Structure and tectonic evolution of the North Patagonian fold and thrust belt

ECHAURREN, ANDRÉS; GIANNI, GUIDO; FERNÁNDEZ PAZ, LUCÍA; NAVARRETE, CÉSAR R.; OLIVEROS, VERÓNICA; ENCINAS, ALFONSO; GIMENEZ, M; LINCE-KLINGER, F.; FOLGUERA, ANDRÉS

Andean Tectonics

Elsevier

Lugar: Ámsterdam; Año: 2019;

The North Patagonian fold-thrust belt at ~43º S is characterized as a thick-skinned deformational 14 system that includes both a retroarc series of eastward directed thrusts and an intraplate belt formed 15 by the inversion of the Cañadón Asfalto rift system. Together, these structural domains define a 16 wide system characterized by reduced topography, crustal thickness and shortening values. Analysis 17 of Mesozoic-Cenozoic evolutionary stages at these latitudes reveals the alternation of extensional 18 and contractional pulses that highlights the dominating role of distinctive mechanisms of interaction 19 between the continent and the different oceanic plates involved through Andean development. In 20 this sense, two main orogenic stages in late Early Cretaceous-early Paleocene and middle-late 21 Miocene time were preceded by protracted extensional phases characterized by abundant 22 magmatism across the margin. These pre-orogenic extensional phases exerted a thermal weakening 23 and lithospheric softening effect necessary for propagation of deformation in the following 24 contraction episodes. Contrastingly, while Cretaceous contraction was associated with a flat-slab 25 episode and the Neogene contraction would be associated with no major changes in the subduction 26 geometry. Propagation of deformation in both cases was arrested by the southwestern edge of the 27 North Patagonian Massif, interpreted as a heralded lithospheric anisotropy that has acted as a long-28 lived mechanical barrier.