## 2 Study Area  
The study concerns two geomorphological units that are part of the western Anti-Atlas, namely the limestone plateau of Lakhssas to the east and the Ifni inlier to the west. According to the new administrative division of Morocco in 2015 [13], they belong respectively to the regions of Souss Massa and Guelmim Oued Noun (Figure 1), with an area of about 2618.19 km\({}^{2}\). Geographically, the study area is bounded to the west by the Atlantic Ocean, to the south by the semi-desert plain of Guelmim, to the north by the limestone plateau of Tiznit, and to the east by the Paleozoic inlier of Kerdous. The study area has three morphological domains (Figure 1):  
* The Lakhssas plateau forms a rugged mountain barrier with an altitude of 1200 m between the Guelmim depression in the south (400 to 600 m) and the Tiznit plain in the north (100 to 400 m). The Lakhssas plateau is a complex anticline fold rising towards the west, overlooking the Ifni inlier with a slope of altitude of 300 to 500 m in the depressions [14]. The sedimentary cover of the border of the Ifni inlier, whose altitude varies between 400 and 700 m, is dominated by surface and underground karst phenomena. * The Ifni inlier's altitudes reach 200 m in the central zone and approach 1100 m in areas with volcanic rocks, especially rhyloitic. It is dug in a depression compared to the Lakhssas plateau. The central zone with flattened relief is dominated by Paleoproterozoic graintes covered in turn by Paleozoic and post-Paleozoic rocks, which form visible ridges [15]. * The coastal platform lies along the west coast of the Ifni inlier with an altitude between 30 and 100 m. The sharp cliff dominates the coastal fringe of 50 m and below the cliff, along the coast, we recognize dead cliffs of the Middle Quaternary and Flandrian [15]. On the structural and geological level, the study area belongs to the Anti-Atlas (Figure 2) [16] which is subdivided into three major structural areas [17]:  
* The Central Anti-Atlas on both sides and along the major Anti-Atlas accident [18],
* The Eastern Anti-Atlas northeast of this accident,
* The Western Anti-Atlas to the southwest of this accident represents the frontal edge of the West African craton [19]. In Morocco, the Antecambrian inliers, where granitoids of the Proterozoic cover the Neoproterozoic terminal and Paleozoic, constitute the Anti-Atlas, especially the western Anti-Atlas, of which the Ifni inlier and the plateau of Lakhssas form a part. The Ifni inlier has a geological history that begins from the Paleoproterozoic to Cenozoic through the Neoproterozoic, Paleozoic, and Mesozoic [20; 21; 22]. It is formed by various granitoids surrounded by volcanic and volcano-sedimentary formations, which grow in the north, east, and south under the carbonate cover. The basement is formed exclusively by eburnean granites [20]. It outcrops to the east of the inlier, in the plain of Tioughza, in the Douar of Alouzad, showing a coarse texture, and to the north, in contact with the Neoproterozoic massif of the Sahel where it is finer. The Neoproterozoic cover is represented by quartzitic sandstones of the Lkst Group belonging to the Anti-Atlas Supergroup [21], and lower and upper volcano-sedimentary formations of the Ouarzazate Supergroup [22]. These formations are intersected by two groups of pan-African granitoids: Cryogenians represented in chronological order by the massif of Mesti then that of Ifni and those Edi-acarian represented by the massifs of Taoulecht, Tioughza, and Mirleft. The limestones of the Lower Cambrian surmount this series. Figure 1: Geographical localisation of: (**A**) Morocco; (**B–D**) Ifni inlier and Lakhssas plateau. On the other hand, the geological history of the Lakhsssa plateau is limited to the Paleozoic and it is composed primarily of calcaro-dolomitic carbonate rocks of the Adoudounian period, from which an underground and surface karstic network develops. The Lakhsssa plateau is located between the inliers of Ifni and Kerdous.