柴达木盆地咸湖相生油岩正构烷烃分布特征及其成因   总被引：25，自引：3，他引：25  

朱扬明  苏爱国  梁狄刚  程克明  翁焕新  彭德华 《地球化学》2003,32(2):117-123

柴达木盆地西部第三系咸水湖相生油岩样品分析资料表明，不同沉积相带生油岩正构烷烃系列有三种碳数分布模式。深湖相生油岩在C18－C28范围呈明显的偶碳数优势，而＞C28范围无碳数优势；滨浅湖相样品在整个碳数范围内呈奇碳数优势分布；过渡相带地层正构烷烃在中碳数范围呈偶碳数优势分布，而高碳数（＞C23）部分为奇碳数优势分布。经不同沉积相带样品之间的沉积环境地球化学指标和碳酸盐含量比较发现，本区咸湖相生油岩正构烷烃的分布不取决于沉积环境的氧化还原性和岩石的矿物组成，而主要与沉积相带中的有机质生源组成有关。偶碳数优势分布的正构烷烃成因并非如常规观点解释的那样，由正构脂肪酸、醇类的还原作用或经碳酸盐催化发生β断裂而来，而可能来源于咸化湖泊中的某种嗜盐细菌或其他微生物。  相似文献   

对《西藏高原雅鲁藏布江北岸蛇绿岩带的发现及其地质意义》一文的商榷   总被引：6，自引：2，他引：6  

李才　夏代祥  王义昭  雍永源  郑海翔周　详刘鸿飞蒋光武万永文胡敬仁 《地质通报》2003,22(1):57-59

综合1：5万区调成果，系统阐述了赣西北地区双桥山群的沉积学特征，认为是一套形成于滨海－半深海环境的重力流沉积体系，基本发育－系列重力流沉积相单元，即块状混杂砾岩相，正递变砾岩相，经典浊积岩相等，对各单元基本层序特征进行了总结论述，并结合地球化学特征及粒度分析成果探讨了沉积环境。  相似文献   

江苏海岸潮滩沉积环境及其可持续利用问题   总被引：2，自引：1，他引：2  

李杨帆  朱晓东 《江苏地质》2003,27(4):203-206

凭借着独一无二的地质、地貌、海洋、气候、土壤和生态特征，江苏潮滩拥有丰富的自然资源，然而却又受着不利自然条件及不合理人类活动的限制。江苏潮滩沉积表现出4个水平相带：草滩(湿地)沉积带、盐蒿泥滩沉积带、泥一砂混和滩沉积带、粉砂滩沉积带。潮滩是极为脆弱的生态系统，它极容易受到湿地围垦、低效的生产方式、酷取滥采、环境污染等人类扰动的破坏。基于以上认识，提出顺应潮滩自然演变，人类活动与潮滩沉积环境的和谐开发利用及保护模式。  相似文献   

Controls of facies and sediment composition on the diagenetic pathway of shallow-water Heterozoan carbonates: the Oligocene of the Maltese Islands   总被引：1，自引：0，他引：1  

Andrea C. Knoerich  Maria Mutti 《International Journal of Earth Sciences》2003,92(4):494-510

Relatively few studies have so far addressed diagenetic processes in Heterozoan carbonates and the role that sediment composition and depositional facies exert over diagenetic pathways. This paper presents a study of Oligocene shallow-water, Heterozoan carbonates from the Maltese Islands. We investigate stratigraphic distribution, abundance and timing of diagenetic features and their relationship to sediment composition and depositional facies. The studied carbonate rocks comprise rud- to packstones of the Heterozoan association predominantly containing coralline red algae, bryozoans, echinoids and benthic foraminifers. XRD analyses show that all high-Mg calcite has been transformed to low-Mg calcite and that no aragonite is preserved. Diagenetic processes include dissolution of aragonitic biota, neomorphism of high-Mg calcitic biota to low-Mg calcite and cementation by fibrous, bladed, epitaxial and blocky cements. Stable isotopes on bulk rock integrated with petrographic data suggest that the study interval was not exposed to significant meteoric diagenesis. We interpret early cementation to have taken place in the marine and marine burial environment. The distribution and abundance of early diagenetic features, determining the diagenetic pathway, can be related to the primary sediment composition and depositional texture. Sorting and micrite content are important controls over the abundance of diagenetic features.  相似文献   

