The role of climate during high plateau formation. Insights from numerical experiments

High plateaus are elevated areas of low relief mostly associated with compressional tectonics and characterized by dry climatic conditions. Results from a novel computer modeling technique integrating surface and tectonic processes suggest that a preexisting dry climate, through its effects on surface transport and orogenic evolution, can significantly contribute to the formation of high plateaus. According to these results, dry climatic conditions promote sediment trapping within the orogen, transferring the accommodation of tectonic shortening towards the external parts of the orogen and leading to the formation of a high plateau. This feedback operates in the following steps: (1) dry climatic conditions at the early stages of orogenesis favor the tectonic defeat of rivers draining the orogen, promoting internal drainage (endorheism); (2) endorheism extends the life of intramountain basins maximizing the mass trapped within the orogen and expelling deformation further into the foreland; and (3) this propagation of deformation further isolates the central parts of the orogen from incoming precipitation, reinforcing sediment trapping and topographic leveling of the intramountain region. This phenomenon allows reproduction of basic topographic, drainage, and tectonic differences between orogens lacking a high plateau, such as the Alps, and orogens with a well-developed high plateau like the Andes, without invoking inherited heterogeneities in the crust or other tectonic processes. It also suggests that internal drainage and high plateaus might be a natural stage of orogenesis undergoing dry climatic conditions. In the light of recent data reporting dry climate prior to the formation of the Andean high plateau, aridity can be seen as one of the causes for the formation of the Altiplano, rather than just as a consequence of topographic growth. (c) 2007 Elsevier B.V. All rights reserved.