Fueguian Andes foreland fold and thrust belt: structure and growth strata.

Abstract

Foreland basin deposits involved in the Fueguian foreland fold and thrust belt were studied on the Atlantic coast of Tierra del Fuego. More specifically, growth strata developed in middle Eocene sequences deposited in the wedge top depozone were analyzed. Restoration methods and kinematics forward modeling were applied, revealing folding kinematics and defining the geometry of the structure at various stages in its geological history. The folded units are characterized by strong competency contrasts and display a transition in deformation behavior from detachment folding to progressive fault propagation with increasing shortening. The evolution of this sector can be summarized in two different tectonic pulses: (1) lower to middle Eocene: development of detachment folding with limb rotation; sedimentation rate was always lower relative to fold growth rate and both of them decreased with time. (2) upper Eocene?-Oligocene: Continued shortening resulted in the propagation of thrust faults through competent units on the steep front limb and the migration northward of the foreland basin system; probably related to generalized wrench kinematics which affected the region.