Age and significance of the Quaternary cemented deposits of the Duje Valley (Picos de Europa,Northern Spain)     

Elisa Villa  Heather Stoll  Pedro Farias  Luna Adrados  R. Lawrence Edwards  Hai Cheng 《Quaternary Research》2013,79(1):1-5

Cemented calcareous breccias appear in the Picos de Europa (Cantabrian Mountains, Spain) resting on glacially abraded surfaces and covered by moraines. U/Th dating of the calcite coating the clasts was successful in two samples, the oldest one indicating that the breccias accumulated during or prior to Marine Isotope Stage (MIS) 11, and the youngest indicating later cementation during MIS 8. The former introduces a limit for the age of the glaciation preceding the breccias, which cannot correspond to an event younger than MIS 12. This is the oldest absolute age so far obtained for intercalated glacial/interglacial deposits of the Iberian Peninsula.  相似文献   

Opaque minerals,magnetic properties,and paleomagnetism of the Tissint Martian meteorite     

Jérôme Gattacceca  Roger H. Hewins  Jean‐Pierre Lorand  Pierre Rochette  France Lagroix  Cécile Cournède  Minoru Uehara  Sylvain Pont  Violaine Sautter  Rosa. B. Scorzelli  Chrystel Hombourger  Pablo Munayco  Brigitte Zanda  Hasnaa Chennaoui  Ludovic Ferrière 《Meteoritics & planetary science》2013,48(10):1919-1936

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Chondrules: Precursors and interactions with the nebular gas     

Roger H. HEWINS  Brigitte ZANDA 《Meteoritics & planetary science》2012,47(7):1120-1138

Abstract– Chondrule compositions suggest either ferroan precursors and evaporation, or magnesian precursors and condensation. Type I chondrule precursors include granoblastic olivine aggregates (planetary or nebular) and fine‐grained (dustball) precursors. In carbonaceous chondrites, type I chondrule precursors were S‐free, while type II chondrules have higher Fe/Mn than in ordinary chondrites. Many type II chondrules contain diverse forsteritic relicts, consistent with polymict dustball precursors. The relationship between finer and coarser grained type I chondrules in ordinary chondrites suggests more evaporation from more highly melted chondrules. Fe metal in type I, and Na and S in type II chondrules indicate high partial pressures in ambient gas, as they are rapidly evaporated at canonical conditions. The occurrence of metal, sulfide, or low‐Ca pyroxene on chondrule rims suggests (re)condensation. In Semarkona type II chondrules, Na‐rich olivine cores, Na‐poor melt inclusions, and Na‐rich mesostases suggest evaporation followed by recondensation. Type II chondrules have correlated FeO and MnO, consistent with condensation onto forsteritic precursors, but with different ratios in carbonaceous chondrites and ordinary chondrites, indicating different redox history. The high partial pressures of lithophile elements require large dense clouds, either clumps in the protoplanetary disk, impact plumes, or bow shocks around protoplanets. In ordinary chondrites, clusters of type I and type II chondrules indicate high number densities and their similar oxygen isotopic compositions suggest recycling together. In carbonaceous chondrites, the much less abundant type II chondrules were probably added late to batches of type I chondrules from different O isotopic reservoirs.  相似文献   

New unspiked K–Ar ages of Quaternary sub-glacial and sub-aerial volcanic activity in Iceland     

Hervé Guillou  Brigitte Van Vliet-Lanoë  Agust Guðmundsson  Sébastien Nomade 《Quaternary Geochronology》2010,5(1):10-19

Indisputable geochronology of Icelandic volcanism may contribute to improving the use of volcanic proxies for paleoenvironmental studies. Accurate and reliable ages may also provide some useful constraints in studying the possible relationship between volcanism and deglaciation in Iceland. Given the difficulty of dating accurately young and low potassic volcanic samples from Iceland, the relationship between deglaciation and increasing levels of volcanism has been shown only for the last deglaciation. The purpose of this study is to evaluate the potential of the unspiked K–Ar dating method for dating Quaternary Icelandic volcanic rocks, because we consider that reliable K–Ar ages of interglacial and sub-glacial volcanic products may generate useful data sets for paleoclimatic reconstructions, so enabling the link between glaciation and volcanic activity to be better established. Given the ages and precisions obtained, this study demonstrates that the unspiked K–Ar method is a promising tool for reconstructing the recent volcanic activity in Iceland during glacial and interglacial intervals.  相似文献   

S velocity structure and radial anisotropy in the Aegean region from surface wave dispersion     

Brigitte Endrun  Thomas Meier  Sergei Lebedev  Marco Bohnhoff  George Stavrakakis  Hans-Peter Harjes 《Geophysical Journal International》2008,174(2):593-616

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Compounds, creativity and complexity in climate change communication: The case of ‘carbon indulgences’     

Brigitte Nerlich  Nelya Koteyko 《Global Environmental Change》2009,19(3):345-353

This article deals with climate change from a linguistic perspective. Climate change is an extremely complex issue that has exercised the minds of experts and policy makers with renewed urgency in recent years. It has prompted an explosion of writing in the media, on the internet and in the domain of popular science and literature, as well as a proliferation of new compounds around the word ‘carbon’ as a hub, such as ‘carbon indulgence’, a new compound that will be studied in this article. Through a linguistic analysis of lexical and discourse formations around such ‘carbon compounds’ we aim to contribute to a broader understanding of the meaning of climate change. Lexical carbon compounds are used here as indicators for observing how human symbolic cultures change and adapt in response to environmental threats and how symbolic innovation and transmission occurs.  相似文献   

