The impact of African aridity on the isotopic signature of Atlantic deep waters across the Middle Pleistocene Transition     

Bruno Malaizé  Elsa Jullien  Amandine Tisserand  Charlotte Skonieczny  E. Francis Grousset  Frédérique Eynaud  Catherine Kissel  Jérôme Bonnin  Svenja Karstens  Philippe Martinez  Aloys Bory  Vivianne Bout-Roumazeilles  Thibaut Caley  Xavier Crosta  Karine Charlier  Linda Rossignol  José-Abel Flores  Ralph Schneider 《Quaternary Research》2012,77(1):182-191

A high resolution analysis of benthic foraminifera as well as of aeolian terrigenous proxies extracted from a 37 m-long marine core located off the Mauritanian margin spanning the last ~ 1.2 Ma, documents the possible link between major continental environmental changes with a shift in the isotopic signature of deep waters around 1.0–0.9 Ma, within the so-called Mid-Pleistocene Transition (MPT) time period. The increase in the oxygen isotopic composition of deep waters, as seen through the benthic foraminifera δ¹⁸O values, is consistent with the growth of larger ice sheets known to have occurred during this transition. Deep-water mass δ¹³C changes, also estimated from benthic foraminifera, show a strong depletion for the same time interval. This drastic change in δ¹³C values is concomitant with a worldwide 0.3‰ decrease observed in the major deep oceanic waters for the MPT time period. The phase relationship between aeolian terrigeneous signal increase and this δ¹³C decrease in our record, as well as in other paleorecords, supports the hypothesis of a global aridification amongst others processes to explain the deep-water masses isotopic signature changes during the MPT. In any case, the isotopic shifts imply major changes in the end-member δ¹⁸O and δ¹³C values of deep waters.  相似文献   

Considerations for modeling burn probability across landscapes with steep environmental gradients: an example from the Columbia Mountains, Canada   总被引：1，自引：0，他引：1  

Marc-André Parisien  Gregg R. Walker  John M. Little  Brian N. Simpson  Xianli Wang  Daniel D. B. Perrakis 《Natural Hazards》2013,66(2):439-462

Fire and land management in fire-prone areas can be greatly enhanced by estimating the likelihood of fire at every point on the landscape. In recent years, powerful fire simulation models, combined with an in-depth understanding of an area’s fire regime and fire environment, have allowed forest managers to estimate spatial burn probabilities. This study describes a methodology for selecting input data and model parameters when creating burn probability maps in difficult-to-model areas and reports the results of a case study for a large area of the Columbia Mountains, British Columbia, Canada. In addition to having particularly mountainous topography, the study area is covered by vegetation types that are poorly represented in fire behavior systems, even though these vegetation types have experienced considerable (if highly irregular) fire activity in premodern times (before 1920). Parameterization of the fire environment for simulation modeling was accomplished by combining various types of fire information (e.g., fire history studies, reconstructed fire climatologies), new technologies (high-resolution remotely sensed data, wind flow modeling), and—a must in data-limited areas—ample expert advice. In this study, we made extensive use of personal accounts from experienced fire behavior officers for the creation of model inputs. Despite difficulties in validating outputs of burn probability models, the multisource model-building approach described here provides a conservative, yet informative, means of estimating the likelihood of fire. Due to the data-intensive nature of the modeling and paucity of input data, an argument is made that modelers must focus on the inputs that are the most influential for their study area.  相似文献   

Granite emplacement by crustal boudinage: example of the Calmayo and El Hongo plutons (Córdoba,Argentina)     

Fernando D'Eramo  José M. Tubía  Lucio Pinotti  Néstor Vegas  Jorge Coniglio  Manuel Demartis  Aitor Aranguren  Miguel Basei 《地学学报》2013,25(5):423-430

