Análisis sedimentológico del embalse de Barasona, Huesca

[Resumen] La pérdida de capacidad debido al aterramiento es un grave problema en numerosos embalses. El pantano de Barasona, en la cuenca del Esera-Isábena, Pirineos Centrales, uno de los más antiguos de España, ha perdido un tercio de su 3 capacidad inicial (71 Hm ) desde su construcción en 1932. El estudio de 23 sondeos ha permitido caracterizar el sedimento,definir facies sedimentarias, reconstruir tridimensionalmente el relleno del vaso y proponer un modelo deposicional dominado por las fluctuaciones en el régimen de aporte de los ríos. Las variaciones en la composición mineralógica proporcionan información sobre áreas fuente y procesos de erosión y transporte en la cuenca. Correlacionando los niveles de limos arenosos con los episodios de avenidas, se ha construido una cronología preliminar que permitirá evaluar variaciones en la tasa de aporte de sedimentos al embalse y en la dinámica del sistema embalse-cuenca..[Abstract] Sediment deliver and consequent loss of water storage capacity aggravate reservoir management problems. The Barasona reservoir in the Esera-Isabena watershed, Central Pyrenees, is one of the oldest in Spain (1932) and has lost one 3 third of its initial water capacity (71 Hm ). In this study we analyze the composition of the infilling of the Barasona reservoir, identify sedimentary facies, and reconstruct the tri-dimensional geometry based on 23 cores. Sedimentary dynamics is mainly controlled by fluctuations in the river inflow. Changes in mineral composition inform of sediment provenance and transport processes in the catchment area. A preliminary chronology based on the identification of floods in the sedimentary record (sandy silt layers) will allow to investigate changes in the sediment yield and in the interaccions reservoir-catchment

Limnogeologúa de Laguna Chungará y cambio climático durante el Holoceno superior en el altiplano chileno septentrional

[Resumen] El estudio sísmico de la Laguna Chungará (69° 30' O, 18° 15'S, 4520 m. s.n.m, Altiplano chileno septentrional) y el análisis sedimentológico de varios sondeos ha permitido reconstruir la evolución de la sedimentación lacustre en el lago durante el Holoceno Superior. Se han identificado dos asociaciones de facies: i) litoral, más somera, compuesta por facies de turbera y in plataforma lacustre, más profunda, compuesta por facies con abundantes fragmentos de Characeae. Estas facies alternan en tres ciclos sedimentarios provocados por fluctuaciones en el nivel del lago. Estas variaciones hidrológicas en la laguna han sido causadas por cambios en el balance hídrico que a su vez reflejan importantes fluctuaciones climáticas durante el Holoceno Superior.[Abstract] We reconstruct the Late Holocene sedimentary history of Laguna Chungará (69° 30' W, 18° 10'5, 4520 m.a.s.l., northern Chilean Altiplano) based on high resolution seismic profiling and sedimentologic analyses of cores. Two sedimentary facies associations have been defined and interpreted: n macrophytedominant littoral, composed of black muds with macrophyte remains and peaty muds, and in Characeae-dominant lacustrine self, composed of gray muds and sands with abundant Characeae remains. The two facies associations define three cycles caused by oscillations in the lake level from shallower (macrophyte) to deeper (Characeae) conditions. Changes in the hydrology of Laguna Chungará reflect variations in the effective moisture (precipitation - evaporation) in the Altiplano during the Late Holocene

Hacia una enseñanza universitaria participativa y no jerarquizada : desarrollo de un método activo-solidario. Un ejemplo en la enseñanza de la Petrología

Presentamos una experiencia didáctica realizada en la Universidad de Zaragoza con el alumnado de tercero de Ciencias Geológicas, en un curso cuatrimestral de Petralogía de Rocas Sedimentarias y Metamórficas. Pretendemos demostrar que es posible una enseñanza de calidad en la que una mayoría de los estudiantes desarrollen el máximo de sus potencialidades.We want to presente a didactic experiment wich was carried put for a term in a course on "Exogenous and Metamorphic Rock petrology" within the third tear of Geological Studies. Our experiment tries to show the likeliness of a kind of university studies where students can have a greater share and therefore develop their full potentiality

Hacia una enseñanza universitaria participativa y no jerarquizada : desarrollo de un método activo-solidario. Un ejemplo en la enseñanza de la Petrología

Presentamos una experiencia didáctica realizada en la Universidad de Zaragoza con el alumnado de tercero de Ciencias Geológicas, en un curso cuatrimestral de Petralogía de Rocas Sedimentarias y Metamórficas. Pretendemos demostrar que es posible una enseñanza de calidad en la que una mayoría de los estudiantes desarrollen el máximo de sus potencialidades.We want to presente a didactic experiment wich was carried put for a term in a course on "Exogenous and Metamorphic Rock petrology" within the third tear of Geological Studies. Our experiment tries to show the likeliness of a kind of university studies where students can have a greater share and therefore develop their full potentiality

Andean drought and glacial retreat tied to Greenland warming during the last glacial period

Abrupt warming events recorded in Greenland ice cores known as Dansgaard-Oeschger (DO) interstadials are linked to changes in tropical circulation during the last glacial cycle. Corresponding variations in South American summer monsoon (SASM) strength are documented, most commonly, in isotopic records from speleothems, but less is known about how these changes affected precipitation and Andean glacier mass balance. Here we present a sediment record spanning the last ~50 ka from Lake Junín (Peru) in the tropical Andes that has sufficient chronologic precision to document abrupt climatic events on a centennial-millennial time scale. DO events involved the near-complete disappearance of glaciers below 4700 masl in the eastern Andean cordillera and major reductions in the level of Peru’s second largest lake. Our results reveal the magnitude of the hydroclimatic disruptions in the highest reaches of the Amazon Basin that were caused by a weakening of the SASM during abrupt arctic warming. Accentuated warming in the Arctic could lead to significant reductions in the precipitation-evaporation balance of the southern tropical Andes with deleterious effects on this densely populated region of South America

Progress in Detection and Projection of Climate Change in Spain since the 2010 CLIVAR-Spain regional climate change assessment report

The Iberian Peninsula region offers a challenging benchmark for climate variability studies for several reasons. It exhibits a wide variety of climatic regimes, ranging from wet Atlantic climates with annual precipitation around 2000 mm, to extensive semiarid regions with severe hydrological stress, to even cold alpine environments in some isolated areas

Geoelectrical and electromagnetic methods applied to paleolimnological studies: Two examples from desiccated lakes in the Basin of Mexico

Paleolimnological studies require a broad understanding of the geometry and depth of the sedimentary fill of lake basins prior to coring campaigns. Seismic methods are routinely employed for the indirect characterization of lake-bottom sediments. However, the use of seismic methods might occasionally be limited due to surface conditions or poor seismic contrasts between the stratigraphic units, which lead to data quality that is too poor to provide sufficient information for the selection of drill sites. Sources of cultural noise are one of the main reasons why seismic methods fail in study areas near or within large cities, such as Mexico City. Under certain conditions, electrical and electromagnetic methods might be a suitable substitute or complement to seismic exploration, as they respond to different physical properties of the subsurface. To evaluate the applicability of such methods, here we present two recent case studies from the desiccated lakes Chalco and Xochimilco both located in urban areas within the Basin of Mexico where electrical resistivity tomography (ERT), transient electromagnetic (TEM) and magnetotelluric (MT) soundings were conducted for the characterization of lake basement and lacustrine sediments. In both examples, the results of the geophysical exploration contributed valuable stratigraphic information for the following drilling and core recovery, which highlights the potential of electrical and electromagnetic methods in paleolimnological studies