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Communication dans un congrès

Chemical weathering and erosion rates in Lesser Antilles: an overview in Guadeloupe, Martinique and Dominica

Abstract : Guadeloupe, Martinique and Dominica Islands alike numerous tropical environment present extreme weathering regimes. Physical denudation is mainly controlled by landside, This reflects the torrential dynamics of the rivers. For Guadeloupe, the mechanical weathering rates are 800-4000 t/km2/yr. The lithology is very porous with high infiltration rates, which induces that most of the elements fluxes are produced on subsurface as the chemical erosion rates are 2 to 5 time higher than the rates from surface water. We show how kinetic of chemical weathering rates depends on the age of the lava and subsurface circulation. In addition, timescale of erosion have been calculated from U-series analyses sediments from rivers. Our results show a large range: from 0 to 150 ka in Martinique and from 0 to 60 ka Guadeloupe. From analyses from the dissolved loads, we propose to evaluate residence times in the river water. It would appear that waters circulation is globally 3 times longer for subsurface water than for surficial water (Rad et al., 2011). Moreover these islands are highly impacted by agriculture. It is therefore interesting to assess the impact of such influence on the weathering rates. Our result show that human activity brings no disturbance on Critical zone processes contrary to what one might think. Indeed, we show that among the combined impact of all parameters (climate, runoff, slopes, vegetation...), the basins age seems to be the control parameter on chemical weathering and land use: the younger the basin, the higher the weathering rate. We could observe a combined effect between the higher erodibility and a higher climate erosivity of the younger reliefs.
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https://hal-brgm.archives-ouvertes.fr/hal-00597310
Contributeur : Sétareh Rad <>
Soumis le : mardi 31 mai 2011 - 15:20:38
Dernière modification le : mercredi 3 juin 2020 - 06:06:02

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  • HAL Id : hal-00597310, version 1

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Sétareh Rad, Karine Rivé, Olivier Cerdan, Benoit Vittecoq, Claude J. Allègre. Chemical weathering and erosion rates in Lesser Antilles: an overview in Guadeloupe, Martinique and Dominica. Goldschmidt Conference 2011, Aug 2011, Orléans, France. pp.1686. ⟨hal-00597310⟩

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