Geochemical and mineralogical evidence of tectonic and sedimentary factors controlling the origin of ferromanganese crusts associated to stratigraphic discontinuities (Betic Cordilleras, SE of Spain)     

Juan Jiménez-Millán  Luis M. Nieto 《Chemie der Erde / Geochemistry》2008,68(3):323-336

Ferromanganese crusts were found in carbonates of tectonostratigraphic units located in the northern and southern areas of the eastern External Subbetic of the Betic Cordilleras (SE Spain). The crusts are associated with four stratigraphic discontinuities of the Jurassic pelagic swells sequences: D1 (Late Carixian-Early Domerian), D2 (Middle Toarcian-Early Bajocian), D3 (Middle Bathonian-Middle Oxfordian), D4 (Early Tithonian-Late Albian). Two main textural types of crusts are distinguished. Type I crusts are thin and characterized by the presence of goethite, quartz, albite and phyllosilicates. Moreover, they show Si, Al, Mg, Na, Ti and K contents close to the European Shale Composite contents and Fe/Mn ratios (>350) higher than type II crusts. Type II crusts occur as thicker banded laminae and/or macrooncoids. They consist mainly of goethite and Mn-oxyhydroxides, which are enriched in REE, Co, Ni and Cu and show a strong Ce positive anomaly. After stratigraphical, mineralogical and geochemical data, the crust formation would be produced by the exposition of bottom sediments during long periods to a thin layer of oxidizing sea and porewater enriched in metallic elements. The textural and compositional variations between crusts can be explained by taking into account the bathymetric conditions. In shallower swells, the precipitation of a thick layer of banded type II crusts and in deeper areas, thin type I crusts were formed. Organic influence was only important in crusts from D3 of the northern area where textural evidence indicates the existence of seasonal periodically alternation between organism accretion and fine sedimentation. These were preceded and followed by phases in which the inorganic precipitation of oxides prevailed together with the fine sedimentation.  相似文献   

大亚湾海域锥状斯氏藻赤潮及其与孢囊的关系   总被引：22，自引：0，他引：22  

肖咏之  齐雨藻  王朝晖  吕颂辉 《海洋科学》2001,25(9):50-54

用沉积物捕捉器取样，研究了大亚湾海域２０００年６～９月孢囊（Ｃｙｓｔ）种群动态，同时 分析了浮游植物种群动态。研究期间（８～９月）该海域发生了一起大规模的锥状斯氏藻赤潮。 赤潮前一个月，锥状斯氏藻孢囊的平均日形成率为２．０５× １０５ｃｙｓｔｓ／（ｍ２·ｄ），丰度为５０．２２％， 该时期以有性生殖产生的静止期孢囊为主；在赤潮盛期的８，９月初，孢囊的平均日形成率达到 ２．０１ ×１０６ｃｙｓｔｓ／（ｍ２·ｄ），丰度为９６．９７％，此时期的孢囊多为营养细胞所形成的暂时性孢囊； 赤潮结束后，由于环境条件的恶化，暂时性孢囊的形成达到高峰，平均日形成率为１．２４×ｌ０７ ｃｙｓｔｓ／（ ｍ２·ｄ），丰度为９９.５３％。结果表明大亚湾丰富的孢囊是潜在的种源（Ｓｅｅｄ　ｂｅｄ），２０００年 的夏季、秋李持续高温（＞２５℃），台风减少及风力减弱等有利锥状斯氏藻的环境条件诱发孢 囊萌发，开始了该种类的赤潮。  相似文献   

The feasibility of escape mechanisms in conical snow crab traps     

Winger  Paul D.; Walsh  Philip J. 《ICES Journal of Marine Science》2007,64(8):1587-1591

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镇泾地区延长组河流相砂体分布与圈闭形成的关系研究   总被引：3，自引：1，他引：2  

张宗林  周文  苏付义 《矿物岩石》2008,28(4)

