Control of syntectonic erosion and sedimentation on kinematic evolution of a multidecollement thrust zone: Analogue modeling of folding in the southern subandean of Bolivia

Romain Darnault (1) , Jean-Paul Callot (2, 3) , Jean-François Ballard (4) , Guillaume Fraisse (5) , Jean-Marie Mengus (1) , Jean-Claude Ringenbach (4)

1 IFPEN - IFP Energies nouvelles
2 UPPA - Université de Pau et des Pays de l'Adour
3 LFCR - Laboratoire des Fluides Complexes et leurs Réservoirs
4 TOTAL S.A.
5 Ecole Nationale Supérieure de Géologie

13 Several analogue modeling studies have been conducted during the past fifteen years with the 14 aim to discuss the effects of sedimentation and erosion on Foreland Fold and Thrust Belt, 15 among which a few have analyzed these processes at kilometric scale (Nalpas et al., 1999; 16 Barrier et al., 2002; Pichot and Nalpas, 2009). The influence of syn-deformation 17 sedimentation and erosion on the structural evolution of FFTB has been clearly demonstrated. 18 Here, we propose to go further in this approach by the study of a more complex system with a 19 double decollement level. The natural study case is the Bolivian sub-Andean thrust and fold 20 belt, which present all the required criteria, such as the double decollment level. A set of 21 analogue models performed under a CT-scan have been used to test the influence of several 22 parameters on a fold an thrust belt system, among which: (i) the spatial variation of the 23 sediment input, (ii) the spatial variation of the erosion rate, (iii) the relative distribution of 24 2 sedimentation between foreland and hinterland. These experiments led to the following 25 observations: 26 1. The upper decollement level acts as a decoupling level in case of increased 27 sedimentation rate: it results in the verticalization of the shallower part (above the 28 upper decollement level), while the deeper parts are not impacted; 29 2. Similarly, the increase of the erosion rate involves the uplift of the deeper part (below 30 the upper decollement level), whereas the shallower parts are not impacted; 31 3. A high sedimentation rate in the foreland involves an inversion of the vergence 32 followed by a back-thrusting of the shallower part. 33 4. A high sedimentation rate in the hinterland favors thrust development toward the 34 foreland in the shallower parts. 35 36

Mots clés: Field examples; Decrease of exploration uncertainties; Skynkinematic sedimentation; Southern subandean of Bolivia; Multidecollement thrust zone; Analogue modeling; Syntectonic erosion and sedimentation; Wedges; Belt

Domaines: Sciences de la Terre; Géologie appliquée

Romain Darnault, Jean-Paul Callot, Jean-François Ballard, Guillaume Fraisse, Jean-Marie Mengus, et al.. Control of syntectonic erosion and sedimentation on kinematic evolution of a multidecollement thrust zone: Analogue modeling of folding in the southern subandean of Bolivia. Journal of Structural Geology, 2016, 89, pp.30-43. ⟨10.1016/j.jsg.2016.05.009⟩. ⟨hal-01449660⟩