Regional Seas and Sustainable Development Results of an International Workshop     

Josep Maria Bayona  Joan Albaigés 《GeoJournal》1995,36(4):416-416

Reports

Regional Seas and Sustainable Development Results of an International Workshop  相似文献   

On the connection among three classical mechanical problems via the hypercomplex KS-transformation     

Maria Dina Vivarelli 《Celestial Mechanics and Dynamical Astronomy》1990,50(2):109-124

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Search for nucleosynthetic and radiogenic tellurium isotope anomalies in carbonaceous chondrites     

Manuela A. Fehr  Mark Rehkämper  Alex N. Halliday  Maria Schönbächler  Bodo Hattendorf 《Geochimica et cosmochimica acta》2006,70(13):3436-3448

Tellurium isotope data acquired by multiple-collector inductively coupled plasma-mass spectrometry (MC-ICPMS) are presented for sequential acid leachates of the carbonaceous chondrites Orgueil, Murchison, and Allende. Tellurium isotopes are produced by a broad range of nucleosynthetic pathways and they are therefore of particular interest given the isotopic anomalies previously identified for other elements in these meteorites. In addition, the data provide new constraints on the initial solar system abundance of the r-process nuclide ¹²⁶Sn, which decays to ¹²⁶Te with a half-life of 234,500 years. The ¹²⁶Te/¹²⁸Te ratios of all leachates were found to be identical, within uncertainty, despite variations in ¹²⁴Sn/¹²⁸Te of between about 0.002 and 1.4. The data define a ¹²⁶Sn/¹²⁴Sn ratio of <7.7 × 10⁻⁵ at the time of last isotopic closure, consistent with the value of <18 × 10⁻⁵ previously reported for bulk carbonaceous chondrites. How close this is to the initial ¹²⁶Sn/¹²⁴Sn ratio of the solar system depends on when the investigated samples last experienced redistribution of Sn and Te. No clear evidence is found for nucleosynthetic anomalies in the abundances of p-, s-, and r-process nuclides. The largest effect detected in this study is a small excess of the r-process nuclide ¹³⁰Te in a nitric acid leachate of Murchison. This fraction displays an anomalous ε¹³⁰Te of +3.5 ± 2.5. Although barely resolvable given the analytical uncertainties, this is consistent with the presence of a small excess r-process component or an s-process deficit. The general absence of anomalies contrasts with previous results obtained for K, Cr, Zr, Mo, and Ba isotopes in similar leachates, which display nucleosynthetic anomalies of up to 3.8%. The reason for this discrepancy is unclear but it may reflect volatility and more efficient mixing of Te in the solar nebula.  相似文献   

Elucidation of different forms of organic carbon in marine sediments from the Atlantic coast of Spain using thermal analysis coupled to isotope ratio and quadrupole mass spectrometry     

Elisa Lopez Capel  Jos Maria de la Rosa Arranz  Francisco J. Gonzlez-Vila  Jos Antonio Gonzlez-Perez  David A.C. Manning 《Organic Geochemistry》2006,37(12):1983

Analysis of river, estuary and marine sediments from the Atlantic coast of Spain using thermogravimetry–differential scanning calorimetry–quadrupole mass spectrometry–isotope ratio mass spectrometry (TG–DSC–QMS–IRMS) was used to (a) distinguish bulk chemical hosts for C within a sediment and humic acid fraction, (b) track C pools with differing natural C isotope ratios and (c) observe variation with distance from the coast. This is the first application of such a novel method to the characterisation of organic matter from marine sediments and their corresponding humic acid fractions. Using thermal analysis, a labile, a recalcitrant and a refractory carbon pool can be distinguished. Extracted humic fractions are mainly of recalcitrant nature. The proportion of refractory carbon is greatest in marine sediments and humic acid fractions. Quadrupole mass spectrometry confirmed that the greatest proportion of m/z 44 (CO₂) and m/z 18 (H₂O) were detected at temperatures associated with recalcitrant carbon (510–540 °C). Isotope analysis detected progressive enrichment in δ¹³C for the sediment samples with an increase in marine influence. Isotopic heterogeneity in the refractory organic matter in marine sediments could be due to products of anthropogenic origin or natural combustion products. Isotope homogeneity of humic acids confirms the presence of terrigenous C in marine sediments, allowing the terrestrial input to be characterised.  相似文献   

Multiple magnetization events in the Red River carbonates, Williston Basin, Canada: Evidence for fluid-flow?     

