Hindered Trench Migration Due To Slab Steepening Controls the Formation of the Central Andes
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2022-12
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Journal Article
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Abstract
The formation of the Central Andes dates back to ∼50 Ma, but its most pronounced episode, including the growth of the Altiplano-Puna Plateau and pulsatile tectonic shortening phases, occurred within the last 25 Ma. The reason for this evolution remains unexplained. Using geodynamic numerical modeling we infer that the primary cause of the pulses of tectonic shortening and growth of the Central Andes is the changing geometry of the subducted Nazca plate, and particularly the steepening of the mid-mantle slab segment which results in a slowing down of the trench retreat and subsequent increase in shortening of the advancing South America plate. This steepening first happens after the end of the flat slab episode at ∼25 Ma, and later during the buckling and stagnation of the slab in the mantle transition zone. Processes that mechanically weaken the lithosphere of the South America plate, as suggested in previous studies, enhance the intensity of the shortening events. These processes include delamination of the mantle lithosphere and weakening of foreland sediments. Our new modeling results are consistent with the timing and amplitude of the deformation from geological data in the Central Andes at the Altiplano latitude.
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127 (12)
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American Geophysical Union
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Subject
Central Andes; Subduction dynamics; Geodynamics; Shortening; Steepening; Flat-Slab