The development of mixed sequences in a marginal setting: example of the Late Albian–Cenomanian in Central Tunisia

The sequence stratigraphy of mixed succession with evaporitic intercalations has already reported in several works around the world. The present work aims to study the sequence stratigraphy of the mixed succession of the Zebbag Formation (Albian–Cenomanian) in Central Tunisia. This study is based on the measuring of a ۱۴۰ m-thick section of the Zebbag Formation with a tight sampling of the carbonate rocks, completed by the microscopic observation of thin sections and the analysis of the chemical composition of the carbonate rocks. According to the vertical changes of the depositional facies notably the carbonate facies on one hand, and the vertical variation of the chemical composition of the carbonate levels on another hand, the Zebbag Formation can be subdivided into ۲۲ mixed depositional sequences that developed in a marginal setting at the southern Tethyan border. The depositional sequences were controlled by the fluctuation of sea level and recorded the alternating marine regression and transgression and the resulting continental and marine influences, respectively. All the depositional sequences show at the base an evaporite succession representing the lowstand system tract, whereas the transgressive and the highstand system tracts are occurred by different deposits according to the depositional environment. Indeed, in the inner part of the platform these system tracts are represented by bedded limestones, whereas in the outer parts are indicated by marls. In the middle part of the platform, the transgressive and highstand system tract are recorded by interbedded marls and limestones.

The development of mixed sequences in a marginal setting: example of the Late Albian–Cenomanian in Central Tunisia Keywords:

Depositional facies , mixed sequences , Late Albian , Cenomanian , Zebbag Formation , Khanguet Zebbag , Central Tunisia