鄂尔多斯盆地镇泾地区侏罗系地层以三角洲-湖泊沉积体系为主,研究区范围内主要发育主河道和部分分流河道砂体。研究区构造平缓,主要为单斜地层、在东南部存在大型鼻状构造。通过对主要储层段(长6、8油层组)砂体分布及与构造之间关系进行研究,分析砂体走向与构造线方向的关系认为在构造单斜地区,当两者相交时(交角β≠0)是形成圈闭的关键因素之一,在大型鼻状构造地区因构造线的弯曲与河道砂体组合可以形成圈闭。根据研究区砂体分布和构造线组合出4种地层-岩性及岩性圈闭。利用构造图与砂体分布图对主要储层段存在的圈闭确定出长6、8油层组10个层圈闭。  相似文献   

Geologic Characteristics of Gas Reservoirs in West Sichuan Foreland Basin     

YANG Keming 《《地质学报》英文版》2008,82(6)

The foreland basin in West Sichuan is a tectonic unit that has undergone multi-periods tectonic movements of Indosinian-Yanshanian-Himalayan. Since late Triassic, it has been in a passive subsidence environment controlled by basin margin mountain systems and by the compression with abundant sediment sources. With the complex geologic setting, the main geologic characteristics of natural gas reservoir are listed as following:(1)Source rocks are coal-bearing mud and shale series with high to over maturity, and long and progressive hydrocarbon generation-displacement period. The key accumulation period is middle-late Yanshanian epoch.(2)There are three gas-bearing systems vertically, each of which has different reservoir mechanism, main-controlled factors and distribution law, so the exploration thoughts and techniques are also different.(3)Undergoing multi-period generation-migration-accumulation, oil and gas have encountered multi-period modification or destruction, and gas accumulation overpass multiple tectonic periods. So the trap type is complicated and dominated by combination traps. Because the main accumulation period of natural gas is early and the reservoir encountered the modification of strong Himalayan movement, there is great difference in the fullness degree of gas reservoirs and complicated gas-water relation. (4) Reservoir is tight to very tight, but reservoirs of relatively high quality developed under the super tight setting. (5) The key techniques for oil and gas exploration in west Sichuan foreland basin are the prediction of relatively favorable reservoirs, fractures and gas bearing; and the key techniques for oil and gas development are how to improve the penetration rate, reservoir protection and modification.  相似文献   

Numerical simulation of a stratigraphic model     

Véronique Gervais  Roland Masson 《Computational Geosciences》2008,12(2):163-179

A multi-lithology diffusive stratigraphic model is considered, which simulates at large scales in space and time the infill of sedimentary basins governed by the interaction between tectonics displacements, eustatic variations, sediment supply, and sediment transport laws. The model accounts for the mass conservation of each sediment lithology resulting in a mixed parabolic, hyperbolic system of partial differential equations (PDEs) for the lithology concentrations and the sediment thickness. It also takes into account a limit on the rock alteration velocity modeled as a unilaterality constraint. To obtain a robust, fast, and accurate simulation, fully and semi-implicit finite volume discre tization schemes are derived for which the existence of stable solutions is proved. Then, the set of nonlinear equations is solved using a Newton algorithm adapted to the unilaterality constraint, and preconditioning strategies are defined for the solution of the linear system at each Newton iteration. They are based on an algebraic approximate decoupling of the sediment thickness and the concentration variables as well as on a proper preconditioning of each variable. These algorithms are studied and compared in terms of robustness, scalability, and efficiency on two real basin test cases.  相似文献   

