Distribution of the organic matter in the channel-levees systems of the Congo mud-rich deep-sea fan (West Africa). Implication for deep offshore petroleum source rocks and global carbon cycle     

François Baudin  Jean-Robert Disnar  Philippe Martinez  Bernard Dennielou 《Marine and Petroleum Geology》2010

The quantity and the source of organic matter preserved in the Recent turbiditic channel-levees systems around 4000 m-depth off the Congo River were determined using bulk geochemical approaches (Rock-Eval, elemental and isotopic analyses) as well as molecular and optical analyses on selected samples. These mud-rich sediments contain high amount of organic matter (3% Corg on average), the origin of which is a mixture of terrestrial higher-plant debris and deeply oxidized phytoplanktonic material. Although the relative contribution of continental source versus marine source of the organic matter cannot be precisely quantified, the continental fraction appears significant (at least 70–80%) especially for such depths and distances from the coast. The organic matter distribution appears very homogeneous at different scales, from the single turbiditic event to the entire levee, and changes in accumulation rates have a little impact on the quantity and quality of preserved organic matter.  相似文献   

Numerical analysis of frost effects in porous media. Benefits and limits of the finite element poroelasticity formulation     

Stéphane Multon  Alain Sellier  Bernard Perrin 《国际地质力学数值与分析法杂志》2012,36(4):438-458

The aim of this paper is to analyse the performance of a finite element formulation usable for predicting the mechanical consequences of frost effects on porous media. It considers the characteristics of porous media and how the frost action can be assessed. The problem is then separated into two parts: thermal and poromechanical calculations. The constitutive equations developed in the framework of poromechanics are presented and the implementation in a usual finite element poroelasticity formulation based on Zuber's method is adopted. An analysis of the time‐step influence on the convergence rate is given and leads us to propose a simple method in order to obtain objectivity of the finite element response and avoid over‐long calculations. Frost effect simulations are carried out on real porous media (two fired clays) as a case study. Although the experimental behaviour of the porous media subjected to frost action is in accordance with some observations, the calculated strains appear to be overestimated compared with measurements. The problem could be largely attributable to the difficulty of assessing permeability evolution during frost development. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Disaster risk reduction legislations: Is there a move from events to processes?     

Siambabala Bernard Manyena  Emmanuel Mavhura  Chipo Muzenda  Elias Mabaso 《Global Environmental Change》2013,23(6):1786-1794

Disaster research and scholarship is now advocating a shift from focusing on the hazard event to processes that generate vulnerability and loss of resilience to disasters. Disaster legislations are among prominent instruments that can highlight the tensions as well as challenges that are being encountered towards this change in focus. Using textual analysis, this paper presents a study that investigated whether five post-2002 disaster legislations have shifted emphasis from the hazard to the vulnerability and resilience paradigms. The five examples illustrate that while there is a slight change, at least in rhetoric, from response to a prevention focus, disaster legislations largely promote a centralised institutional framework, with inadequate resource commitments and limited participation from vulnerable communities. Consequently, while generalisations simply cannot be made without a wider analysis of many more examples from different countries, the five disaster legislations appear to re-emphasise the response focus with less attention on the processes that reduce vulnerability and enhance resilience. The conclusion is that while the rhetoric has changed, the disaster legislations have not significantly moved from the hazard to vulnerability and resilience focus suggesting that reduction of losses and damages to disasters remains a big challenge  相似文献   

Palaeo-environmental and dietary analysis of intestinal contents of a mammoth calf (Yamal Peninsula,northwest Siberia)     

Bas van Geel  Daniel C. Fisher  Adam N. Rountrey  Jan van Arkel  Joost F. Duivenvoorden  Aline M. Nieman  Guido B.A. van Reenen  Alexei N. Tikhonov  Bernard Buigues  Barbara Gravendeel 《Quaternary Science Reviews》2011,30(27-28):3935-3946

Intestinal samples from the one-month-old Siberian mammoth calf ‘Lyuba’ were studied using light microscopy and ancient DNA to reconstruct its palaeo-environment and diet. The palynological record indicates a ‘mammoth steppe’. At least some pollen of arboreal taxa was reworked, and thus the presence of trees on the landscape is uncertain. In addition to visual comparison of 11 microfossil spectra, a PCA analysis contributed to diet reconstruction. This yielded two clusters: one of samples from the small intestine and the other of large-intestine samples, indicating compositional differences in food remains along the intestinal tract, possibly reflecting different episodes of ingestion. Based on observed morphological damage we conclude that the cyperaceous plant remains and some remains of dwarf willows were originally eaten by a mature mammoth, most likely Lyuba’s mother. The mammoth calf probably unintentionally swallowed well-preserved mosses and mineral particles while eating fecal material deposited on a soil surface covered with mosses. Coprophagy may have been a common habit for mammoths, and we therefore propose that fecal material should not be used to infer season of death of mammoths. DNA sequences of trnL and rbcL genes amplified from ancient DNA extracted from intestinal samples confirmed and supplemented plant identifications based on microfossils and macro-remains. Results from different extraction methods and barcoding markers complemented each other and show the value of longer protocols in addition to fast and commercially available extraction kits.  相似文献   

