Spatial and temporal characterization of progressive deformation during orogenic growth: Example from the Fuegian Andes, southern Argentina

TORRES CARBONELL, PABLO J.; CAO, SEBASTIÁN J.; DIMIERI, LUIS V.

JOURNAL OF STRUCTURAL GEOLOGY

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2017 vol. 99 p. 1 - 19

0191-8141

Superposed structural fabrics in the easternmostFuegian Andes reveal two distinct, non-coaxial deformation phases across thetransition from the orogenic core to the thrust-fold belt. Each phase ischaracterized by different metamorphic conditions and consistently differentorientations, which allow the structural correlation between the orogenic coreand the internal thrust-fold belt. The first deformation phase was coeval withregional metamorphism reaching upper greenschist facies, and featured simpleshear deformation of the basement (Paleozoic and Jurassic) and cover(Cretaceous) in the top of the underthrusting South American plate. The secondphase developed during collision of the orogenic wedge with the Río Chico Arch,a promontory in the underthrusting plate; this phase was characterized bythrust sheet emplacement and formation of a crustal duplex, with rock upliftand consequent low to very-low grade metamorphism. Buttressing against the RíoChico Arch is responsible for the change in shortening orientation thatdistinguishes both phases.