El tiempo en un geólogo

Uno de los mayores aportes de la Geología a la cultura universal es haber dado dimensión al tiempo geológico. Se analiza los conceptos de tiempo relativo ytiempo absoluto, y se da cuenta de diversos métodos ideados por lo geólogos para establecer la edad de la Tierra y de las rocas que la conforman. Se discutefinalmente un caso real de determinación de edad de formación de ciertas rocas en Aysén, resaltando algunas de las dificultades que para ello se debe enfrentary resolver.  

Abbot Juan Ignacio Molina: A life devoted to the natural and civil history of Chile

Indexación: Web of Science; ScieloJuan Ignacio Molina (1740-1829) nació cerca de Talca, Chile, y falleció en Bolonia, Italia. Es el primer científico chileno. Desde pequeño se interesó por la naturaleza. Se educó con la Compañía de Jesús en diversos lugares de Chile central, lo que le permitió conocer su geografía, fauna, flora y población. Con 15 años ingresó a la Compañía. En 1767, abandonó el país al ser expulsada esta orden de españa y sus dominios. Se radicó en los Estados Pontificios, donde se ordenó de sacerdote y permaneció hasta su muerte. Allí enseñó ciencias naturales y produjo su obra científica: Compendio de la historia geográfica, natural y civil del reino de Chile de 1776, una versión aumentada, Ensayo sobre la historia natural de Chile de 1782 y una segunda en 1810. En ellas, abordó aspectos climáticos, botánicos, geológicos, zoológicos, mineralógicos y geográficos del territorio. Describió el terremoto de Concepción, las erupciones del Villarrica y Peteroa, e hizo referencia a recursos minerales. Diferenció cuatro unidades litoestratigráficas para Chile central. Clasificó plantas y animales siguiendo los criterios de Linneo. En una de sus 14 memorias, Analogías menos observadas de los tres reinos de la Naturaleza, sin podérselo calificar de evolucionista, se destaca su intento de integración entre los "seres" de los tres reinos, y en Sobre la propagación del género humano en las diversas partes de la tierra, propuso tres vías diferentes para el poblamiento de América. En 1802, ingresó a la Academia de Ciencias de Bolonia.Juan Ignacio Molina (1740-1829), born next to Talca, Chile, and dead in Bologna, Italy, is the first Chilean scientist. His education in establishments of the Society of Jesus, in several localities of central Chile, allowed him to learn about its geography, flora, fauna, and population. At 15 years old he entered the Society. In 1767, he left Chile when the Jesuits were expelled from the spanish territories. In Bologna he produced his scientific contribution. Molina published in 1776 the first of his books, Compendio della storia geográfica, naturale, e civile del regno del Chile. In this one and the others, Molina treated different topics as climatology, botany, geology, zoology, mineralogy, and physical geography. He described his impressions on the Concepción earthquake, the eruptions of the Villarrica and Peteroa volcanoes, and made detailed descriptions of minerals and ore deposits. He differentiated four major lithostratigraphic units. In his descriptions of plants and animals he followed the classification of Linneus. He wrote 14 scientific memoirs. In Analogie meno osservate dei tre regni della Natura, he supports the idea of a gradual transition between all "beings" in the three kingdoms of nature, however, in it he makes no proposition that can be qualified as evolutionary. In Sulla propagazione sucesiva del genere umano he suggests three sources for the population in America. In 1802, he entered the Bolognese Academy of Sciences.http://ref.scielo.org/b3s74

Evolution of the Great Tehuelche Paleolake in the Torres del Paine National Park of Chilean Patagonia during the Last Glacial Maximum and Holocene

Indexación: Web of Science; ScieloRESUMEN. Una serie de morrenas glaciares se distribuyen desde el margen oriental de la cuenca de drenaje Torres del Paine a cerca del actual margen de los Campos de Hielo Patagónico, junto con una serie de terrazas lacustres regional continuos relacionados con las fluctuaciones glaciales. La geomorfología, apoyada por la evidencia de sedimentos del lago, indica la existencia de un único paleolago proglacial en esta zona, aquí denominado el Gran Tehuelche paleolago. Este concepto ayuda a aclarar la cronología de eventos glaciales y conduce a una mejor comprensión de la evolución del sistema hidrológico de la zona de Torres del Paine. Avances glaciales referidos anteriormente como ocurrieron A, B y C durante el Último Máximo Glacial y alimentados con la Gran Tehuelche paleolago con agua de deshielo, que le permite alcanzar su máxima extensión. El descubrimiento de trombolitos en Laguna Amarga sugiere que el drenaje de la paleolago hacia el fiordo de Última Esperanza tuvo lugar en 7113 Cal. años AP, después de la fusión de una barrera de hielo que existía durante el avance glacial antes. Esto dio lugar al desarrollo de un sistema hidrológico fluvio-lacustre complejo que persiste hasta nuestros días. Palabras clave: Patagonia, último máximo glacial, Younger Dryas, trombolitos. RESUMEN. Un grupo de morrenas glaciales estan Distribuidas desde el margen Este de la cuenca de drenaje de Torres del Paine Hacia el margen real de los Campos de Hielo Patagónicos. Las morrenas se observan en conjunto con las Naciones Unidas Grupo de terrazas Lacustres Regionales, las Cuales estan vinculadas y una las fluctuaciones glaciales. La geomorfología y Evidencias de sedimentos Lacustres indicano la existence De unico ONU lago proglacial, referido En Este Estudio de Como Gran Paleolago Tehuelche. Este Concepto ayuda a clarificar la cronología de los eventos glaciales y permite Una mejor Comprensión de la Evolución del Sistema hidrológico del sector de Torres del Paine. Los eventos glaciales, previamente Referidos Como Avance A, B y C, ocurrieron Durante el Último Máximo Glacial y alimentaron con Aguas de fusión al Gran Paleolago Tehuelche, permitiéndole Alcanzar su alcalde extensión. El Descubrimiento de trombolitos en Laguna Amarga sugiere Que El desagüe del paleolago Ocurrió Hace 7.113 Cal. Por años AP el Seno de Última Esperanza, producto de la fusión De Una barrera glaciar existente Durante los Avances glaciales Anteriores. LUEGO del drenaje sí Desarrollo en Un complejo Sistema hidrológico Que Persiste Hasta el presente. Palabras clave: Patagonia, Último Máximo Glacial, Dryas Temprano, Trombolitos.http://ref.scielo.org/wgc2q

