inscription
PORTAIL D'INFORMATION GÉOGRAPHIQUE

Résultats de la recherche (30 résultats)

Affinez votre recherche

Par Collection Par Auteur Par Date Par Sujet Par Titre
  • Isotopic approach to soil carbonate dynamics and implications for paleoclimatic interpretations
  • Carbon ; Carbonate ; Geochemistry ; Holocene ; Isotope analysis ; Nevada ; Oxygen 18 ; Palaeoclimatology ; Semi-arid area ; Soil ; United States
  • The AA. examine stable and radiogenic isotopes of C and stable isotopes of O in carbonate sampled from gravel coatings and soil matrix in three Holocene soils from a semiarid region in Nevada. By comparing isotopic measurements with modeled stable
  • isotope profiles and radiocarbon ages, the AA. assess the nature of soil carbonate with respect to its origin (detrital, dust, or pedogenic) and dynamic nature (closed or open to atmospheric CO2) over time.
  • 1994
  • Stable isotopic evidence for latest Pleistocene and Holocene climatic change in north-central Texas
  • Carbonate ; Climatic variation ; Geochronology ; Isotope analysis ; Lacustrine sediment ; Palaeo-environment ; Pedogenesis ; Quaternary ; Sedimentology ; Texas ; United States
  • The AA. examine evidence for climatic change at the Aubrey Clovis site, north-central Texas, over the past 14,000 yr. The primary emphasis of this paper will be on stable isotopic evidence from pedogenic and lacustrine carbonates from the study site
  • . An indepedently derived alluvial history from the same locality corroborate the isotopic data.
  • 1994
  • Isotope hydrograph separations and rapid delivery of pre-event water from drainage basins
  • Deuterium ; Hydrochemistry ; Hydrology ; Isotope analysis ; Meltwater ; Methodology ; Oxygen 18 ; Rill wash ; Stream flow ; Watershed
  • Environmental isotopes, such as oxygen-18 and deuterium, have been used increasingly to separate stormflow into its event and pre-event components in order to elucidate the sources, pathways and residence times of water in drainage basins
  • . The hydrological processes that have been invoked to explain the observed isotopic response of streamflow to rainfall and snowmelt inputs in various environments are reviewed. This paper summarizes the environmental isotope hydrograph separation technique
  • and provides a broad review of the results of isotope hydrograph separations conducted around the world.
  • 1994
  • Strontium isotopes as indicators of mineral weathering in catchments
  • out in the use of strontium isotopes in mineral weathering studies.
  • 1994
  • Evolution of isotopic composition and concentration of atmospheric CO2 as result of anthropogenic influences
  • Atmosphere ; Carbon dioxide ; Cracow ; Geochemistry ; Human impact ; Isotope analysis ; Poland ; Pollution ; Town
  • Systematic investigations of the isotopic composition in atmospheric CO2 and its concentration in Cracow urban area have been carried on. Continuous sampling at biweekly intervals was supplemented by series of samples representing four-hour periods
  • 1994
  • Stable isotopic variability within modern travertines
  • Carbon ; Carbonate rock ; Geochemistry ; Isotope analysis ; Oxygen 18 ; Palaeo-environment ; Travertine ; United States of America ; Water
  • Six ensembles de travertins de sources chaudes et deux ensembles à température ambiante ont été échantillonnés afin de déterminer les liens entre la teneur en isotopes stables des travertins et celle des eaux dans lesquels ils ont été déposés. Cette
  • 1994
  • Late Quaternary vegetation and climate changes in central Texas based on the isotopic composition of organic carbon
  • Biomass ; Carbon ; Climatic variation ; Isotope analysis ; Palaeo-ecology ; Palaeo-environment ; Quaternary ; Texas ; United States ; Vegetation
  • Stable carbon isotope analyses were performed on organic carbon from the late Quaternary alluvial deposits and soils along three streams within the Fort Hood Military Reservation of central Texas. This paper presents the results
  • 1994
