Tectonic evolution of the Chos Malal fold-and-thrust belt (Neuquén Basin, Argentina) from (U-Th)/He and fission-track thermochronometry

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

TECTONICS

AMER GEOPHYSICAL UNION

Año: 2018

0278-7407

In the southern CentralAndes at 37-38 °S latitude, the Chos Malal fold-and-thrust belt (FTB), whichresults from the Late Cretaceous closure of the Neuquén Basin, has generatedincreasing interest because of its potential for hydrocarbon exploration. Usingdetailed field mapping, seismic reflection, well data analysis, we haveproduced balanced cross- sections, which combined with apatite and zircon(U-Th) /He, and fission-track thermochronology from samples distributed alongthe FTB, bring new constraints on the chronology of the structural developmentof the Chos Malal FTB. Fully reset samplesobtained from the Early Jurassic rocks at the bottom of the sedimentarysequence exposed in the Cordillera del Viento, a major basement-involvedhinterland structure, permit to quantify its cooling rate from 5.4 ± 4.1 and 3.8± 3.2 °C/Ma between 70-55 Ma down to between 2.0 ± 1.3 and 1.3 ± 0.9 °C/Maafter 55 Ma until the present. Detrital AFT ages from Late Jurassic and EarlyCretaceous sandstones reveals that tectonically-driven exhumation throughbasement-involved thrusting has occurred at ~15-7 Ma in both the inner andouter sectors of the FTB. Finally, the cooling and exhumation of the LasYeseras-Pampa Tril basement-involved anticlines at the mountain front at ~ 9-7Ma, slightly younger than previously assumed, suggests a normal sequence offaulting propagation. Our proposed thermo-structural model of the Chos MalalFTB contributes to a better understands of the tectonic evolution of thissegment of the Andes.