Time filter

Source Type

A fragmentary bone from the Dinosaur Park Formation (Campanian) of Dinosaur Provincial Park (Alberta, Canada), originally described as a pterosaur tibiotarsus, is reinterpreted as the distal end of the tibiotarsus of a basal bird, probably an enantiornithine, on the basis of several distinctive characters. It is the first report of such a bird from the Dinosaur Park Formation and shows that this group was present, together with various more derived ornithurines, in the relatively high-latitude environments of Late Cretaceous western Canada. © Cambridge University Press 2010. Source

Aubourg C.,Cergy-Pontoise University | Aubourg C.,French National Center for Scientific Research | Pozzi J.-P.,CNRS ENS Geology Laboratory
Earth and Planetary Science Letters

We investigate the effects of burial and moderate experimental heating on claystones from three regions with different degrees of maturation: immature (burial temperature ~40°C) of Bure Callovo-Oxfordian claystones in the Basin of Paris (France); early mature (burial temperature ~85°C) of Opalinus Lower Dogger claystones from the Mont Terri anticline in front of the Jura fold belt (Switzerland); and mature to overmature (burial temperature <170°C) of Chartreuse Callovian-Oxfordian claystones from Chartreuse Sub-Alpine chains. To have information about the nature of the magnetic assemblage, we perform low-temperature (10K-300K) investigation of an isothermal remanent magnetization. In a first set of laboratory heating experiments, we aim to impart a chemical remanent magnetization (CRM) at 95°C for several weeks in Bure and Opalinus claystones. Thermal demagnetization of the CRM reveals that magnetite is formed by heating the Opalinus claystones while an assemblage of magnetite and iron sulphide is formed in Bure claystones. Further, we document the appearance of a magnetic transition at ~35K in Bure claystones after heating. We name this transition the P-transition and we propose that it is related to the formation of fine-grained pyrrhotite (Fe7S8). The P-transition is also detected in early mature to mature Opalinus and Chartreuse claystones. We conduct additional experimental heating of natural Opalinus claystones. One set of experiments is referred to as short-term heating (1h) from 100°C to 200°C. It is dedicated to an investigation of the effect of short-lived heating processes in geology. A second set of heating experiments is designed to approach burial conditions using a gold capsule. In burial-like experiments, we heated Opalinus claystones from 150°C to 250°C for several weeks under a pressure of 100MPa. In both experiments, we observe a correlative diminution of the pyrrhotite signature at 35K with increasing temperature. We interpret this trend as the appearance of magnetite. We derive a parameter PM from the warming curve of a saturated isothermal remanent magnetization acquired at 10K (ZFC). We report on a consistent evolution of PM with temperature in the range of 40°C to 250°C, including natural samples, heated samples at 95°C, and burial-like heated samples. PM first increases between ~40°C up to ~85°C, implying that pyrrhotite gradually dominates the magnetic assemblage at low temperature. For temperatures above 85°C, PM decreases up to 250°C, implying that the formation of magnetite gradually overshadows the magnetic input of pyrrhotite. PM values obtained from mature to overmature claystones from the Chartreuse are lower than the PM values obtained from the burial-like heated Opalinus claystones, suggesting that the formation of magnetite is driven by kinetics. The continuous trend of the PM parameter suggests that the magnetic properties of pyrrhotite-magnetite claystones can be used to infer paleo-temperatures and we propose to name this geothermometer MagEval. © 2010 Elsevier B.V. Source

Buffetaut E.,CNRS ENS Geology Laboratory
Annales de Paleontologie

Samrukia nessovi was described as a giant bird on the basis of a pair of mandibular rami from the Late Cretaceous of Kazakhstan. Anatomical comparison shows that the specimen bears no distinctive avian characters, and that its purported autapomorphies, as well as all its other characters, are in fact well-known pterosaurian features. The published phylogenetic analysis placing Samrukia within Aves is flawed because it did not include pterosaurs. Samrukia nessovi is clearly a large pterosaur, not a giant bird. © 2011 Elsevier Masson SAS. Source

Buffetaut E.,CNRS ENS Geology Laboratory | Angst D.,CNRS Geological Laboratory of Lyon: earth, planets and environment
Geological Magazine

A large heterocoelous cervical vertebra from the Late Cretaceous of Cruzy (Hérault, southern France) is described and referred to the giant bird Gargantuavis philoinos Buffetaut & Le Loeuff, 1998, confirming its avian nature. Gargantuavis appears to have been a long-necked bird with possibly a relatively small skull. Derived features such as heterocoely suggest that Gargantuavis was an advanced ornithuromorph, close to ornithurines. Copyright © 2012 Cambridge University Press. Source

Pawlyta M.,Silesian University of Technology | Rouzaud J.-N.,CNRS ENS Geology Laboratory | Duber S.,University of Silesia

The aim of this paper is to describe carbonisation and partial graphitization of carbon blacks (CB). Raman spectrometry is used to investigate a series of five CB grades during heat treatment (up to 2600 °C). Obtained results are discussed by comparing Raman data with X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) observations. For Raman spectra interpretation, the usual curve fitting method proposed by Sadezky et al. for soot and disordered carbonaceous material is applied. As the same procedure can be applied over all the heat-treatment temperature range, the determination of band parameters from five band decompositions appears to be the most convenient to follow the CB's structural improvement. We demonstrate that only a partial graphitization takes place and the graphitizability is limited by the diameter of the primary particles. Our observations generalize the results obtained for cokes: graphitization degree of carbonaceous materials after the heat-treatment is limited by the diameter of the volumes within polyaromatic layers are oriented in parallel. © 2014 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations