Distribution of Rare-earth Elements in the Shenzhen Bay and Dapeng Bay Modern Sediments

The aim of this paper is to study the REE geochemistry of the Shenzhen Bay (SZB) and Dapeng Bay(DPB) modern sediments, discuss their REE distribution patterns, reveal the REE geochemical difference between the two bays which share the same material source but are deposited in different sedimentary environments, and expound their dynamic changes.It can be concluded that the SZB and DPB sediments are essentially of continental source.Their REE distribution patterns are quite different from those of Pacific pelagic sediments, but are very similar to those of South Chi-na granites.Because of different sedimentary environments prevailing in the SZB and DPB, some REE fractionation would have taken place in the sediments of the two bays.

Carbon isotopic study of individual alcohol compounds in modern sediments from Nansha Islands sea area, China

Carbon isotopic compositions of individual n-alkanols and sterols in modern sediments from the Nan-sha Islands sea area are measured after derivatization to trimethylsilyl ethers by the new isotopic analytical technique of GC/C/IRMS. The effects of the three added silyl carbon atoms in every alcohol molecule on these compound isotopic compositions and the characteristics of their carbon isotopic compositions are studied. Then their biological sources are discussed using their carbon isotopic compositions.

Preliminary study on environmental magnetism of modern sediments in Kunming Lake and its implication

The study on global changes is an important international scientific program of IGBP organized by ICSU. It is also one of the most active programs in the area of natural sciences.Obviously, the study of global climate change in the past should be a focus of the modern scientific research. Its first task is to reconstruct historical sequences of climate. The research is not only the basis of knowing the climatic change in the past, but also the key to predict the climatic change trend in the coming 21st century. In the past two years, we have carried out some preliminary study of environmental magnetism by systematical sampling of modern sediments at a section in the Kunming Lake in the Sum-

Sulfur isotopic composition of modern seafloor hydrothermal sediment and its geological significance

A total of 1 264 sulfur isotopic values for modern seafloor hydrothermel sediments from different hydrothermal fields have been collected.On this basis,combining our sulfur isotpic data for surface hydrothermal sediments from the Jade hydrohtermal field in the Okinawa Trough and the TAG hydrothermal field in the Mid-Atlantic Ridge,respectively,and comparing the sulfur isotopic compositions and analyzing their sources of sulfur in seafloor hydrothermal sediments from different geologic-tectonic setting,the results show that:(1) sulfur isotopic values of sulfides and sulfates in modern seafloor hydrothermal sediments are concentrated in a narrow range,δ 34S values of sulfides vary from 1×10 -3 to 9×10 -3,with a mean of 4.5×10 -3 (n=1042),δ 34S values of sulfates vary from 19×10 -3 to 24×10 -3,with a mean of 21.3×10 -3(n=217);(2) comparing the sulfur isotopic compositions of hydrothermal sediments from the sediment-hosted hydrothermal fields,the range of sulfur isotopic values for hydrothermal sediments from the sediment-free hydrothermal fields is narrow relatively;(3) the differences of sulfur isotopic compositions in sulfides from different hydrothermal fields show the differences in the sources of sulfur.The sulfur of hydrothermal sulfides in the sediment-free mid-ocean ridges is mainly from mid- ocean ridge basalt,and partially from the reduced seawater sulfate,and it is the result of partially reduced seawater sulfate mixed with basaltic sulfur.In the sediment-hosted mid-ocean ridges and the back-arc basins,the volcanics,the sediments and the organic matters also can offer their sulfur for forming hydrothermal sulfides;(4)the variations of sulfur isotopic compositions and the different sources of sulfur for hydrothermal sediments may be attributed to the various physical-chemical characteristics of hydrothermal fluids,the magmatic evolution and the different geologic-tectonic settings of seafloor hydrothermal systems.

