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1.
V. N. Sergeev N. G. Vorob’eva P. Yu. Petrov 《Stratigraphy and Geological Correlation》2007,15(1):1-11
Excellently preserved organic-walled and silicified microfossils are first found in the Lower Riphean Ust-Il’ya and Kotuikan formations of the Billyakh Group in the northern slope of the Anabar Uplift (the Fomich River basin). Similar assemblages were previously known only from sections located southward in the Kotuikan River basin, and taxonomic composition of organic-walled microbiotas from the Ust-Il’ya and Kotuikan formations became a corner stone in competitive microphytological models that are based on different approaches. In their composition and general appearance, microbiotas from the Kotuikan and Ust-Il’ya formations in the Fomich River basin are similar to microbiotas reported from the Kotuikan River basin, although northern sections of the above formations characterize deeper sedimentation settings than in localities known before. The Ust-Il’ya and Kotuikan assemblages of organic-walled microfossils include sphaeromorphic Chuaria circularis and Leiosphaeridia, two-layer vesicles the genus Simia, filamentous Plicatidium and Taenitrichoides, and some others. The silicified microbiota from the lower Kotuikan Subformation is largely composed of akinetes of Anabaena-like cyanobacteria Archaeoellipsoides, spherical Myxococcoides grandis, and short trichomes Filiconstrictosus and Orculiphycus representing initial germination stages of Anabaena-like cyanobacterial spores. Acanthomorphic acritarchs known from lithology-similar Lower and Middle Riphean (Mesoproterozoic) formations of Australia and China have not been observed in the Ust-Il’ya and Kotuikan microbiotas, which are probably of older age. The found microbiotas outline substantially wider distribution area of organic-walled and silicified microfossils, supplement microphytological characteristics of Riphean sediments in the Anabar Uplift, provide information on taxonomic composition of microbiotas from a wider spectrum of facies, and specify relationships between Early and Middle Riphean assemblages of microorganisms from different continents. 相似文献
2.
A microfossil assemblage has been detected in phosphorite cherts from the Dengying and Meishucun Formations (610 Ma) of the Sinian System in Jinning County, Yunnan Province, southwest China.A unique type (mode) of microfossil preservation — collophanite or apatite, or even in rare cases, chert-replacement — is reported here for the first time.The size frequency statistics for the assemblage are consistent with the results obtained by Schopf. The assemblage includes 18 genera and 20 species, among which 4 genera and 10 species are new. The assemblage consists of solitary and colonial spheroidal cells and septate or non-septate filaments, mainly Cyanophyta, especially Chroococaceae, Oscillatoriaceae and Nostocaceae.The microfossils described are Bigeminococcus grandis n. sp., Myxococcoides kingii, Myxococcoides grandis, Palaeoanacystis vulgaris, Archaeophycus venustus n.g. et sp., Eomycetopsis robusta, Circulinema jinningense n.g. et sp., Circulinema muirae n.g. et sp., Cyanonema infliatum, Obruchevella parva, Oscillatoriopsis awramikii n. sp., Palaeolyngbya oehlerii n. sp., Palaeolyngbya spiralis n. sp., Palaeotubulus lamellosus n.g. et sp., Veteronostocale sp. 1, Veteronostocale sp. 2, Allantomorphus septatus n.g. et sp., Clonophycus vacus n. sp., Archaeotrichion contortum, Rhienonema antiquum, Micrhystridium setulerum and Protosphaeridium densum. 相似文献
3.
Rupendra Babu Veeru Kant Singh Naresh Chandra Mehrotra 《Journal of the Geological Society of India》2014,84(4):442-448
An assemblage of structurally preserved organic-walled microfossils (OWMs) from the macerated residue of black carbonaceous shale belonging to Saradih Formation, the youngest carbonate horizon of the Raipur Group, Chhattisgarh Supergroup exposed at on the right bank of Mahanadi River, NE of Sarangarh township in Raigarh district, Chhattisgarh is being reported for the first time. The assemblage is comprised of 19 taxa of 13 genera belong to eukaryotes and prokaryotes viz. Leiosphaeridia, Stictosphaeridium, Dictyotidium, Synsphaeridium, Symplassosphaeridium, Satka, Trachysphaeridium, Goniosphaeridium, Trachyhystrichosphaera, Vandalosphaeridium, Siphonophycus, Oscillatoriopsis and Polythrichoides. The comprehensive account of recovered microbiotic assemblage can be correlated with globally known Neoproterozoic (early Cryogenian) assemblages, deposited in tidal complexes of shallow sea. 相似文献
4.
5.
Roger Buick 《Precambrian Research》1984,24(2):157-172
A sample of chert from North Pole in the Archaean Pilbara block of Western Australia contains carbonaceous filaments that resemble microfossils. These occur in alternating light and dark laminae that look stromatolitic. However, the filaments are too simple in form for their origin to be determined, so they should be regarded as dubiofossils, perhaps biogenic, perhaps inorganic. Their host laminae were inorganically precipitated in a concordant fissure and thus cannot be stromatolitic. This fissure is younger than the surrounding silicified sediments of the ca. 3500 Ma old Warrawoona Group and possibly formed towards the end of the uplift and associated fracturing of the North Pole Dome, perhaps ca. 2750 Ma ago. The filaments are therefore contaminants in secondary chert.The filament-bearing rock was collected less than a metre from one of the localities (B) from which Awramik et al. reported early Archaean microfossils and possible microfossils. Their filaments from this locality were almost identical to those described here and were found in similar laminae. This suggests that their locality B filaments may also be contaminants in secondary chert. Other filaments found by Awramik et al. at North Pole come from an imprecisely located sample site (locality A) where the rock relationships are unknown. Since the host laminae of these filaments are not demonstrably primary and as cryptic concordant fissures filled with secondary minerals are common in locality A rocks, the filaments from this sample site could be contaminants too. Those that were assigned to Archaeotrichion should be treated as dubiofossils. Thus, the filaments described by Awramik et al. may not be fossil bacteria in ca. 3500 Ma old stromatolites, as they proposed, and are not necessarily the oldest known fossil organisms, as has been claimed. 相似文献
6.
《Precambrian Research》1985,28(2):163-173
Eight categories of organic-walled coccoid microfossils in the c. 700-Ma-old Doushantuo Formation are described and named. Of these, one genus and species (Paratetraphycus giganteus) is new. Most of the microfossils are interpreted as being the remains of the Chroococcaceae and are morphologically comparable to those of the 650-Ma-old Yudoma microbiota and the 850-Ma-old Bitter Springs microbiota. These microfossils occur in non-stromatolitic cherts, adding preservational information to the study of Precambrian life. 相似文献
7.
Imad Mahmood Ghafor Kamal Haji Karim Varrojan Sissakian 《Arabian Journal of Geosciences》2014,7(9):3599-3610
Oligocene and Lower Miocene sediments from High Folded Zone of Iraqi Zagros have been studied paleontologically at south of Sulaimaniyah, Kurdistan Region, NE Iraq. The identified fauna are consisted of (25) genera and species of benthonic and (16) species of planktonic foraminifera. The fauna comprises relatively abundant foraminiferal assemblages of moderate diversity. Based on the stratigraphic distribution of these species, two biozones have been recognized which are Nummulites—Rotalia and Globoquadrina dehiscens zones. These biozones indicate that the studied sections of Basara and Khewata are of Late Oligocene–Early Miocene age. Based on the microfossils, it has been found that the age of sediments is equivalent to or represents Anah and Serikagni Formations. Some previous studies described Oligocene rocks (Kirkuk Group) as interior sag basin. In the present study, the occurrence of the group inside High Folded Zone and its rich fauna content are used for the discussion of the sag basin versus normal marine water. 相似文献
8.
M. E. Mel’nikov S. P. Pletnev I. A. Basov T. A. Punina T. E. Sedysheva V. D. Khudik Yu. D. Zakharov 《Russian Journal of Pacific Geology》2007,1(3):257-264
New materials obtained in the Pacific during cruises of the R/V Gelendzhik carried out by the State Scientific Center Yuzhmorgeologiya in 2000–2001 make it possible to specify the geologic and geomorphologic structure of Alba Guyot and clarify lithological and paleontological characteristics of lithotectonic rock complexes ranging from the Early Cretaceous to Pleistocene in age. Based on macro-and microfossils from sedimentary rocks several “transgressive” phases are distinguished in the guyot development: Cenomanian-Turonian, late Campanian-Maastrichtian, late Paleocene-middle Eocene, and Late Cenozoic. Finds of Paleogene molluscan and coral remains, together with planktonic foraminifers, imply relatively shallow sedimentation settings on Alba Guyot during the early Paleocene. 相似文献
9.
