A pilot study of genetic differentiation between two phenotypes of a Mediterranean population of the bivalve Cerastoderma glaucum and genetic discrimination with other Cerastoderma glaucum and Cerastoderma edule populations outside the Mediterranean

The internal transcribed spacer 1 (ITS1) region of 29 individuals of Cerastoderma glaucum (from the Mediterranean Sea, the Atlantic and the North Sea) and 18 individuals of Cerastoderma edule (from the Atlantic and the North Sea) and the cytochrome c oxidase subunit I (COI) region of 43 individuals of C. glaucum (from the Mediterranean Sea, the Atlantic and the North Sea) and 9 individuals of C. edule (from the Atlantic and the North Sea) were PCR amplified and sequenced. The ITS1 sequences led us to describe 27 genetic haplotypes, while 21 genetic haplotypes were determined via the COI sequences. The ITS1 and the COI sequences revealed an important genetic variability within the Mediterranean population of C. glaucum, which contained two different phenotypes: orange foot and yellow foot. A genetic differentiation between the two phenotypes was revealed by the nucleotide diversity index (π) and is strengthened by the AMOVA analysis. This result leads us to suspect the presence of two different groups in the same population of C. glaucum. Nevertheless to be confirmed this hypothesis requires further studies using more locations and a larger number of sample sizes.     

Linking uplift,erosion, and sedimentation using landscape evolution models: Madagascar since the Late Cretaceous

We present a study to estimate the large-scale landscape history of a continental margin, by establishing a source-to-sink volume balance between the eroding onshore areas and the offshore basins. Assuming erosion as the primary process for sediment production, we strive to constrain a numerical model of landscape evolution that balances the volumes of eroded materials from the continent and that deposited in the corresponding basins, with a ratio imposed for loss of erosion products. We use this approach to investigate the landscape history of Madagascar since the Late Cretaceous. The uplift history prescribed in the model is inferred from elevations of planation surfaces formed at various ages. By fitting the volumes of terrigenous sediments in the Morondava Basin along the west coast and the current elevation of the island, the landscape evolution model is optimized by constraining the erosion law parameters and ratios of sediment loss. The results include a best-fit landscape evolution model, which features two major periods of uplift and erosion during the Late Cretaceous and the middle to late Cenozoic. The model supports suggestions from previous studies that most of the high topography of the island was constructed since the middle to late Miocene, and on the central plateau the erosion has not reached an equilibrium with the high uplift rates in the late Cenozoic. Our models also indicate that over the geological time scale a significant portion of materials eroded from Madagascar was not archived in the offshore basin, possibly consumed by chemical weathering, the intensity of which might have varied with climate.     

Impacts of Holocene and modern sea-level changes on estuarine mangroves from northeastern Brazil

Projections of the impacts of modern Relative Sea Level (RSL) rise on estuarine mangroves should be supported by coastal topographic data and records of mangrove dynamics under past RSL change. This work identified inland and seaward mangrove migrations along the Jucuruçu River (Bahia, Northeastern Brazil), during the Holocene based on sedimentary features, palynological and geochemical (δ¹³C, δ¹⁵N, C/N) data integrated with digital elevation models. During the Middle Holocene, in response to RSL rise, the estuary saw mangrove forest establish up to ~37 km inland. RSL stood between -1.4 (+0.36/-2.2 m) and +1 (2.19/0.2 m) around 7400 cal yr BP, and rose to a highest position of +3.25 (4.22/2.45 m) reached around 5350 cal yr BP. That marine incursion caused the inland replacement of freshwater vegetation by mangroves on tidal flats. Since then, the estuary experienced RSL fall, reducing inland tidal water salinity towards the Late Holocene, making that the mangroves were replaced by freshwater floodplain vegetation. Today, in the seaward part of the estuary near its mouth, mangroves occupy an area of ~10 km² along tidal channels. Considering a RSL rise of 98 cm up to the end of the 21^st century, at a rate significantly higher than that of Middle Holocene RSL rise (1.5 mm/yr) and fall (0.6 mm/yr), the current mangrove substrates are expected to drown and/or eroded near the coast, while new mangroves may establish inland, at topographically higher tidal flats in nowadays freshwater-tidal zones. Mangrove area could expand over 13 km² of coastal and flood plain. Following the same interaction between RSL/climate changes and Holocene mangrove dynamics, such upstream mangrove migration may be attenuated or intensified by changes in fluvial discharge. © 2019 John Wiley & Sons, Ltd.     

Groundwater components in the alluvial aquifer of the alpine Rhone River valley, Bois de Finges area, Wallis Canton, Switzerland

Source, type, and quantity of various components of groundwater, as well as their spatial and temporal variations were determined by different hydrochemical methods in the alluvial aquifer of the upper Rhone River valley, Bois de Finges, Wallis Canton, Switzerland. The methods used are hydrochemical modeling, stable-isotope analysis, and chemical analysis of surface water and groundwater. Sampling during high- and low-water periods determined the spatial distribution of the water chemistry, whereas monthly sampling over three years provided a basis for understanding seasonal variability. The physico-chemical parameters of the groundwater have spatial and seasonal variations. The groundwater chemical composition of the Rhone alluvial aquifer indicates a mixing of weakly mineralized Rhone River water and SO₄-rich water entering from the south side of the valley. Temporal changes in groundwater chemistry and in groundwater levels reflect the seasonal variations of the different contributors to groundwater recharge. The Rhone River recharges the alluvial aquifer only during the summer high-water period. Electronic Publication     

Fundamentals Of Remote Sensing For Risks Assessment

Remote sensing instruments aboard satellites observe the properties (e.g., intensity) of electromagnetic radiation (e.g., from the Sun) backscattered and/or emitted by the surface. Thus, they record some information about the surface. Different information is obtained in the visible/near infrared, thermal infrared and microwave parts of the spectrum.     

