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Hydrodynamics in Holocene Lake Mega-Chad |
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| Authors: | Frédéric Bouchette Mathieu Schuster Claude Roquin Patrick Marsaleix |
| Institution: | a GEOSCIENCES-M, Université Montpellier II et CNRS, cc 60, Place Eugène Bataillon, 34095 Montpellier cedex 5, France b Université de Poitiers UFR SFA, IPHEP - Institut International de Paléoprimatologie, Paléontologie Humaine: Evolution et Paléoenvironnements, CNRS UMR 6046, 40 avenue du Recteur Pineau, 86022 Poitiers, France c Institut de Physique du Globe de Strasbourg (CNRS/Université de Strasbourg, UMR 7516, EOST), 1, rue Blessig, 67084 Strasbourg, France d HR-Wallingford, Howbery Park, Wallingford, OX10 8BA, UK e Laboratoire d'Aérologie-CNRS et Université de Toulouse, 14, Avenue Edouard Belin, 31400 Toulouse, France f Institut de Mathématiques et modélisation de Montpellier, Université Montpellier II et CNRS, cc 51, Place Eugène Bataillon, 34095 Montpellier cedex 5, France |
| Abstract: | Holocene Lake Mega-Chad (LMC) was the largest late Quaternary water-body in Africa. The development of this giant paleo-lake is related to a northward shift of the isohyetes interpreted as evidence for an enhanced Monsoon (African Humid Period). Numerous preserved coastal features have been described all around the LMC shore. Such features reveal the main paleo-hydrodynamical tendencies. In the context of a closed water-body like LMC, hydrodynamics are forced mainly by winds. We use a three-dimensional numerical model (SYMPHONIE) to simulate the mean hydrodynamics in LMC under both Harmattan-like (northeasterly trade winds) and Monsoon-like (southwesterly winds) forcings. The northern part of LMC displays coastal features, such as sand spits, that are consistent with the simulations forced by Harmattan-like winds. Geomorphic features related to Monsoon-driven hydrodynamics are not clearly expressed. They could have developed during the early stage of LMC but subsequently reworked. At the time of sand-spit building, Harmattan-like driven hydrodynamics prevailed and related coastal features were preferentially preserved in the sedimentary record. |
| Keywords: | Wind-driven circulation Sand spits Wave-cut terrace Monsoon Trade winds SYMPHONIE Coastal modelling Paleo-lake Africa Sahara Alongshore drift |
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