Search results for "NIV"
showing 10 items of 7213 documents
Diagenesis of clay minerals and K-bentonites in Late Permian/Early Triassic sediments of the Sichuan Basin (Chaotian section, Central China).
2014
10 pages; International audience; Detailed clay mineralogical analyses were carried out on Late Permian/Early Triassic carbonate sediments exposed on the Chaotian section (Sichuan Basin, Central China). The clay assemblages are dominantly composed of illite in platform carbonates and clay seams, and illite-smectite mixed-layers (I/S) in tuff layers (K-bentonites) intercalated in the carbonate succession. Detrital and authigenic volcanogenic clay minerals have been partially replaced through illitisation processes during burial, raising questions about diagenetic effects. The precise determination of I/S occurring in K-bentonites shows that the sediments reached a temperature of about 180 °C…
Biometric and morphometric approaches on Lower Hettangian dinosaur footprints from the Rodez Strait (Aveyron, France).
2012
9 pages; International audience; Along the southern crystalline border of the Rouergue, the detrital Sandstones-variegated Mudstones Formation and the Dolomitic Formation yields numerous dinosaur footprints from the Earliest Hettangian. Among the 25 sites distributed along the 40 km-long transect between Marcillac-Vallon and Saint-Geniez-d'Olt, two of them, Puech de Castres and Le Bouyssou, have yielded abundant ichnites in various well-defined stratigraphic units. The combined analysis of these footprints with biometric and morphometric methods (Fourier analysis) warrants their identification to Grallator, Eubrontes and Dilophosauripus. The dual methodological approach also reveals two new…
Structure and evolution of a Messinian mixed carbonate-siliciclastic platform: the role of evaporites (Sorbas Basin, South-east Spain).
2010
36 pages; International audience; The Sorbas Member is a late Messinian complex sedimentary systemthat formed immediately following deposition of the Messinian evaporites in the Sorbas Basin (South-east Spain). This work describes the sequence architecture and facies organization of a continuous kilometre long, alluvial fan to open platform transect near the village of Cariatiz in the north-east of the basin. The postevaporitic Cariatiz platform was a mixed carbonate-siliciclastic system composed of four intermediate-frequency, fifth-order depositional sequences (Depositional Sequences 1 to 4) arranged in an overall prograding trend. The intense fracturing and brecciation of these deposits …
In the aftermath of the end-Permian extinction: the microbialite refuge?
2013
7 pages; International audience; We present the first study of micro-crustaceans (ostracods) associated with microbial crusts in the aftermath of the most devastating extinction, the end-Permian extinction (EPE). These post-extinction microbialites dominated shallow shelf marine environments and were traditionally considered as devoid of any associated fauna. We present a micro-palaeontological analysis of a large record from microbial and non-microbial settings following the EPE. This dataset documents the proliferation of ostracods strictly associated with microbialites. Based on the diet of extant ostracods and uniformitarianism, we propose that the abundant microbes in the mats served a…
Permian-Triassic extinctions and rediversifications.
2015
Ammonoids were a major component of Permian marine faunas, but were on the verge of extinction during the Permian-Triassic crisis ~ 252 myr ago. Despite the severity of this extinction, their recovery was explosive in less than 1.5 myr. By Smithian time, they had already reached levels of taxonomic richness much higher than those of the Permian. The causes for the rapid Early Triassic diversification and proliferation of these organisms still remain elusive, but the evolution of their spatio-temporal diversity and disparity patterns closely correlates with the numerous environmental changes recorded during this time interval.
Revision of the genus Anasibirites Mojsisovics (Ammonoidea): An iconic and cosmopolitan taxon of the late Smithian (Early Triassic) extinction
2016
34 pages; International audience; The family Prionitidae Hyatt represents a major component of ammonoid faunas during the Smithian (Early Triassic), and the genus Anasibirites Mojsisovics is the most emblematic taxon of this family. Its stratigraphical range is restricted to the beginning of the late Smithian (Wasatchites distractus Zone). The genus is also characterized by an unusual cosmopolitan distribution, thus contrasting with most earlier Smithian ammonoid distributions that were typically restricted by latitude. Because the late Smithian witnessed an extinction of the nekton (e.g. ammonoids, conodonts) whose amplitude is equal to or larger than that of the end-Permian crisis, the nu…
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad, Morocco and their biodiversity
2018
36 pages; International audience; Trilobites are widespread in Early Devonian deposits of north Gondwana; some of the most emblematic ones were collected from the famous latest Emsian (Early Devonian) mudmound locality Hamar Laghdad in south-eastern Morocco. This locality is famous for its trilobites, especially for the conspicuous red-coloured remains of phacopid trilobites with often greenish eyes. Here, we present a taxonomic revision of the previously described trilobites from the so-called Red Fauna of Hamar Laghdad. We introduce the new taxa Harpes hamarlaghdadensis n. sp. and Morocops davidbrutoni n. sp. Phacopids dominate the trilobite assemblage from the Red Cliff at Hamar Laghdad …
Discovery of an Autunian macroflora and lithostratigraphic re-investigation on the western border of the Lodève Permian basin (Mont Sénégra, Hérault,…
2013
11 pages; International audience; Re-investigation of the western edge of the Lodève basin allows reassignment of one sandstone-conglomerate formation previously identified as "terminal Stephanian" to Early Autunian. The existence of two unconformable (Stephanian and Autunian) megasequences, separated by a sedimentary gap, which had been rejected, is thus re-affirmed. The authors also found, less than 20 m above the basal Autunian conglomerate, a macroflora with taxa characteristic of the famous Tuilières flora from a site, located in the eastern part of the basin near Lodève, in the Grey Autunian group. This confirms that the new Mont Sénégra fossiliferous beds belong to the Lower Autunian…
Lowermost Jurassic dinosaur ecosystem from the Bleymard Strait (southern France): sedimentology, mineralogy, palaeobotany and palaeoichnology of the …
2021
AbstractWe report the first Hettangian theropod tracksite (~200 Ma) yielding a rich accumulation of plant remains from the Bleymard Strait (southern France). It constitutes an excellent opportunity to reconstruct lowermost Jurassic ecosystems hosting dinosaurs and which are still poorly documented in this area. Two morphotypes of tridactyl tracks are distinguished. They share similarities with Grallator and Kayentapus. Plant-bearing beds yield abundant leafy axes (Pagiophyllum peregrinum), male cones (Classostrobus sp.), wood (Brachyoxylon sp.) and pollen of conifers (Classopollis classoides). Sedimentological, petrological and mineralogical analyses demonstrated that, in the Dolomitic Form…
Terrestrial plants and marine algae from the Late Jurassic lithographic limestone of the Causse Méjean (Lozère, southern France)
2016
International audience; A new Late Jurassic flora was discovered in the fossiliferous lithographic limestone of the Causse Méjean, Lozère (southern France). It consists of the first Kimmeridgian/Tithonian plants from this area. Fossil plants are represented by megaremains preserved as impressions. This flora shows a co-occurrence of terrestrial plants and marine algae. The land plants include vegetative remains ascribed to bennettitaleans (Zamites Brongniart, 1828), conifers (Brachyphyllum Brongniart, 1828), and pteridosperms (Cycadopteris Zigno, 1853). Marine algae were ascribed to dasyclads (Goniolina D’Orbigny, 1850). Lithological and palaeontological features suggest preservation in a f…