Grimaud J.L., Chardon D., Beauvais Anicet. (2014). Very long-term incision dynamics of big rivers. Earth and Planetary Sciences Letters, 405, p. 74-84. ISSN 0012-821X.
Titre du document
Very long-term incision dynamics of big rivers
Année de publication
2014
Type de document
Article
Auteurs
Grimaud J.L., Chardon D., Beauvais Anicet
Source
Earth and Planetary Sciences Letters, 2014,
405, p. 74-84 ISSN 0012-821X
Constraining large-scale incision dynamics of shield and post-rift margin domains is key to understanding the sediment routing system over the overwhelming part of the continental surface. Based on dated and regionally correlated incision markers from West Africa, we reconstruct for the first time the entire paleo-long profiles of big rivers such as the Niger at ca. 24, 11 and 6 Ma, as well as the Eocene topography those rivers have dissected. The results provide boundary conditions and calibration for surface process models and paleodrainage dynamics. Though spatially and temporally variable, incision remained mostly below 10 m/mywith a mean around 5 m/my. The spatial stability of both the river outlets and divides imposed maintenance or increasing concavity of the river long profiles through time, resulting from spatially contrasted adjustment of river segments bounded by recurrent lithogenic knickzones that persisted since 24Ma. Drainages evolved preferentially by very slow slope decrease or uniform incision in between the stationary knickzones of evolving amplitude, with apparently no relation to base level change. Therefore, knickzone height or position may not simply reflect the transient response of big rivers to base level fall as predicted by stream-power incision river models. This may also challenge uplift histories of deep continental interiors retrieved from river long profiles inversion relying on such models. Very slow incision allowed amplification of the Hoggar hot spot swell and flexural uplift of the continental margin to be recorded by river long profiles, emphasizing the potential of big non-orogenic rivers as gauges of dynamic topography. (Résumé d'auteur)
Plan de classement
Evaluation et gestion des ressources en eau [062EVAEAU]
;
Géomorphologie [064GEOMOR]
Descripteurs
PALEOGEOMORPHOLOGIE ; DYNAMIQUE ; COURS D'EAU ; CONFIGURATION DU LIT ; SEDIMENTATION FLUVIATILE ; TOPOGRAPHIE ; EOCENE ; CENOZOIQUE ; MODELISATION ; VARIATION SPATIALE ; VARIATION TEMPORELLE ; DRAINAGE ; NIVEAU DE L'EAU ; TECTONIQUE ; PROFIL EN LONG ; INCISION ; ETALONNAGE ; PALEODRAINAGE ; LITHOGENESE