  • New Zealand tephro-chronology as a tool in geomorphic history of the c. 140 ka Mamaku Ignimbrite Plateau and in relating oxygen isotope stages
  • Climatic variation ; Isotope analysis ; Loess ; New Zealand ; North Island ; Oxygen ; Palaeosol ; Stratigraphic correlation ; Stratigraphy ; Tephrochronology ; Vegetation ; Volcanism
  • 1994
  • Biomass ; Burundi ; Carbon ; Climatic variation ; Holocene ; Humid environment ; Isotope analysis ; Palaeo-environment ; Palynology ; Peat bog ; Quaternary
  • This study concerns the carbon isotope variations in organic matter from the Kashiru peat deposits, which span at least the last 40,000 yr. The δ13C values of total organic matter (TOM) were determined in order to estimate the relative abundances
  • of C3 and C4 plants in and around the swamp. The isotopic results are compared with the pollen data which have yielded a detailed record of vegetational and climatic changes in the Burundi mountains.
  • 1994
  • Aeolian features ; Isotope dating ; Kansas ; Loess ; Mineralogy ; Palaeo-environment ; Pedogenesis ; Stratigraphy ; Surface deposits ; United States
  • The AA. present here the stratigraphical, chemical, physical and mineralogical records from the loess deposits of central Kansas. The records show a strong correlation with the Louchuan record and the oxygen isotope curve, indicating continuous
  • 1994
  • Climatic variation ; Core sampling ; Ecuador ; Isotope analysis ; Marine sediment ; Oxygen ; Palaeogeography ; Pollen analysis ; Tropical zone
  • The general correspondence between pollen and oxygen isotope variations in Tri 163-31B suggests that tropical climatic variations in the northern Andes were basically coherent with northern hemisphere glacier variations.
  • 1994
  • Aminostratigraphy ; Bibliography ; C 14 dating ; Dating ; Isotope analysis ; Methodology ; Palaeomagnetism ; Thermoluminescence
  • 1994
  • Aerosol ; Atmospheric circulation ; Climatic variability ; Geochemistry ; Greenland ; Ice core ; Iceland ; Isotope analysis ; Volcanic ash ; Volcanic eruption
  • By using major ion, microparticle, and stable-isotope data obtained from ice cores, it is possible to assess the degree of atmospheric loading and potential climatic importance of major volcanic eruptions that occured prior to 1880. The AA. have
  • 1994
  • Baja California ; California ; Coral reef ; Geochemistry ; Isotope analysis ; Marine quaternary ; Marine terrace ; Mexico ; North Pacific Ocean ; Oregon ; Sea level ; United States of America ; Uranium
  • Corals from marine terrace deposits of the Pacific coast of North America show some open-system effects with respect to U isotopes. Secondary addition of 234U is observed and implies that some apparent ages are probably minima. Some variability
  • 1994
  • Atmosphere ; Cracow ; Isotope analysis ; Poland ; Pollution ; Precipitation ; Radioactivity ; Town ; Tritium
  • 1994
  • Eemian ; Greenland ; Ice ; Ice core ; Interglacial ; Isotope analysis ; Palaeoclimatology ; Quaternary
  • 1994
  • Isotope stratigraphy, sedimentation rates, deep circulation, and carbonate events in the Labrador Sea during the last 200 ka
  • Atlantic Ocean ; C 14 dating ; Carbonate ; Glaciation ; Isotope analysis ; North Atlantic Ocean ; Ocean circulation ; Oceanology ; Palaeo-environment ; Quaternary ; Sedimentology
  • 1994
  • Early diagenetic processes in Labrador Sea sediments: uranium-isotope geochemistry
  • Atlantic Ocean ; Diagenesis ; Geochemistry ; Isotope analysis ; Marine sediment ; North Atlantic Ocean ; Palaeo-environment ; Sea floor ; Uranium
  • 1994
  • Climatic variation ; Europe ; Foraminifera ; Interglacial ; Isotope analysis ; Marine quaternary ; Northwestern Europe ; Palaeo-environment ; Sea level ; Stratigraphy ; Water temperature
  • 1994
  • The earlier estimate for the age of laminated sediment formation, late Pleistocene to Holocene, was based on extrapolation of diatom data in the cores witn conventional 14C and oxygen-isotope chronologies. However,new radiocaebon ages for cores show
  • 1994