Oxygen isotope compositions of phosphate from arvicoline teeth and Quaternary climatic changes, Gigny, French Jura

Oxygen isotope compositions of biogenic phosphates from mammals are widely used as proxies of the isotopic compositions of meteoric waters that are roughly linearly related to the air temperature at high- and mid-latitudes. An oxygen isotope fractionation equation was determined by using present-day European arvicoline (rodents) tooth phosphate: δ¹⁸O_p = 20.98(±0.59) + 0.572(±0.065) δ¹⁸O_w. This fractionation equation was applied to the Late Pleistocene karstic sequence of Gigny, French Jura. Comparison between the oxygen isotope compositions of arvicoline tooth phosphate and Greenland ice core records suggests to reconsider the previously established hypothetical chronology of the sequence. According to the δ¹⁸O value of meteoric water-mean air temperature relationships, the δ¹⁸O value of arvicoline teeth records variations in mean air temperatures that range from 0° to 15°C.     

DFT study of the cation arrangements in the octahedral and tetrahedral sheets of dioctahedral 2:1 phyllosilicates

Quantum mechanical calculations based on the density functional theory (DFT) are used to study the crystal structures of dioctahedral 2:1 phyllosilicates. The isomorphous cation substitution is investigated by exploring different substitutions of octahedral Al³⁺ by Mg²⁺ or Fe³⁺, tetrahedral substitution of Si⁴⁺ by Al³⁺, and different interlayer cations (IC) (Na⁺, K⁺, Ca²⁺, and Mg²⁺). Samples with different kinds of layer charges are studied: only tetrahedrally charged, only octahedrally charged, or mixed octahedral/tetrahedral charged. The effect of the relative arrangements of these substitutions on the lattice parameters and total energy is studied. The experimental observation of segregation tendency of Fe³⁺ and dispersion tendency of Mg²⁺ in the octahedral sheet is reproduced and explained with reference to the relative energies of the octahedral cation arrangements. These energies are higher than those due to the IC/tetrahedral and IC/octahedral relative arrangements. The tetrahedral and octahedral substitutions that generate charged layers also tend to be dispersed. The octahedral cation exchange potentials change with the IC-charge/ionic radius value.     

Microdeformation of lacustrine laminite sequences from Late Miocene formations of SE Spain: an interpretation of loop bedding

Lacustrine laminated sediments (laminites) present in Late Miocene formations of the Híjar Basin, SE Spain, display well developed loop bedding, a structure consisting of bundles of laminae that are sharply constricted at intervals, giving a morphology of loops or links of a chain. The laminite sequences, which are interbedded with turbidite marlstones, were accumulated on the bottom of a permanently stratified lake developed in a rapidly subsiding basin limited by 010° and 105° normal faults. As deduced from both macro- and microdeformational analyses, the basin evolved under an extensional stress field throughout the Late Miocene. Four main types of loops, simple and complex loops with subcategories, have been recognized within the laminite sequence. Simple loops of type 1 show the best definite pattern, quite similar to ' pinch and swell structures ', a type of boudinage typical of stretching of alternating beds where the competence contrast is not strongly marked. The remaining loop types display contortion and occasional breakage of laminae (microfaulted edges) indicative of microdeformation near the boundary between the ductile-brittle deformational fields. The distribution of the various loop types across the laminite sequence reflects an interplay between progressive lithification of the laminites as sedimentation progressed and tectonic stresses which affected the sediment sequence. Accordingly, a mechanism of deformation under an extensional stress field, ultimately related to the creep movement of the main basin faults which resulted in successive seismic shocks of low magnitude, is proposed to explain the formation of loop bedding in the laminites.     

Augmented reality and photogrammetry: A synergy to visualize physical and virtual city environments

Close-range photogrammetry is based on the acquisition of imagery to make accurate measurements and, eventually, three-dimensional (3D) photo-realistic models. These models are a photogrammetric product per se. They are usually integrated into virtual reality scenarios where additional data such as sound, text or video can be introduced, leading to multimedia virtual environments. These environments allow users both to navigate and interact on different platforms such as desktop PCs, laptops and small hand-held devices (mobile phones or PDAs). In very recent years, a new technology derived from virtual reality has emerged: Augmented Reality (AR), which is based on mixing real and virtual environments to boost human interactions and real-life navigations. The synergy of AR and photogrammetry opens up new possibilities in the field of 3D data visualization, navigation and interaction far beyond the traditional static navigation and interaction in front of a computer screen.In this paper we introduce a low-cost outdoor mobile AR application to integrate buildings of different urban spaces. High-accuracy 3D photo-models derived from close-range photogrammetry are integrated in real (physical) urban worlds. The augmented environment that is presented herein requires for visualization a see-through video head mounted display (HMD), whereas user’s movement navigation is achieved in the real world with the help of an inertial navigation sensor. After introducing the basics of AR technology, the paper will deal with real-time orientation and tracking in combined physical and virtual city environments, merging close-range photogrammetry and AR. There are, however, some software and complex issues, which are discussed in the paper.     

