sediments overlap each other, whereas εNd values of Korean riverine sediments are generally less radiogenic in comparison to the Changjiang and Huanghe. Moreover, εNd values of these two large rivers appear unaffected by mineral sorting and are relative stable during the Holocene. We propose a three endmembers (i.e., the Changjiang, the Huanghe, and Korean rivers) mixing model to explain sediment provenances in the Central Yellow Sea Mud (CYSM). Mixing calculations show that the Huanghe is the major sediment contributor to the CYSM before ~ 8 ka (thousand years before 1950 CE), whereas the Changjiang has become the predominant sediment source after ~ 8 ka. Holocene changes in riverine sediment supplies to the CYSM are closely related to the oceanic circulation, monsoon climate, and drainage changes. After examining several hypotheses to explain the variations in 87Sr/86Sr ratios of Core YSC-1 during the past ~ 8 kyr, we tentatively attribute that to changes in the erosion patterns of the Changjiang Basin. This in turn is associated with the asynchronous evolution of monsoon precipitation in the upper (Indian Summer Monsoon) and middle-lower Changjiang (East Asian Summer Monsoon). Therefore, our results highlight significant influences of monsoon climate on erosion patterns within the Changjiang catchment at millennial timescales.

In order to reveal the influence factors dominating the water input and sediment discharge into the sea from the Yalu River catchment,the numerical model of HydroTrend3.0.4 with three scenarios,i.e.the climate change-driven,Human activities-driven,and combined climate change and human activities-driven senarios,is adopted to simulate water and sediment fluxes into coastal coastal ocean during the period of 1958-2012 at two river gauging stations.Results indicate that,during the period,water discharge of climate change-driven,Human activities-driven,and combined climate change and human activities-driven scenarios were 264.5 × 108 m3/a,264.3 × 108 m3/a and 263.7 × 108 m3/a,and sediment load was 5.53Mt/a,1.62Mt/a and 1.59Mt/a,respectively.The observed water discharge and sediment load were 259.2 × 108 m3/a and 1.48Mt/a.Under the scenario driven by climate change,the main factor dominating the variation of water discharge is precipitation,and the sediment flux variation under natural condition is mainly controlled by frequent flood events during the wet season.However,under the scenario of the combined climate change and human activities-driven,the intensifying human activities have caused dramatic change in sediment load into the sea:the anthropogenic impact can totally decrease the sediment flux of the Yalu River by 3.94Mt/a,including an increase in 1.2Mt/a sediment yielding by water and soil erosion,and a larger decrease in 5.14Mt/a by the dam interception effect.We also found that the sediment load entering the sea of the Yalu River before 1940 (pre-dams) was about 6.67Mt/a,5 times of the present sediment load into the sea.

2015年10月采集长江口及废黄河口51个沉积物样品,对沉积物中的多环芳烃(Polycyclic Aromatic Hydrocarbons,PAHs)的含量进行测定,探讨长江口及废黄河口海域表层沉积物中PAHs的分布组成、来源及潜在的生态风险评价.总PAHs的含量范围为4.23～292.39 ng/g,平均值含量为67.40 ng/g.研究区样品的PAHs含量呈现“北部低南部高”的空间分布特征,舟山群岛东部区域PAHs含量普遍偏高,长江口次之,废黄河口最低.与国内其他海区相比,研究区域PAHs总体处于中低等污染水平.运用统计分析和特征比值法对来源进行分析,研究区域沉积物中PAHs主要是以4环、5环为主,来源分析显示PAHs的主要来源为各类燃烧源及石油源的混合来源.根据效应区间低/中值法(ERL/ERM)评价结果显示,长江口及废黄河口海域的潜在生态风险很小,但对生态有一定的潜在威胁,也应该引起重视.

Natural gas hydrate research and development (R&D) have entered a phase of onshore and offshore field tests.Offshore hydrate production tests,however,are only performed by Japan and China.Through comprehensive summarization of two hydrate production testing cases in Japan and the careful study of Japan's industrialization plan,we found that Japan is rich in gas hydrate resources.Even though a great deal of manpower,materials and financial have been inputted into the R&D,but technology assuring stable gas production remains to be developed.Therefore,the hydrate industrialization will be a relatively long process.Before successful industrialization,they still have to do more on resource survey,demonstration and systematism of technology and equipment,making production test,and development of specifications and regulations.

To achieve a more robust understanding of the transport pattern of silt components in offshore areas,the grain size characteristics of 783 surface samples of fine-grained sediments are used to interpret the sediment transport pathways and predominant sedimentological conditions offshore the Shandong Peninsula,Yellow Sea.Based on the variation in the grain size composition,a regional "silt fractionation" was observed,and the very fine silt (VFSt) and the fine silt (FSt) displayed similar dynamic behaviors to that of the clay fraction during transportation and deposition,and these silts all acted as flocs.By contrast,the coarse silt (CSt) was primarily transported and deposited as single grains,indicating that the CSt content was the environmentally sensitive component in the sediments in the study area.The sediments displayed complicated sources based on the grain size analysis.In the northern part of the study area,the fine-grained sediment primarily originated from the Huanghe River Estuary (suspended or reworked,whereas in the eastern Shandong Peninsula,the sediments of the mud wedge were primarily composed of Huanghe-derived sediments and characterized by CSt-enriched,and in the southern Shandong Peninsula,the sediments primarily originated from the small rivers nearby.The marine fronts in the study area were thought to be the major factor controlling the settling and deposition of coarse silt.Further study should be carried out on the mechanisms that the fronts control the deposition of silty fractions in shelf settings.

