Stumpf A.,University of Strasbourg |
Malet J.-P.,University of Strasbourg |
Allemand P.,CNRS Geological Laboratory of Lyon: earth, planets and environment |
Ulrich P.,University of Strasbourg
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2014
Recent advances in image-matching techniques and VHR satellite imaging at submeter resolution theoretically offer the possibility to measure Earth surface displacements with decimetric precision. However, this possibility has yet not been explored and requirements of ground control and external topographic datasets are considered as important bottlenecks that hinder a more common application of optical image correlation for displacement measurements. This article describes an approach combining spaceborne stereo-photogrammetry, orthorectification and sub-pixel image correlation to measure the horizontal surface displacement of landslides from Pléiades satellite images. The influence of the number of ground-control points on the accuracy of the image orientation, the extracted surface models and the estimated displacement rates is quantified through comparisons with airborne laser scan and in situ global navigation satellite measurements at permanent stations. The comparison shows a maximum error of 0.13. m which is one order of magnitude more accurate than what has been previously reported with spaceborne optical images from other sensors. The obtained results indicate that the approach can be applied without significant loss in accuracy when no ground control points are available. It could, therefore, greatly facilitate displacement measurements for a broad range of applications. © 2014 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).
Gomez B.,CNRS Geological Laboratory of Lyon: earth, planets and environment |
Daviero-Gomez V.,CNRS Geological Laboratory of Lyon: earth, planets and environment |
Coiffard C.,Leibniz Institute for Evolution and Biodiversity Science |
Martin-Closas C.,University of Barcelona |
Dilcher D.L.,Indiana University Bloomington
Proceedings of the National Academy of Sciences of the United States of America | Year: 2015
The early diversification of angiosperms in diverse ecological niches is poorly understood. Some have proposed an origin in a darkened forest habitat and others an open aquatic or near aquatic habitat. The research presented here centers on Montsechia vidalii, first recovered from lithographic limestone deposits in the Pyrenees of Spain more than 100 y ago. This fossil material has been poorly understood and misinterpreted in the past. Now, based upon the study of more than 1,000 carefully prepared specimens, a detailed analysis of Montsechia is presented. The morphology and anatomy of the plant, including aspects of its reproduction, suggest that Montsechia is sister to Ceratophyllum (whenever cladistic analyses are made with or without a backbone). Montsechia was an aquatic angiosperm living and reproducing below the surface of the water, similar to Ceratophyllum. Montsechia is Barremian in age, raising questions about the very early divergence of the Ceratophyllum clade compared with its position as sister to eudicots in many cladistic analyses. Lower Cretaceous aquatic angiosperms, such as Archaefructus and Montsechia, open the possibility that aquatic plants were locally common at a very early stage of angiosperm evolution and that aquatic habitats may have played a major role in the diversification of some early angiosperm lineages. © 2015, National Academy of Sciences. All rights reserved.
Vannier J.,CNRS Geological Laboratory of Lyon: earth, planets and environment |
Liu J.,Northwest University, China |
Lerosey-Aubril R.,CNRS Geological Laboratory of Lyon: earth, planets and environment |
Vinther J.,University of Bristol |
Daley A.C.,University of Oxford
Nature Communications | Year: 2014
Understanding the way in which animals diversified and radiated during their early evolutionary history remains one of the most captivating of scientific challenges. Integral to this is the 'Cambrian explosion', which records the rapid emergence of most animal phyla, and for which the triggering and accelerating factors, whether environmental or biological, are still unclear. Here we describe exceptionally well-preserved complex digestive organs in early arthropods from the early Cambrian of China and Greenland with functional similarities to certain modern crustaceans and trace these structures through the early evolutionary lineage of fossil arthropods. These digestive structures are assumed to have allowed for more efficient digestion and metabolism, promoting carnivory and macrophagy in early arthropods via predation or scavenging. This key innovation may have been of critical importance in the radiation and ecological success of Arthropoda, which has been the most diverse and abundant invertebrate phylum since the Cambrian. © 2014 Macmillan Publishers Limited.
Buffetaut E.,CNRS ENS Geology Laboratory |
Angst D.,CNRS Geological Laboratory of Lyon: earth, planets and environment
Geological Magazine | Year: 2013
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.