Do the shallow‐water habitats of a hypersaline tropical estuary act as nursery grounds for fishes?

Fish assemblages were studied in a hypersaline tropical estuary in Northeastern Brazil. A total of 104 species were collected by beach seine during the dry and rainy seasons of 2012. Two families, Atherinopsidae and Gerreidae, were numerically dominant in all zones of the estuary; juveniles of Atherinella brasiliensis, Eucinostomus argenteus, Lile piquitinga, Ulaema lefroyi, Lutjanus analis and Sphoeroides greeleyi contributed 77% of the total catch. The factors that best explained the fish abundance pattern were salinity and depth, which were related to spatial segregation. Species richness was lowest in the upper zone, an area with high salinity and shallow depth. The distinct roles of structurally different habitats (submerged macrophyte beds and mangrove prop‐roots) and the influence of physicochemical conditions in the middle zone of the estuary may influence taxonomic diversity. The middle zone of the estuary is the one most attractive to juveniles of reef species (Lutjanidae and Serranidae). The fish assemblages are clearly dominated by marine estuarine dependent species, highlighting the importance of the ecosystem as a nursery ground for marine species of the Brazilian coast.     

Geodetic methods for detecting volcanic unrest: a theoretical approach

In this paper we study the application of different geodetic techniques to volcanic activity monitoring, using theoretical analysis. This methodology is very useful for obtaining an idea of the most appropriate (and efficient) monitoring method, mainly when there are no records of geodetic changes previous to volcanic activity. The analysis takes into account the crustal structure of the area, its geology, and its known volcanic activity to estimate the deformation and gravity changes that might precede eruptions. The deformation model used includes the existing gravity field and vertical changes in the crustal properties. Both factors can have a considerable effect on computed deformation and gravity changes. Topography should be considered when there is a steep slope (greater than 10°). The case study of Teide stratovolcano (Tenerife, Canary Islands), for which no deformation or gravity changes are available, is used as a test. To avoid considering topography, we worked at the lowest level of Las Cañadas and examined a smaller area than the whole caldera or island. Therefore, the results are only a first approach to the most adequate geodetic monitoring system. The methodology can also be applied to active areas where volcanic risk is not associated with a stratovolcano but instead with monogenetic scattered centers, especially when sites must be chosen in terms of detection efficiency or existing facilities. The Canary Islands provide a good example of this type of active volcanic areas, and we apply our model to the island of Lanzarote to evaluate the efficiency of the monitoring system installed at the existing geodynamic station. On this island topography is not important. The results of our study show clearly that the most appropriate geodetic volcano monitoring system is not the same for all different volcanic zones and types, and the particular properties of each volcano/zone must be taken into account when designing each system.     

Analysis of the impact of large scale seismic retrofitting strategies through the application of a vulnerability-based approach on traditional masonry buildings

The buildings’ capacity to maintain minimum structural safety levels during natural disasters, such as earthquakes, is recognisably one of the aspects that most influence urban resilience. Moreover, the public investment in risk mitigation strategies is fundamental, not only to promote social and urban and resilience, but also to limit consequent material, human and environmental losses. Despite the growing awareness of this issue, there is still a vast number of traditional masonry buildings spread throughout many European old city centres that lacks of adequate seismic resistance, requiring therefore urgent retrofitting interventions in order to both reduce their seismic vulnerability and to cope with the increased seismic requirements of recent code standards. Thus, this paper aims at contributing to mitigate the social and economic impacts of earthquake damage scenarios through the development of vulnerability-based comparative analysis of some of the most popular retrofitting techniques applied after the 1998 Azores earthquake. The influence of each technique individually and globally studied resorting to a seismic vulnerability index methodology integrated into a GIS tool and damage and loss scenarios are constructed and critically discussed. Finally, the economic balance resulting from the implementation of that techniques are also examined.     