Etude systématique des isotopes de l'oxygène,du carbone et du strontium dans les carbonatites

${}^{18}\text{O}{}^{16}\text{O}$, ${}^{13}\text{C}{}^{12}\text{C}$ and ${}^{87}\text{Sr}{}^{86}\text{Sr}$ ratios have been measured on the same samples for carbonatite complexes. The results show that besides the ‘carbonatite box’ of Tayloret al. (1967) there exist higher δ¹⁸O and δ¹³C values than can be explained by late magmatic or deuteric processes. These processes correspond to high concentrations of CO₂ and lead to big enrichments in ¹⁸O and ¹³C as well as in some ‘volatile’ elements. Strontium results are consistent with a model of selective contamination of deep-seated material by highly radiogenic strontium. The whole study leads to the opinion that parent magmas of carbonatites differentiated in a crustal environment with or without significant contamination.     

Tectonique cassante et champ de contraintes tertiaire en avant des Alpes orientales: le Jura souabe

Résumé La reconnaissance de la fracturation dans le Jura souabe, et son analyse qualitative et quantitative (par traitement informatique) a permis de distinguer cinq épisodes tectoniques cassants, caractérisés successivement par: une distension N-S, des compressions N-S et SW-NE, une distension E-W et une compression ESE-WNW. Ces états de contrainte au sein de la plateforme européenne, en avant de la zone de collision Afrique-Europe, traduisent les mouvements relatifs de ces plaques au cours du Tertiaire.

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Scouting of fracturation in Swabian Jura, and qualitative and quantitative (by informatical treatment) analysis allow to distinguish five breacking tectonic episodes caracterized by: (1) a N-S distension, (2) N-S and (3) NE-SW compressions, (4) a E-W distension and (5) a ESE-WNW compression. These stress fields inside the european platform, in front of collision zone Africa-Europa, attest relative motions of these plates during Tertiary.

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Zusammenfassung Im Schwäbischen Jura lassen die qualitative und die quantitative Aufnahme der Frakturierung sowie ihre EDV-Analyse fünf aufeinander folgende Phasen der tektonischen Beanspruchung (tectonique cassante) erkennen: (1) Zerrung N-S, (2) Kompression N-S und (3) SW-NE, (4) Zerrung E-W, (5) Kompression ESE-WNW. Diese Spannungszustände in der Kollisions-zone von Afrika und Europa vorgelagerten europäischen Plattform geben ein Bild der Relativbewegungen dieser beiden Kontinentalplatten im Tertiär.

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EDV 5 : 1. N-S, 2. N-S 3. SW-NE, 4. E-W, 5. ESE-WNW. .

     

Etude des images Landsat de la zone transformante Rhin-Saône (France)

Résumé L'étude des images Landsat de la zone transformante entre les fossés de la Saône et du Rhin donne un échantillonage significatif de la facturation réparti sur une grande surface, et révèle l'existence de plusieurs linéaments. Ceux-ci sont interprétés comme des accidents profonds délimitant, au Paléogène, un couloir de cisaillement sénestre transformant N 80°, au dessus duquel la couverture se fracture selon un système de Riedel. On reconnait également en surface des failles hercyniennes de direction varisque et des failles »rhénanes« subméridiennes liées à l'ouverture des fossés.

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Landsat imagery of the transform fault zone between the Saône and Rhine grabens indicates a significant fracture pattern distributed over a large area, and reveals many lineaments. These latter are interpreted as basement faults delimiting, during Paleogene time, a N 80° sinistral transform fault zone, above which the cover breaks in series of Riedel shears. Other faults can be recognized on the surface: Hercynian faults of Variscan trend as well as approximately N-trending faults due to the opening of the rifts.

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Zusammenfassung Die Auswertung von Satellitenbildern Landsat der transform fault zone zwischen dem Saône- und dem Rhein-Graben ergibt ein signifikatives Bild der über eine ausgedehnte Oberfläche verteilten Bruchtektonik; es läßt sich daraus auf das Vorhandensein von mehreren Lineamenten schließen. Diese werden als krustale Störungen interpretiert, welche im Paleogen eine enge Scherungszone (senestre, N 80° transform fault zone) begrenzten, deren Bedeckung dem System von Riedel folgend aufbrach. Es lassen sich außerdem an der Oberfläche zwei verschiedene Bruchsysteme erkennen: einerseits herzynische Störungen variskischer Richtung, andererseits die mit der Öffnung des Rheingrabens verbundenen Bruchlinien submeridianer Richtung.

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Surface heterogeneity of mineralsAnalyse de l'hétérogénéité superficielle des minéraux

The precise study of adsorption mechanisms at solid–liquid interfaces requires a good analysis of the surface heterogeneity of the studied solids. For that purpose, molecular probe technique is one of the most powerful, especially at solid–gas interfaces. Indeed, low-pressure gas adsorption coupled to modelling of derivative adsorption isotherms as a function of logarithm of pressure allows to study qualitatively and quantitatively the effect of surface heterogeneity on the energy distribution of adsorption centres. The present review points out the interests of that approach to determine the shape of particles, the presence of high-energy adsorption sites and the surface polarity. Results comparing adsorption at solid–gas and solid–liquid interfaces are also mentioned. To cite this article: F. Villiéras et al., C. R. Geoscience 334 (2002) 597–609.