Search results for "Surface Processes"
showing 10 items of 1294 documents
Free-living amoebae in sediments from the Lascaux Cave in France
2013
The Lascaux Cave in France is an old karstic channel where the running waters are collected in a pool and pumped to the exterior. It is well-known that water bodies in the vicinity of humans are suspected to be reservoirs of amoebae and associated bacteria. In fact, the free-living amoebae Acanthamoeba astronyxis, Acanthamoeba castellanii, Acanthamoeba sp. and Hartmannella vermiformis were identified in the sediments of the cave using phylogenetic analyses and morphological traits. Lascaux Cave sediments and rock walls are wet due to a relative humidity near saturation and water condensation, and this environment and the presence of abundant bacterial communities constitute an ideal habitat…
Anza palaeoichnological site, Late Cretaceous, Morocco. Part III: Comparison between traditional and photogrammetric records
2020
11 pages; International audience; The present study evaluates a methodological workflow that could identify dinosaur tracks and trackways more comprehensively at outcrop scale. The approach described here is based both on 3D modelling by photogrammetry at different resolutions, and on suitably processed digital elevation models (DEMs). The ichnosite of Anza, Morocco, was chosen to demonstrate the efficiency of the proposed pipeline, because 323 dinosaur and pterosaur tracks discovered there have already been published. One subsector containing 89 tracks, identified in the two companion works that followed a traditional approach, was selected and divided into four subzones. By combining diff…
La résilience : un concept pour la gestion des risques
2007
Les systemes socio naturels possedent la capacite de resister aux aleas. Les catastrophes les perturbent, mais les font rarement disparaitre. Le concept de resilience, d’origine physique, qui illustre cette capacite s’est enrichi lors de son transfert dans differentes disciplines scientifiques. Certes, la resilience est difficile a mesurer. Mais sa connaissance permet d’adopter de nouvelles formes de gestion des risques naturels ou sociaux. Ces nouvelles formes de gestion sont tres differentes des approches technologiques qui ne sont pas toujours bien adaptees au milieu ou a la societe.
Le territoire comme un système complexe : un concept opératoire pour l'aménagement et la géographie
2006
International audience; Les territoires sont aujourd'hui sur le devant de la scène, pressés de fournir des solutions de développement socio-économique, ou une image cohérente des lieux qu'ils englobent. On assiste à une forte consommation du concept, tout est territoire ; et des concepts qui recouvrent d'autres réalités glissent imperceptiblement vers cette boîte noire qui représente tout et rien à la fois. Visitons le concept sous l'angle de la systémique afin de produire une définition opérationnelle qui permette de resituer le territoire vis-à-vis de l'espace géographique. Le territoire défini se trouve ainsi replacé au cœur de la complexité.
Cinq millénaires de métallurgie en montagne basque. Les apports d'une démarche intégrée alliant palynologie et géochimie isotopique du plomb
2001
Five thousand years of metallurgy in the basque mountains : the contributions of an integrated process mixing palynology and the isotopic chemistry of lead. An interdisciplinary research combining palyno- logy and lead isotopic geochemistry was performed in a peat bog of the Basque Country, in an area recognized as being an old metallurgical centre. These various analyses make it possible to reconstitute mining and metallurgical activities and to appreciate the impact on forest during last five millennia. Several phases are attested between late Neolithic and modern times (Middle Bronze age, Late Bronze age, Antiquity and finally modern time). Most of these phases are clearly related to for…
Analistas simbólicos, jerarquía urbana y atracción de talento en las ciudades mundiales españolas (2005-2019): un análisis a partir de la EPA
2021
Este trabajo utiliza los microdatos de la Encuesta de población activa del INE entre 2005 y 2019 para analizar el nivel de competencias de la población ocupada, los procesos de cualificación del mercado de trabajo de las ciudades mundiales españolas (Madrid, Barcelona, Valencia, Sevilla y Bilbao) y el papel que están teniendo las migraciones de profesionales y técnicos altamente cualificados como reflejo de su capacidad diferencial para atraer talento externo. Siguiendo el marco conceptual propuesto por Allen J. Scott de creciente polarización de los mercados de trabajo metropolitanos entre una clase de «analistas simbólicos» de alta cualificación y una «subclase de servicios», se considera…
Gulf of Maine shells reveal changes in seawater temperature seasonality during the Medieval Climate Anomaly and the Little Ice Age
2011
article i nfo In this study, we use subannually resolved oxygen isotope values of fossil (dead-collected) and modern (live- caught) bivalve shells (Arctica islandica L.) from the northwestern Atlantic (Gulf of Maine, USA) to reconstruct past seasonal changes in seawater temperature. Our results indicate decreased seasonal temperature amplitude of about 1.6 °C (or ∼21%) during Medieval times (ca. AD 1033-1062) compared to shells from the early Little Ice Age (ca. AD 1321-1391) and during the late 19th century (AD 1864-1886). Additionally, seasonal oxygen isotope data suggest that summers were cooler and winters were warmer in the Gulf of Maine during the 11th century compared to summers and …
Comparative sclerochronology of modern and mid-Pliocene (c. 3.5Ma) Aequipecten opercularis (Mollusca, Bivalvia): an insight into past and future clim…
2009
Records of environment contained within the accretionarily deposited tissues of fossil organisms afford a means of detailed reconstruction of past climates and hence of rigorous testing of numerical climate models. We identify the environmental factors controlling oxygen and carbon stable-isotopic composition, and microgrowth-increment size, in the shell of modern examples of the Queen Scallop, Aequipecten opercularis. This understanding is then applied in interpretation of data from mid-Pliocene A. opercularis from eastern England. On the basis of oxygen-isotope evidence we conclude that winter minimum seafloor temperature was similar to present values (typically 6–7 °C) in the adjacent so…
Coralline algal growth-increment widths archive North Atlantic climate variability
2011
Over the past decade coralline algae have increasingly been used as archives of paleoclimate information. Encrusting coralline algae, which deposit annual growth increments in a high Mg-calcite skeleton, are amongst the longest-lived shallow marine organisms. In fact, a live-collected plant has recently been shown to have lived for at least 850 years based on radiometric dating. While a number of investigations have successfully used geochemical information of coralline algal skeletons to reconstruct sea surface temperatures, less attention has been paid to employ growth increment widths as a temperature proxy. Here we explore the relationship between growth and environmental parameters in …
Eurhomalea exalbida (Bivalvia): A reliable recorder of climate in southern South America?
2012
Abstract Due to the lack of suitable high-resolution archives, regional and continental-scale climate dynamics of southern South America are not well understood. Shells of the long-lived, shallow-marine bivalve mollusk, Eurhomalea exalbida (Dillwyn), are likely to contain information on the past water temperatures. As yet, however, no rigorous calibration study has been presented so that growth history traits and the reliability of shell oxygen isotope-based temperature estimates remain unknown. Shell growth patterns and oxygen isotope ratios of four young specimens of E. exalbida from the Falkland Islands (Southwest Atlantic) were analyzed and cross-calibrated with environmental parameters…