Chellata strike-slip fault a transkabyle polyphase fault, contemporary with the Miocene collision (Kabylian “Dorsal”, Algeria): A new kinematic and geodynamic interpretation

Abstract

The Rif, Kabyle, and Sicilian-Calabrian fronts are primarily manifested by thrust structures on the forelands of African origin. These thrust fronts of the internal zones over the external zones of the Maghreb exhibit variable geometries depending on the transects: the average dip differs from one block to another, as seen between the Djurdjura and Chellata massifs, located on either side of the eponymous pass. The differential tangential block displacement between these two entities creates a decoupling through a strike-slip system, making them relatively autonomous. The Chellata massif retains a coherent paleogeographic organization, while the western Djurdjura shows moderate deformation and thick formations. To the east, deformation gradually decreases, waning near the Chellata massif and concentrating at the Chellata Pass fault. This structure, interpreted in this paper as a sinistral strike-slip, challenges earlier interpretations by Gélard in his thesis, which suggested a dextral motion. The structural analysis reveals two main phases of sliding between the Djurdjura and Chellata blocks. The first phase, sinistral, displaces the Djurdjura by 15–20 km to the south. The second phase, dextral, brings the Chellata block back to its current position. This dynamic is facilitated by a network of conjugate strike-slip faults, notably the Chellata fault to the east and the Thénia-Bouira fault to the west. This phase of late strike-slip and thrusting, dated between the Serravallien-Tortonien is part of the Maghreb collision, synchronized with oceanic opening in the western Mediterranean and the activity of the south Mediterranean transform network.