Structural and Thermochronological Constraints on the Exhumation of the Chos Malal Fold and Thrust Belt (~37° S)

SÁNCHEZ NATALIA; TURIENZO, MARTÍN; COUTAND, ISABELLE; LEBINSON, FERNANDO; 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 thrustbelt based on structural and thermochronological data. This fold and thrust belt canbe divided into an inner-western zone, characterized by exposed basement-involvedstructures that are inserted in the sedimentary cover and generated a wide region withthin-skinned deformation, and an outer-eastern zone, where blind thrusts, involvingbasement rocks, produce deformation in the cover restricted to the deformation frontwhere the main hydrocarbon deposits of the region are located. Zircon (U?Th)/Heand apatite fission-track cooling ages at the Cordillera del Viento, ranging from 72 to51 Ma, evidence a period of uplift and exhumation in the inner zone during the LateCretaceous?Paleocene. These data are in agreement with the notable unconformityand hiatus observed between Paleogene volcanics and Paleozoic basement rocks.The contraction in this zone continued during theMiocene giving rise to most of thethick and thin-skinned structures of the Chos Malal fold and thrust belt, as revealedby apatite fission-track ages between ~15 and 10 Ma. Furthermore, folded volcanicsequences with 40Ar/39Ar ages of ~15 Ma and intrusive rocks with U?Pb ages of11.5 Ma evidence this compressive episode. The deformation advanced toward theforeland during the Late Miocene, where samples from the basement-involved LasYeseras?Pampa Tril anticlines show apatite fission-tracks ages of ~9?7 Ma, whichled to the uplift and exhumation of the outer zone of the Chos Malal fold and thrustbelt.