Erika Szabo  Maria T. Cioppa   《Journal of Geochemical Exploration》2006,89(1-3):384

Samples collected from the Upper Ordovician Red River carbonates in a well at the centre of the Williston Basin revealed two paleomagnetic components with different inclinations, 60.3 ± 3.9° (k = 70.7, N = 12) and 20.4 ± 3.3° (k = 141.2, N = 8), but similar declination values in individual specimens. Inclination-only analysis indicates two possible scenarios for the age of these two magnetizations: in scenario (a) the timing of magnetization happened sometime between Late Ordovician to Devonian; and in scenario (b) there are two different remagnetizations, one that overlaps Pennsylvanian to Permian time while the other can have either a Late Jurassic or a Tertiary age. Whereas dolomitization and some isotopic data tend to support scenario (a), previous paleomagnetic data from the Williston Basin and from younger units in the same well, the tectonic evolution of the basin, and the hydrocarbon maturation pattern in the Red River carbonates all favour chemical remagnetization(s) driven by orogenic fluids during the Alleghenian and Laramide orogenies.  相似文献   

The bimodal rift-related Juscelândia volcanosedimentary sequence in central Brazil: Mesoproterozoic extension and Neoproterozoic metamorphism     

Renato Moraes  Reinhardt A. Fuck  Mrcio Martins Pimentel  Simone M.C.L. Gioia  Maria H.B.M. de Hollanda  Richard Armstrong 《Journal of South American Earth Sciences》2006,20(4):287-301

The Barro Alto Complex and Juscelândia volcanosedimentary sequence are exposed in the central part of the Neoproterozoic Brasília belt of central Brazil. The former is a large (approximately 150 km long), boomerang-shaped, mafic-ultramafic, layered complex formed by two different intrusions metamorphosed under granulite facies. These rocks are tectonically overlain by rocks of the Juscelândia volcanosedimentary sequence, represented mainly by biotite-gneiss and amphibolite, or amphibolite facies metamorphic equivalents of rhyolite and basalt, respectively. New SIMS U–Pb zircon data and Sm–Nd isochron data presented herein help clarify the igneous and metamorphic evolution of the Juscelândia volcanosedimentary sequence, as well as its relationship with the Barro Alto Complex. Zircon grains from two biotite gneisses were analyzed by SIMS (SHRIMP) and indicate Mesoproterozoic dates, approximately 1.28 Ga, interpreted as the time of bimodal volcanism in a tectonic setting transitional between a continental rift and an ocean basin. Metamorphism is constrained by Sm–Nd garnet-whole-rock isochrons for garnet amphibolite and pelitic schists of the Juscelândia sequence, as well as for clinopyroxene-garnet amphibolite and garnet granulite of the Barro Alto Complex, which give ages between 0.74 and 0.76 Ga, in agreement with SIMS dates for metamorphic zircon rims. These new data are significant, because they establish that a single metamorphic event affected both the Barro Alto Complex and the Juscelândia sequence. Based on these new data, we present a modified tectonic model for the Brasília belt.  相似文献   

Holocene climate variability in Sicily from a discontinuous stalagmite record and the Mesolithic to Neolithic transition   总被引：2，自引：0，他引：2  

Silvia Frisia  Andrea Borsato  Augusto Mangini  Christoph Sptl  Giuliana Madonia  Ugo Sauro 《Quaternary Research》2006,66(3):388-400

Fabric and stable isotopic composition of a Holocene stalagmite (CR1) from a cave in northern Sicily record changes in paleorainfall in the early Holocene. High δ¹³C stable isotope values in the calcite deposited from ca. 8500 to ca. 7500 yr ago are interpreted as reflecting periods of high rainfall. The wet phase was interrupted by two periods of multi-century duration characterized by relatively cool and dry winters centered at ca. 8200 and ca. 7500 yr ago, highlighted by low δ¹³C and δ¹⁸O values. A high variability of δ¹³C values is recorded from ca. 7500 to ca. 6500 yr ago and indicates that the transition from a pluvial early Holocene to the present-day climate conditions was punctuated by decadal-scale periods of relatively dry winters. In northern Sicily, the traditional elements of the Neolithic appear at ca. 7700 yr ago. It is possible that changes in rainfall influenced the passage from hunter-gathering to farming and sheep-herding economies.  相似文献   

Dicarinella imbricata (MORNOD 1949): First SEM documentation of the lost holotype and foraminiferal assemblage from the type horizon (Upper Cretaceous, Switzerland)     

Michele Caron  Silvia Spezzaferri 《Swiss Journal of Geoscience》2006,99(3):295-299

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Gravity signature of crustal subduction inferred from numerical modelling     

Anna Maria Marotta  Elisa Spelta  Catia Rizzetto 《Geophysical Journal International》2006,166(2):923-938

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Soluble organic compounds in fog and cloud droplets: what have we learned over the past few years?     

Sandro Fuzzi  Maria Cristina Facchini  Stefano Decesari  Emanuela Matta  Mihaiela Mircea 《Atmospheric Research》2002,64(1-4)

We have recently set up a new procedure for characterising the water soluble organic compounds (WSOC) in fog water, for which information is still rather limited. Fog samples collected during the 1998–1999 fall–winter season in the Po Valley (Italy) were analysed following this procedure, which allows a quantitative determination of three main classes of organic compounds (neutral species, mono- and di-carboxylic acids, polycarboxylic acids), together accounting for ca. 85% of the total WSOC. This procedure also provides information on the main chemical characteristics of these three classes of compounds (functional groups, aliphatic vs. aromatic character, etc.). The enhanced chemical knowledge on fog/cloud chemical composition opens new scenarios as far as chemical and microphysical processes in clouds and fogs are concerned.  相似文献