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In South Tunisia, the Bir Mastoura (BMT-1) borehole provides Carboniferous, Permian, and early Triassic foraminifers and carbonate algae which permit to establish a local biozonation which can be correlated with (1) the Capitanian (Late Middle Permian) outcrops of Jbel Tebaga; (2) other Tunisian boreholes; and (3) several stratotypes and/or well-studied Tethyan outcrops. Microfacies, microfaunas and microfloras of BTM-1 reveal subtropical, carbonate, inner platform deposits. As everywhere in the world, the Early Triassic is faunistically very poor. The Upper Permian and Upper Middle Permian microfaunas and microfloras are traditional in Tunisia, but a little poorer than the Tebaga assemblages. The fusulinids of the middle and lower Middle Permian strata are also less numerous than in other Tunisian boreholes. The late Pennsylvanian fusulinids known in some of these boreholes, were not observed in BMT-1; however, these fusulinids are re-discussed here due to their biostratigraphic and palaeobiogeographic importance; they are assigned to two substages, early Gzhelian with Darvasoschwagerina spp. and late Kasimovian with Schwageriniformis petchoricus. Neither early-middle Kasimovian nor late Moscovian microfossils were found, and their absence is probably regional in the whole North Africa. In contrast, the early Moscovian beds yield all the fusulinid biozones of the Urals (Russia) and display diversified microfauna with Profusulinella aff. simplex, Ovatella ex gr. ovata; Depratina timanica, Aljutovella (Tikhonovichella) rhombiformis, Hemifusulina spp., Eofusulina aff. tashlensis, Paraeofusulina trianguliformis, Moellerites cf. praecolaniae and Parabeedeina cf. pseudoelegans. The middle-late Bashkirian seems to be only partially represented, whereas the early Bashkirian is similarly relatively complete, with Varvariella ex gr. varvariensis, Plectostaffella cf. karsaklensis, P.? nauvalia, Semistaffella? sp. and common oolitic microfacies. The Serpukhovian and late Visean appear more developed than in other boreholes. They yield Praedonezella, Eosigmoilina and Endostaffella. As across the North Africa, no older Mississippian foraminifers are not known prior to the late Visean. The palaeogeography is discussed thanks to the regional new data; especially the concept of a Saharan province, or its replacement by multiple aborted rifts during the late Visean-Serpukhovian. From the Bashkirian to Early Permian, affinities with Croatia are frequent. Comparisons with other North African basins, northern Spain, Donets Basin, the Urals basins, Moscow Basin, Taurus and Alborz are also presented. |
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