Large-Eddy Simulation of the Stable Atmospheric Boundary Layer using Dynamic Models with Different Averaging Schemes   总被引：5，自引：5，他引：0  

Rob Stoll  Fernando Porté-Agel 《Boundary-Layer Meteorology》2008,126(1):1-28

Large-eddy simulation (LES) of a stable atmospheric boundary layer is performed using recently developed dynamic subgrid-scale (SGS) models. These models not only calculate the Smagorinsky coefficient and SGS Prandtl number dynamically based on the smallest resolved motions in the flow, they also allow for scale dependence of those coefficients. This dynamic calculation requires statistical averaging for numerical stability. Here, we evaluate three commonly used averaging schemes in stable atmospheric boundary-layer simulations: averaging over horizontal planes, over adjacent grid points, and following fluid particle trajectories. Particular attention is focused on assessing the effect of the different averaging methods on resolved flow statistics and SGS model coefficients. Our results indicate that averaging schemes that allow the coefficients to fluctuate locally give results that are in better agreement with boundary-layer similarity theory and previous LES studies. Even among models that are local, the averaging method is found to affect model coefficient probability density function distributions and turbulent spectra of the resolved velocity and temperature fields. Overall, averaging along fluid pathlines is found to produce the best combination of self consistent model coefficients, first- and second-order flow statistics and insensitivity to grid resolution.  相似文献   

‘Low carbon’ metals, markets and metaphors: the creation of economic expectations about climate change mitigation     

Brigitte Nerlich 《Climatic change》2012,110(1-2):31-51

Dealing with the threat of anthropogenic climate change has been a challenge for policy makers for a long time. In recent years, the problems posed by climate change and solutions proposed to mitigate its effects have been framed by lexical ‘carbon compounds’, such as carbon footprint or carbon trading and by one dominant metaphor, the market metaphor. Through a detailed content analysis of industry and press coverage from 1985 to the present, this paper examines the fate of one important lexical compound in this context, namely low carbon, which can be used as an adjective or a noun. Over the last two decades this lexical compound moved across and between three discourses, the steel industry, the car industry and what one might call the climate change industry. Using insights from ecolinguistics and the sociology of expectations, the paper discusses how the lexical compound low carbon in general and the metaphor low carbon future in particular came to prominence in policy discourses, especially in the UK, and how they were used to frame expectations of a prosperous low carbon future, while sidelining deeper social and cultural reflections on climate change mitigation.  相似文献   

Loess and palaeoenvironment: Some results of a European joint programme of research     

Edward Derbyshire  Armelle Billard  Brigitte Van Vliet-Lanoë  Jean-Pierre Lautridou  Mauro Cremaschi Cnr 《第四纪科学杂志》1988,3(2):147-169

In 1985, a programme of research on the sedimentology and diagenesis of the loess and loessic silts of western Europe was initiated jointly by laboratories in Leicester, Meudon, Caen, Milan, Cardiff and Southampton, involving a limited amount of comparative work on the loess from types sites in the Loess Plateau of central China. Preliminary results include the following: (1) Experimental procedures in particle size analysis, clay sample preparation and microscopy have been standardised in all cooperating groups; distinctive fabrics indicative of depositional mechanisms have been recognised. (2) Comparison of aeolian, colluvial and alluvial silt by laser-scanning and bulk magnetic susceptibility anisotropy methods appears to differentiate aeolian silt from loessic silts re-deposited by slope processes and flowing water. (3) The variability in the anisotropy of the limon à doublet facies has been assessed by image analysis of scanning electron microscopy (SEM) and optical microscopy. Strong anisotropy has also been measured in thin section imagery of loess from Normandy and Poland as the product of freezing and thawing. This is confirmed by scanning electron microscopy and by experimental freezing of some silts. (4) The clay fabric and mineralogy in western European loess differ from those in Chinese loess, especially in the case of semi-arid deposits. (5) Distribution of CaCO₃, using thin sections and SEM analysis, has been determined for loess from Normandy and the Rhǒne valley in France and for some Chinese loess, At Saint Vallier, zones of CaCO₃ concentration occur masking much of the original (loess) sedimentary skeleton which is a locally reworked loessic silt with some laminations. Despite considerable scatter, the palaeomagnetic results indicate a reversed polarity throughout, placing the whole Saint Vallier sequence in the Matuyama chron. These preliminary results suggest the existence of two different palaeoenvironments: one typified by central China, with arid glacials and humid interglacials; and the other represented by western Europe, with generally high humidities. There was stronger weathering and soil development and fewer freezing effects on the lossic succession in northern Italy than in western littoral Europe.  相似文献   

Book reviews     

Michael Sokolov  Brigitte Nixdorf  Mohammad A. Kishk  Mohammed A. Kishk  Wolf Tietze  W. Weischet  G. H. Pirie  Helmut Blume  Konrad Murr  H. Hubrich  Hans-Jürgen Brosin 《GeoJournal》1991,25(1):58-96

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