Influence of synkinematic sedimentation in a thrust system with two decollement levels; analogue modelling

Abstract

International audienceCompressive systems in foreland domains are characterised by fold and thrust belts linked to the presence of one or several ductile layers in depth acting as a decollement level. The main parameters controlling the structural evolution are: the presence of a decollement level, theamount and rate of shortening, and the amount of synkinematic sedimentation. The effect of these parameters has only been studied on a thrust belt scale. Furthermore, only the effect of synkinematic sedimentation on a simple system with one decollement level has been studied at the scale of a single structure. The aim of this study was to use analogue modelling to test the effect of shortening rate, velocity and the localization of sedimentation on a single system characterised by the presence of two prekinematic decollement levels. The main results showed variations in the structural vergence, folding geometry (symmetric or asymmetric), the evolution of the deformation (horizontal propagation versus vertical uplift), and the decoupling of the lower and upper brittle structures in relation with the main parameters (shortening rate and mass transfer). The results of the experiments were then compared to natural examples from the sub-Andean thrust belt

Influence of Overlapping décollements, Syntectonic Sedimentation, and Structural Inheritance in the Evolution of a Contractional System: The Central Kuqa Fold‐and‐Thrust Belt (Tian Shan Mountains, NW China)

“…They efficiently propagate deformation toward the foreland and yield the development of complex thrust systems whose geometry and kinematic evolution is strongly controlled by the lithology, overlap, lateral extent, and interaction between décollements (Ruh et al, ; Sans et al, ; Santolaria et al, ). Besides, the behavior and role of weak décollements under contraction are also determined by (i) their interaction with underlying basement features (that can partly correspond to inherited structures; Giambiagi et al, ) and (ii) by the thickness and distribution of overlying syntectonic sequences (Duerto & McClay, ; Pichot & Nalpas, ). The restored cross section presented in this work takes all these factors into account and puts forward a new structural model that can be relevant for the understanding of other fold‐and‐thrust systems involving multiple décollements, basement faulting, and variable syntectonic sedimentary rates.…”

Multidisciplinary approach to constrain kinematics of fault zones at shallow depths: a case study from the Cameros–Demanda thrust (North Spain)

“…Transport direction can also vary through time according to the boundary conditions imposed by erosion and sedimentation. Analogue models with sandsilicone systems (Barrier et al 2002;Pichot and Nalpas 2009) indicate that the geometry of thrusts changes due to syn-tectonic sedimentation at its front, usually developing steeper thrust surfaces. Associated changes in transport direction have not been analyzed yet, but at certain obliquities between the shortening direction and the strike of thrusts, the increase in dip of the thrust surface could favor, from the mechanical point of view, stronger strikeslip versus dip-slip components.…”

Physical Modeling of Fold‐and‐Thrust Belt Evolution and Triangle Zone Development: Dabashan Foreland Belt (Northeast Sichuan basin, China) as an Example

“…Our experiments only take two parameters into account: decollement and mechanical contrast. Other factors, such as synsedimentation and erosion, which were neglected, can also influence deformation and have been previously studied in depth (Mugnier et al, 1997;Bonini, 2001;Pichot and Nalpas, 2009). The neglecting of fluid pressure makes the slope steep (Davis et al, 1983).…”

“…2c) in the front in the foreland direction (Jamison, 1993). Multiple factors might influence the formation and development of triangle zones, including the property of decollements, the mechanical contrast of lithology, the converging velocity, and erosion and synsedimentation (Lawton et al, 1994;Couzens and Wiltschko, 1996;Teixell and Koyi et al, 2003;Couzens-Schultz et al, 2003;Ferrill et aI.,2008;Mugnier et al, 1997;Bonini, 2001;Pichot and Nalpas, 2009). Yet multiple decollements and the mechanical contrast of lithology are (Jamison, 1993 The questions posed in this study include: what is the process of triangle zone formation and development?…”