Sedimentary evidence for an ice-sheet dammed lake in a mountain valley of the Eastern Sudetes, Czechia

An accumulation of glacial sediments is located near Písečná village in the depression between the Sokol Ridge and Zlaté Hory Highlands NNE of Jeseník town (Eastern Sudetes). The accumulation lies at the lateral side of the mountain valley of the Bělá River and fills a preglacial palaeovalley of this river. Research combining facies analysis of outcrops, ground penetrating radar survey, interpretation drilling survey, and modelling of the preglacial relief was undertaken at the site. According to the results obtained, the upper part of the sedimentary accumulation represents a coarse-grained terminoglacial glaciofluvial delta of the Gilbert type. The development of the accumulation has dominantly been driven by the preglacial morphology. Facies typical for foresets of coarse-grained deltas represented mainly by high-density flows, cohesionless debris flows, debris falls and less common low-density flows were found in the outcrops. The delta near Písečná prograded into a lake dammed by the ice-sheet front in the north. The lake was bounded by the slopes of Sokol Ridge, Zlaté Hory Highlands and Góry Parkowe on other sides. The lake level reached an altitude of up to 430 m a.s.l., as the coarse-grained delta plain base lies at this level