Late Pleistocene glaciofluvial sedimentation in Gariūnai–Pagiriai proglacial valley, SE Lithuania

Abstract

The results of studies of glaciofluvial sediments and their sedimentation in a proglacial valley in the northern part of SE Lithuanian outwash plain are presented. The aim of the study was to compare the features of sediments in the geomorphologically well expressed Gariūnai–Pagiriai proglacial valley with the rest part of the SE Lithuanian Sandy Plain in which the complexity of proglacial fluvial sedimentation was revealed during the resent investigations. The change of depositional structures of sandy sediments and grain size distribution in vertical sediment sequences was studied for lithofacies analysis. The studies carried out let to interpret the sedimentation conditions of deposits in the proglacial valley as a meandering stream of SE direction, which downstream turns SW and intersects the SE Lithuanian Sandy Plain composed of braided stream outwash sediments. Lithofacies of proglacial valley deposits were distinguished in the deposit sequences due to a qualitative sedimentological research. Mid-channel and side-channel bar deposits of the proglacial valley were described and conditions of their sedimentation were evaluated. It was interpreted that formation of glaciofluvial terraces in the proglacial valley took place in several stages under the changing mode of ice meltwater flow and the steady source of clastic sediment material.