Peat in the Niayes of Senegal: depositional environment and Holocene evolution - Université Pierre et Marie Curie Accéder directement au contenu
Article Dans Une Revue Journal of African Earth Sciences Année : 1991

Peat in the Niayes of Senegal: depositional environment and Holocene evolution

J.-J. Chateauneuf
  • Fonction : Auteur

Résumé

The "Niayes" peat deposits north of Dakar, in Senegal, provide an unusual opportunity to study the continental and littoral detrital environment of the Holocene in West Africa. These organic deposits, that may attain a thickness of 10m, accumulated in Late Pleistocene interdune basins whose extend morphology depend closely upon the palaeohydrologic evolution of and the continental model for this zone during the Holocene. The present sub-Canarian climate of this region allows the preservation of an azonal vegetation of Guinean chorological affinity that is evidence of the wider development of now more southerly vegetation during the older Holocene. The nature of the sedimentary facies of these peatfields is closely related to the altitude of the basins of accumulation and the position of the fresh/salt water interface which conditions the recharge of the shallow aquifer. Thus, fresh-water and mangrove-swamp peats exist more or less closely associated according to the site. 14C age determinations gives ages for these deposits between 12000 B.P. and the present, and detailed palynological studies have shown that there were two periods of climatic optimum, one between 9000 and 7000 B.P. and one between 4000 and 2000 B.P. The highly variable rates of sedimentation (0.2-12,5 mm/y for the continental zones and 2 mm/y for the mangrove swamps) are related to the paleotopography of the water-table or to very local fluctuations of sea level. The evolution of the vegetal biomass, evaluated both qualitatively (relative representation of the various vegetation levels) and quantitatively (concentration of pollen per gram of dry sediment) during the course of the Holocene enables reconstruction of the complete climatic and hydrologic history of the region up to the dawn of the Present.

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Dates et versions

hal-00908397 , version 1 (22-11-2013)

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Citer

Anne-Marie Lézine, J.-J. Chateauneuf. Peat in the Niayes of Senegal: depositional environment and Holocene evolution. Journal of African Earth Sciences, 1991, 12, pp.171-179. ⟨10.1016/0899-5362(91)90067-9⟩. ⟨hal-00908397⟩
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