The last and penultimate glaciation in the North Alpine Foreland: New stratigraphical and chronological data from the Salzach glacier

摘要

The Northern Alpine Foreland was repeatedly covered by massive piedmont glaciers during Quaternary glacial maxima. The Salzach palaeoglacier lobe (Austria/Germany) was the easternmost of a series of Pleistocene piedmont glaciers entering the foreland through major alpine valleys. It covered an area of more than 1000 km(2) during at least four glacial maxima. Here we aim to bring more light into its history by analyzing multiple drill log data, two major outcrops, topographic data, and absolute chronologies of sediments. Stratigraphic and lithofacies investigations are focused on proximal (i.e. near the lobe axis) and distal (i.e. near terminal moraine) deposits of the Salzach glacier lobe. The glacial carving into the Miocene bedrock occurred during early glacial maxima and was rather uniform across the lobe with larger values only in the proximal parts of the glacier. More than 100 m of accumulated sediments during later glacial maxima indicate a change in ice-sheet dynamics and a characteristic sequence development which varies from proximal to distal lobe positions. New luminescence ages suggest a depositional focus at the penultimate glacial period while the impact of the LGM was rather minor. Sediments of gravelly braided-rivers dominate the proximal parts of the former lobe where meltwater discharge was generally high, while sheetflood deposits dominate the distal, near terminal lobe positions. (C) 2015 Elsevier Ltd and INQUA. All rights reserved.