Managing and researching floods: sustainability,policy responses and the place of rural communities          下载免费PDF全文

Steven B. Emery  David M. Hannah 《水文研究》2014,28(18):4984-4988

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Cold-seep-driven carbonate deposits at the Central American forearc: contrasting evolution and timing in escarpment and mound settings   总被引：1，自引：0，他引：1  

V. Liebetrau  N. Augustin  S. Kutterolf  M. Schmidt  A. Eisenhauer  D. Garbe-Schönberg  W. Weinrebe 《International Journal of Earth Sciences》2014,103(7):1845-1872

Continuous surface cores of cold-seep carbonates were recovered offshore Pacific Nicaragua and Costa Rica from 800 to 1,500-m water depths (Meteor 66/3) in order to decipher their evolution and methane enriched fluid emanation in contrasting geological settings. Cores from the mounds Iguana, Perezoso, Baula V and from the Jaco Scarp escarpment were used for a multi-method approach. For both settings aragonite was revealed as dominant authigenic carbonate phase in vein fillings and matrix cementation, followed by Mg-calcite as second most abundant. This common precipitation process of CaCO₃ polymorphs could be ascribed as indirectly driven by chemical changes of the advecting pore water due to anaerobic oxidation of methane. A more direct influence of seep-related microbial activity on the authigenic mineral assemblage in both settings is probably reflected by the observed minor amounts of dolomite and a dolomite-like CaMg carbonate (MgCO₃ ~ 42 %). δ¹³C data of Jaco Scarp samples are significantly lower (?43 to ?56 ‰ PDB) than for mound samples (?22 to ?36 ‰ PDB), indicating differences in fluid composition and origin. Noteworthy, δ¹⁸O values of Scarp samples correlate most closely with the ocean signature at their time of formation. Documenting the archive potential, a high resolution case study of a mound core implies at least 40 changes in fluid supply within a time interval of approximately 14 ky. As most striking difference, the age data indicate a late-stage downward-progressing cementation front for all three mound cap structures (approx. 2–5 cm/ky), but a significantly faster upward carbonate buildup in the bulging sediments on top of the scarp environment (approx. 120 cm/ky). The latter data set leads to the hypothesis of chemoherm carbonate emplacement in accord with reported sedimentation rates until decompression of the advective fluid system, probably caused by the Jaco Scarp landslide and dating this to approximately 13,000 years ago.  相似文献   

(Mis)adventures in Rumsfeld space     

Matthew G. Hannah 《GeoJournal》2010,75(4):397-406

Ewald’s recent genealogy of constructions of risk in Western societies argues that the 1980s saw an important paradigm shift to the “precautionary principle”. Critical scholars have taken up this idea as a lens through which to interpret the Bush administration’s ‘war on terror’. I argue that 11 September 2001 actually brought about qualitative changes to this paradigm. Bush’s pre-emptive doctrine is driven, and perhaps even more importantly, continually justified to the US population, by what might be called the “trans-precautionary principle”, a move from “decisionism” to “actionism”, and a new radicalization of the way fear is produced and managed. Donald Rumsfeld’s famous typology of different articulations of knowledge and ignorance offers an excellent analytical window onto the connections between ignorance, fear and geopolitical action in this new regime. In the latter part of the essay, his four modes of knowledge/ignorance are arrayed, for heuristic purposes, in an abstract spatial grid organized along dimensions of the specificity and possession of knowledge. This allows a ‘mapping’ of some of the Bush administration’s more controversial strategies in the ‘war on terror’, as a set of different pathways through Rumsfeld Space.  相似文献   

Grain size, areal thickness distribution and controls on sedimentation of the 1991 Mount Pinatubo tephra layer in the South China Sea     

Martin G. Wiesner  Andreas Wetzel  Sandra G. Catane  Eddie L. Listanco  Hannah T. Mirabueno 《Bulletin of Volcanology》2005,67(5):490-495

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Interhemispheric climate linkages,V. Markgraf (ed.). Publisher Academic Press,San Diego 2000 (454 pp) ISBN 0‐12‐472670‐4     

Michael Hannah 《第四纪科学杂志》2003,18(5):468-469

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Amino acid analyses of R and CK chondrites          下载免费PDF全文

Aaron S. Burton  Hannah McLain  Daniel P. Glavin  Jamie E. Elsila  Jemma Davidson  Kelly E. Miller  Alexander V. Andronikov  Dante Lauretta  Jason P. Dworkin 《Meteoritics & planetary science》2015,50(3):470-482

