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1.
The Lower Palaeozoic graptolitic sequence in the Southern Uplands of Scotland (Moffat Shales) is a highly condensed succession of marine shales, with much of the Ordovician and Early Silurian being represented by about 100 m of shales, mudstones and cherts. A total of 133 samples were collected from five main inliers and zoned by their graptolitic assemblages. These were analysed for the elements Si and Al (94 samples), Mg (80 samples), Ti, Fe, Mn, Ca, Na, and K (33 samples), and Cu, Pb, Zn, Rb, Sr, Y and Zr (133 samples). X-ray diffraction studies reveal the presence of quartz, illite, chlorite, carbonate and pyrite and these can be related to element associations brought out by correlation and multivariate statistical techniques. These studies reveal a systematic change up the succession based on an increasing contribution of clay to these sediments. Interpretation of the principal components indicates the main control of sedimentation to be physiographic, with physico-chemical conditions and decay of organic matter also being important. 相似文献
2.
K. E. Degtyarev T. Yu. Tolmacheva A. A. Tretyakov A. B. Kotov K. N. Shatagin 《Geotectonics》2016,50(1):71-142
A comprehensive study of the Lower Palaeozoic complexes of the Kokchetav Massif and its fringing has been carried out. It has allowed for the first time to discover and investigate in detail the stratified and intrusive complexes of the Cambrian–Early Ordovician. Fossil findings and isotope geochronology permitted the determination of their ages. The tectonic position and internal structures of those complexes have also been defined and their chemical features have been analyzed as well. The obtained data allowed us to put forward a model of the geodynamic evolution of Northern Kazakhstan in the Late Ediacaran–Earliest Ordovician. The accumulation of the oldest Ediacaran to Earliest Cambrian siliciclastics and carbonates confined to the Kokchetav Massif and its fringing occurred in a shallow shelf environment prior to its collision with the Neoproterozoic Daut island arc: complexes of the latter have been found in the northeast of the studied area. The Early Cambrian subduction of the Kokchetav Massif under the Daut island arc, their following collision and exhumation of HP complexes led to the formation of rugged ground topography, promoting deposition of siliceous–clastic and coarse clastic units during the Middle to early Late Cambrian. Those sediments were mainly sourced from eroded metamorphic complexes of the Kokchetav Massif basement. At the end of the Late Cambrian to the Early Ordovician within the boundaries of the massif with the Precambrian crust, volcanogenic and volcano-sedimentary units along with gabbros and granites with intraplate affinities were formed. Simultaneously in the surrounding zones, which represent relics of basins with oceanic crust, N-MORB- and E-MORB-type ophiolites were developed. These complexes originated under extensional settings occurred in the majority of the Caledonides of Kazakhstan and Northern Tian Shan. In the Early Floian Stage (Early Ordovician) older heterogeneous complexes were overlain by relatively monotonous siliceous–clastic units, that were being deposited until the Middle Darrivilian Stage (Middle Ordovician). 相似文献
3.
NILS-MARTIN HANKEN 《Sedimentology》1979,26(1):135-142
Moulds after aragonite fossils from two Upper Ordovician limestones in the Oslo Region are filled with well sorted clastic fine sand. The fossil moulds are thought to have been formed by selective dissolution of aragonite shell material by fresh water in the vadose zone. Internal sedimentation post-dates precipitation of a thin veneer of iron poor drusy calcite cement, but predates precipitation of ferroan blocky calcite cement. These age relationships and the texture of the fine sand suggests sedimentation in semiconsolidated sediment in the vadose zone of an island during early emergence. 相似文献
4.
Eight rare-earth elements (REE) have been determined in Cambro-Silurian sediments and volcanics from nine stratigraphic units in the Trondheim Region and ten stratigraphic units in the Oslo Region by neutron-activation analyses. In the eugeosynclinal sediments from the Trondheim Region the REE variations are related to variations in source material, which mainly are volcanic debris of local origin. In the foreland sediments from the Oslo Region significant development of clays has occurred and therefore the REE variations reflect the deposition environment. 相似文献
5.
