Principes de subdivision stratigraphique de l’histoire de la terre ; le cas du Quaternaire, sa signification et son rang hiérarchique

Historiquement, les unités stratigraphiques furent différenciées sur la base des caractéristiques de la biosphère. Pour les dépôts où les fossiles sont communs, l’unité de base est l’Étage ; chaque Étage correspondant, originellement, à une faune. Ils sont regroupés en unités de rang supérieur d’après l’importance des coupures biologiques. Dans la pratique, les Étages historiques étaient des formations (ensembles de couches) fossilifères régionales. Ce fondement a conduit à des difficultés d’application au niveau des limites car la base de ces Étages était localisée dans des dépôts transgressifs sur la plate forme continentale succédant à une lacune de dépôt. On a alors proposé de fixer les limites à la base du stratotype de l’Étage. Ainsi tous les dépôts antérieurs, connus ou inconnus, appartenaient à l’Étage inférieur ; il restait qu’une portion du temps n’était pas représentée par des dépôts dans ces stratotypes historiques. Par la suite, la communauté des stratigraphes a élaboré un nouveau principe, celui des Points Stratotypiques Mondiaux (PSM). Selon cette convention, un Étage est défini par un point, choisi par les experts dans une succession continue ; ce point définit l’Étage situé au-dessus. Dès lors, la limite était parfaitement définie par des dépôts antérieurs et postérieurs. Pour les stratigraphes francophones, le seul concept de PSM ne suffit pas à la définition complète d’une unité stratigraphique. Celle-ci nécessite trois composantes : le PSM de la limite inférieure, le PSM de la limite supérieure et un contenu dont l’essentiel est l’ensemble des couches du stratotype historique qui a donné son nom à l’Étage. L’intérêt de ce type de définition est que les notions de couches et de temps coïncident parfaitement ce qui a conduit à proposer, pour les langues où les deux notions étaient distinguées jusque là, une terminologie unique pour désigner les unités représentées par les couches (Erathème, Système, Série, Étage, sous étage inférieur, sous étage supérieur), et les unités de temps correspondantes (Ère, Période, Époque, Âge, sous âge “ancien”, “tardif”). C’est dans le cadre de l’Union Internationale des Sciences Géologiques (U.I.S.G) que sont élaborées les conventions internationales. La Commission Internationale de Stratigraphie est chargée de la question des unités stratigraphiques. Dans ce cadre, des sous commissions sont créées, lesquelles chargent des groupes de travail de prendre en main chaque convention. Ces conventions, proposées dans le cadre de ces Groupes de Travail, sont votées et avalisées par les instances de l’U.I.S.G. L’action, dans ces structures, est très influencée par un petit nombre de personnes sollicitant le travail d’un très grand nombre de personnes. Les outils utilisés par les stratigraphes pour caractériser les couches ne sont pas disponibles de façon uniforme au cours des temps géologiques. Dans cette optique, il existe trois sortes de stratigraphies : 1- celle où les Étages sont adaptés à la subdivision de l’histoire de la planète avec leur concept fondateur actuel, les PSM et le moyen de corrélation le plus commun, les fossiles ; 2- pour les temps plus anciens, les moyens de corrélation sont différents et obligent à changer la règle ; aujourd’hui, les conventions acceptées le plus généralement sont des âges conventionnels ; 3- au Quaternaire, une large palette d’outils est applicable et, selon les milieux, l’un ou l’autre outil sera appliqué et conduira à une subdivision propre. L’exploitation de la diversité des outils disponibles nécessite de ne pas s’encombrer d’unités uniques, mondiales, quand de nombreux outils peuvent être associés avec des âges en années. Les conventions, concept fixe et contraignant, sont remplacées par des connaissances, concept variable laissant une plus grande liberté de progrès. En outre, le Quaternaire n’est pas une subdivision comparable aux unités antérieures. Sa durée n’est pas supérieure à celle d’un Étage mais son rang hiérarchique doit aussi prendre en compte sa signification. Pour la première fois de l’histoire du globe, les temps quaternaires s’inscrivent dans une biosphère influencée, et même considérablement influencée à long terme, par une espèce unique. C’est une révolution fondamentale dans l’évolution. Cette prise en compte est aussi une nécessité pour la prise de conscience des responsabilités de l’homme vis à vis de son environnement ; elle se traduirait par le fait que l’unité Quaternaire pourrait se situer, de façon justifiable, au niveau d’une Ère succédant au Cénozoïque (ou Tertiaire) sinon d’un Éon de même rang que le Phanérozoïque. La question de la position précise de sa limite inférieure est autre ; il ne manque pas d’exemples, dans la colonne stratigraphique, dans lesquels le fait dominant caractérisant une unité n’apparaît pas précisément au premier