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Multiple Dolomitization Episodes In Deep-Water Limestones of the Triassic Lagonegro Basin (Southern Italy): From Early Reflux To Tectonically Driven Fluid Flow
Get PDFMassive dolomitization does not commonly occur in deep-water carbonates. However, this regional study on outcrops and subsurface samples of Triassic Lagonegro basinal carbonates from the southern Apennines fold and thrust belt (Italy) shows that the evolution of the Lagonegro basin was punctuated by two events of massive dolomitization. These processes resulted in two distinct dolomite types, displaying different petrographic and geochemical features. A medium-crystalline and fabric-preservative dolomite in the northern area (Molise, Campagna, and San Fele–Mount Pierno) contrasts with a medium- to coarse-crystalline and fabric-destructive dolomite in the southern area (from Pignola to the high Val d'Agri).
Geochemical data (increase in δ18O with respect to typical Late Triassic seawater values, high Sr and low Mn and Fe content, Sr isotopes consistent with Late Triassic seawater) indicate that the dolomite in the northern area is the result of an early replacement caused by a marine and possibly oxidizing fluid during shallow burial. Dolomitizing fluids likely were expelled through reflux from the Norian Apenninic carbonate platform towards the proximal Lagonegro basin. This reflux was promoted by the Norian peculiar paleoceanographic and climatic conditions in the Tethyan region, and affected only the proximal basinal facies.
Dolomites in the southern area display a decrease in δ18O compared to Late Triassic seawater values and show lower Sr, higher Mn and Fe contents, and higher Sr isotope ratios compared to the early dolomites of the northern area. Fluid-inclusion microthermometry reveals homogenization temperatures between 70 and 120°C and salinities of 1.9 to 6.4 wt % NaCl eq. for saddle dolomites. These geochemical signatures indicate that the southern area was affected by late diagenetic burial dolomitization, interpreted to be the result of large scale tectonically driven fluid flow during the second compressional phase characterizing the southern Apennines fold and thrust belt emplacement.
The dolomite distribution across the Lagonegro basin (northern and southern) is possibly controlled by the paleogeographic distribution of the facies (proximal vs. distal) as well as by their proximity to thrust faults. The Lagonegro case study demonstrates that basinal successions may undergo multiple dolomitization episodes in a manner similar to carbonate platform successions, from early shallow to deep-burial diagenesis. One of the relevant implications is that in areas of restricted oceanographic circulation, during periods of aridity, reflux dolomitization may extend beyond the platform margin, into deep-water carbonates, having the potential to alter their reservoir quality
Late Dolomitization in Basinal Limestones of the Southern Apennines Fold and Thrust Belt (Italy)
No full textThe Triassic pelagic carbonates of the Lagonegro Units from the southern Apennines fold and thrust belt host discordant bodies of dolostone. These rocks show textural features typical of zebra or
saddle dolomites. In this contribution, the results of field observations, petrography and geochemical analyzes performed on samples from three different outcrops are presented.
Field data indicate that the peculiar zebra-type rock and brecciated fabrics were controlled by regular
bedding of the micritic, pelagic limestones. The dolomitization resulted in the replacement of the host
limestones and subsequent void-filling precipitation of dolomite in a dilatational stress field.
Homogenization temperatures (Th) are in the range 80 - 120°C, with a clear mode of 95 ± 10°C. When corrected for maximum pressure, they indicate an upper limit for dolomite formation around 110 - 115°C. Melting temperatures of ice (Tmi) point to salinities in the range 2-6 wt% NaCl eq, with a mean of 4.2%.
δ13C values overlap those of the Upper Triassic seawater, whereas the δ18O values are significantly depleted compared to the coeval seawater. 87Sr/86Sr values are higher with respect to Upper Triassic seawater, and partially overlap Middle-Upper Miocene values.
The performed analyzes indicate a dolomitization process driven by warm fluids (110 - 115°C) with a
salinity close to that of seawater and O-isotope ratios comprised between seawater and formation waters. It is suggested that the dolomitization was accomplished by formation waters squeezed out or from surrounding lithologies or from the underlying mélange units. Integration with available thermal data on the collisional history of the belt suggests that the fluid-flow took place after maximum burial, in the early stages of exhumation, in the assumption of a fluid in thermal equilibrium with the host rocks.
According to literature data, the dolomitization event was quite widespread. It can be argued that it was part of a major fluid-flux associated with fold and thrust belt development, which possibly affected the Apulian Platform carbonates located in the foreland. The latter, now buried below the nappe stack, hosts some of the major oil fields of continental Europe
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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