Presencia del paleogeno bajo los sedimentos neogénicos de Vilablareix (Girona)

This study makes clear the existence of a paleogenical red basal level (Pontils Fm.) in the Vilablareix àrea, under the mio-pliocenical cover of the Girona plain, enlargening the surface known go far of that level

La Geologia al servei de la societat

S’acaba de commemorar l’Any Internacional del Planeta Terra, en el marc de la celebració reivindicativa de les Nacions Unides. L’objectiu d’aquesta iniciativa és incrementar la conscienciació dels ciutadans i de la classe política sobre l’aportació de les ciències de la terra a la millora de la qualitat de vida i la salvaguarda del nostre planeta

La Intrusió salina a Sant Antoni de Calonge: la geologia al servei de la gestió territorial

L’extracció intensiva d’aigua subterrània en zones properes a la costa pot produir canvis en les condicions hidrogeològiques naturals dels aqüífers costaners. Les conseqüències més evidents d’aquest fenomen són el descens del nivell freàtic, la intrusió salina i els riscos geotècnics que se’n deriven i que poden afectar l’estabilitat de les edificacions que hi ha a la zona. Per encàrrec de l’Ajuntament de Calonge, el centre GEOCAMB de la UdG ha fet un estudi sobre aquest problema en el seu terme municipal

Geologia del Baix Ter

Article que analitza el valor i la singularitat de les zones humides del Baix Ter, tenint en compte la descripció de les característiques geològiques de la Plana del Ter i dels diferents ambients morfodinàmics que s' hi troben

Ciències de la terra i societat : la recerca en geologia aplicada

Aquest article pretén presentar les línies de treball del grup de recerca de l'Àrea de Geodinàmica Externa del Departament de Ciències Ambientals de la Facultat de Ciències de la UdG (Universitat de Girona)com a mostra dels camps d'aplicació més comuns del treball dels geòlegs

El Geocamp: un portal informàtic interuniversitari i una eina d'autoedició per les activitats de camp en geologia

GEOCAMP(http://einstein.uab.es/_c_gr_geocamp/geocamp) és una proposta d'innovació educativa desenvolupada per un equip de professors universitaris vinculats a tres universitats catalanes (UdG, UAB i UPC). GEOCAMP és un portal d'Internet que engloba material docent desenvolupat específicament per optimitzar el procés d'aprenentatge en les activitats de camp de Geologia. El GEOCAMP ha estat emprat abastament per estudiants de les universitats en les quals l'equip d'autors imparteix docència. La seva potencialitat i lliure disposició ha permès que el seu ús es generalitzi a d'altres centres i nivells educatius tant a la resta de l'estat com a l'estranger

El Holoceno medio palustre de la llanura litoral del río Ter (Baix Empordá, Girona)

The paludal deposits presented here belong to a geomorphological unit identified between Palafrugell Corridor and the littoral plains of Ter River (Baix Ter), associated to a carbonate-rich spring system. The sections show a distintic clay level, mixed with black silts, very rich in snail remains. The malacological assemblage contained stillwaters species (Bithynia leachii, Galba truncatula, Pisidium milium, Radix peregra) along with damp species (Monacha cartusiana, Oxyloma elegans, Succinea putris, Succinella oblonga, Vallonia pulchella, Vertigo sp.). Some open-dry species are also present (Cernuella virgata, Eobania vermiculata, Pomatias elegans, Rumina decollata) revailing a mosaic-like landscape. Radiocarbon dates place this level ca. 7.000BPwithin the Holocene sequence of the Baix Ter basin. Colluvial deposits on top of these paludal levels have a typical open-dry malacological assemblage (Cernuella virgata, Cochlicella acuta, Eobania vermiculata, Pomatias elegans, Rumina decollata, Trochoidea elegans) the same assemblage that inhabits the Empordà littoral plains nowadays

Kriging coordinates: what does that mean?

Kriging is an interpolation technique whose optimality criteria are based on normality assumptions either for observed or for transformed data. This is the case of normal, lognormal and multigaussian kriging. When kriging is applied to transformed scores, optimality of obtained estimators becomes a cumbersome concept: back-transformed optimal interpolations in transformed scores are not optimal in the original sample space, and vice-versa. This lack of compatible criteria of optimality induces a variety of problems in both point and block estimates. For instance, lognormal kriging, widely used to interpolate positive variables, has no straightforward way to build consistent and optimal confidence intervals for estimates. These problems are ultimately linked to the assumed space structure of the data support: for instance, positive values, when modelled with lognormal distributions, are assumed to be embedded in the whole real space, with the usual real space structure and Lebesgue measure

Major-elements trends in cenozoic volcanites of Hungary

Hungary lies entirely within the Carpatho-Pannonian Region (CPR), a dominant tectonic unit of eastern Central Europe. The CPR consists of the Pannonian Basin system, and the arc of the Carpathian Mountains surrounding the lowlands in the north, east, and southeast. In the west, the CPR is bounded by the Eastern Alps, whereas in the south, by the Dinaridic belt. (...)

A Log-linear model of grain size influence on the geochemistry of sediments

Sediment composition is mainly controlled by the nature of the source rock(s), and chemical (weathering) and physical processes (mechanical crushing, abrasion, hydrodynamic sorting) during alteration and transport. Although the factors controlling these processes are conceptually well understood, detailed quantification of compositional changes induced by a single process are rare, as are examples where the effects of several processes can be distinguished. The present study was designed to characterize the role of mechanical crushing and sorting in the absence of chemical weathering. Twenty sediment samples were taken from Alpine glaciers that erode almost pure granitoid lithologies. For each sample, 11 grain-size fractions from granules to clay (ø grades <-1 to >9) were separated, and each fraction was analysed for its chemical composition. The presence of clear steps in the box-plots of all parts (in adequate ilr and clr scales) against ø is assumed to be explained by typical crystal size ranges for the relevant mineral phases. These scatter plots and the biplot suggest a splitting of the full grain size range into three groups: coarser than ø=4 (comparatively rich in SiO2, Na2O, K2O, Al2O3, and dominated by “felsic” minerals like quartz and feldspar), finer than ø=8 (comparatively rich in TiO2, MnO, MgO, Fe2O3, mostly related to “mafic” sheet silicates like biotite and chlorite), and intermediate grains sizes (4≤ø <8; comparatively rich in P2O5 and CaO, related to apatite, some feldspar). To further test the absence of chemical weathering, the observed compositions were regressed against three explanatory variables: a trend on grain size in ø scale, a step function for ø≥4, and another for ø≥8. The original hypothesis was that the trend could be identified with weathering effects, whereas each step function would highlight those minerals with biggest characteristic size at its lower end. Results suggest that this assumption is reasonable for the step function, but that besides weathering some other factors (different mechanical behavior of minerals) have also an important contribution to the trend. Key words: sediment, geochemistry, grain size, regression, step function

An alternative method for dating unknown tephras based on a segmented regression model

In CoDaWork’05, we presented an application of discriminant function analysis (DFA) to 4 different compositional datasets and modelled the first canonical variable using a segmented regression model solely based on an observation about the scatter plots. In this paper, multiple linear regressions are applied to different datasets to confirm the validity of our proposed model. In addition to dating the unknown tephras by calibration as discussed previously, another method of mapping the unknown tephras into samples of the reference set or missing samples in between consecutive reference samples is proposed. The application of these methodologies is demonstrated with both simulated and real datasets. This new proposed methodology provides an alternative, more acceptable approach for geologists as their focus is on mapping the unknown tephra with relevant eruptive events rather than estimating the age of unknown tephra. Kew words: Tephrochronology; Segmented regression