Determination of linear alkylbenzenesulfonates in modern sediments from core Zhu-9 and its significance

High performance liquid chromatography (HPLC) has the advantages of rapid analysis and high sensitivity. In the present study a suitable analytical condition has been established for HPLC, and the LAS in modern sediments from core Zhu-9 at the Pearl River mouth has been determined by HPLC. The concentrations of C12-LAS homologues are the highest. The sedimentation flux of C12-LAS was correlated with the average flow of the Xijiang and Beijiang rivers: the higher the flow rate, the larger the C12-LAS sedimentation flux. This shows that the more rapidly the river flows, the shorter the LAS will stay in freshwater, the less the extent of biodegradation, the larger the C12-LAS sedimentation flux in the core Zhu-9.

The sedimentary facies and dynamic environment of the Diaokou lobe in the modern Huanghe River Delta of China

The Huanghe River captures the Diaokou River in 1964 and forms a deltaic lobe in the subsequent 12 a. The progradational process of the Diaokou lobe is in associated with complicated evolution of riverine sheet flooding, merging, and swinging. On the basis of 11 borehole cores and 210 km high resolution seismic reflection data set, the sedimentary sequence and dynamic environment of the Diaokou lobe Cone subdelta lobe of the modern Huanghe River Delta） are studied. The stratigraphy of the lobe is characterized by an upward-coarsening ternary structure and forms a progradational deltaic clinoform. Totally six seismic surfaces are identifiable in seismic profiles, bounded six seismic units （SUs）. These SUs correspond to six depositional units （DUs） in the borehole cores, and among them, SUs 4-6 （DUs D to F） consist of the modern Diaokou lobe. Lithological and seismic evidences indicate that the delta plain part of the Diaokou lobe is comprised primarily by fluvial lag sediments together with sediments from sidebanks, overbanks, fluvial flood plains and levees, while the delta front part is a combination of river mouth bar sands （majority） and distal bar and deltaic margin sediments （minority）. As a result of the high sedimentation rate and weak hydrodynamic regime in the Huanghe River Delta, the sediments in the delta front are dominated by fine-grained materials. The grain size analysis indicates the Huanghe River hyperpycnal-concentrated flow shows the suspension, transportation and sedimentation characteristics of gravity flow, and the sediment transportation is primarily dominated by graded suspension, while uniform suspension and hydrostatic suspension are also observed in places. The strength of the hydrodynamic regime weakens gradually offshore from riverbed, river mouth bar, sidebank, distal bar subfacies to delta lateral margin and flooding plain subfacies.

典型海相砂质临滨坝沉积演化过程及成因机制

滩坝砂体是重要的油气储层,其形成的水动力机制复杂多变,受露头及现代沉积等资料的局限性影响,坝体的发育过程、几何形态、动态演化模式及构型叠置关系尚不明确。针对以上问题,利用沉积数值模拟与现代沉积相结合的方法,对典型正向线性临滨坝的沉积演化过程及成因机制进行了探讨。研究结果表明:典型海相临滨坝完整的发育阶段包括锥形坝形成期、弯月坝发育期、条带状复合坝形成期、条带状复合坝扩大生长期以及条带状复合坝停止发育期,现代沉积中可见不同发育阶段的坝体。不同演化阶段的坝体受向岸流、环流、沿岸流和底流等水动力控制。锥形坝及弯月坝为多个小规模、近等间距规则排列的坝体,受向岸流及沿岸环流不断冲刷,锥形坝演化为弯月坝。锥形坝及弯月坝间发育裂流凹槽,坝顶可发育回流沟槽,为典型的顶积式沉积过程。弯月坝坝体及坝间凹槽不断被沉积充填,形成相对整一的条带状复合坝,此阶段表现为典型的侧积式沉积过程。复合坝在向岸流及底流改造下变宽、变厚,最终出露水面形成障壁型滨岸。复合坝内部构型可由多个锥形坝、弯月坝及坝间凹槽构成,呈锥形坝-裂流凹槽-锥形坝或弯月坝-裂流凹槽-弯月坝的构型叠置关系,剖面上呈厚—薄—厚的叠置特征。