Diagenetic and very low-grade metamorphic characteristics of the Paleozoic series of the Istanbul Terrane (NW Turkey) 总被引：1，自引：0，他引：1
The Istanbul Terrane along the Black Sea coast in NW Anatolia, is a Gondwana-derived continental microplate, comprising a well-developed Paleozoic succession. Petrographic and X-ray diffraction studies were performed on rock samples from measured sections throughout Ordovician?CCarboniferous sedimentary units. Diagenetic-very low-grade metamorphic clastic (shale/mudstone, siltstone, sandstone) and calcareous rocks (limestone, dolomite) mainly contain phyllosilicates, quartz, feldspar, calcite, dolomite, hematite and goethite minerals. Phyllosilicates are primarily represented by illite, chlorite, mixed-layered chlorite?Cvermiculite (C?CV), chlorite?Csmectite (C?CS) and illite?Cchlorite (I?CC). Feldspar is commonly present in the Ordovician and Carboniferous units, whereas calcite and dolomite are abundant in the Silurian and Devonian sediments. The most important phyllosilicate assemblage is illite?+?chlorite?+?I?CC?+?C?CV?+?C?CS. Illite and chlorite-bearing mixed layer clays are found in all units. The amounts of illites increase in the upper parts of the Silurian series and the lower parts of the Devonian series, whereas chlorite and chlorite-bearing mixed-layers are dominant in the Ordovician and Carboniferous units. Kübler index values of illites reflect high-grade anchimetamorphism for the Early Ordovician rocks, low-grade metamorphism to high-grade diagenesis for the Middle Ordovician?CEarly Silurian rocks and high-grade diagenesis for the Late Silurian?CDevonian units. The K-white micas b cell dimensions indicate intermediate pressure conditions in the Early Ordovician?CEarly Silurian units, but lower pressure conditions in the Middle Silurian?CDevonian units. Illites are composed of 2M 1?±?1M d polytypes in all units, except for Upper Ordovician?CLower Silurian units which involve 1M polytype in addition to 2M 1 and 1M d polytypes. The 2M 1/(2M 1?+?1Md) ratios rise from Devonian to Ordovician together with the increasing diagenetic-metamorphic grade. Chlorites have IIb polytype. In general, crystal-chemical data of clay minerals in the Istanbul Terrane show a gradual increase in the diagenetic/metamorphic grade together with increasing depth. The new data presented in this work indicate that the diagenetic/metamorphic grade of the Paleozoic of the Istanbul Terrane is higher than that of the neighboring Zonguldak Terrane and generated by a single metamorphic phase developed at the end of Carboniferous. This finding contrasts with the metamorphic history of the neighboring Zonguldak Terrane that displays a distinct Early Devonian unconformity and a thermal event. 相似文献
6.
Jean-François Ghienne Julien Moreau Lionel Degermann Jean-Loup Rubino 《International Journal of Earth Sciences》2013,102(2):455-482
The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidié and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic glacial erosion surface showing corrugated glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician glacial erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidié (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician glacial erosion surface amalgamate together. Here, an estimate of the glacial erosion depth cannot be derived from the stratigraphic hiatus beneath the glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related glacial erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities. 相似文献
7.
8.
Nirja Awasthi 《Contributions to Mineralogy and Petrology》1970,28(3):192-220
The Lower Krol sediments consist of intercalations of dolomite with shales in the marginal areas (Solan and Nainital), while limestones are interbedded with marls in the central part of the basin (Massoorie). The Upper Krols are largely composed of dolomites with subordinate limestones and shales.The non-carbonate detrital fraction is dominated by quartz with minor amounts of orthoclase, microcline and plagioclase feldspars. Illite and chlorite constitute the dominant clay minerals, lesser amounts of corrensite and kaolinite are sometimes present. An eastward increase in illite and decrease in chlorite has been ascribed to the supply and distribution of the terrigenum.Zirconium, rubidium, strontium, zinc, nickel and manganese were determined by X-ray fluorescence. Early diagenetic dolomites contain Sr, Zn, Ni and Mn in trace amounts, while the late diagenetic dolomites are characterized by an absence of these elements. The posttectonic dolomites are unusually rich in iron, manganese and sometimes in zinc.Authigenic formation of alkali feldspars, chlorite, illite, quartz and pyrite is not uncommon. The feldspars appear to have formed at early and late diagenetic stages. Potash feldspars dominate over albite in association with dolomite, whereas albite tends to be more common in the limestones.The Krol sedimentation seems to have started in a shallow coastal lagoon behind a barrier beach, upwards changing into tidal-flat deposits. 相似文献
9.
