An exploratory modelling study on sediment transport during the Zanclean flood of the Mediterranean

Abstract

A nearly 400-km-long erosion channel through the Strait of Gibraltar has been interpreted as evidence for a catastrophic refill of the Mediterranean at the end of the Messinian salinity crisis, 5.33 million years ago. This channel extends from the Gulf of Cadiz to the Algerian Basin and implies the excavation of ca. 1000 km3 of Miocene sediment from the Alboran Basin and bedrock from the Strait of Gibraltar. The fate of these eroded materials remains unknown. In a first attempt to predict the distribution of those flood deposits, we develop a numerical model to simulate the transport of material eroded from the Strait of Gibraltar. It is a Lagrangian model based upon standard sediment transport equations which is able to simulate suspended and bed load sediment transport. Water circulation during the flood was obtained from a hydrodynamic model of the whole Mediterranean Sea previously developed by the authors and applied to the Zanclean flood. Five particle sizes were considered for suspended load and three for bed load transport. Areas of sediment deposition in the Mediterranean Sea were determined. In the case of suspended load, these are related to hydrodynamic conditions: areas sheltered from the jet of incoming water by local topography and areas where water currents abruptly decrease due to a sudden increase in water depth. In the case of bed load transport, sediments follow water streamlines and deposits are much more localized than in the case of suspended load. Single channel seismic records were also analysed to identify and characterize flood-related deposits in the eastern Alboran Sea