72-7 Exhumation of the Chango Real in the Northern Sierras Pampeanas, Argentina

Session: Toe to Toe: Cordilleran Systems from Trench to Retroarc Domains (Posters)

Presenting Author:

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Abstract:

The timing and location of initial shortening in the Central Andes of northwestern Argentina (~26°S) remains opaque. Some suggest that deformation and exhumation started as early as Eocene time in the Eastern Cordillera possibly associated with flat-slab subduction. Initiation of basement involved uplifts in the Central Andes and growth of the Eastern Cordillera is documented by the sedimentary record preserved in the region, which suggests regional foreland basin deposition starting by Paleogene time. However, the timing of early exhumation is more challenging to resolve in the basement-involved uplifts. Low-temperature thermochronology (<300 °C) provides the time a in which a given mineral phase passes through a nominal temperature window. The apatite fission-track (AFT) and (U-Th-Sm)/He methods constrain cooling between ~120 and ~40 °C and are commonly used to document the timing of exhumation of basement rocks from ~6 to 2 km in the upper crust. In the Eastern Cordillera in the northwest of Argentina, these methods have yielded ages which are significantly older than the onset of shortening the Central Andes (>100 Ma) or associated with more recent exhumation events (<20 Ma). One area where timing of exhumation along the basement-involved uplifts is consistent with early exhumation suggested for the Eastern Cordillera of Bolivia is Chango Real in northwestern Argentina. AFT data from Chango Real suggest an onset of exhumation at ~40 Ma (Coutand et al., 2001), however, the Eocene timing is underpinned by one sample comprised of 10 single-grain ages. Here, we aim to determine the timing of exhumation initiation in the Eastern Cordillera by presenting AFT data from two samples in the Chango Real and a third sample from the El Durazno range which bounds the Corral Quemado basin. These samples will provide useful insight on the initiation of deformation in the Eastern Cordillera and timing of intra-foreland basin development in the Central Andes.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9166

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