Mongkol Udchachon Punya Charusiri Hathaithip Thassanapak Clive Burrett 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(2):215-226
Lower Palaeozoic rocks have been mapped in Kayin State in an area previously shown on published maps as either metamorphic or possibly Lower or Upper Palaeozoic rocks. Three new formations, with a total thickness of over 900?m, apparently overlain by an, at least, 100?m thick Upper Palaeozoic formation are mapped along the Salween River and along the road from Yinbaing, in Myanmar, to Tha Song Yang, in Thailand. The Lower Palaeozoic succession consists of the predominantly siliciclastic Kyaukpulu and Kushwe–e–we formations and an overlying, predominantly carbonate Meseik Ashe Formation which contains Middle Ordovician (Darriwilian) conodonts. The older two formations are probable correlates of the Ngwetaung and Lokeypin formations of the southern Shan State of Myanmar and the Lower Ordovician siliciclastics of western Thailand. The overlying, peritidal to shallow subtidal carbonates of the Meseik–Ashe Formation are correlates of the Wunbye and Sitha formations of Shan State, Myanmar. The thick–bedded, quartz arenites of the Nyaungwiang Formation are faulted against the Ordovician carbonates and are probable lithological correlates of the Carboniferous Taungnyo Formation. The folds in the Lower Palaeozoic rocks are overturned to the northeast and deformation was in one major phase between the Tournaisian and the Early Permian. The Lower Palaeozoic strata may probably be followed as a ridge for at least 100?km towards the NNW, close to the western border of the Sibuma Block which is separated by a postulated cryptic suture from the Irrawaddy Block to the west. 相似文献
10.
我国中上扬子地区下古生界黑色页岩是震旦系、二叠系大中型气田的重要烃源岩,同时其自身也具有形成页岩气藏的巨大潜力。初步研究表明,中上扬子地区下古生界有利页岩气层主要发育在下震旦统陡山沱组、下寒武统筇竹寺组、上奥陶统五峰组和下志留统龙马溪组,这些层位的黑色页岩厚度、有机碳含量、以及Ro值等各项参数均符合形成页岩气藏的特征,是今后页岩气勘探的潜力地层。 相似文献
11.
Richard H. April 《Sedimentary Geology》1981,29(4):283-307
The clay mineralogy of the Newark Supergroup (Upper Triassic/Lower Jurassic) in the Connecticut Valley was studied by X-ray diffraction analysis. Clay minerals identified in 126 samples are illite, chlorite, smectite, kaolinite, vermiculite, expandable chlorite, mixed-layer illite/smectite, mixed-layer chlorite/smectite, and mixed-layer chlorite/vermiculite. In general, the rocks are illitic with subordinate amounts of chlorite. However, the various lithofacies in the Newark Supergroup are characterized by distinct clay-mineral assemblages. Red beds of floodplain origin contain clays mainly of detrital nature with 2M illite most abundant. Subordinate amounts of chlorite, smectite, vermiculite, kaolinite and mixed-layer illite/smectite are also present. An interstratified chlorite/vermiculite occurs in red mudstone underlying basalt flows. Lacustrine gray beds are generally characterized by the clay-mineral assemblage 1Md illite + chlorite with minor amounts of smectite ane expandable chlorite. An interstratified chlorite/smectite predominates in gray mudstone associated with perennial lake cycles in the East Berlin Formation. Black shales of deeper lacustrine origin contain the assemblage 1Md ifillite + trioctahedral smectite and traces of chlorite. Illite and smectite also occur as mixed-layer phases.In many respects, the distribution of clay minerals in the Connecticut Valley can be likened to the general scheme proposed for the Permo-Triassic basins of Europe and Africa. These display both vertical and horizontal variations in clay-mineral assemblages that reflect the chemical and spatiotemporal evolution of intrabasin depositional and diagenetic environments. Chemical data indicate that magnesium, especially, was concentrated in the black muds of large perennial lakes that intermittently occupied the Connecticut rift valley. Pore waters derived from these sediments played an important role in the development of Mg-rich 2 : 1 and interstratified clay minerals during early diagenesis. 相似文献
12.
