西藏多巴小区下古生界德吾卡下组岩石特征及时代讨论     

郭安臣  王彦  祝爽  邵学君 《吉林地质》2013,(4):18-19,30

笔者2012年在班戈西1/5万区域地质调查工作中,依据桑日PM5号剖面中岩石组合特征及笔石化石将原德吾卡下组划分为上下二段。下段主要为笔石粉砂岩相。上段主要为中层生物碎屑粉晶灰岩与灰绿、黄绿、黄褐色薄层粉砂岩互层。在下段笔石粉砂岩层位中获得的笔石化石,经鉴定种属为Monograptus sp,时代为早志留世。  相似文献   

中国特马豆克阶笔石地层述评   总被引：7，自引：1，他引：6  

张元动  王志浩  冯洪真  骆天天  B.-D. Erdtmann 《地层学杂志》2005,29(3):215-235

特马豆克阶是奥陶系第一个顶底界均已确立全球界线层型的年代地层单元,由于这两个GSSP都不在我国,因此如何在我国各个地区准确识别这两条界线,了解阶内的笔石和牙形刺序列,对我国奥陶纪地层和古生物研究具有重要意义。简要介绍特马豆克阶和奥陶系底界全球层型的纽芬兰GreenPoint剖面及特马豆克阶顶界全球层型的瑞典Diabasbrottet剖面,对界线附近的生物地层进行了分析讨论,并对GSSP的确立过程作了简要回顾。在以往大量成果积累及近年来工作的基础上,对我国特马豆克阶的笔石序列提出了新的观点:根据对吉林大阳岔等剖面的最新研究,华北板块的特马豆克阶笔石地层从下至上可以识别出4个笔石带——Rhabdinoporaflabelliformisparabola带、Anisograptusmatanensis带、Psigraptusjacksoni带和Aorograptusvictoriae带,弃用以往长期使用的Adelograptus-Clonograptus带;同时提出华南的特马豆克阶从下到上可以识别出7个笔石带——Rhabdinopora?taojiangensis带,R.flabelliformisparabola带,Anisograptusmatanensis带,R.flabelliformisanglica带,Aorograptusvictoriae带,Acanthograptussinensis带,Hunnegraptuscopiosus带。对采自四川古蔺纳羊箐桐梓组顶部笔石标本的研究表明,该层位相当于特马豆克期末的Hunnegraptuscopiosus带。此外还将我国的特马豆克阶笔石序列与国外若干主要地区进行了对比。  相似文献   

海相优质页岩的形成环境及发育模式——以中扬子地区秭归新滩剖面五峰—龙马溪组页岩为例          下载免费PDF全文

韩京  蔡全升  黎洋  李旭文 《古地理学报》2019,21(4):661-674

运用地球化学和岩石学方法,从古盐度、古气候、古生产力、海域封闭性以及氧化还原条件等方面,分析中扬子地区秭归新滩剖面上奥陶统五峰组—下志留统龙马溪组海相优质页岩的形成环境,并探讨了优质页岩发育的控制因素及模式。结果表明:中扬子地区五峰—龙马溪组优质页岩以硅质页岩为主,主要发育在五峰组至埃隆阶底部;优质页岩主要形成于温暖潮湿、低盐度—正常盐度、弱封闭—半封闭的缺氧环境中,并且具有较高的古生产力;海相优质页岩的发育是构造活动、海平面升降以及陆源—生物硅质供应等多因素综合作用的结果,而在埃隆期之后,随着扬子板块的持续向西北推进,海域面积不断萎缩,生物硅质供应降低,陆源碎屑供应迅速增加,优质页岩不再发育。最后,总结了海相优质页岩的发育模式。  相似文献   

内蒙古阿拉善左旗乌兰尚德地区志留系圆包山组笔石化石的发现及其地质意义     

王挨顺  马云飞  张宝艳  武力军  张云学  邢志强  刘明君  杨富广  梁志宝  贾永琦  赵佳佳  张强  孙泽晨 《地质通报》2019,38(6):950-958

阿拉善盟阿拉善左旗杭乌拉山以北哈日奥布日格断凹陷盆地两侧,北东向出露770km2的哑地层,前人将其划为二叠系双堡塘组,但该套地层的岩性和岩石组合及层序特征,与内蒙古岩石地层所述的双堡塘组的现在定义和地质特征及区域变化完全相悖。采用现代沉积学理论和层序地层学方法,开展岩石组合、基本层序、沉积构造与沉积环境研究,划分出3个段级填图单元。根据发现的笔石化石和被晚泥盆世中粗粒黑云母花岗闪长岩侵入的关系,将地层时代确定为早志留世,改划为志留系圆包山组。泥盆纪区域变质变形作用使其发生浅变质和片理化变形,并形成轴向北东的复式向斜构造。后期叠加构造变形,形成紧闭倒转褶皱。志留系圆包山组的确定对本区地层划分和区域构造演化研究有重要意义。  相似文献   

Graptolite‐Derived Organic Matter and Pore Characteristics in the Wufeng‐Longmaxi Black Shale of the Sichuan Basin and its Periphery     

