The Dayet Iffer belongs to the Dayets of tectono-karst origin of the Northern Middle Atlas. After its watershed genesis of middle altitude during the Quaternary, two lacustrine formations were deposited on the surface while other thick formations exist in depth. The detailed sedimentological study of the soltanian and holocene lithological sections on the surface and the 14C datings helped recognize part of the history of the watershed. The geophysical study allowed to detect the thickness of the superficial geological formations as well as the various geological phenomena (tectonic and/or karst) that affected them from the genesis to the present. The current shape of the watershed where the Dayet Iffer exists is only the result of an evolution where sedimentary, tectonic and karst phenomena interfere. The tomography obtained with Res2DInv software, performed for the first time at the Dayet Iffer, reveals the presence of three ranges which can be interpreted as three resistive, intermediate and conductive zones with a large set of faults. These results helped determine the thickness (over 160 m) of the sedimentary filling. This shows that the hydrological behavior of the Dayet Iffer takes into account both horizontal flows at the stratification and/or karstic joints and the movement of sub-vertical fractures.

In northern Middle Atlas, the Dayet Iffère is located in an area affected by karst and tectonic. After its watershed genesis of middle altitude during the upper Pleistocene, two lacustrine formation were deposed. The detailed sedmentological study as well as the correlations between the different lacustrine formations defined in Dayet Afourgagh and Dayet Agoulmam, and the 14C dating allowed to reconstitute the major stages of the filling evolution of the lake basin and its sedimentary dynamic. The variations of sedimentation are interpreted as climatic fluctuations and evolution of vegetation since upper Soltanien. These results show a complex interaction between sedimentary processes and climatic phenomena that tend to a stability marked by heat, permanent humidity and a fairly dense vegetation cover at the end of the Soltanian, after probably a hot arid to semi-arid episode.

No abstract

No abstract