Lake Chad sedimentation and environments during the late Miocene and Pliocene: New evidence from mineralogy and chemistry of the Bol core sediments - Université de Poitiers Accéder directement au contenu
Article Dans Une Revue Journal of African Earth Sciences Année : 2016

Lake Chad sedimentation and environments during the late Miocene and Pliocene: New evidence from mineralogy and chemistry of the Bol core sediments

Résumé

This study presents mineralogical and geochemical data from a borehole drilled near the locality of Bol (13°27′N, 14°44′E), in the eastern archipelago of the modern Lake Chad (Chad). Samples were taken from a ∼200 m long core section forming a unique sub-continuous record for Central Africa. Among these samples, 25 are dated between 6.4 and 2.4 Ma. Dominant minerals are clays (66% average) mixed with varying amounts of silt and diatomite. The clay fraction consists of Fe-beidellite (87% average), kaolinite, and traces of illite. Clay minerals originate from the erosion of the vertisols that surrounded the paleolake Chad. Sedimentological data indicate that a permanent lake (or recurrent lakes) existed from 6.7 until 2.4 Ma in the vicinity of Bol. By comparison with modern latitudinal distribution of vertisols in Africa the climate was Sudanian-like. Changes in the sedimentation rate suggest a succession of wetter and dryer periods during at least six million years in the region during the critical time period covering the Miocene–Pliocene transition.

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Stratigraphie
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hal-01716155 , version 1 (23-02-2018)

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Abderamane Moussa, Alice Novello, Anne-Elisabeth Lebatard, Alain Decarreau, Claude Fontaine, et al.. Lake Chad sedimentation and environments during the late Miocene and Pliocene: New evidence from mineralogy and chemistry of the Bol core sediments. Journal of African Earth Sciences, 2016, 118, pp.192-204. ⟨10.1016/j.jafrearsci.2016.02.023⟩. ⟨hal-01716155⟩
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