Burial fluxes and sources of organic carbon in sediments of the central Yellow Sea mud area over the past 200 years

Long-term changes of composition, sources and burial fluxes of TOC （total organic carbon） in sediments of the central Yellow Sea mud area and their possible affecting factors are discussed in this paper. Firstly, similarity analysis is employed to confirm that the carbon burial features resulted from two collected cores are typical in the central Yellow Sea mud area where YSWC （Yellow Sea Warm Current） is prevalent. On this basis, the burial flux of TOC here was considered to be 235.5-488.4 pmol/（cm^2.a） since the first industrial revolution, accounting for about 70%-90% among burial fluxes of TC （total carbon） in the sediments. Compared TOC/TC ratio in the two cores with that in other marine sediments worldwide, we suggest that the growth of calcareous/non-calcareous organisms and dissolution of IC （inorganic carbon） are important factors controlling the TOC/TC ratio in sediment. Results of two-end mixed model based on fi13C data indicate that marine-derived organic carbon （OCa） is the main part among total burial organic carbon which accounts for a ratio over 85%. Due to the high TOC/TC ratio in the two cores, TC in the sediments also mainly exists as OCa, and the proportion of OCa is about 60%-80%. Away from the shore and relatively high primary production in upper waters are the main reasons that OCa is predominant among all burial OC in sediments of the central Yellow Sea mud area. Burial of OC in this mud area is probably mainly influenced by the human activities. Although the economic development during the late 19th century caused by the first industrial revolution in China did not obviously increase the TOC burial fluxes in the sediments, the rise of industry and agriculture after the founding of new China has clearly increased the TOC burial flux since 1950s. Otherwise, we also realize that among TC burial fluxes, TIC account for about 10%-30% in sediments of the central Yellow Sea mud area, so its burial could not be simply ignored here. Distinct from TOC burial, long-term TIC burial fluxes variations relate with climate changes more closely： the East Asian summer monsoon may influence the strength of the Huanghe River （Yellow River） flood, which could further affect the transport of terrestrial IC from land to the central Yellow Sea as well as the burial of these IC in the sediments.

Geochemical and Grain-Sized Implications for Provenance Variations of the Central Yellow Sea Muddy Area Since the Middle Holocene

Based on high-resolution analysis to a 280-cm long sediment core obtained from the muddy area in the central Yellow Sea, we examined the provenance of muddy sediments and discussed the changing marine sedimentary environment since the middle Holocene. The results indicated that fine-grained sediments in the muddy area were mainly derived from the Huanghe(Yellow River) and Changjiang(Yangtze River) with considerable stepwise variations during the past 6.6 kyr. The Yellow Sea Warm Current was initiated at 6 kyr when the sea level was high together with the enhanced East Asian Winter Monsoon. These in combination established the framework of shelf circulation in the Yellow Sea that began to trap the river-derived fine-grained sediments. From 4.9 kyr to 2.8 kyr, both the Kushiro Current and East Asian Monsoon were significantly weakened, reducing the delivery of Changjiang sediments to the muddy area. As a result, the sediments were mainly originated from the Huanghe. From 2.8 kyr to 1.5 kyr the continuously weakened East Asian Winter Monsoon and enhanced Yellow Sea Warm Current entrapped more fine-grain sediments. Whereas the enhanced East Asian Winter Monsoon and the human caused increase in sediment load of the Huanghe since 1.5 kyr, and direct delivery of Huanghe sediments to the Yellow Sea during 1128–1855 AD might dominated the sedimentation in the study area. The stepwise variations of the sediment provenance and composition of the Central Yellow Sea muddy sediments are of importance to understanding the formation of muddy deposit in the central Yellow Sea and the associated variations of marine environment since the middle Holocene.

