Glacial deposits in the Serra do Gerês Mountains (NW Iberian Peninsula): till macrofabric analysis

Abstract

Till macrofabric and grain-size analysis of glacial diamictons and sequences present in several valleys of the Serra do Gerês Mountains in the Northwestern Iberian Peninsula were used to interpret till types and to reconstruct the glacial paleoprocess history of this mountainous region. Subglacial lodgement, supraglacial melt-out, and deformation tills are dominant in this range. Subglacial lodgement tills, representative of periods of glacial advance followed by stability in several valleys, present cluster fabrics and generally poorly sorted and fine sediments. Supraglacial melt-out and deformation tills, representative of periods of glacial stability with some minor readvances followed by recession, present weaker fabric data and coarser, poorly sorted sediments. Glacial deposits affected by post-glacial paraglacial activity in the form of landslides were also observed in one valley. These present weaker to moderate fabric data and coarser, poorly sorted sediments. These glacial diamictons and sequences are of particular importance in the reconstruction of the glacial dynamics and history of the Serra do Gerês Mountains due to poor preservation of glacial landforms related to the Last Glacial Maximum in several glaciated valleys.