Tills and related deposits linked to glacier dynamics in the Sierra do Xistral: interpretation of lithofacies and paleoglacier reconstruction

Abstract

The glaciers developed in the mountains of Sierra do Xistral shaped a glacial landscape, although not well defined. It is a low-lying mountain that was covered by an icecap during the Upper Pleistocene. The occurrence of moraine ridges, outwash plains, erratics and kames has been described. The places where deposits of glacial origin can be studied are relatively scarce, but this does not prevent good examples. Different types of till have been described, both sub-glacial and supraglacial, as well as fluvioglacial and torrential deposits. Their interpretation is an important element for understanding the glacial dynamics in this sector. This work is based on the usual method of work in this type of studies, which includes a visual analysis of the different sedimentary outcrops and their integration into the local geomorphological context. The genetic interpretation of the outcrops allows us to determine the extent of the glaciation in the Sierra do Xistral, determining which areas of the valley were occupied by the glacial ice and which were free of it.