Role of synkinematic ductile levels on the evolution of compressive zones – analogue modelling

Abstract

In foldbelt faults, layers with ductile behaviour can form levels of decollement [Byerlee, 1978]. When these levels are prekinematic, they play a significant role in the genesis, evolution and final geometry of the foldbelt faults, as, for example in the Appalachian Mountains [Davis and Engelder, 1985], the Jura [Sommaruga, 1999], or the Pyrenees [Verges et al., 1992]. Previous studies based on analogue modelling have shown how a prekinematic decollement level can influence the geometry of foldbelt faults and structures [Ballard, 1989; Colletta et al., 1991; Letouzey et al., 1995; Merle et Abidi, 1995]. However, no study has yet described the influence of synkinematic sedimentation of incompetent levels on the genesis and evolution of compressive structures. The laboratory experiments presented here are designed to explore some of the mechanisms of formation of synsedimentary thrust faults, in relation with the occurrence of a decollement layer during syntectonic sedimentation.