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1.
V N Sergeev A H Knoll S P Kolosova P N Kolosov 《Stratigraphy and Geological Correlation》1994,2(1):19-33
Silicified shallow-water marine carbonate deposits of the Proterozoic Debengda Formation (the Olenek Uplift, northeastern Siberia) contain well preserved microfossils. One or two distinct assemblages consists only of filamentous Siphonophycus microfossils, which are presumably the extracellular sheaths of hormogonium cyanobacteria. The other is dominated by coccoidal microfossils, first by the entophysalidacean cyanobacterium Eoentophysalis. The coccoidal assemblage was recognized in the layered carbonate precipitate structures of a superficially stromatolite appearance. Despite its simple composition, the microfossil assemblage supports the generally accepted Mesoproterozoic (middle Riphean) age of the Debengda Formation. This conclusion corresponds to the available data on isotopic geochronology, and to the composition of columnar stromatolites from the Dehengda Formation. Both the structural features and carbon isotopic composition of its rocks are comparable to those of rocks of known Mesoproterozoic age, but differ from the characteristics of definitely Neoproterozoic deposits. 相似文献
2.
Silicified carbonates of the latest Mesoproterozoic Sukhaya Tunguska Formation, northwestern Siberia, contain abundant and diverse permineralized microfossils. Peritidal environments are dominated by microbial mats built by filamentous cyanobacteria comparable to modern species of Lyngbya and Phormidium. In subtidal to lower intertidal settings, mat-dwelling microbenthos and possible coastal microplankton are abundant. In contrast, densely woven mat populations with few associated taxa characterize more restricted parts of tidal flats; the preservation of vertically oriented sheath bundles and primary fenestrae indicates that in these mats carbonate cementation was commonly penecontemporaneous with mat growth. Eoentophysalis mats are limited to restricted environments where microlaminated carbonate precipitates formed on or just beneath the sediment surface. Most microbenthic populations are cyanobacterial, although eukaryotic microfossils may occur among the simple spheroidal cells interpreted as coastal plankton. Protists are more securely represented by large (up to 320 micrometers in diameter) but poorly preserved acritarchs in basinal facies. The Sukhaya Tunguska assemblage contains 27 species in 18 genera. By virtue of their stratigraphic longevity and their close and predictable association with specific paleoenvironmental conditions, including substrates, Proterozoic cyanobacteria support a model of bacterial evolution in which populations adapt rapidly to novel environments and, thereafter, resist competitive replacement. The resulting evolutionary pattern is one of accumulation and stasis rather than the turnover and replacement characteristic of Phanerozoic plants and animals. 相似文献
3.
The Neoarchean Carawine Formation, Hamersley Group, Western Australia is a carbonate ramp that preserves diverse microbial structures which are characteristic of specific depositional environments. These distinctive structures are distributed in five shallow subtidal and two deeper‐water facies in the Oakover area of the Carawine Formation. The shallow subtidal facies are composed of biohermal and bedded stromatolites, centimetre‐scale ridge‐shaped microbialites and wavy‐laminated microbialites. The deeper‐water facies are composed of fenestrate microbialites, planar laminated dolostone and dolostone with rolled‐up microbial laminae. Microbialites in the Carawine Formation lie within a continuum of Archean to Proterozoic microbial facies. Some shallow‐water microbial facies in the Carawine Formation are similar to Proterozoic facies, such as large bioherms internally composed of a variety of stromatolite morphologies. In contrast, fenestrate microbialites grew in quiet subtidal environments and are common in Archean rocks but have not been documented in similar Proterozoic environments. The similarity of shallow‐water facies across the Archean–Proterozoic transition, before and after the oxidation of the atmosphere and surface oceans, indicates that stromatolite growth in shallow subtidal environments was not strongly affected by the chemical changes associated with oxidation of the oceans or by biological responses to those chemical changes. Rather, stromatolite morphology was controlled mostly by the physical environment and the corresponding biological responses to that environment. In contrast, the absence of fenestrate microbialites from Proterozoic deep subtidal environments suggests that the morphology of deep subtidal microbial structures was influenced by chemical or biological changes that occurred in association with oxidation of the surface oceans. 相似文献
4.
臼齿构造是一种发育于中、新元古代碳酸盐岩中的具有特殊结构和时限性的沉积构造,其成因有多种解释。徐州地区新元古界贾园组风暴沉积及臼齿构造发育。本文通过野外和室内观察研究,对研究区贾园组臼齿构造形态特征及沉积环境进行分析,并探讨其形成过程。贾园组臼齿构造集中发育于古纬度20°N~34°N的潮下碳酸盐岩缓坡地带,古海洋基底在地震波作用下产生裂隙系统,元古代特殊大气成分背景下的海水中的远源风暴流渗透进入温暖的碳酸盐缓坡地带碳酸盐沉积区的裂隙系统,并在裂隙的愈合作用下与孔隙水产生化学反应产生方解石快速结晶作用,并接受后期沉积作用改造。元古代大地构造背景、古海洋、古大气的物理化学条件是控制研究区臼齿构造时空分布的主要因素。 相似文献
5.
阿克苏地区地处塔里木克拉通西北部的盆-山结合部位,新元古代地层齐全且发育前寒武纪蓝片岩,保留了新元古代从洋壳俯冲汇聚到陆壳拉张伸展过程的记录,是近年塔里木新元古界研究的热点及重点地区。但阿克苏地区新元古代地层层序和沉积体系的研究较为薄弱,构造对沉积充填的控制作用仍不清楚,由此也制约着对塔里木克拉通初期裂谷发育演化的认识。本文综合地层学、沉积学等多种研究手段,分析阿克苏地区新元古代地层展布及垂向发育特征,将多处实测剖面与钻井-地震剖面结合,构建了阿克苏地区新元古代地层发育序列及空间对比格架。明确了由裂陷控制的沉积相类型及演化：南华纪巧恩布拉克组先后发育冲积扇/扇三角洲、水下-冰川亚相（冰碛岩）及深水陆棚相;尤尔美那克组,早期以陆上-冰川沉积为主,晚期以冲积扇沉积为主;震旦纪苏盖特布拉克组由冲积扇过渡到辫状河三角洲和潮坪相;奇格布拉克组以碳酸盐岩台地沉积为主。通过盆-山构造结合沉积序列分析,确定新元古代经历了三个构造-沉积演化阶段：（1）局限深裂谷发育阶段（南华纪）,充填冲积扇/扇三角洲及深水陆棚相沉积,其中发育两期不同环境的冰川沉积;（2）裂谷扩张期（震旦纪早期）,火山活动强烈,发育冲积扇-辫状河三角洲、潮坪相沉积;（3）坳陷发育期（震旦纪晚期）,广盆浅海环境,发育碳酸盐岩台地。 相似文献
6.
Distinctive, metre‐scale antiformal structures are well developed in a Famennian carbonate platform in the Chedda Cliffs area of the Lennard Shelf reef complexes. The structures are distinguished by chevron‐shaped crests and thickened cores and contain abundant non‐skeletal allochems (ooids/pisoids, peloids and intraclasts) of silt to pebble size and variably developed laminations and fenestrae. The internal morphology and pervasive occurrence of fenestral clotted and wavy laminated fabrics suggest that these structures are microbial mounds composed of agglutinated stromatolites and thrombolites. Microbial fabrics most probably originated through sediment trapping and binding by microbial mats with early lithification involving microbial calcification and cementation of trapped sediment. The facies and stratigraphic context of the mounds support a shallow subtidal, transitional backreef to reef‐flat setting; however, alone these mounds do not provide unequivocal environmental information. Other large antiformal structures in Famennian platforms on the Lennard Shelf, previously described as tepee structures, show morphological similarities to the Chedda Cliffs mounds, which suggests that these other structures may also be microbial mounds. The presence of microbial mounds in platform successions further highlights the importance of microbial communities in the Lennard Shelf reef complexes. 相似文献
7.
