The Geology of the Pelagian Block: The Eastern Tunisian Platform

Abstract

The eastern platform of Tunisia, the Tunisian section of the Pelagian block, is one of four major tectonic units which can be seen in a northwest-southeast traverse across the country (Fig. 1). In the northwest lies the Alpine zone with the Numidian nappes, Tell units, and the autochthon and para-autochthon of Hedil and Medjerda. This zone is bordered immediately to the south by a zone of diapirs, but is separated from it by a major fault. The two together formed a sediment-filled foredeep in Miocene time. The importance of this fault was noted by Jauzein (1967) who called it the Teboursouk suture (the Teboursouk thrust of Rouvier, 1973). Jauzein considered it to be the eastern limit of the zone affected by Upper Pliocene-post-Villafranchian tangential thrust faulting. Detailed study of a section of the fault (Bajanik and Salaj, 1971) showed it to be a zone varying in width from a few dozen meters to a kilometer, and trending northeast-southwest. The zone of diapirs marks the northern edge of the intermediate chains of the Tunisian Atlas. These chains terminate to the south against the Saharan platform, and to the east against the Tunisian platform, the edge of which is found by a tectonic feature known as the north-south axis (Fig. 1). At Sbiba there is a westward jutting salient in the north-south axis; north and west of this point the autochthonous Atlas tends to have structures striking northeast-southwest, while to the south the influence of the Saharan platforms seems to have imparted an east-west structural tend.