Search results for "Biozone"
showing 8 items of 28 documents
Sucesión de Polygnátidos (Conodontos) del Emsiense (Devónico Inferior) en los Pirineos Centrales Españoles
2011
A comprehensive conodont study of five sections of Emsian age, carried out in the Spanish Central Pyrenees, has revealed an important succession of polygnathids that can be used for identifying basal boundaries of globally recognized biozones. This succession consists of Polygnathus excavatus excavatus, Po. gronbergi, Po. nothoperbonus, Po. mashkovae, Po. laticostatus, and the new species Polygnathus luciae that allows the identification of the excavatus, nothoperbonus and laticostatus Zones. The nothoperbonus Zone is further subdivided into Lower and Upper nothoperbonus subzones, relying upon the lowest occurrence of Po. mashkovae. These biostratigraphic data from the Spanish Central Pyren…
Biogeography of the Pleistocene pleniglacial malacofaunas in Europe. Stratigraphic and climatic implications
1990
Abstract As determined by Lozek, malacological associations are significant of a particular vegetal environment. In Quaternary sequences, different types of associations are recognized which can be assimilated to the present types of malacofaunas. There are associations of grass group, of forest group and of the ecotone of these two biogeographical entities. On the European scale, in Pleistocene sequences, the interglacial faunas indicate similarly the same differences as today, being of stratigraphic interest. On the contrary, pleniglacial faunas, which are mainly preserved in the loess belt, seemed not interesting for stratigraphy since they indicate more generalized and more homogeneous …
Middle Eocene calcareous nannofossils in the Jaca transect (South-central Pyrenees Eocene Basin, Aragón river valley, Huesca)
2020
The calcareous nanoplankton is studied from the base of the turbidite systems of the Upper Hecho Group (Jaca Basin, middle Eocene of the South-central Pyrenean Basin) up to the Gracionepel instabilities, within the Larres slope Marls. This new chronostratigraphic contribution is of crucial importance for the improvement of the detailed temporal and spatial correlation framework of the genetically related depositional systems at basin scale. The calcareous nanofossil assemblage is largely dominated by Coccolithus pelagicus , C. formous as well as different species of Reticulofenestra , accompanied by occasional specimens of several species of Sphenolithus and Chiasmolithus . The results obt…
Early–middle Jurassic lytoceratid ammonites with constrictions from Morocco: palaeobiogeographical and evolutionary implications.
2008
13 pages; International audience; The ammonite genus Alocolytoceras Hyatt, 1900 is an uncommon lytoceratid with distinctive shell ornament. A set of 58 specimens, recently collected at Amellago in the central High Atlas (Morocco), has enabled us to trace a succession of three species over eight biozones from the Toarcian to the Aalenian. Two specimens from the Lusitanian Basin are added for comparison. Following a review of the genus, based on original specimens and data from the literature, seven species are considered valid. A palaeobiogeographical synthesis of 13 regions demonstrates irregular distribution patterns over time, with a constant presence in the south-west Tethys and an insta…
New insights into the diversity dynamics of Triassic conodonts
2013
International audience; In this paper, we examine the diversity trends and the evolutionary patterns of Triassic conodonts through a newly powered large-scale data-set compiled directly from the primary literature. Paleodiversity dynamics analyses have been undertaken by working at the species level and using a system of time units based on biozone subdivisions for a fine temporal level resolution. The role of heterogeneous duration of taxa in diversity estimates has been evaluated through the probabilistic profiles. Results reveal three different stages in the diversity behaviour of Triassic conodonts from standing metrics delimited by two inflections at the mid-Anisian and mid-Carnian. Su…
Le dimorphisme chez Perisphinctes (Properisphinctes) cf. bernensis de Loriol (Oxfordien inférieur, région de Cracovie, Pologne)
2004
Resume Une population d'ammonites rapportee a Perisphinctes (Properisphinctes) cf. bernensis de Loriol 1898, d'âge Oxfordien inferieur (zone a Mariae), a ete trouvee dans la region de Cracovie, dans le Sud de la Pologne. L'etude de ces formes a permis de montrer l'existence, au sein de cette espece, d'un dimorphisme microconque/macroconque, qui etait soupconne, mais non encore demontre avec certitude. Cette espece, connue en Europe uniquement par des individus incomplets, precise notre connaissance des perisphinctides de la base de l'Oxfordien inferieur. Pour citer cet article : R. Tarkowski, D. Marchand, C. R. Palevol 3 (2004).
Emersion generalisee intra-maastrichtienne de la plate-forme de Gavrovo-Tripolitza (Grece); effets sur les populations de foraminiferes Rhapydioninin…
2001
Abstract The reliability of biostratigraphic correlations in neritic carbonate platforms is often questioned because the benthic fauna on which biozonation is based are particularly sensitive to environmental change. It is crucial to know whether a population change corresponds strictly to a facies change. Conversely, there arise the questions of determining how populations are renewed over time and how new species appear even if facies associations remain unchanged. This is the case with the Gavrovo-Tripolitza zone of Greece, an isolated shallow carbonate platform surrounded by two oceanic domains (Pindos-Olonos Zone and Ionian Zone). The absence or scarcity of faunas generally used in Upp…
Nuevas faunas de micromamíferos del Terciario continental de la Depresión Intermedia (provincia de Cuenca, España centro-oriental)
1986
In this paper the fossil content of nine new micromammal bearing localities and that of 15 levels in a borehole from the Loranca Basin (eastern Tague Basin, Prov. of Cuenca) is described. The age ranges from early Arvernian (Late Oligocene) to Turolian (Late Miocene). 47 rodent and lagomorph taxons have been found which are arranged in 8 biostratigraphic units. The Loranca-2 borehole contains 15 fossiliferous levels covering the Upper Oligocene/Lower Miocene. These additional data complete the faunal sequence published by Díaz & López(1919). The stratigraphic framework of the basin needs a revision because of the new faunal data.<br><br>Se presenta una serie de 9 nuevos yaci…