124 research outputs found
Hyperactive neotectonic near the South Rifian front Lifted Late Quaternary lagunal deposits (Atlantic Morocco)
Mediterranean biodiversity gradient initiated by basin restriction
Physical connectivity between marine basins facilitates population exchange and hence controls biodiversity. The Mediterranean Sea is a semi-restricted basin with only a small two-way connection to the global ocean, and it is a region heavily impacted by climate change and biological invasions today. The massive migration of non-indigenous species into the basin through the Suez Canal, driven and enabled by climate warming, is drastically changing Mediterranean biodiversity. Understanding therefore the origin and cause(s) of pre-existing biodiversity patterns is crucial for predicting future impacts of climate change. Mediterranean biodiversity exhibits a west-to-east decreasing gradient in terms of species richness, but the processes that resulted in this gradient have only been hypothesized. By examining the fossil record, we provide evidence that this gradient developed 5.33 million years ago at the end of the Messinian Salinity Crisis, and it was therefore caused by the re-population of the basin by marine species with a dominating western source at the MediterraneanÂżAtlantic gateway
Distribution of common modern dinoflagellate cyst taxa in surface sediments of the Northern Hemisphere in relation to environmental parameters: the new n = 1968 database
The dinoflagellate cyst genera Achomosphaera Evitt 1963 and Spiniferites Mantell 1850 in Pliocene to modern sediments: a summary of round table discussions
Source at https://doi.org/10.1080/01916122.2018.1465739. We present a summary of two round-table discussions held during two subsequent workshops in Montreal (Canada) on 16 April 2014 and Ostend (Belgium) on 8 July 2015. Five species of the genus Achomosphaera Evitt 1963 and 33 of the genus Spiniferites Mantell 1850 emend. Sarjeant 1970 occuring in Pliocene to modern sediments are listed and briefly described along with remarks made by workshop participants. In addition, several holotypes and topotypes are reillustrated. Three species previously assigned to Spiniferites are here considered/accepted as belonging to other genera: Impagidinium inaequalis (Wall and Dale in Wall et al.1973) Londeix et al. 2009, Spiniferites? rubinus (Rossignol 1962 ex Rossignol 1964) Sarjeant 1970, and Thalassiphora balcanica Baltes ̧ 1971. This summary forms the basis for a set of papers that follows, where points raised during the workshops are explored in greater detail
La distribution des kystes de Dinoflagellés dans les sédiments hémipélagiques (ArdÚche) et pélagiques (Arc de Castellane, S.E. de la France) en domaine vocontien, du Valanginien terminal au Barrémien inférieur - Biostratigraphie et relations avec la stratigraphie séquentielle.
Two sections from the Lower Vocontian Cretaceous (SE France) representing pelagic (Clue de Vergons; Alpes-de-Haute-Provence) and hemipelagic (Ravin des BuissiĂšres; ArdĂšche) environments were studied from a palynological point of view (mainly dinoflagellates). Well dated by ammonites faunas, these sections lie on the Uppermost Valanginian - Lower Barremian time interval. The discontinuities of the Sequence stratigraphy (Vail concept) have been recognized in situ for each of the outcrops.The original inventory of dinokysts in these series, based on 105 samples, resulted in the recognition of almost 190 taxa. A biozonation based on stratigraphic extensions and dinocyst assemblages is proposed. It is compared with that provided by ammonite faunas and with Sequence stratigraphy: the dinozonation established proves to be a biostratigraphic scale that rarely depends on the other two. At the level of 3rd order cycles, no systematic relationship can be observed between sequence discontinuities and dinocyst assemblages. Some correlations are proposed for 2nd order cycles (recognition of the transgressive interval; general rise in sea level). From a biostratigraphic point of view, these local results are placed in a more global framework and compared with the dinozonations of the main basins of the Lower Cretaceous.Based on