The sulphide-bearing rocks of the Upper Cretaceous Germav Formation in southeastern Turkey (Bozova–Urfa) and the morphologically varied sulphide occurrences they contain have been investigated. Pyrite and marcasite are the main sulphide minerals; lesser bravoite and millerite also occur. Pyritised branches and leaves, trace fossils, and animal microfossils and macrofossils are abundant. Most of the concretionary and authigenic concretionary pyrite occurrences are probably related to burrows. The concretionary pyrites have low Co and high Ni contents and low Co:Ni ratios. The pyrite-rich lithostratigraphic sequences were deposited in a deep-sea environment, and pyrite mineralization developed in syn-sedimentary, early diagenetic and epigenetic stages under anoxic conditions. To cite this article: C. Bölücek, B. Ilhan, C. R. Geoscience 338 (2006). 相似文献
10.
The microfossil assemblages of subsurface Carboniferous rocks from Faghur-1x were examined and identified. Their biostratigraphical and paleoenvironmental importance were investigated. The assemblage included well-preserved foraminifera like Omphalotis omphalota, Omphalotis sp. 2, Omphalotis sp. 3, Paraarchaediscus stilus, Paraarchaediscus koktjubensis, Archaediscus krestovnikovi, Archaediscus complanatus, Archaediscus inflatus, Archaediscus karreri, Diplosphearina inequalis, Eotubertina sp., Tetrataxis conica, Cribrostomum lecomptei, Palaeotextularia angulata, and Palaeotextularia longiseptata. This foraminiferal association indicates the late Viséan-early Serpukhovian. The other microfossils are gastropods, brachiopods, ostracods, crinoidal ossicles, frond-like fenestrate bryozoan types and stick-like colonies, echinoderms, microproblematica like Draffania biloba and algal Calcisphaera and the dasyclad Koninckopora. This microfossils assemblage points to the deposition in a restricted to open platform in a lagoonal framework environment. The Tehenu Basin is the eastern segment of northern African Sahara basins that provided refuge for the foraminiferal genera through the mass extinction events during the glacial Viséan-Serpukhovian times. However, its foraminiferal associations have lower diversities than the western basins, which indicate that it was more readily affected by the mass extinction event. 相似文献
11.
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
12.
Vertebrate remains from the Upper Cretaceous (Santonian) Ajka Coal Formation (Bakony Mountains, western Hungary) are described. Macro- and microfossils collected from two boreholes and from isolated chunks of sediment/matrix dumped on spoil heaps of the Jókai Mine represent pycnodontiform and lepisosteiform fishes, bothremydid turtles, the mosasauroid Pannoniasaurus inexpectatus, the crocodyliforms cf. Theriosuchus, Iharkutosuchus makadii and cf. Allodaposuchus, as well as ankylosaurian and theropod dinosaurs. This unit was deposited in a swampy lacustrine environment, in contrast with the neighbouring and contemporaneous floodplain deposit of the vertebrate-bearing Csehbánya Formation at Iharkút. Despite significant environmental differences, the faunal composition of the Ajka Coal Formation assemblage completely overlaps with that of the Csehbánya Formation, suggesting the occurrence of the same semi-aquatic and terrestrial species in both settings. The ankylosaurian remains further strengthen the previous view that ankylosaurus preferred wetland habitats such as fluvial systems and coastal regions. 相似文献
13.