时间序列沉积物捕获器(sediment trap)及其在青海湖的放置

沉积物捕获器在认识现代沉积过程方面具有独特的优势,已在海洋和国外一些大湖的研究中得到了成功的应用,但相关的工作在我国湖泊研究中尚未开展。Mark 8-13型时间序列沉积物捕获器是用来连续收集水体沉降颗粒物的仪器,可以获得沉积物输入通量和季节性变率。本文在介绍了该类型沉积物捕获器的设计、工作原理、投放和回收等基本知识的基础上,阐明了我们选择青海湖作为放置沉积物捕获器的理由和科学意义。在本专题的五篇论文中,我们展示了在青海湖放置的沉积物捕获器于2010年7月至2012年9月期间收集的沉积物和湖水样品的研究结果和同步的实时监测数据。通过在青海湖两年多的试验性地放置以及初步的结果,我们建议在我国典型内陆不同位置的湖泊等水体长期地放置这类沉积物捕获器,将为湖泊等水体系统的现代沉积和生物过程的深入理解提供全新的视角。

现代河流沉积物碎屑及矿物组分研究新进展

现代河流沉积物忠实地记录了流域盆地内的母岩、风化、搬运和沉积过程中的化学、物理过程以及人类活动的改造作用,是探索和验证源-汇系统等理论的重要媒介。本文以全球现代河流砂组分数据库为基础,总结了碎屑组分、重矿物组分在不同大陆的分布特征,探讨了其在物源识别、源区贡献率计算、沉积物产生及搬运过程中气候-构造等影响因素的评估、对源-汇系统的研究启示等方面的应用。今后建议加强基于大数据的沉积物组分对气候-构造-人类活动的响应、沉积物产生及通量、高时间分辨率的沉积物组分变异性、不同物源定量化方法的差异等方面的研究。

玛纳斯湖滨岸带盐类和风成砂混合沉积特征及环境意义:来自物理模拟实验的启示

基于对玛纳斯湖现代沉积观察所获得的湖泊内砂岩为风成沉积的初步认识,在滨岸带盐类与风成砂混合沉积基本特征表述的基础上,结合物理模拟实验,分析了其成因过程,再现了风成砂与盐类的混合沉积形成过程,进一步对不同温度变化过程中的沉积差异进行探讨,揭示了盐类与风成砂的混合沉积形式能够反映气候变化。结果表明,温度影响盐类与风成砂混合沉积形式:①层状混合沉积:持续低温条件下(0~7℃),盐类晶体较粗厚度较大,与风成砂形成明显的韵律性层状混合沉积;②差异混合沉积:温度的连续变化(0~13℃)引起频繁的盐类在水面形成的薄膜状晶体在重力作用下崩塌,风成砂分布不均与盐类差异混合沉积。该认识为研究盐湖背景下混合沉积的形成机制提供了有价值的参考。

沣河西安段现代河流沉积特征及其沉积环境变化解译

本文对沣河西安段现代河流沉积体的岩石类型、沉积相类型、沉积模式及气候变化进行了综合研究,并对该地区现代河流体系的Google卫星影像、实地勘察、样品采集以及地球化学元素含量及其比值进行分析。结果表明,西安沣河现代沉积体岩性主要为土黄色泥岩、灰白色砂岩及泥质粉砂岩和少量的浅灰色细砾岩系;识别出3种亚相,即河道充填亚相、河道边缘亚相、泛滥盆地亚相;4种微相,即河床滞留沉积、点沙坝、河口扇和泛滥平原;在垂向上发育有3套不同的沉积层序:下部层序具有反韵律特征,中部和上部表现为明显的正韵律沉积,指示了水动力先增大再逐渐减弱的过程;通过分析沉积物中Co、Cr、Cu、Ni、Rb、Sr、V、Zn和Zr等微量元素含量的变化,以及锶铜法(Sr/Cu)、钒镍法(V/(V+Ni))、钒铬法(V/Cr)、镍钴法(Ni/Co)和锶钡法(Sr/Ba),确定沉积时期的环境主体为干旱气候,伴有季节性降雨,水体呈弱氧化-氧化性的淡水环境。

