基于古地磁与~(230)Th定年的西沙西科1井乐东组生物礁沉积年代的初步研究          下载免费PDF全文

王振峰  张道军  刘新宇  尤丽  罗威  易亮  谭亮成  祝幼华  秦华峰  程海  李忠权  谢强  车志伟  邓成龙  朱日祥 《地球物理学报》2017,60(3):1027-1038

生物礁是重要的自然资源,在全球气候变化与碳循环中扮演了重要角色.磁性地层学是建立年代框架的有效手段,但是,由于生物礁沉积物中天然剩磁强度弱,南海地区生物礁的磁性地层学研究尚未很好展开.为此,本文利用西沙群岛西科1井乐东组生物礁沉积样品进行了详细的岩石磁学和磁性地层学研究.结果显示,西沙群岛乐东组记录了布容正极性时、奥杜维尔正极性时和松山负极性时.通过对比已有的钻孔资料,本文认为应基于岩石地层特征这一标准将西沙地区的乐东组埋深予以统一.在此基础上,综合磁性地层与~(230)Th定年结果,本文将乐东组的底界限定在~2.0 Ma.  相似文献   

In.uence of particle composition on thorium scavenging in the marginal China seas     

YANG Weifeng  CHEN Min  .  CAO Jianping  QIU Yusheng  ZHANG Run  MA Qiang  TONG Jinlu  YANG Junhong  YANG Zhi  L U E 《海洋学报(英文版)》2009,(2):45-53

Thorium-234 and particle composition (organic matter, biogenic silica, carbonate and lithogenic component) were examined in the East China Sea (ECS) and the northern South China Sea (NSCS) in order to constrain the particle types scavenging thorium isotopes. Good positive correlations between particulate organic matter (POM) or carbonate and thorium-234 in suspended particulate matter (SPM) indicates that POM and carbonate are e.cient to scavenge thorium-234. No relationship between biogenic silica and thorium-234 suggests that geochemical behavior of thorium-234 may be not in.uenced by biogenic silica. A simple model was used to evaluate the a.nity of thorium-234 to di.erent particle components. The results show that POM is the most e.cient scavenger for thorium-234 in the ECS and the NSCS, followed by carbonate. The authors’ results lend support to the utility of thorium-234 as a proxy of POC and carbonate in the upper layer. However, the strong dependence of thorium scavenging on particle composition challenges thorium-230 as a constant .ux proxy.  相似文献   

冬季南海北部陆架锋区悬浮颗粒态硅的分析冬季南海北部陆架锋区悬浮颗粒态硅的分析     

鲁超  刘素美  任景玲  陈琪  罗忻  李健兵  张经 《海洋学报(英文版)》2009,28(5)

对冬季南海北部陆架锋区的悬浮颗粒态生物硅（Particulate Biogenic Silica, PBSi）和成岩硅（Lithogenic Silica, LSi）含量进行了调查分析,讨论了悬浮颗粒态生物硅分布及其影响因素。结果表明,南海北部陆架区悬浮颗粒态生物硅和成岩硅平均含量分别为059和893 μmol/dm3。生物硅分布与水团关系密切：在营养盐充足的沿岸水生物硅含量高（10 μmol/dm3）;而在营养盐缺乏的陆架表层水生物硅含量低（023 μmol/dm3）;在两种水团过渡区生物硅含量居中（065 μmol/dm3）并与溶解硅酸盐（Dissolved Silicate, DSi）成显著正相关（R=048,N=44,P=0001,a=001）。此外锋面位置也直接影响生物硅的含量与分布。大部分调查海区被高温高盐低营养盐海水占据,因此导致了调查海区以低浓度的生物硅和成岩硅为特征,且与世界其他海区相比,生物硅含量处于低值区。  相似文献   

The biogenic gas potential of the submarine canyon systems of Plio-Peistocene foreland Basin,southwestern Taiwan     

Shi-Chie Fuh  Chir-Cherng Chern  Shov-Chian Liang  Yu-Liang Yang  Suh-Huey Wu  Tzy-Yi Chang  Jen-Yang Lin 《Marine and Petroleum Geology》2009

