A sedimentological and stratigraphical study of Veiki moraine in northernmost Sweden

Abstract: Veiki moraine is a landform area consisting of rim-ridged subcircular hummocks and plateaus with depressions in between, mostly located within a N-S extending zone of a hummocky landscape. It is believed to have formed during the pre-late Weichselian and survived overriding by ice during the subsequent glaciations. Due to their good preservation, the Veiki moraine provides valuable information on the glaciation and prevailing environmental conditions in northern Sweden during the earlier stages of Weichselian glaciations, as well as the ice dynamics of the late Weichselian ice sheet. To determine the internal stratigraphy of the moraine plateaus and interpret the depositional environment, excavation into two Veiki moraine plateaus were carried out. The sections investigated were supplemented by morphological data from LiDAR elevation models and GPR profiles. In addition, sorted sediment units within the two Veiki moraine plateaus were sampled for radiocarbon and OSL dating. The two moraine plateaus investigated seem to consist of massive diamicton in the center. The rim ridges are built up by stratified debris flow units, partly underlain by organic-rich lake sediment. The elevated position of these sediments indicates that the moraines were surrounded by ice at the time of deposition. They are interpreted to have formed by debris and meltwater inflow into depressions on a debris-covered stagnant ice mass. After the surrounding ice had melted they were left standing as high points in the landscape. The moraine plateaus and the surroundings are covered by a thin till bed deposited by subsequent glaciations. Dating of lake sediment suggest deposition around 50,000 years BP. This indicates deposition during the Tärandö II interstadial, which followed the glaciation in MIS 4 during the Weichselian glaciation cycle.