Legg D.A.,Imperial College London |
Legg D.A.,Natural History Museum in London |
Vannier J.,CNRS Geological Laboratory of Lyon: earth, planets and environment
Lethaia | Year: 2013
Isoxys is a cosmopolitan bivalved arthropod genus known almost exclusively from Cambrian Konservat-Lagerstätten. Despite its wide geographical distribution in such sites of exceptional preservation, little was known of its soft-part anatomy until recently when remains of eyes and raptorial frontal appendages were discovered. This absence has precluded determination of affinities. The new discovery of soft parts led to two important hypotheses: (1) that Isoxys was related to the 'great-appendage' arthropods and (2) that its contained species were not congeneric. Neither has been tested using a detailed cladistics analysis. The morphology of Isoxys is re-evaluated and coded into an extensive cladistics analysis. Our results indicate that Isoxys was indeed a monophyletic genus with all representatives united by the presence of an expansive dorsal shield with prominent antero- and posterolateral cardinal spines. It also indicates that Isoxys occupies a crucial role in arthropod evolution, resolving at the base of Arthropoda. The 'great appendages' of Isoxys are interpreted as innovating from either the protocerebral or deutocerebral somite and are therefore not homologous to those of other 'great-appendage' arthropods, which are interpreted as originating from the tritocerebral somite of the head. © 2013 The Lethaia Foundation.
Bonaventura P.,University of Lyon |
Benedetti G.,University of Lyon |
Albarede F.,CNRS Geological Laboratory of Lyon: earth, planets and environment |
Miossec P.,University of Lyon
Autoimmunity Reviews | Year: 2015
Zinc (Zn) nutritional importance has been known for a long time, but in the last decades its importance in immune modulation has arisen. This review aims at describing the mechanisms involved in the regulation of Zn homeostasis and their effects on the immune response focusing on those which are implicated in the physiopathology of rheumatoid arthritis. Zn functions as a modulator of the immune response through its availability, which is tightly regulated by several transporters and regulators. When this mechanism is disturbed, Zn availability is reduced, altering survival, proliferation and differentiation of the cells of different organs and systems and, in particular, cells of the immune system. Zn deficiency affects cells involved in both innate and adaptive immunity at the survival, proliferation and maturation levels. These cells include monocytes, polymorphonuclear-, natural killer-, T-, and B-cells. T cell functions and the balance between the different T helper cell subsets are particularly susceptible to changes in Zn status. While acute Zn deficiency causes a decrease in innate and adaptive immunity, chronic deficiency increases inflammation. During chronic deficiency, the production of pro-inflammatory cytokines increases, influencing the outcome of a large number of inflammatory diseases, including rheumatoid arthritis. © 2014 Elsevier B.V.
Reolid M.,University Jae n |
Emanuela M.,CNRS Geological Laboratory of Lyon: earth, planets and environment |
Nieto L.M.,University Jae n
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2014
The analysis of macroinvertebrates, trace fossils, calcareous nannofossils and geochemistry from Pliensbachian to Lower Toarcian deposits of the Subbetic (Southern Spain) allows us to interpret the incidence of the Toarcian Oceanic Anoxic Event (T-OAE) in the boundary between the Tethys and the Hispanic Corridor. Trace fossils from the marl-limestone rhythmite (Upper Pliensbachian to Lower Toarcian) indicate an oxygenated bottom. A dark marly interval occurs above a fossil-rich condensed surface with a negative excursion of δ18O, interpreted as evidence of the Early Toarcian transgression and a climate warming. The carbon cycle perturbation is recorded by decreasing CaCO3 content and the negative excursion of δ13C at the base of the Serpentinum Zone, NJT 6 nannofossil Zone. The barren interval for nektonic and benthic organisms at the beginning of the Serpentinum Zone confirms the oxygen restricted conditions in the sea-floor. Environmental conditions were unfavourable for the development of calcareous nannoplankton, as attested by the drop in absolute abundances. The deep photic zone seemed to be particularly hostile to phytoplankton, as shown by the decrease in relative abundance of the deep-dweller Mitrolithus jansae, related to shoaling of the oxygen minimum zone in the water column. Increasing values of redox sensitive elements and total organic carbon, as well as the record of pyrite framboids <5μm size, confirm the anoxic conditions (probably euxinic conditions in any moment) at the base of the dark marly interval (NJT 6). The return to oxic or dysoxic conditions is confirmed by the record of fossil-poor marls with scarce macroinvertebrates and microfossils, as well as the recovery of trace fossils mainly (low-oxygen tolerant Chondrites tracemakers). Increasing abundance of calcareous nannofossils and deep-dweller M. jansae indicate ameliorated environmental conditions in the water column. Geochemistry supports the recovery of carbonate production (increasing CaCO3) and oxygen availability (decrease of TOC and redox sensitive elements). © 2014 Elsevier B.V.