Biogenic gas was accidentally discovered and produced from the Plio/Pleistocene formation of the Hsinying gas field in southwestern Taiwan in 1989. A stratigraphic trapping mechanism related to the evolution of submarine canyon systems in the Plio-Peistocene foreland basin has been proposed in a previous study which explained underestimated recoverable gas reserve before drilling. To verify this shallow gas exploration hypothesis and to systematically evaluate the biogenic gas generation and entrapment potential of the submarine canyon systems, seismic interpretation, high-resolution sequence stratigraphic interpretation, seismic attribute analysis and geochemical analysis were performed and integrated in this study. Twenty-nine submarine canyons mapped mainly trend in a NE direction, except the NW trending Eurchungchi submarine canyons located near the Chiali paleo-high. Bright seismic amplitudes were often observed at the incised valley heads of the canyon systems. The shales located near the incised valley heads and deposited during flooding stage possess the highest biogenic gas generation potential, as canyon fill reveals the second highest. Due to the high sediment accumulation rate in the foreland basin, organic matter in such a depositional environment tends to become diluted. A Class III AVO anomaly, inverted impedance lower than 4.7 e + 6 kg/M³*M/S and A/B (the ratio between the target horizon amplitude and the RMS amplitude from the background strata) greater than 1.78 were identified as valid direct gas indicators as sand is buried shallower than 1000 m. Class IV AVO anomaly and A/B greater than 1.4 were concluded to be the indicators of gas sand in the case that sand is buried deeper than 1600 m. Based on the results of sequence stratigraphic interpretation and the consistency between spatial geometries of seismic attributes and those of the submarine canyons, a stratigraphic trap associated with the incised valley heads was concluded to be the original gas entrapment style of the Hsinying and the Kuantian gas fields. Biogenic gas migrated after being trapped startigraphically, hence contributing to the present-day gas field structure. Due to the prevalent erosional features of the submarine canyons on the time structural maps, different types of stratigraphic traps formed in combination with faults and submarine canyons can be recognized easily.  相似文献   

长江水下三角洲现代沉积速率厘定的新途径:季节性Bio-Si记录     

范德江  齐红艳  孙晓霞  郭志刚  杨作升 《中国海洋大学学报(自然科学版)》2009,39(5)

长江水下三角洲沉积层中高分辨生物硅(Bio-Si)曲线具有明显的波动规律,记录了该区硅藻生物量的季节性差异,据此对近14年来的沉积速率进行了估算。在1992～2005年里,该处沉积速率变化于1.2～3.4 cm/a之间,平均沉积速率2.1 cm/a,沉积速率与长江入海沙量具有较好的对应关系。研究结果表明长江水下三角洲Bio-Si沉积记录类似于季节性湖泊中的"年纹",可作为沉积速率估算的新指标。  相似文献   

黄海冷水域生源要素的变化特征及相互关系   总被引：33，自引：8，他引：33  

王保栋 《海洋学报》2000,22(6):47-54

根据“中韩黄海水循环及物质通量合作研究”项目的现场调查资料,对黄海冷水域生源要素的分布变化特征及其相互关系进行了探讨。结果表明,黄海冷水团存在期间,上层水体中的营养盐由于浮游植物的摄取而几乎被耗尽,但在密度跃层以下因有机物分解使营养盐再生而逐步累积。溶解氧、pH和叶绿素a的层化现象亦十分明显,并在中层(20～30m)形成最大值层。生源要素断面分布中等值线的起伏趋势或马鞍形形态表明,黄海冷水团中的垂直环流存在将底层冷水向上扩散的趋势。此外,对影响生源要素的含量、分布及其季节变化的因素,以及生源要素之间的相互关系进行了分析探讨。  相似文献   