现代海洋沉积物X射线衍射全矿物分析方法

现代海洋沉积物中成分非常复杂,同时存在几种、十几种不同类型的矿物,将其进行全矿物分析在海洋地质学中有着重要的意义。X射线衍射(XRD)全矿物分析已成为海洋地质研究的通用方法。虽然XRD分析方法不断成熟和完善,但是一直没有一个统一的、放之四海而皆准的方法。该文介绍一种相对简单、快捷的XRD全矿物分析法,暂且称作强度因子法。普遍适用于现代海洋沉积物的物相定量分析方法,为现代海洋地质研究提供可靠的地质数据。

长江口-杭州湾毗连海区的现代沉积速率

运用沉积地层同位素2 10 Pb、13 7Cs测年技术 ,估算长江口 杭州湾毗连海区的现代沉积速率。研究结果表明 ,以泗礁水道为界 ,东侧的马鞍列岛区受外海高盐水的顶托 ,长江来沙少 ,淤积缓慢 ;西侧至长江口、杭州湾海岸交汇点 (南汇咀 )之间水域 ,是长江泥沙扩散南下的主要通道。其中 ,受长江冲淡水次级锋和杭州湾锋面输沙影响的湾口浅滩区 ,沉积速率约 3cm/a ;洋山港区 ,水深大于 2 0m的峡道区 ,受强动力作用而处于侵蚀状态 ,峡道两端出口的浅水区 ,沉积速率为0 .3～ 1.6cm/a ;马迹山港区 ,位于典型的峡道沿岸淤泥质陡坡 ,其沉积过程不稳定 ,正常沉积速率为 0 .7～ 3.4cm/a 。

现代浅水湖盆三角洲沉积砂体形态特征——以洞庭湖和鄱阳湖为例

以Google Earth提供的卫星照片平台为基础,对现代洞庭湖和鄱阳湖河口沉积进行了描述,分析了砂体发育特征。洞庭湖东、西湖区环境差异明显,发育5处规模较大三角洲,三角洲特征各异,其中西洞庭三角洲沉积砂体最为发育。潘阳湖基本东西分隔,以西部湖区沉积为主,特别是赣江三角洲砂体面积占整个湖区面积的7成以上。两湖中现代浅水三角洲砂体有两种展布形式,一种是连片展布砂体,主要发育于西洞庭和西潘阳湖中,尤以赣江三角洲最为典型,而另一种以枝状孤立砂体为特征,以东洞庭草尾-蒿竹河三角洲和潘阳湖西河三角洲为代表。前者三角洲平原发育,砂体连片分布,主体成因为分流砂坝。后者枝状、条带状分布,不具备广阔的平原相带,主体是天然堤沉积。通过对其成因分析认为其形成主要受控于河道推进过程中的沉积稳定程度,而这可能与河流的沉积物构成及水量相关。

新疆乌伦古湖的^(210)Pb、^(137)Cs测年与现代沉积速率

通过对乌伦古湖2个沉积柱样的210Pb和137Cs剖面的观测,运用210Pb过剩法和137Cs时标法估算了近几十年来的平均沉积速率。研究结果表明:210Pb过剩法的CRS模式测定的沉积速率的变化范围为0.018~0.071 g/(cm2.a),137Cs时标法测定沉积速率的变化范围为0.034~0.060 g/(cm2.a),两者具有较高的一致性。20世纪60年代以前,人类活动对本区影响相对较小,湖泊的沉积速率主要受自然因素的影响;20世纪60年代以后,随着乌伦古河中、下游农业的发展和调水工程的实现,人类活动逐渐成为主导湖泊演化的因素,从而影响乌伦古湖沉积速率。

多点地质统计学方法在三角洲前缘微相模拟中的应用

通过鄱阳湖三角洲现代沉积的研究确立水下分流河道与河口坝微相的平面形态与结构特征,结合永安镇油田密井网区资料统计的两种微相宽度建立定量的训练图像。以此为基础,利用多点地质统计学Sneisim算法进行三角洲前缘的微相模拟。模拟结果具有忠实于井点数据、不同微相平面形态与发育规模受训练图像定量约束的特点;能够再现三角洲前缘水下分流河道与河口坝的几何特征与空间结构。利用该方法可以建立反映现代沉积特征与地下实际情况的沉积微相模型。

