Search results for "OBI"
showing 10 items of 18972 documents
Les ammonites du Pliensbachien du jebel Bou Rharraf (Haut Atlas oriental, Maroc).
2011
60 pages; International audience; L'originalité des dépôts sédimentaires et des faunes d'ammonites du jebel Bou Rharraf repose sur la présence de faciès « Ammonitico Rosso », les plus occidentaux connus pour le Pliensbachien, une forte diversité des Phylloceratida (Phylloceras, Calaiceras, Zetoceras, Partschiceras et Juraphyllites) et une disparité morphologique importante chez les Galaticeras, Miltoceras et les Tauromeniceras. Si quelques formes, telles que Miltoceras taguendoufi et Mauretaniaceras elmii nov. gen., nov. sp. ont un cachet endémique très affirmé, les faunes du Pliensbachien du Haut Atlas oriental sont classiques pour la marge sud de la Téthys occidentale. Trois genres (Callo…
Pseudoskirroceras, a remarkable but poorly known Early Pliensbachian Tethyan ammonite genus: New data from the High Atlas (Morocco).
2007
13 pages; International audience; The discovery of new Early Pliensbachian ammonite faunas in Central High Atlas (Morocco) allows the re-examination of the taxonomic, stratigraphical and palaeogeographical framework of the genus Pseudoskirroceras, an intriguing but until now poorly known Tethyan taxon. For the first time, several specimens of Pseudoskirroceras mastodon (Fucini, 1935) the type species of the genus, have been collected in a well-known stratigraphical context. This material allows the evaluation of intra-specific variability and consequently the assessment of the taxonomical relevance of various geometrical and ornamental features. The best diagnostic features are the clearly …
COMMENT TO LEHRMANN ET AL. NEW SECTIONS AND OBSERVATIONS FROM THE NANPANJIANG BASIN, SOUTH CHINA
2016
In the study of Earth-surface environmental processes during the events associated with the Permian–Triassic boundary, a key issue is the nature of the latest Permian pre-extinction surface in shallow marine limestones in numerous sites, principally within the Tethyan realm. Sediments below this surface pre-date the extinction event, so that the limestones comprising these latest Permian facies contain diverse fossil remains of organisms that lived just before the extinction. At all reported sites, this surface is disconformably overlain by post-extinction sediments, which contain microbialites in many places, particularly in Tethys. The nature of the youngest pre-extinction surface remains…
Ammonite paleobiogeography during the Pliensbachian-Toarcian crisis (Early Jurassic) reflecting paleoclimate, eustasy, and extinctions.
2011
14 pages; International audience; The Pliensbachian-Toarcian crisis (Early Jurassic) is one of the major Mesozoic paleoecological disturbances when ca. 20% of marine and continental families went extinct. Contemporaneously, profound paleobiogeographical changes occurred in most oceanic domains including a disruption of ammonite provincialism during the Early Toarcian. Here, we quantitatively reappraise the structure and evolution of paleobiogeographical patterns displayed by ammonite faunas before, during, and after the biological crisis, over a time-interval including 13 biochronozones. The high-resolution study presented here involves the use of hierarchical Cluster Analyses, non-metric M…
Geographical and bathymetric distribution of foraminiferal assemblages from the Alboran Sea (western Mediterranean)
2018
A total of 176 surface sediment samples, recovered in the Alboran Sea by the oceanographic vessel Vizconde de Eza during the 2002 and 2003 campaigns, were analysed for their foraminiferal content. Planktonic and benthic foraminifera were picked up, studied and classified. In addition, a series of diversity indices were calculated. An attempt was made to correlate diversity (Fisher alpha index) with longitude, latitude and depth. Planktonic assemblages are strongly dominated by the species Globorotalia inflata (d’Orbigny) together with Globigerina bulloides d’Orbigny. Correlation analysis show only a weak relation between planktonic foraminiferal diversity and both longitude and distance to …
The lower Ovetian Stage (lower Cambrian Stage 3) trilobite zonation in Spain and correlation with West Gondwana
2020
New trilobites from the upper part of the Pusa Formation (base of Cambrian Stage 3) in Central Spain are studied for their systematic and biostratigraphic significance. The trilobites Proabadiella ...
Upper Ovetian trilobites from Spain and their implications for the palaeobiogeography and correlation of the Cambrian Stage 3 in Gondwana
2016
Abstract The upper part of the La Herreria Formation in Los Barrios de Luna (Leon Province, N Spain) has been revised from a palaeontological and biostratigraphical point of view. Two stratigraphic sections have been studied including their trilobite and ichnofossils contents. The ichnofossil assemblages have a high diversity of species characterising the Cruziana ichnofacies, suggesting a shallow sublittoral environment for the upper part of the La Herreria Formation. The trilobites species recognised are Lunagraulos antiquus , Dolerolenus formosus , Dolerolenus longioculatus , Lunolenus lunae , Metadoxides richterorum , Metadoxides armatus and Sardaspis ? sp. from the upper Ovetian (lower…
Multistratigraphic records of the Lower Cretaceous (Valanginian–Cenomanian) Puez key area in N. Italy
2016
Abstract We present a stratigraphic investigation of a Hauterivian to Cenomanian hemipelagic succession from Col Puez, in the Dolomites (Southern Alps, northern Italy). A composite section of seven segments was studied with bio-, magneto-, and chemostratigraphy, which enabled detailed and robust age calibration of the Puez succession. It also revealed the paleoceanographic history and helped identify the important global climatic events of that period. The age of the Lower Cretaceous Puez Formation in the Dolomites is refined as late Hauterivian to early Cenomanian. Ammonoids provide a detailed biostratigraphic subdivision that forms the basis for analyses of the faunal distribution and the…
La faune ammonitique des marnes à fossiles ferrugineux de la région de Niort, France (Oxfordien inférieur, Zone à Cordatum, Sous-Zone à Cordatum)
2009
21 pages; Une nouvelle récolte d'ammonites dans les marnes à ammonites ferrugineuses de la région de Niort (France), autrefois étudiées par de GROSSOUVRE (1922), apporte de très nombreuses informations biostratigraphiques, paléoenvironnementales et paléobiogéographiques. La faune est datée de l'Oxfordien inférieur : Zone à Cordatum, Sous-Zone à Cordatum, partie inférieure probable. De plus, elle est unique en Europe occidentale 1) par les espèces trouvées -dont certaines ne semblent connues que dans ce gisement- 2) par la domination très atypique du binôme Taramelliceras - Creniceras qui représente les 2/3 des individus. Enfin, le spectre faunique plaide en faveur d'un milieu de plate-forme…
Soil physicochemical and microbial drivers of temperature sensitivity of soil organic matter decomposition under boreal forests
2020
Abstract Soil organic matter (SOM) in boreal forests is an important carbon sink. The aim of this study was to assess and to detect factors controlling the temperature sensitivity of SOM decomposition. Soils were collected from Scots pine, Norway spruce, silver birch, and mixed forests (O horizon) in northern Finland, and their basal respiration rates at five different temperatures (from 4 to 28 °C) were measured. The Q10 values, showing the respiration rate changes with a 10 °C increase, were calculated using a Gaussian function and were based on temperature-dependent changes. Several soil physicochemical parameters were measured, and the functional diversity of the soil microbial communit…