Lithological classification assisted by the joint inversion of electrical and seismic data at a control site in northeast Mexico

In this paper, evidence is presented that the combination of geospectral images and geophysical signatures (resistivity–velocity cross-plots) is a good tool to provide a natural visualization of the distribution and variations of lithological features in a test site. This was confirmed by the correlation between the electrical resistivity and seismic velocity values obtained after cross-gradient joint inversion at two profiles and geotechnical information provided by shallow boreholes in a site located in the Earth Sciences School grounds in Linares, Northeastern Mexico. The results obtained from this study show how the cross-gradient joint inversion facilitates the analysis of hydrological estimates and assists in lithological classification of subsurface materials.     

The Grenville-age basement of the Andes

The analysis of the basement of the Andes shows the strong Grenville affinities of most of the inliers exposed in the different terranes from Colombia to Patagonia. The terranes have different histories, but most of them participated in the Rodinia supercontinent amalgamation during the Mesoproterozoic between 1200 and 1000 Ma. After Rodinia break-up some terranes were left in the Laurentian side such as Cuyania and Chilenia, while others stayed in the Gondwanan side. Some of the terranes once collided with the Amazon craton remained attached, experiencing diverse rifting episodes all along the Phanerozoic, as the Arequipa and Pampia terranes. Some other basement inliers were detached in the Neoproterozoic and amalgamated again to Gondwana in the Early Cambrian, Middle Ordovician or Permian times. A few basement inliers with Permian metamorphic ages were transferred to Gondwana after Pangea break-up from the Laurentian side. Some of them were part of the present Middle America terrane. An exceptional case is the Oaxaquia terrane that was detached from the Gondwana margin after the Early Ordovician and is now one of the main Mexican terranes that collided with Laurentia. These displacements, detachments, and amalgamations indicate a complex terrane transfer between Laurentia and Gondwana during Paleozoic times, following plate reorganizations and changes in the absolute motion of Gondwana.     

Toward the application of ecological concepts in EU coastal water management

The EU Water Framework Directive demands the protection of the functioning and the structure of our aquatic ecosystems. The defined means to realize this goal are: (1) optimization of the habitat providing conditions and (2) optimizing the water quality. The effects of the measures on the structure and functioning of the aquatic ecosystems then has to be assessed and judged. The available tool to do this is 'monitoring'. The present monitoring activities in The Netherlands cover target monitoring and trend monitoring. This is insufficient to meet the requirements of the EU. It is, given the EU demands, the ongoing budget reductions in The Netherlands and an increasing flow of unused new ecological concepts and theories (e.g. new theoretical insights related to resource competition theory, intermediate disturbance hypothesis and tools to judge the system quality like ecological network analysis) suggested to reconsider the present monitoring tasks among governmental services (final responsibility for the program and logistic support) and the academia (data analyses, data interpretation and development of concepts suitable for ecosystem modelling and tools to judge the quality of our ecosystems). This will lead to intensified co-operation between both arena's and consequently increased exchange of knowledge and ideas. Suggestions are done to extend the Dutch monitoring by surveillance monitoring and to change the focus from 'station oriented' to 'area oriented' without changing the operational aspects and its costs. The extended data sets will allow proper calibration and validation of developed dynamic ecosystem models which is not possible now. The described 'cost-effective' change in the environmental monitoring will also let biological and ecological theories play the pivotal role they should play in future integrated environmental management.     

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

The analyses of the main parameters controlling the present Chile‐type and Marianas‐type tectonic settings developed along the eastern Pacific region show four different tectonic regimes: (1) a nearly neutral regime in the Oregon subduction zone; (2) major extensional regimes as the Nicaragua subduction zone developed in continental crust; (3) a Marianas setting in the Sandwich subduction zone with ocean floored back‐arc basin with a unique west‐dipping subduction zone and (4) the classic and dominant Chile‐type under compression. The magmatic, structural and sedimentary behaviours of these four settings are discussed to understand the past tectonic regimes in the Mesozoic Andes based on their present geological and tectonic characteristics. The evaluation of the different parameters that governed the past and present tectonic regimes indicates that absolute motion of the upper plate relative to the hotspot frame and the consequent trench roll‐back velocity are the first order parameters that control the deformation. Locally, the influences of the trench fill, linked to the dominant climate in the forearc, and the age of the subducted oceanic crust, have secondary roles. Ridge collisions of seismic and seismic oceanic ridges as well as fracture zone collisions have also a local outcome, and may produce an increase in coupling that reinforces compressional deformation. Local strain variations in the past and present Andes are not related with changes in the relative convergence rate, which is less important than the absolute motion relative to the Pacific hotspot frame, or changes in the thermal state of the upper plate. Changes in the slab dip, mainly those linked to steepening subduction zones, produce significant variations in the thermal state, that are important to generate extreme deformation in the foreland. Copyright © 2009 John Wiley & Sons, Ltd.     

