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1.
在峡东陡山沱组黑色燧石中前人报道了多种多样的具刺疑源类化石，笔者最近重新研究了陡山沱组岩石切片中的具刺疑源类，发现微化石三维地保存了几乎没蚀变的条件下，这个生物群落包括Filis phaeridi-um,Baltisphaeridium,Comasphaeridium和Tianzhushania等分子，它们中的Tianzhushania在外表及形态上可与产自挪威斯瓦尔巴德群岛晚里菲岩层中的Trachyhstrichosphaera aimika比较，Trachyhystrichosphaera aimika是晚前寒武纪最特殊和分布最广的一个分子，目前已知至少产自世界上15个地区的晚里菲岩层中，对于新古元代前文德地层似乎是一个出色的指示化石，产自陡山沱组的Tianzhushania似乎支持Butterfield的观点，即：陡山沱组硅化碳酸盐沉积的年代早于伊迪卡拉后生物多样化的时期，但是，由于化石只发展于少数岩石薄片中，因此，这些化石或许只代表峡东陡山沱组局部的生态环境。文中还讨论了陡山沱组的沉积环境及化石的保存。 相似文献
2.
本文报道的微体化石产于湖北宜昌樟村坪万家沟剖面埃迪卡拉纪陡山沱组第10层的硅磷质结核中,化石组合包括疑源类Appendisphaera grandis、Ericiasphaera spjeldnaesii、Knollisphaeridium maxi mum、Leiosphaeridia tenuissi ma、Meghystrichosphaeridium perfectum、Tianzhushania polysiphonia、T.spinosa、T.ornata;丝状蓝藻Oscillatoriopsis obtusa、Polytrichoides induviatus、P.lineatus、Salome hubeiensis、Siphonophycustypicum;多细胞藻类Sarcinophycus palilloformis、Wengania minuta。该微体化石组合面貌与黄陵背斜东、南翼陡山沱组二段硅质结核中以大型具刺疑源类Tianzhushania为特征的组合相同,与贵州瓮安地区陡山沱组上磷块岩下部保存的微体化石组合面貌基本一致。 相似文献
3.
4.
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
5.
Pap illomembrana compta在贵州瓮安的发现——兼论陡山沱期大型具刺疑源类的对比及时代 总被引：9，自引：0，他引：9
首次报道贵州瓮安震旦系陡山沱组磷块岩中发现大型具刺疑源类 Papillomembrana compta。对震旦纪陡山沱期已发现的特色硅化或磷酸盐矿化大型具刺疑源类组合及国内外地层对比进行综合评述 ,结合同位素测年、化学地层和其他有关资料综合分析 ,对陡山沱组的年代问题进行探讨。现有研究资料表明 ,陡山沱组含大型具刺疑源类组合的层位应低于俄罗斯北部、澳大利亚、乌克兰、西伯利亚北部及加拿大纽芬兰等地发现多种典型伊迪卡拉期生物群的层位 ,年代应早于以伊迪卡拉期生物群爆发为标志的早期后生动物多样化的时段。 相似文献
6.
V. N. Sergeev N. M. Chumakov M. A. Semikhatov N. G. Vorob’eva 《Stratigraphy and Geological Correlation》2013,21(1):1-7
Microfossils from silicified varieties of cap dolomites crowning the section of the tillite-bearing Lower Vendian (Ediacaran) Churochnaya Formation in the Polyudov Range (North Urals) are characterized. These microfossils are the first to be found from Vendian sections of the region and from all the terminal post-glacial sediments, one of the most significant global glaciation Marinoan of the African Glacial Era, when glaciers reached the equator. They are represented by remains of hormogonian and chrococcacean cyanobacteria as well as possible green filamentous algae. This microbiotic assemblage is of relatively low diversity, being composed of taxa with wide stratigraphic ranges characteristic of Proterozoic conservative microbiotas developed in shallow-water siliceous-carbonate facies. The lack of phytoplanktonic microfossils in this biota including Pertatataka-type acanthomorphic acritarchs or Ediacaran Complex Acanthomorph Palynoflora (ECAP) is also consistent with the conclusion on shallow-water deposition of the Churochnaya Formation. Moreover, most cyanobacteria representatives occurring in the latter are characteristic of shallow-water arid environments that confirm a theory of significant temperature increase during accumulation of the cap dolomites after termination of the above-mentioned glaciation. In addition to these microfossils, the cap dolomite member of the Churochnaya Formation contains filamentous and coccoidal pseudofossils formed under influence of post-sedimentary fluids. In their morphometric parameters, they resemble structures described from Archean sections as microfossil remains, which may be a key to interpreting their nature. 相似文献
7.
