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

Within the Central Andes of NW Argentina, the spatiotemporal distribution and style of deformation is strongly influenced by pre-Cenozoic heterogeneities, mostly related to the Salta rift extension in the Cretaceous. At the enigmatic junction of the thin-skinned Subandean belt and 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 multiple exhumation events. Mesozoic (140-115 Ma), pre-Andean exhumation of basement highs is constrained 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)/He and 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 Oligocene-early Miocene (26-16 Ma), after which exhumation propagated to the border of the Eastern Cordillera in the middle Miocene (22-10 Ma). The onset of rapid exhumation in the San Lucas block, which is located east of the Tilcara Range, occurred in the late Miocene (10-8 Ma) in its western part, and in the late Miocene-early Pliocene (6-4 Ma) in its eastern part. Internal deformation of the San Lucas block, disturbing zircon (U-Th-Sm)/He and apatite fission track age patterns, predates propagation of rapid exhumation. The here presented low-temperature thermochronology data set thus quantifies the multi-phase exhumation history of the Eastern Cordillera of NW Argentina and constrains the timing of Andean propagation of exhumation within the Eastern Cordillera and the adjacent structural transition zone.

Automated summary

In the Central Andes of NW Argentina, the distribution and style of deformation is strongly influenced by pre-Cenozoic heterogeneities, particularly related to the Salta rift extension in the Cretaceous. The Tilcara Range and San Lucas block in the Eastern Cordillera exhibit evidence of multiple exhumation events. Through low-temperature thermochronology data set, the multi-phase exhumation history of the Eastern Cordillera of NW Argentina is quantified.