The difference analysis of physical-mechanical properties of sediments in the central South Yellow Sea and Zhe-Min coastal area in China

The difference analysis of physical-mechanical properties of muddy sediments is made in the central South Yellow Sea and the Zhe-Min（Zhejiang Province to Fujian Province of China） coastal area. The results show that sediments in the two regions are both dominated by mud. There are perfect negative power function correlations between the water content and the density, the compression coefficient and the compression modulus; a good positive power function correlation between the liquid limit and the plastic limit, a perfect positive linear correlation between the water content and the void ratio, and a perfect polynomial function correlation between the miniature vane shear strength and the pocket penetration resistance. In general, compared with sediments in the Zhe-Min coastal area, sediments in the central South Yellow Sea possess high water content, high void ratio,low density, high plasticity, high compressibility, low shear strength. The causes of the differences between physical-mechanical properties of sediments are analyzed from the topographic features, material sources,hydrodynamic conditions, deposition rate, and material composition. Compared with the Zhe-Min coastal area,the central South Yellow Sea is far from the Mainland and low-lying; has poor hydrodynamic condition; the materials diffused to the area are less and dominated by fine clay, have the high content of smectite and organic matters. These factors lead to sediments of the central South Yellow Sea has the higher water content, the higher plasticity, the lower density, and the lower strength than sediments in the Zhe-Min coastal area.

Rates and fluxes of centennial-scale carbon storage in the fine-grained sediments from the central South Yellow Sea and Min-Zhe belt, East China Sea

The global carbon cycle has played a key role in mitigating global warming and climate change.Long-term natural and anthropogenic processes influence the composition,sources,burial rates,and fluxes of carbon in sediments on the continental shelf of China.In this study,the rates,fluxes,and amounts of carbon storage at the centennial scale were estimated and demonstrated using the case study of three fine-grained sediment cores from the central South Yellow Sea area(SYSA) and Min-Zhe belt(MZB),East China Sea.Based on the high-resolution temporal sequences of total carbon(TC)and total organic carbon(TOC)contents,we reconstructed the annual variations of historical marine carbon storage,and explored the influence of terrestrial and marine sources on carbon burial at the centennial scale.The estimated TC storage over 100 years was 1.18×10~8 t in the SYSA and 1.45×10~9 t in the MZB.The corrected TOC storage fluxes at the centennial scale ranged from 17 to 28 t/(km^2·a)in the SYSA and from 56 to 148 t/(km^2·a)in the MZB.The decrease of terrestrial materials and the increase of marine primary production suggest that the TOC buried in the sediments in the SYSA and MZB was mainly derived from the marine autogenetic source.In the MZB,two depletion events occurred in TC and TOC storage from 1985 to 1987 and 2003 to 2006,which were coeval with the water impoundment in the Gezhouba and Three Gorges dams,respectively.The high-resolution records of the carbon storage rates and fluxes in the SYSA and MZB reflect the synchronous responses to human activities and provide an important reference for assessing the carbon sequestration capacity of the marginal seas of China.

Composition, Source and Environmental Indication of Clay Minerals in Sediments from Mud Deposits in he Southern Weihai Offshore, Northwestern Shelf of the South Yellow Sea, China

Studying the sedimentary characteristics of the muddy area along the Yellow Sea shelf is of great significance for deep-ening the understanding of the climate and environment evolution since the last glacial period.Recently,a small muddy area developed in the southern Weihai offshore has attracted a lot of attention.Based on high-resolution grain size,clay mineral,AMS14C,and OSL data of sediments from the core WHZK01 in the muddy area,we acquired a new understanding of sedimentary characteristics,sources and paleoclimatic environment during the last 13 kyr.The results show that the core WHZK01 sediments were mainly from the Yellow River and local rivers along the coast.However,the sources varied for different deposition units.The riverbed(before 13 kyr BP)and fluvial plain deposits(13-10 kyr BP)were mainly from local river inputs.The very thin littoral deposits from 10 kyr BP to 8 kyr BP also mainly originate from coastal river inputs,while the littoral-neritic deposits since 8 kyr BP were dominated by the Yellow River materials and partly supplied by the coastal rivers and the island erosion.In addition,five events related with the strong East Asian winter monsoon(EAWM)during the intervals of 13.0-11.0 kyr BP,10.0-8.2 kyr BP,7.0-5.0 kyr BP,3.5-2.5 kyr BP,and 1.2-0.5 kyr BP were iden-tified.Three events related with the enhancement of the EAWM since the middle Holocene have strengthened the transport capacity of the coastal currents of the Shandong Peninsula.Meanwhile,more Yellow River-derived distal sediments were deposited to the southern Weihai offshore and formed wedge-shaped muddy bodies.In short,the ratio of smectite/illite could be used as an effective EAWM indicator since 13 kyr BP on the northwestern shelf of the South Yellow Sea.