The role of gypsum and/or dolomite dissolution in tufa precipitation: lessons from the hydrochemistry of a carbonate–sulphate karst system

The precipitation of freshwater carbonates (tufa) along karstic rivers is enhanced by degassing of carbon dioxide (CO₂) downstream of karstic springs. However, in most karstic springs CO₂ degassing is not enough to force the precipitation of tufa sediments. Little is known about the role of dissolution of gypsum or dolomite in the hydrochemistry of these systems and how this affects the formation of tufa deposits. Here we present a monitoring study conducted over a year in Trabaque River (Spain). The river has typical karst hydrological dynamics with water sinking upstream and re‐emerging downstream of the canyon. Mixing of calcium–magnesium bicarbonate and calcium sulphate waters downstream of the sink enhances the dissolution of carbonates and potentially plays a positive role in the formation of tufa sediments. However, due to the common‐ion effect, dissolution of dolomite and/or gypsum causes precipitation of underground calcite cements as part of the incongruent dissolution of dolomite/dedolomitization process, which limits the precipitation of tufa sediments. Current precipitation of tufa is scant compared to previous Holocene tufa deposits, which likely precipitated from solutions with higher saturation indexes of calcite (SIcc values) than nowadays. Limited incongruent dissolution of dolomite/dedolomitization favours higher SIcc values. This circumstance occurs when waters with relatively high supersaturation of dolomite and low SO₄^2? composition sink in the upper sector of the canyon. In such a scenario, the process of mixing waters enhances the exclusive dissolution of limestones, preventing the precipitation of calcite within the aquifer and favouring the increase of SIcc values downstream of the springs. Such conditions were recorded during periods of high water level of the aquifers and during floods. This research shows that the common‐ion effect caused by the dissolution of gypsum and/or dolomite rocks can limit [or favour] the precipitation of tufa sediments depending on the occurrence [or not] of incongruent dissolution of dolomite/dedolomitization. Copyright © 2016 John Wiley & Sons, Ltd.     

A regional water balance indicator inferred from satellite images of an Andean endorheic basin in central-western Argentina

In the Central Andes of Argentina (30–37°S), snowmelt is the main source of freshwater, an essential natural resource for ~2.2 million people in the adjacent arid lowlands. In this region, Laguna Llancanelo collects the water inputs from the Malargüe endorheic basin. Previous studies concerning the annual and intra-annual variations of this lagoon and its relationship with regional climate are rare. We obtained a monthly record for the Laguna Llancanelo area (LLA, 1984–2013) using the modified normalized difference water index derived from Landsat images. Monthly LLA ranges between 35 km² and 411 km² and is significantly related to variations of the Río Malargüe, the main snow-fed tributary to the lagoon. There is no long-term relationship between LLA and local rainfall, but rapid increases in LLA result from heavy rainfall around the lagoon. Conversely, rapid reductions in LLA encompass periods with both reduced discharge from the Río Malargüe and low local rainfall. The LLA integrates moisture of both Pacific (snowfall in the upper Andes) and Atlantic (lowland rainfall) origins; therefore, we propose using LLA as an indicator of regional water balance.     

Cenozoic thick-skinned deformation and topography evolution of the Spanish Central System

The Spanish Central System is a Cenozoic pop-up with an E–W to NE–SW orientation that affects all the crust (thick-skinned tectonics). It shows antiform geometry in the upper crust with thickening in the lower crust. Together with the Iberian Chain it constitutes the most prominent mountainous structure of the Pyrenean foreland.The evolutionary patterns concerning the paleotopography of the interior of the Peninsula can be established by an analysis of the following data: gravimetric, topographical, macro and micro tectonic, sedimentological (infilling of the sedimentary basins of the relative foreland), P–T–t path from apatite fission tracks, paleoseismic and instrumental seismicity.Deformation is clearly asymmetric in the Central System as evidenced by the existence of an unique, large (crustal-scale) thrust at its southern border, while in the northern one there is a normal sequence of north verging thrusts, towards the Duero Basin, whose activity ended during the Lower Miocene. This deformation was accomplished under triaxial compression, Oligocene–Lower Miocene in age, marked by NW–SE to NNW–SSE shortening. Locally orientations of paleostresses deviate from that of the regional tensor, following a period of relative tectonic quiescence. During the Upper Miocene–Pliocene, a reactivation of constrictive stress occurred and some structures underwent rejuvenation as a consequence of the action of tectonic stresses similar to those of today (uniaxial extension to strike–slip with NW–SE shortening direction). However, the westernmost areas show continuous activity throughout the whole of the Tertiary, with no apparent pulses. At the present time there is a moderate seismic activity in the Central System related to faults that were active during the Cenozoic, with the same kinematic characteristics.