长江口生物硅的组成、行为和收支     

冉祥滨  刘军  刘森  臧家业  王保栋  赵军 《海洋学报(英文版)》2018,37(1):60-72

基于在长江口开展的三个综合航次对河口生物硅组成、行为和收支进行了研究。结果表明,长江口生物硅主要是由植硅体、硅藻和海绵骨针三部分组成,其中植硅体有16种形态,在高混浊区对生物硅的贡献量为23%-83%。收支计算显示,长江输送的生物硅是河口区获取外部生物硅的主要途径,占河口生物硅总输入量的95%;维持河口生物硅水平的主要过程是初级生产（55 Gmol a^-1）和沉积过程（46 Gmol a^-1）;初级生产所贡献的生物硅分别是长江生物硅输送量的2.3倍和河口区向外输送生物硅的63%。从河口区向东海和黄海输送的生物硅是26 Gmol a^-1,与长江的生物硅输送量相当;河口区沉积的生物硅是向外输送量的1.7倍,在其中植硅体贡献了53%至88%的生物硅,表明河口是陆源生物硅汇的作用;反风化作用也是河口活性硅去除的一个重要途径。本研究显示植硅体是河口生物硅的重要组成部分,长江口在生物硅收支与循环中表现出汇的作用。  相似文献   

The diffusion coefficient of dissolved silica revisited   总被引：1，自引：0，他引：1  

Laura Rebreanu  Jean-Pierre Vanderborght  Lei Chou   《Marine Chemistry》2008,112(3-4):230-233

The diffusion coefficient of dissolved silica was determined for two different salinities, 36 and 0, at temperatures ranging from 2 °C to 30 °C and at an average pH value of 8.1. Our results show limited influence of salinity and a variation by a factor of 2 to 3 of the silica diffusion coefficient within the temperature range considered in this study. The values obtained at 25 °C are in agreement with previous work carried out at room temperature for seawater and freshwater. The dependency on temperature and viscosity of the diffusion coefficient agrees well with the Einstein–Stokes equation. The composition of the solvent appears to be an important factor because it modifies the viscosity and allows for the complexation of the dissolved silica with less mobile ions, while its pH controls the dissolved silica speciation. In seawater, the higher viscosity and the presence of dissociated and polymeric species result in a decrease of the diffusion coefficient compared to freshwater systems.  相似文献   

Effect of solid to solution ratio on biogenic silica determination in coastal sediments     

Nattapong Loassachan  Kuninao Tada 《Journal of Oceanography》2008,64(5):657-662

The method of DeMaster (1981) for measuring biogenic silica (BSi) in marine sediments was modified. We found a considerable effect of the solid to solution (S/S) ratio on BSi determination in coastal sediments. The BSi contents determined by DeMaster’s method were overestimated due to the contribution of clay mineral-derived extractable Si at a low S/S ratio (<1 g l⁻¹), and incomplete recovery of BSi was observed due to incomplete extraction when using a high S/S ratio (>2 g l⁻¹). For BSi analysis of coastal sediment samples, the BSi content of representative samples must be measured using various S/S ratios to determine the appropriate S/S ratio in order to minimize the contribution of extractable Si derived from clay minerals and to obtain sufficiently efficient extraction with 1% Na₂CO₃ before actual sample measurement. One way to determine the appropriate S/S ratio is to use artificial sediment which has a theoretical Si and clay mineral content similar to the sediment sample composition. Using artificial sediment, the S/S ratio of 2 g l⁻¹ seems appropriate for measuring the BSi content of the coastal sediments investigated in this study, because 99.6% recovery can be achieved.  相似文献   

天池天文峰全新世火山喷发物长石表面硅膜特征及意义     

张秉良 《地质学报》2011,85(6):947-954

利用扫描电镜和能谱分析研究天池火山天文峰剖面全新世喷发物中长石表面硅膜的结构状态和化学组成,结果显示:天文峰剖面从顶部黑色浮岩向下到暗灰色浮岩中,长石表面发育有不同结构状态的硅膜.硅膜的结构特征有随火山喷发时代越早,长石颗粒表面硅膜越厚,结构越复杂;喷发时代越晚,长石颗粒表面硅膜越薄,其结构越简单的变化趋势,即长石表面...  相似文献