Silica Gel as a Surrogate for Biogenic Silica in Batch Dissolution Experiments at pH 9.2: Further Testing of the Shrinking Object Model and a Novel Approach to the Dissolution of a Population of Particles

Recently, the increase in dissolved concentration in the batch dissolution of various salts or sucrose has been successfully modelled with three equations, one a cubic in time. However, from three separate earlier investigations with ocean sediments and phytoplankton frustules, there is residual suspicion that biogenic silica does not follow this behaviour. This paper shows that the Shrinking Object Model applies to the dissolution of sieved silica gel particles, as well as to a sample of unsieved, freeze-dried frustules of Odentella sp. Silica gel, being readily available in quantities that can be sieved, is a useful surrogate for biogenic silica in allowing problems of experimental design to be overcome. The dissolutions covered three possible analytic integrations that arise from the model: an exponential for approach to saturation with excess solid silica; the approach to near saturation with either a slight excess or deficiency of silica; dissolution at high under-saturation. Good agreement was found between experimental results and mathematical modelling. The paper provides template calculations by which future raw results can be parameterized. Nevertheless, the reasons for non-linear kinetics reported in earlier work have not been identified, and so controversy over non-linear dissolution kinetics is enhanced. Stirring regime was found to be important with silica gel dissolution, and so biogenic silica dissolution is therefore likely to be ‘transport limited’ at low stirring rate. Accordingly, all archived and future data should be scrutinized for stirring effects before being applied to the oceanic environment. A rigorous test for determining whether a substance’s dissolution deviates from the model is recommended as a preliminary to any future dissolutions, whether in batch or with the chemo-stat. A fixed amount of frustule sample is added to a series of buffered mixtures containing increasing background silicic acid concentrations. Absence of any problem is marked by a linear plot between the increase in silicic concentration accruing over a fixed reaction period and that of the background silicic acid. A novel mathematical proof is provided to justify the test’s use. The reasons for the earlier deviations from expected behaviour of, for example, oceanic sediments, are discussed. Lastly, the paper provides a novel approach to the dissolution of a population of particles of mixed sizes which will probably find ready future application in oceanography.     

Geographic influences on sexual and reproductive health service utilization in rural Mozambique

The HIV/AIDS epidemic remains a major public health issue across the globe, and it is of particular concern in sub-Saharan Africa. Utilization of sexual and reproductive health (SRH) services can significantly impact HIV prevention, transmission, and treatment. SRH service utilization may be determined by individual characteristics, such as education and economic status, but also by the location and accessibility of health care facilities. Using population-based survey data, this study applies exploratory spatial analysis techniques to examine spatial patterns of SRH service utilization among rural married women in southern Mozambique. Clustering among those using services is found as are spatial associations, indicating significant spatial variability in the utilization of health services. The findings provide valuable insights for current and future health care program planning and configuration.     

Landslide Susceptibility Mapping Using Remotely Sensed Data through Conditional Probability Analysis Using Seed Cell and Point Sampling Techniques

Rapid urbanization, intense infra-structure development and increased tourism related activities have resulted in the change of landscape of the Kodaikkanal town and its surrounding, a popular hill town in Tamilnadu, South India. As an after effect, the numbers of landslides and rock-falls have increased steadily in the past decade. Landslide susceptibility analysis is carried out for this area using conditional probability analysis. The geo-spatial database for mapping landslide susceptibility consists of the factors - Relief, Slope, Aspect, Curvature, Weathering, Land use, Topographic Wetness Index and Proximity to road. Two sampling strategies ?C point and seed-cell are compared for landslide susceptibility mapping. The Landslide Susceptibility map developed using conditional probability method is verified using R index for both sampling strategies. The study shows that both the sampling strategies perform with good accuracy, seed cell technique excels slightly over point sampling. 86.11% of the landslides fall in the high and critical susceptible zones. The results show that conditional probability technique provides a simple tool for susceptibility analysis. The method can be used at regional scale and is a valuable input for planning purpose.     

Spatial and temporal distribution of landlocked Galaxias maculatus and Galaxias platei (Pisces: Galaxiidae) in a lake in the South American Andes

Galaxiids are present in many of the Andean lakes in southern South America. We studied landlocked Galaxias maculatus (Jenyns) and Galaxias platei Steindachner populations in a deep oligotrophic lake (Lake Gutiérrez, Patagonia, Argentina). Their temporal and spatial distribution, intralacustrine movements (horizontal and vertical), and spawning periods were analysed using several sampling techniques (ichthyoplankton net, seine net, gill net, and baited benthic taps). We identified the early life stages of both species based on their morphology and otolith shape. The free embryos of both species migrate to the limnetic zone, where they coexist as larvae, facing the same food availability and probably the same predation risk. Each species then moves on to its own juvenile and adult habitat: the littoral and benthic zone for G. maculatus and only the deeper benthic zone for G. platei. Their adult habitats and part of their spawning periods partly overlap.     

The millennial atmospheric lifetime of anthropogenic CO<Subscript>2</Subscript>

The notion is pervasive in the climate science community and in the public at large that the climate impacts of fossil fuel CO₂ release will only persist for a few centuries. This conclusion has no basis in theory or models of the atmosphere/ocean carbon cycle, which we review here. The largest fraction of the CO₂ recovery will take place on time scales of centuries, as CO₂ invades the ocean, but a significant fraction of the fossil fuel CO₂, ranging in published models in the literature from 20–60%, remains airborne for a thousand years or longer. Ultimate recovery takes place on time scales of hundreds of thousands of years, a geologic longevity typically associated in public perceptions with nuclear waste. The glacial/interglacial climate cycles demonstrate that ice sheets and sea level respond dramatically to millennial-timescale changes in climate forcing. There are also potential positive feedbacks in the carbon cycle, including methane hydrates in the ocean, and peat frozen in permafrost, that are most sensitive to the long tail of the fossil fuel CO₂ in the atmosphere.