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

2016

Article référencé dans le Web of Science WOS:000378434500016

Moussa A., Novello A., Lebatard A. E., Decarreau A., Fontaine C., Barboni D., Sylvestre Florence, Bourles D. L., Pailles C., Buchet G., Duringer P., Ghienne J. F., Maley J., Mazur J. C., Roquin C., Schuster M., Vignaud P., Brunet M.

Journal of African Earth Sciences, 2016, 118, p. 192-204 ISSN 1464-343X

This study presents mineralogical and geochemical data from a borehole drilled near the locality of Bol (13 degrees 27'N, 14 degrees 44'E), in the eastern archipelago of the modern Lake Chad (Chad). Samples were taken from a similar to 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.

Géologie et formations superficielles [064] ; Pédologie [068]

TCHAD

Fonds IRD [F B010067631] ; Niamey (LASDEL)

fdi:010067631