This study deals with the structure and emplacement of the Calmayo and El Hongo trondhjemite plutons (Famatinian belt of Córdoba, Argentina). It provides structural data from the granites and the country rocks and a study of the magnetic fabric in the plutons. New U/Pb geochronological data yield intrusion ages of 512.1 ± 3.4 Ma and 500.6 ± 4.5 Ma for the Calmayo and El Hongo plutons respectively. The El Hongo massif and the southern part of the Calmayo trondhjemite preserve magmatic structures, whereas the northern domain of Calmayo shows the imprint of solid‐state deformation. The main foliation in the country rocks outlines a boudin‐like pattern at the map scale and the granites are located along boudin necks, suggesting that the emplacement of these trondhjemite plutons was linked to large‐scale boudinage of the country rocks.  相似文献   

Seismotectonic versus man-induced morphological changes in a cave on the Arrábida chain (Portugal)     

José António Crispim 《Geodinamica Acta》2013,26(3-4):135-142

Abstract

Distinctions between cave morphologies originating from seismic or active tectonics and those generated by natural clastic breakdown or by human activity must be made using unambiguous interpretative criteria.

Easily accessible caves in particular, which may have been visited for centuries or millennia, or caves located near engineering works or quarries using great quantities of explosives, may have broken speleothems, breakdowns or detachment joints unrelated to seismic events or tectonic movements.

Zambujal cave lies near neotectonic and seismic structures associated with a Plio-Quatemary 200 m uplift of the Arrábida chain and has suffered impacts resulting from quarrying, followed by possible vandalism. It is thus an example for which it is difficult to decipher morphological agents as there is the possibility that identical forms have been generated by several causes, which may have repeated at different episodes of its evolution. However, a careful morphological interpretation makes it possible to accept the existence of two seismic episodes, an “ancient” one and a “modern” one. The detection of other episodes between these is only possible using absolute dating. © Elsevier, Paris  相似文献   

A methodological approach of fluvial dynamics oriented towards hydrosystem management: case study of the Loire and Allier rivers     

Emmanuèle Gautier  Hervé Piégay  Patrick Bertaina 《Geodinamica Acta》2013,26(1):29-43

Abstract

This study was conducted as part of the European LIFE Loire Nature program for the conservation and management of a 110-km-long section of the Loire and Allier rivers, an area renowned for its ecological richness. The methodological approach is based on statistical analysis (bivariate and multivariate analyses) of hydro-geomorphologic and biogeographical variables, complemented by reach typology and mapping. The main results show, on the one hand, the great spatial variability of fluvial mosaic complexity along the river continuum and on the other hand, some independence between the riparian forest characteristics and the channel forms. The fluvial pattern (e.g. anabranching) and the forest establishment along the Loire river register specific features. © 2000 Éditions scientifiques et médicales Elsevier SAS  相似文献   

Biosphère,biosphères…     

André Schaaf  Jean-Michel Caron 《Geodinamica Acta》2013,26(2-3):87-102

Résumé

En douze paragraphes, qui balaient l’âge de la Terre depuis ses origines jusqu’à Homo sapiens, nous tenterons de montrer la richesse conceptuelle qu’engendre l’étude de la biosphère actuelle et des biosphères passées. © 2000 Éditions scientifiques et médicales Elsevier SAS  相似文献   

The colonization success of an exotic Poaceae is related to native macrophyte richness, wind disturbance and riparian vegetation     

Sidinei Magela Thomaz  Márcio José Silveira  Thaisa Sala Michelan 《Aquatic Sciences - Research Across Boundaries》2012,74(4):809-815

Biotic and abiotic factors are filters that prevent invasions in aquatic and terrestrial ecosystems. In this investigation we tested the hypothesis that the success of a non-native Poaceae (Urochloa subquadripara) is positively correlated with the richness of native macrophytes and negatively correlated with wind disturbance (fetch) and presence of riparian vegetation on coarse spatial scales. Our samplings were carried out in a tropical reservoir (Rosana Reservoir, Brazil). We first compared competing models using the Akaike criterion to find the main combinations of explanatory variables (native macrophyte richness, fetch, and presence of riparian vegetation) associated with the success of U. subquadripara. Then, we applied multiple regressions to assess the coefficient of determination of the best models selected according to the Akaike criterion. The probability of occurrence of U. subquadripara increased significantly with increases in the number of native macrophyte species, but decreased with fetch and the presence of riparian vegetation. Stand width and maximum depth of occurrence (indicators of the success of this Poaceae) were also positively related with native richness and negatively with fetch and riparian vegetation. Our results supported our expectation that wave disturbance is an important variable explaining U. subquadripara success. Because the less exposed sites are also more favorable for colonization by natives, positive relationships between the success of non-native species and native diversity emerge at the coarse scale. Taken together, our results support the theory of “biotic acceptance”; that is, favorable sites are more prone to colonization by both native and non-native species.  相似文献   

