Caracterización morfológica, textural y composicional de las partículas de oro reveladas en placeres marinos de las playas Mejías y Jiguaní (NE de Cuba Oriental)

En este trabajo se describen los principales rasgos morfológicos, texturales y composicionales de las partículas de oro presentes en los placeres marinos costeros de las playas Mejías y Jiguaní, Cuba. Las partículas de oro estudiadas en ambos depósitos, son muy finas, mostrando formas tabulares predominantes; en ocasiones aparecen muy aplastadas, formando especies de laminillas o hojuelas, observándose, a través de las imágenes de electrones etrodispersados,partículas con texturas internas muy complejas , así como cariado de los granos. Las partículas están compuestas por subgranos de composición diferente,correspondientes a aleaciones naturales de Electrum, oro nativo y oro mercurial en ambos placeres y aleaciones de Au-Cu (tetraauricuprido) en el Placer Jiguaní. Estos subgranos frecuentemente se encuentran alterados en sus bordes. Esta alteración consiste predominantemente en un enriquecimiento en oro con relación a la plata.

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Diseño experimental y análisis de datos

Capítol 22 del llibre 'Conceptos y técnicas en ecología fluvial' que es refereix a la importància del disseny experimental i de l'anàlisi estadística en la investigació ecològica

Aplicació de tècniques geofísiques electromagnètiques a la localització de zones afectades per abocaments incontrolats de residus

Increase of the metropolitan area of cities provoking a progressive settlement of zones that previously had a different territorial use. These zones are usually located within city houndaries and for many years have been affected hy the waste of many kinds of residues. Qualitative analysis of the electrical behaviour of soil, based on maps and cross sections of apparent conductivity, allows us to locate anomalies generated by the wastes. Moreover, the electrornagnetic techniques (EM-31 and EM-34 Geonics devices) are cheaper than other survey methods. Two examples in the campus of the University of Girona, in the southern area of Girona city, illustrate the environmental problem and the applicability of the geophysical method

Caracterització arqueològica i geològica de les produccions de rajoleria d’època romana de Llafranc (Baix Empordà)

Descripció de diferents materials ceràmics d'època romana trobats a Llafranc

First record of the common bream (Abramis brama) introduced to the Iberian Peninsula

This is the first record of the common bream, Abramis brama (Linnaeus, 1758), introduced into the Iberian Peninsula. Eight individuals of this cyprinid fish species were captured (of a total of 978 fish) in the Boadella Reservoir (Catalonia, Spain) on August 18, 2004. This reservoir is only 14 km away from France, where the bream is native, and contains several exotic freshwater fish that are still not widespread in Spain. The further introduction of species and the illegal translocation of the bream by anglers to other Iberian river basins should be controlled by the Spanish administration

Experimental assessment of the effects of a Neotropical nocturnal piscivore on juvenile native and invasive fishes

We experimentally examined the predator-prey relationships between juvenile spotted sorubim Pseudoplastystoma corruscans and young-of-the-year invasive and native fish species of the Paraná River basin, Brazil. Three invasive (peacock bass Cichla piquiti, Nile tilapia Oreochromis niloticus, and channel catfish Ictalurus punctatus) and two native (yellowtail tetra Astyanax altiparanae and streaked prochilod Prochilodus lineatus) fish species were offered as prey to P. corruscans in 300 L aquaria with three habitat complexity treatments (0%, 50% and 100% structure-covered). Prey survival was variable through time and among species (C. piquiti < O. niloticus < A. altiparanae < P. lineatus < I. punctatus), depending largely on species-specific prey behavior but also on prey size and morphological defenses. Habitat complexity did not directly affect P. corruscans piscivory but some prey species changed their microhabitat use and shoaling behavior among habitat treatments in predator’s presence. Pseudoplatystoma corruscans preyed preferentially on smaller individuals of those invasive species with weak morphological defensive features that persisted in a non-shoaling behavior. Overall, our results contrast with those in a companion experiment using a diurnal predator, suggesting that nocturnal piscivores preferentially prey on different (rather diurnal) fish species and are less affected by habitat complexity. Our findings suggest that recovering the native populations of P. corruscans might help controling some fish species introduced to the Paraná River basin, particularly C. piquiti and O. niloticus, whose parental care is expected to be weak or null at night

Els esfondraments per carstificació al terme municipal de Besalú

En aquest treball s'analitzen les característiques generals i particulars dels esfondraments per carstificació que esprodueixen al terme municipal de Besalú, i s'examinen les diferents dades que permeten establir una primera aproximació cartogràfica del perill existent

Geologic maps published by university de Girona's unity of geodynamics

In 1978 University de Girona's Unity of Geodynamics started publishing geological maps, in several themes and scales, of various areas of the Province of Girona (fig. 1). So far, up to 38 maps, gathered in several collections, have been published

Geomorphological mapping of granite zones in the province of Girona (Catalunya, Spain)

Since 1978, the unity of Geodynamics of the University of Girona has been publishing a series of detailed geological and geomorphological maps of different municipal terms of the Province of Girona, mainly on the scale of 1:10.000, situated for the major part in the Littoral and Prelittoral mountain ranges of the Cadena Costera Catalana. These mountain ranges are constituted of materials belonging to the palaeozoic era, basically metamorphous and igneous rocks (plutomc and hypoabyssal rocks)

Aportación al estudio de arcillas expansivas asociadas a las facies garumnienses de la Conca de Tremp (Prepirineo de Lleida)

Some clay levels of the garumnian facies, which surface in the southern sector of the Tremp Basin present a principal mineralogy of expansive type. The oedometer essays show that such materials present a very high grade of potencial expansivity. The swelling pressure presents values higher than 390 KN/m2. In the majority of the areas wherw this kind of clays surface the hydric erosion phenomena and the mass movements often appear to be very common and intense. The geomorphological role of the expansive clays is discussed as the triggering factor, associated to the development of these denudative processes

Formas graníticas asociadas a megalitos en el nordeste de Cataluña

The landforms that appears in granite slabs of the megaliths, that localize in the NW part of Catalonia, had studied for quantify their increase values. The results allow of distinguish between pre and postmegalithical landforms. Some premegalithical gnammas are 5000 years old or more and has developed actually. Had been calculate 1cm/1000 yaers deepening rates for gnammas and between 0,4 and 3 com/1000 years for the alveoles according to postmegalithical ladforms sizes. The size cannot be used for age approach in another postmegalithical landforms (pitting, ‘pseudorejones’ and speleothems)

Impacto ambiental previsto en la explotación de gravas en la zona de concurso medio del riu Fluvià (Girona)

The main environmental impacts related to the gravel pits in the medium course of the Fluvià river have been assessed. In order to compute the global impact and index based on the numerical values of different impacts has been defined. This index is applied to different areas and the results reveal that the environmental impact expected for a gravel pit is high or moderate close to the main streams and low in the rest of the territory