Lower Devonian rhynchonellid brachiopods from the Ougarta area (western Sahara, Algeria)

The description and study of rhynchonellid brachiopods recently collected from the Lower Devonian of the Ougarta area in western Algerian Sahara permitted the revision of previously described and/or listed taxa, mainly from Morocco. Palaeobiogeographically, the nine identified taxa share many similarities with the rhynchonellid fauna of the Ibarmaghian Domain. Five of the nine identified taxa belong to three genera of the Family Nucinulidae Sartenaer, 2004. Three of these are new taxa, namely Nucinulus orbignyanus crassicostus subsp. nov., Cuninulus ougartaensis sp. nov. and Palinulus saharaensis sp. nov. The our remaining taxa are assigned (one of them questionably) to the genera Lanceomyonia, Stenorhynchia and Glossinulus of the families Hebetoechiidae, Trigonirhynchiidae, and Glossinotoechiidae, respectively.Peer reviewe

Les Chitinozoaires du Silurien superieur et du Devonien du Sahara Algerien (cadre geologique, systematique, biostratigraphie)

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Datation par les chitinozoaires des principaux épisodes transgressifs identifiés dans l'Ordovicien du Sahara Algérien

10 p.Au cours de l'Ordovicien, des variations du niveau marin ont été identifiées dans les régions nord gondwaniennes en exploitant les données de l'analyse des faciès, des faunes et des traces-fossiles sensibles à la bathymétrie. Les épisodes de montée du niveau marin enregistrés sont datés en termes de biozones de chitinozoaires nord gondwaniens. Une hiérarchie est proposée parmi les neuf épisodes transgressifs retenus car ils présentent une extension régionale. Du plus ancien au plus récent il s'agit des événements transgressifs à destombesi, brevicollis/symmetrica, brevis, bulla, formosa, pissotensis p.p., ponceti/deunffi, fistulosa et elongata p.p. En raison de leur amplitude et de leur vaste distribution paléogéographique, les événements à formosa et à fistulosa apparaissent comme les principaux épisodes transgressifs ordoviciens dans les régions nord gondwaniennes. Les dépôts argileux associés à ces hauts nivaux marins sont enregistrés jusque dans les séquences les plus proximales en bordure du Hoggar et du bouclier arabique. Le cas de l'événement transgressif à elongata p.p. est un peu particulier car il correspond à la fusion au moins partielle, vers la fin de l'Hirnantien, de la calotte glaciaire couvrant une large part du Gondwana

Devonian sea level fluctuations on northern Gondwana

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Chitinozoan-based calibration of Early-Mid Ordovician transgressive events on northern Gondwana

International audienc

Biostratigraphical calibration of third order Ordovician sequences on the northern Gondwana platform

International audienceThis study illustrates bathymetric trends across the northern Gondwana platform during the Ordovician. The sedimentary records of the Algerian Sahara, central Morocco, and western France are investigated to document related environmental changes through the period. Outcrop and subcrop sections have been selected with regard to their completeness and to the precision of the available biostratigraphical data, based on chitinozoans. This group provides the most continuous biostratigraphical record in the terrigenous Ordovician successions of northern Gondwana. For each area, the chitinozoan data have been assembled, updated and referred to one of the 26 Ordovician chitinozoan biozones defined in northern Gondwana regions. A sequential analysis based on the identification of genetic units is presented. The stacking pattern of these units is established for each locality, and the resulting curves express variations in sedimentary environments partly driven by relative sea-level changes. From successive smoothings of these curves, we define 16 main cycles at lower frequencies. Uncertainties concerning the precise chronostratigraphic position of some of these cycles are discussed. The proposed northern Gondwana relative sea-level variation curves are compared to the recently-published global Ordovician sea-level curve and to other regional curves available for the major Ordovician palaeoplates (Laurentia, Baltica, South China, north-eastern Gondwana)

Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

International audienceThe aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed