(Un)Coupled thrust belt-foreland deformation in the northern 1 Patagonian Andes: 2 new insights from the Esquel-Gastre sector (41°30??43° S)

MARTÍN ARCE; MARCELO PAOLINI; SAVIGNANO, ELISA; MARTA FRANCHINI; STEFFANO MAZOLI; MASSIMILIANO ZATTIN; CECILE GAUTHERON

TECTONICS

AMER GEOPHYSICAL UNION

Año: 2016 vol. 35 p. 2636 - 2656

0278-7407

The Patagonian Andes represent a unique natural laboratory to study surface deformation in relation to deep slab dynamics. In the sector comprised between latitudes 41°30? and 43°S, new apatite (U-Th)/He ages indicate a markedly different unroofing pattern between the ?broken foreland? area (characterized by Late Cretaceous to Paleogene exhumation) and the adjacent Andean sector to the west, which is dominated by Miocene-Pliocene exhumation. These unroofing stages can be confidently ascribed to inversion tectonics involving reverse fault32related uplift and concomitant erosion. Late Cretaceous-Paleogene shortening and exhumation are well known to have affected also the thrust belt sector of the study area during a prolonged stage of flat-slab subduction. Therefore, the different ages of near-surface unroofing documented in this study suggest coupling of the deformation between the thrust belt and its foreland during periods of flat-slab subduction (e.g. during Late Cretaceous-Paleogene times), and dominant uncoupling during periods of steep-slab subduction and rollback, even when these are associated with high convergence rates (i.e. > 4 cm/year), as those documented in Miocene times for the Patagonian Andes.