Geochemistry, clay mineralogy and grain size distribution in various sediment cores drilled during ODP Leg 119 on the Antarctic continental shelf off Prydz Bay

Drilling was undertaken at five sites (739-743) on ODP Leg 119 on a transect across the continental shelf of Prydz Bay, East Antarctica, to elucidate the long-term glacial history of the area and to examine the importance of the area with respect to the development of the East Antarctic ice sheet as a whole. In addition to providing a record of glaciation spanning 36 m.y. or more, Leg 119 has provided information concerning the development of a continental margin under the prolonged influence of a major ice sheet. This has allowed the development of a sedimentary model that may be applicable not only to other parts of the Antarctic continental margin, but also to northern high-latitude continental shelves. The cored glacial sedimentary record in Prydz Bay consists of three major sequences, dominated by diamictite: 1. An upper flat-lying sequence that ranges in thickness from a few meters in inner and western Prydz Bay to nearly 250 m in the outer or eastern parts of the bay. The uppermost few meters consist of Holocene diatom ooze and diatomaceous mud with a minor ice-rafted component overlying diamicton and diamictite of late Miocene to Quaternary age. The diamictite is mainly massive, but stratified varieties and minor mudstone and diatomite also occur. 2. An upper prograding sequence cored at Sites 739 and 743, unconformly below the flat-lying sequence. This consists of a relatively steep (4° inclination) prograding wedge with a number of discrete sedimentary packages. At Sites 739 and 743 the sequence is dominated by massive and stratified diamictite, some of which shows evidence of slumping and minor debris flowage. 3. A lower, more gently inclined, prograding sequence lies unconformably below the flat-lying sequence at Site 742 and the upper prograding sequence at Site 739. This extends to the base of both sites, to 316 and 487 mbsf, respectively. It is dominated by massive, relatively clast-poor diamictite which is kaolinite-rich, light in color, and contains sporadic carbonate-cemented layers. The lower part of Site 742 includes well-stratified diamictites and very poorly sorted mudstones. The base of this site has indications of large-scale soft-sediment deformation and probably represents proximity to the base of the glacial sequence. Facies analysis of the Prydz Bay glacial sequence indicates a range of depositional environments. Massive diamictite is interpreted largely as waterlain till, deposited close to the grounding line of a floating glacier margin, although basal till and debris flow facies are also present. Weakly stratified diamictite is interpreted as having formed close to or under the floating ice margin and influenced by the input of marine diatomaceous sediment (proximal glaciomarine setting). Well-stratified diamictite has a stronger marine input, being more diatom-rich, and probably represents a proximal-distal glaciomarine sediment with the glaciogenic component being supplied by icebergs. Other facies include a variety of mudstones and diatom-rich sediments of marine origin, in which an ice-rafted component is still significant. None of the recovered sediments are devoid of a glacial influence. The overall depositional setting of the prograding sequence is one in which the grounded ice margin is situated close to the shelf edge. Progradation was achieved primarily by deposition of waterlain till. The flat-lying sequence illustrates a complex sequence of advances and retreats across the outer part of the shelf, with intermittent phases of ice loading and erosion. The glacial chronology is based largely on diatom stratigraphy, which has limited resolution. It appears that ice reached the paleoshelf break by earliest Oligocene, suggesting full-scale development of the East Antarctic ice sheet by that time. The ice sheet probably dominated the continental margin for much of Oligocene to middle Miocene time. Retreat, but not total withdrawal of the ice sheet, took place in late Miocene to mid-Pliocene time. The late Pliocene to Pleistocene was characterized by further advances across, and progradation of, the continental shelf. Holocene time has been characterized by reduced glacial conditions and a limited influence of glacial processes on sedimentation.

(Table 2) Chemical composition of ice-rafted brecciated crystalline schist and biotite-garnet crystalline schist from the Kara Sea

Composition and distribution.of ice-rafted coarse debris from the Kara Sea bottom were investigated. This material was obtained on 42 stations in Cruise 49 of R/V Dmitry Mendeleev by Sigsby trawls, box corers, grabs, and gravity corers. Existence of two main petrographic provinces is suggested: (1) West Kara and (2) East Kara. They differ in composition and sources of debris material. It is supposed that debris was transported mainly by floating ice. In Upper Pleistocene time rafting by glaciers and icebergs was also very possible.

Disputa de Proyectos en Ecuador : El Hecho Social del 30 de Septiembre de 2010

El hecho social estudiado en este trabajo es lo ocurrido el 30 de Septiembre del año 2010 en Ecuador, cuando un sector de las fuerzas armadas y de la policía realizan una protesta en contra de la Ley de Servicio Público. Esta protesta fue acompañada, entre otras, por un conjunto de acciones que incluyeron la retención del presidente Rafael Correa por más de 10 horas en el hospital policial, distintos hechos delictivos en varios puntos del país, la toma del Aeropuerto de Quito, el intento de tomar los medios de comunicación públicos. Ante esto, se produjo una importante y rápida repercusión a nivel internacional y especialmente desde Latinoamérica. A lo largo del trabajo, se analizará cómo intervienen y se posicionan ante el hecho distintos actores nacionales e internacionales, políticos, sociales, culturales y económicos, lo cual permitirá reconstruir los intereses en juego, la disputa de proyectos y los conflictos de intereses latentes no sólo en Ecuador, sino en toda la región Latinoamérica. El análisis que se realiza en este trabajo se hace a partir de la construcción de una base de datos de medios gráficos argentinos (Clarín, La Nación, Página 12, Perfil), ecuatorianos (Diario Hoy, Diario Popular, El Universo, El Telégrafo) y latinoamericanos como Telesur y con un marco teórico desarrollado a partir de la bibliografía. Desde los Medios Masivos de Comunicación, así como distintos actores, fueron considerando lo ocurrido como una sublevación policial, un intento de golpe de estado o un autogolpe. Esto es lo que se reconstruirá a lo largo del trabajo

Forasteros y migrantes. Un acercamiento a la construcción de la trama social en la ciudad de San Miguel de Tucumán en las últimas décadas coloniales

El crecimiento de los sectores populares urbanos hacia fines del siglo XVIII y comienzos del XIX, quizás haya sido uno de los fenómenos demográficos más significativos y que ha producido más rupturas en la organización social corporativa y jerárquica de Antiguo Régimen. Recién cuando la ciudad creció y adquirió características de urbe (que no eran sinónimos), pudo hablarse de la presencia de un grupo social que no pertenecía a la corporación de vecinos y que incluso se oponía a ésta. El tema que se plantea en este trabajo es la construcción de la trama social urbana en San Miguel de Tucumán en las postrimerías coloniales. En este contexto, problematizamos la situación de forasteros y migrantes como un problema para las autoridades en torno a su ubicación social y su control. La hipótesis que planteamos es que la definición de "forastero en la ciudad" aplicada por las autoridades, estaba dirigida a los migrantes "de baja esfera", es decir, a quienes no eran reconocidos por los vecinos como pares. Progresivamente, la referencia de identificación utilizada fue la patria: el lugar de origen. Cada vez era más frecuente la expresión "natural deÔǪ" como única referencia de identidad, más allá de las señas personales.