Development of northwest Pacific guyots: General results from Ocean Drilling Program legs 143 and 144   总被引：1，自引：0，他引：1  

Peter Flood 《Island Arc》1999,8(1):92-98

Results of the Ocean Drilling Program legs 143 and 144, which investigated the nature and origin of seven guyots in the northwest Pacific Ocean, document a history of prolonged volcanism (128–84 Ma), followed by subsidence, accumulation of shallow-water carbonates, emersion following a sea-level fall, then continued subsidence, and drowning. Generally, the life span of a guyot is of the order of 5–20 million years. The stratigraphic sequence in each guyot consists of 3–10 m-thick, shoaling-upward cycles, which display a 100-Ka periodicity perhaps related to sea-level fluctuations. The drilling results indicate that the demise of the shallow-water carbonate platforms is related to either a temporal (110–100 Ma) event or paleolatitude location (0–10°S) involving nutrient-rich water not conducive to production of calcium carbonate by shallow-water organisms. Following emergence and erosion, re-submergence occurred during a rise of sea-level. However, the rate of sediment accumulation was unable to keep pace with the rate of sea-level rise and the guyots drowned. Subsidence continued as the lithospheric plate cooled. The majority of guyots are now at ~ 1500 m below sea-level. Plate movements over the past 100 million years have carried the guyots from ~ 14°S to their current location in the northwest Pacific. Guyots are flat-topped submerged volcanic islands capped by thick sequences of shallow-water carbonates. The flat-top morphology is constructional, not related to wave planation as originally thought and reported in most textbooks.  相似文献   

麦哲伦海山区MA、MC海山玄武岩基岩的岩石学特征   总被引：3，自引：2，他引：1  

朱克超  李扬  赵祖斌 《海洋地质与第四纪地质》1999,19(4):84-19

麦哲伦海山区MA、MC海山玄武岩基岩的岩石学特征研究表明,岩性为蚀变玄武岩、橄榄玄武岩等;结构为基质具间隐、间往结构及拉斑玄武结构的斑状结构;矿物组成为斜长石、橄榄石、辉石及脱玻化玻璃等。按岩石化学成分分类属碱性玄武岩,而稀土分配模式属洋岛碱性玄武岩类型。  相似文献   

锥角对锥体结构抗冰性能影响的离散元分析   总被引：1，自引：1，他引：0  

龙雪  宋础  季顺迎  王跃方 《海洋工程》2018,36(6):92-100

在寒区海洋工程中,锥体海洋结构的尺寸参数对其破冰性能具有重要影响。采用具有黏结-破碎功能的离散元方法模拟海冰与锥体结构的相互作用过程中海冰的破坏模式及冰载荷分析。该离散元方法的计算参数通过与渤海油气平台的实测数据对比进行了可靠性验证。在此基础上,当设计海域的潮差固定时,对不同锥角下风电单桩锥体结构的冰载荷和海冰破坏模式进行了离散元分析。计算结果表明:锥体冰载荷随锥角的增大而增大,海冰的平均断裂长度则随锥角的增大而减小;当锥角小于70°时海冰的破碎模式主要为弯曲破坏,而当锥角大于70°时海冰破坏模式则主要为挤压破碎。以上研究结果可为冰区海上风电单桩结构的抗冰锥设计提供参考。  相似文献   

纵横加筋圆锥壳振动特性多变量分析     

王祖华  刘东  刘均 《海洋工程》2019,37(4):80-86

为了全面掌握纵横加筋圆锥壳结构参数与其振动特性之间的关系,采用有限元软件ANSYS对纵横加筋圆锥壳进行参数化建模,并基于设计变量全组合数据,采用相关性分析、主效应分析和主成分分析方法,对纵横加筋圆锥壳结构参数与结构第一阶总体弯曲模态频率、激励力处的加速度响应总级以及结构质量之间的关系进行研究,得到了各结构参数与目标量之间关系的定量描述。为正确理解纵横加筋圆锥壳结构参数与振动特征量之间的关系提供了数据支撑,同时为此类结构的工程设计提供了参考依据。  相似文献   

大洋海山及其生态环境特征研究进展   总被引：1，自引：0，他引：1  

马骏  宋金明  李学刚  李宁  王启栋 《海洋科学》2018,42(6):150-160

海山作为深海大洋独特地貌,尽管其研究可追溯到100多年前,但对大洋海山的形成、地质特征、动力学特性、生态环境等方面了解甚少。随着人们认识海洋程度的提升,特别是回声探测、无人潜水器和卫星技术等技术的应用,对大洋海山的系统探索已取得了前所未有的进展,大洋海山研究已成为当代人们所渴求探索的领域之一。本文对大洋海山的研究历程、分类、生物群落特征、水文环境特征以及维持海山区高生物量的机制进行了总结。目前全球海山主要有两种分类方式,其分类一是基于构造特征,可将海山分为板块内海山、大洋中脊海山和岛弧海山;二是基于山顶到海表面的距离,可将海山分为浅海山、中等深度海山和深海山。海山为生物提供了独特的栖息地,形成了高生物量、高生物多样性和高生物独有性等三种主要的生物群落特征,使海山成为世界海洋渔业的重点海域和生态环境研究的热点区域之一。海山突出的地形对大洋环流造成阻隔,因而在海山周围形成了其独特的水文环境,其中海山环流和上升流是其两种典型代表,这些独特的水文环境特征对生物群落的组成和分布具有重要影响。海山区的高生物量主要通过上升流输送、地形诱捕和海流水平输送三种机制维持,三种机制对支撑海山生态系统的物质循环和能量流动至关重要。  相似文献   

