Post-collisional sediment budget history of the Alps: tectonic versus climatic control

Abstract.

Based on the sediment budget of the Eastern, Swiss and Western Alps since the Oligocene the regional tectonic evolution has been identified as the dominant factor. It is superimposed on the influence of both regional and global climate change and global sea-level change. During late Pliocene and Pleistocene times, climate became the dominant factor because of cyclic glaciations. The early post-collisional history of the Alps is characterized by a doubling of sediment discharge rates around the Rupelian/Chattian boundary. This increase is attributed to isostatic re-adjustment either after large-scale thermal reorganization of the lithosphere related to slab break-off, or to crustal thickening as continental crust became subducted. From Middle Oligocene to Late Miocene times, the overall trend of sediment discharge rates in the entire Alps was modified only during relatively short-lived phases. These are characterized by an increase in Aquitanian (ca. 23–21 Ma) and late Burdigalian times (ca. 18–16.4 Ma), and a decrease in early to middle Burdigalian (21–19 Ma) and Langhian to Serravalian times (16.4–12 Ma). An important, still ongoing period of uplift, reflected by rapidly increasing sediment discharge rates, started in latest Miocene times in the Swiss and Western Alps and affected the Eastern Alps some 2 million years later. The reason for this uplift is not clear, but deep-seated lithospheric processes appear to be likely.