Search results for "BIOSTRATIGRAPHY"
showing 10 items of 138 documents
Dolomitization as an eventualdetermining factor in the colour alteration index (CAI)
1993
Abstract The Colour Alteration Index of conodonts (CAI) is indicative of the degree of alteration of organic material that exists in the interior of the conodonts. This CAI is used ordinarily in the determination of paleotemperatures. More frequent findings of abnormally high CAI values, equivalent to paleotemperatures that are not compatible with temperatures obtained by other more trustworthy methods, has taken us to use values not superior to 6 for the establishment of paleotemperatures. The CAI values measured in specimens proceding from dolostones in the Iberian Range (Spain) show in this way a certain degree of incompatibility with geological data. These anomalous values are the conse…
Early Jurassic normal faulting in a carbonate extensional basin: characterization of tectonically driven platform drowning (High Atlas rift, Morocco).
2009
18 pages; International audience; This paper describes a tectonostratigraphic model of the synrift evolution of the Early Jurassic High Atlas rift of Morocco. The model is constrained by mapping of a set of inverted extensional blocks, by facies analysis of carbonate platform and turbiditic to hemipelagic synrift deposits, and by high-resolution (n 3 100 ka) biostratigraphy of the Early Jurassic succession. The chronostratigraphic packages of the High Atlas of Rich vary significantly in thickness, facies and architecture from one tectonic block to another. Our study shows how synrift strain varied in space and time over a long time interval (14 Ma) around the High Atlas rift. Initially, in …
Calculating the long-term displacement rates of a normal fault from the high-resolution stratigraphic record (early Tethyan rifting, French Alps)
2003
Displacement rates of normal faults deduced from stratigraphic data are often unreliable. Here we calculate the velocity of motion on a normal fault from the variations in accommodation potential on both sides of the fault within a highresolution time-frame established by biostratigraphy and physical stratigraphy. Our example is the Ornon normal fault bounding the Early Jurassic Bourg-d’Oisans Basin formed during Tethyan rifting. We show that motion on the fault was discontinuous when examined at high resolution and over a long time interval. During a first interval (Hettangian to Sinemurian Arietites bucklandi zone) a low rate of displacement (= 202–423 m Myr -1 ) coeval with diffused exte…
Sinemurian to lowermost Toarcian ammonites of the Brescian Prealps (Southern Alps, Italy): preliminary biostratigraphical framework and correlations.
2009
10 pages; International audience; A set of 28 ammonite biohorizons or faunal assemblages is proposed for the Sinemurian, the Pliensbachian and the lowermost Toarcian of the Brescian Prealps, in part based on the published data of the authors of this contribution and partly on new results, derived both from recent field investigations and from the study of the historical collection of Lower Jurassic ammonites preserved in the Museum of Natural Sciences of Brescia (Northern Italy). The biohorizons are present in the Liassic carbonate succession of the Brescian Prealps, cropping out between the eastern surroundings of Brescia (Botticino), to the east, and Lake Iseo, to the west. Since the Hett…
The Upper Sinemurian ammonite succession in the Sierra Madre Oriental (Mexico).
2009
International audience; In the Sierra Madre Oriental (Mexico), the biostratigraphic subdivision of the Upper Sinemurian can be refined. It has been possible to differentiate 11 horizons from the upper Obtusum Zone to the top of the Raricostatum Zone which are correlated with the NW European standard zonation. The index species of each horizon is figured.
Revision of asterolepidoid antiarch remains from the Ogre Formation (Upper Devonian) of Latvia
2020
The Frasnian (Upper Devonian) antiarch Walterilepis speciosa was first described in 1933 (as Taeniolepis) on the basis of a single specimen. The newly collected material has allowed the head to be described in a more detail, especially the nuchal and paranuchal plates. Other newly described elements include bones of the pectoral appendages and trunk armour, demonstrating a rather high and short trunk armour. The shape and proportions of the head and trunk armour suggest the attribution of Walterilepis to the family Pterichthyodidae; it is most probably closely related to Lepadolepis from the Late Frasnian of Germany. Whilst W. speciosa is endemic to the Latvian part of the Baltic Devonian B…
Synthesis of recent stratigraphic data on bathonian to oxfordian deposits of the eastern Paris basin
2007
International audience
A database of Triassic conodonts from a comprehensive revisión of literature
2013
The revision of a comprehensive amount of bibliography has made possible the development of a database containing the stratigraphic ranges of the conodont species from the uppermost Permian and the Triassic, with a total of 336 species in 52 genera. This database is aimed at biostratigraphy and studies related to biological, evolutional and palaeodiversity dynamics. La revisión de una amplia cantidad de bibliografía ha hecho posible el desarrollo de una base de datos en la que figuran los rangos estratigráficos de las especies de conodontos presentes desde el Pérmico superior y el Triásico, con un total de 336 especies y 52 géneros. Esta base de datos está dirigida a la bioestratigrafía y a…
The Jaguar - Panthera onca gombaszoegensis (Kretzoi, 1938) (Carnivora: Felidae) in the late lower pleistocene of Akhalkalaki (south Georgia; Transcau…
2001
Abstract A lower hemimandibula of a pantherine cat of Akhalkalaki (south Georgia, Transcaucasia) is re-examinated. The fossil originates from lacustrine sediments of late Lower Pleistocene age (0.9 − 0.8 Ma B.P.) above the Jaramillo polarity subzone. A tooth-by-tooth analysis comparing the fossil with Lower and Middle Pleistocene lions, tigers and jaguars and Holocene southwest Asian lions assigns it to the Eurasian jaguar, Panthera onca gombaszoegensis. Palaeoenvironmental reconstruction indicates a dry, warm meadow-steppe influenced by montane condition, with permanent water bodies present. This is consistent with the strong open-water affinities of the modern jaguar. The morphological pr…
Coupures morphologiques et biochronologie chez les Kosmoceratinae de l'Est de la France (Callovien inférieur pp. à Callovien supérieur pp.)
1998
Abstract For the first time in eastern France, a detailed succession of the uppermost Lower Callovian to Lower Upper Callovian Kosmoceratinae is presented, according to the fossils collected in situ at Blye (Jura, France). It is compared with the abundant data from Champagne and Bourgogne. These ammonites may allow more accurate correlations between the subboreal and subtethysian biostratigraphical frameworks. They record numerous morphological changes, sometimes different from those generally accepted. They allow the precise recognition of the limits of the biostratigraphical units, and the definition of successive faunal units available in the lowermost Upper Callovian.