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

NATALIA P. SÁNCHEZ; MARTIN TURIENZO; ISABELLE COUTAND; FERNANDO LEBINSON; VANESA S. ARAUJO; LUIS V. DIMIERI

Opening and closure of the Neuquén Basin in the Southern Andes

Springer

Año: 2020; p. 323 - 340

This chapter reviews the evolution of the ChosMalal fold and thrust belt based on structural and thermochronological data.This mountain belt can be divided into an inner zone, characterized by exposedbasement-involved structures that are inserted in the sedimentary cover andgenerated a wide region with thin-skinned deformation, and an outer zone whereblind thrusts involving basement rocks produce deformation in the coverrestricted to the deformation front where the main hydrocarbon deposits of theregion are located. Zircon (U-Th)/He and apatite fission track cooling ages atthe Cordillera del Viento, ranging from 72 Ma to 51 Ma, evidence a period ofuplift and exhumation in the inner zone during the Late Cretaceous-Paleocene.These data are in agreement with the notable unconformity observed betweenPaleogene volcanics and Paleozoic basement rocks. The contraction in this zonecontinued during the Miocene giving rise to most of the thick and thin-skinned structuresof the Chos Malal fold and thrust belt, as reveled by apatite fission tracks agesbetween ~15 -10 Ma. Furthermore, folded volcanicsequences with 40Ar/39Ar ages of ~15 Ma and intrusiverocks with U-Pb ages of 11.5 Ma coeval with the folding evidence thiscompressive episode. The deformation advanced towards the foreland during theLate Miocene, where samples from the basement-involved Las Yeseras-Pampa Tril anticlinesshow apatite fission tracks ages of ~9-7 Ma, which led to the uplift and exhumationof the outer zone of the Chos Malal fold and thrust belt.