Gas hydrates at DSDP Leg 84

On DSDP Leg 84, gas hydrates were found at three sites (565, 568, and 570) and were inferred, on the basis of inorganic and organic geochemical evidence, to be present at two sites (566 and 569); no evidence for gas hydrates was observed at Site 567. Recovered gas hydrates appeared as solid pieces of white, icelike material occupying fractures in mudstone or as coarse-grained sediment in which the pore space exhibited rapid outgassing. Also a 1.05-m-long core of massive gas hydrate was obtained at Site 570. Downhole logging indicated that this hydrate was actually 3 to 4 m thick. Measurements of the amount of methane released during the decomposition of these recovered samples clearly showed that gas hydrates had been found. The distribution of evolved hydrocarbon gases indicated that Structure I gas hydrates were present because of the apparent inclusion of methane and ethane and exclusion of propane and higher molecular weight gases. The water composing the gas hydrates was fresh, having chlorinities ranging from 0.5 to 3.2 per mil. At Sites 565, 568, and 570, where gas hydrates were observed, the chlorinity of pore water squeezed from the sediment decreased with sediment depth. The chlorinity profiles may indicate that gas hydrates can often occur finely dispersed in sediments but that these gas hydrates are not recovered because they do not survive the drilling and recovery process. Methane in the gas hydrates found on Leg 84 was mainly derived in situ by biogenic processes, whereas the accompanying small amounts of ethane likely resulted from low-temperature diagenetic processes. Finding gas hydrates on Leg 84 expands observations made earlier on Leg 66 and particularly Leg 67. The results of all of these legs show that gas hydrates are common in landward slope sediments of the Middle American Trench from Mexico to Costa Rica.

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Fil: Gargiulo, Miguel Angel. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Clay mineraology and grain size composition of surface sediments from South Pacific Ocean

The reconstruction of low-latitude ocean-atmosphere interactions is one of the major issues of (paleo-)environmental studies. The trade winds, extending over 20° to 30° of latitude in both hemispheres, between the subtropical highs and the intertropical convergence zone, are major components of the atmospheric circulation and little is known about their long-term variability on geological time-scales, in particular in the Pacific sector. We present the modern spatial pattern of eolian-derived marine sediments in the eastern equatorial and subtropical Pacific (10°N to 25°S) as a reference data set for the interpretation of SE Pacific paleo-dust records. The terrigenous silt and clay fractions of 75 surface sediment samples have been investigated for their grain-size distribution and clay-mineral compositions, respectively, to identify their provenances and transport agents. Dust delivered to the southeast Pacific from the semi- to hyper-arid areas of Peru and Chile is rather fine-grained (4-8 µm) due to low-level transport within the southeast trade winds. Nevertheless, wind is the dominant transport agent and eolian material is the dominant terrigenous component west of the Peru-Chile Trench south of ~ 5°S. Grain-size distributions alone are insufficient to identify the eolian signal in marine sediments due to authigenic particle formation on the sub-oceanic ridges and abundant volcanic glass around the Galapagos Islands. Together with the clay-mineral compositions of the clay fraction, we have identified the dust lobe extending from the coasts of Peru and Chile onto Galapagos Rise as well as across the equator into the doldrums. Illite is a very useful parameter to identify source areas of dust in this smectite-dominated study area.

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Fil: Gargiulo, Miguel Angel. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

La práctica docente incorpora propuestas de la educación en línea

Si bien se ha detectado en la última década un incremento en el uso de computadoras en los colegios, el uso de las mismas como fuente de materiales didácticos ha sido limitado. La formación docente tiene la responsabilidad de incorporar las TICs como herramientas que permiten la alfabetización científica y tecnológica. La presente investigación tiene como objetivo Evaluar el uso de recursos didácticos pensados en TICs1 por parte de los docentes practicantes para su aplicación en las prácticas docentes del Profesorado de Biología. La metodología seleccionada es la de Investigación Acción desarrollándose en distintas Fases. Fase 1:Diagnóstico del grado de información de los Docentes Practicantes sobre Tics. Fase 2: Diseño de recursos didácticos pensados en Tics Fase 3: Ejecución, seguimiento y primeras interpretaciones. Fase 4: Evaluación de la propuesta y formulación de alternativas superadoras La Investigación se lleva a cabo en dos cursos de Biología de 3º año y en uno de Salud y Adolescencia de 1ºaño Polimodal. Para la validación de resultados se emplea el análisis colectivo e interpretación de los resultados, líneas de base y evaluación La originalidad de la suma de las Tics en la práctica docente radica en la manera de concebir la relación profesor alumnos siendo una transición indispensable en los cambios que se avecinan en los procesos de enseñanza aprendizajeSe espera que al finalizar la residencia docente puedan aplicar las nuevas tecnologías que están aprendiendo al mismo tiempo que realicen la evaluación continua constituyendo la misma una retroalimentación constructiva, favoreciendo el desarrollo profesional.

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Fil: Gargiulo, Miguel Angel. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.