In this chapter, we study the geometry and evolution of the Andean fold and thrust belt located between 35° and 36°S. The main goal of this chapter is twofold; the first is to propose a new Neogene chronostratigraphic scheme based on outcrop studies and a new 39Ar/40Ar and K-Ar dating of volcanic intervals. The second is to integrate the structural kinematics deduced from the age and internal architecture of Neogene strata with two balanced cross sections to define the main pulses of fold-belt activity during the Miocene and Pliocene. Fold-belt kinematics is interpreted applying the Coulomb critical wedge model,...