Lateral variations in sediment composition and bedding in Middle Triassic interplatform basins (Buchenstein Formation, southern Alps, Italy)     

Florian Maurer  Wolfgang Schlager 《Sedimentology》2003,50(1):1-22

ABSTRACT Hemipelagic deposits are widespread in Triassic sequences of the Alpine belt and provide important data for stratigraphy and the study of bedding rhythms. The area of the western and central Dolomites of northern Italy escaped strong alpidic deformation and preserves such deposits in their original palaeogeographic setting. The Buchenstein Formation, the object of this study, was deposited in up to 1000 m deep, Middle Triassic interplatform basins, which extend over an area of 500 km² within the Dolomites. Excellent outcrops and volcaniclastic markers allow a detailed correlation of the formation in both laminated (anoxic) and bioturbated facies down to a bed scale, and show its relationship to coeval carbonate platforms. Correlation of lithostratigraphically well‐constrained intervals in the bioturbated facies reveal that lateral thickening and thinning of the deposits depends on the amount of shallow‐water debris in the succession and is a function of the distance to coeval carbonate platform sources. In the laminated background deposit, thickness variations in limestones and marls parallel the thickness variations in ash layers, and were caused by local redeposition of sediment on the basin floor. Lateral persistence of laminae indicates that bottom currents were weak in the Buchenstein basin, but were able to redeposit mud in a significant way. In the area around Seceda and Geisler (western Dolomites), a lateral transition from dark‐grey laminated to grey bioturbated to red bioturbated facies is observed, which is probably linked to local relief with different oxygenation conditions on the sea floor. A comparison shows that decimetre‐scale bedding is preserved in all facies types and that the bedding rhythm is partly the result of different cementation of the sediment during early diagenesis. Correlation of individual layers in the bioturbated facies reveals that beds are thicker and enriched in lime mud in the western part of the basin, and decrease in thickness and contain less micrite towards the east, further away from the main shallow‐water areas. Nearslope calciturbidites change gradually from distinct layers into lateral arrays of micrite nodules and bands further out in the basin. These observations point to a platform source of lime mud in the Buchenstein basin.  相似文献   

地层基准面研究概述   总被引：2，自引：0，他引：2       下载免费PDF全文

刘豪  王英民  王媛 《沉积与特提斯地质》2003,23(2):98-104

根据研究目的和内容的差异，形成了基准面研究的两个派别——地貌基准面和地层基准面。基准面的一个升降周期形成了一个基准面旋回，这种基准面旋回性导致了该旋回周期的特有岩石地层单元；而在不同的地质历史中，基准面旋回级别不一样，形成了不同级别的基准面旋回，控制了不同级别岩石地层单元的记录特征。同时在一个基准面升降旋回过程中，决定了沉积可容空间的大小，进而控制了沉积物的叠置模式。但基准面的形成和控制因素亟需进一步深入研究。  相似文献   

准噶尔盆地吉木萨尔凹陷中-上二叠统沉积相特征   总被引：3，自引：0，他引：3  

张健  刘楼军  黄芸  王军  胡斌 《新疆地质》2003,21(4):412-414

准噶尔盆地东部吉木萨尔凹陷中-上二叠统由上芨芨槽子群、泉子街组、梧桐沟组组成．凹陷内中-上二叠统经历了低水位域→高水位域→低水位域的变化过程，其有利相带以扇三角洲和三角洲相为主，主要发育于东斜坡区的东北部及东南部以及凹陷南北两侧断裂下盘，在南北局部的乌拉泊组和梧桐沟组还发育浊积扇．油气显示集中于三角洲或扇三角洲相带内(芦草沟组、梧桐沟组)，凹陷腹部深湖-半深湖相内的扇三角洲和三角洲沉积区是凹陷内油气的最有利聚集区和保存区．  相似文献   

Provenance, environmental and paleogeographic controls on sandstone composition in an incised-valley system: the Eocene La Meseta Formation, Seymour Island, Antarctica     

