Ben Moussa T., Amrouni O., Hzami A., Dezileau L., Mahé Gil, Abdeljaouad S. (2019). Progradation and retrogradation of the Medjerda delta during the 20th century (Tunisia, western Mediterranean). Comptes Rendus Geoscience, 351 (4), p. 340-350. ISSN 1631-0713.
Titre du document
Progradation and retrogradation of the Medjerda delta during the 20th century (Tunisia, western Mediterranean)
Ben Moussa T., Amrouni O., Hzami A., Dezileau L., Mahé Gil, Abdeljaouad S.
Source
Comptes Rendus Geoscience, 2019,
351 (4), p. 340-350 ISSN 1631-0713
The aim of this study is the reconstitution of the recent morpho-sedimentary evolution of the Medjerda River delta. We examine the spatio-temporal evolution of the Medjerda shoreline between 1936 and 2016 using satellite images, complemented by sedimentological and geochemical analyses and (210)Pbex and (137) Cs radiometric data. The general tendency of the shoreline evolution shows an increasing progradation (300 +/- 12 m) between 1936 and 2016. Yet the mesoscale Net Shoreline Movement position (NSM) and the End Point Rate (EPR) reveal an erosion pattern estimated to be -20 m +/- 0.15 m/yr during the period 1988-1999. The sedimentological analyses reveal four main lithostratigraphic units. The fine sand substratum layer (Md = 0.08 mm) decreases toward clay and silt facies (Md < 0.063 mm), rich in continental plant debris. The geochemical results reveal gradual incoming of the terrigenous component instead of marine deposits. The Cs-137/(210) Pbex radiometric dating confirms the functioning of the new river flow by the 1950s with the highest sedimentation rate being 3.3 cm/yr. Our results show that the Sidi-Salem dam impoundment (1981) led to a dramatic reduction of sediment discharge, a decrease of the grain size with nearly no more sand reaching the coast, and the shoreline retreat.
