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Longitudinal to transverse drainage network evolution in the High Atlas (Morocco): The role of tectonics
Author(s) -
Babault Julien,
Van Den Driessche Jean,
Teixell Antonio
Publication year - 2012
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2011tc003015
Subject(s) - geology , fluvial , transverse plane , tectonics , geomorphology , lithosphere , rift , crust , paleontology , graben , basin and range topography , seismology , structural basin , structural engineering , engineering
The High Atlas of Morocco is a still‐active, linear intracontinental mountain chain in the NW African plate, which results from weak crustal thickening associated with rift inversion during the Cenozoic and from uplift related to mantle thermal doming. A striking morphological feature of the High Atlas is the occurrence of both transverse and longitudinal (i.e., strike‐parallel) drainage characterized by deep fluvial incision of more than 1000 m in low‐relief topography of the axial zone of the chain. Most of the transverse component of the drainage appears to postdate the longitudinal component as indicated by recent or incipient captures and wind gaps. The longitudinal drainage is inherited from an early stage of fluvial organization controlled by the tectonic structures developed during upper crustal folding and thrusting in the post‐Paleozoic cover. Amplification of N‐S regional slope in the western High Atlas by continued crustal shortening and thickening triggered: (i) higher erosion rates in transverse than in longitudinal catchments and (ii) captures of longitudinal streams by transverse ones, creating a new organization of the drainage system toward the regional slope. Such evolution from a longitudinal to a transverse‐dominated drainage may represent a common mechanism of fluvial network development in mountain belts where the amplification of the regional slope results from long‐lived lithospheric convergence.