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ABSTRACT
The North Chilean coast is marked by three first-order morphological features that allow
us to document precisely the deformation of the andean subduction margin since the Late
Miocene : (1) a set of steep, 1-km-deep canyons incised in (2) the Pampa del Tamarugal
plateau, a 1000-m-high surface of combined origin (erosion and sedimentation) which is now in
hanging position and limited to the West by (3) the 1-km-high and 700-km-long Coastal Scarp.
A detailed study of the morphology and the geology of the area combined with analysis of
the drainage allows us to characterize the morpho-tectonic evolution of the Andean Marginal
Block for the past 10 million years. The relative 1000-m high base-level change would result
from recent and active tectonic uplift of the relatively rigid Marginal Block. We test this
hypothesis by modelling the landscape evolution using a numerical approach (code APERO).
Our results suggest continuing tectonic deformation and thickening of the subduction margin
probably associated with strong mechanical coupling across the subduction thrust interface.
Since a few million years the Andes orogen appears to have grown westwards, towards the
subduction zone, by incorporating the Marginal Block to the mountain building process.
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