Sergio A. Marenssi  Laura I. Net  Sergio N. Santillana 《Sedimentary Geology》2002,150(3-4):301-321

The Eocene La Meseta Formation is the youngest exposed unit of the back-arc James Ross Basin, Antarctic Peninsula, cropping out in Seymour (Marambio) Island. The formation comprises 720 m of clastic sedimentary rocks of deltaic, estuarine and shallow marine origin. It was subdivided into six unconformity-based units (Valle de Las Focas, Acantilados, Campamento, Cucullaea I, Cucullaea II and Submeseta Allomembers) grouped into three main facies associations. Facies association I represents valley-confined deposition in a progradational/aggradational tide-dominated and wave-influenced delta front/delta plain environment. Facies association II includes tidal channels, mixed tidal flats, tidal inlets and deltas, washover and beach environments. Facies association III represents nonconfined tide- and storm-influenced nearshore environments. La Meseta Formation sandstones are quartzofeldspathic with some hybrid arenites (glauconite and carbonate bioclasts-rich). Sandstone detrital modes are subdivided into two distinctive petrofacies: the low quartz petrofacies (petrofacies I, Q<55% and L>12%), interpreted to retain the original provenance signal, and the high quartz petrofacies (petrofacies II, Q>55% and L<12%), representing the reworking product of the former after selective elimination of the more labile components. Petrofacies I sandstone framework grains were mainly derived from a dissected magmatic arc and an associated metamorphic belt. Textural evidence for recycling of some grains (e.g. garnet) from older sedimentary units during valley incision is not conclusive. Changes in the relative participation of source areas during the evolution of the incised-valley system are evaluated from the relative proportions of lithic fragments and monomineralic clasts derived from each rock type. Two lithic assemblages were recognized. The mixed lithic assemblage (Rv/Rm+Rp<1.4) shows participation of all rock types; it represented valley-confined environments, either during the initial stage of valley development, or after main episodes of incision. The volcanic lithic assemblage (Rv/Rm+Rp>1.4) is clearly dominated by volcanic-derived clasts; it developed at times of high sea level and/or during later stages of the valley fill, when an “energy fence” at the shoreline prevented delivery of sediment from the Antarctic Peninsula, thus enhancing the relative participation of local volcanic sources.  相似文献   

福建明溪盖洋地区震旦纪火山岩及古火山构造恢复   总被引：1，自引：0，他引：1  

胡宗良  陈兴高  吴泽有  冯宗帜 《福建地质》2002,21(1):1-9

明溪盖洋地区广泛发育的震旦纪火山岩，均已遭受区域变质，前人多数是从变质岩角度对其作研究，笔者是从火山岩及火山作用角度，在调研变质火山岩岩石宏观与微观特征的同时，着重调查古火山构造，研究不同火山产物空间分布特征，寻找残存的古火山构造形迹，并结合遥感资料信息。初步恢复古火山中心，为研究这一时期火山活动特点乃至南平-宁化构造-岩浆带的演化及古构造环境提供了新的资料。  相似文献   

Integrating Seismic Data for Lithofacies Modeling: A Comparison of Sequential Indicator Simulation Algorithms     

Tingting Yao 《Mathematical Geology》2002,34(4):387-403

Clastic reservoir characterization starts typically with modeling lithofacies distribution and geometry. The architecture of the reservoir, governed by the lithofacies geometry, is a major source of heterogeneity in such clastic systems. Seismic data provide potentially valuable information about the areal distribution of different lithofacies, such as the averaged prior proportion of each lithofacies. However, seismic data are available only at coarse vertical resolution rather than the fine lithofacies sampling along wells, hence seismic is considered equivalent to 2D data while building 3D geological models. This scale difference between the seismic data and the lithofacies data available along the wells makes direct integration difficult. Different algorithms have been proposed to integrate the seismic data: (1) duplicate seismic data along the vertical line and use the prior proportions provided by the seismic data as prior local means; (2) integrate the 2D seismic data as collocated block averages; and (3) duplicate seismic data along the vertical line and integrate them using a Markov-Bayes algorithm. These three algorithms are applied on a data set originating from a real clastic reservoir. The results are compared with regard to how much kriging weight is applied to the seismic data and how well the information from seismic data is honored.  相似文献