A non‐collisional,accretionary Sveconorwegian orogen – Comment     

Charlotte Möller  Bernard Bingen  Jenny Andersson  Michael B. Stephens  Giulio Viola  Anders Scherstén 《地学学报》2013,25(2):165-168

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Meeting reports     

T. S. Murty  E. N. Bernard  Gordon A. McKay 《Natural Hazards》1988,1(3):305-308

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The ‘MESOGERS 84’ experiment: A report     

A. Weill  C. Mazaudier  F. Baudin  C. Klapisz  F. Leca  M. Masmoudi  D. Vidal Madjar  R. Bernard  O. Taconet  B. S. Gera  A. Sauvaget  A. Druilhet  P. Durand  J. Y. Caneil  P. Mery  G. Dubosclard  A. C. M. Beljaars  W. A. A. Monna  J. G. Van Der Vliet  M. Crochet  D. Thomson  T. Carlson 《Boundary-Layer Meteorology》1988,42(3):251-264

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The partitioning of Fe and Mg between olivine and carbonate and the stability of carbonate under mantle conditions   总被引：4，自引：1，他引：4  

John A. Dalton  Bernard J. Wood 《Contributions to Mineralogy and Petrology》1993,114(4):501-509

We have investigated the effect of Fe on the stabilities of carbonate (carb) in lherzolite assemblages by determining the partitioning of Fe and Mg between silicate (olivine; ol) and carbonates (magnesite, dolomite, magnesian calcite) at high pressures and temperatures. Fe enters olivine preferentially relative to magnesite and ordered dolomite, but Fe and Mg partition almost equally between disordered calcic carbonate and olivine. Measurement of K _d (X _Fe ^carb X _Mg ^ol /X _Fe ^ol X _Mg ^carb ) as a function of Fe/ Mg ratio indicates that Fe–Mg carbonates deviate only slightly from ideality. Using the regular solution parameter for olivine W _FeMg ^ol of 3.7±0.8 kJ/mol (Wiser and Wood 1991) we obtain for (FeMg)CO₃ a W _FeMg ^carb of 3.05±1.50 kJ/mol. The effect of Ca–Mg–Fe disordering is to raise K _d substantially enabling us to calculate W _CaMg ^carb -W _CaFe ^carb of 5.3±2.2 kJ/mol. The activity-composition relationships and partitioning data have been used to calculate the effect of Fe/Mg ratio on mantle decarbonation and exchange reactions. We find that carbonate (dolomite and magnesian calcite) is stable to slightly lower pressures (by 1 kbar) in mantle lherzolitic assemblages than in the CaO–MgO–SiO₂(CMS)–CO₂ system. The high pressure breakdown of dolomite + orthopyroxene to magnesite + clinopyroxene is displaced to higher pressures (by 2 kbar) in natural compositions relative to CMS. CO₂. We also find a stability field of magnesian calcite in lherzolite at 15–25 kbar and 750–1000°C.  相似文献   

The “geo” of United States national strategy     

Bernie Grover  M. Baruch Bernard 《GeoJournal》1993,31(2):141-148

The paper discusses the geo dimensions of the new world order, with particular emphasis on the increasing role of geoeconomics, and its impact on US national strategy. While the paper uses the US experience to illustrate the growing importance of geoeconomic considerations, the issues raised have direct bearing on many other nations throughout the world.US post Cold War strategy is determined by its three geo challenges. The most important is the geoeconomic challenge caused by the tri-polar division of the world along trading bloc lines, instant global communication and other technologies overcoming the constraints of physical geography, transnational corporations (TNCS) that are becoming supranational in character, and the emergence of a well educated global labor force. The geopolitical challenge is characterized by America's declining relative economic power and its traditional military allies having become economic competitors, while religious, ethnic, and regional tensions threaten its global interests. The third challenge is the military geography issue of effectively projecting power over distance, within the constraints of greatly reduced budgets and loss of overseas bases.  相似文献   

Application of objective analysis to metallic traces in the atmospheric aerosol     

Christophe Migon  Bernard Gentili 《Journal of Atmospheric Chemistry》1993,16(3):277-284

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