Polyphase deformation of the Dorsale Calcaire Complex and the Maghrebian Flysch Basin Units in the Jebha area (Central Rif, Morocco): New insights into the Miocene tectonic evolution of the Central Rif belt

In order to better understand the orogenic evolution of the Rif chain in the Eocene-Miocene interval, we provide new structural and kinematic data for the Jebha area, a key-sector of the Central Rif. Here the thrust sheet superposition occurs along the well-known Jebha-Chrafate lineament, widely considered as a major left-lateral transfer fault that enabled the Miocene westward migration of the internal thrust front. Our structural analysis was mainly focused on (i) the internal deformation of stacked nappes and (ii) the kinematics of the main thrust faults. Five main deformation stages were recognized for the Eocene-Miocene tectonic evolution of this area. The first orogenic pulse (D1), which occurred in the Eocene-Oligocene interval, was responsible for the tectonic stacking of the Ghomaride Nappes. Subsequently between the late Aquitanian and the late Burdigalian, imbrication (stage D2) occurred for some Internal Dorsale Calcaire thrust sheets within a dominant regional ENE-WSW shortening. At the Rif scale, different displacements of the WSW-migrating thrust front were accommodated by transfer structures including the Jebha-Chrafate fault. The following late Burdigalian-Langhian stage (D3) was defined, on the contrary, by a prevalence of the radial thrust front migration. In the Jebha area the early thrusting (stage D3a) was characterized by a main SE-vergence. In this phase the External Dorsale Calcaire and the Maghrebian Flysch Basin Units were included in the accretionary wedge. Two late D3 regional deformation phases were probably related to the buttressing effect that followed the collision of the thrust sheet pile against the crustal ramp of the External Rif domain. The first stage (D3b) consisted of an out-of-sequence thrusting recorded in the western sector of the Jebha area with the superposition of the Ghomaride Unit onto the External Dorsale Calcaire Unit, and in the eastern sector with the stacking of the Internal Dorsale Calcaire Unit directly onto the Predorsalian Unit. The second stage (D3c) included a late back-thrusting affecting the whole orogenic chain and deforming all the tectonic contacts. The fourth stage (D4) was characterized by strike-slip faulting and SW-verging folding. This latter mostly affected the successions located to the East of the Jebha village and was partially synchronous with the D3 stage. It was most probably related to the SW-migration of the internal thrust-front of the Bokkoya Dorsale Calcaire Complex and a renewed activity of the Jebha-Chrafate fault zone. The last tectonic stage (D5) included a radial extension expressed by high and low-angle normal faults.