Search results for "DIVERSITY"

Prehistoric palaeodemographics and regional land cover change in eastern Iberia

2019

Much attention has been placed on the drivers of vegetation change on the Iberian Peninsula. While climate plays a key role in determining the species pools within different regions and exerts a strong influence on broad vegetation patterning, the role of humans, particularly during prehistory, is less clear. The aim of this paper is to assess the influence of prehistoric population change on shaping vegetation patterns in eastern Iberia and the Balearic Islands between the start of the Neolithic and the late Bronze Age. In all, 3385 radiocarbon dates have been compiled across the study area to provide a palaeodemographic proxy (radiocarbon summed probability distributions (SPDs)). Modelled…

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…

Cultural evolution and environmental change in Central Europe between 40 and 15 ka

2020

The role of environmental change in the evolution of cultural traits is a topic of long-standing scientific debate with strongly contrasting views. Major obstacles for assessing environmental impacts on the evolution of material culture are the fragmentary nature of archaeological and – to a somewhat lesser extent – geoscientific archives and the insufficient chronological resolution of these archives and related proxy data. Together these aspects are causing difficulties in data synchronization. By no means does this paper attempt to solve these issues, but rather aims at shifting the focus from demonstrating strict chains of causes and events to describing roughly contemporaneous developm…

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…

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 …

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…

Les forages de Juzanvigny (Aube, France): lithobiostratigraphie des formations du Barrémien à l'Albien moyen dans l'est du bassin de Paris et datatio…

2017

RESUME Dans le departement de l'Aube, region stratotypique de l'etage Albien, plusieurs forages realises en 2013 ont traverse la plus grande partie des Argiles tegulines de Courcelles ou « Gault » auct. (Albien inferieur et moyen), les Sables verts de l'Aube (Aptien superieur), les Argiles a Plicatules (Aptien inferieur), les Sables et argiles bariolees (Barremien superieur) et la partie superieure des Argiles ostreennes (Barremien inferieur). Une description lithologique detaillee de la succession est realisee dans le but d'ameliorer la connaissance du Cretace inferieur de la bordure orientale du bassin de Paris dont les affleurements sont peu nombreux et discontinus. En ce qui concerne l'…

Comments on: A review of the evolution, biostratigraphy, provincialism and diversity of Middle and early Late Triassic conodonts

2016

Unravelling extrinsic and intrinsic factors of the early Palaeozoic diversification of blastozoan echinoderms

2010

19 pages; International audience; The Subphylum Blastozoa represents more than one third of the early Palaeozoic echinoderm fauna. A comprehensive database including all records of blastozoans was built to provide quantitative analyses of palaeogeography and diversity patterns and processes, for the 10 classes currently included in this subphylum during the early Palaeozoic. The global pattern of taxonomic diversity shows two peaks during the Cambrian Series 3 and the Late Ordovician intervals. In Cambrian times, the high taxonomic diversity seems to be related with a high turnover rate and a high endemicity of blastozoan genera, whereas in Ordovician times, the rise in diversity is associa…