GLACIARISMO Y GEOLOGÍA


2007 2009 2011

El de Sanabria es el lago más grande de España con origen glaciar y a la vez se puede considerar el más occidental de todo el Paleártico; dada esta singularidad está considerado como Lugar de Interés Geológico -LIG- por el Instituto Geoológico y Minero de España (IGME)

Última actualización: 17/12/2017  11:49:11  


2007 / M. Rico, B. Valero Garcés , J.C. Vega, A. Moreno , P. González-Sampériz, M. Morellón  y P. Mata

El registro sedimentario del Lago de Sanabria desde la última deglaciación

Resumen

The sedimentary evolution of Sanabria Lake (Zamora province, NW Spain) is reconstructed based on 4 kullenberg cores and 3 short cores. The longest core (9 m long) in the deepest (51 m) eastern subbasin reached the laminated and banded clastic proglacial lacustrine sediments deposited when the watershed was still glaciated. Basal 14C AMS dating (ca. 26 ka BP) indicates that the terminal morraine complex deposited prior to the global LGM.

A high resolution study including magnetic susceptibility and XRF core-scanner geochemistry show millennial and century scale cycles in Lateglacial and Holocene organic-rich sediments. Calibration studies including 20 year long series of limnological data, short sediment cores, meteorological and land-use changes data are in progress.

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 2009 /  T. Cowton, P.D. Hughes  y  P.L. Gibbard

Palaeoglaciation of Parque Natural Lago de Sanabria, northwest Spain

Resumen

Detailed geomorphological mapping provides evidence for at least three phases of glaciation in the Parque Natural Lago de Sanabria, in northwest Spain. The most extensive glaciation was characterised by a large plateau ice cap. A combination of geomorphological evidence and glacier modelling indicates that this ice cap covered an area of more than 440 km2, with a maximum ice thickness of c. 300 m and outlet glaciers reaching as low as 1000 m. This represents the largest ice mass in Iberia outside the Pyrenees and one of the largest in the mountains of southern Europe and the Mediterranean region. Radiocarbon dates from the base of lacustrine sequences appear to suggest that the most extensive phase of ice-cap glaciation occurred during the last cold stage (Weichselian) with deglaciation occurring before 14–15 ka 14C BP. A second phase of glaciation is recorded by the moraines of valley glaciers, which may have drained small plateau ice caps; whilst a final phase of glaciation is recorded by moraines in the highest cirques.

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2011 / Laura Rodríguez-Rodríguez, Mª José Domínguez-Cuesta Montserrat Jiménez-Sánchez

Reconstrucción en 3D del máximo glaciar registrado en la cuenca del Lago de Sanabria (Noroeste de España)

Resumen

La realización de una cartografía geomorfológica detallada en una superficie de 220 km2 en torno al Lago de Sanabria (Noroeste de España), junto con la caracterización sedimentológica de los depósitos glaciares, han permitido reconstruir la extensión alcanzada por el hielo durante el máximo glaciar local. De acuerdo con este modelo, el aparato glaciar instalado sobre la cuenca del Lago de Sanabria alcanzó una extensión de al menos 155 km2, situando su frente más avanzado en el valle Tera (940 m). Sus límites septentrional y oriental habrían sobrepasado los límites de estudio, de modo que este aparato glaciar constituiría una fracción de un casquete montañoso más grande instalado sobre el Macizo de Trevinca, al oeste de la zona de estudio.

Se ha aplicado un modelo matemático para establecer la altitud alcanzada por el hielo a lo largo de 29 perfiles longitudinales siguiendo las paleo-direcciones de flujo del hielo indicadas por las evidencias geomorfológicas. La integración de todos los datos mediante un SIG ha permitido elaborar un modelo digital de la topografía del hielo a partir del cual se ha podido determinar tanto la distribución de potencias del glaciar (entre 0 y 454 m), como su volumen total (estimado en 22,9 km3) durante el máximo glaciar local.

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2011 /  Laura Rodríguez-Rodríguez, Montserrat Jiménez-Sánchez, María José Domínguez-Cuesta, Vincent Rinterknecht, Raimon Pallàs, Didier Bourlès y Blas Valero-Garcés

Last deglaciation in northwestern Spain: New chronological and geomorphologic evidence from the Sanabria region

Resumen

Geomorphologic mapping, morphometric analysis of glacial features, and sedimentologic characterization of glacial deposits, together with GIS management, have led to reconstruction of the glacial evolution of the Tera valley glacier (Sanabria Lake basin, NW Spain) after the local glacial maximum. Moreover, a structural analysis of the bedrock fracture network based on a detailed map containing 898 fractures has been used to evaluate the influence of bedrock geology in the development of the glacier pattern. A detailed model of the deglaciation has been constructed by complementing the geomorphologic evidence with the chronological and sedimentologic study of a drilling core retrieved from the eastern subbasin of Sanabria Lake in 2004. According to this model, 10 episodes of glacier front retreat and stabilization took place after the local glacial maximum. Subsequently, a proglacial lake was established in the eastern subbasin of current Sanabria Lake, fed by ablation waters coming from the glacier front retreat. The proglacial activity was extended from a minimum age of 25.6 to 14.3 ka BP, in which the sedimentation of organic-rich muds took place until 13.1 ka BP. Subsequently, around 13.1 to 12.2 ka BP, a short advance of the Tera glacier is inferred from the deposition of coarser and less organic sediments. After this date, the glacier front would have retreated to the headwaters of the Tera valley. Sedimentologic and chronological data from another core retrieved in a moraine-dammed deposit indicate that a marginal lake would have been active since at least 22 ka BP until at least up to 10.5 ka BP to the north of Sanabria Lake. These results suggest a local glacial maximum prior to the global LGM and, therefore, new evidence of an early deglaciation in SW Europe.

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