南海东部海域柱样沉积物浊流沉积探讨     

章伟艳  张富元  张霄宇 《热带海洋学报》2003,22(3):36-43

利用1998年南海东部陆坡69号柱样、深海盆149号柱样、南部岛礁323号柱样沉积物的粒度、化学、古生物、矿物等鉴定分析测试资料,分析了南海东部海域发生浊流沉积的地质背景、产生浊流沉积的条件和诱发因素,进而发现南海东部浊流沉积发育,在南北陆坡及中部深海盆地均有浊流沉积层。从其出现层位看,为氧同位素2—4期,即晚更新世中晚期。从浊流沉积出现层数分析,具有自北向南浊流发生频次减弱的趋势。从浊流沉积物成分看,南海东部浊流沉积物具有多样性,北部陆坡以陆源为主,中部深海盆以陆源及火山源为主,南部岛礁以生物源为主。  相似文献   

莺歌海盆地形成与演化的动力学机制   总被引：4，自引：0，他引：4  

孙向阳  任建业 《海洋地质与第四纪地质》2003,23(4):45-50

莺歌海盆地位于印支半岛与南海北部大陆边缘交接区,复杂的地质构造背景使其形成演化的动力学机制成为国内外的研究焦点。从区域动力学演化的角度,系统分析了影响莺歌海盆地发育的印支地块构造演化特征,认为莺歌海盆地构造演化主要受印支半岛早期的逃逸挤出构造和晚期的挤压-伸展构造系统影响(或控制),在此动力学驱动机制下,莺歌海盆地新生代以来的构造演化经历了3个阶段,即左旋走滑-伸展裂陷阶段、中下地壳韧性伸展-热沉降阶段和加速沉降阶段。  相似文献   

Determination of phospholipid fatty acid structures and stable carbon isotope compositions of deep-sea sediments of the Northwest Pacific, ODP site 1179   总被引：1，自引：0，他引：1  

Christopher T. Mills  Robert F. Dias  Dennis Graham  Kevin W. Mandernack   《Marine Chemistry》2006,98(2-4):197-209

Sediment samples ranging from 0.05 to 278 m below sea floor (mbsf) at a Northwest Pacific deep-water (5564 mbsl) site (ODP Leg 191, Site 1179) were analyzed for phospholipid fatty acids (PLFAs). Total PLFA concentrations decreased by a factor of three over the first meter of sediment and then decreased at a slower rate to approximately 30 mbsf. The sharp decrease over the first meter corresponds to the depth of nitrate and Mn(IV) reduction as indicated by pore water chemistry. PLFA-based cell numbers at site 1179 had a similar depth profile as that for Acridine orange direct cell counts previously made on ODP site 1149 sediments which have a similar water depth and lithology. The mole percentage of straight chain saturated PLFAs increases with depth, with a large shift between the 0.95 and 3.95 mbsf samples. PLFA stable carbon isotope ratios were determined for sediments from 0.05 to 4.53 mbsf and showed a general trend toward more depleted δ¹³C values with depth. Both of these observations may indicate a shift in the bacterial community with depth across the different redox zones inferred from pore water chemistry data. The PLFA 10me16:0, which has been attributed to the bacterial genera Desulfobacter in many marine sediments, showed the greatest isotopic depletion, decreasing from − 20 to − 35‰ over the first meter of sediment. Pore water chemistry suggested that sulfate reduction was absent or minimal over this same sediment interval. However, 10me16:0 has been shown to be produced by recently discovered anaerobic ammonium oxidizing (anammox) bacteria which are known chemoautotrophs. The increasing depletion in δ¹³C of 10me16:0 with the unusually lower concentration of ammonium and linear decrease of nitrate concentration is consistent with a scenario of anammox bacteria mediating the oxidation of ammonium via nitrite, an intermediate of nitrate reduction.  相似文献   

南沙群岛南永2井沉积层"红色事件"和"黑色事件"的成因探讨     

姚衍桃  詹文欢 《热带海洋学报》2006,25(6):39-46

南沙群岛南永2井的红色沉积层和黑色沉积层标志着两次异常事件,简称为“红色事件”和“黑色事件”。这两个特殊沉积层的主要特征是磁化率为正值、锰铝(黑色沉积)和铁铝(红色沉积)含量高。关于它们的成因主要有两种观点:一种是火山喷发或地震活动,另一种是气候突变。将红色沉积层和黑色沉积层与南海其它珊瑚礁钻井资料、南海及其周缘火山活动和深海沉积中的微玻陨石进行详细对比,并综合分析几种成因的可能性大小。“红色事件”和“黑色事件”在南海其它珊瑚礁钻井中的反映不明显或无反映,表明两事件的影响范围很有限。尽管南海周缘的一些火山活动期次、全球气候变化的一些代用指标和深海沉积中的微玻陨石层在时间上与“红”、“黑”两事件有较好的对比,成岩作用也能使某些沉积层位形成铁富集或锰富集,但综合考虑各个因素可以排除周缘火山喷发、气候突变、撞击事件及成岩作用等4种成因。火山或地震活动引起的铁或锰热泉上涌可以对“红”、“黑”两事件作出较好的解释,是可能性较大的成因。  相似文献   

