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