Tectonic and oceanographic control of sedimentary patterns in a small oceanic basin: Dove Basin (Scotia Sea,Antarctica)          下载免费PDF全文

Lara F. Pérez  Andrés Maldonado  Francisco Javier Hernández‐Molina  Emanuele Lodolo  Fernando Bohoyo  Jesús Galindo‐Zaldívar 《Basin Research》2017,29(Z1):255-276

Dove Basin, a small oceanic domain located within the southern Scotia Sea, evidences a complex tectonic evolution linked to the development of the Scotia Arc. The basin also straddles the junction between the main Southern Ocean water masses: the Antarctic Circumpolar Current (ACC), the Southeast Pacific Deep Water (SPDW) and the Weddell Sea Deep Water (WSDW). Analysis of multichannel seismic reflection profiles, together with swath bathymetry data, reveals the main structure and sediment distribution of the basin, allowing a reconstruction of the tectonostratigraphic evolution of the basin and assessment of the main bottom water flows that influenced its depositional development. Sediment dispersed in the basin was largely influenced by gravity‐driven transport from adjacent continental margins, later modified by deep bottom currents. Sediments derived from melting icebergs and extensive ice sheets also contributed to a fraction of the basin deposits. We identify four stages in the basin evolution which – based on regional age assumptions – took place during the early Miocene, middle Miocene, late Miocene–early Pliocene and late Pliocene–Quaternary. The onsets of the ACC flow in Dove Basin during the early Miocene, the WSDW flow during the middle Miocene, and the SPDW during the late Miocene were influenced by tectonic events that facilitated the opening of new oceanic gateways in the region. The analysis of Dove Basin reveals that tectonics is a primary factor influencing its sedimentary stacking patterns, the structural development of new oceanic gateways permitting the inception of deep‐water flows that have since controlled the sedimentary processes.  相似文献   

Assessment of CHADFDM satellite-based input dataset for the groundwater recharge estimation in arid and data scarce regions     

Nafiseh Salehi Siavashani  Joaquin Jimenez-Martinez  Guillermo Vaquero  Francisco J. Elorza  Justin Sheffield  Lucila Candela  Aleix Serrat-Capdevila 《水文研究》2021,35(6):e14250

Aquifer natural recharge estimations are a prerequisite for understanding hydrologic systems and sustainable water resources management. As meteorological data series collection is difficult in arid and semiarid areas, satellite products have recently become an alternative for water resources studies. A daily groundwater recharge estimation in the NW part of the Lake Chad Basin, using a soil–plant-atmosphere model (VisualBALAN), from ground- and satellite-based meteorological input dataset for non-irrigated and irrigated land and for the 2005–2014 period is presented. Average annual values were 284 mm and 30°C for precipitation and temperature in ground-based gauge stations. For the satellite-model-based Lake Chad Basin Flood and Drought Monitor System platform (CHADFDM), average annual precipitation and temperature were 417 mm and 29°C, respectively. Uncertainties derived from satellite data measurement could account for the rainfall difference. The estimated mean annual aquifer recharge was always higher from satellite- than ground-based data, with differences up to 46% for dryland and 23% in irrigated areas. Recharge response to rainfall events was very variable and results were very sensitive to: wilting point, field capacity and curve number for runoff estimation. Obtained results provide plausible recharge values beyond the uncertainty related to data input and modelling approach. This work prevents on the important deviations in recharge estimation from weighted-ensemble satellite-based data, informing in decision making to both stakeholders and policy makers.  相似文献   

Interprétation des cisaillements ductiles vers le NE dans les gneiss de Torrox (Complexe Alpujarride,Cordillères Bétiques)     

Julia Cuevas  Francisco Navarro-Vilá  José M. Tubía 《Geodinamica Acta》2013,26(1):107-116

Résumén

Les Gneiss de Torrox font partie de l’Unité de Sayalonga, appartenant au Complexe Alpujarride des Cordillères Bétiques (Espagne). Ils ont subi une déformation hétérogène par cisaillement simple, caractérisée par le développement de zones mylonitiques à pendage subhorizontal et de linéations d’étirement de direction N070°E. Nous interprétons ces linéations comme la direction de transport dans un contexte de chevauchements ductiles vers l’Kst-Nord-est. Ce sens de mouvement est très répandu dans les Alpujarrides, et permet de mieux comprendre que les nappes Alpujarrides occidentales soient plus métamorphiques que celles des Alpujarrides centrales et orientales.  相似文献   

Is net ecosystem production higher in natural relative to constructed wetlands?     

