988 resultados para Sierra Nevada


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13/01/15 Funded by •Faculty of Management at Radboud University Nijmegen

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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

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En este artículo, se analizan los principales cambios que se han dado en un territorio donde se implementó una reforma agraria en los años sesenta del siglo pasado, lo que permitió el acceso a la tierra por parte de los campesinos indígenas y el inicio de un proceso de "territorialización" sobre un importante espacio rural ubicado en el cantón Cayambe, provincia de Pichincha, Ecuador. Interesa sobre todo resaltar la estrategia campesina de ocupación de un territorio de hacienda y su transformación en un territorio de agriculturas familiares campesinas orientadas a la producción de leche y articuladas con las agroindustrias locales. Este proceso ha significado una mayor complejidad del territorio ahora liderado por una dinámica económica externa, lo que ha generado cambios importantes en las estrategias económicas, sociales y culturales de las familias indígenas.

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En este artículo, se analizan los principales cambios que se han dado en un territorio donde se implementó una reforma agraria en los años sesenta del siglo pasado, lo que permitió el acceso a la tierra por parte de los campesinos indígenas y el inicio de un proceso de "territorialización" sobre un importante espacio rural ubicado en el cantón Cayambe, provincia de Pichincha, Ecuador. Interesa sobre todo resaltar la estrategia campesina de ocupación de un territorio de hacienda y su transformación en un territorio de agriculturas familiares campesinas orientadas a la producción de leche y articuladas con las agroindustrias locales. Este proceso ha significado una mayor complejidad del territorio ahora liderado por una dinámica económica externa, lo que ha generado cambios importantes en las estrategias económicas, sociales y culturales de las familias indígenas.

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En este artículo, se analizan los principales cambios que se han dado en un territorio donde se implementó una reforma agraria en los años sesenta del siglo pasado, lo que permitió el acceso a la tierra por parte de los campesinos indígenas y el inicio de un proceso de "territorialización" sobre un importante espacio rural ubicado en el cantón Cayambe, provincia de Pichincha, Ecuador. Interesa sobre todo resaltar la estrategia campesina de ocupación de un territorio de hacienda y su transformación en un territorio de agriculturas familiares campesinas orientadas a la producción de leche y articuladas con las agroindustrias locales. Este proceso ha significado una mayor complejidad del territorio ahora liderado por una dinámica económica externa, lo que ha generado cambios importantes en las estrategias económicas, sociales y culturales de las familias indígenas.

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The magnetic microparticle and nanoparticle inventories of marine sediments from equatorial Atlantic sites were investigated by scanning and transmission electron microscopy to classify all present detrital and authigenic magnetic mineral species and to investigate their regional distribution, origin, transport, and preservation. This information is used to establish source-to-sink relations and to constrain environmental magnetic proxy interpretations for this area. Magnetic extracts were prepared from sediments of three supralysoclinal open ocean gravity cores located at the Ceará Rise (GeoB 1523-1; 3°49.9'N/41°37.3'W), the Mid-Atlantic Ridge (GeoB 4313-2; 4°02.8'N/33°26.3'W), and the Sierra Leone Rise (GeoB 2910-1; 4°50.7'N/21°03.2'W). Sediments from two depths corresponding to marine isotope stages 4 and 5.5 were processed. This selection represents glacial and interglacial conditions of sedimentation for the western, central, and eastern equatorial Atlantic and avoids interferences from subsurface and anoxic processes. Crystallographic, elemental, morphological, and granulometric data of more than 2000 magnetic particles were collected by scanning and transmission electron microscopy. On basis of these properties, nine particle classes could be defined: detrital magnetite, titanomagnetite (fragmental and euhedral), titanomagnetite-hemoilmentite intergrowths, silicates with magnetic inclusions, microcrystalline hematite, magnetite spherules, bacterial magnetite, goethite needles, and nanoparticle clusters. Each class can be associated with fluvial, eolian, subaeric, and submarine volcanic, biogenic, or chemogenic sources. Large-scale sedimentation patterns are delineated as well: detrital magnetite is typical of Amazon discharge, fragmental titanomagnetite is a submarine weathering product of mid-ocean ridge basalts, and titanomagnetite-hemoilmenite intergrowths are common magnetic particles in West African dust. This clear regionalization underlines that magnetic petrology is an excellent indicator of source-to-sink relations. Hematite encrustations, magnetic spherules, and nanoparticle clusters were found at all investigated sites, while bacterial magnetite and authigenic hematite were only detected at the more oxic western site. At the eastern site, surface pits and crevices were seen on the crystal faces indicating subtle early diagenetic reductive dissolution. It was observed that paleoclimatic signatures of magnetogranulometric parameters such as the ratio of anhysteretic and isothermal remanent magnetizations can be formed either by mixing of multiple sources with separate, relatively narrow grain size ranges (western site) or by variable sorting of a single source with a broad grain size distribution (eastern site). Hematite, goethite, and possibly ferrihydrite nanoparticles occur in all sediment cores studied and have either high-coercive or superparamagnetic properties depending on their partly ultrafine grain sizes. These two magnetic fractions are generally discussed as separate fractions, but we suggest that they could actually be genetically linked.

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Several vertebrae of a sauropterygian specimen have been recovered in Fuencaliente de Medinaceli (Soria Province, Castilla y León, Spain). The remains come from Middle–Upper Triassic Muschelkalk Facies. This finding represents the first documented evidence of a Triassic tetrapod in Castilla y León. The vertebrae belong to Nothosaurus, a sauropterygian genus found in Europe, Middle East, North of Africa and China. This genus is poorly-known in the Iberian record. The new remains constitute the first evidence of the species Nothosaurus giganteus, or a related taxon, in the Iberian Peninsula. This study reveals the occurrence of at least two species of the sauropterygian Nothosaurus in the Spanish record.

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A phytosociological study of the forests from Sierra Maestra is conducted, following the methodology of the Zurich- Montpelier School. They are transformed into a forest typology using the standards of the Institute of Agro-Forestry Research. In general, 35 types and/or subtypes are presented. From this group, the most abundant ones belong to semi-deciduous microphyll forest, followed by those from mangroves and mountain rainforest, respectively. Silvicultural treatments are needed; among them, the protection forests are those found above 800 m asl and mangroves. 

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Since its excavation in the summer of 1973, El Niño cave has been considered a key site to understand the process of production economy and pottery technology introduction in South-eastern Iberian Peninsula, and especially to approach how such process could have affected people already settled in the Segura mountains. However, data from El Niño cave was very fragmentary, due to the lack of a broad study of Neolithic occupations of the site. In this paper, we present the analysis of pottery, lithic industry and faunal remains, as well as the existing dates from the site´s Holocene levels. The review of different evidence from the site allows suggesting that El Niño cave would have probably acted as a hunting and shepherding station, being a logistical site of larger places. However, limitations due to the fact that we are dealing with a 40- year-old excavation, prevent specifying how the process of Neolithic introduction in the Segura Mountains occurred.