Proper motions of young stars in Chamaeleon. I. A Virtual Observatory study of spectroscopically confirmed members

(abridged) We want to provide further evidence of the origin of the proposed stellar members of Chamaeleon and to identify interlopers from the foreground \epsilon Cha and \eta Cha associations. To this aim, we compile lists of spectroscopically confirmed members of Chamaeleon I and II, \epsilon Cha and \eta Cha, and of background objects in the same line of sight. Using Virtual Observatory tools, we cross-match these lists with the UCAC3 catalogue to get the proper motions of the objects. In the vector point diagram, we identify the different moving groups, and use this information to study the membership of proposed candidate members of the associations from the literature. For those objects with available radial velocities, we compute their Galactic space velocities. We look for correlations between the known properties of the objects and their proper motions. The members of the dark clouds exhibit clearly different proper motions from those of the foreground associations and of the background stars. The data suggest that Chamaeleon II could have different dynamical properties from Chamaeleon I. Although the two foreground clusters \epsilon and \eta Chamaeleontis constitute two different proper motion groups, they have similar spatial motions, which are different from the spatial motion of Chamaeleon I. On the other hand, the space motions of the Chamaeleon II stars look more similar to those of the foreground clusters than to the Chamaeleon I stars, but the numbers are low. Hence, with the available data it is unclear to what extent the stellar populations in both clouds are physically connected to each other. We find no correlations between the proper motions and the properties of the objects in either of the clouds

The metamorphic complexes of the Patagonian and Fuegian Andes

The Patagonian and Fuegian Andes are made up in part by late Paleozoic to Mesozoic metamorphic complexes. The mostly low grade late Paleozoic Eastern Andes Metamorphic Complex (EAMC) crops out to the East of the Meso-Cenozoic South Patagonian batholith (SPB), which intruded the metamorphic complexes. The protholit of the EAMC was likely deposited in a passive margin setting and at the Puerto Edén area underwent Late Jurassic sillimanite grade and migmatite local metamorphic conditions. It is suspected, but not proven, that the Cordillera Darwin Metamorphic Complex is a higher grade metamorphic complex equivalent of the EAMC. West of the SPB, paleo subduction complexes occur and are represented by the allochtonous Madre de Dios terrane. This terrane is composed of the ocean floor lithologies of the Denaro Complex topped by the Tarlton limestones that represent a guyot assemblage. The low grade continent derived Duque de York complex was deposited down top of the ocean floor lithologies. Further west, the blueschist bearing Middle Jurassic Diego de Almagro Complex, with psammopelitic, mafic and siliceous volcanic rock protoliths, evolved deep in a subduction zone during the Cretaceous. The possibility that the Antarctic Peninsula was located west of the present margin of South America is discussed

Ultramafic rocks in the North Patagonian Andes: is their emplacement associated with the Neogene tectonics of the Liquiñe–Ofqui Fault Zone?

Serpentinites and fresh or partially serpentinized harzburgite crop out in the western slope of the North Patagonian Andes of continental Chiloé (41°44’-42°12’S). These rocks are spatially associated with low-grade metamorphic rocks containing Cenozoic detrital zircons. The metamorphic rocks, together with Devonian metasediments, have been mapped previously as Late Paleozoic-Triassic metamorfic complex, an age no longer tenable for at least part of the complex. Transpressional tectonic emplacement of the ultramafic body or bodies is thought to have been related to activity on the Liquiñe-Ofqui Fault Zone, following a late Oligocene-Early Miocene extensional phase in the forearc region of the present Andes. This fault zone occurs immediately east of the outcrops of the ultramafic rocks and has been interpreted previously as generating a hemi-flower or flower structure

Magnetoelastic modelling in soft nanocrystalline alloys

Magnetoelastic effects in ultra soft nanocrystalline alloys are investigated theoretically and experimentally. From Hc measurements, extraction of magnetoelastic contribution is carried out using a formalism obtained revisiting random anisotropy model (RAM) in the light of domain walls (DW) displacements, our approach based on theoretical investigations on the way of a reversal of a correlated volume (CV) located in the vicinity of a DW. Modelling of magnetoelastic effects shows that even in perfectly relaxed samples, a magnetoelastic contribution exists due to elastic frustration experienced by a CV during its magnetization reversal. Magnitude of this energy is large enough to drive coercivity of samples featuring grain diameter D around 10 nm, which are of major interest for applications