南海海岛海山的重磁响应特征   总被引：2，自引：0，他引：2       下载免费PDF全文

陈洁  朱本铎  温宁  万荣胜 《地球物理学报》2012,55(9):3152-3162

南海的海岛、海山等地貌单元的地球物理研究对于南海成因、海岛利用、资源问题和我国海防建设均具有重要意义.过去我国的南海海洋实际测量资料覆盖面小,且多数为测线调查,海底地形测量精度和重磁等测量精度较低,因此,一直无法得到精度较高的研究成果.本文利用半个多世纪我国在南海历年的多波束、重力、磁力等船载海洋实际地球物理调查资料,加上少数卫星、航空测量成果,得到能够覆盖南海全部海域的多波束、重力、磁力实际测量的地球物理基础数据.追溯南海周边的地磁台站与当年调查时间匹配的日变数据,重新校正历年磁力测量成果,并利用"十一五"863国家海洋高科技计划的处理、拼合技术,获得了南海海底地形、重力、磁力三方互为印证的可靠地球物理成果,为海岛海山的地球物理研究奠定基础.研究发现,南海海岛海山按其地球物理性质并结合现有的岩石物性资料,可以分为三大类:1)南海大部分海岛海山为空间重力异常值高、正磁力ΔZ_⊥异常值也高的高密度高磁性的双高海山,以基性喷出岩(玄武岩)为主;2)空间重力异常值高、磁力ΔZ_⊥异常值低的海山,以花岗岩、变质岩为主;3)空间重力异常值高、部分磁力ΔZ_⊥异常值高部分低的海山,可能是花岗岩、变质岩海山的部分区域出现火山喷发形成的. 海山的分布有规律,与南海的成因与南海块体的分异状态有关.  相似文献   

Frigate tuna Auxis thazard in New Zealand waters (note)     

P. E. Roberts  D. Eggleston  G. D. James 《新西兰海洋与淡水研究杂志》2013,47(1):163-167

Previous records of the frigate tuna Auxis thazard (Lacépède, 1802) were probably misidentifications of the slender tuna Allothunnus fallai. Frigate tuna were caught on the north‐east coast of New Zealand during 1975–76; the modal fork length of 176 specimens was 32–34 cm, and more detailed morpho‐metry and counts from 4 specimens are presented.  相似文献   

Quantifying the relative intensity of fishing on New Zealand seamounts     

Richard L. O'Driscoll  Malcolm R. Clark 《新西兰海洋与淡水研究杂志》2013,47(4):839-850

New Zealand seamounts support major fisheries for several deepwater fish species, including orange roughy (Hoplostethus atlanticus) and smooth oreo (Pseudocyttus maculatus). Although a high proportion of features in the depth range 500–1000 m have been fished, very little is known about the ecological impacts of bottom trawling on seamounts. The potential impact is likely to be influenced by the spatial extent and frequency of fishing. A new index is presented to assess the relative intensity of trawling on New Zealand seamounts. The fishing effects index (FEI) incorporates information on the density of fishing on the seamount as a proportion of the seabed area and also on tow direction. Detailed fisheries data from more than 250 000 tows were examined to calculate FEI for New Zealand seamounts. The most intensively fished seamounts were on the south Chatham Rise, an area characterised by a large number of relatively small features which were fished serially for orange roughy in the 1980s and 1990s. Other seamounts with high FEI were on the north Chatham Rise, Challenger Plateau, and off the east coast of the North Island. A range of sensitivity analyses indicated that the general rankings of seamounts were relatively robust to the choice of arbitrary thresholds used to assign tows to seamounts.  相似文献   

Contemporaneous multi-scale structures in the Montagne des Mémises (Préalpes du Chablais, Haute-Savoie, France)     

Anne Guyomard  Jean-Yves Josnin  Jean-Claude Hippolyte  Serge Fudral 《Swiss Journal of Geoscience》2009,102(1):3-14

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Digital Surface Development of Large Cylindrical and Conical Structures With a Single-Image Technique     

Iliana Theodoropoulou  Elli Petsa  & George E. Karras 《The Photogrammetric Record》2001,17(97):25-37

Normally, regular surfaces of architectural or archaeological interest can be accurately mapped with single-image techniques. Whenever possible, such surfaces are developed digitally, or they are presented as suitable cartographic projections. This paper describes the raster development of two large towers, one conical and one cylindrical, with heights of 19m and 12 m, and diameters of approximately 10m and 8m, respectively. The towers, dating from circa 300 BC, are situated on Greek islands and are accessible only on foot. The first tower was imaged from its surrounding hills with several lenses, including powerful telephoto lenses. The other tower was recorded from up to 9m above ground level by means of a modified fishing rod carrying a lightweight 35mm camera. All the non-metric photographs, taken at a negative scale of approximately 1:350 which allowed an overall accuracy of 3 cm to 4 cm to be achieved, were developed digitally and then mosaicked. The raster products are described and discussed.  相似文献