1,721,193 research outputs found
Comportement du champ magnetique terrestre au cours de transitions de polarite
No full textSIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
A quick look at the MAGIC database
No full textNational audienceIn order to publish an article in most scientific journals, it is now often required that access be given to all paleomagnetic data, especially demagnetization data, rather than interpretations (FAIR principles). However, this requirement remains largely unfulfilled despite the existence of a dedicated database. Indeed, the MAGIC database (https://www2.earthref.org/MagIC/about) provides the possibility of a fairly comprehensive archive of the various data and interpretations obtained during most paleomagnetic studies. As of June 2023, about 250 of the more than 4400 contributions listed contain raw data. Most of the archived data correspond to studies published in the last ten years. MAGIC is based on a collection of open source Python programs for analyzing and uploading data but can be accessed without relying on the tools provided (Pmagpy). The complexity of the database archiving process is often cited as a reason for not publishing data. However, this complexity is partly the price to pay for the diverse information that can be stored. Despite the small number of contributions to the MAGIC website, we can already identify a number of problems, such as the failure of some users to follow basic rules such as sample orientation. There are also inconsistencies between the interpretations published in the articles and the actual data. Some data, such as low field susceptibility, which provides important information about magnetic carriers, is rarely archived. From my own experience with data archiving in MAGIC to reviewing a number of contributions, I will try to convince you of the usefulness of this archiving, which in my opinion should also be accompanied by a process of data evaluation. During an article evaluation process, reviewers should be able to evaluate the data, and the archiving condition should be automatic upon acceptance of the article, and not remain a promise of future publication by the authors. Such a measure would probably strengthen the MAGIC initiative that our American colleagues have been pursuing for almost 20 years. We should not forget that it is not the fanciful interpretations published in an article that are important, but the data
A quick look at the MAGIC database
No full textNational audienceIn order to publish an article in most scientific journals, it is now often required that access be given to all paleomagnetic data, especially demagnetization data, rather than interpretations (FAIR principles). However, this requirement remains largely unfulfilled despite the existence of a dedicated database. Indeed, the MAGIC database (https://www2.earthref.org/MagIC/about) provides the possibility of a fairly comprehensive archive of the various data and interpretations obtained during most paleomagnetic studies. As of June 2023, about 250 of the more than 4400 contributions listed contain raw data. Most of the archived data correspond to studies published in the last ten years. MAGIC is based on a collection of open source Python programs for analyzing and uploading data but can be accessed without relying on the tools provided (Pmagpy). The complexity of the database archiving process is often cited as a reason for not publishing data. However, this complexity is partly the price to pay for the diverse information that can be stored. Despite the small number of contributions to the MAGIC website, we can already identify a number of problems, such as the failure of some users to follow basic rules such as sample orientation. There are also inconsistencies between the interpretations published in the articles and the actual data. Some data, such as low field susceptibility, which provides important information about magnetic carriers, is rarely archived. From my own experience with data archiving in MAGIC to reviewing a number of contributions, I will try to convince you of the usefulness of this archiving, which in my opinion should also be accompanied by a process of data evaluation. During an article evaluation process, reviewers should be able to evaluate the data, and the archiving condition should be automatic upon acceptance of the article, and not remain a promise of future publication by the authors. Such a measure would probably strengthen the MAGIC initiative that our American colleagues have been pursuing for almost 20 years. We should not forget that it is not the fanciful interpretations published in an article that are important, but the data
Formation of the Patagonian Orocline and paleogeographic evolution of the Patagonian –Antarctic Peninsula System
No full textA l’échelle continentale, la Cordillère des Andes présente d’importantes courbures. Une des plus importantes est la Courbure de la Patagonie, où le cours de l’orogène et de ses principales provinces tectoniques pivotent de près de 90°, passant d’une orientation N-S à 50°C à une orientation E-O en Terre de Feu. Malgré son importance, l’origine de la Courbure de la Patagonie et son implication dans les reconstructions paléogéographiques demeurent sujet à controverse: est-elle le résultat d’un plissement oroclinal, ou bien une caractéristique héritée? C’est dans ce contexte que j’ai réalisé une étude paléomagnétique et de susceptibilité d'anisotropie magnétique dans la région des Andes Australes. Les résultats obtenus suggèrent que la partie intérieure de cette courbure soit une caractéristique secondaire liée à l’évolution de la Péninsule Antarctique.At the continental scale, the Andes presents significant curvatures. One of the largest is the curvature of Patagonia, where the orogen and its main tectonic provinces are rotated about 90 ° from an NS direction at 50 ° to an EO orientation in Tierra del Fuego. Despite its importance, the origin of the curvature of Patagonia and its involvement in paleogeographic reconstructions remain controversial: is the result of an oroclinal bending, or an inherited characteristic? It is in this context that I made a paleomagnetic and magnetic susceptibility anisotropy in the Austral Andes region. The results suggest that the inner part of the bend is a secondary feature linked to the evolution of the Antarctic Peninsula.In this thesis, I will present the results of a paleomagnetic and anisotropy of magnetic susceptibility (AMS) study of 146 sites sampled between 50 ° S and 55.5 ° S (85 sites in marine sedimentary rocks of the Cretaceous-Miocene of the Magallanes fold and thrust belt; 20 sites in sedimentary and volcanic rocks south of Cordillera Darwin, 41 sites in intrusive rocks of the Cretaceous-Eocene batholith. The AMS results in the sediments show that the magnetic fabric is controlled by tectonic processes, partially or completely obliterating the sedimentary fabric. In general, there is a good correlation between the orientation of the magnetic lineation and that of the fold axes except at Peninsula Brunswick. The wide variation in the orientation of magnetic fabrics within the batholith suggests an emplacement of intrusive without tectonic constraint. Paleomagnetic results obtained in Navarino Island and Hardy Peninsula, south of the Beagle Channel, show a post-tectonic remagnetization recording a counterclockwise rotation of more than 90 ° as that recorded by the intrusive rocks older than ~ 90Ma. The Upper Cretaceous to Eocene intrusive rocks record counterclockwise rotations of lower magnitude (45 ° -30 °). In contrast, the Magallanes fold and thrust belt mainly developed between the Eocene and Oligocene records little or no rotation. Spatial and temporal variations of tectonic rotations determined in this study support a model of deformation of the Austral Andes in two steps. The first step corresponds to the rotation of a volcanic arc by closing a marginal basin (the Rocas Verdes basin) and formation of Cordillera Darwin. During the propagation of deformation in the foreland, the curvature acquired by the Pacific border of the Austral Andes is accentuated by about 30 °. The tectonic reconstructions using the most recent Global Plate Tectonic model show the essential role of the convergence between the Antarctic Peninsula and South America in the formation of Patagonian orocline during the Late Cretaceous to the Eocene
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
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