Cecilia Español  Belinda Gallardo  M. Rosa Pino  Ana Martín  Francisco A. Comín 《Aquatic Sciences - Research Across Boundaries》2013,75(3):385-397

Ecosystem metabolism is an important measure of wetland restoration efficiency, and serves to indicate if the system is capable of processing energetic resources. Despite its value, ecosystem metabolism has rarely been included in monitoring programs. In this study, we aimed to achieve the following objectives: (i) compare net ecosystem production (NEP) rates of constructed vs. natural wetlands; (ii) identify the highest NEP rate habitats; and (iii) define the main environmental factors regulating NEP in different wetland types. Pelagic and benthic NEP rates and physicochemical features were measured in three natural and five constructed wetlands in the middle Ebro River floodplain (NE Spain). Statistical analyses showed pelagic NEP rates peaked in natural wetlands, which produced up to 187.5 mg C m^?3 h^?1 compared to lower rates in constructed wetlands (up to 46.2 mg C m^?3 h^?1). Pelagic NEP responded positively to temperature, total dissolved solids, and nutrients. Benthic NEP rates were 3 to 30-fold greater than pelagic in natural (up to 994.9 mg C m^?3 h^?1) and constructed (up to 1,551.5 mg C m^?3 h^?1) wetlands, and were heavily influenced by habitat type, with NEP peaking in areas dominated by submerged vegetation and fine organic sediment. Rapid recovery in aquatic communities (i.e. macroinvertebrate diversity) has been previously reported for the studied wetlands; however, our study suggests a slower recovery of functional processes (i.e. pelagic NEP) in constructed habitats. We therefore strongly advocate the inclusion of ecosystem function in the design and evaluation of restoration projects to optimise long-term wetland ecosystem sustainability.  相似文献   

Actual state of European wetlands and their possible future in the context of global climate change     

Hana Čížková  Jan Květ  Francisco A. Comín  Raija Laiho  Jan Pokorný  David Pithart 《Aquatic Sciences - Research Across Boundaries》2013,75(1):3-26

The present area of European wetlands is only a fraction of their area before the start of large-scale human colonization of Europe. Many European wetlands have been exploited and managed for various purposes. Large wetland areas have been drained and reclaimed mainly for agriculture and establishment of human settlements. These threats to European wetlands persist. The main responses of European wetlands to ongoing climate change will vary according to wetland type and geographical location. Sea level rise will probably be the decisive factor affecting coastal wetlands, especially along the Atlantic coast. In the boreal part of Europe, increased temperatures will probably lead to increased annual evapotranspiration and lower organic matter accumulation in soil. The role of vast boreal wetlands as carbon sinks may thus be suppressed. In central and western Europe, the risk of floods may support the political will for ecosystem-unfriendly flood defence measures, which may threaten the hydrology of existing wetlands. Southern Europe will probably suffer most from water shortage, which may strengthen the competition for water resources between agriculture, industry and settlements on the one hand and nature conservancy, including wetland conservation, on the other.  相似文献   

Mobility Patterns of Overseas Human Capital in Australia: the role of a ‘new’ graduate visa scheme and rural development policy     

Francisco Rowe  Jonathan Corcoran  Alessandra Faggian 《The Australian geographer》2013,44(2):177-195

In 2007, the Australian federal government introduced a ‘new’ graduate visa scheme, the 485 visa sub-class. This visa facilitates the transition from student to worker for overseas graduates from Australian higher education institutions, with the potential to significantly increase their numbers in the country. At the same time, local governments have introduced various policies designed to attract and retain human capital in rural areas to address the shortfall of highly skilled individuals. This paper redresses the current lack of research into the spatial dynamics of overseas human capital in Australia and their relation to the new visa scheme in combination with shifts in rural development policies. Drawing on survey data of graduates describing the ‘before’ (2005) and ‘after’ (2008) periods of the introduction of the 485 visa scheme, this paper shows that the propensity of overseas graduates to move between Australia's regions has increased substantially. In particular, there have been an increasing proportion of overseas graduates moving to major cities despite rural development policy efforts to attract human capital to rural areas. However, these policy efforts appear to have attracted overseas graduates with particular qualifications (education and health) to work in such locales.  相似文献   

