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  • 11
    Publication Date: 2012-10-13
    Description:    Based on microfacies analyses and sedimentological data, 17 facies are identified within the Middle Miocene carbonates at Siwa Oasis in the northern Western Desert of Egypt. These facies are attributed to five main facies belts. Within these facies and facies belts, five foraminiferal assemblages are recognized. A depositional model relates the reported facies and biofacies to a down-dip depositional profile of an inner to middle carbonate ramp. The facies of the peritidal to restricted lagoon (facies belt 1) and the less-restricted lagoon (facies belt 2) were deposited in the inner ramp behind the barrier/beach shoal facies belt 3. Basinward, lime mudstone of facies belts 4 and 5 accumulated in a proximal to distal middle ramp, respectively. The depositional evolution involved three stages, which are strongly controlled by tectonics and eustatic sea-level changes. The first stage comprises the transgressive Lower Miocene clastic-dominated fluvial facies of the Moghra Formation. The second stage heralds the deposition of the Langhian inner-ramp carbonate and shale facies of the basal Oasis Member of the Marmarica Formation under a relatively high stand of sea level, constrained clastic influx and climate warming. The final stage is represented by Langhian to Serravallian mid-ramp carbonate-dominated facies of the Siwa Escarpment and El Diffa Plateau members under fluctuating sea level, and a westward restriction in clastic supply and water turbidity. Content Type Journal Article Category Original Article Pages 1-24 DOI 10.1007/s10347-012-0332-2 Authors Zaki A. Abdel-Fattah, Geology Department, Faculty of Science, Damietta University, New Damietta City, 34517 Egypt Mahmoud A. Kora, Geology Department, Faculty of Science, Mansoura University, Mansoura, 35516 Egypt Salah N. Ayyad, Geology Department, Faculty of Science, Mansoura University, Mansoura, 35516 Egypt Journal Facies Online ISSN 1612-4820 Print ISSN 0172-9179
    Print ISSN: 0172-9179
    Electronic ISSN: 1612-4820
    Topics: Geography , Geosciences
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  • 12
    Publication Date: 2012-10-01
    Description:    Assessing the role that physical processes play in restricting microbial mat distribution has been difficult due to the primary control of bioturbation in the modern ocean. To isolate and determine the physical controls on microbial mat distribution and preservation, a time in Earth’s history must be examined when bioturbation was not the primary control. This restricts the window of observation primarily to the Precambrian and Cambrian, which precede the development of typical Phanerozoic and modern levels of bioturbation. Lower Cambrian strata of the southern Great Basin, United States, record the widespread development of seafloor microbial mats in shallow shelf and nearshore settings. These microbial mats are recorded by wrinkle structures, which consist of millimeter-scale ridges and sinuous troughs that represent the former presence of a surface microbial mat. Wrinkle structures within these strata occur exclusively within heterolithic deposits of the offshore transition, i.e., between fair-weather wave base and storm wave base, and within heterolithic tidal-flat deposits. Wrinkle structures are not preserved in siltstone-dominated offshore deposits or amalgamated shoreface sandstones. The preservation of wrinkle structures within these environments is due to: (1) the development of microbial mats atop clean quartz-rich sands for growth and casting of the structures; and (2) the draping of the microbial mat by finer-grained sediment to inhibit erosion. The exclusion from offshore deposits may be due to a lack of sufficient sunlight, whereas the restriction from the shoreface is likely due to the amalgamation of proximal tempestites, resulting in the erosion of any incipient microbial mat development. Content Type Journal Article Category Original Article Pages 1-21 DOI 10.1007/s10347-012-0331-3 Authors Scott A. Mata, Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089-0740, USA David J. Bottjer, Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089-0740, USA Journal Facies Online ISSN 1612-4820 Print ISSN 0172-9179
    Print ISSN: 0172-9179
    Electronic ISSN: 1612-4820
    Topics: Geography , Geosciences
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  • 13
    Publication Date: 2012-09-20