Longitudinal and temporal thermal patterns of the French Rh?ne River using Landsat ETM+ thermal infrared images     

Vincent Wawrzyniak  Hervé Piégay  Alain Poirel 《Aquatic Sciences - Research Across Boundaries》2012,74(3):405-414

Understanding the thermal regime of rivers is a key issue for predicting ecosystem change in the context of global warming. However, water temperature is not only influenced by air temperature. To better highlight relative contribution of factors controlling water temperature, we used satellite thermal infrared (TIR) images from Landsat ETM+ to investigate longitudinal and temporal variations in thermal patterns of the French Rh?ne River. Because satellite TIR remote sensing is limited to large rivers, we used an automated water extraction technique to remove pixels contaminated by terrestrial surfaces. We calculated water surface temperatures of the 500?km long reach for 83 dates between 1999 and 2009. The average accuracy and uncertainty of our data, ±1.1 and ±0.4°C for reaches with more than 3?pixels across and ±1.4 and ±0.5°C for reaches with one to 3?pixels across, are comparable to other satellite TIR studies of rivers. Our results confirmed previous studies on the thermal impacts of tributaries and nuclear power plants on the Rh?ne, providing an understanding of their seasonal pattern and their longitudinal impact. We showed temperature differences of 0?C2°C within the largest hydroelectric bypass facilities between the bypass section and the canal, with Montélimar and Caderousse showing the most pronounced differences. Discussion points concern the potential impacts of tributaries and nuclear power plants on the spatio-temporal thermal patterns, as well as the factors responsible for thermal differences in the bypass facilities: length and minimum flow of the bypass section, and tributaries coming into this reach.  相似文献   

Establishing the wave climate influence on the morphodynamics of a coastal lagoon inlet     

Sandra Plecha  Paulo A. Silva  Anabela Oliveira  João M. Dias 《Ocean Dynamics》2012,62(5):799-814

The morphologic changes in estuaries and coastal lagoons are very complex and constitute a challenging task in coastal research. The bathymetric changes result from the combined action of tides, waves, rivers discharge and wind stress in the area of interest. Additionally, an accurate knowledge of the sediment transport is essential to achieve a good morphological characterization. This work establishes the influence of the wave climate on the morphodynamics of the Ria de Aveiro lagoon inlet by analysing the numerical results of the morphodynamic modelling system MORSYS2D. The numerical simulations considered a realistic coupled forcing of tidal currents and waves. The computed sediment fluxes and bathymetric changes are analysed and compared with the erosion and accretion trends obtained from the numerical simulations forced only by tidal currents, in order to establish the wave climate influence. The final bathymetry and the corresponding changes are compared with bathymetric data collected through surveys. It is concluded that: (a) the morphodynamics of the study area is dominated by the wave regime in the lagoon inlet and nearshore areas, while in the inner areas is tidally dominated; and (b) the inclusion of the wave regime forcing constitutes an improvement in order to accurately reproduce the local morphodynamics.  相似文献   

Escherichia coli Inactivation in Fresh Water Through Photocatalysis with TiO2‐Effect of H2O2 on Disinfection Kinetics          下载免费PDF全文

Jorge Rodríguez‐Chueca  Maria Peña Ormad  Rosa Mosteo  Saúl Canalis  José Luis Ovelleiro 《洁净——土壤、空气、水》2016,44(5):515-524

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