海底柱状沉积物超声测量   总被引：10，自引：0，他引：10  

周建平  吕文正  陶春辉 《海洋学研究》2003,21(4):26-33

运用RS-ST01C超声测试仪,对32个海底沉积物柱状样品进行了现场超声波声学测量,并作了声速剖面初步分析,结果表明,样品及其固定方法、耦合剂、t0值、生物含量、取样效果和频率等因素对测量的结果均有一定影响,其中,样品及其固定方法、t0值、生物含量以及取样效果对声速测量的结果影响较大,而耦合剂和频率等因素对其影响较小。  相似文献   

Structure of Subsurface Intrusion of the Oyashio Water into the Kuroshio Extension and Formation Process of the North Pacific Intermediate Water     

Kuniaki Okuda  Ichiro Yasuda  Yutaka Hiroe  Yugo Shimizu 《Journal of Oceanography》2001,57(2):121-140

In order to understand the actual formation process of the North Pacific Intermediate Water (NPIW), structure of subsurface intrusions of the Oyashio water and the mixing of the Oyashio and the Kuroshio waters in and around the Kuroshio Extension (KE) were examined on the basis of a synoptic CTD observation carried out in May-June 1992. The fresh Oyashio water in the south of Hokkaido was transported into KE region through the Mixed Water Region (MWR) in the form of subsurface intrusions along two main paths. The one was along the east coast of northern Japan through the First Branch of the Oyashio (FBO) and the other along the eastern face of a warm streamer which connected KE with a warm core ring through the Second Branch of the Oyashio (SBO). The fresh Oyashio water extended southward through FBO strongly mixed with the saline NPIW transported by the Kuroshio in the south of Japan (old NPIW) in and around the warm streamer. On the other hand, the one through SBO well preserved its original properties and extended eastward beyond 150°E along KE with a form of rather narrow band. The intrusion ejected Oyashio water lens with a diameter of 50–60 km southward across KE axis and split northward into the MWR involved in the interaction of KE and a warm core ring, which were supposed to be primary processes of new NPIW formation.  相似文献   

利用钻芯孔检测灌注桩钢筋笼长度的方法     

樊敬亮  董平  叶景艳  李明  朱国伟 《物探与化探》2008,32(3):335-337

根据充电法原理,结合模型桩试验,分析了钢筋笼周围的充电电场特征,结果表明钢筋笼的底端对应于电位梯度曲线的极小值点及电位曲线的拐点。以此研究结果为基础,提出了利用钻芯孔来检测成桩后钢筋笼长度的方法。某桥的应用表明,该方法简便、实用、可靠。  相似文献   

Palaeolimnological studies of the eutrophication of volcanic Lake Albano (Central Italy)     

Andrea Lami  Frank Niessen  Piero Guilizzoni  Julieta Masaferro  Claudio A. Belis 《Journal of Paleolimnology》1994,10(3):181-197

We use palaeolimnological techniques to reconstruct the eutrophication history of a volcanic lake (Lake Albano, central Italy) over the past three centuries. The presence of annual varves down to the bottom of the core (c. 1700 A.D.) indicated the lack of bioturbation and likely long-term meromixis. Sedimentation rates were estimated by varve counts (calcite/diatom couplets), indicating a mean rate of 0.15 cm yr^–1. The reconstruction of eutrophication was traced using past populations of algal and photosynthetic bacteria (through their fossil pigment), and geochemistry, as well as fossil remains of chironomids. Phaeophorbidea and the red carotenoid astaxanthin were used to detect past zooplankton development.The first sign of trophic change related to human activities is datedc. 1870 A.D. From that period onward a sharp increase of authigenic CaCO₃, nitrogen, N:P ratio, and dinoxanthin, a characteristic carotenoid of Chrysophyceae and Dinophyceae, is observed.Chironomid analyses showed the near absence of a deep water fauna throughout the core length. The populations of chironomid larvae are restricted to oxygenated littoral zones. In fact, the few fossil remains found are primarily of littoral origin, representing shallow water midges that were transported to profundal waters. The reduction of total chironomid in the uppermost layers of the core is to be related to human land uses.  相似文献   

豫西后造山阶段存在变质核杂岩吗？   总被引：2，自引：1，他引：1  

曹高社  赵太平 《地质论评》1997,43(4):365-372

不少学者用变质核杂岩模式解释豫西造山阶段基底隆起和与之相伴的盆岭构造的构造格局。介一本区基底隆起的形态、机制、时限和地壳剥露层次均没有变质核杂岩特征与基底隆起相伴的断陷人舅地也不同于变质核杂岩模式中的半地堑。  相似文献   

Research on temporal and spatial distribution, evolutionary character and mechanism of crustal deformation field before and after the Tangshan earthquake   总被引：2，自引：0，他引：2  

周硕愚  施顺英  帅平 《地震学报(英文版)》1997,10(6):693-701

Ｒｅｓｅａｒｃｈｏｎｔｅｍｐｏｒａｌａｎｄｓｐａｔｉａｌｄｉｓｔｒｉｂｕ┐ｔｉｏｎ,ｅｖｏｌｕｔｉｏｎａｒｙｃｈａｒａｃｔｅｒａｎｄｍｅｃｈａｎｉｓｍｏｆｃｒｕｓｔａｌｄｅｆｏｒｍａｔｉｏｎｆｉｅｌｄｂｅｆｏｒｅａｎｄａｆｔｅｒｔｈｅＴａｎｇｓｈａｎ...  相似文献