Kathleen A. McFadden Shuhai Xiao Chuanming Zhou Micha&#x; Kowalewski 《Precambrian Research》2009,173(1-4):170
Doushantuo acanthomorphic acritarchs are large morphologically complex organic-walled microfossils broadly constrained between the 635 Ma Nantuo glaciation and the 551 Ma Miaohe Biota. They are potential biostratigraphic tools for subdivision and correlation of the Ediacaran System in South China. However, major variations in sedimentary facies and stratigraphic thickness present challenges in understanding the spatial and temporal distribution of these acritarchs. Further, the distribution of acritarchs in the Doushantuo Formation is associated with the presence of early diagenetic chert and phosphate, implying a certain degree of preservational bias and/or environmental control. The purpose of this paper is to document the stratigraphic distribution of Doushantuo acritarchs and to quantitatively evaluate their biostratigraphic significance and possible taphonomic–environmental biases, based on high-resolution paleontological data from six sections over 100 km in the Yangtze Gorges area, South China.A total of 1082 acritarch fossils were recorded from 84 chert horizons in the six sections of the study area. These chert horizons are not uniformly distributed throughout the Doushantuo Formation, thus the presence/absence of early diagenetic chert does play a role in controlling the distribution of acritarchs. The sampled chert horizons can be grouped into two stratigraphic intervals in the lower and upper Doushantuo Formation, respectively, based on regional stratigraphic correlation. Quantitative analysis shows that the two intervals are distinct taxonomically and largely independent of taphonomic or facies controls. Thus, the two intervals can be regarded as assemblage biozones. The lower biozone (biozone 1) is numerically dominated by Tianzhushania spinosa (n = 587; 68.3%) and Meghystrichosphaeridium magnificum (n = 74; 8.6%), whereas the upper biozone (biozone 2) is dominated by Ericiasphaera rigida (n = 104; 47.1%) and Tianzhushania spinosa (n = 34; 14.1%). The three most common genera, Meghystrichosphaeridium, Tianzhushania, and Ericiasphaera, have been identified in all sections. Correspondence analysis (CA), detrended correspondence analysis (DCA), discriminant analysis (DA), and pairwise comparisons of samples (Spearman rank coefficient and Jaccard–Chao index), all consistently support biostratigraphic zonations. Thus, the distribution of the Doushantuo acanthomorphs is primarily controlled by biostratigraphic position of samples, with facies and taphonomic differences playing a secondary role. Our case study suggests that acanthomorphic acritarchs can offer a viable tool for regional correlation of the Ediacaran System. 相似文献
8.
晚新元古代瓮安生物群研究新进展 总被引：2，自引：0，他引：2
产于贵州瓮安，福泉，开阳地区晚新元古代陡山陀期磷块岩中的多细胞藻类，大型带刺疑源类，蓝菌丝状体和细菌化石，球状微体化石，后生动物化石等构成的瓮安生物群是世界上目前发现保存最完美的一个古生物群之一，本文在简单介绍翁安生物群研究现状的基础上，首次批露了笔者近些年来觅获和初步研究的单细胸原生动物，多细胞类海绵动物和类腕足类后生动物等一批新的动物化石资料，为地球早期动物起源，早期生物组织分化，适应辐射，生物多样化和早期海洋生物生态系统提供了珍贵的化石实证材料，此外，还论述了瓮安生物群发现的科学意义。 相似文献
9.