Freshwater chlorophycean algae in recent marine sediments of the Beaufort, Laptev and Kara Seas (Arctic Ocean) as indicators of river runoff 总被引：3，自引：0，他引：3
Jens Matthiessen Martina Kunz-Pirrung Peta J. Mudie 《International Journal of Earth Sciences》2000,89(3):470-485
Freshwater chlorophycean algae are characteristic organic-walled microfossils in recent coastal and shelf sediments from the Beaufort, Laptev and Kara seas (Arctic Ocean). The persistent occurrence of the chlorophycean algae Pediastrum spp. and Botryococcus cf. braunii in marine palynomorph assemblages is related to the discharge of freshwater and suspended matter from the large Siberian and North American rivers into the Arctic shelf seas. The distribution patterns of these algae in the marine environments reflect the predominant deposition of riverine sediments and organic matter along the salinity gradient from the outer estuaries and prodeltas to the shelf break. Sedimentary processes overprint the primary distribution of these algae. Resuspension of sediments by waves and bottom currents may transport sediments in the bottom nepheloid layer along the submarine channels to the shelf break. Bottom sediments and microfossils may be incorporated into sea ice during freeze-up in autumn and winter leading to an export from the shelves into the deep sea. The presence of these freshwater algae in sea-ice and bottom sediments in the central Arctic Ocean confirm that transport in sea ice is an important process which leads to a redistribution of shallow water microfossils. 相似文献
14.
A. L. Ragozina D. Dorjnamjaa E. A. Serezhnikova L. V. Zaitseva B. Enkhbaatar 《Stratigraphy and Geological Correlation》2016,24(3):242-251
The Vendian (Ediacaran) beds of the Zavkhan Basin, in the upper part of the Tsagaanolom Formation (<632 ± 14 Ma), yielded a new “Zavkhan” association of algae, microfossils, and problematic organisms, which is established in the series of alternating chert-carbonate shale with phosphorite interbeds. This association is distinct in the predomination of large (250 μm and over) sphaeromorphic microfossils of the genera Tasmanites, Archaeooides, and Leiosphaeridia, whereas acanthomorph acritarchs are represented by rarely found Cavaspina sp. and Tanarium sp. Multicellular algae included fragments of encrusting or foliate thalli with pseudoparenchymatous structure of polygonal cells characteristic of Rhodophyta algae (Thallophycoides sp.), and cordlike thalli of Vendotaenid algae Tyrasotaenia podolica. These layers of siltstone contain imprints of the problematic Vendian macrofossil Beltanelliformis brunsae. In their stratigraphic position, chemostratigraphic data, and fossil assemblage, the “Zavkhan” association can be assigned to the Upper Vendian. 相似文献
15.
Zhang Yun 《Precambrian Research》1985,30(3):277-302
A relatively diverse microbiota, preserved in-situ, has been discovered in cherty stratiform stromatolites of the middle Proterozoic Wumishan Formation (c. 1200–1300 Maold), Jixian Group, in the Ming Tombs area of Beijing. This microfossil assemblage consists of two parts: (1) the mat-building and mat-dwelling benthos which mostly belong to “long-lasting” taxa and are mostly common with those of other Proterozoic microbiotas; and (2) allochthonous elements including some plankton and peculiar structures which are either new forms first described here or taxa shared with some contemporaneous or penecontemporaneous microbiotas elsewhere. The latter may have more stratigraphic significance.Bivariate analysis on two characters measured (length and width) has been used in the classification of the elongate microfossils, and the results demonstrate that biometrical methods are effective in the taxonomy of some Precambrian microfossils.The following new taxa are described:Archaeoellipsoides obesus sp. nov., Archaeoellipsoides conjunctivus sp. nov., Bactrophycus oblongum gen. et sp. nov., Bactrophycus dolichum gen. et sp. nov., Callosicoccus crauros gen. et sp. nov. 相似文献
16.