moment de l’unité en question. Cependant, il serait souhaitable que l’“événement guide” pour situer la base du Quaternaire soit en relation avec le fondement de l’influence de l’homme : l’apparition de la pensée conceptuelle, marquée par l’apparition des outils vers 2,6 Ma.Throughout the history of geology, stratigraphical units have been identified and named according to the observation that macrofossils evolved over time from one deposit to the next. For example, the Aptian Stage is named after the particular fossils observed in deposits near Apt, SE France (Orbigny, 1840 in Moullade et al., 2006) or the Campanian Stage named after the deposits of the Champagne Charentaise area, SW France (Coquand, 1857 in Neumann and Odin, 2001). The sections selected as typical for a stage are called stratotypes. Thus, for deposits where fossils are common, the fundamental stratigraphical unit is the Stage which most commonly corresponds to a particular fauna found in a given three-dimensional-formation. The quite constant mechanism of evolution has led to the fact that those Stages have duration of the same order of magnitude (3 to 10 Ma) from the Cambrian System to the Neogene System, which lends to the concept of Stage an approximate time-significant value. These Stages are grouped in higher ranking units according to the significance of the cuts in terms of changes in the biosphere. These changes are reported in figure 1 according to modern information gathered by Lethiers (1998). It is clear that the pioneer stratigraphers recognised most of the main cuts in the biological evolution and used them as major unit boundaries (Era or System). So, from the practical point of view, historical Stages are defined as strata characterised by a particular fauna. This practice has led to some difficulties as far as the location of the boundaries is concerned. Often, the apparently “new fauna” results from transgressive deposits on the continental platform following a sedimentary break (and corresponding lack of record, see case 2, fig. 2). In a few other cases, the successive Stages defined in different basins include contemporaneous deposits with different faunas due to endemism or environmental differences (case 1, fig. 2). In order to solve these problems, it was first accepted that boundaries would be defined at the base of the historical stratotypes; in this situation, all deposits, known or unknown, and older than those located at the base of the stratotype pertain to the previous Stage. The remaining problem is that deposits immediately older than the boundary were not necessarily documented in the stratotypes. In order to solve the latter problem, stratigraphers (mainly represented by experts of the Phanerozoic interval of time) have decided to create a new kind of convention using the concept of Global Standard Stratotype Section and Point (GSSP or PSM –Point Stratotypic Global– in French, see fig. 3). According to this new convention, Stage boundaries (instead of Stage bodies) become the key for defining Stages. The GSSP defines a Stage by a point selected in a section where deposition is continuous and the Stage located above the point is defined by this point (Remane et al., 1996). According to this approach, the boundary becomes perfectly defined with deposits able to characterise the geological history above and below. French speaking stratigraphers have discussed this kind of definition (see Odin et al., 2004, 2005) and suggested that a single GSSP is not enough for the full definition of a stratigraphical unit. A complete definition needs three conventions : 1- the GSSP for the lower (older) boundary, 2- the GSSP for the upper (younger) boundary and 3- the historical stratotype which gives its name to the unit and generally documents the major portion of the unit’s content. This new approach using GSSP is interesting in that the distinct concepts of time on the one hand and strata deposited during (and documenting) this time on the other hand are fully coincident. This coincidence suggests that a single terminology is sufficient for designating time and rock units (Zalasiewicz et al., 2004) i.e., the differentiation previously made in some languages between rock units (Erathem, System, Series, Stage, Lower and Upper sub Stages), and the corresponding time units (Era, Period, Epoch, Age, Early and Late sub Stages, see fig. 5) is no longer necessary. The question is : which are the best words to be selected ? Zalasiewicz et al. (2004) would prefer the words shown in the right hand column (fig. 5) while Odin et al. (2004, 2005) would recommend the words shown in bold type in the same figure because they are distinct from the confusing words of the common language (such as epoch or period) and because they have long been used in many languages (upper, lower), even when geological time is concerned. These conventions are worked out within the International Union of Geological Sciences Organisation (IUGS). Within it, the International Commission of Stratigraphy is the appropriate body in charge for these conventions regarding stratigraphical units. This Commission is organised in sub commissions which create Working Groups each in charge for a particular convention (fig. 6). When a 60 % majority vote is obtained for a proposal within a Working Group, it is voted by the parent sub Commission, and the proposal is submitted to the Commission which votes and the accepted convention is submitted to IUGS for ratification. Within this organisation, a comparatively small number of people is usually able to significantly influence the work and decision of a large number of experts. An example of practical GSSP is given in figure 7. The conventions discussed above are mainly valid and of easy application for the fossil-bearing deposits, those which are the subject of interest of a majority of stratigraphers. However, the stratigraphical tools (the techniques of investigation documented in the deposits) applicable in the rocks are not the same in the deposits of different geological age (fig. 8). From that point of view, there are three distinct stratigraphies (Odin, 1994) : 1- the one where Stages are applicable for subdividing the geological history using the presently accepted and fully relevant concept of GSSP ; there, there is an abundant documentation by fossils (biostratigraphy is the key unequivocal dating tool) ; 2- for older time, the key unequivocal dating tool is geochronology ; accordingly, the appropriate sub commission on Precambrian Stratigraphy decided to select numerical ages for definition of conventional unit boundaries (Plumb, 1991) ; 3- for the Quaternary history, there is a large variety of particular tools often applicable in particular deposits or more or less local areas each one being able to generate its own scale (fig. 10). In this situation, the best use of the information suggests that each particular tool may be accepted for subdivision of the geological history. The use of a single series of integrated boundaries would not be easily applicable because all tools do not necessarily locate cuts at the same place while each kind of cut is an interesting piece of information. The correlation between the diversified columns may be achieved with more or less precise connection, using the known age (in years) of the key events. As a result, the Quaternary interval of time does not need unique conventions but is better based on evolving knowledge. According to us, conventions which are constraining and fixed concepts should thus be replaced by knowledge which gives a wider freedom for adapting to evolving information. The Quaternary is not similar to the older stratigraphical units. It is short but its hierarchical ranking must first depend on the significance one wants to give to it. Taking into account the major role of the biosphere in the previous subdivision of the geological history, the ranking of the Quaternary unit should reflect the considerable change in the process of evolution of life brought when the genus Homo appears. From that point of view, the history of the biosphere may be subdivided as shown in figure 9. Looking at this scheme, it is clear that there is a single taxon (man) which is able to influence the whole biosphere to its benefit (?) for the first time on Earth. This is not a detail of the history. The key role of this species is an observation but it is also necessary to point out this key role for becoming conscious of its responsibility with regard to its environment for the future. Taking this into account, the stratigraphical unit where man becomes a major actor of evolution must have the highest ranking, at least at the level of an Era (see fig. 5) distinct from the Cenozoic (or Tertiary) or possibly a sub Era if this kind of unit is useful in order to conform to the proposal of Pillans and Naish (2004). This means that the base of the Quaternary must cut all previous units of lower ranking in the hierarchy and cannot be part of a previous System as suggested in the proposal of inclusion in the Neogene System considered by Clague (2006). The question of the location of the lower boundary of the Quaternary is different from that of its ranking. As far as the nature of the key character of the unit (influence of man on the biosphere) is concerned, there are plenty of units of the time scale for which the key factor is NOT perceptible immediately above the base of the unit (trilobites do not appear at the base of the Palaeozoic, large dinosaurs do not appear at the base of the Mesozoic; mammals do not dominate at the base of the Tertiary). However, it would be advisable to locate the base of the Quaternary near the “guide event” related to the funding of the influence of man on biosphere which is the appearance of the conceptual thinking documented in the deposits by the first man artefacts about 2,5 Ma ago (Semaw et al., 1997, 2003)