Sedimentary Characteristics of the Second Marine Layer During the Late Marine Isotope Stage 3 in Southern Yellow Sea and Their Response to the East Asian Monsoon

We use the particle size of sediments in core YS01A to study the sedimentary environment of the mud deposit in the central South Yellow Sea of China during late Marine Isotope Stages 3 （MIS3; 40.5 kyr-31.3 kyr）. In addition, the East Asian Monsoon and its relationship with the North Atlantic Ocean climate change are discussed based on the sensitive grain-size calculation and the spectrum analysis. The results show that during late MIS3, the muddy area in the central South Yellow Sea experienced the evolution of coastal facies, shallow marine facies, coastal facies, and continental facies, with weak hydrodynamic conditions. Compared with other climate indicators, we found that there were many century to millennium-scale climate signals documented in the muddy area sediments in the central South Yellow Sea. According to our particle size results, three strong winter monsoon events occurred at 37.6kyr, 35.6kyr and 32.2kyr. The East Asian Winter Monsoon records in core YS01A are consistent with the Greenland ice core and the Hulu cave stalagmite 8180. The millennial and centennial scale cycles, which are 55 yr, 72 yr, 115 yr, 262 yr respectively, correspond to solar activity cycles, while the 1049 yr and 2941 yr cycles correspond to the Dansgaard-Oeschger cycles. These cycles indicate that the paleoclimate evolution of the area was controlled by the solar activities, with the high-latitude driving thermohaline circulation as the main energy conveyor belt, followed by the sea-air-land amplification of the winter monsoon variation in the central Yellow Sea in the late MIS3.

Last 150-Year Variability in Japanese Anchovy (Engraulisjaponicus) Abundance Based on the Anaerobic Sediments of the Yellow Sea Basin in the Western North Pacific

Relatively short historical catch records show that anchovy populations have exhibited large variability over multi-decadal timescales.In order to understand the driving factors(anthropogenic and/or natural) of such variability,it is essential to develop long-term time series of the population prior to the occurrence of notable anthropogenic impact.Well-preserved fish scales in the sediments are regarded as useful indicators reflecting the fluctuations of fish populations over the last centuries.This study aims to validate the anchovy scale deposition rate as a proxy of local anchovy biomass in the Yellow Sea adjoining the western North Pacific.Our reconstructed results indicated that over the last 150 years,the population size of anchovy in the Yellow Sea has exhibited great fluctuations with periodicity of around 50 years,and the pattern of current recovery and collapse is similar to that of historical records.The pattern of large-scale population synchrony with remote ocean basins provides further evidence proving that fish population dynamics are strongly affected by global and basin-scale oceanic/climatic variability.

Grain size records reveal variability of the East Asian Winter Monsoon since the Middle Holocene in the Central Yellow Sea mud area,China

Three cores （ZY-1, ZY-2 and ZY-3） retrieved from the Central Yellow Sea mud （CYSM） were analyzed in sensitive grain size and AMS J4C dating to reconstruct the history of the East Asian Winter Monsoon （EAWM） since the Middle Holocene in the study area. The results show that these data provide a continuous history of the EAWM over the past 7.2 ka and that the EAWM can be divided into three periods： strong and highly fluctuating during 7.2-4.2 ka BP; moderate and relatively stable during 4.2-1.8 ka BP; and weakened during 1.8-0 ka BP. Compared with the East Asian Summer Monsoon （EASM） recorded in the previous studies, the evolutionary history of the EAWM broadly follows the orbital-derived winter insolation with a similar long-term step-decreased trend as the EASM. At the centennial scale, however, the EAWM intensified events correlate well with the EASM weakened events and the North Atlantic climatic variations （Bond events 0 to 5） within the dating error, most likely forced by the reduction of solar irradiance through changes in the oceanic-atmospheric circulation patterns.

