Uplift and denudation history at low-elevation passive margins: Insights from morphostratigraphic analysis in the SE Armorican Massif along the French Atlantic margin |
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Authors: | François Bétard |
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Institution: | Laboratoire de géographie physique, UMR 8591-CNRS, université Paris-Est Créteil (UPEC), 61, avenue du Général-de-Gaulle, 94010 Créteil cedex, France |
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Abstract: | Like other low-elevation passive margins, the French Atlantic margin is characterized by a gradual topographic transition from the coast to low-altitude interior plains or plateaus. Here we propose a morphostratigraphic analysis to constrain long-term landscape evolution and denudation rates, through the characterization of palaeotopographies and related palaeoweatherings in an area restricted to the southeast Armorican Massif. Two regional-scale palaeosurfaces are recognized: (i) the Infraliassic palaeosurface, the truncated weathering profiles of which are sealed by Liassic marine deposits; (ii) the Eocene palaeosurface, underlain by thick kaolinite- and iron-rich palaeosaprolites and by siliceous duricrusts (silcretes). Quantitative constraints on large-scale tectonic uplift and long-term denudation are obtained from these morphostratigraphic markers. Mean uplift and denudation rates calculated on post-Eocene times range between 0.5 and 2 m.Ma-1. These low values imply high landscape stability of the inland margin over most of the Cenozoic. |
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Keywords: | Palaeolandforms Palaeosaprolites Tectonic uplift Denudation rates Morphostratigraphy Passive margins Armorican Massif France |
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