| Abstract: | Analysis of sediments and morpho-structural elements of the last 25 km of the lower Moulouya valley has shown that this river evolved during the middle and upper Holocene in a tectonic context of uplift, at the South-Eastern end of the Kebdana Mountains. This geodynamic context limited the sedimentation and inhibited the formation of a delta on the Mediterranean shore. A brief sedimentary episode allowed about 10 m of sediments to be deposited, forming a well-marked alluvial terrace. The sedimentation appeared before 3,750 years cal BC in connection with the Holocene sea transgression (“Mellahian” period) and a probably more humid period. It developed at an average rate of 0.6 mm.a–1, five kilometres from the shoreline, before stopping just after 395 years cal BC, at the same time as the post- Mellahian regression. The sediments show evidence of syn- and post-sedimentary seismic activity (seismites, diaclases, faults). They also show some traces of the “Mellahian” transgression (beds containing halite and gypsum) which indicate an average rise of 2.0 mm.a–1 since about 3,700 years cal BC, 22 km from the Moulouya mouth. The sediment composition indicates a subarid climate during the Holocene, but does not enable possible climatic variations to be detected. |
