Tufa sedimentation in changing hydrological conditions : the River Mesa (Spain)

The processes controlling tufa deposition along the River Mesa (NE Spain) were studied from April 2003 to September 2009, based on six-monthly monitoring of physical and chemical parameters of the river water and sedimentological characteristics, including deposition rates on tablets. With a mean annual discharge around 1.5m3 /s, the sedimentation rate (mean 2mm/yr) recorded important spatial, seasonal and interannual variations. The river waters are of the calcium bicarbonate type. In this study, three distinct river stretches were distinguished based on the steady groundwater inputs, some of low-thermal nature. Groundwater discharges controlled the water chemical composition, and some sedimentation features too. At each stretch, an increase in pCO2 and conductivity was measured around the spring sites. Decreasing trends in conductivity or alkalinity with high enough saturation values with respect to calcite were only clearly observed in the intermediate stretch, which had higher tufa deposition rates than the other two. Tufa deposition rates were higher in cool (autumn+winter) than in warm (spring+summer) periods. In some low-rainfall warm periods, tufa deposition was inhibited or limited due to the low flow -mainly from groundwater inputs- and to the dryness of some river sites, which indeed favoured erosion during flooding. A decrease in yearly deposition rates from April 2006 onwards paralleled an important reduction in the river discharge. Groundwater inputs, drought periods and flood events should therefore be considered to understand fluvial tufa sedimentation in semi-arid conditions

Utilización de diseños ornamentales en la enseñanza de la Cristalografía

El análisis de modelos periódicos y simétricos de una y dos dimensiones puede servir de introducción al estudio de las propiedades de la periodicidad y simetría de la estructura tridimensional de los cristales. En este trabajo se propone un esquema de análisis de dichos desafíos, sobre los que se van descubriendo progresivamente los distintos conceptos relacionados con este tema. Para la asignación al desafío del grupo espacial correspondiente de una o dos dimensiones se proponen sendos diagramas. Los desafíos que se ofrecen se han tomado de motivos ornamentales de uso cotidiano, para aprovechar los conceptos intuitivos de periodicidad y simetría.The analysis of periodic and symmetric patterns in one or two dimensions can be used as an introduction to the study of periodicity and symmetry in the three-dimensional structure of crystals. In the present paper a scheme to analyse such patterns is proposed: the notions related with periodicity and symmetry are graduall y discovered through the pattern. Two diagrams are proposed to correlate every pattern with its own spatial group (in one or two dimensions). The patterns presented in t he paper have been taken from ornamental designs of common use, in order to take advantage of the intuitive knowledge of periodicity and symmetry

Utilización de diseños ornamentales en la enseñanza de la Cristalografía

El análisis de modelos periódicos y simétricos de una y dos dimensiones puede servir de introducción al estudio de las propiedades de la periodicidad y simetría de la estructura tridimensional de los cristales. En este trabajo se propone un esquema de análisis de dichos desafíos, sobre los que se van descubriendo progresivamente los distintos conceptos relacionados con este tema. Para la asignación al desafío del grupo espacial correspondiente de una o dos dimensiones se proponen sendos diagramas. Los desafíos que se ofrecen se han tomado de motivos ornamentales de uso cotidiano, para aprovechar los conceptos intuitivos de periodicidad y simetría.The analysis of periodic and symmetric patterns in one or two dimensions can be used as an introduction to the study of periodicity and symmetry in the three-dimensional structure of crystals. In the present paper a scheme to analyse such patterns is proposed: the notions related with periodicity and symmetry are graduall y discovered through the pattern. Two diagrams are proposed to correlate every pattern with its own spatial group (in one or two dimensions). The patterns presented in t he paper have been taken from ornamental designs of common use, in order to take advantage of the intuitive knowledge of periodicity and symmetry

Tufa sedimentation in changing hydrological conditions : the River Mesa (Spain)