    Description:    Halysis is a microfossil found in Ordovician to Devonian shallow-marine carbonates. Up to now, it is only known from thin-sections, and therefore its three-dimensional shape and its systematic position are controversial. Halysis is described as a chain-like microfossil with a shape of the single “chain links” ranging from circular to rounded rectangular. Given that Halysis commonly co-occurs with calcareous algae, it is assumed to also be an alga. Interpretations of the anatomy propose a filiform or tubiform shape. Even a unistratose sheet of cells has been discussed. Since Halysis is comparatively rare, its shape has not been resolved up to now. For the present study, 52 out of several hundred specimens from an Upper Ordovician shallow-water limestone of South China have been investigated in detail, which for the first time offers the opportunity to analyze a great number of sections through Halysis . A three-dimensional computer model of Halysis has been constructed in order to set up planes sectioning the model. These simulated sections have been compared to those from Halysis in thin-sections. The results show that Halysis represents a microfossil with a morphology consisting of parallel juxtaposed, partly branching tubes. A single sheet of cells, which was recently proposed as shape of Halysis , can clearly be excluded. Content Type Journal Article Category Original Article Pages 1-20 DOI 10.1007/s10347-012-0329-x Authors Konstantin Frisch, GeoZentrum Nordbayern, Fachgruppe Paläoumwelt, Loewenichstraße 28, 91054 Erlangen, Germany Axel Munnecke, GeoZentrum Nordbayern, Fachgruppe Paläoumwelt, Loewenichstraße 28, 91054 Erlangen, Germany Christian Schulbert, GeoZentrum Nordbayern, Fachgruppe Paläoumwelt, Loewenichstraße 28, 91054 Erlangen, Germany Yuandong Zhang, State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Nanjing, 210008 China Journal Facies Online ISSN 1612-4820 Print ISSN 0172-9179
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    Topics: Geography , Geosciences
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  • 14
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    In: Facies
    Publication Date: 2012-09-17
    Description:    Ongoing microbialite formation is described at two previously unreported sites in southern Sinai, Egypt. Samples were collected in the peritidal tropical environment of Nabq Bay and Hidden Bay (southern Sinai, Egypt). Field observations and sample analyses show evidence of both sediment trapping and biostabilization in bacterial mucilaginous sheaths and microbially induced mineralization, producing a suite of increasingly lithified material: from agglomerated, consolidated sand to lithified crusts and oncoids. Thin-sections show evidence of bacteria (cyanobacteria and sulphate-reducing bacteria) among the constituent grains in the form of gelatinous filaments (green and red sheaths), and microalgal colonies along the outer edge, accompanied by a very high grade of clast alteration. The alternation of planar to irregular dark, superposed layers, and clastic layers is visible at the surface and/or inside some crusts. Widespread filaments of Schizothrix among grains have been identified, as well as extracellular polymeric substances (EPS), sheaths stabilizing particles, and calcareous tubular encrustations around cyanobacteria filaments. Carbonate precipitates include diffuse micrite, microcrystals of high-Mg calcite precipitating in the EPS matrix, and acicular aragonite as isopachous rims around grains. Cementation is accompanied by partial dissolution and progressive alteration of original grain boundaries. We describe four microbialite categories on the basis of their macroscopic morphology combined with different texture and lithification grade. The occurrence of the southern Sinai microbialites is explained by the interplay of local sedimentary dynamics and accommodation space in a peritidal tropical environment undergoing large temperature and salinity variations. Content Type Journal Article Category Original Article Pages 1-12 DOI 10.1007/s10347-012-0330-4 Authors Daniela Basso, Section of Geological Sciences and Geotechnologies, University of Milano-Bicocca, P.za della Scienza 4, 20126 Milan, Italy Valentina Alice Bracchi, Section of Geological Sciences and Geotechnologies, University of Milano-Bicocca, P.za della Scienza 4, 20126 Milan, Italy Andrea Noemi Favalli, Section of Geological Sciences and Geotechnologies, University of Milano-Bicocca, P.za della Scienza 4, 20126 Milan, Italy Journal Facies Online ISSN 1612-4820 Print ISSN 0172-9179
    Print ISSN: 0172-9179
    Electronic ISSN: 1612-4820
    Topics: Geography , Geosciences
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  • 15
    Publication Date: 2012-09-07
