Barremian intracontinental rift and Aptian Atlantic transgression in the northern boundary of the Central High Atlas (Morocco)
Résumé
The northern boundary of the Central High Atlas was affected by a transgression during the Aptian that reached the junction zone between the Middle and the High Atlas. In this sector (Naour-Aghbala) which corresponds to the presumed closure zone of this Aptian Atlantic marine trough, the sedimentary record reveals a strong dependence on the regional structural framework. The Barremian continental sedimentation is concentrated in an elongated W-E highly subsiding zone, limited to the south by the polyphase Aghbala-Afourer Fault Zone (AAFZ), which corresponds to the contact between the main Atlasic Belt and its northern boundary (Beni Mellal Atlas). The Aptian deposits preserve similar littoral marine characters from West to East without showing any confined facies, which could evoke the eastern limit of the gulf. On the other hand, towards the North, the Aptian layers rapidly change from marine to lagoonal then to continental facies. The paleogeographic boundary of the Aptian shoreline, oriented E-W, is locally controlled by the North El Ksiba Fault (NKF) in the North. The Aptian Atlantic transgression, closely linked to the narrow Barremian graben, shows a wide northward extension of the marine sedimentary area. The Barremian graben highlighted in the Aghbala-Naour area represents only a segment of a major east-west intracontinental rift that continued eastward with the more recent frontal thrust of the eastern Moroccan High Atlas. This faulted structure was the penetration axis of a double transgression: from the Tethys to the East and from the Atlantic Ocean to the West on the emerged Atlasic domain.