The processes controlling tufa deposition along the River Mesa (NE Spain) were studied from April 2003 to September 2009, based on six-monthly monitoring of physical and chemical parameters of the river water and sedimentological characteristics, including deposition rates on tablets. With a mean annual discharge around 1.5m3 /s, the sedimentation rate (mean 2mm/yr) recorded important spatial, seasonal and interannual variations. The river waters are of the calcium bicarbonate type. In this study, three distinct river stretches were distinguished based on the steady groundwater inputs, some of low-thermal nature. Groundwater discharges controlled the water chemical composition, and some sedimentation features too. At each stretch, an increase in pCO2 and conductivity was measured around the spring sites. Decreasing trends in conductivity or alkalinity with high enough saturation values with respect to calcite were only clearly observed in the intermediate stretch, which had higher tufa deposition rates than the other two. Tufa deposition rates were higher in cool (autumn+winter) than in warm (spring+summer) periods. In some low-rainfall warm periods, tufa deposition was inhibited or limited due to the low flow -mainly from groundwater inputs- and to the dryness of some river sites, which indeed favoured erosion during flooding. A decrease in yearly deposition rates from April 2006 onwards paralleled an important reduction in the river discharge. Groundwater inputs, drought periods and flood events should therefore be considered to understand fluvial tufa sedimentation in semi-arid conditions

Tufa sedimentation in changing hydrological conditions: the River Mesa (Spain)

The processes controlling tufa deposition along the River Mesa (NE Spain) were studied from April 2003 to September 2009, based on six-monthly monitoring of physical and chemical parameters of the river water and sedimentological characteristics, including deposition rates on tablets. With a mean annual discharge around 1.5m3 /s, the sedimentation rate (mean 2mm/yr) recorded important spatial, seasonal and interannual variations. The river waters are of the calcium bicarbonate type. In this study, three distinct river stretches were distinguished based on the steady groundwater inputs, some of low-thermal nature. Groundwater discharges controlled the water chemical composition, and some sedimentation features too. At each stretch, an increase in pCO2 and conductivity was measured around the spring sites. Decreasing trends in conductivity or alkalinity with high enough saturation values with respect to calcite were only clearly observed in the intermediate stretch, which had higher tufa deposition rates than the other two. Tufa deposition rates were higher in cool (autumn+winter) than in warm (spring+summer) periods. In some low-rainfall warm periods, tufa deposition was inhibited or limited due to the low flow �mainly from groundwater inputs� and to the dryness of some river sites, which indeed favoured erosion during flooding. A decrease in yearly deposition rates from April 2006 onwards paralleled an important reduction in the river discharge. Groundwater inputs, drought periods and flood events should therefore be considered to understand fluvial tufa sedimentation in semi-arid condition

Composición determinada por XRF de un conjunto de altar dorado y esmaltado de la catedral de Huesca

El presente artículo estudia, desde el punto de vista interdisciplinar y a partir de un análisis realizado con un equipo portátil de fluorescencia de rayos X, un conjunto de altar dorado y esmaltado de la catedral de Huesca de comienzos de la Edad Contemporánea. Los análisis revelan que existe homogeneidad en su composición química: el conjunto presenta mayoritariamente oro junto a cantidades menores de cobre y plata e incluye además trazas de mercurio sin variaciones significativas entre los distintos puntos analizados. Sin embargo, el peso del cáliz, como objeto principal, es similar al de otro de plata dorada de dimensiones parecidas, lo que resulta incompatible con una composición de oro puro, por lo que se propone la hipótesis de que todas las jocalias tengan un dorado de extraordinario grosor, probablemente de varias decenas de micras

Geomorphological study of the Cafayate dune field (Northwest Argentina) during the last millennium