The Changing Landscape for Stroke\ua0Prevention in AF: Findings From the GLORIA-AF Registry Phase 2

Background GLORIA-AF (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation) is a prospective, global registry program describing antithrombotic treatment patterns in patients with newly diagnosed nonvalvular atrial fibrillation at risk of stroke. Phase 2 began when dabigatran, the first non\u2013vitamin K antagonist oral anticoagulant (NOAC), became available. Objectives This study sought to describe phase 2 baseline data and compare these with the pre-NOAC era collected during phase 1. Methods During phase 2, 15,641 consenting patients were enrolled (November 2011 to December 2014); 15,092 were eligible. This pre-specified cross-sectional analysis describes eligible patients\u2019 baseline characteristics. Atrial fibrillation disease characteristics, medical outcomes, and concomitant diseases and medications were collected. Data were analyzed using descriptive statistics. Results Of the total patients, 45.5% were female; median age was 71 (interquartile range: 64, 78) years. Patients were from Europe (47.1%), North America (22.5%), Asia (20.3%), Latin America (6.0%), and the Middle East/Africa (4.0%). Most had high stroke risk (CHA2DS2-VASc [Congestive heart failure, Hypertension, Age  6575 years, Diabetes mellitus, previous Stroke, Vascular disease, Age 65 to 74 years, Sex category] score  652; 86.1%); 13.9% had moderate risk (CHA2DS2-VASc = 1). Overall, 79.9% received oral anticoagulants, of whom 47.6% received NOAC and 32.3% vitamin K antagonists (VKA); 12.1% received antiplatelet agents; 7.8% received no antithrombotic treatment. For comparison, the proportion of phase 1 patients (of N = 1,063 all eligible) prescribed VKA was 32.8%, acetylsalicylic acid 41.7%, and no therapy 20.2%. In Europe in phase 2, treatment with NOAC was more common than VKA (52.3% and 37.8%, respectively); 6.0% of patients received antiplatelet treatment; and 3.8% received no antithrombotic treatment. In North America, 52.1%, 26.2%, and 14.0% of patients received NOAC, VKA, and antiplatelet drugs, respectively; 7.5% received no antithrombotic treatment. NOAC use was less common in Asia (27.7%), where 27.5% of patients received VKA, 25.0% antiplatelet drugs, and 19.8% no antithrombotic treatment. Conclusions The baseline data from GLORIA-AF phase 2 demonstrate that in newly diagnosed nonvalvular atrial fibrillation patients, NOAC have been highly adopted into practice, becoming more frequently prescribed than VKA in Europe and North America. Worldwide, however, a large proportion of patients remain undertreated, particularly in Asia and North America. (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients With Atrial Fibrillation [GLORIA-AF]; NCT01468701

Principes de subdivision stratigraphique de l'histoire de la terre ; le cas du Quaternaire, sa signification et son rang hiérarchique: le cas du Quaternaire, sa signification et son rang hiérarchique

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Q5 Le Quaternaire, Limites et spécificités - Première partie

Colloque international organisé par le CNF-INQUA et l'AFEQ Muséum national d'Histoire naturelle (Paris, 1-3 février 2006

Patterns of oral anticoagulant use and outcomes in Asian patients with atrial fibrillation: a post-hoc analysis from the GLORIA-AF Registry

Background: Previous studies suggested potential ethnic differences in the management and outcomes of atrial fibrillation (AF). We aim to analyse oral anticoagulant (OAC) prescription, discontinuation, and risk of adverse outcomes in Asian patients with AF, using data from a global prospective cohort study. Methods: From the GLORIA-AF Registry Phase II-III (November 2011-December 2014 for Phase II, and January 2014-December 2016 for Phase III), we analysed patients according to their self-reported ethnicity (Asian vs. non-Asian), as well as according to Asian subgroups (Chinese, Japanese, Korean and other Asian). Logistic regression was used to analyse OAC prescription, while the risk of OAC discontinuation and adverse outcomes were analysed through Cox-regression model. Our primary outcome was the composite of all-cause death and major adverse cardiovascular events (MACE). The original studies were registered with ClinicalTrials.gov, NCT01468701, NCT01671007, and NCT01937377. Findings: 34,421 patients were included (70.0 ± 10.5 years, 45.1% females, 6900 (20.0%) Asian: 3829 (55.5%) Chinese, 814 (11.8%) Japanese, 1964 (28.5%) Korean and 293 (4.2%) other Asian). Most of the Asian patients were recruited in Asia (n = 6701, 97.1%), while non-Asian patients were mainly recruited in Europe (n = 15,449, 56.1%) and North America (n = 8378, 30.4%). Compared to non-Asian individuals, prescription of OAC and non-vitamin K antagonist oral anticoagulant (NOAC) was lower in Asian patients (Odds Ratio [OR] and 95% Confidence Intervals (CI): 0.23 [0.22-0.25] and 0.66 [0.61-0.71], respectively), but higher in the Japanese subgroup. Asian ethnicity was also associated with higher risk of OAC discontinuation (Hazard Ratio [HR] and [95% CI]: 1.79 [1.67-1.92]), and lower risk of the primary composite outcome (HR [95% CI]: 0.86 [0.76-0.96]). Among the exploratory secondary outcomes, Asian ethnicity was associated with higher risks of thromboembolism and intracranial haemorrhage, and lower risk of major bleeding. Interpretation: Our results showed that Asian patients with AF showed suboptimal thromboembolic risk management and a specific risk profile of adverse outcomes; these differences may also reflect differences in country-specific factors. Ensuring integrated and appropriate treatment of these patients is crucial to improve their prognosis. Funding: The GLORIA-AF Registry was funded by Boehringer Ingelheim GmbH

Correction to: Comparative effectiveness and safety of non-vitamin K antagonists for atrial fibrillation in clinical practice: GLORIA-AF Registry

International audienceIn this article, the name of the GLORIA-AF investigator Anastasios Kollias was given incorrectly as Athanasios Kollias in the Acknowledgements. The original article has been corrected