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Methane-derived carbonate conduits from the late Aptian of Salinac (Marne Bleues, Vocontian Basin, France): Petrology and biosignatures
No full textPeculiar carbonate bodies occur in distinct marl layers of the Marnes Bleues Formation (Aptian-Albian, Vocontian Basin, Southern France). The carbonate conduits exhibit pipe- or sausage-like forms and a central channel. Their sizes range between 30 and 60 cm in length and 5-10 cm in diameter. The conduit carbonates consist of automicrite authigenically formed within the sediment. Millimeter-sized aggregates of framboidal pyrite are abundant within the conduit automicrites, probably representing former colonies of sulfate reducing bacteria. The central channel reflects former pathways of reduced fluids in the carbonate conduit. Ni-enrichments at the margins of the central cavity are may be due to the activity of methane-related metabolism as Ni is an important bio-element for respective microbes. Light stable carbon isotope ratios of the conduit automicrites (-25.86 parts per thousand, to -23.10 parts per thousand, VPDB) point to carbonate precipitation linked to anaerobic oxidation of methane (AOM), while less depleted stable carbon isotope ratios of microspar in marginal zones of the central opening (-8.96 parts per thousand VPDB) are in line with microbial sulfate reduction. A methane-related origin of the conduit carbonates is confirmed by the presence of authigenic lipid biomarkers tentatively sourced by archaea most of which are characterized by strong C-13 depletions (delta C-13 values down to -104 parts per thousand). The presence of organically bound sulfur is well in line with microbial sulfate reduction. Isorenieratane potentially point to the presence of brown pigmented green sulfur bacteria. The methane was probably sourced by older OAE black shales which are known to contain isotopically (delta C-13) heavy biomarkers of archaea as reported elsewhere. (C) 2015 Elsevier Ltd. All rights reserved
Organic Compounds and Conditioning Films Within Deep Rock Fractures of the aspo Hard Rock Laboratory, Sweden
No full textPalaeoproterozoic grano-dioritic rocks of the island of aspo exhibit several mineralized fracture generations mainly filled by quartz, calcite, fluorite and/or epidote. Manganese-rich calcite fractures of probably Palaeozoic age are related to younger, possibly Pleistocene/Holocene cracks formed during the last ice age and successive crustal uplift, in contact to the host rock, which are sometimes associated with organic matter. Signals of organic molecules could be gained on the corresponding phase boundaries with Raman spectroscopy, likewise HPLC and HPAE-PAD reveal the presence of carbohydrates and amino acids in bulk rock samples. It is supposed that most of the preserved organic matter is related with thin conditioning films. Extracted bacterial and fungal DNA from the grano-dioritic rocks indicates still active microbial activity in fracture micro-niches.German Research Foundation [DFG - FOR 571, 48, Re 665/27-3
Outcrop analogues of pockmarks and associated methane-seep carbonates: A case study from the Lower Cretaceous (Albian) of the Basque-Cantabrian Basin, western Pyrenees
No full textLate Albian deep-water sediments of the Black Flysch Group in the Basque-Cantabrian Basin (western Pyrenees) preserve a fossil pockmark field including methane seep carbonates and associated macrofauna. The geometry of the pockmarks is reconstructed from repeated lens-shaped turbidite deposits with centrally located carbonate bodies. Early diagenetic carbonate phases such as clotted micrite and yellow calcite with delta C-13 values as low as -41.6%, and hydrocarbon biomarkers (e.g. 2,6,10,15,19-pentamethylicosane) with strong depletions in C-13 indicate that the carbonates precipitated due to anaerobic oxidation of methane. The pockmarks probably formed due to subsidence induced by dewatering and degassing of the gas-charged seabed perhaps enhanced by the weight of the carbonate bodies. The macrofauna resembles that of other late Mesozoic deep-water methane-seeps world-wide, and is dominated by large lucinid and Caspiconcha bivalves, and hokkaidoconchid gastropods. During late diagenesis the carbonate delta O-18 values were reset to a narrow range of -12 to -10%., the remaining pore spaces and fissures were filled with pyrobitumen, and additional carbonate phases precipitated, potentially due to thermochemical sulfate reduction processes. (C) 2012 Elsevier B.V. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Isolation of Anaerobic Bacteria from Terrestrial Mud Volcanoes (Salse di Nirano, Northern Apennines, Italy)
No full textTerrestrial mud volcanoes and salses are unique inland sites of methane and saline water seepage, driven by tectonic pressure and methane from deep subsurface oil reservoirs. These structures are mainly found in active nappe tectonic zones, like in the foothills of the Northern Apennines. Fluid samples, taken anaerobically from the Nirano mud volcano field located in the foreland of the Northern Apennines, contain low numbers of bacterial cells. Representative strains were enriched under anaerobic conditions in culture media based on the composition of the mud volcano fluid. Anaerobic fermentative organisms, partially involved in cycling of sulfur compounds, namely Desulfovibrio and clostridial strains, were enriched and isolated. Two isolates of Clostridium thiosulfatireducens- and Desulfovibrio psychrotolerans-related strains were retrieved from enrichment cultures. Isolated sulfate reducers form aggregates, composed of bacterial biomass, extracellular polysaccharides and a mineral matrix. Besides some typical "contaminants" from topsoil, the Nirano mud volcano fluids contain culturable bacteria related to organisms typical for other sediments of saline systems and/or oil reservoirs
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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