The sedimentological changes caused by human impact at the artificial channel of Medjerda-River (Coastal zone of Medjerda, Tunisia)
2018
Abstract. Recent sedimentary and morphological changes at the new mouth of
Medjerda-River (Gulf of Tunis) are investigated using a multiproxy approach
of sediment cores complited by 210 Pbex and 137 Cs method dating. The
subject of the study is to focus on surveying the sedimentary evolution of
Medjerda-Raoued Delta caused by the human intervention in the management of
the main tributaries of the Medjerda-River (artificial channel of Henchir
Tobias). Sediment cores (CEM-1 and CEM-3) were subjected to both multiproxy
approaches (Grain size, geochemical analysis and dating radiometric
210 Pbex and 137 Cs). The sedimentological analysis of the new
deltaic deposits shows a progradation sequence with the silt and clay
deposits on the historic sandy substratum. The mean grain size evolution on
the old beach profile shows a decreasing trend from backshore (CEM-3) to
nearshore (CEM-1). The geochemical results show varying concentrations of
chemical elements such as Fe, K, Rb, Nb, Cr, Ti, Ba, Ca, Sr, Zr, V, and
potentially toxic metal trace elements such as Pb, Zn and the As. The
Principal component Analysis (PCA) applied in the geochemical elements
evolution confirms the marine origin of the sand deposits in the basic layers
of the two cores. The chronological method ( 210 Pbex and 137 Cs)
affirms that the first fluvial deposits were set up only after 1950. The
sedimentological and geochemical result confirm the actual unless of coarser
fluvial supplies under the human activities leading the negative coastal
sediment balance and the shoreline retreat as well.
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