Seasonal Diatom Variability and Paleolimnological Inferences – A Case Study     

Dörte Köster  Reinhard Pienitz 《Journal of Paleolimnology》2006,35(2):395-416

The seasonality of physical, chemical, and biological water variables is a major characteristic of temperate, dimictic lakes. Yet, few investigations have considered the potential information that is encoded in seasonal dynamics with respect to the paleolimnological record. We used a one-year sequence of diatoms obtained from sediment traps and water samples, as well as the sedimentary diatom record covering the past ca. 1000 years in Bates Pond, Connecticut (USA), to investigate which variables influence the seasonal distribution of diatoms and how this can be used for the interpretation of the fossil record. The seasonal patterns in diatom assemblages were related to stratification and, to a lesser extent, to nitrate, silica, and phosphorus. During mixing periods in spring and autumn, both planktonic and benthic species were collected in the traps, while few lightly silicified, spindle-shaped planktonic diatoms dominated during thermal stratification in summer. Changes in fossil diatom assemblages reflected human activity in the watershed after European settlement and subsequent recovery in the 20th century. A long-term trend in diatom assemblage change initiated before European settlement was probably related to increased length of mixing periods during the Little Ice Age, indicated by the increase of taxa that presently grow during mixing periods and by application of a preliminary seasonal temperature model. We argue that the analysis of seasonal diatom dynamics in temperate lakes may provide important information for the refinement of paleolimnological interpretations. However, investigations of several lakes and years would be desirable in order to establish a more robust seasonal data set for the enhancement of paleolimnological interpretations.  相似文献   

迎接寒武系全球年代地层的新划分——2004年版“国际地层表”述评   总被引：9，自引：4，他引：9  

彭善池 《地层学杂志》2005,29(2):171-177,204

评述了国际地层委员会最新公布的2 0 0 4年版“国际地层表”的寒武系部分,包括它的底界全球层型和点位的确定和存在的问题、寒武系当前的再划分情况、芙蓉统和排碧阶及其底界全球层型剖面和点位、寒武系的时代跨度。介绍了全球寒武系年代地层的研究方向和正在表决中的全球寒武系最新划分方案。讨论了与我国寒武系年代地层的划分和建立地方性、区域性年代地层系统的相关问题  相似文献   

“国际地层表”与GSSP   总被引：11，自引：2，他引：11  

章森桂  严惠君 《地层学杂志》2005,29(2):188-204

近年来,“国际地层表”不断被国际地层委员会更新,用GSSP来定义年代地层单位而建立起来的“国际地层表”,使得大家在叙述地质历史时有一种共同的语言、有一个全球性的标准。在显生宇的96个阶(统)中已有4 6个阶(统)确立了GGSP,其余的有望在2 0 0 8年全部确立。我国已取得了4枚金钉子,即将取得3枚,还有可能再获得4—6枚。根据区域特点,我国已编制了“中国区域年代地层(地质年代)表”并正在开展区域性建阶工作  相似文献   

泌阳凹陷安棚油田深层系成岩作用研究及其在成岩圈闭预测中的应用   总被引：14，自引：2，他引：14  

金振奎  陈祥  明海慧  周新科  邹元荣  张响响 《沉积学报》2002,20(4):614-620

深层系一般指沉积盆地中埋藏深度在2 500～2 700 m以下的地层,其储集物性普遍很差,但在一定条件下,深部溶蚀作用可产生优质储层,形成成岩圈闭.然而这种成岩圈闭的预测一直是一个难题.安棚油田位于河南泌阳凹陷东南部,勘探成果表明,在该油田深层系下第三系核桃园组核三段下部(简称(核三下)席状的扇三角洲砂体中存在成岩圈闭.本次通过定量的成岩作用研究和成岩阶段划分,对成岩圈闭的形成机理和分布进行了探讨.研究表明,该区核三下的砂体经历了压实、胶结、溶蚀等多种成岩作用,不同的成岩作用发生于不同的埋藏深度.2 700～3 100 m之间以胶结强烈为特征,属于胶结带.3 100～3 900 m之间以次生溶蚀孔隙发育为特征,尤其是3 200～3 600 m之间, 属于深部溶蚀带.本区核三下砂体自南而北埋藏深度逐渐变浅,其上倾方向处于胶结带的部分由于强烈胶结而变成致密层,可封堵油气,而下倾方向处于溶蚀带的部分由于次生溶蚀孔隙发育而成为良好储层,从而形成成岩圈闭.根据不同埋藏深度、不同成岩阶段孔隙发育和保存的特征,可预测成岩圈闭分布。  相似文献