A cargo de Sébastien DETRICHE Université Paris-Sud, ORSAY (France)
SEMINARIS DE LA FACULTAT DE GEOLOGIA I L'INSTITUT DE CIÈNCIES DE LA TERRA JAUME ALMERA

Universitat de Barcelona (UB)
Consell Superior d'Investigacions Científiques (CSIC)

Dia: Dimecres 11 de Març
Hora: 12.00 h
Lloc: sala d'actes de l'Institut Jaume Almera

Resum:
Lake Afourgagh is a small (~0.03 km2), shallow groundwater fed lake (~ 6 m deep in 2005) located in the Middle-Atlas mountain in Morocco (alt. 1380 m). Since the last 1970's, the lake experienced a strong fall of its water level as a result of recurrent droughts and human activities. The recent evolution of the lake system allows asking the following questions: has the lake experienced such perturbations during the historical period? If yes, were they linked to climate and/or to human activities? In order to answer these questions, a combination of lithofacies and biofacies (charophyte, ostracod, diatom and mollusc remains) characterization and deposit geometry data was studied on the lake shore-terrace sediments. It provides evidence for four major low lake level phases (estimated in terms of pluridecimetric to plurimetric amplitudes) during the last 2500 years which induced the development of palaeosols in proximal settings at 2191 cal. BP, 1769 BP, 1515 cal. BP and 1062 cal. BP. These events appear to be linked to major arid episodes on a regional scale.

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