    Description:    The facies development through the stratigraphical interval of the Silurian (late Ludlow) Lau Event and the associated major δ 13 C record excursion have been studied in the Prague Basin. The investigated sections consist of temperate-water carbonates (Kopanina Formation) that were deposited in shallow as well as deeper parts of the basin. In both areas, the facies evolution reflects a major shallowing of sea-level during the early part of the event, which resulted in weathering (karstification) and erosion in the shallower parts of the basin, leading to stratigraphic gaps there. Paleokarst features and dolomitization are associated with these strata in the vicinity of Prague, where the δ 13 C record displays a strong diagenetic overprint and palynomorphs are very poorly preserved. A transition from deep-water shale to subtidal, thick-bedded limestone facies in the deeper parts of the basin, close to Kosov, signals the same sea-level drop, indicating that it was basin-wide. Detailed lithologic descriptions for the studied sections are provided and the development in the Prague Basin is compared with the coeval succession on Gotland, Sweden, which was located in the tropical realm at this times. Content Type Journal Article Category Original Article Pages 1-20 DOI 10.1007/s10347-012-0328-y Authors Martina Gocke, Department of Agroecosystem Research, University of Bayreuth, 95440 Bayreuth, Germany Oliver Lehnert, Universität Erlangen-Nürnberg, Geozentrum Nordbayern, Fachgruppe Krustendynamik, Schlossgarten 5, 91054 Erlangen, Germany Jiří Frýda, Czech Geological Surveym, P.O.B. 85, 118 21 Prague 1, Czech Republic Journal Facies Online ISSN 1612-4820 Print ISSN 0172-9179
    Print ISSN: 0172-9179
    Electronic ISSN: 1612-4820
    Topics: Geography , Geosciences
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  • 16
    Publication Date: 2012-09-03
    Description:    Carbonate deposits from Zrin in the Mt. Zrinska Gora were deposited in the SW part of the Central Paratethys Sea during the Middle Badenian (Middle Miocene). The studied section contains a rich fossil community of non-geniculate coralline red algae (Subfamily Melobesioideae), bryozoans, benthic and planktonic foraminifera, echinoderms, ostracods, molluscs, and calcareous nannoplankton. Based on lithological variations and changes in the biogenic components, four facies associations (FA) are distinguished. Their distribution points to skeletal production and sedimentation on a middle to proximal outer carbonate ramp. The main lithological feature of the section is an alternation of two lithofacies: fully lithified grainstone–rudstone and packstone, and semi-lithified rudstone–floatstone with a carbonate sandy matrix. Depositional environments on the ramp were periodically influenced by minor high-frequency sea-level changes and/or changes of hydrodynamic conditions, which are suggested as the driving mechanisms causing the alternation of the two lithofacies. Vertically in the succession, the two lithofacies alternate to give three thinning- and fining-upward units. The lower part of each unit is formed of a rhodolith and coralline algal FA, which passes upwards into a bryozoan-coralline algal FA and/or FA of bioclastic packstone-grainstone. Based on the vertical upward change in FAs, each unit can be interpreted as a deepening-upward sequence. Patterns in the relative abundance of bryozoan colony growth form (vinculariiform, cellariiform, adeoniform, membraniporiform, celleporiform, and reteporiform), size and abundance of rhodoliths and coralline branches, and benthic foraminifera are interpreted by comparison with data from modern and fossil environments. Based on these data, a water depth range for each FA is interpreted, providing evidence of low-frequency relative sea-level changes. It is hypothesized that relative sea-level fluctuated in the water depth range from 30 to 80 m, and in the uppermost part of the section, rich in planktonic foraminifera and calcareous nannoplankton, possibly deeper. Causes of the low-frequency relative sea-level fluctuations and the general deepening trend observed within the succession cannot be interpreted based on one section; however, they may be related to the subsidence of the depositional basin. The benthic biotic communities are a vertical alternation of rhodalgal and bryorhodalgal associations, and this is attributed to relative sea-level fluctuations. These biotic associations gave rise to warm-temperate carbonates of the Middle Badenian N9 planktonic Zone ( Orbulina suturalis , O. universa ) and NN4–NN5 nannoplankton Zones ( Sphenolithus heteromorphus ). Content Type Journal Article Category Original Article Pages 1-24 DOI 10.1007/s10347-012-0327-z Authors Maja Martinuš, Department of Geology, Faculty of Science, University of Zagreb, Zagreb, Croatia Karmen Fio, Department of Geology, Faculty of Science, University of Zagreb, Zagreb, Croatia Kristina Pikelj, Department of Geology, Faculty of Science, University of Zagreb, Zagreb, Croatia Šimun Aščić, Department of Geology, Faculty of Science, University of Zagreb, Zagreb, Croatia Journal Facies Online ISSN 1612-4820 Print ISSN 0172-9179
