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Communication dans un congrès

Paleohydrology of meandering systems : a new approach for the reconstruction of ancient drainage aeras and the quantification of the controlling factors

Abstract : In meandering system fluvial sedimentology, studying infill geometries and sedimentary structures of channelized sandstone bodies, gives information about the sedimentary dynamic and the depositional environment. Associated with such a sedimentary approach, paleohydrology enables the reconstruction of hydrological parameters such as discharge, drainage area or stream length. Although fluvial systems are known to be influenced by allogenic and/or autogenic processes, climate or structural evolution were not taken into account in previous paleohydrological studies. Therefore, the present study attempts to develop a new method of paleohydrological reconstitution, based on the geometry of fluvial sandstone bodies and constrained by the controlling factors (climate and tectonic). We selected two meandering systems of the same age, developed under different climatic setting: the first one is located in the Alpine Foreland Basin (SE France) and was associated to a subtropical humid realm; the second one is situated in the Loranca Basin (Central Spain) and was related to subtropical semi-arid conditions. Dealing with the uniformitarianism concept, we developed a new method to determine the paleohydrological parameters of the two different systems. For each of these two climatic setting we have constructed an equivalent modern rivers database taking into account their respective climatic conditions. By defining empirical relations, we translated the point-bar thickness (the only data available in the field) into paleohydrological parameters, such as channel geometry, water discharge and basin geometry. Because fluvial members studied are composed of several channelized sequences; each of them gives a specific drainage area depending on discharge value and climatic coefficient. But assuming a constant basin area all along the river evolution, we can quantify the spatiotemporal impact of the climate on the development of an alluvial system. Furthermore, granulometry, orientation of the lateral accretion surface and geometry of sandstone bodies are controlled by the variations of basin slope. Channel deposits record the basement modifications due to tectonic response. The use of a sedimentological and paleohydrological approach allows us to quantify the impact of tectonic on the evolution of a stream. By combining both the impacts of climate and tectonic we aim to determine to which controlling factors an alluvial system is the most sensitive. This research attempts to create a new method to predict cautiously the evolution of a drainage basin
keyword : Hydrology Modeling
Type de document :
Communication dans un congrès
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https://hal-mines-paristech.archives-ouvertes.fr/hal-00568780
Contributeur : Pascale Nalon <>
Soumis le : mercredi 23 février 2011 - 14:42:19
Dernière modification le : mercredi 14 octobre 2020 - 03:52:25

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  • HAL Id : hal-00568780, version 1

Citation

Anne-Edwige Held, Isabelle Cojan. Paleohydrology of meandering systems : a new approach for the reconstruction of ancient drainage aeras and the quantification of the controlling factors. American Geophysical Union, Fall Meeting 2009, Dec 2009, San Francisco, United States. 1p. ⟨hal-00568780⟩

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