The northern margin of the Maghrebide Tethyan domain during the Jurassic (Djurdjura and Chellata massifs, Great Kabylia, Algeria)

Within the Alpine belt extending from the Strait of Gibraltar to Calabria, the sedimentary cover of the Kabylia Chain ("Dorsale Kabyle" or "Chaine cal caire" of French authors) is a key element of the Maghrebides, that marks o ut the boundary between the internal and external orogenic zones. Studies o f the lithostratigraphy and depositional environments of the Jurassic succe ssion of this domain, coupled with datings by ammonites, show that rifting during the Liassic led to a transverse differentiation through the calcareo us chain. Rifting occurred in a progressive manner from the south towards t he north, affecting successively the external domain of the chain at the He ttangian to early Sinemurian boundary, the median domain during the late Si nemurian and the inner domain from the Domerian up to the Toarcian. This di achronous tectonic activity was accompanied by the formation of structures in an extensional regime (normal faults, fault-scarp breccias, Neptunian dy kes, synsedimentary discordances, etc.). Terrains affected by this extensio n were immediately subject to subsidence, which also migrated from the sout h towards the north. The distribution of sedimentary facies in the studied area during the Jurassic is interpreted in terms of a passive margin which opened out towards a future trough of flysch sedimentation in the south and which graded northward into a possibly emerged continental domain. Such an analysis concerning one of the main segments of the Maghrebide chain - loc ated in the "Great Kabylia" - may be applicable to other parts of the Maghr ebide orogenic belt. In many respects, the geodynamics of this northward fa cing margin of the Kabylian basement is similar to that of the European con tinental margin of the western Alps bordering the Tethyan realm.