| Popis: |
The sub-Andean system through Argentina and Bolivia is composed of a fold-and-thrust belt developed from 9 Ma until today, as a result of an east-northeast-verging compressive stress field. Depending on the area evaluated, thin- or thick-skinned deformation characterizes the structural style throughout this orogenic system. The differences in structural styles depend on variables such as the sedimentary column involved, internal facies and thickness changes, detachment level features, climatic influence, and the presence of inherited extensional and compressional structures. The existing balanced structural cross-sections sometimes present difficulties for solving the rate and chronology of the deformation. The aim of this chapter is to present suitable new deformation models integrating distinct kinematic characteristics and to analyze the variables involved in the southern sub-Andean thin-skinned fold-and-thrust belt. The structural framework proposed for the southern sub-Andean system in Bolivia and northwestern Argentina is based in the identification of four rheological levels. Levels 1 and 3, with a shale-dominated composition (Kirusillas and Los Monos Formations, respectively), are deformed as a weak isotropic material and can be simulated using Trishear kinematic modeling. On the other hand, rheological levels 2 and 4 (Tarabuco–Santa Rosa–Icla–Huamampampa Formations and Carboniferous–Cenozoic interval, respectively), with a sand/shale alternating composition, are structured as a strongly heterogeneous interval responding to the compressive stress field with parallel folding. A simple shear kinematic model could be used to simulate this deformation. This behavior has been tested as a feasible model for the deep structure in significant oil/gas fields in Argentina and Bolivia. |
