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Exhumation du prisme collisionnel Ouest Alpin et évolution du bassin molassique : nouvelles données thermochronologiques et tectono-sédimentaires

Abstract : New thermochronological data (AFT, ZHe, and ZFT) on the Belledonne and Grandes Rousses ECMs basement show a similar and relatively rapid exhumation dynamic around 18 Ma for all the External Cristalline Massifs. However, the exhumation of southern massifs (e.g., Oisans) could start earlier, from 25 Ma suggesting a diachronous exhumation along the Alpine Arc. This also suggests a progressive localization of deformations along the crustal ramps between ~25 and 18 Ma. Finally, the rapid exhumation starting at around 18 Ma seems to correspond to the limit of mega-sequences in the molassic basin. Field analysis, borehole data and seismic lines show that the basin was deformed as early as the Oligocene (25 Ma). This also allows the calculation of the sediment volumes preserved within the West Alpine Molassic Basin. Finally, a preliminary study of the source to sink in the West Alpine basins is approached from petro-detritic analyses, detrital thermochronology and calculation from the seismic lines. These results highlighted the progressive denudation of the Variscan crust of the upper plate whose detrital signal has been present since the Eo-Oligocene in the peri-alpine basins. The late Miocene appearance in the West Alpine Molassic basin of a tertiary thermochronological signal suggests a change in surface dynamics and/or a different sedimentary routing over time, but also significant differences compared to the basins located north of the Alps.
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  • HAL Id : tel-03372619, version 1

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Jean-Baptiste Girault. Exhumation du prisme collisionnel Ouest Alpin et évolution du bassin molassique : nouvelles données thermochronologiques et tectono-sédimentaires. Sciences de la Terre. Sorbonne Université, 2020. Français. ⟨NNT : 2020SORUS086⟩. ⟨tel-03372619v1⟩

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