0000000000710053
AUTHOR
François Atrops
showing 5 related works from this author
Ice age at the Middle–Late Jurassic transition?
2003
A detailed record of sea surface temperatures in the Northern Hemisphere based on migration of marine invertebrate fauna (ammonites) and isotopic thermometry (δ18O values of shark tooth enamel) indicates a severe cooling at the Middle–Late Jurassic transition (MLJT), about 160 Ma ago. The magnitude of refrigeration (1–3°C for lower middle latitudes) and its coincidence in time with an abrupt global-scale fall of sea level documented through sequence stratigraphy are both suggestive of continental ice formation at this time. Ice sheets may have developed over the high-latitude mountainous regions of Far-East Russia. The drastic cooling just post-dated the Middle–Late Callovian widespread dep…
Palynofacies and calcareous nannofossils in the Upper Kimmeridgian, southeastern Paris basin (France)
2005
AbstractThe Upper Kimmeridgian Members “Calcaires blancs supérieurs” and the “Marnes à exogyres supérieures” of the southeastern Paris basin were investigated for their palynofacies and calcareous nannofossils. These members display alternating limestone-marl lithotypes and represent shallow marine palaeoenvironments. The lower carbonate member is interpreted as a proximal palaeoenvironment (palaeobathymetry = 5 to 10 m), where storm and swell deposits were prevalent and the salinity was occasionally weak. The relative richness of brown phytoclasts in this part is favoured by good preservation related to restricted conditions. These conditions would explain the dominance of the nannofoss…
Jurassic evolution of the Arabian carbonate platform edge in the central Oman Mountains
2005
International audience; The Jurassic Sahtan Group exposed in northern Oman was deposited in shallow marine environments at the edge of the Arabian Platform facing the Neo-Tethys (Hamrat Duru Basin). The upper Sahtan Group is made up of a mixed siliciclastic-carbonate unit overlain by pure carbonate deposits, assigned to a Bathonian and Early Callovian age on the basis of brachiopods and foraminifers. These carbonate depositional systems were composed of outer oolitic shoals that underwent subaerial exposure, and a deeper, somewhat restricted, gently dipping shelf interior. Oolitic material was shed off the platform edge into the deep-sea depositional complex of the Guweyza Formation. The Sa…
A sequence analyzed from the basin to the platform : the Middle Oxfordian calcareous succession in southeastern France
2004
Abstract Middle Oxfordian sedimentation is very homogeneous in southeastern France. It is characterized by a specific alternation of marls and fine-grained limestones (G. transversarium Zone). This work shows that sets of calcareous beds allow accurate stratigraphic correlations in various paleogeographic areas, from the shallow Jura platform to the deep Dauphinois basin. Following a rifting period, this sedimentation illustrates a doming period with decreasing subsidence and water depth. This corresponds to the establishment of a wide marine area more favourable to carbonate sedimentation. Considering sequence stratigraphy, some slight variations occur in the sediment record and lead to in…
Les Gregoryceras (Ammonitina) de l'Oxfordien moyen terminal et supérieur téthysien : révision systématique, biostratigraphie et évolution.
2009
43 pages; Les Gregoryceras Spath, 1924 (Ammonitina, Peltoceratina) de la fin de l'Oxfordien moyen (sous-zone à Rotoides) et de la base de l'Oxfordien supérieur (zone à Bifurcatus) sont révisés. Les coupes ayant fourni la plupart des spécimens de ce travail (Espagne et Maghreb) sont décrites et datées sur la base de comparaisons fauniques entre les domaines téthysien et subtéthysien. Le meilleur outil pour ces corrélations est la présence du genre Gregoryceras. La succession des espèces de Gregoryceras est identique pour les deux domaines suscités, ce qui permet de compléter l'échelle biostratigraphique proposée antérieurement et parallèle à la zonation standard. Les espèces reconnues et red…