Carbonate platform growth and cyclicity at a terminal Proterozoic passive margin, Infra Krol Formation and Krol Group, Lesser Himalaya, India 总被引：3，自引：0，他引：3
Ganqing Jiang Nicholas Christie-Blick† Alan J. Kaufman‡ Dhiraj M. Banerjee§ Vibhuti Rai¶ 《Sedimentology》2003,50(5):921-952
Abstract The Infra Krol Formation and overlying Krol Group constitute a thick (< 2 km), carbonate-rich succession of terminal Proterozoic age that crops out in a series of doubly plunging synclines in the Lesser Himalaya of northern India. The rocks include 18 carbonate and siliciclastic facies, which are grouped into eight facies associations: (1) deep subtidal; (2) shallow subtidal; (3) sand shoal; (4) peritidal carbonate complex; (5) lagoonal; (6) peritidal siliciclastic–carbonate; (7) incised valley fill; and (8) karstic fill. The stromatolite-rich, peritidal complex appears to have occupied a location seaward of a broad lagoon, an arrangement reminiscent of many Phanerozoic and Proterozoic platforms. Growth of this complex was accretionary to progradational, in response to changes in siliciclastic influx from the south-eastern side of the lagoon. Metre-scale cycles tend to be laterally discontinuous, and are interpreted as mainly autogenic. Variations in the number of both sets of cycles and component metre-scale cycles across the platform may result from differential subsidence of the interpreted passive margin. Apparently non-cyclic intervals with shallow-water features may indicate facies migration that was limited compared with the dimensions of facies belts. Correlation of these facies associations in a sequence stratigraphic framework suggests that the Infra Krol Formation and Krol Group represent a north- to north-west-facing platform with a morphology that evolved from a siliciclastic ramp, to carbonate ramp, to peritidal rimmed shelf and, finally, to open shelf. This interpretation differs significantly from the published scheme of a basin centred on the Lesser Himalaya, with virtually the entire Infra Krol–Krol succession representing sedimentation in a persistent tidal-flat environment. This study provides a detailed Neoproterozoic depositional history of northern India from rift basin to passive margin, and predicts that genetically related Neoproterozoic deposits, if they are present in the High Himalaya, are composed mainly of slope/basinal facies characterized by fine-grained siliciclastic and detrital carbonate rocks, lithologically different from those of the Lesser Himalaya. 相似文献
8.
天津蓟县中元古界雾迷山组是一套厚度超过3000,m的叠层石碳酸盐岩沉积序列,在该序列中潮下相叠层石生物层、凝块石生物丘与潮坪相泥晶白云岩、潟湖相白云质泥页岩一起构成若干个环潮坪型米级旋回——"雾迷山旋回层"。在雾迷山组下部发育微指状叠层石,并被古生物学家定义为"Pseudogymnosolen mo-panyuensis-Scuphus-Yangzhuang columnaris"组合,即假裸枝叠层石科叠层石,沉积学家将其解释为元古代文石(灰华)海底沉淀物所构成的叠层石,代表从太古代海底结壳状文石沉淀物组成的叠层石到新元古代碎屑结构相的泥晶碳酸盐岩叠层石过渡时期的特殊产物。因此,雾迷山组巨厚的叠层石碳酸盐岩沉积序列,记录了元古代文石(灰华)海底沉淀物所构成的特殊的叠层石大规模消亡的层位,为研究前寒武纪以叠层石为代表的微生物碳酸盐岩所经历的漫长而复杂的地质历史演变提供了宝贵的材料。 相似文献
9.
Rocks of the Early Proterozoic Nabberu Supergroup were deposited in the Nabberu Basin along the northern margin of the Archaean Yilgarn Shield in Western Australia. The Nabberu Basin consists of three tectonic-sedimentary units known as the Earaheedy, Glengarry and Padbury Sub-basins.The Earaheedy Group within the easternmost sub-basin is divided into a lower Tooloo Sub-group and an upper Miningarra Sub-group, representing succeeding sedimentary cycles totalling some 6000 m of shallow water sediments. The Tooloo Sub-group comprises thin quartzose to arkosic clastics (Yelma Formation) which rest unconformably on Archaean rocks, and are overlain by chert, shale, iron formations and minor carbonate (Frere Formation), and thinly bedded carbonate, shale and sandstone (Windidda Formation). The overlying Miningarra Sub-group includes sandstone and shale (Wandiwarra Formation), super-mature quartz sandstone and arkosic siltstone (Princess Ranges Quartzite), fine arkosic sandstone, siltstone, shale and carbonate (Wongawol Formation), limestone, shale and sandstone (Kulele Creek Limestone) and sandstone and shale (Mulgarra Sandstone). Distinctive stromatolite assemblages occur in carbonate units throughout the sequence.Iron formations of the Frere Formation are similar to those of the Lake Superior and Labrador Provinces of North America, and commonly have a distinctive pelletal (intraclastic) texture, but are locally oolitic or laminated. Benthonic microfossils found at one locality are identical to those in the Lake Superior iron formations (Walter et al., 1976).West into the Glengarry Sub-basin and Peak Hill—Robinson Ranges area the basal clastics become considerably thicker, finer-grained and more varied, and are commonly interbedded with basaltic volcanics and greywackes. The Peak Hill Beds (MacLeod, 1970), Finlayson Sandstone and Maraloou Formation (Bunting et al., 1977) may be lateral equivalents of the Yelma Formation, while the overlying Horseshoe Range Beds, Labouchere Formation and Robinson Range Formation (Barnett, 1975) are possible equivalents of the Frere Formation. The Millidie Creek Formation may be equivalent to the Wandiwarra Formation.Deformation of the Nabberu Basin has resulted in the development of the Stanley Fold Belt in the north and the Kingston Platform in the south. On the Kingston Platform the rocks dip very gently north, but deformation increases northwards. A slaty cleavage becomes more conspicuous in this direction, while folds become tighter, overturned southwards and cut by north-dipping thrusts. The fold belt trends west-northwest across the eastern portion of the basin before swinging to the southwest. Archaean basement is increasingly involved in the deformation and becomes progressively more gneissic as the Early Proterozoic rocks become more strongly schistose. Refolding of early structures is pronounced in the west. Metamorphic grade, based on mineral assemblages in basic, pelitic and carbonate rocks and iron formations, also increases north and northwest, reaching a maximum grade of granulite facies west of the Robinson Ranges. The sediments are essentially unmetamorphosed in the southeastern part of the basin. 相似文献
10.
吉林南部通化二道江剖面新元古界万隆组臼齿构造及其沉积特征 总被引：1，自引：3，他引：1
吉林南部通化二道江剖面新元古界万隆组广泛发育缓坡碳酸盐岩沉积,其中发育的一种特殊的碳酸盐岩——臼齿碳酸盐岩,近年来引起了中国乃至世界各国地质学家的重视。通过对野外露头的详细观察和描述、室内薄片观察、扫描电镜、能谱分析等测试手段,揭示了二道江剖面万隆组的地层、岩石、臼齿构造(MT)及沉积岩相和沉积环境特征。臼齿构造是特指那些发育在前寒武纪细粒碳酸盐岩中有清晰边界、粒度在0·01mm左右的由等轴或多边形的微亮晶方解石组成的集合体,其形态可分为条带状构造、瘤状构造及棱角碎块状构造。臼齿构造的形成严格受沉积岩相和沉积环境的控制。万隆组由下而上可分为3段第1段下部为发育臼齿构造的纹层状泥晶灰岩、砂屑灰岩及风暴砾屑灰岩,为中—深缓坡沉积环境的产物;上部由浅缓坡相的泥灰岩、钙质页岩、砂屑灰岩与叠层石灰岩组成;第2段为厚层泥晶灰岩和粉屑泥晶灰岩、瘤状灰岩组成的深缓坡相沉积;第3段本剖面未出露。万隆组形成于缓坡沉积环境,其中浅缓坡相可分为4种岩相组合,中缓坡相可分为11种岩相组合,深缓坡相有6种岩相组合。 相似文献
11.
大连地区甘井子组是辽宁重要的新元古界层位,发育大量的碳酸盐岩.运用经典层序地层学理论,通过对野外实测剖面的综合分析,对大连地区新元古界震旦系甘井子组进行层序地层学研究,共识别出5个层序界面,划分了4个三级层序,15个准层序组和55个准层序.甘井子组碳酸盐岩沉积可划分为局限台地亚相和开阔台地亚相,进一步划分为潟湖、潮坪、潮下低能和浅滩微相.运用区域大地构造和天文旋回方法对甘井子组环境演化进行探讨,认为其经历了局限台地→开阔台地→局限台地的演化过程.受扬子旋回末期低幅度的构造升降作用影响,大连地区南关岭期末期—甘井子期出现了5次短暂暴露,形成了5个层序界面.同时受周期性天文旋回的影响形成了准层序、层对等高频旋回.通过对大连地区甘井子组进行层序地层和沉积演化研究,为探索辽东南地区的油气资源提供依据. 相似文献
12.
