1,720,962 research outputs found
The Pliocene-age Stirone River hydrocarbon chemoherm complex (Northern Apennines, Italy)
No full textThe Stirone River section in the Italian Northern Apennines hosts a rare example of Pliocene age
hydrocarbon-imprinted carbonates in the Mediterranean Basin associated with deep-water hemipelagic
lithologies. These include meter-sized, dolomite-cemented chimneys, micritic brecciated limestones,
lucina-mudstones and chemosymbiotic bivalve shells. Some such chimneys show d13C values as low
as 37.5‰ VPDB, suggesting subsurface precipitation of authigenic dolomite induced by anaerobic
oxidation of methane triggered by consortia of sulphate reducing bacteria. These carbonates are interpreted
as part of the plumbing system related to hydrocarbon expulsion onto the seafloor, resulting from
hydrocarbon-enriched defluidization processes dated at an interval at 3.6e3.3 Ma and associated with
the thrust-related “Salsomaggiore structure”
Chronostratigraphic distribution of cetaceans in the Pliocene of Northern Apennines (Italy): palaeoecological implications
No full textA large number of cetacean fossils have been recovered through the time from the Pliocene deposits in Northern Apennines thrust belt, on both the Padan-Adriatic and the Tyrrhenian side. In this work, the cetaceans of Castell'Arquato Basin (Padan-Adriatic side) have been placed within a high-resolution chronostratigraphic framework available for this area. This results in a better assessment of their evolutionary history and of the palaeoecologic factors controlling their diversity and abundance through the time. Our results document a greater diversity between 3.1 and 2.7 Ma time interval, likely due to the development of eutrophic conditions during precessionally-driven insolation maxima at 400 ka eccentricity maxima, which are recorded in deeper depositional settings by sapropel clusters. Eutrophic conditions kept a complex trophic chain, as currently observed in the Ligurian Sea (Corsican-Ligurian-Provençal Basin), an area characterized also by upwelling. A reduction in both number and ecological diversity of cetacean taxa is observed along the Pliocene-Pleistocene transition; this trend, related to the onset of the Quaternary icehouse conditions, appears in good agreement with the recently recognized extinction event that affecting the marine megafauna at the end of the Pliocene
Palaeocological anatomy of shallow-water Plio-Pleistocene biocalcarenites (Northern Apennines, Italy)
Get PDFShell-rich biodetrital carbonate lithosomes punctuate the Plio-Pleistocene marine shallow-water successions of the Mediterranean basins. These m-thick sedimentary packages often display large-scale clinostratified geometry and show a remarkable rhythmic alternation with mudstone lithosomes. Our palaeoecological analysis defines the depositional settings and hints to the factors involved in the development of these peculiar bio-detrital carbonate units. Six distinct biofacies, have been identified through a two-way cluster analysis based on the macrofossil content, mostly molluscs, and matched with sedimentary facies. These are Aequipecten gr. opercularis and Bittium reticulatum biofacies, Anomia ephippium biofacies, Ditrupa arietina and Tritia semistriata biofacies, Corbula gibba and Saccella commutata biofacies, Timoclea ovata and Corbula gibba biofacies, Timoclea ovata and Anomia ephippium biofacies. Quantitative analyses suggest that these bio-detrital deposits have a multiphase history, and that, along with their bracketing marine mudstones, are not nearshore or shoreface deposits but developed in mid to outer shelf settings. Our results suggest that sea-level change was neither the only nor the main factor controlling the internal stacking pattern of individual biocalcarenites. They provide instead arguments in favour of periodic, high-amplitude climatic/oceanographic oscillations determining significant modifications of the source-to-sink dynamics of the basin and affecting the trophic structure, the supply of terrigenous sediments, as well as the energy and pattern of bottom currents of shelfal areas
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
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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