Constraining Andean Propagation of Exhumation at the Limit of the Eastern Cordillera, NW Argentina, Using Low‐Temperature Thermochronology in a Structural Context

VAN KOOTEN, WILLEMIJN S. M. T.; SOBEL, EDWARD R.; DEL PAPA, CECILIA E.; PAYROLA, PATRICIO; GLODNY, JOHANNES

TECTONICS

AMER GEOPHYSICAL UNION

Año: 2022 vol. 41

0278-7407

Within the Central Andes of NW Argentina, the spatiotemporal distribution and style ofdeformation is strongly influenced by pre-Cenozoic heterogeneities, mostly related to the Saltarift extension in the Cretaceous. At the enigmatic junction of the thin-skinned Subandean beltand the thick-skinned Santa Barbara System, the Tilcara Range and adjacent San Lucas block,located within the Eastern Cordillera, show thermochronological and field evidence of multipleexhumation events. Mesozoic (140-115 Ma), pre-Andean exhumation of basement highs isconstrained by unconformities between basement and syn-rift strata, as well as zircon (U-Th-Sm)/He cooling ages. Cenozoic Andean exhumation is quantified by apatite (U-Th-Sm)/Heand fission track cooling ages, which were reset between the Late Cretaceous and Miocene.These data show that the westernmost Tilcara Range began exhuming in the late OligoceneearlyMiocene (26-16 Ma), after which exhumation propagated to the border of the EasternCordillera in the middle Miocene (22-10 Ma). The onset of rapid exhumation in the San Lucasblock, which is located east of the Tilcara Range, occurred in the late Miocene (10-8 Ma) in itswestern part, and in the late Miocene-early Pliocene (6-4 Ma) in its eastern part. Internaldeformation of the San Lucas block, disturbing zircon (U-Th-Sm)/He and apatite fission trackage patterns, predates propagation of rapid exhumation. The here presented low-temperaturethermochronology dataset thus quantifies the multi-phase exhumation history of the EasternCordillera of NW Argentina and constrains the timing of Andean propagation of exhumationwithin the Eastern Cordillera and the adjacent structural transition zone.