A ca. 600 m thick siliciclastic succession in northern Russia contains abundant and diverse microfossils that document early to middle Ediacaran deposition along the northeastern margin of the East European Platform. The Vychegda Formation is poorly exposed but is well documented by a core drilled in the Timan trough region (Kel’tminskaya-1 borehole). Vychegda siliciclastics lie unconformably above Tonian to lower Cryogenian strata and below equivalents of the late Ediacaran Redkino succession that is widely distributed across the platform. The basal 10 m of the formation preserve acritarchs and fragments of problematic macrofossils known elsewhere only from pre-Sturtian successions. In contrast, the upper, nearly 400 m of the succession contains abundant and diverse large acanthomorphic acritarchs attributable to the Ediacaran Complex Acanthomorph Palynoflora (ECAP). This distinctive set of taxa is known elsewhere only from lower, but not lowermost, Ediacaran rocks. In between lies an additional assemblage of relatively simple filaments and stratigraphically long ranging sphaeromorphic acritarchs interpreted as early Ediacaran in age. Bearing in mind that knowledge of late Cryogenian (post-Strurtian/pre-Marinoan) microfossils is sparse, the Vychegda record is consistent with data from Australia and China which suggest that diverse ECAP microfossil assemblages appeared well into the Ediacaran Period. Accumulating paleontological observations underscore both the promise and challenges for the biostratigraphic characterization of the early Ediacaran Period. 相似文献
10.
贵州瓮安埃迪卡拉（震旦）纪陡山沱期磷酸盐化生物群具有生物多样性特征，包含有蓝菌、多细胞藻类、疑源类、后生动物休眠卵及胚胎、可疑的海绵动物、管状后生动物和微小两侧对称的后生动物等化石类型，是迄今为止全球保存最为完好的晚前寒武纪磷质化石库。瓮安陡山沱组磷质岩提供了早期生命从简单到复杂进化过程中的重要化石记录，展示了埃迪卡拉生物群出现以前早期多细胞生物的生命景观，为研究晚前寒武纪生物圈面貌提供了一个重要的埋葬学窗口。近来，通过醋酸浸解法，在贵州瓮安陡山沱期含磷地层中发现了大量疑似后生动物的实体化石（包含了所有已经报道的类型或与之相似的化石类型）新材料，为了解这些化石的内部构造特征，将一些化石包埋后制作了定向薄片。基于上述化石新材料，结合定向薄片的研究和前人的研究成果，本文详细介绍了瓮安生物群中后生动物化石研究的新进展和存在的问题。 相似文献
11.
贵州台江五河剖面灯影组顶部微体动物化石 总被引：2，自引：0，他引：2
贵州台江灯影组白云岩中发现了30～70μm的锥形微体动物化石,它们具有典型的锥管状、似几丁质壳壁和平行纤维结构等生物结构,可能分属软体动物Carinachitids、Arthrochites、Punctatus、Spondylotubus和似几丁虫类化石等5种类型。其中建立了一新属、种Spondylotubus taijiangensis Yang(gen.etsp.nov.)。在灯影组白云岩中这一类群的发现对研究前寒武纪寒武纪界线附近生物的多样性和生物地层,以及寒武纪生物大爆发都具有一定的科学意义。 相似文献
12.
Yin Chongyu Liu Pengju Stanley M. Awramik Chen Shouming Tang Feng Gao Linzhi Wang Ziqiang Leigh A. Riedman 《《地质学报》英文版》2011,85(2):283-295
Large acanthomorphic acritarchs have been found in chert of the Ediacaran Doushantuo Formation at several localities in South China, including the East Yangtze Gorges of Hubei Province, Weng’an area of Guizhou Province, and elsewhere. However, their potential for biostratigraphic subdivision and correlation of Ediacaran successions is limited by facies control, taphonomic biases, and taxonomic problems. In the Yangtze Gorges, the Doushantuo Formation is generally subdivided into four lithologic members. However, in the Weng’an area, the Doushantuo Formation comprises just a lower and upper part separated by a mid-Doushantuo erosional surface. In the Yangtze Gorges at the Zhangcunping section, the Doushantuo succession is similar to that at Weng’an. So far, the correlation between the Yangtze Gorges and Weng’an area, and elsewhere has been an issue of debate. To resolve the debate, we selected eight sections in the Yangtze Gorges area and systemically sampled chert nodules of the Doushantuo Formation, focusing in particular on the upper Doushantuo Formation. Our data confirm two different assemblages appearing separately in the second and third members, which are separated by a negative δ13C excursion (EN2). The lower assemblage is characterized by Tianzhushania and a diverse suite of large acanthomorphic acritarchs. The upper assemblage is distinguished from the lower assemblage, by (1) absence of Tianzhushania; (2) occurrence of abundant, 100–150 μm, smooth-walled spherical microfossils; (3) occurrence of highly diverse acanthomorphic acritarchs including species extending from the second member and new forms in this member; (4) occurrence of unnamed new forms of protist; and (5) occurrence of the tubular microfossil Sinocyclocylicus guizhouensis. Since the Tianzhushania-dominated assemblage is not present in Australia, it seems that only the upper acanthomorph assemblage is present and thus the lower Doushantuo acanthomorph assemblage is missing in Australia. 相似文献
13.
