Structural and thermochronological constraints on the exhumation of the Chos Malal fold and thrust belt (~37º S)

SÁNCHEZ NATALIA; TURIENZO MARTÍN; COUTAND ISABELLE; FERNANDO, LEBINSON; ARAUJO VANESA; DIMIERI LUIS

Opening and closure of the Neuquén Basin in the Southern Andes

Springer

Año: 2020; p. 323 - 340

This chapter reviews the evolution of the Chos Malal fold and thrust belt based onstructural and thermochronological data. This mountain belt can be divided intoan inner zone, characterized by exposed basement-involved structures that areinserted in the sedimentary cover and generated a wide region with thin-skinneddeformation, and an outer zone where blind thrusts involving basement rocksproduce deformation in the cover restricted to the deformation front where themain hydrocarbon deposits of the region are located. Zircon (U-Th)/He and apatitefission track cooling ages at the Cordillera del Viento, ranging from 72 Ma to 51 Ma, evidence a period of uplift and exhumation in the inner zone during the LateCretaceous-Paleocene. These data are in agreement with the notable unconformityobserved between Paleogene volcanics and Paleozoic basement rocks. Thecontraction in this zone continued during the Miocene giving rise to most ofthe thick and thin-skinned structures of the Chos Malal fold and thrust belt,as reveled by apatite fission tracks ages between 15-10 Ma. Furthermore, folded volcanic sequences with 40Ar/39Ar ages of 15Ma and intrusive rocks with U-Pb ages of 11.5 Ma coeval with the folding evidencethis compressive episode. The deformation advanced towards the foreland duringthe Late Miocene, where samples from the basement-involved Las Yeseras-PampaTril anticlines show apatite fission tracks ages of 9-7 Ma, which led to the uplift and exhumation of theouter zone of the Chos Malal fold and thrust belt.