Exogenous delivery of amino acids and other organic molecules to planetary surfaces may have played an important role in the origins of life on Earth and other solar system bodies. Previous studies have revealed the presence of indigenous amino acids in a wide range of carbon‐rich meteorites, with the abundances and structural distributions differing significantly depending on parent body mineralogy and alteration conditions. Here we report on the amino acid abundances of seven type 3–6 CK chondrites and two Rumuruti (R) chondrites. Amino acid measurements were made on hot water extracts from these meteorites by ultrahigh‐performance liquid chromatography with fluorescence detection and time‐of‐flight mass spectrometry. Of the nine meteorites analyzed, four were depleted in amino acids, and one had experienced significant amino acid contamination by terrestrial biology. The remaining four, comprised of two R and two CK chondrites, contained low levels of amino acids that were predominantly the straight chain, amino‐terminal (n‐ω‐amino) acids β‐alanine, and γ‐amino‐n‐butyric acid. This amino acid distribution is similar to what we reported previously for thermally altered ureilites and CV and CO chondrites, and these n‐ω‐amino acids appear to be indigenous to the meteorites and not the result of terrestrial contamination. The amino acids may have been formed by Fischer–Tropsch‐type reactions, although this hypothesis needs further testing.  相似文献   

Techniques for assessing the climatic sensitivity of river flow regimes     

Donna Bower  David M. Hannah  Glenn R. McGregor 《水文研究》2004,18(13):2515-2543

Regimes are useful tools for characterizing the seasonal behaviour of river flow and other hydroclimatological variables over an annual cycle (hydrological year). This paper develops and tests: (i) a regime classification method to identify spatial and temporal patterns in intraannual hydroclimatological response; and (ii) a novel sensitivity index (SI) to assess river flow regimes' climatic sensitivity. The classification of regime shape (form) and magnitude considers the whole annual cycle rather than isolating a single month or season for analysis, which has been the common approach of previous studies. The classification method is particularly useful for identifying large‐scale patterns in regimes and their between‐year stability, thus providing a context for short‐term, small‐scale process‐based research. The SI provides a means of assessing the often‐complex linkages between climatic drivers and river flow, as it identifies the strength and direction of associations between classifications of climate and river flow regimes. The SI has the potential for application to other problems where relationships between nominal classifications require to be found. These techniques are evaluated by application to a test data set of river flow, air temperature and rainfall time‐series (1974–1999) for a sample of 35 UK river basins. The results support current knowledge about the hydroclimatology of the UK. Although this research does not seek to yield new, detailed physical process understanding, it provides perspective at large spatial and temporal scales upon climate and flow regime patterns and quantifies linkages. Having clearly demonstrated the regime classification and SI to be effective in an environment where the hydroclimatology is relatively well known, there appears to be much to gain from applying these techniques in parts of the world where patterns and associations between climate and hydrology are poorly understood. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Mixing of Hillslope, River, and Alluvial Ground Waters in Lowland Floodplains   总被引：1，自引：0，他引：1  

Amanda J. Claxton  Paul D. Bates  Hannah L. Cloke 《Ground water》2003,41(7):926-936

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High-temperature carbonate minerals in the Stillwater Complex, Montana, USA     

Hannah M. Aird  Alan E. Boudreau 《Contributions to Mineralogy and Petrology》2013,166(4):1143-1160

High-temperature carbonate minerals have been observed in association with sulfide minerals below the platiniferous Johns-Manville (J-M) reef of the Stillwater Complex in a stratigraphic section that has been previously shown to be characterized by unusually Cl-rich apatite. The carbonate assemblage consists of dolomite with exsolved calcite in contact with sulfide minerals: chalcopyrite and pyrrhotite in the Peridotite Zone; and pyrrhotite with pentlandite, pyrite and chalcopyrite in Gabbronorite Zone I of the Lower Banded Series. A reaction rim surrounds the carbonate–sulfide assemblages, showing an alteration of the host orthopyroxene to a more calcium-enriched, Fe-depleted pyroxene. The calcite–dolomite geothermometer yields a minimum formation temperature as high as 950 °C for the unmixed assemblages. Iron and manganese concentrations exceed the range seen in carbonatite and mantle xenolith carbonates and are distinctly different from the nearly pure end-member carbonates associated with greenschist-grade (and lower) assemblages (e.g., carbonate veins in serpentinite) that occur locally throughout the complex. The association of high-temperature carbonates with sulfides beneath the J-M reef supports the hydromagmatic theory which involves a late-stage chloride–carbonate fluid percolating upwards, dissolving PGE and sulfides and redepositing them at a higher stratigraphic level. Characterization of the processes which form strategically important metal deposits, such as the J-M reef of the Stillwater Complex and the analogous Merensky reef of the Bushveld Complex in South Africa, could potentially lead to better exploration models and, more broadly, a deeper understanding of the cooling and compositional evolution of large bodies of ultramafic and mafic magma and of carbonatites, on both a local and a regional scale.  相似文献   

Application of Re-Os Geochemistry to Sedimentary Basin: Stratigraphic Correlation, Oil - Source Correlation and Paleo-Environment Condition     

XU Guangping  Judith L. Hannah  Holly J. Stein  Svetoslav Georgiev 《《地质学报》英文版》2013,87(Z1):602-604

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