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

Sedimentología del Mioceno del Vallés occidental (prov. de Barcelona)

In this paper we make a litostratigraphical study on the Miocene of the 'Vallés occidental' (Barcelona, Spain) which embraces a part of the 'Depresion Media' of the intermediary tectonic grave between the 'Cadena Litoral' and 'Prelitoral' of the 'Sistema Mediterráneo'. At the same time we undertake an analysis of the bassin

Interpretación sedimentológica y paleogeográfica del nivel de areniscas eocénicas de Sarrià de Ter (Prov. de Gerona)

There is in this work a description of sedimentological characters of the medium Eocene sandstone level from Sarriá de Ter (Gerona province Spain) and an interpretation of their genesis and situation in the regional paleogeography. The conclusion is that these sandstones form a deltaic channel(delta front). To wards the E and NE the become fluvial deposits, to wards the W, Plana de Vic, they become clay and silstones considered as a prodelta

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

El Patrimoni geològic de les terres gironines

Lluís Pallí i Carles Roqué acaben de publicar "El patrimoni geològic de les terres gironines: 300 elements singulars". El llibre, editat per la Universitat de Girona, amb el suport de la Diputació, recull una dedicació de més de quaranta anys a les recerques geològiques a través del territori gironí

Previsió d'impactes en el medi físic, derivats de l'explotació de les formacions geològiques d'interés per a la producció d'àrids, a la zona del curs mitjà del Riu Fluvià (La Garrotxa)

Potential mining of the pliocene and quaternary geological formations for the aggregate production along the medium course of the Fluvil river is likely to be carried out through gravel pits. The most significant environmental impacts are envisaged to occur during site preparation and extraction of aggregate. Several environmental impacts types have been considered: variation of water table, reduction of soil and vegetation, development of unbalanced land-forms and deterioration of landscape

Un model de guia didàctica [Ressenya del llibre Itinerari geològic de Banyoles : descoberta del funcionament del sistema lacustre, de David Brusi , Joan Bach i Miquel Sanz]

Ressenya del llibre 'Itinerari geològic de Banyoles : descoberta del funcionament del sistema lacustre' de David Brusi, Joan Bach i Miquel Sanz, editat per l' Ajuntament de Banyoles i Eumo Editorial l'any 1990

El sistema cárstico de Sant Martí de Llémena

Descripció del sistema càrstic de Sant Martí de Llémena

Significado sedimentológico de los niveles con Assilinas de la Formación Armancies (Eoceno medio) y sus equivalentes laterales

In this paper we show some sedimentological characteristics of Assilina beds from Armancies Fm. (middle Eocene) and their lateral equivalents that let us to remark some aspects of their genesis. We arrive to the conclusion that, in occidental sector (Bagá-Campdevanol), ‘las barras de Assilinas’ from the Armancies Fm. are grain flow channels, first sedimented at W of Terrades and after slided, from E to W in a turbidite basin, without any coarse clastic

Métodos de reconocimiento del subsuelo

The aim of this workshop is to present the main methods of subsoil studies (namely mechanical and geophysical methods) to the Earth Sciences professorate. These methods frequently involve the use of specific material. The different methods are usually taught in the classroom where there is no real contact between the students and the equipment. Several activities, all of them taking place in surrounding areas of the university campus of Girona, will provide the assistants to the workshop with the opportunity of making measurements with different equipment. These activities will be made in the field so as to contribute to the resolution of a problem which will have been previously proposed. The problems presented are situations, most of them real, when subsoil investigation techniques are usually used. These cases have been employed as teaching-learning strategies with university and second grade students in the area of Girona. Finally, some examples of exercises involving the treatment of data obtained through subsoil investigation techniques are also presented to complement the workshop

La zona lacustre de Banyoles (Girona, España)

Descripció de la zona lacustre de Banyoles des del punt de vista geològic i hidrogeologic

Oscil.lacions del nivell del mar i sediments associats durant l'Holocè a la Costa Brava Meridional (Girona)

Several marine deposits in the southern Costa Brava shoreline have been studied. They appear at different heights above and below the present sea level. Three groups are defined in relation to their origin: conglomerate levels at the bottom of the cliffs, not-cemented emerged beaches and cemented submerged beaches. The age of the emerged beaches has been accurately determined by means of the ceramic content and radiocarbon dating. Chronological succession of the deposits and their stratigraphic and paleontological characteristics allow to define a sequence of the sea level changes during the latest stages of the versiliane transgression in the studied area

Estudi i propostes de gestió de les zones humides dels Estanys de Basturs

Estudi del medi abiòtic i biòtic dels estanys de Basturs (Conca del riu Tremp) a partir del qual s'han elaborat diverses propostes de gestió dirigides a una millora de la conservació les zones humides

Interactions between grain size and composition of sediments: two examples

Two contrasting case studies of sediment and detrital mineral composition are investigated in order to outline interactions between chemical composition and grain size. Modern glacial sediments exhibit a strong dependence of the two parameters due to the preferential enrichment of mafic minerals, especially biotite, in the fine-grained fractions. On the other hand, the composition of detrital heavy minerals (here: rutile) appears to be not systematically related to grain-size, but is strongly controlled by location, i.e. the petrology of the source rocks of detrital grains. This supports the use of rutile as a well-suited tracer mineral for provenance studies. The results further suggest that (i) interpretations derived from whole-rock sediment geochemistry should be flanked by grain-size observations, and (ii) a more sound statistical evaluation of these interactions require the development of new tailor-made statistical tools to deal with such so-called two-way compositions

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