The occurrence of along-strike thickness variations in pretectonic sedimentary packages is expected to influence the structural architecture of doubly verging thrust wedges. To test this hypothesis, we used laboratory sandbox experiments. Model results show that longitudinal tapering of pretectonic sediments causes a great complexity in the internal tectonic fabric of the wedge, particularly in the pro-wedge, dominated by highly segmented, curvilinear thrusts. The along-strike variation of the mode by which the same amount of bulk contraction is accommodated in different regions of the orogen produces the obliquity of the deformation fronts in both the pro-wedge and the retro-wedge. Comparison with the overall architecture of the Lesser Antilles and Manila accretionary systems validates our experimental results.