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    Topics: Geography , Geosciences
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  • 17
    Publication Date: 2012-09-03
    Description:    Late Jurassic–Early Cretaceous Štramberk-type reef limestones are known from some parts of the Southern Carpathians in Romania. The Upper Jurassic deposits mainly consist of massif reef limestones including a variety of microbialites associated with micro-encrusters. They played an important role in the formation and evolution of the reef frameworks and thus are of significant importance for deciphering the depositional environments. For our study, the most important encrusting organisms are Crescentiella morronensis, Koskinobullina socialis , Lithocodium aggregatum, Bacinella -type structures, Radiomura cautica , Perturbatacrusta leini , Coscinophragma sp., and crust-forming coralline sponges such as Calcistella . Based on microscopic observations, microbial contribution to reef construction is documented by the abundance of dense micrite, laminate structures, clotted, thrombolithic or peloidal microfabrics, constructive micritic cortices, biogenic encrustations and cement crusts, as well as by other types of microbial structures and crusts. Most of the investigated carbonate deposits can be classified as “coral-microbial-microencruster boundstones” which are characteristic for the Intra-Tethyan domain. Their paleogeographical significance is indicated by the presence of many features comparable with carbonate deposits of rimmed platform systems from the Northern Calcareous Alps or Central Apennines. Based on the distribution of the facies and facies associations within the carbonate sequences under study we can distinguish slope and external shelf margin environments. The microbial crusts, the encrusting micro-organisms, and in some cases the syndepositional cements have stabilized and bound the carbonates of the slope facies types. Subsequently, the stable substrate favored the installation of coral-microbial bioconstruction levels. Content Type Journal Article Category Original Article Pages 1-30 DOI 10.1007/s10347-012-0325-1 Authors George Pleş, Department of Geology, Babeş-Bolyai University, M. Kogălniceanu 1, 400084 Cluj-Napoca, Romania Cristian V. Mircescu, Department of Geology, Babeş-Bolyai University, M. Kogălniceanu 1, 400084 Cluj-Napoca, Romania Ioan I. Bucur, Department of Geology, Babeş-Bolyai University, M. Kogălniceanu 1, 400084 Cluj-Napoca, Romania Emanoil Săsăran, Department of Geology, Babeş-Bolyai University, M. Kogălniceanu 1, 400084 Cluj-Napoca, Romania Journal Facies Online ISSN 1612-4820 Print ISSN 0172-9179
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    Topics: Geography , Geosciences
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  • 18
    Publication Date: 2012-08-25
    Description:    The Carnian Pluvial Event was followed by extreme aridity around the Mediterranean region, but the relationship between these climatic modes and the evaporite deposits of the north Arabian margin has not been established. The Mohilla Formation in Israel was deposited on the rifted Levant margin of the Neotethyan seaway during the Carnian (Late Triassic). The lowermost member, M1 (carbonate, shale, minor evaporite), records sea-level and climate change of the transition from open-marine deposits to the thick evaporite of the overlying M2 member. Field, petrographic and cathodoluminescence investigation of the M1 member exposed at Makhtesh Ramon, southern Israel, enabled tracking of changing paleoenvironments. The M1 member can be subdivided into six sea-level controlled sedimentary cycles, each terminating in subaerial exposure. Open-marine, lagoonal, and supratidal belts are represented, but environments become increasingly restricted upwards. Three of the exposure horizons are marked by well-developed early diagenetic features, including dissolution porosity and meteoric cements. These changing facies belts and the superposed diagenetic modes formed under an oscillating climate regime of three relatively humid episodes dominated by deposition of carbonate, alternating with evaporitic sediments indicating aridity. Deposition of the M1 member can be correlated with the