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La crisi sinemuriana delle piattaforme carbonatiche del Sudalpino orientale
No full textIn an undefined moment of the Sinemurian – Pliensbachian interval, a global crisis of the carbonate platforms induced the reorganization of the palaeogeography of the eastern Southern Alps (MASETTI et al., 2012). Roughly in correspondence of the Sinemurinan-Pliensbachian boundary, recent investigations have found a negative δ13C isotope anomaly attributed to a global perturbation of the carbon cycle (e.g., JENKYNS et al., 2002).
The present work aimed at identifying the causes of the Southern Alps carbonate platforms’ crisis and at more accurately defining the moment in time of this event. I employed a multidisciplinary approach (facies analysis, chemostratigraphy and biostratigrapy) to investigate eight stratigraphic sections located along a West-Est oriented transect, crossing the Trento Platform, the Belluno Basin and the Friulian Platform.
For the Central-Weastern sector of the Trento Platform, I have investigated the sections of Chizzola, Madonna della Corona, Rotzo, Val Gola which are characterized by the shallow water pliensbachian deposit of the Rotzo Formation (Calcari Grigi Group). For the North-Eastern sector, in which the Rotzo Fm. is absent, the sections of Foza and Col Moschin have been sampled.
In these last two sections, an unconformity surface defines the upper limit of the hettangian-sinemurian peritidal facies of the M. Zugna Fm. (Calcari Grigi Group). On the top of this surface, either the drowning facies of the Fanes Piccola Encrinite unit (upper Pliensbachian) or the pelagic ones belonging to the Lower Rosso Ammonitico (upper Bajocian – lower Callovian) rest.
A similar stratigraphic setting was observed in the Northern sector of the Friulian Platform, the only one where the Calcari Grigi Group crops out. In this sector, I studied the M. Cumieli section. In the Belluno Basin, located between the two above mentioned platforms, the section of M. Verzegnis (Soverzene Fm.) has been sampled.
Moreover, I chose the Campanian-Lucanian Platform (Southern Apennines) in order to better characterize the geographical extension of the carbon isotope signal and to compare coeval carbonate platform deposits that doesn’t belong to the Southern Alps sector. As representative of the Campanian-Lucanian Platform, the formation called Palaeodasycladus Limestone cropping out at the Valico di Chiunzi (Lattari Mts., close to Salerno) has been investigated.
In collaboration with the Earth Sciences Department of the Oxford University, analyses on the carbon and oxygen stables isotopes have been performed on about 2000 samples of
powder rock (bulk rock) sampled every 20 cm along an overall stratigraphic thickness of more than 700 m. High resolution δ13C curves allowed to identify a large primary negative excursion located in the upper part of the peri-platform unit of Soverzene. The unearthing of an ammonite belonging to the Arnioceras genus allowed referring this anomaly to the boundary between Lower Sinemurian (Semicostatum zone and Turneri zone) and the upper Sinemurian (Obtusum zone). Such anomaly has been found also in the upper part of the M. Zugna Fm. (Trento Platform and Friulian Platform) and in peritidal facies of the Palaeodasycladus Limestone (Campanian-Lucanian Platform). In both cases the excursion generally corresponded to the F.O. of the foraminifera Paleomayncina termieri. The correlation of the isotope excursion has allowed to define an Arnioceras time-line across the platform and basin domains and to better calibrate the F.O. of Paleomayncina termieri.
The negative excursion, in keeping with the variations in the relative sea level curve indicated in the literature (HESSELBO, 2008; HESSELBO & JENKYNS, 1998), corresponds to a transgressive phase in the platform domains induced by the crisis of the carbonate factory.
This crisis determines the definitive interruption of the carbonate peritidal sedimentation existing since the upper Triassic and the consequent underfed of the Belluno Basin.
From the upper Pliensbachian, a new generation of carbonate platforms got established. This is predominantly characterized by a subtidal sedimentation and initially by eutrophic conditions, in which large bivalves of the “facies a Lithiotis” accumulated (Rotzo Fm., Southern Alps; Lithiotis Member, Southern Appenine).
The data suggest that the isotopic anomaly is supra-regional, as suggested by the simultaneous dismiss of coeval carbonate platforms, including that of the Corna in the Brescian Alps (SCHIROLLI, 1997), Rocca Livernà Limestone in the Ligurian Alps (DECARLIS & LUALDI, 2010), Calcare Massiccio in Umbro-Marchean-Sabina Appenine, Inici Fm. in Sicily (RONCHI et al., 2000) and Djebel Bou Dahar in the High Atlas marocain (MERINO-TOMÈ et al., 2012). The absence of reliable evidence of a significant volcanic activity in that part of the Sinemurian permitted to attribute the negative isotopic excursion to the introduction of large amounts of the lightweight 12C isotope in the ocean-atmosphere system, issued in the form of methane as a result of destabilization of gas hydrates. The most credited cause of their dissociation is the warming up of oceanic bottom water associated with changes of ocean circulation (JENKYNS, 2003 cum bibl.). It’s possible that the syn-sedimentary tectonics that was affecting the Jurassic continental margin at that period may have contributed to the destabilization of the gas hydrates, although with intensities that are difficult to estimate
Carbon-isotope anomalies and demise of carbonate platforms in the Sinemurian (Early Jurassic) of the Tethyan region: Evidence from the Southern Alps (Northern Italy)
Get PDFDespite its global impact on ecosystems, the Triassic/Jurassic boundary event had only a modest effect on the carbonate depositional systems of the Southern Alps, whereas a fundamental reorganization of the same palaeogeographic area took place during the Sinemurian Age. This paper investigates whether or not the well-documented demise of Sinemurian carbonate platforms in the Tethyan region was a response to a global event by examination of carbon-isotope anomalies in successions of different facies that record this interval of time. A chemostratigraphic transect from LakeGardauptotheeasternItalianborderisillustrated byfourstratigraphicsections;high-resolution (20 cm over key intervals) chemostratigraphic sampling allowed detection of a major negative δ13C anomaly of 1.5‰, preceded by a positive excursion, both in shallow- and deep-water successions, over the stratigraphical range of the ammonite genus Arnioceras. A comparison with sections from the UK suggests that the positive excursion belongs to the turneri Zone and the succeeding negative excursion falls within the obtusum Zone. In the deep-water Belluno Basin, the negative anomaly occurs in a biogenic chert-rich unit recording the onset of mesotrophic conditions in the basin. In the platform-carbonate successions, this major negative carbon-isotope excursion is developed within a calcarenitic unit corresponding to the lowest occurrence of the foraminifer Paleomayncina termieri. Thisevidencefordeepeningandtransgressionacrossthecarbonateplatformsuggestspre-conditioning for drowning. Hence, rather than tectonic subsidence alone, environmental factors may have aided the demise of Tethyan carbonate platforms during the Early Jurassic Sinemurian Age
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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