Oil Source and Entrapment Epoch of the Ordovician Oil Reservoir in the Kongxi Burial-Hill Zone, Huanghua Depression, North China 总被引：6，自引：0，他引：6
WANG Tieguan WANG Feiyu LU Hong The Key Laboratory of Petroleum Entrapment Mechanism of Ministry of Educationin the University of Petroleum Beijing YANG Chiyin LIAO Qianjin ZHOU Jiansheng Geological Research Institute Dagang Oilfield 《《地质学报》英文版》2001,75(2):212-219
An oil flow obtained from the Middle Ordovician Fengfeng Formation carbonate reservoir in the well KG-3, Kongxi burial-hill zone in 1993 marked a breakthrough in petroleum exploration of the high-mature Lower Palaeozoic strata, North China. Both the Lower member of the Fengfeng Formation and the Second Member of the Upper Majiagou Formation in the Middle Ordovician are supposed to be the main source beds. Oil generation peaks range from 1.0% to 1.6% in Ro, showing a "lag effect" of oil generation in high-mature carbonate source rocks under multicyclic tectonic movement conditions. The Kongxi burial-hill zone adjoins a potential Ordovician source kitchen. The KG-3 Ordovician burial-hill reservoir has undergone two oil filling events, i.e., an early event in the Late Carboniferous-Permian and a more significant late event in the early Eogene. 相似文献
13.
塔里木盆地阿克苏-柯坪地区寒武系-奥陶系的沉积环境 总被引：8，自引：0，他引：8
本文讨论了塔里木西北缘厚一千余米的寒武系-奥陶系暗色碳酸盐岩夹细碎屑岩系的沉积环境。寒武系以粉-细晶白云岩、微晶叠层石白云岩夹细碎屑岩为主;奥陶系以含硅粉-细晶白云岩、内碎屑岩、细碎屑岩与灰岩的混合岩互层为主。根据矿物成分、生物化石、结构构造、岩石的元素、稳定同位素、矿物组合等判断,其沉积环境为半封闭的潮坪环境至开阔的陆棚沉积环境。 相似文献
14.
利用爱沙尼亚奥陶系含藻干酪根未成熟生油岩样品的加水热模拟实验结果,计算了下古生界藻干酪根在各不同演化阶段的平均表观活化能和频率因子。发现其演化的整个过程不完全符合化学反应的一级反应,而是分段符合,动力学参数随演化程度的升高而先降低后增加。其计算结果对于我国下古生界及中上元古界生油层盆地模拟和资源评价具有重要的参考价值。 相似文献
15.
A.E.KELEPERTSIS E.KONTIS 《中国地球化学学报》1997,16(1):8-19
The mineralogy and geochemistry data are presented for thirty-seven shales,four concretions,two carbonate sediments and seven lignites from the Marathousa coal field of the Megalopolis Basin in Greece.The argillaceous rocks consist of chlorite,illite,kaolinte,albite,quartz.opal-A,calcite and dolomite;the concretions of aragonite,gypsum and pyrite;and the carbonate rocks of calcite,quartz and illite.The mineral matter in the lignites consists of gypsum,quartz,albite,chlorite,illite,opal-A,dolomite,pyrite,and rarely calcite and kaolinite Athree-factor model explains the total variaition of major and trace elements in the argillaceous sediments.The first factor is an aluminosilicate factor and involves the following elements:Al,Si,Mg,Na,K,Ti,Mn,Nb,Y,Rb,Zn,Cu,Ni,Cr,Nband V,associated with chlorite,albite and illite.The second factor involves the elements Ca,Sr,Ba,Znand Sc and is related to carbonate lithology and mainly the carbonate concretions with gypsum.The third factor involves Fe and Ce with a weak association with Mn.The diagenesis of the Marathousa sediments and lignites was not very advanced as indicated by (a) the total thickness of the sequence (500m),(b) the presence of biogenic silica(opal-A) and (c) the age of the deposit(Pleistocene).FOr these reasons the rpresence of chlorite,illite and kaolinite in the sediments and lignite is due not to diagenetic reactions but to weathering of the flysch and metamorphic rocks at the edges of the Megalopolis Basin and transport of the weathering products(illite,chlorite,kaolinite)into the basin of deposition.The diagenetic minerals of the Marathousa sequence include pyrite,gypsum,dolomite and aragonite. 相似文献
16.
胜利油区早古生代沉积相 总被引：3，自引：0，他引：3
早古生代，胜利油区作为华北地台的一部分，接受了一套以海相碳酸盐岩为主的沉积，其沉积相与其他地区既有相似性，又有特殊性。文中首先按沉积岩类型，将沉积相划分为碎屑沉积相系和碳酸盐岩沉积相系。根据岩石的沉积构造、指相矿物、生物化石等，将下古生界沉积相进一步划分为４个相９种亚相，并对各种相的特征进行了简要说明。在单井相分析的基础上，利用单因素和三端元作图法编制了基础图件，结合相序的变化规律和区域地质背景，对区内早古生代不同时期的沉积相展布特征进行了探讨：馒头期—徐庄期，基本为潮上到潮间带；张夏期—崮山期，发育有潮下浅滩和开阔海两种主要沉积相；长山期—早奥陶世，以潮间—潮下带为主；中奥陶世，以浅水的潮上、潮间带与较深水的潮下带间互出现。研究早古生代沉积相，对于评价碳酸盐岩储层和烃源岩有重要意义。 相似文献
17.