Purnima Srivastava 《Journal of Earth System Science》2009,118(5):575-582
A highly diversified, advanced and exceptionally well preserved microfossil assemblage, dominated by a planktic community,
has been recorded from petrographic thin sections of chert belonging to the Sirbu Shale Formation, Bhander group, upper Vindhyans,
Rajasthan. Recently, it was noticed that the assemblage also contains well preserved, large-sized acanthomorphic acritarchs,
Trachyhystrichosphaera considered to be an age-marker microfossil of the Cryogenian (850-630 Ma). It is reported for the first time from any Indian
microfossil assemblage of Proterozoic succession. The other microfossils of the Sirbu Shale Formation are: well preserved
simple, small and large-sized sphaeromorphs; complex acanthomorphs, cyanobacterial community; especially a very small-sized
but exceptionally well preserved Obruchevella, a form resembling Volvox colonies; cf. vase-shaped microfossils and morphologies, possibly inclining towards fungal affinity, or lichenlike symbiotic
associations of algae and fungi. Till date, Trachyhystrichosphaera has so far not been reported from successions older than the Tonian (1000850 Ma). It is believed that acanthomorphs attained
maximum size in Ediacaran (630-542 Ma), and further decreased in size in the Cambrian. The global paleontological literature
indicates that Trachyhystrichosphaera ranges in age from Tonian-Ediacaran (1000-542 Ma).
The present record of Trachyhystrichosphaera as well as the earlier studies of micro and megascopic life of the Bhander Group in general and the Sirbu Shale in particular
(aided by the absence of any Cambrian fossil record) indicate that in all possibilities, age of the Sirbu Shale should lie
near Cryogenian (850-630 Ma) and the uppermost Bhander group, may incline towards the Ediacaran (630-542 Ma). 相似文献
14.
贵州瓮安磷矿新元古代微体生物化石 总被引：2，自引：0，他引：2
发现于新元古代陡山沱期的瓮安生物群是一个重要的化石生物群。它的大部分化石保存了较完好的细胞结构、组织分化特征和其他微细构造 ,经描述的属种超过 5 0个。初步研究揭示出地球早期生命漫长的进化过程 ,在距今 6亿年前就已经出现了许多高级后生生物。对瓮安生物群的深入研究将有助于进一步了解早期生命的起源和演化过程。 相似文献
15.
Claudia V. Rubinstein Marco Vecoli Ricardo A. Astini 《Journal of South American Earth Sciences》2011,31(1):124-138
Middle Ordovician acritarchs, including enigmatic, spore-like microfossils, are recorded from the Labrado and Capillas formations, of the Sierras Subandinas (Capillas River Section, Sierra de Zapla), northwestern Argentina. The Sierras Subandinas represent the outermost exposures of the Central Andean Basin that display an alternation of shallow-marine deltaic systems and estuarine environments, where relative sea-level fluctuations are frequent. The scarcity of fossils in the section, due to the marginal marine settings and frequent subaerial exposures, hinders the biostratigraphic constraining of these sedimentary successions. Based on the palynological assemblages, a probably Dapingian age is interpreted for the upper Lagunilla Member of the Labrado Formation, whereas the lower part of the Capillas Formation is assigned to the Darriwilian. Acritarchs from the lower part of the Capillas Formation indicate clear affinities with the “peri-Gondwana province”. However the lack of Frankea, a marker taxa for the Middle Ordovician, could be related either to the intermediate paleolatitudinal position of the Central Andean Basin or to local paleoenvironmental conditions. The facies analysis and the distribution of palynomorph assemblages throughout the studied section, suggest that organic-walled microfossils are influenced by local paleoenvironmental conditions. A probable non-marine origin is proposed for the spore-like microfossils co-occurring within the acritarch assemblages. 相似文献
16.