寒武纪芙蓉统均一石沉积组构及环境特征——以河北涞源长山组为例 总被引：1，自引：1，他引：0
均一石以隐晶质岩性、无纹层与凝块结构发育为特征,与叠层石、凝块石、树形石并列为典型的微生物岩。然而,由于均一石在1995年命名以来很少在地层记录中得到识别和描述,并且缺乏现代实例的类比物,使得关于均一石的报道极具研究价值。为研究华北地台寒武系均一石沉积组构与形成环境特征,系统性地针对河北涞源祁家峪剖面芙蓉统长山组均一石生物丘进行研究。芙蓉统长山组从下部陆棚相钙质泥岩向上变浅至浅缓坡相厚层块状泥晶灰岩,组成了一个淹没不整合型三级层序。三级层序顶部的浅缓坡相厚层块状泥晶灰岩层,代表强迫型海退过程沉积,其内部发育一系列米级均一石生物丘。研究结果表明,这些生物丘主体为致密泥晶及少量微量晶组成,其中可见到附枝菌(Epiphyton)、葛万菌(Girvanella)、肾形菌(Renalcis)等钙化微生物化石。这些钙化微生物(蓝细菌)化石的出现,代表了显生宙第一幕蓝细菌钙化作用事件的证据,同时间接的说明均一石生物丘形成于蓝细菌主导的微生物席的钙化作用过程之中。同时,生物丘内还局部集中发育底栖鲕粒与草莓状黄铁矿颗粒,表明了生物丘形成过程中复杂的微生物沉积作用机制。因此,河北涞源长山组顶部的均一石生物丘,尽管泥晶和微亮晶是其基本构成,但是各种钙化蓝细菌化石以及底栖鲕粒与草莓状黄铁矿颗粒的局部出现表明了在蓝细菌主导的微生物席中复杂的微生物活动信号,成为了解生物丘形成机制、显生宙第一幕蓝细菌钙化作用事件的典型实例。 相似文献
13.
华南上扬子区早-中奥陶世疑源类古环境意义 总被引：1，自引：2，他引：1
对上扬子区 7个剖面早—中奥陶世疑源类研究表明 ,这些疑源类组合在分异度及属种组成上呈现有规律的变化 ,这种变化是上扬子区古环境变化的反映。在上扬子区西部 ,近岸碎屑岩相沉积的滇东红石崖组所产疑源类组合分异度低 ,为个体较小、壳饰较简单的分子 ;上扬子区中部 ,以黔北湄潭组为代表的浅海相碎屑岩和灰岩沉积中 ,疑源类分异度较高 ,并出现许多个体较大、壳饰较复杂的分子 ;而在上扬子区东部鄂西宜昌大湾组陆棚相灰岩与泥岩中 ,疑源类分异度继续增高 ,其中个体大、具粗大、长而复杂突起的分子占优势。 相似文献
14.
Distinctive lithological associations and geological relationships, and initial geochronological results indicate the presence of an areally extensive region of reworked Archaean basement containing polymetamorphic granulites in the Rauer Group, East Antarctica.
Structurally early metapelites from within this reworked region preserve complex and varied metamorphic histories which largely pre-date and bear no relation to a Late Proterozoic metamorphism generally recognized in this part of East Antarctica. In particular, magnesian metapelite rafts from Long Point record extreme peak P–T conditions of 10–12 kbar and 100–1050°C, and an initial decompression to 8 kbar at temperatures of greater than 900°C. Initial garnet–orthopyroxene–sillimanite assemblages contain the most magnesian (and pyrope-rich) garnets ( XMg = 0.71) yet found in granulite facies rocks. A high-temperature decompressional P–T history is consistent with reaction textures in which the phase assemblages produced through garnet breakdown vary systematically with the initial garnet X Mg composition, reflecting the intersection of different divariant reactions in rocks of varied composition as pressures decreased. This history is thought to relate to Archaean events, whereas a lower-temperature ( c. 750–800°C) decompression to 5 kbar reflects Late Proterozoic reworking of these relict assemblages.