variations in the content of dinokyst assemblages and variations in the frequencies of certain taxa, a palaeoecology study was carried out: certain environmental parameters such as variations in sea level, distance from the coast and surface salinity were identified, indicating an overall rise in sea level from the base to the top of the Hauterivian. The Muderongia/Phoberocysta genera ratio can be used to propose a diagram of sea-level variations, particularly for the Lower Hauterivian.Deux coupes du CrĂ©tacĂ© infĂ©rieur vocontien (SE de la France) reprĂ©sentant les milieux pĂ©lagiques (Clue de Vergons ; Alpes-de-Haute-Provence) et hĂ©mipĂ©lagiques (Ravin des BuissiĂšres ; ArdĂšche) ont Ă©tĂ© Ă©tudiĂ©es d'un point de vue palynologique (dinoflagellĂ©s essentiellement). Bien datĂ©es par les faunes d'ammonites, ces sĂ©ries ont Ă©tĂ© recalĂ©es sur la stratigraphie sĂ©quentielle (modĂšle de Vail) dont les discontinuitĂ©s ont Ă©tĂ© reconnues in situ sur chacun des affleurements.RĂ©alisĂ© sur 105 Ă©chantillons, l'inventaire original des dinokystes de ces sĂ©ries a abouti Ă la reconnaissance de prĂšs de 190 taxons. Une biozonation basĂ©e sur les extensions stratigraphiques et les assemblages des dinokystes est proposĂ©e. Elle est comparĂ©e Ă celle fournie par les faunes d'ammonites ainsi qu'Ă la stratigraphie sĂ©quentielle : la dinozonation Ă©tablie s'avĂšre ĂȘtre une Ă©chelle biostratigraphique rarement dĂ©pendante des deux autres. Au niveau des cycles de 3Ăšme ordre, aucune relation systĂ©matique n'est observable entre les discontinuitĂ©s sĂ©quentielles et les assemblages de dinokystes. Quelques corrĂ©lations sont proposĂ©es au niveau des cycles de 2Ăšme ordre (reconnaissance de l'intervalle transgressif ; remontĂ©e gĂ©nĂ©rale du niveau marin). D'un point de vue biostratigraphique, ces rĂ©sultats locaux sont replacĂ©s dans un cadre plus global et comparĂ©s avec les dinozonations des principaux bassins du CrĂ©tacĂ© infĂ©rieur.S'appuyant sur les variations du contenu des assemblages de dinokystes, sur les variations de frĂ©quences de certains taxons, un essai de palĂ©oĂ©cologie a Ă©tĂ© rĂ©alisĂ© : certains paramĂštres environnementaux tels que variations du niveau marin, Ă©loignement Ă la cĂŽte ou salinitĂ© de surface ont pu ĂȘtre apprĂ©hendĂ©s, indiquant une remontĂ©e globale du niveau marin de la base au sommet de l'Hauterivien. Le rapport de genres Muderongia/Phoberocysta permet de proposer un schĂ©ma des variations du niveau marin, en particulier pour l'Hauterivien infĂ©rieur
Quantitative biostratigraphical ranges of some late Cenozoic species of the dinoflagellate genusSpiniferitesand taxonomic considerations
International audienceA new quantitative biostratigraphical method, based on an âindex of stratigraphical abundanceâ (ISA), has been used to refine the stratigraphical range of 50 dinoflagellate cyst taxa. Most of these correspond to Quaternary representatives of Achomosphaera or Spiniferites. Some extinct taxa are also discussed when their morphology is close to that of recent species (e.g. Spiniferites lenzii, S. twistringiensis and S. pseudofurcatus), as well as some species possibly related to the motile Gonyaulax spinifera complex. The ISAs of S. mirabilis and S. hyperacanthus are similar, as well as for S. elongatus and S. sphaericum. Although initially presumed as indicating morphotypes of a same taxon, it seems rather that the ISAs similarites must be interpreted as an indication of close ecological preferences. The emergence of forms of Spiniferites with low to absent septa appears relatively late (compared to the range of the genus), but the first occurrence of intergonal processes is relatively early, indicating that it is probably a character deeply rooted into the generic genome. The previously calculated phylogeny of some Gonyaulax motile cells shows a different tree pattern than the stratigraphical first appearance succession of their presumed cyst equivalents
La distribution des kystes de Dinoflagellés dans les sédiments hémipélagiques (ArdÚche) et pélagiques (Arc de Castellane, S.E. de la France) en domaine vocontien, du Valanginien terminal au Barrémien inférieur - Biostratigraphie et relations avec la stratigraphie séquentielle.
