Progressive deformation of a Coulomb thrust-wedge: the eastern Fuegian Andes thrust-fold belt.

PABLO TORRES CARBONELL; LUIS DIMIERI; EDUARDO OLIVERO

Geological Society of London Special Publications

Geological Society of London

Lugar: London; Año: 2011 vol. 349 p. 123 - 147

0305-8719

Time-calibrated balanced-cross sections of the eastern Fuegian Thrust-Fold Belt reveal many complex pro- and retro-vergent structures, rooted at the base of the upper Paleocene. These structures involve the unconformity-bounded syntectonic sequences of the Austral foreland basin, and accommodate a minimum shortening of c. 41.8 km. The complex and progressive kinematics of the thrust-fold belt are recorded by 1) propagation of the basal décollement into the foreland, and forward-directed thrusting during the Ypresian; 2) out-of-sequence thrusting in the Lutetian; 3) subsidence and sedimentation from the late Lutetian to the Oligocene; 4) backthrusting during the Oligocene; and 5) a renewed stage of forward-directed thrusting between the latest Oligocene and the early Miocene, probably related to accretion below the sole fault in the hinterland. This thrust sequence is interpreted as the result of a critical Coulomb wedge behavior during the first stage of thrust-fold belt expansion, with accretion of new material that led to a taper decrease. The subsequent period of internal deformation corresponds to a subcritical stage, during which backthrusting accommodates significant shortening (c. 15%). After growth and taper increase, the last period of forward thrusting at the wedge’s front marks the inception of a new critical stage.