Upper Jurassic – lowermost Cretaceous formations in northern Tunisia include the Zaress Fm. of the Tunisian “Dorsale” (Ammonitico Rosso facies: Middle Callovian-Oxfordian) and the corresponding beds from Fahs and Jédidi fms (radiolarian-bearing series: Upper Bajocian-Oxfordian) of the nearby surrounding exposures and the “Tunisian Trough”, respectively. These heteropic facies are overlain by the marl/limestone alternations of the Beni Kleb Fm. (Kimmeridgian – Middle Berriasian). Recent integrated biostratigraphic investigations (ammonites, radiolarians, calpionellids) undertaken in different palaeogeographical domains of northern Tunisia allowed a precise dating of the Malm -Berriasian fms. Revised lithostratigraphy and regional correlations lead to the recognition of an updated facies repartition in central and northern Tunisia. Within the North Maghrebian Range, main palaeogeographical segments can be outlined considering facies affinities: the North-South Axis successions of Central Tunisia show close affinities with those described from the Middle and Central AurŻs Range (eastern Algeria). The Tunisian “Dorsale” series are to be compared with corresponding beds of northern AurŻs, Hodna Mounts and the South Tellian Border (Tiaret area), in Algeria, and with the Prérif and Mésorif Upper Jurassic facies, in Morocco. Deeper facies of the Tunisian Dorsale surrounding outcrops and the “Tunisian Trough” are closer to successions described in ancient literature from the Babors and the West Numidian Range of Algeria. All these equivalent successions from the external segments of the Maghrebian Range are quite distinctive from the Internal Rif and Kabylias “Dorsales calcaires” series. Both facies types have evolved in clearly different palaeogeographical realms related with the tectonic evolution of north- and south-western Tethys margins since the Triassic – Early Jurassic times.
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