河北卢龙武山寒武系-奥陶系界线剖面暴露良好、沉积连续、具有典型海相沉积特征以及丰富的古生物标准化石(如三叶虫和牙形刺等),因此该处受到许多地质研究人员的重视并被选为华北型寒武系-奥陶系界线层型剖面的地点。本文配合寒武系-奥陶系界线层型剖面的研究,对界线附近地层的粘土矿物进行了鉴定并探讨了古沉积环境。 相似文献
18.
上扬子区下古生界层序地层格架的初步研究 总被引：19，自引：5，他引：14
上扬子区下古生界在贵州及其邻区发育较为完整。在震旦纪与寒武纪之交的台地淹没事件之后,寒武系形成一个从深水盆地相黑色页岩系到大套台地碳酸盐的沉积序列,其中下寒武统包含5个三级层序而可以进一步归为一个二级层序,中上寒武统构成一个二级层序而且可以进一步划分为7个三级层序。奥陶纪艾家山世末期的都匀运动、奥陶纪末期的与冈瓦纳大陆冰期相响应的全球海平面下降事件以及志留纪末期广西运动的共同作用,造成扬子地台大幅度的古地理变迁以及残留不全的奥陶系和志留系。详尽追踪和对比的结果可以将奥陶系划分为8个三级层序且可以进一步归为一个二级层序,在残留不全的的志留系中可以划分出7个三级层序并可以进一步归为一个二级层序。层序地层格架的建立,可以大致解读许多有趣的地质现象,如寒武纪碳酸盐台地的生长过程,奥陶纪与志留纪之交的“浅海静水”型黑色页岩系的发育特点,志留纪由北而南的海侵所造成的复杂的志留系展布特征等等;同时也意味着许多有待于进一步研究的问题,早寒武世数次快速海侵事件与生物事件的关系,奥陶系顶部特殊的“观音桥灰岩”的成因,奥陶系红花园组海绵生物礁的基本沉积模式等等。 相似文献
19.
《International Geology Review》2012,54(12):1410-1427
Existence of Sinian to lower Paleozoic formations in this area is confirmed by discoveries made since 1957, by the faculty of the Geological Department of Nanking University, of abundant fossils including graptolites, trilobites and Protospongia. Pre-Devonian strata here exceed 12,000 m in thickness and belong to typical geosynclinal sediments. Summarized in ascending order, these strata are - 1) pre-Sinian (lower Proterozoic), including the Ta-yu and Li-ch'un groups; 2) Sinian, with the Ku-t'ing group; 3) Lower Cambrian, with the Ho-t'ang formation; 4) Middle and Upper Cambrian, Pa-ch'un group; 5) Lower Ordovician, including Yin-tu-hu and Ning-kuo formations; Middle Ordovician, Hu-lo formation; Upper Ordovician, Sha-ch'un group. -- Authors. 相似文献
20.
用野外露头剖面、钻井剖面和地震剖面相结合的综合研究方法,首先用人工合成记录结合11口井的VSP资料,对鄂尔多斯下古生界进行层位标定。在此基础上,对鄂尔多斯全区下古生界371条共长15 683 km的地震剖面进行了重新处理和地层解释,这大大提高了解释精度。以此为基础,把鄂尔多斯下古生界划分为5个地层单位,即寒武系中下部、寒武系中上部及冶里组和亮甲山组、马家沟群下部、马家沟群上部、平凉组和背锅山组,并作出了它们的等厚图。从这些等厚图可以看出：前4个地质时期的古构造格局为“一隆三凹”,即西缘凹陷、南缘凹陷和东缘凹陷(或东部凹陷)呈“U”形从西南东三面包围着一个中部隆起。最后一个地质时期的古构造格局为“一隆二凹”,即西缘凹陷和南缘凹陷呈“L”形镶嵌在一个巨大的鄂尔多斯隆起的西缘和南缘。到奥陶纪末,鄂尔多斯全区以及整个华北地台均变为隆起区,从而结束了鄂尔多斯隆起和凹陷并存的历史。 相似文献