A contribution to the quantification of crustal shortening and kinematics of deformation across the Western Andes ( ∼ 20–22° S)
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Published:2023-01-06
Issue:1
Volume:14
Page:17-42
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ISSN:1869-9529
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Container-title:Solid Earth
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language:en
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Short-container-title:Solid Earth
Author:
Habel TaniaORCID, Simoes MartineORCID, Lacassin RobinORCID, Carrizo Daniel, Aguilar GermanORCID
Abstract
Abstract. The Andes are an emblematic active Cordilleran orogen.
Mountain building in the Central Andes (∼20∘ S)
started by the Late Cretaceous to early Cenozoic along the subduction margin
and propagated eastward. In general, the structures sustaining the uplift of
the western flank of the Andes are dismissed, and their contribution to
mountain building remains poorly constrained. Here, we focus on two sites
along the Western Andes at ∼20–22∘ S in the
Atacama desert, where structures are well exposed. We combine mapping from
high-resolution satellite images with field observations and numerical
trishear forward modeling to provide quantitative constraints on the
kinematic evolution of the investigated field sites. When upscaling our
local field interpretations to the regional scale, we identify two main
structures: (1) the Andean Basement Thrust, a west-vergent thrust system
placing Andean Paleozoic basement over Mesozoic strata, and (2) a series of
west-vergent thrusts pertaining to the West Andean Thrust System, deforming
primarily Mesozoic units. From our interpreted sections, we estimate that
both structures together accommodate at least ∼6–9 km of
shortening across the sole investigated ∼7–17 km wide field
sites. This multi-kilometric shortening represents only a fraction of the
total shortening accommodated across the whole Western Andes. The timing of
the main deformation recorded in the folded Mesozoic series can be bracketed
between ∼68 and ∼29 Ma – and possibly between
∼68 and ∼44 Ma – from dated deformed
geological layers, with a subsequent significant slowing-down of shortening
rates. Even though the structures forming the Western Andes only absorbed a
small fraction of the total shortening across the whole orogen, their
contribution was relatively significant at the earliest stages of
Andean mountain building before deformation proceeded eastward.
Funder
Institut national des sciences de l'Univers Institut de Physique du Globe de Paris Centro Avanzado de Tecnología para la Minería Agence Nationale de la Recherche
Publisher
Copernicus GmbH
Subject
Paleontology,Stratigraphy,Earth-Surface Processes,Geochemistry and Petrology,Geology,Geophysics,Soil Science
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