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Étude de l'enregistrement minéralogique des événements paléoclimatiques dans les sols tropicaux : nouveaux apports de la datation de kaolinites par irradiations expérimentales

Abstract : Laterites are covering a third of the continental surfaces. Understanding their evolution through the ongoing climate change is critical to predict the future Critical Zone transformation. Laterite duricrusts can contain several generations of secondary minerals that can be correlated with distinct paleoclimatic events. Isotopic studies showed that loose laterites may also be formed by several generations of secondary minerals. The objective of this PhD was to confirm that loose laterites contain several generations of kaolinites and that they formed during regional and/or global paleoclimatic events. With this aim in view, a recent dating methodology, the Electron Paramagnetic Resonance dating of kaolinites, was used on tropical regolith profiles from three continents with distinct geodynamic histories: India (Karnataka plateau), South America (Rio Negro basin, Brazil) and Australia (Syerstone region, New South Wale). The data set of this PhD confirms that a regolith contains several generations of kaolinites. All the identified generations of the present study can be correlated with regional paleoclimatic events or with tropical weathering favourable periods initiated by global paleoclimatic trends. Kaolinite generations formed preferentially during high precipitations periods and result from the rejuvenation of laterite profiles. The results of this PhD confirm that laterites have an episodic evolution.
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Maximilien Mathian. Étude de l'enregistrement minéralogique des événements paléoclimatiques dans les sols tropicaux : nouveaux apports de la datation de kaolinites par irradiations expérimentales. Sciences de la Terre. Sorbonne Université, 2018. Français. ⟨NNT : 2018SORUS161⟩. ⟨tel-02340919⟩

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