现代风成沉积物磁化率各向异性与风向关系的研究

通过对风洞及室内模拟定向风条件下的风成沉积物磁化率各向异性与风向之间关系的研究，发现风成沉积物磁化率各向异性的长轴方向的偏角不仅与风向有关，而且与粉尘沉积量有关。风成沉积物磁化率各向异性的长轴方向的偏角在α95（α95≤20°）的区间范围内与粉尘沉积量大的风向一致．在干旱、半干旱区，现代风成沉积物（沙丘、黄土的表层土）的磁化率各向异性的长轴方向的偏角在此范围区间内与常年盛行风向一致，尤其与沉积物沉降时的盛行风向一致．

渤海湾曹妃甸潮汐汊道系统的现代沉积作用

利用渤海湾曹妃甸近岸海域22个表层样的粒度测试数据,5个柱状样的210Pb测定数据,同时结合多年海底地形断面对比,对曹妃甸海域潮汐汊道系统的现代沉积环境进行分析。结果表明,曹妃甸西部双龙河口表层沉积物从近岸到远岸有总体变细的趋势,2008年这一区域的沉积物与2006年相比有明显细化趋势。10年尺度上曹妃甸东部海域主潮流通道——老龙沟深槽的冲刷强度为21.3cm/a,冲刷强度不大,基本处于稳定状态。从百年尺度来看,曹妃甸沿岸潮滩与近岸浅滩的淤积速率大约在0.9～1.5cm/a之间。曹妃甸近岸河口区域底质沉积物的细化很大程度上是由于挖泥造成的,适当控制人类活动强度势在必行。老龙沟深槽的维持得益于研究区广阔的纳潮水域,在港口设计规划中自觉维持纳潮量关系到整个潮汐汊道系统的稳定性。

陆相盆地滩坝砂体沉积特征及其形成与保存条件——以青海湖现代沉积为例

滩坝砂体由于经历了湖浪作用的反复淘洗物性良好,成为近年来石油勘探界关注的热点.通过对我国最大的内陆湖泊(青海湖)现代沉积特征的实地考察,从沉积环境、水动力及沉积特征等诸多方面建立了滨岸滩坝沉积的综合鉴别特征,指出低角度冲洗交错层理、反粒序(滩)、正粒序(坝)以及不含泥质等特征是识别滩坝砂体的典型标志.分析结果表明:物源—水动力—湖盆底形—湖岸线—湖平面(基准面)是决定青海湖滩坝是否发育(形成+保存)的主控因素,其中物源为滩坝形成提供了物质基础,水动力为沉积物改造及滩坝形成提供了源动力,湖盆底形与湖岸线决定了滩坝形成的平面位置与规模范围,湖平面(基准面)的升降变化决定了已形成滩坝沉积保存与否的地质命运.陆源滩坝砂体的形成较为容易,但保存较难,只要具备物源、湖盆底形及水动力等基本条件,低位域、高位域及湖侵域都可能形成滩坝砂体,但只有位于长期基准面旋回早期或三级层序湖侵期的滩坝沉积才能得到较好的保存.这对我国陆相盆地岩性油气藏勘探开发具有一定借鉴意义.

北部湾现代沉积速率

运用210Pb法测定了北部湾16根柱样的现代沉积速率,结果显示北部湾柱样210 Pb剖面分布呈现三段式正常型、二段式正常型和倒置型3种类型,主要受沉积物组成、沉积物供应和水动力条件控制。北部湾东侧现代沉积速率相对较高的区域分布在钦州湾附近20m水深以浅的地区和涠洲岛至海南岛西岸一线外水深20～50m的内陆架。而在海南岛西岸水下岸坡带、琼州海峡西口附近和北部湾顶东北角这3处强潮区,现代沉积强度可能较弱或无现代细粒沉积。在北部湾中部50m水深以深,由于物质供应匮乏,现代沉积速率也极低。北部湾东侧存在由环流驱动的沉积物"传送带",自南向北运动,其西边界在琼州海峡一线以南是在50m等深线附近,以北是在109°E附近,冬季可能略向西拓展。