Mouchene M., van der Beek P., Carretier Sébastien, Mouthereau F. (2017). Autogenic versus allogenic controls on the evolution of a coupled fluvial megafan-mountainous catchment system : numerical modelling and comparison with the Lannemezan megafan system (northern Pyrenees, France). Earth Surface Dynamics, 5 (1), p. 125-143. ISSN 2196-6311.
Titre du document
Autogenic versus allogenic controls on the evolution of a coupled fluvial megafan-mountainous catchment system : numerical modelling and comparison with the Lannemezan megafan system (northern Pyrenees, France)
Mouchene M., van der Beek P., Carretier Sébastien, Mouthereau F.
Source
Earth Surface Dynamics, 2017,
5 (1), p. 125-143 ISSN 2196-6311
Alluvial megafans are sensitive recorders of landscape evolution, controlled by both autogenic processes and allogenic forcing, and they are influenced by the coupled dynamics of the fan with its mountainous catchment. The Lannemezan megafan in the northern Pyrenean foreland was abandoned by its mountainous feeder stream during the Quaternary and subsequently incised, leaving a flight of alluvial terraces along the stream network. We use numerical models to explore the relative roles of autogenic processes and external forcing in the building, abandonment and incision of a foreland megafan, and we compare the results with the inferred evolution of the Lannemezan megafan. Autogenic processes are sufficient to explain the building of a megafan and the long-term entrenchment of its feeding river on time and space scales that match the Lannemezan setting. Climate, through temporal variations in precipitation rate, may have played a role in the episodic pattern of incision on a shorter timescale. In contrast, base-level changes, tectonic activity in the mountain range or tilting of the foreland through flexural isostatic rebound do not appear to have played a role in the abandonment of the megafan.
Plan de classement
Hydrologie [062]
;
Géologie et formations superficielles [064]
