Thrust-fold belt kinematics and orogenic growth in Tierra del Fuego, Argentina: implications of backthrusting for critical Coulomb wedge development

Abstract

Analysis of balanced cross-sections and of the chronostratigraphy of the deformed foreland basin successions allows to solve the structural kinematics of the eastern Fuegian thrust-fold belt. Based on the Coulomb wedge theory, we propose a chronologically and geometrically well-constrained growth history for the frontal Fuegian Andes orogen. The mountain front behaved in a critical manner during the Early Eocene, characterized by forward thrusting. The wedge became subcritical after that, until renewed forward propagation of the thrust front in the Early Miocene. The long period as a subcritical wedge enhanced retrodeformation, recorded by out-of-sequence thrusting and backthrusting. We suggest that backthrusts should be considered an important mechanism for accommodating shortening in subcritical orogenic wedges.