A population density grid for Spain     

Francisco J. Goerlich  Isidro Cantarino 《International journal of geographical information science》2013,27(12):2247-2263

This article describes a high-resolution land cover data set for Spain and its application to dasymetric population mapping (at census tract level). Eventually, this vector layer is transformed into a grid format. The work parallels the effort of the Joint Research Centre (JRC) of the European Commission, in collaboration with Eurostat and the European Environment Agency (EEA), in building a population density grid for the whole of Europe, combining CORINE Land Cover with population data per commune. We solve many of the problems due to the low resolution of CORINE Land Cover, which are especially visible with Spanish data. An accuracy assessment is carried out from a simple aggregation of georeferenced point population data for the region of Madrid. The bottom-up grid constructed in this way is compared to our top-down grid. We show a great improvement over what has been reported from commune data and CORINE Land Cover, but the improvements seem to come entirely from the higher resolution data sets and not from the statistical modeling in the downscaling exercise. This highlights the importance of providing the research community with more detailed land cover data sets, as well as more detailed population data. The dasymetric grid is available free of charge from the authors upon request.  相似文献   

Tunnel stability analysis during construction using a neuro‐fuzzy system     

Jos Luis Rangel  Ursula Iturrarn‐Viveros  A. Gustavo Ayala  Francisco Cervantes 《国际地质力学数值与分析法杂志》2005,29(15):1433-1456

This paper presents an alternative strategy to evaluate the stability of tunnels during the design and construction stages based on a hybrid system, composed by neural, neuro‐fuzzy and analytical solutions. A prototype of this system is designed using a database formed by 261 cases, 45 real and the rest synthetic. This system is capable of reproducing the displacements induced at the periphery of the tunnel before and after support installation. The stability of the excavation process is evaluated using a criterion that considers dimensionless parameters based on the shear strength of the media, the induced deformation level in the ground, the plastic radii and the advance of excavation without support. The efficiency and validity of the prototype is verified with two examples of actual tunnels, one included in the database used to train the system and the other not included. The results of both examples show a better approximation than other commonly used techniques. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Integral Field Spectroscopy with Gemini: Support for IFU data in the Gemini IRAF package     

James E.H. Turner  Bryan W. Miller  Tracy L. Beck  Inseok Song  Andrew J. Cooke  Robert L. Seaman  Francisco G. Valds 《New Astronomy Reviews》2006,49(10-12):655

We present a brief overview of facilities for Integral Field Spectroscopy at the Gemini Observatory. These include four optical and near-infrared IFUs suitable for high spatial resolution work and a suite of tasks for handling IFU data in the Gemini IRAF package. We describe the tools for data reduction that are available now or planned in the near future, helping investigators make productive use of these ground-breaking instruments. Further details on the individual IFUs, specific science applications and reduction examples are given in associated presentations by Beck et al., Carrasco et al., Trancho et al. and Winge et al.  相似文献   

Aquifer interactions with a polluted mountain river of Nicaragua     

Jose Alfredo Mendoza  Peter Ulriksen  Francisco Picado  Torleif Dahlin 《水文研究》2008,22(13):2264-2273

The interactions between a stream and nearby shallow aquifers were investigated in a mountain basin being polluted by mercury released during mining in central Nicaragua. Hourly data series of water levels and temperatures were analysed using cross‐correlation. Resistivity imaging was used to map the subsurface and to complement the hydrological data interpretation. The results show the complex hydrogeological conditions that characterize the region, with weathering and fractured rock as main contributors to groundwater transport. The resistivity images suggest the presence of two vertical dykes perpendicular to the stream, and zones rich in clay. The data series indicate a rapid response from the aquifers to recharge events, followed by immediate discharge on a yearly basis. Furthermore, alternating periods of stream infiltration and aquifer discharge were identified. This work demonstrates that surface water pollution is a threat to groundwater quality in the area. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献