Major shifts in sediment provenance revealed by a Pleistocene drill core record from the Eastern Alps (Austria)

The valley network of the Austrian Eastern Alps was shaped by a complex interplay of tectonic, fluvial, glacial, and karst processes. The sedimentary infill of a glacially overdeepened structure in the Bad Aussee basin provides an excellent opportunity to reconstruct the regional landscape evolution. A drill core, which is investigated as a part of the ICDP (International Continental Scientific Drilling Program) project DOVE (Drilling Overdeepened Alpine Valleys), recovered 880 m of Pleistocene sediments. This unique record shows a succession of subglacial, (glacio-)fluvial and lacustrine deposits.

In this study, we complement sedimentological and geochemical analyses of the drill core material with data obtained from nearby outcrops to investigate the provenance of the basin infill. Petrographic analyses show that metamorphic rocks such as mica schists and gneisses, likely derived from the central Alpine crystalline units to the south of the Enns valley, make up the majority of the gravel fraction over large sections of the succession. As today’s catchment of the river Traun, which drains the Bad Aussee basin, is largely composed of carbonate rocks, major changes in the regional drainage network during the Pleistocene glacial-interglacial cycles can be assumed. Currently ongoing geochronological investigations using a combination of luminescence and cosmogenic nuclide burial dating will help constrain the timing of sediment deposition and improve our understanding of the regional Quaternary topographic evolution.