La marge septentrionale de la Tethys maghrebine au Jurassique (Djurdjura et Chellata, Grande Kabylie, Algerie)

Within the Alpine belt extending from the Strait of Gibraltar to Calabria, the sedimentary cover of the Kabylia Chain ("Dorsale Kabyle" or "Chaine calcaire" of French authors) is a key element of the Maghrebides, that marks out the boundary between the internal and external orogenic zones. Studies of the lithostratigraphy and depositional environments of the Jurassic succession of this domain, coupled with datings by ammonites, show that rifting during the Liassic led to a transverse differentiation through the calcareous chain. Rifting occurred in a progressive manner from the south towards the north, affecting successively the external domain of the chain at the Hettangian to early Sinemurian boundary, the median domain during the late Sinemurian and the inner domain from the Domerian up to the Toarcian. This diachronous tectonic activity was accompanied by the formation of structures in an extensional regime (normal faults, fault-scarp breccias, Neptunian dykes, synsedimentary discordances, etc.). Terrains affected by this extension were immediately subject to subsidence, which also migrated from the south 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 -- located in the "Great Kabylia" -- may be applicable to other parts of the Maghrebide orogenic belt. In many respects, the geodynamics of this northward facing margin of the Kabylian basement is similar to that of the European continental margin of the western Alps bordering the Tethyan realm.