Carte Geologique du Maroc au 1/50 000, feuille Taghazout - Notice explicative

The 1/50,000 Taghazout sheet includes formations belonging to two distinct structural domains: the Anti-Atlas precambrian basement to the South, and its paleozoic cover, which outcrops in the northern and eastern parts of the sheet. The middle proterozoic basement (Cryogenian, NP2-PII) outcrops in the nearby sheets of Boumalne and Imtir: metamorphosed and folded during the panafrican orogeny, it is unconformably covered by thick volcanic and volcano-clastic formations (Ouarzazate Group), and truncated by intrusive bodies, which, neither metamorphosed nor folded, are referable to the upper Neoproterozoic or Ediacaran (NP3-PIII). In the Taghazout sheet outcrop only the Ouarzazate Group and the upper neoproterozoic magmatic bodies of Oussilkane, Arharrhitz, Bou Gafer and Tanout Addou. They correspond to a post-collisional sequence from calc-alkaline with high K to shoshonitic. The basement of the Taghazout sheet is characterized by faulting tectonics with normal and transcurrent faults of uppermost neoproterozoic age, associated with an intense fluids activity. These structures has been strongly reactivated during the Paleozoic (hercynian orogeny) and afterward. The Paleozoic consists of sedimentary sequences ranging in Age from Lower Cambrian to Carboniferous (Visean). Its basis unconformably rests on a rough paleomorphology developed on the precambrian basement of the Jbel Saghro. The series, several thousands meters thick, is characterized by clastics with some carbonate local deposits. The Cambrian is represented by the Tata group and the Feijas internes group. The first constitutes the lower part of a cycle, including a continental lower unit (Formation d’Igoudine), that fills the upper precambrian paleotopography, and a cover of marine tidal limy siltstones (Formation d’Amouslek). These two formations onlap the precambrian basement of the northern Saghro. The upper part of the cycle corresponds to the sandstones of the Formation d’Asrir that disappears northwards. The second cycle, more generalized, includes the classical platform sequence of the Middle Cambrian: the Niveau de la Brèche à Micmacca, the Formation du Jbel Wawrmast (or Schistes à Paradoxides) and the Formation du Jbel Afraou (or Grès du Tabanit). Following the upper cambrian-tremadocian general hiatus, the Ordovician corresponds to series deposited in a marine platform affected by frequent eustatic changes and subsidence stacking patterns. It finishes by the major event of the upper Ashgillian sea level fall related to the north-west African glaciation. On the other hand, the Silurian and devonian outcrops are very localized to the North and North West and present incomplete sequences because of a complex tectonic context. They are represented by the lower Silurian black shales and by some middle/upper Devonian fossiliferous limestones. The Carboniferous series is extensively developed in the northern part of the map, forming the group of the Flysch du Jbel Tisdafine (Visean). This group consists of a lower unit, with olistostrome characters, (Formation d’Ait Yalla) that fills a fault controlled paleo-topography, and of a thick flyschoid upper unit (Formation de Tinerhir) probably of deltaic character. The entire paleozoic sequence is affected by deformations related mainly to the hercynian orogeny, with intensity decreasing southwards and south-eastwards. The more deformed zones are characterized by southward thrusts involving Silurian and carboniferous formations. These are part of the deformed Tinerhir block that extends westwards, in the Imtir area. In the rest of the sheet, the deformations correspond to fold systems, with NE-SW to N-S and E-W directions, and to faulted zones affecting the cambrian-ordovician sequences. These faults strike essentially NE-SW and ENE-WSW and are characterized by steeply dipping planes and a polyphase kinematics. They form the north Saghro system, being the Isk n'Izekelli and Tizi n'Boujou-Bou Tiouit faults the major regional structures. The only rocks referable to the Meso-Cenozoic are represented by some liassic dolerites, intruded into the cambro-Ordovician sequence, and by some flows of olivine nephelinite of mio-pliocene age.