Search results for "Stage"
showing 10 items of 1393 documents
Report on the 4th International Meeting of the IUGS Lower Cretaceous ammonite working group, the "Kilian Group" (Dijon, France, 30th August 2010).
2011
8 pages; International audience; The 4th Kilian Group meeting (Dijon, France, 30th August 2010) focused on the Aptian and Albian Stages. For the Aptian, a two-fold division of the stage was adopted for the Mediterranean area with a boundary between the Dufrenoyia furcata and Epicheloniceras martini Zones. The main changes to the zonal scheme concern the Lower Aptian with: the introduction of a Deshayesites luppovi Subzone in the upper part of the Deshayesites oglanlensis Zone; the replacement of Deshayesites weissi by Deshayesites forbesi as new indexspecies of the second interval zone; the introduction of a Roloboceras hambrovi Subzone in the upper part of the D. forbesi Zone; and the subd…
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 …
Early evidence of fire in south-western Europe: the Acheulean site of Gruta da Aroeira (Torres Novas, Portugal)
2020
The site of Gruta da Aroeira (Torres Novas, Portugal), with evidence of human occupancy dating to ca. 400 ka (Marine Isotope Stage 11), is one of the very few Middle Pleistocene localities to have provided a fossil hominin cranium associated with Acheulean bifaces in a cave context. The multi-analytic study reported here of the by-products of burning recorded in layer X suggests the presence of anthropogenic fires at the site, among the oldest such evidence in south-western Europe. The burnt material consists of bone, charcoal and, possibly, quartzite cobbles. These finds were made in a small area of the cave and in two separate occupation horizons. Our results add to our still-limited know…
Stage boundaries, global stratigraphy, and the time scale: towards a simplification
2004
International audience; This paper examines four facets of stratigraphic terminology and usage considered faulty and proposes corrective measures. The four perfectible areas are: (1) The system of dual nomenclature requiring discrete terminologies for the superpositional and temporal aspects of rock units. (2) The premise that a GSSP establishes the base of a stage as being coincident with the top of the preceding stage rather than simply defining it as the boundary between stages. (3) The rejection of supplementary (auxiliary) sections that would broaden the knowledge of a GSSP and enlarge the area in which it is easily usable. (4) The current dual system of nomenclature for Precambrian an…
Challenges in defining the base of Cambrian Series 2 and Stage 3
2017
Formal subdivision of the Cambrian System into four series and ten stages is in progress. The base of Cambrian Stage 3 (provisional), which is conterminous with the base of Cambrian Series 2 (provisional), is expected to be placed at a horizon close to the first appearance of trilobites, which marks the onset of the largest phase of the Cambrian explosion. Conceptually, an ideal boundary position would be marked by a significant and globally recognizable bioevent that divides the lower part of the Cambrian System into a sub-trilobitic Terreneuvian Series and a trilobite-dominated Series 2. If the level is to be identified principally through biostratigraphic means, its position also needs t…
Pseudoshasticrioceras bersaci nov. sp. (Ammonoidea, Gassendiceratinae), and new ammonite biohorizon for the Upper Barremian of southeastern France
2009
International audience; Research in the Feraudianus Subzone of the Sartousiana Zone of the Barremian stage led to the discovery of a new species of Pseudoshasticrioceras: P. bersaci nov. sp. Its study provides evidence concerning the developments of the latest Gassendiceratinae BERT et alii, 2006, and the relationship between the genus Pseudoshasticrioceras DELANOY, 1998, and Gassendiceras BERT et alii, 2006. In particular, this new species is derived from Pseudoshasticrioceras magnini (DELANOY, 1992) by a minor revision in the processes of ontogenesis (retardation of ornamentation - neoteny). However, the evolution towards Pseudoshasticrioceras autrani DELANOY, 1998, implies a "failure" in…
Integrated bio- and carbon-isotope stratigraphy of the Upper Cretaceous Gurpi Formation (Iran): A new reference for the eastern Tethys and its implic…
2018
29 pages; International audience; A high-resolution stratigraphic analysis of the Upper Cretaceous Gurpi Formation has been undertaken in the Shahneshin section (Zagros Basin, Iran). New results on calcareous nannofossils, planktic foraminifers, dinoflagellate cysts and high-resolution carbon and oxygen stable isotopes form the basis of a reference section for the eastern Tethys that spans the upper Coniacian to the late Danian. Carbon-isotope correlation to Gubbio, Italy and the NW German chalk allows for the identification of many isotopic events as well as for the definition of new events in the Campanian and Maastrichtian. Our results allow for a review of the accurate position of the C…
OnCallavia(Trilobita) from the Cambrian Series 2 of Iberia with systematic status of the genus
2021
Olenellid trilobites from the lower Cambrian of the Iberian Peninsula are very scarce and poorly studied, making them difficult to compare with defined species and to include in biostratigraphic and paleobiogeographic analyses. Based on newly collected specimens, we revise the species ‘Callavia? lotzei’ Richter and Richter, 1941 from the ‘Cumbres beds’ of Cumbres de San Bartolomé and the ‘Herrerías shale’ of Cañaveral de León, Sierra del Bujo, and Hinojales (Huelva, Spain), and ‘Paradoxides choffati’ Delgado, 1904 from the Vila Boim Formation of Elvas (Portugal). The new material indicates that Callavia? lotzei is a junior synonym of ‘P. choffati.’ The Iberian species are here assigned to C…
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…