1,720,980 research outputs found
Contribution to the late triassic geochronology by magnetostratigraphic correlations between tethyan marine sections and the newark apts
Full text linkChronology of Late Triassic (last Epoch of Triassic Period) is still a debated question. Late Triassic is constrained by two U/Pb ages, one near the Ladinian/Carnian boundary (237.773±0.052 Ma; Alpe di Siusi/Seiser Alm, Italy) and the other at the Rhaetian/Hettangian boundary (201.36±0.17 Ma; Levanto, Peru). Unfortunately, any radiometric age constraints the Stage boundaries of Late Triassic. Many attempts to assign an age to the Stages have been made during the last 20 years, correlating marine sections (usually from Tethys) with the Newark Astrochronological Polarity Time Scale (Newark APTS). The ages obtained was sometimes very different, in particular for the Rhaetian, with a duration that varied from ~2 My to ~9 My depending from the correlation performed with the APTS. The options proposed in the Geological Time Scale 2012 introduced two different ages for both Rhaetian (~205.4 Ma and ~209 Ma) and Norian (~221 Ma and ~228 Ma). The Norian age of ~228 Ma seems coherent with many other correlations between marine sections and the APTS. In an effort to help resolving the issues of the Late Triassic chronology, selected Tethyan marine sections, characterized by a detailed biostratigraphy, have been analyzed for paleomagnetism. The investigation are focused on two main intervals: the Rhaetian and the Carnian. The Rhaetian have been chosen for the reasons explained before (confused chronology), the Carnian because the few magnetostratigraphic data covering this interval, in particular its middle part, must be integrated to obtain a continuous magnetostratigraphy of this Stage. The chosen sections are: Pignola-Abriola, Mount Messapion and the ODP Leg 122-Hole 761C for the Rhaetian; Pignola-2, Dibona, and ODP Leg 122-Holes 759B/760B for the Carnian. The magnetostratigraphy of these sections have been integrated with the data from other Tethyan sections in literature, obtaining a continuous magnetostratigraphy spanning the entire Late Triassic. This composite magnetostratigraphy of Tethyan section has been time-calibrated using the Newark APTS, linked to the composite through the statistical correlations with Pignola-2, Pizzo Mondello, and Pignola-Abriola. The so obtained Geomagnetic Polarity Time Scale (GPTS) has been used to assign an age to the events calibrated to the magnetostratigraphy of the Late Triassic, like the bioevents defining the Stage and substage boundaries, or climatic events as the Carnian Pluvial Event
Paleomagnetic data from the Pignola 2 section (Southern Apennines, Italy) and the Dibona section (Dolomites, Italy): a contribution to the Carnian magnetostratigraphy
No full textMagnetostratigraphy of the Punta Grohmann section (Dolomites, Italy): improving the chronology of the Ladinian/Carnian boundary
No full textWe provide the magnetostratigraphy of the Ladinian/Carnian Punta Grohmann stratigraphic section (Dolomites, Italy), calibrated with U Pb ages from the literature (237.58 0.04 Ma; 237.68 0.05 Ma). The FO of ammonoid Zestoceras lorigae, the base of the vigens-densus palynomorphs Zone, and sequence stratigraphy suggest a Carnian age for the upper part of the section, which has been confirmed by the magnetostratigraphic correlation between Punta Grohmann and Prati di Stuores (Carnian GSSP). Additional magnetostratigraphic correlation between Punta Grohmann and key time-calibrated Ladinian–Carnian sections from the literature (e.g., Mayerling, Seceda, Rio Nigra) lead to a more precise age of the Carnian base (about 236.5 Ma) and to a better definition of the Middle–Late Triassic Geomagnetic Polarity Time Scale
Late Norian δ13Corg record in the Tethyan realm: New clues on the complex Late Triassic carbon cycle from the Lagonegro Basin (southern Italy)
No full textGoing 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
New clues on the complex Late Triassic carbon cycle from the Lagonegro Basin (southern Italy)
No full textVariations 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
- …