贵州瓮安磷矿上震旦统陡山沱组地层和沉积环境 总被引：19，自引：0，他引：19
瓮安磷矿当时位于川黔滇台地东南边缘,是我国晚震旦世陡山沱期主要的磷矿之一。该区陡山沱组含磷地层中发现大量低等蓝藻和真菌、红藻、大型球状绿藻、疑源类及可能的后生动物化石,引起国内外地质学家和古生物学家的关注,尤其是最近报道从该地层中发现具细胞结构的海绵和动物胚胎化石,震动了各国古生物学界。瓮安磷矿的陡山沱组不整合于南沱组或板溪群之上,为灯影组浅灰白色白云岩层整合覆盖,以中部的古喀斯特侵蚀面为界而分为下、上两个岩性段,构成下段的白云岩—磷块岩—白云岩序列和上段的磷块岩—白云质生屑磷块岩—磷质白云岩序列。化石产于陡山沱组上段。 相似文献
17.
Neoproterozoic successions in western Shandong of North China Craton contain fine-grained siliciclastic rocks which offer a unique opportunity to explore the Neoproterozoic biosphere. In this study, we have revealed a well-preserved and diversified microfossil assemblage from the Tongjiazhuang Formation, Tumen Group in western Shandong, North China Craton, which is characterized by abundant smooth-walled sphaeromorphic acritarchs and cyanobacterium-like filamentous forms and relatively low abundance of more complex acritarchs. A total of 40 microfossil taxa belonging to 20 morphological genera have been identified, most of which are described for the first time from the Tongjiazhuang Formation of the Tumen Group in western Shandong, including Simia sp., Trachyhystrichosphaera aimika, T. botula, Germinosphaera bispinosa, Unnamed sp. A, Jacutianema solubila, and Pololeptus rugosus. The Tongjiazhuang assemblage revealed in this study is much more diverse than previously reported and well comparable to the Tonian Liulaobei and Gouhou assemblages in the Xuhuai region. Particularly, the occurrence of T. aimika, T. botula, G. bispinosa, J. solubila, and P. rugosus indicates a late Mesoproterozoic to Tonian age for the Tongjiazhuang Formation. In addition, the occurrences of macroscopic carbonaceous compressions, including Chuaria-Tawuia assemblage from the Tongjiazhuang Formation and Tawuia and Sinosabellidites from the Shiwangzhuang Formation, are consistent with geochronological data, suggesting a Tonian age for the Tongjiazhuang, Fulaishan, and Shiwangzhuang formations of the middle and upper Tumen Group, while the Heishanguan and Erqingshan formations of the lower Tumen Group are likely late Mesoproterozoic to Tonian in age. Thus, available biostratigraphic data, lithostratigraphic correlation, and geochronological data suggest that the whole Tumen Group is late Mesoproterozoic to Tonian in age, rather than Cryogenian or Ediacaran. This study significantly improves our knowledge about the diversity of the Tonian biosphere and implies a ∼200–300 million years unconformity (the ‘Great Unconformity’) between the late Mesoprotoerozoic to Tonian Tumen Group and the early Cambrian Liguan Formation in western Shandong. 相似文献
18.
长江三峡地区震旦系的微体植物化石 总被引：1，自引：0，他引：1
《地层学杂志》1986,(4)
<正> 1980年,笔者同余汶、钱逸、王宗哲、侯先光、赵自强等在宜昌莲沱的王丰岗,南沱至石牌村以及秭归县庙河震旦系剖面采集了岩样(图1)。莲沱砂岩和南沱冰碛层中的化石贫乏,仅发现球形疑源类Leiominuschla sp.Protoleiosphaeridium spp.以及一些微体植物残片。陡山沱组微体植物类型多样化,数量可观。有疑源类(acritarchs)的刺球亚类(Acanthomorphitae)的分子,如微刺藻(Micrhystridium),波罗地藻(Baltishaeridium)和毛发藻(Comasphaeridium)等,其中Micrhystridium的数量多至千万计。有晚前寒武纪常见的球形亚类(sphaeromorphitae)的分子外,出现许多具有各种裂口、开口及至口盖的疑源类属种,如Leiosphaeridia?operculia sp.n.,Stictosphaeridium?apertum sp.n.,Paiaeostomc cystis angoformis,Eoaperturilites monoscissus gen. et sp. n., Eo. gonostomus gen. et sp. n., Tasmanites? sp. A。 相似文献
19.
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
20.
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