Analogue modeling of large-transport thrust faults in evaporites-floored basins: Example of the Chazuta Thrust in the Huallaga Basin, Peru

The Huallaga Basin is a deformed foreland basin located in North Peru. The basin comprises several syntectonic depocenters. The most significant is the Biabo Syncline located at the back of the Chazuta Thrust, a long, flat-floored thrust detaching on an evaporitic décollement, which has accommodated more than 40 km of horizontal displacement. The hangingwall of the Chazuta Thrust has remained remarkably intact with little or no internal deformation and has incorporated a large volume of evaporites at its base. In order to unravel the formation and evolution of this thrust, we conducted a series of physical experiments that tested the role of various parameters. The goal is to investigate a system in which most of the deformation is accommodated in the frontal part of the chain (Chazuta Thrust), whereas deformation of the thrust sheet itself remains minor. Results from our experimental investigations suggest that the three key parameters that have allowed for such a long-lived, large-slip frontal thrust to operate are (1) the wedge-shaped syn-kinematic sedimentation, (2) the presence of the Biabo Syncline, which acted as a bulldozer pushing the evaporites forward, forcing their distal inflation and (3) the erosion at the front that favored farther advance of the frontal thrust, dragging passively large volumes of evaporites along with it.