Trend analysis of sediment grain size and sedimentary process in the central South Yellow Sea

With the method of trend analysis of sediment grain size, the sediment transport trend of the fine-grained sediments area in the central South Yellow Sea was studied. The results demonstrated that there is a sedimentation center around the point of 123.4° E, 35.1°N, and the sediments outside the center are transported to it. The patterns of sediment transportation and deposition in the Yellow Sea should be controlled by cyclonic circulation (including the Yellow Sea Cold Water Mass) and cold water gyre. The study also showed that the method of trend analysis of sediment grain size has prospective utilization in the fine-grained sediment deposited area on large-scale continental shelf.

Tectonic Evolution and Hydrocarbon Potential in Northern Area of the South Yellow Sea

The northern area of the South Yellow Sea, located in the offshore region of China, resulted from the continental-continental collision orogeny during the Mesozoic and can be divided into four stages in terms of tectonic evolution： （1） pre-orogenic passive continental margin stage （Z-T2）; （2） foreland basin stage corresponding with the late phase of the Sulu （苏鲁） orogeny （J3-K）; （3） post-orogenic intracontinental rifted basin stage （K2t-E）; and （4） regional subsidence and coverage stage （N-Q）. Based on detailed investigation and study of the intracontinental rifted basin, hydrocar- bon source rocks of Late Cretaceous Taizhou （泰州） Formation distributed well in the basin, and four reservoir-cap combinations as well as numerous trap structures were found. As a result, the geological conditions would be excellent for reservoir formation in the basin, and the oil resource amount is estimated at about 20×10^8 t, which makes the basin a major target for hydrocarbon exploration in the South Yellow Sea.

北黄海西部泥质区全新世以来沉积有机碳埋藏特征

北黄海西部泥质区沉积环境稳定、沉积记录连续,是重建过去周边流域变化与黄海海洋环境信息的良好载体。目前围绕北黄海西部泥质区沉积有机碳的研究工作多局限于通过表层沉积物揭示其现代分布特征,对于该泥质区长时间尺度沉积有机碳埋藏过程与机制的研究相对薄弱。通过北黄海西部泥质区W03岩芯的总有机碳指标,重建了全新世以来北黄海西部沉积有机碳的埋藏特征,探讨了气候及海洋环境变化对北黄海西部沉积有机碳埋藏的控制机制。研究表明:海平面上升的停滞期(10.3~9.8 cal.kaBP),发育硬质黏土层,有机碳以陆源输入为主(60.7%),动荡的沉积环境导致总有机碳含量相对较低,平均含量仅为0.22%;海平面上升期(9.8~7.0 cal.kaBP),海源有机碳的贡献增加(47.7%),相对稳定的沉积环境有利于该时期有机碳的埋藏;高海平面以来(7.0 cal.kaBP至今),黄海环流体系逐渐形成,陆源有机碳输入随着东亚冬季风驱动的沿岸流强度变化发生相应的改变,海源有机碳的贡献继续增加(50.0%),总有机碳的含量升高至0.58%。北黄海西部泥质区全新世以来沉积有机碳埋藏主要受控于海平面变化和海洋环流体系的运动。

