Post-LGM coastline evolution of the NW Sicilian Channel: Comparing high-resolution geophysical data with Glacial Isostatic Adjustment modeling.

Abstract

Since about 20,000 years ago, the geography of the Earth has been profoundly modified by the gradual sea-level rise caused by the melting of continental ice sheets. Flat areas and regions characterized by very low gradients experienced, more than others, rapid flooding, with the progressive disappearance of vast coastal territories. Here we present a reconstruction of the late Quaternary coastline evolution of the north-western sector of the Sicilian Channel, constrained by high-resolution seismic profiles where the marker of the post-Last Glacial Maximum (LGM) marine transgression has been clearly identified and mapped. The locations of the post-LGM seismic horizon have been compared with predictions of a Glacial Isostatic Adjustment (GIA) model, which accounts for the migration of the shorelines in response to sea-level rise and for Earth's rotational and deformational effects associated with deglaciation. We have verified that most of the points mapped through seismic data interpretation fall along the palaeo-coastline that the GIA model predicts for the 21 kyrs B.P. time frame. However, the model shows a misfit in the marine sector between Mazara del Vallo and Sciacca, where the available data indicate a Quaternary tectonic uplift. The analysis of the seismic profiles provides useful constraints to current GIA models. These add on existing histories of relative sea level in the Mediterranean Sea, allowing to gain new insight into the evolution of the palaeo-geography of the region of study and of the whole Sicilian Channel since the LGM, even in areas where direct geophysical observations are not available yet. In this respect, one of the most attractive implications of the ancient coastline evolution is linked with the underwater archaeology. The sea-level rise heavily impacted the distribution of human settlements, possibly forcing site abandonment and migrations, and this is particularly relevant in the Mediterranean basin, the cradle of the western civilization. The underwater traces left by these ancient populations represent the fundamental proofs to reconstruct the early history of our precursors.