WU Jin  ZHOU Wen  SUN Shash  ZHOU Shangwen  SHI Zhensheng 《《地质学报》英文版》2019,93(4):982-995

A key target of shale gas exploration and production in China is the organic-rich black shale of the Wufeng Formation-Longmaxi Formation in the Sichuan Basin and its periphery. The set of black shale contains abundant graptolites, which are mainly preserved as flattened rhabdosomes with carbonized periderms, is an important organic component of the shale. However, few previous studies had focused on the organic matter (OM) which is derived from graptolite and its pore structure. In particular, the contributions of graptolites to gas generation, storage, and flow have not yet been examined. In this study, focused ion beam-scanning electron microscope (FIB-SEM) was used to investigate the characteristics of the graptolite-derived OM and the micro-nanopores of graptolite periderms. The results suggested that the proportion of OM in the graptolite was between 19.7% and 30.2%, and between 8.9% and 14.4% in the surrounding rock. The total organic carbon (TOC) content of the graptolite was found to be higher than that of the surrounding rock, which indicated that the graptolite played a significant role in the dispersed organic matter. Four types of pores were developed in the graptolite periderm, including organic gas pores, pyrite moulage pores, authigenic quartz moldic pores, and micro-fractures. These well-developed micro-nano pores and fractures had formed an interconnected system within the graptolites which provided storage spaces for shale gas. The stacked layers and large accumulation of graptolites resulted in lamellation fractures openning easily, and provided effective pathways for the gas flow. A few nanoscale gas pores were observed in the graptolite-derived OM, with surface porosity lie in 1.5%–2.4%, and pore diameters of 5–20 nm. The sapropel detritus was determined to be rich in nanometer-sized pores with surface porosity of 3.1%–6.2%, and pore diameters of 20–80 nm. Due to the small amount of hydrocarbon generation of the graptolite, supporting the overlying pressure was difficult, which caused the pores to become compacted or collapsed.  相似文献   

The world's longest graptolite?     

David K. Loydell  Robert F. Loveridge 《Geological Journal》2001,36(1):55-57

An incomplete specimen of Stimulograptus halli 1.45 m long is recorded from the Aberystwyth Grits Formation north of Clarach, western mid‐Wales. This is the longest graptoloid graptolite known. Assuming a growth rate similar to that of modern Rhabdopleura it lived for at least 25 years. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

An Aeronian (Middle Llandovery) graptolite from the Pentamerus Beds near Hillend Farm,Shropshire, UK     

David K. Loydell  M. Paul Smith 《Geological Journal》2002,37(2):93-95

A specimen of Clinoclimacograptus retroversus is recorded from the Pentamerus Beds of the A489 road section near Hillend Farm, Shropshire, England. This specimen, combined with the presence of the brachiopod Eocoelia hemisphaerica, demonstrates that the beds here must be of mid to late Aeronian (Mid Llandovery) age. The fossiliferous horizons lie only a few metres above the Precambrian unconformity and thus help to constrain the timing of the transgression here. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

大巴山奥陶系的研究     

成汉钧  汪明洲  陈祥荣  许安东  陈淑娥 《地球科学与环境学报》1988,(1)

根据东西大巴山奥陶纪地层的差异性,划分为两个地层小区:宁强—西乡地层小区(西大巴山小区)和城口—巫溪小区(东大巴山小区)。对区内各剖面进行了划分和对比以后,分别建立起两小区内的综合地层分类系统。宁强—西乡小区分为三统、八组和十二个生物带(动物群),城口—巫溪小区分为三统、九组和十一个生物带(动物群)。将宁强—西乡小区宝塔组顶部的瘤状泥灰岩分出,与原涧草沟组合并,改称临湘组;并在剖面相互对比的基础上,讨论了七个有关问题。  相似文献   

桂北兴安奥陶纪至志留纪初笔石序列的再研究   总被引：1，自引：0，他引：1  

唐兰  陈旭  杨杰  杨兴莲  丛培允  杨显峰  王欣  张举  宋妍妍  陈中阳  侯旭东  张琳娜  孙海静 《地层学杂志》2013,(1):1-7

桂北兴安发育有一套奥陶系至志留系底部的含笔石浅变质的碎屑岩地层,自下而上可分成3个岩石地层单元,即升坪组(下部),黄隘组(中部)和田岭口组(上部)。这些地层的笔石自下而上可分为奥陶系Corymbograp-tus cf.balticus层,Expansograptus hirundo带,Exigraptus clavus-Undulograptus austrodentatus带,Didymogra-ptus artus带,Dicellograptus sextans带,Leptograptus flaccidus trentonensis层,Dicellograptus elegans层,Dicel-lograptus ornatus带,Appendispinograptus venustus层及志留系底部的Neodiplograptus modestus层。  相似文献   

Detailed paleogeographic evolution of the Bass Basin: Late Cretaceous to present     

D. Briguglio  J. Kowalczyk  J. D. Stilwell  M. Hall  A. Coffa 《Australian Journal of Earth Sciences》2013,60(6-7):719-734

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