南黄海SYS90-1A孔第四纪沉积物磁性地层学研究

可靠的年代地层框架是开展南黄海地区第四纪环境演变研究的基础。目前南黄海南部地区缺乏可靠年代学控制的长序列钻孔。通过对南黄海南部SYS90-1A孔(孔深90.1 m)沉积物开展详细的磁性地层学研究,并结合AMS14C测年结果及区域已有磁性地层学结果,建立南黄海南部地区第四纪沉积物年代地层框架。结果显示,SYS90-1A孔岩芯记录了从布容(Brunhes)正极性时至松山(Matuyama)负极性时上部,包括Kamikatsura和Santa Rosa地磁漂移事件。早、中更新世界线即布容正极性时与松山负极性时界线(B/M界线)深度位于74.2 m,Kamikatsura和Santa Rosa地磁漂移事件深度分别位于79.75~82.47 m和85.25~87.74 m。根据Kamikatsura和Santa Rosa地磁漂移事件的年代控制点和平均沉积速率,推算钻孔底部年龄为0.96 Ma。南黄海SYS90-1A孔早更新世晚期的沉积速率约为8.66 cm/ka,中更新世以来的沉积速率约为9.5 cm/ka,而全新世以来的沉积速率为12.8 cm/ka,沉积速率自早更新世晚期以来呈增加趋势。这一结果不仅为南黄海南部第四纪沉积物研究提供了有效的年代学约束,而且为南黄海地区第四纪地层划分和对比、沉积环境与气候变化、物源示踪等研究提供了重要的时间标尺。

深水中大型气田滚动勘探技术体系与成效——以琼东南盆地中央峡谷A边际气田为例

为了促进琼东南盆地中央峡谷深水A边际气田开发,引入目标搜索研究、目标评价研究、目标钻探研究等完整气田滚动勘探技术体系。A边际气田目标搜索除利用传统的区带油气潜力目标搜索技术外,提出评价过程目标搜索技术,共搜索了5个油气潜力区块,并优选A4构造进行油气目标评价。从圈闭解释与落实、圈闭烃类检测两方面对A4构造油气成藏主控因素开展研究。A4构造中部预测优势含气区具有强振幅属性、低密度、低速度、低纵波阻抗、低纵横波速度比等有利含气信息特征,总体为Ⅲ类AVO异常,且能够升级HL_0气组控制天然气地质储量,部署滚动探井A4-1井实施钻探,在黄流组钻遇气层超20 m,莺歌海组二段钻遇可疑气层近10 m,获得天然气探明地质储量近30亿立方米,钻探效果好。滚动勘探研究在深水A边际气田的应用,不仅有效地促进了A边际气田后续滚动勘探活动,而且证实了滚动勘探同样适用于深水油气勘探。

全新世以来南黄海中部泥质区沉积物的源汇过程及其控制因素

南黄海中部泥质区沉积了大量来自邻近河流的陆源沉积物,是研究沉积物物源的良好区域,但其沉积物的输运过程和控制因素尚不明确。本文利用南黄海中部泥质区岩芯YSCW-1中沉积物的粒度和元素组成特征,查明自全新世以来研究区沉积物的源汇过程及其控制因素。基于^(14)C放射年龄,YSCW-1岩芯沉积物为9.3 ka以来的沉积,泥质沉积中心形成于约6.5 ka。粒度组成表明研究区沉积物主要由砂、粉砂和黏土组成。基于地球化学相关指标,研究区沉积物来源受到黄河和长江的影响。6.7 ka以前,黄河沉积物占据主导地位;6.7 ka之后长江对南黄海中部泥质区的贡献量增加,可能与黄海现代环流体系的形成有关,海洋锋面限制了黄河以及朝鲜河流沉积物向南黄海中部泥质区的输送。

Magnetostratigraphy of borehole EY02-2 in the southern Yellow Sea and its paleoenvironmental significance