The major Late Proterozoic ( c. 1000 Ma) granulite facies metamorphism is recorded in a suite of younger Fe-rich metapelites and associated paragneisses in which syn- to post-deformational decompression, through 2–4 kbar from maximum recorded P–T conditions of 7–9 kbar and 800–850°C, is constrained by geothermobarometry and reaction textures. This P–T evolution is thought to reflect rapid tectonic collapse of crust previously thickened through collision. 相似文献
Structurally early metapelites from within this reworked region preserve complex and varied metamorphic histories which largely pre-date and bear no relation to a Late Proterozoic metamorphism generally recognized in this part of East Antarctica. In particular, magnesian metapelite rafts from Long Point record extreme peak P–T conditions of 10–12 kbar and 100–1050°C, and an initial decompression to 8 kbar at temperatures of greater than 900°C. Initial garnet–orthopyroxene–sillimanite assemblages contain the most magnesian (and pyrope-rich) garnets ( X
The major Late Proterozoic ( c. 1000 Ma) granulite facies metamorphism is recorded in a suite of younger Fe-rich metapelites and associated paragneisses in which syn- to post-deformational decompression, through 2–4 kbar from maximum recorded P–T conditions of 7–9 kbar and 800–850°C, is constrained by geothermobarometry and reaction textures. This P–T evolution is thought to reflect rapid tectonic collapse of crust previously thickened through collision. 相似文献
15.
通过对塔北奥陶系碳酸盐岩沉积相类型、相带区域组合及分布特征的研究,根据岩石特征、沉积结构和相序特征的分析,建立了塔北奥陶系碳酸盐岩的沉积演化模式。研究认为塔北下奥陶统蓬莱坝组、中下奥陶统鹰山组、中奥陶统一间房组和上奥陶统吐木休克组沉积相横向分布较稳定。蓬莱坝组、鹰山组鹰四段、鹰三段为局限台地相;鹰二段为半局限台地相;鹰一段和一间房组属于开阔台地相,但向上水体不断变浅,一间房组沉积时期开始出现点礁;上奥陶统吐木休克组沉积时期区域整体沉降,为沉没台地-斜坡-盆地沉积。上奥陶统良里塔格组沉积时期盆地整体抬升,区域沉积厚度和沉积相出现较大变化,早中期发育碳酸盐开阔台地相,后期为典型的台地边缘相。 相似文献
16.
米仓山地区早寒武世仙女洞组沉积物源新认识：沉积学、重矿物和碎屑锆石年代学的证据 总被引：1，自引：0，他引：1
长期以来,一直认为米仓山地区早寒武世地层主要由汉南古陆和/或摩天岭古陆提供沉积物,实际并非如此。米仓山地区早寒武世仙女洞组主要由鲕粒灰岩以及角砾灰岩等组成。本文根据沉积相时空展布、交错层理恢复的物源方向、重矿物以及碎屑锆石LA-ICP-MS U-Pb测年,综合探讨仙女洞组的物源方向以及物源区。沉积相时空展布和古流向表明,仙女洞组的物源主要来自西北和西南方向,非前人判断沉积物来自东北和/或西北方向。碎屑重矿物锆石、磷灰石、白钛石、铬尖晶石和磁铁矿组合表明物源主要来自于岩浆岩,部分为基性岩浆岩。对仙女洞组3件样品碎屑锆石U-Pb年龄分析,获得172组U-Pb有效年龄。碎屑锆石的谐和年龄表明,物源主要集中在744~896Ma和1755~2493Ma。综合相展布、古水流、重矿物组合以及碎屑锆石测年,仙女洞组的物源主要来自:(1)西北方向,摩天岭古陆的碧口群、横丹群和鱼洞子群的火山-沉积岩以及新元古代侵入岩;(2)西南方向,主要为康滇古陆的花岗岩、流纹岩、辉绿岩等。 相似文献
17.
采用微相分析的方法,对新疆阿合奇地区晚石炭世—早二叠世哈拉奇组和康克林组碳酸盐岩的微相类型和沉积环境进行了研究,发现两地层单元具有不同的岩石结构、颗粒组分及生物化石组合微相特征。哈拉奇组沉积粒度相对较细,泥质含量较高,生物碎屑相对较少,可划分出5种微相类型和5种次一级微相类型;康克林组生物种类丰富,个体保存较完整,颗粒组分出现了较多鲕粒、核形石等,亮晶胶结普遍,泥级组分相对较少,可划分出6种微相类型和8种次一级微相类型。根据微相类型组合特征和野外沉积构造,认为哈拉奇组碳酸盐岩主要形成于深水陆棚和台地斜坡2种沉积环境,其次为台地边缘浅滩和开阔台地沉积,总体反映较深水沉积环境;康克林组碳酸盐岩主要形成于台地边缘浅滩、开阔台地和局限台地3种沉积环境,反映沉积环境水体相对较浅。 相似文献
18.
