Palynology and sedimentology of the Miocene series in the north-east of Tunisia: the climatic and eustatic signature

The Saouaf syncline is located in Tunisia Centre north-east, south-east of the Tunisian dorsal. The sedimentary series, starting with limestone and marlstone, is essentially an alternation of three terms, sandstone, clay and lignite. It is in this basin that the Saouaf Formation was defined as a siliciclastic and lignite series dating back to the Serravallian-Tortonian age. The pollen associations identified in this series allowed for the organization of the vegetation in the era in altitudinal levels (coastal environment, rivers edges, plains, high zones). The evolution of vertical micro-floristic associations through the detailed analysis of the palynological diagram reflects the fluctuation of climatic and ecological parameters during this period. Moreover, the facies associations reflect an evolutionary curve in the depositional environment, showing its fluctuation over time. Accordingly, the synthesis of palynological data, correlated with lithosedimentological ones, suggests the type of environment prevailing at that time. This is a coast-lagoon fluvio-deltaic environment with a significant detrital influence in a subsiding context controlled by a fluctuating but generally warm climate.     

Study of a Neogene basin dynamics: The “Bizerte basin”, northeastern Tunisia: relevance to the global Messinian Salinity Crisis

The Messinian sediments of northeastern Tunisia were deposited under an active tectonic setting. They are organized in sequences indicating a transitional deposit from margin – littoral to lacustrine – continental facies. These series unconformably overlie the Serravallian–Tortonian silty clays packages, and are overlain by the transgressive Early Pliocene marl (Zanclean). The presence of evaporitic strata points out to the Messinian Salinity Crisis described in the peripheral basins of the western Mediterranean. The Messinian sedimentation was found to have been closely controlled by transtensive tectonics and differential subsidence at a large spatio-temporal scale. It is organized in sequences typical of a depositional environment controlled by eustatism, tectonic and maybe by climate changes. Despite the existence of some local specific sedimentological characteristics, our results corroborate previous findings that pointed out to the Messinian times as a singular period all around the Mediterranean Basin. Field and subsurface seismic profile data helped reconstructing either the sedimentary or tectonic unconformities existing between the studied Messinian series and older Neogene successions.