Detailed rock magnetic and paleomag- netic studies have been undertaken on borehole EY02-2 (70m in length) in the southern Yellow Sea (SYS). The main Curie point revealed by magnetic susceptibility-temperature (k-T) curve is 580―600℃ indicating magnetite dominance. The hysteresis loop parameters show large variation of magnetic minera size in different sedimentary contexts: it is larger in subtidal sediment than in terrigenous sediment and even larger than in shallow sea sediment. This trend is correlative with distance to sediment source and dynamic strength. Magnetostratigraphic results show that the M/B polarity boundary (MBPB) is at 63.29m and there are at least 7 polarity transitions (Nr1-7) in Brunhes chron that can be tentatively correlated with 6 named polarity reversals. Three positive polarity reversals occur in late Matuyama chron and the early two may be the record of Kamikatsura happening in 886±3 kaB.P. Magnetic susceptibility (MS) and sediment grain size behave so differently in some sedimentary facies that certain big environmenta changes can be clearly revealed. Generally, the MS and grain size of subtidal and terrigenous sediments are larger than shallow sea sediments and MS value around 10×10?5SI and mean grain size of 7Φ seems to be indicators of shallow sea sediments of deep water depth. However, the frequently used excellen climatic proxies such as MS and grain size in loess and deep sea sediments fail to record such climatic cycles revealed by oxygen isotope in continental seaThe various sediment sources, sedimentation dy- namic and their complex changes between glacial and interglacial periods should be the cause of fail- ure.

南黄海中部MIS6期以来沉积物稀土元素组成及其物源指示意义

对南黄海中部SYSC-1孔0~30 m段岩芯稀土元素(REE)和粒度进行分析,结合年代测定,研究了沉积物REE组成特征及其影响因素,并对其物质来源变化进行了探讨。结果表明,∑REE含量为111.66~231.12μg/g,垂向分布变化较大,均值与中国黄土∑REE均值比较接近。∑REE与粒度变化有一定的相关性,但(La/Yb)N、(Gd/Yb)N和(δEu)N等参数受粒级影响较小。稀土元素分异参数有效示踪了物质来源,与周边河流对比发现,SYSC-1孔沉积物(La/Yb)N和(δEu)N散点图分布位置与黄河和长江较为一致,而与朝鲜半岛河流有明显不同。REE判别函数(DF)的物源区分结果表明,钻孔MIS6期经历了一次大的物源转换,沉积物由长江源(27.98~30 m)转为黄河源(24.24~27.98 m)。MIS5.5—MIS5.1期间(24.24~16.98 m)发育了浅水陆架冷水团沉积,主要是长江源细颗粒沉积物被古黄海暖流由南往北携带而来,并在冷涡区附近沉积下来。MIS5.1—MIS1期间(16.98~3 m)的低海平面时间较长,主要发育了一套滨浅海相-河口/潮坪相-三角洲相沉积,随着海平面急剧下降,陆架可容纳空间缩小,导致黄河、长江入海口向陆架区移动,黄河沉积物质控制了钻孔所处的南黄海北部区域。MIS1中晚期,山东半岛沿岸流的形成将黄河沉积物质主要控制在南黄海西部附近海域,而黄海暖流将济州岛西南部泥质区的长江源细颗粒物质搬运至SYSC-1孔附近的冷涡区沉积下来。总体来说,MIS6期以来南黄海中部海域沉积演化是西太平洋边缘海河海相互作用的一个典型范例,海平面波动和海洋环流变化在物源转换过程中发挥了重要作用。

北黄海BS24岩芯稀土元素地球化学与重矿物组成对北黄海晚全新世沉积演化过程的指示意义

北黄海泥质区具有地理位置独特、陆源物质供应丰富、沉积环境复杂等特点,为了更好地理解全球变化背景下对北黄海“源-汇”过程的影响,对北黄海泥质区边缘BS24岩芯沉积物进行了AMS14C测年、粒度、黏土粒级稀土元素和重矿物组成特征分析,以判识沉积物的来源、沉积环境特征,并进一步探讨北黄海的沉积演化过程。研究表明,BS24岩芯轻重稀土元素具有明显分异,稀土元素的球粒陨石标准化配分曲线右倾,轻稀土元素富集,重稀土元素亏损,上陆壳标准化的δEu和δCe无明显异常。稀土元素的变化趋势较为一致,以170 cm为界,上段波动幅度较大,下段含量相对稳定。岩芯中共鉴定出30种重矿物,以黑云母(37.46%)和自生黄铁矿(22.39%)最为常见,辉石和氧化铁矿物及不稳定矿物含量低。黏土粒级及极细砂组分特征指示,BS24岩芯晚全新世以来主要接受黄河物质的沉积。BS24岩芯自生黄铁矿含量的变化可能指示了北黄海冷水团强度的变化。650 cal. a BP以来,北黄海冷水团强度增强,自生黄铁矿含量降低;650~1 560 cal. a BP期间,研究区处于还原环境,北黄海冷水团强度减弱,营造的缺乏对流性环境为自生黄铁矿的富集提供了有利条件。

