L'analyse isotopique de 36 échantillons d'eau du sol est faite dans le cadre d'une étude hydrogéologique en Tripolitaine. La mesure des isotopes stables H/H, O/O et C/C et les isotopes radioactifs H/'H et C/C reflètent les mélanges verticaux et
This paper proposes, as a testable hypothesis, a basin-scale approach for interpreting the abundance of in situ produced cosmogenic isotopes, an approach which considers explicitly both the isotope and sediment flux through a drainage basin
. This model is designed for interpreting isotope abundance in sediment. The AA. suggest that measured isotope abundances may reflect spatially averaged rates of erosion if a basin is in isotopic steady state and if sampled sediments are well mixed.
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.
Monthly precipitation samples were collected at Tsukuba City from 1992 to 2006, and isotope ratios of oxygen and hydrogen were analyzed for all samples. The isotope ratios of monthly precipitation have no remarkable trend in their seasonal change
. The temperature effect on isotopes in precipitation is found durinf cool period. In cases of snowfall, precipitation from Baiu front and autumnal rain front, the isotope ratios in precipitation are relatively lighter than those of other cases.
The Greenland Ice Sheet Project 2 (GISP2) oxygen isotope record, with its high-resolution detail, yields crucial information on past climate change. Here the AA. present high-resolution GISP2 oxygen isotope records and mention some of their climatic
implications, with emphasis on the abrupt switches in isotope ratios in the Northern Hemisphere.
Isotope und ihre Anwendung in den Geowissenschaften, in der Bergbausicherheit und im Umweltschutz.. (Isotopes and their application in the geological sciences, the safety in mining and protection against environmental pollution)
Congrès ; Extraction minière ; Généralités sur la géographie ; Géochimie ; Isotope ; Lutte contre la pollution ; Mine ; Pollution ; Sciences de la Terre ; Sécurité
Geomorphological applications of cosmogenic isotope analysis
Bibliography ; Dating ; Erosion rate ; Geochemistry ; Geomorphology ; Isotope analysis ; Mass movement ; Weathering
The AA. focus on the geomorphological applications of in situ-produced cosmogenic isotope analysis. The past decade has seen a rapid growth in applications of cosmogenic isotope analysis to a wide range of geomorphological problems
Climate in southwestern Ontario, Canada, between AD 1610 and 1885 inferred from oxygen and hydrogen isotopic measurements of wood cellulose from trees in different hydrologic settings
Oxygen and hydrogen isotopes were measured in wood celullose and cellulose-nitrate from trees that grew in different hydrologic settings in southwestern Ontario. An isotope model that accounts for isotopic fractionations associated
with photosynthesis in plants was applied to the stable isotope data to infer past meteoric water isotopic composition and seasonal air moisture variations. The result is an account of summer and winter conditions in southwestern Ontario for 275 yyears (1610 to 1885
Sr-isotope record of Quaternary marine terraces on the California coast and off Hawaii
California ; Etats-Unis ; Géochimie ; Hawaii ; Isotope ; Niveau marin ; Paléo-environnement ; Quaternaire marin ; Stratigraphie ; Terrasse marine
California ; Geochemistry ; Hawaii ; Isotope ; Marine quaternary ; Marine terrace ; Paleo-environment ; Sea level ; Stratigraphy ; United States
The AA. use Sr-isotope stratigraphy to constrain relative and absolute ages of Quaternary marine terraces formed during interglacial periods in southern California. They test for the presence of a glacial-interglacial oscillatory signal superimposed
on the longer-term Sr-isotope trend for the Quaternary.
Oxygen isotope constraints on surface ocean temperatures
Donnée substitutive ; Foraminifère ; Géographie physique ; Isotopes de l'oxygène ; Paléoclimatologie ; Quaternaire zone chaude ; Température de surface de l'océan
Published oxygen isotope results from benthic and planktonic foraminifera are used to constrain the extent to which surface ocean temperatures in the tropics changed between glacial and inter-glacial time. The possible impacts of bioturbation
and of the redistribution of oxygen isotopic ratios within the sea, putting aside the oxygen isotope results, are consistent with the CLIMAP project conclusion that tropical ocean temperatures remained within ca. 2oC of their present value.
Oxygen isotope studies and quaternary marine climates in Climatic variations and variability: facts and theories.
This paper describes the isotopic fractionations and shows that variations of the oxygen isotopic composition of foraminifera along deep sea cores are generally a continental ice volume index and thus a worldwide oceanic stratigraphic marker
. Specific applications of oxygen isotopes related either to past temperature changes or local sea water isotopic composition variations are presented.
Les isotopes du milieu (isotopes constitutifs de l'eau, isotopes dissous) peuvent être utilisés à des fins scientifiques et techniques en hydrologie: étude des crues, du rôle des neiges, du transfert de l'eau et des modalités de recharge dans la
Up to one fourth of the isotopic change in foraminifera found in deep-sea cores (or some 0.3 /) may be due to a gradual change in the isotopic composition of the Antarctic and Greenland ice sheets. Therefore the peak-to-valley variation of the 0
uncorrected isotopic curves, and the last stadial (e.g. Weichselian around 18,000 B.P.) less intense.
Oxygen isotope ratios from tree rings containing compression wood
During studies of oxygen isotope : temperature relationships for tree rings in the Canadian Rockies, the AA. noted differences in oxygen isotope ratios between samples from compression wood and normal radii in the same stem. This paper briefly
The purposes of this study are : 1) to investigate temporal and spatial distribution of environmental isotopes of natural waters at a mountainous catchment| 2) to make clear the factors causing isotopic variation of natural waters| 3) to understand
Groundwater isotopic evidence for paleorecharge in U.S. High Plains aquifers
Aquifer ; Deuterium ; Great Basin ; Groundwater ; Isotope analysis ; Oxygen 18 ; Palaeohydrology ; Tritium ; United States of America
This study interprets relative groundwater ages, distinguishes vertical and lateral flow paths, and evaluates paleoclimatic implications of isotopic stratification of groundwater beneath the U.S. High Plains.
Ross ice shelf oxygen isotopes and West Antarctic climate history
Antarctique ; Barrière de Ross ; Carotte de glace ; Glace ; Géographie des régions polaires ; Isotopes de l'oxygène ; Paléoclimatologie ; Quaternaire supérieur ; Ross Ice Shelf
The Ross Ice Shelf oxygen isotopic profile at station J-9 covers at least the last 30,000 yr.
This paper discusses the chemical evolution and the recharge elevation of spring water by using major dissolved components and isotopic composition around Asama volcano. In addition the A. will provide the conceptual model of groundwater flow system
The development of biogeography as a science has involved the assimilation of both new concepts and new techniques. Stable isotopes have been used in the study of climatic history, the evolution of the biosphere, the biogechemical cycling