The Cafayate depression is a dry valley located in the Pre-Andean region of northwest Argentina. The area shows the development of a large dune field. Its significance has been established from geomorphological and mineralogical evidence, grain shape characteristics and chronological data (OSL dating, archaeological remains, and historical data). The dating results were between 1000–1100 AD to1740–1830 AD showing that the aeolian dynamics remained active during the last millennium. It was not possible to identify stabilised phases marked by ruptures or paleosol development. Nevertheless, other regional and local proxies from Northwest Argentina (archaeological, documentary, etc.) were used to complete the interpretative framework to propose the paleoenvironmental evolution of the area. In addition, human activity and land use must be considered as a complementary factor affecting aeolian dynamics during the most recent stage.Fil: Peña Monné, José Luis. Universidad de Zaragoza; EspañaFil: Sancho Marcén, Carlos. Universidad de Zaragoza; EspañaFil: Sampietro Vattuone, Maria Marta. Universidad Nacional de Tucuman. Facultad de Cs.naturales E Instituto Miguel Lillo. Laboratorio de Geoarqueologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rivelli, Felipe. Universidad Nacional de Salta. Facultad de Ciencias Naturales; ArgentinaFil: Rhodes, Edwards J.. University of California at Los Angeles; Estados Unidos. University Of Manchester; Reino UnidoFil: Osácar Soriano, María Cinta. Universidad de Zaragoza; EspañaFil: Rubio Fernández, Virginia. Universidad Autónoma de Madrid; EspañaFil: García Giménez, Rosario. Universidad Autónoma de Madrid; Españ

Geomorphology and environmental changes in the Cafayate depression (province of Salta, Northwest Argentina)

La depresión de Cafayate es un buen ejemplo de cuenca árida pre-andina del Noroeste de Argentina. Comprende el valle del Río Santa María en su sector de confluencia con el Río Calchaquí y presenta un amplio repertorio geomorfológico (depósitos fluviales, conos aluviales, depósitos lacustres, campos de dunas) que aporta importante información sobre la evolución holocena y, de forma especial, para los últimos mil años. En esta oportunidad, se dedica mayor atención a las acumulaciones eólicas, en las que se han realizado estudios geomorfológicos, mineralógicos y una aproximación cronológica a partir de dataciones OSL y restos arqueológicos. Los datos obtenidos ponen en evidencia que las dunas de Cafayate han permanecido activas durante el último milenio, con varias dataciones que indican alta actividad durante la Anomalía Cálida Medieval (1000-1100 AD) y la Pequeña Edad del Hielo (intervalos 1300-1420 AD; 1540-1650 AD; 1740-1830 AD). La utilización de otros datos paleoambientales (climatología e hidrología histórica, arqueología) de ámbito regional permite reconstruir los cambios dinámicos en la actividad eólica en relación con los eventos ENSO cálidos y fríos, así como la posible intervención antrópica en la evolución de estos paisajes áridos.The Cafayate depression is a good example of a pre-Andean arid basin in Northwest Argentina. It comprises the valley of the Río Santa María in its sector of confluence with the Río Calchaquí and presents a wide geomorphological repertoire (fluvial deposits, alluvial cones, lake deposits, dune fields) that provides important information on the Holocene evolution and, in a special way, for the last thousand years. On this occasion, greater attention is devoted to aeolian accumulations, in which geomorphological and mineralogical studies have been carried out, and a chronological approximation based on OSL dating and archaeological remains. The data obtained show that the Cafayate dunes have remained active during the last millennium, with several dates indicating high activity during the Medieval Warm Anomaly (1000-1100 AD) and the Little Ice Age (intervals 1300-1420 AD; 1540-1650 AD; 1740-1830 AD). The use of other palaeoenvironmental data (climatology and historical hydrology, archeology) at a regional level allows us to reconstruct the dynamic changes in wind activity in relation to hot and cold ENSO events, as well as the possible anthropic intervention in the evolution of these arid landscapes.Fil: Peña Monné, Jose Luis. Universidad de Zaragoza; EspañaFil: Sancho Marcén, Carlos. Universidad de Zaragoza; EspañaFil: Sampietro Vattuone, Maria Marta. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Laboratorio de Geoarqueología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Rivelli, Felipe. Universidad Nacional de Salta; ArgentinaFil: Rhodes, Edward J.. University of California; Estados UnidosFil: Osácar Soriano, María Cinta. Universidad de Zaragoza; España. University of Manchester; Reino UnidoFil: Rubio Fernández, Virginia. Universidad Autónoma de Madrid; EspañaFil: García Giménez, Rosario. Universidad Autónoma de Madrid; Españ