Marcos Valcárcel Díaz

Pleistocene glaciation in Spain

This chapter discusses the Pleistocene glaciation in Spain. After a century and a half of research on Pleistocene glaciation in Spain, it is still difficult to make generalizations regarding the maximum glacial limits and the age of the individual ice advances, because many glaciated areas have still to be analyzed in detail. The glaciation was controlled not only by the preexisting landforms and the altitude, but also by the available humidity, related to their distance from the sea. This explains the progressive rise of the Equilibrium Line Altitude (ELA) towards the east and south, as well as the extensive glaciation in the northwestern mountains. From the avaliable data it can be concluded that, although the Wurmian glaciation seems to have been the dominant one, there is some evidence of previous glacial cycles.

Upper Pleistocene glacial valley-junction sediments at Pias, Trevinca Mountains, NW Spain

Abstract Sediments at Pias (Galicia) provide evidence of Upper Pleistocene glacial activities at a valley junction in the north-western mountains of Spain. The sedimentary sequence consists of lower, predominately fine-grained lacustrine deposits with few lonestones, overlain by poorly sorted, sandy gravels interstratified with massive diamicton deposited during mid-Weichselian times (MIS 3) (marine isotope stage 3). The lacustrine sediments were deposited in a glacial valley temporarily dammed by a confluent glacier. The presence of active ice is suggested by massive diamicton layers best interpreted as till, rafted sediments in lacustrine deposits and deformation structures indicative of loading and kettle formation. Frozen ground conditions are suggested by a few involution-like structures. The Pias area contains one of the few western-Spain sedimentary records of Upper Pleistocene glaciation at relatively low latitude (about 42°N) and low altitude (less than 1000 m a.s.l.). A southern dip of the Polar front to 40–45°N latitudes, as occurred during Last Glacial Maximum, could have cut moisture to the northern Fennoscandinavian ice sheets. At the same time, however, sufficient precipitations would have persisted in north-western Spain to sustain extensive ice caps and their outlets to elevations as low as c. 900 m a.s.l.

Geomorfología del valle glaciar de Balouta (Ancares Leoneses - NW de la Península Ibérica)

En valle de Balouta ha sido estudiado con anterioridad por LLOPIS LLADO (1954) y por nosotros (PEREZ ALBERTI ET AL., 1993). En este ultimo trabajo se citaba la presencia de un afloramiento de materiales de origen glaciar en las cercanias del pueblo de Murias, a unos 780 m de altitud, despues de atravesar un sector del valle muy encajado de unos 6 km de longitud. Estos depositos senalan el maximo avance reconocido del glaciar de Balouta y superan ampliamente la dimension del glaciarismo descrito por LLOPIS LLADO en su momento. Este autor baso sus hipotesis restrictivas en las formas niticas de acumulacion presentes en el valle de Malevo. El descubrimiento de nuevos afloramientos, asi como el avance en el conocimiento sobre el glaciarismo pleistoceno en el NW peninsular, nos permite completar la vision dada por el citado autor. En el presente trabajo se presenta una cartografia de las formas y depositos del valle de Balouta y se reconstruye la dinamica del aparato glaciar a partir de los datos geomorfologicos, al tiempo que se aportan algunas referencias metodologicas en un intento de conceptualizar mejor los problemas referentes al glaciarismo y periglaciarismo iberico.