Kinematic and mechanic evolution of the Andes buried front at the Boomerang Hills hydrocarbon province (Bolivia): Control exerted by the pre-Andean history

Abstract

Abstract The Boomerang Hills are a hydrocarbon-rich region located in front of the Bolivian Andes, central South America, where the Andean chain bends forming the Bolivian Orocline. The geological interpretation of seismic (2D profiles and 3D volumes) and well data allowed us to generate a complete stratigraphic section, cross sections, maps and a 3D model, and to obtain the parameters to carry out a depth conversion and decompaction. A cross section and a 3D model were kinematically and mechanically restored, as well as decompacted, to decipher the evolution of this region through time. The southern Boomerang Hills are the buried frontal part of the Andes where thin-skinned contractional structures of Andean age (Late Cenozoic) predominate, whereas the northern Boomerang Hills belong to the Beni-Chaco Plain, where contractional structures are almost absent and thick-skinned extensional tectonics of pre-Andean age (Paleozoic, Mesozoic and Early Cenozoic) dominate. The buried frontal thrust of the Andes resulted from transpressional reactivation of a gravity-driven, extensional detachment developed along the slope of a basement high tilted during Paleozoic times. Thus, the thrust orientation, position, dimensions and type of structural termination were controlled by the extensional fault geometry, the Paleozoic mechanical stratigraphy, and the structural relationships between the Paleozoic cover and the basement.