Sedimentary Facies and Distribution of Reservoir Rocks from the Feixianguan Formation in the Daxian-Xuanhan Region, NE Sichuan 总被引：1，自引：0，他引：1
MA Yongsheng MOU Chuanlong GUO Xusheng YU Qian TAN Qinyin 《《地质学报》英文版》2006,80(1):137-151
The Lower Triassic Feixianguan Formation in the Daxian-Xuanhan region, northeastern Sicbuan is interpreted to be a carbonate platform intermediate between the West Hubei-East Cbongqing marine basin and Guangyuan-Wangcang marine basin. Outcrops, well logs and seismic data have disclosed that three sedimentary facies can be identified for the formation： open platform, platform exposed shoal and restricted platform facies. During the early stage of deposition of the Feixianguan Formation, there existed a sedimentary framework all the same as the Late Permian one： open platform in the west, and platform exposed shoal, restricted platform and open platform eastwards. The gradual increase of the shoal area permitted eastward migration of the shoal facies. During the deposition of the third member of the Feixianguan Formation, the study area was invaded by temporary transgressions. Till the deposition of the fourth member of the formation, the study area was prevailed over the unified restricted platform deposits, as indicated by the sedimentary model for the typical carbonate platform shoal deposits. The reservoir rocks in the Feixianguan Formation consist mostly of solution opening dolostone, and the rock types are assembled by oolitic dolostone, residual oolitic dolostone and sucrosic residual oolitic medium- to coarse-grained dolostone. The deep and shallow dual laterologs show relatively high resistivity, clear amplitude differences and time difference saltation of acoustic waves in some intervals. The seismic responses are indicated by low-frequency and highly variable amplitudes and chaotic reflection configurations. The reservoir rocks are characterized by high porosity-high permeability and medium porosity-medium permeability, showing a marked correlation between porosity and permeability. Solution openings are extremely developed in the reservoir rocks, including cast pores, intergranular solution openings, intercrystal pores, intercrystal solution openings, solution openings （caves） and minute fissures. Macropores and coarse pore throats are common. The reservoir rocks are apparently controlled by sedimentary facies in distribution patterns. Vertically, they occur dominantly in the second and first members of the Feixianguan Formation, and laterally in the platform exposed shoals and restricted platforms, where good natural gas potential is expected. 相似文献
19.
Field and laboratory analyses of carbonate rock samples from the Qiangtang Basin,Tibet, indicate that carbonate source rocks are mainly developed in the Middle Jurassic Xiali Formation and Upper Jurassic Suowa Formation. Comprehensive studies showed that the Suowa Formation carbonate source rocks have a favorable hydrocarbon-generating potential. The abundance of organic matter in the carbonate rocks is controlled mainly by sedimentary environment and inorganic compounds in the rocks, which is higher in the restricted platform facies than in the open platform facies. Organic carbon contents decrease with increasing CaO contents in the source rocks. 相似文献
20.
《Cretaceous Research》2008,29(1):65-77
The faunas of three previously poorly known and highly fossiliferous limestones from the upper Lower Cretaceous of Texas are dominated by turritelline gastropods. These faunas consist of turritelline-dominated assemblages in the Whitestone Limestone Member of the Walnut Formation in Travis County (middle Albian), the Keys Valley Marl Member of the Walnut Formation in Coryell County (middle Albian), and the Fort Terrett Formation in Kimble County (middle Albian). A fourth high-spired gastropod assemblage in the Segovia Formation in Pecos County (upper Albian) is not dominated by turritellines. Two other turritelline-dominated assemblages in non-carbonate rocks from the Albian and Cenomanian of Texas and Oklahoma are also described. These turritelline-dominated assemblage occurrences add considerably to our knowledge of the facies occurrence of Cretaceous turritelline-dominated assemblages, and they are consistent with the global facies distribution of these assemblages: i.e., although they are widespread in siliciclastic facies from Cretaceous to Recent, turritelline-dominated assemblages in carbonate facies occur almost exclusively in the Cretaceous and Paleogene. 相似文献