Mourer-Chauvire C.,CNRS Geological Laboratory of Lyon: earth, planets and environment
Neues Jahrbuch fur Geologie und Palaontologie - Abhandlungen | Year: 2013
The genus Dynamopterus Milne-edwards, 1892, described from the "Phosphorites du Quercy", is only known from humeri, whereas the genus Idiornis OberhOlser, 1899, is known in the Quercy from numerous elements of the post-cranial skeleton, but its humeri are known only from three fragments referred to the species I. itardiensis. Comparison of the humeri of Dynamopterus with those of Idiornis itardiensis, and with the recent genus Cariama, makes it possible to identify these humeri as belonging to the same genus as the remains attributed to Idiornis. The generic name Dynamopterus Milne-edwards, 1892, has priority over Idiornis OberhOlser, 1899, and therefore must replace it. © 2013 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.
Michaut C.,University Paris Diderot |
Ricard Y.,CNRS Geological Laboratory of Lyon: earth, planets and environment |
Bercovici D.,Yale University |
Sparks R.S.J.,University of Bristol
Nature Geoscience | Year: 2013
Eruptions at active silicic volcanoes are often cyclical. For example, at the Soufrière Hills volcano in Montserrat, Mount Pinatubo in the Philippines, and Sakurajima in Japan, episodes of intense activity alternate with repose intervals over periods between several hours and a day. Abrupt changes in eruption rates have been explained with the motion of a plug of magma that alternatively sticks or slides along the wall of the volcanic conduit. However, it is unclear how the static friction that prevents the plug from sliding is periodically overcome. Here we use two-phase flow equations to model a gas-rich, viscous magma ascending through a volcanic conduit. Our analyses indicate that magma compaction yields ascending waves comprised of low- and high-porosity bands. However, magma ascent to lower pressures also causes gas expansion. We find that the competition between magma compaction and gas expansion naturally selects pressurized gas waves with specific periods. At the surface, these waves can induce cyclical eruptive behaviour with periods between 1 and 100 hours, which compares well to the observations from Soufrière Hills, Mount Pinatubo and Sakurajima. We find that the period is insensitive to volcano structure, but increases weakly with magma viscosity. We conclude that observations of a shift to a longer eruption cycle imply an increase in magma viscosity and thereby enhanced volcanic hazard. © 2013 Macmillan Publishers Limited.
Andreani M.,CNRS Geological Laboratory of Lyon: earth, planets and environment |
Daniel I.,CNRS Geological Laboratory of Lyon: earth, planets and environment |
Pollet-Villard M.,CNRS Geological Laboratory of Lyon: earth, planets and environment
American Mineralogist | Year: 2013
The reactivity of ultramafic rocks under hydrothermal conditions controls chemical fluxes at the interface between the internal and external reservoirs of silicate planets. On Earth, hydration of ultramafic rocks is ubiquitous and operates from deep subduction zones to shallow lithospheric environments where it considerably affects the physical and chemical properties of rocks and can interact with the biosphere. This process also has key emerging societal implications, such as the production of hydrogen as a source of carbon-free energy. To date, the chemical model systems used to reproduce olivine hydrothermal alteration lead to the formation of serpentine with sluggish reaction rates. Here, we use in situ diamond-anvil cell experiments and show that the presence of aluminum in hydrothermal fluids increases the rate of olivine serpentinization by one to two orders of magnitude. Aluminum increases the solubility of olivine and enhances the precipitation of aluminous serpentine. After two days, olivine crystals were fully transformed to aluminous serpentine under conditions typical for natural hydrothermal environments, i.e., 200 and 300 °C, 200 MPa. This result motivates a re-evaluation of the natural rates of olivine serpentinization and of olivine hydrolysis in general in a wide range of settings. This discovery also opens the potential of the serpentinization reaction for industrial scale production of hydrogen at economically feasible timescales and temperature.