2D modelling of large-scale platform margin collapses along an ancient carbonate platform edge (Maiella Mt., Central Apennines, Italy): geological model and conceptual framework

Results of numerical simulations of large-scale platform margin collapses along the edge of the Cretaceous platform of the Maiella (Central Apennines) are presented, adding a new contribution to the understanding of the role and quantification of the various factors that control triggering of these phenomena and the production of breccias and megabreccias. For this purpose, a sophisticated numerical code, widely used in recent contexts to simulate overall mass movements and deep gravity-driven deformation, is applied for the first time to an ancient system on a scale of several kilometres. The modelling carried out is a simplified attempt to understand a very complex phenomenon produced over a very long time-span. It tests whether the perturbing causes in the model, acting together or separately, are able to activate such large-scale collapse, and helps to understand the effects of perturbing causes and their variations. In particular, modelling was carried out considering both static (variations in sea level) and dynamic (seismic events without and with fault formation) conditions and combinations of them. Variations in sea level alone do not produce all the effects observed but may certainly be a predisposing element. Seismic shock simulations show that fracturing and shear stresses are concentrated on the platform margin, representing the most sensitive and vulnerable area. Earthquake swarms associated with an active fault are the most likely means of triggering large-scale platform margin collapses, such as those occurring during the Early Cretaceous in the Maiella.