1,720,979 research outputs found
Correlation potential of Middle Triassic hemipelagic carbonate successions using carbon isotopes
No full textStable isotope studies of the marine Triassic have previously focused on two intervals, the Permian/Triassic and Triassic/Jurassic boundaries. The potential of stable carbon
and oxygen isotopes as chemostratigraphic correlation tools, however, is largely untapped for Triassic carbonate successions. The present study was launched to explore the usefulness of carbon isotope data in correlating Middle Triassic deep-water,
hemipelagic carbonate sediments of the Livinallongo Formation of the Dolomites (Southern Alps, Northern Italy).
The samples come mostly from the Knollenkalke Member consisting of greenishgrey, bioturbated, nodular limestones. We analyzed the micritic calcite within individual nodules and compared its composition to that of matrix calcite as well as late
diagenetic calcite veins.
Thin-section examination aided by cathodoluminescence petrography and scanning electron microscopy suggest that the fine grained calcite cement in the nodules formed near the sediment-water interface and has not been diagenetically altered since then.
Its carbon isotopic composition therefore most likely reflects the initial seawater isotopic composition.
The carbon isotope data from the Knollenkalke Member show a secular trend of increasing values upsection which coincides with a similar trend in biostratigraphically correlated sections in eastern Romania (Atudorei et al., 1997) and Oman (Hauser et al., 2001). These preliminary results suggests the presence of a possibly Tethys-wide chemostratigraphic marker in the Middle Triassic.
Hauser M. et al., 2001, Eclogae geol. Helv., 94, 29-62
Atudorei V. et al., 1997, Extended scientific report of the project 95-32 “The Triassic of north-Dobrogea”, Geological Museum, Lausanne, Switzerland
Aragonite dissolution, sedimentation rates and carbon isotopes in deep-water hemipelagites (Livinallongo Formation, Middle Triassic, northern Italy) - Reply
No full textIn a discussion of our recent paper, Maurer and Brack
[Maurer, F., Brack, P., 2007. Aragonite dissolution, sedimentation
rates and carbon isotopes in deep-water hemipelagites
(Livinallongo Formation, Middle Triassic,
northern Italy) — Comment. Sedimentary Geology
doi:10.1016/j.sedgeo.2006.09.003] suggested that, in the
Buchenstein Basin (i.e., the sedimentary basin represented
by the Buchenstein Group), sedimentation rates of
laminated and bioturbated facies were approximately the
same, and post depositional pressure dissolution was the
dominant mechanism of carbonate dissolution. The
authors drew their conclusions partly from hitherto
unpublished data, and partly from the literature.
More specifically, their discussion focuses on four
points, (i) the reliability of correlations, (ii) the rate of
sedimentation of different facies of the Livinallongo
Fm. — Buchenstein beds, (iii) the origin of sediments,
and (iv) the mechanism of carbonate dissolution.
We welcome the new data presented by Maurer and
Brack. We believe, however, that some of their points
arose from misinterpretations of our study, partly due to
a graphical error. In this reply, we take the opportunity
to clarify the issues raised by Maurer and Brack
[Maurer, F., Brack, P., 2007. Aragonite dissolution,
sedimentation rates and carbon isotopes in deep-water
hemipelagites (Livinallongo Formation, Middle Triassic,
northern Italy) — Comment. Sedimentary Geology
doi:10.1016/j.sedgeo.2006.09.003]
Age, soil-forming processes, and archaeology of the loess deposits at the Apennine margin of the Po plain (northern Italy): New insights from the Ghiardo area
No full text
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
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