Journal
TECTONICS
Volume 35, Issue 11, Pages 2636-2656Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2016TC004225
Keywords
Patagonia; low-temperature thermochronology; exhumation; AHe dating; broken foreland; Chubut
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Funding
- University of Padova [CPDA158355]
- University of Naples Federico II (Fondi Ricerca Dipartimentale)
- Universidad Nacional de Rio Negro [PICT-FONCyT 2013-2916, PIP-CONICET 330]
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The Patagonian Andes represents a unique natural laboratory to study surface deformation in relation to deep slab dynamics. In the sector comprised between latitudes 41 degrees 30 and 43 degrees S, new apatite (U-Th)/He ages indicate a markedly different unroofing pattern between the broken foreland area (characterized by Late Cretaceous to Paleogene exhumation) and the adjacent Andean sector to the west, which is dominated by Miocene-Pliocene exhumation. These unroofing stages can be confidently ascribed to inversion tectonics involving reverse fault-related uplift and concomitant erosion. Late Cretaceous-Paleogene shortening and exhumation are well known to have affected also the thrust belt sector of the study area during a prolonged stage of flat-slab subduction. Therefore, the different ages of near-surface unroofing documented in this study suggest coupling of the deformation between the thrust belt and its foreland during periods of flat-slab subduction (e.g., during Late Cretaceous-Paleogene times) and dominant uncoupling during periods of steep-slab subduction and rollback, even when these are associated with high convergence rates (i.e., > 4cm/yr), as those documented in Miocene times for the Patagonian Andes.
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