Two sections from the Lower Vocontian Cretaceous (SE France) representing pelagic (Clue de Vergons; Alpes-de-Haute-Provence) and hemipelagic (Ravin des BuissiĂšres; ArdĂšche) environments were studied from a palynological point of view (mainly dinoflagellates). Well dated by ammonites faunas, these sections lie on the Uppermost Valanginian - Lower Barremian time interval. The discontinuities of the Sequence stratigraphy (Vail concept) have been recognized in situ for each of the outcrops.The original inventory of dinokysts in these series, based on 105 samples, resulted in the recognition of almost 190 taxa. A biozonation based on stratigraphic extensions and dinocyst assemblages is proposed. It is compared with that provided by ammonite faunas and with Sequence stratigraphy: the dinozonation established proves to be a biostratigraphic scale that rarely depends on the other two. At the level of 3rd order cycles, no systematic relationship can be observed between sequence discontinuities and dinocyst assemblages. Some correlations are proposed for 2nd order cycles (recognition of the transgressive interval; general rise in sea level). From a biostratigraphic point of view, these local results are placed in a more global framework and compared with the dinozonations of the main basins of the Lower Cretaceous.Based on variations in the content of dinokyst assemblages and variations in the frequencies of certain taxa, a palaeoecology study was carried out: certain environmental parameters such as variations in sea level, distance from the coast and surface salinity were identified, indicating an overall rise in sea level from the base to the top of the Hauterivian. The Muderongia/Phoberocysta genera ratio can be used to propose a diagram of sea-level variations, particularly for the Lower Hauterivian.Deux coupes du CrĂ©tacĂ© infĂ©rieur vocontien (SE de la France) reprĂ©sentant les milieux pĂ©lagiques (Clue de Vergons ; Alpes-de-Haute-Provence) et hĂ©mipĂ©lagiques (Ravin des BuissiĂšres ; ArdĂšche) ont Ă©tĂ© Ă©tudiĂ©es d'un point de vue palynologique (dinoflagellĂ©s essentiellement). Bien datĂ©es par les faunes d'ammonites, ces sĂ©ries ont Ă©tĂ© recalĂ©es sur la stratigraphie sĂ©quentielle (modĂšle de Vail) dont les discontinuitĂ©s ont Ă©tĂ© reconnues in situ sur chacun des affleurements.RĂ©alisĂ© sur 105 Ă©chantillons, l'inventaire original des dinokystes de ces sĂ©ries a abouti Ă la reconnaissance de prĂšs de 190 taxons. Une biozonation basĂ©e sur les extensions stratigraphiques et les assemblages des dinokystes est proposĂ©e. Elle est comparĂ©e Ă celle fournie par les faunes d'ammonites ainsi qu'Ă la stratigraphie sĂ©quentielle : la dinozonation Ă©tablie s'avĂšre ĂȘtre une Ă©chelle biostratigraphique rarement dĂ©pendante des deux autres. Au niveau des cycles de 3Ăšme ordre, aucune relation systĂ©matique n'est observable entre les discontinuitĂ©s sĂ©quentielles et les assemblages de dinokystes. Quelques corrĂ©lations sont proposĂ©es au niveau des cycles de 2Ăšme ordre (reconnaissance de l'intervalle transgressif ; remontĂ©e gĂ©nĂ©rale du niveau marin). D'un point de vue biostratigraphique, ces rĂ©sultats locaux sont replacĂ©s dans un cadre plus global et comparĂ©s avec les dinozonations des principaux bassins du CrĂ©tacĂ© infĂ©rieur.S'appuyant sur les variations du contenu des assemblages de dinokystes, sur les variations de frĂ©quences de certains taxons, un essai de palĂ©oĂ©cologie a Ă©tĂ© rĂ©alisĂ© : certains paramĂštres environnementaux tels que variations du niveau marin, Ă©loignement Ă la cĂŽte ou salinitĂ© de surface ont pu ĂȘtre apprĂ©hendĂ©s, indiquant une remontĂ©e globale du niveau marin de la base au sommet de l'Hauterivien. Le rapport de genres Muderongia/Phoberocysta permet de proposer un schĂ©ma des variations du niveau marin, en particulier pour l'Hauterivien infĂ©rieur
RĂ©flexions sur deux pendentifs Ă âdent de requinâ trouvĂ©s Ă Burdigala (Bordeaux)
International audienc
Les phallus embarqués : une protection pour les bateaux et les marins durant l'Antiquité
Par Brice Ephrem, chercheur associĂ© Ausonius (Univ. Bordeaux Montaigne). Ce billet prĂ©sente une partie des problĂ©matiques prĂ©sentĂ©es dans le cadre dâune publication intitulĂ©e « Les pĂȘcheurs et Priape. RĂ©flexions sur les attributions marines dâun dieu ithyphallique Ă lâĂ©poque romaine » ((Dans Bouet, A., Petit-Aupert, C. Ă©d., Bibere, ridere, gaudere, studere, hoc est vivere. Hommages Ă Francis Tassaux, MĂ©moires Ausonius 53, Bordeaux, p. 145-157. URL : https://halshs.archives-ouvertes.fr/halshs-..
Les pendentifs Ă âdent de requinâ : des amulettes protectrices spĂ©cifiques Ă Burdigala (Bordeaux) ?
Brice Ephrem, Laurent Londeix Ă lâĂ©poque romaine, les dents dâanimaux portĂ©es en pendentif sont relativement courantes (FeugĂšre 2018). PercĂ©es ou associĂ©es Ă une monture mĂ©tallique, elles sont reconnues comme des amulettes Ă vocation protectrice. En fonction des interprĂ©tations, elles pouvaient symboliser la force et le courage des animaux supposĂ©s fournir une protection  ou apporter une dĂ©fense contre le danger reprĂ©sentĂ© par une dent (Deschler-Erb & GostenÄnik 2008, 300). Si les canines dâa..
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