The occurrence, types, morphology, and mineralogical characteristics of tube microfossils were studied in gossanites from twelve VHMS deposits of the Urals. Several types of tube microfossils were recognized, including siboglinids, polychaetes and calcerous serpulids, replaced by a variety of minerals (e.g. hematite–quartz, hematite–chlorite, carbonate–hematite) depending on the nature of the substrate prior to the formation of the gossanites. Colonial hematite tube microfossils (~ 150 μm across,1–2 mm long) are composed of hematitic outer and inner walls, and may exhibit a cellular structure within their cavities. Spherical forms are saturated with Fe-oxidizing bacteria inside the tubes – probably analogues of trophosomes. Colloform stromatolitic outer wall surfaces are characterized by the presence of numerous interlaced filaments of hematite (2–3 μm diameter, up to 1–2 mm long). Between tube microfossils, the hematitized cement contains bundles of hematitized filaments with structures similar to the hyphae of fungi. Hematite–chlorite tube microfossils are scattered in gossanites, mostly as biological debris. They are typically 30 to 300 μm in diameter and 1 to 5 mm long. The layered structure of their tube walls is characterized by hematite–quartz and chlorite layers. Abundant filamentous bacteria coated by glycocalix and chlorite stromatolite are associated with hematite–chlorite tubes. The carbonate–hematite tube microfossils (up to 300 μm across, 2–3 mm long) occur in carbonate-rich gossanites. The tubes are characterized by fine (~ 10 μm thick) walls of hematite and cavities dominated by relatively dark carbonate or hematite. Carbonates may be present both in walls and cavities. Stromatolite-like leucoxene or hematite–carbonate aggregates were also found in association with tubes. Randomly oriented filaments are composed of ankerite. Single filaments are composed of individual cells, typically smaller than 100 nm across, similar to that of magnetotactic bacteria.Three dimensional tomographic images of all types of tube microfossils demonstrate a clear wavy microlayering from outer and inner walls, which may reflect segmentation of the tube worms. The traces of burrowing or fragments of glycocalix with relict spheres are typical of tube microfossils from gossanites.The carbon isotopic composition of carbonates associated with tube microfossils from hematite–quartz, hematite–carbonate, and hematite–chlorite gossanites average − 7.2, − 6.8, –22.8‰, PDB, respectively. These values are indicative of a biogenic origin for the carbonates. The oxygen isotopic composition of these carbonates is similar in all three gossanite types averaging + 13.5, + 14.2, + 13.0‰ (relative to SMOW), and indicative of active sulfate reduction during the diagenetic (and anadiagenetic) stages of the sediments evolution. The trace element characteristics of hematite from tube microfossils are characterized by high contents of following trace elements (average, ppm): Mn (1529), As (714), V (540), W (537), Mo (35), and U (5). Such high contents are most likely the result of metal and metalloid sorption by fine particles of precursor iron hydroxides during the oxidation of sulfides and decomposition of hyaloclasts via microbially-mediated reactions. 相似文献
17.
Calpionellids and chitinoidellids were identified from exotic limestone clasts occurring in flysch deposits of the Early Cretaceous to Oligocene age from the Silesian and Subsilesian nappes of the Polish Outer Carpathians. They represent the remnants of carbonate sedimentation along the northern and southern margin of the Severin-Moldavidic Basin, areas which are no longer preserved on the surface. Chitinoidellid and calpionellid assemblages characterize the Chitinoidella, Crassicollaria and Calpionella zones (latest early Tithonian–early Berriasian). The calpionellid zonation for the Western Carpathians was used for the present study, but some difficulties were encountered resulting from the application of this zonation. Cathodoluminescence imaging (CL) was useful for the identification of these microfossils in samples containing sparse and poorly preserved specimens, especially in the studied shallow-water limestone (the so-called Štramberk-type limestones). 相似文献
18.
Pier L. Binda 《Precambrian Research》1977,4(3):285-306
Lower Kundelungu black argillites and silty dolomicrites from the Ndola area contain a rich microfossil assemblage, of which several forms can be attributed to the form-genus Fibularix Pflug, 1965. The same assemblage has also been found in fine-grained, mildly metamorphosed sedimentary rocks from Kalengwa and Karibarembi (North-Western Province). These findings support the Kundelungu correlation of the Kalengwa and Karibarembi successions.Three new species of Fibularix are described and illustrated. Seven types of sphaeromorphs are described and illustrated, though treated informally. Some sphaeromorphs are detached parts of Fibularix chains.The Lower Kundelungu microfossils resemble very closely some palynomorphs that occur in the Brioverian (Late Precambrian) of France, in the Libby Formation (Belt) of the northwestern United States, and in other formations of Late Precambrian age. 相似文献
19.
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
20.
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