4-D Basin Reconstruction and Palaeooceanographic Simulations of the Peri-Alpine Foreland Basin During the Early Miocene

Ulrich Bieg¹ and Michael Peter Suess^2
1 Technical University of Darmstadt, Darmstadt, Germany
² Harvard University, Cambridge, MA

During the Early Miocene the Alpine foreland basin was flooded by a shallow marine seaway, linking the western Mediterranean with the Paratethys. The seaway was a conduct for the transport of significant amounts of sediments from the emerging Alps to the Mediterranean. We reconstructed the time progressive global and regional fluctuations in eustatic and tectonic conditions that caused key oceanographic parameters (palaeogeography, palaeobathymetry, stratification and boundary tides) and sediment-transport regimes to vary widely throughout in the Burdigalian Seaway's history. Tidal deposits in the central molasse basin indicate a meso- to macrotidal system during the maximum Miocene flooding stage. Numerical simulations evaluate how these can be generated considering varying tidal amplitudes and phase as well as atmospheric forcing and freshwater influx. Our numerical simulations showed that it is not possible to generate a mesotidal system by using one incident tidal wave from the Mediterranean, but that two counter-propagating tidal waves at both open gateways are necessary. Without any further forcing terms the calculated sediment transport directions show a complicate pattern of circulation cells and joint half circles, which are likely closed for sediment transport. Applying fresh water influx from the fan delta systems and major rivers at the Swiss and German coastline forces the net transport in the central seaway towards two opposed current branches allowing for significant amounts of sediments to be directed towards the East and West.