In order to investigate the polycyclic aromatic hydrocarbons (PAHs) contamination of the surficial sediment in the south Coastal Mud Area off Zhejiang-Fujian (CMAZF),the content of polycyclic aromatic hydrocarbons in the surficial sediments were analyzed,and the distribution,sources and ecological threats of polycyclic aromatic hydrocarbons were also discussed.The results showed that the total PAHs concentrations of the surficial sediment in the south CMAZF ranged from 12.95 × 10-9 to 156.05 × 10-9.The results of isomeric ratio method and SPSS analysis indicated that PAHs in the study area mainly come from the combustion of coal and oil,and partly from oil source.The assessment results concerning with ecological risk evaluation of PAHs revealed that,to some extent,there might exist ecological risk in the surficial sediment of south CMAZF,and more attention should be paid to protect the marine environment.

Natural radioactivity is very important for the assessment of the marine sand property and usability.By using gamma spectrometry, the concentration of the natural radionuclides 226 Ra, 232 Th and 40 K have been measured in marine sand deposits from Liaodong Bay (LDB), North Yellow Sea (NYS), Zhoushan area (ZS), Taiwan Shoal (TS) and Pearl River Mouth (PR), offshore China, which are potential marine sand mining areas.The radiation activity equivalent (Raeq), indoor gamma absorbed dose rate (DR), annual effective dose (HR), alpha index (Ia), gamma index (Ig), external radiation hazard index (Hex), internal radiation hazard index (Hin), representative level index (RLI), excess lifetime cancer risk (ELCR) and annual gonadal dose equivalent (AGDE) associated with the natural radionuclides are calculated to assess the radiation hazard of the natural radioactivity in the marine sands offshore China.From the analysis, it is found that these marine sands are safe for the constructions.The Pearson correlation coefficient reveals that the 226 Ra distribution in the marine sands offshore China is controlled by the variation of the 40 K concentration.Principal component analysis (PCA) yields a two-component representation of the entire data from the marine sands, wherein 98.22% of the total variance is explained.Our results provide good baseline data to expand the database of radioactivity of building materials in China and all over the world.

Factors influencing millennial-scale variability in the thermocline depth (vertical mixing) and sea surface salinity (SSS) of the southern Okinawa Trough (OT) during the past 17,300 years were investigated based on foraminifer oxygen isotope records of the surface dweller Globigerinoides ruber sensu stricto and the thermocline dweller Pulleniatina obliquiloculata in the AMS 14C dated OKT-3 core. The thermocline depth is influenced by surface thermal buoyancy (heat) flux, in turn controlled by the annual mean insolation at 30°N and the strength of the East Asian winter monsoon (EAWM). Strong insolation and weak EAWM tend to increase buoyancy gain (decrease buoyancy loss), corresponding to shallow thermocline depths, and vice versa. Regional SSS is influenced by the global ice volume, the Kuroshio Current (KC), and vertical mixing. A deep thermocline coincides with a high SSS because strong vertical mixing brings more, saltier subsurface KC water to the surface, and vice versa. Local SSS (excluding the global ice volume effect) became lower in the northern OT than in the southern OT after ~9.2 ka, implying that Changjiang diluted water had stronger influence in the northern sector. SSS show no major changes during the Bølling/Allerød and Younger Dryas events, probably because the KC disturbed the North Atlantic signals. This argues against earlier interpretations of sea surface temperature records of this core. Wavelet and spectral analyses of the Δδ18OP-G (δ18O of P. obliquiloculata minus G. ruber s.s.) and δ18Olocal records display 1,540-, 1,480-, 1,050-, 860-, 640-, and 630-year periods. These are consistent with published evidence of a pervasive periodicity of 1,500 years in global climate as well as EAWM and KC signatures, and a fundamental solar periodicity of 1,000 years and intermediary derived periodicity of 700 years.

2012～2013年在江苏王港典型互花米草盐沼湿地采集了4根柱状样和48个表层样,通过对比光滩和互花米草滩沉积物中总有机碳(TOC)、活性有机碳(LC)和顽固性有机碳(RC)含量,结合互花米草生物量季节变化,探讨了互花米草生物量对沉积物中有机碳组分的影响.结果表明,互花米草滩表层沉积物中LC含量及其中互花米草来源比例,均与互花米草地表枯落物量密切相关,但存在两个月的“相位差”,这与枯落物有机碳快速分解时间一致,说明枯落物通过提高沉积物中LC的含量,提高了TOC含量并改变了TOC组分.互花米草地下生物量主要分布在0～20 cm深度内,该深度范围内互花米草滩各形态碳含量较高,LC和RC含量分别达到了光滩的4.03倍和1.70倍;同时,TOC中LC所占比重在0～20 cm深度内较高,也表现出先下降后不变的趋势;另外,不同深度各形态有机碳含量均与地下生物量之间存在较好的正相关关系,说明地下生物量是影响沉积物各形态碳含量的重要因素,且对LC的影响大于RC.