The lower Maastrichtian deposits of the Mateur-Beja area in northern Tunisia are mainly composed of fine-grained marl and limestone alternations occasionally interbedded by coarsegrained calcarenites and gravel deposits. In the coarse-grained intervals sedimentary structures are indicative of storm-induced high-energy currents in an outer ramp to slope setting and of local reworking by bottom currents in the basin. In deeper environments, finegrained sediments accumulated mainly while settling from storm-induced suspensions. The lower Maastrichtian deposits contain abundant Zoophycos exhibiting two main morphotypes, skirt-shaped Zoophycos in deposits around storm-wave base and tongue-shaped Zoophycos in somewhat deeper sediments. The types differ in burrow architecture, morphology of lobes, and size of structural elements. These differences are attributed to different behavioral programs modulated by the availability of benthic food that decreased seaward. Stormaffected environments seem to be a prerequisite for these Zoophycos-producers to choose their habitat.
The northwestern Tunisian Mateur-Beja domain comprises a thick succession of carbonate units belonging to the Late Cretaceous (Abiod Formation) and the Early Eocene times (Bou Dabbous Formation and its lateral equivalent). Sedimentological analyses were carried out on these sedimentary units with regard to their paleogeographic reconstructions. Three sections from the Upper Cretaceous and ten sections from the Lower Eocene successions were selected and correlated through the study area. The Upper Cretaceous Abiod Formation is composed of foraminiferal biomicrite limestones and marls deposited in outer platform to basin environments located slightly below storm wave base. The Lower Eocene carbonate successions are characterized by various storm-induced coarse-and fine-grained facies deposited in inner platform to basinal environments. Both carbonate units are characterized by significant lateral variations in thickness and facies. Close inspections show that thickness and facies variations were especially caused by synsedimentary major fault activity and locally by halokinetic movements. Comparison between the two studied units suggests that the changes of tectonic regime would have had significant impacts on thickness and facies distribution. Thus, the Upper Cretaceous and Lower Eocene carbonate deposits are interpreted in tectonically controlled basins.
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