晚更新世以来南黄海中部进积体序列与古河流系统

通过高分辨率浅地层剖面声学地层与钻孔沉积地层的综合对比分析,系统研究了晚更新世以来南黄海中部海域的层序地层序列及其对海平面变化的响应。研究显示,基于高分辨率浅地层剖面自老至新划分的6个声学地层单元(U5、U4、U3、U2、U1-2、U1-1)与钻孔划分的沉积地层单元密切相关。MIS4期与末次冰盛期低海面时期发育的2个层序界面(R4、R2),将研究区晚更新世以来的层序地层自下而上划分为3个层序(SQ3、SQ2、SQ1),并识别出3期进积体序列与2期古河流系统。MIS5期与MIS3期高海面及海平面下降期间的2期东向进积体序列主要包括高位体系域与强制海退体系域,对应浅海—滨海沉积,厚度分别由西部的24 m与40 m向东明显变薄,而全新世高海面以来向海的进积体序列主要对应高位体系域,与长江源的浅海相泥质沉积相关,最大厚度超过16 m。研究区MIS4期和末次冰盛期发育的2期古河流系统与低位体系域相对应,最大沉积厚度分别超过36 m与24 m,均与长江及黄河密切相关,影响范围延伸至黄海槽及其以东海域,尤其末次冰盛期最远可达济州岛附近海域。

南黄海中部泥质区悬浮体颗粒组成及沉降

联合使用扫描电镜(SEM)和能量色散X射线光谱仪(EDX)的技术手段,对2012年春季采集的南黄海中部泥质区的悬浮体样品进行悬浮体颗粒结构和组成的系统观察,揭示研究区悬浮体类型、特征及空间分布,并首次发现了高温燃烧颗粒。结果表明:研究区悬浮体颗粒类型多样,包括碎屑矿物、自生矿物、生物碎屑、高温燃烧颗粒等单颗粒类型,其中高温燃烧颗粒以硅质或者铁质规则球状颗粒出现;同时发现了有机包膜体、矿物质絮团、矿物-生物碎屑絮团、矿物-有机包膜絮团以及矿物-生物碎屑-有机包膜复合絮团等絮团类型颗粒。实测结果表明,悬浮体颗粒粒径范围为0~500μm,主体集中在0~20μm,平均粒径为7.84μm,不同类型悬浮体粒径差别显著,其级配符合对数正态分布。该区悬浮体颗粒在水体中以递变悬浮方式搬运,能较长时间保留在水体之中。

南黄海中部泥质区黏性土的微结构特征及其成因分析

通过对南黄海中部泥质区27张黏性土微结构图片的分析,发现该区黏性土具有粒状链接结构、絮状链接结构和黏土基质结构三种微结构类型,以黏土基质结构为主。分别从地形特征、物质来源、水动力条件、沉积速率等宏观因素,以及粒度成分、矿物组成、化学成分等微观因素分析微结构的成因,得知平坦的海底地形、较弱的水动力条件、较长的搬运距离使得研究区沉积物来源较少,沉积速率较低,沉积物颗粒以粉粒和黏粒为主。伊利石、绿泥石和蒙脱石等黏土矿物和有机质含量较高,这些物质成分的亲水性特征使得研究区的黏性土易吸水膨胀,微结构类型以孔隙非常发育,结构极为疏松的黏土基质结构为主。研究成果揭示了南黄海中部泥质区黏性土宏观工程性质的微观机理,加深了对海洋沉积物工程性状的认识。