transition in the western Tethys from the Carnian pluvial episode to aridity. This transition in the Levant region is characterized by an oscillatory climate that culminated in a thick evaporite unit from the extreme arid phase. The oscillations may be attributed to shifting global climate belts, overprinted by monsoonal strengthening and weakening, in the equatorial belt. Content Type Journal Article Category Original Article Pages 1-23 DOI 10.1007/s10347-012-0321-5 Authors Or M. Bialik, Department of Geological and Environmental Sciences, Ben-Gurion University, Beer Sheva, 84105 Israel Dorit Korngreen, Geological Survey of Israel, 30 Malkhe Israel St., Jerusalem, 95501 Israel Chaim Benjamini, Department of Geological and Environmental Sciences, Ben-Gurion University, Beer Sheva, 84105 Israel Journal Facies Online ISSN 1612-4820 Print ISSN 0172-9179
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    Topics: Geography , Geosciences
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  • 19
    Publication Date: 2012-08-23
    Description:    In the Julian Alps (Mt. Prisojnik, NW Slovenia) and in the Kamnik–Savinja Alps (Mt. Križevnik, N Slovenia), both of which form part of the eastern Southern Alps, several meters of Upper Anisian pelagic red nodular, radiolarian-rich limestone (Loibl Formation) were deposited on the drowned platform carbonates of the Contrin Formation. The time of the platform drowning is dated with radiolarians and conodonts to the Illyrian, more precisely to the upper part of the Paraceratites trinodosus Ammonoid Zone. The red limestone is overlain by pyroclastics and volcanics (rhyolites) or carbonate (mega)breccia (Uggowitz Formation). The following unit consists of thin-bedded limestone, grainstone and subordinate marl (Buchenstein Formation) deposited during the final filling of the basin from the adjacent prograding carbonate platform (Schlern Formation) in the Ladinian. Map-scale geometry, neptunian dykes, the onset of volcanism, the presence of (mega)breccia and related paleo-escarpments, the lateral variations in thickness and the wedge-shaped geometry of the lithological units provide evidence of syn-sedimentary block faulting and the formation of small-scale, relatively shallow half-grabens within the previously uniform Slovenian Carbonate Platform. This analysis indicates a clear tectonic control over the development of the Middle Triassic stratigraphy. The described extensional event is well correlated and genetically connected with the syn-rift formation of the neighboring Slovenian Basin and other Southern Alpine basins that formed in connection with the opening of the Meliata-Maliac branch of the Neotethys Ocean. Content Type Journal Article Category Original Article Pages 1-28 DOI 10.1007/s10347-012-0326-0 Authors Bogomir Celarc, Geological Survey of Slovenia, Dimičeva ulica 14, 1000 Ljubljana, Slovenia Špela Goričan, Ivan Rakovec Institute of Paleontology, ZRC SAZU, Novi trg 2, 1000 Ljubljana, Slovenia Tea Kolar-Jurkovšek, Geological Survey of Slovenia, Dimičeva ulica 14, 1000 Ljubljana, Slovenia Journal Facies Online ISSN 1612-4820 Print ISSN 0172-9179
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  • 20
    Publication Date: 2012-08-20
    Description:    Neomeris (Lamouroux, 1816 ) is an extant taxon, the origin of which can be tracked back into Early Cretaceous times. The introduction of a new mid-Cretaceous species from Brazil, i.e., Neomeris srivastavai n. sp., offers the opportunity to review the subdivision of the genus into three subgenera, to complete the catalogue of the fossil calcareous algae of Brazil, and to point out the huge stratigraphic gap and lack of documentation between the first occurrence of the dasycladacean model of reproduction, i.e., choristospory, and the oldest record so far known of an undescribed fossil Neomeris (from Portugal). Content Type Journal Article Category Original Article Pages 1-10 DOI 10.1007/s10347-012-0322-4 Authors Bruno Granier, Département des Sciences de la Terre et de l’Univers, UFR des Sciences et Techniques, Université de Bretagne Occidentale (UBO), 6 avenue Le Gorgeu, CS 93837, 29238 Brest Cedex 3, France Dimas Dias-Brito, Departamento de Geologia Aplicada, UNESPetro, Universidade Estadual Paulista, Rio Claro, IGCE, Caixa-Postal 178, av. 24 A 1515, Bela Vista, Rio Claro, SP 13506-900, Brazil Ioan I. Bucur, Department of Geology, Babeş-Bolyai University, Str. M. Kogalniceanu nr.1, 400084 Cluj-Napoca, Romania Journal Facies Online ISSN 1612-4820 Print ISSN 0172-9179
    Print ISSN: 0172-9179
    Electronic ISSN: 1612-4820
    Topics: Geography , Geosciences
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