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

Lugar: Amsterdam; Año: 2017 vol. 99 p. 1 - 19

0191-8141

Superposed structural fabrics in the easternmost Fuegian Andesreveal two distinct, non-coaxial deformation phases across the transitionfrom the orogenic core to the thrust-fold belt. Each phase ischaracterized by different metamorphic conditions and consistentlydifferent orientations, which allow the structural correlation betweenthe orogenic core and the internal thrust-fold belt. The firstdeformation phase was coeval with regional metamorphism reaching uppergreenschist facies, and featured simple shear deformation of the basement(Paleozoic and Jurassic) and cover (Cretaceous) in the top of theunderthrusting South American plate. The second phase developed duringcollision of the orogenic wedge with the Río Chico Arch, a promontory inthe underthrusting plate; this phase was characterized by thrust sheetemplacement and formation of a crustal duplex, with rock uplift andconsequent low to very-low grade metamorphism. Buttressing against theRío Chico Arch is responsible for the change in shortening orientationthat distinguishes both phases.