Along strike preorogenic thickness variation and onlapping geometries control on thrust wedge evolution: insight from sandbox analogue modelling

Abstract: Thickness variation of sedimentary sequences is largely viewed as a controlling factor on the evolution of orogenic wedges; among the different structural and stratigraphic features generating thickness variation, we focused our analysis on the onlapping geometries, using laboratory sandbox experiments. The aim was trying to describe how a common sedimentary configuration could influence thrusts geometry and mode of accretion. Model results showed that onlapping geometries in pretectonic sediments cause a great complexity, dominated by curvilinear thrusts, back thrust and out-ofsequence thrusts. They also influence mode of accretion, generating diachronous thrusting along strike, reactivation and under-thrusting alternating to simple piggy-back sequence. Our modeling results are compared with natural examples from the Apennines, the southern Pyrenees, the Pindos (Greece) and the West Spitsbergen (Greenland) fold and thrust belts, among many others, where strain localization and diachronic thrusting affecting thrust propagation in correspondence to complex geometries both in the pre-orogenic stratigraphy and in the upper crust.