First occurence of rudists (Bivalvia) from the Coniacian-Santonian limestones of the Saharan platform, southern Tunisia: Description, biostratigraphy and correlation

This study focuses on the description of rudists observed within the Berressef Formation from the Matmata area in the Saharan platform of southern Tunisia. The study of rudists is based on two measured stratigraphic sections and five observation points. It has revealed for the first time the presence of Coniacian-Santonian rudists. Two rudist associations were identified: 1) Biradiolites angulosus-Biradiolites martellii-Radiolites trigeri association (Coniacian) containing Durania cf. arnaudi, Bournonia cf. gardonica, Biradiolites sp., Hippurites sp. and Apricardia sp.; and 2) Radiolites dario-Bournonia fascicularis association (late Coniacian-Santonian) including Sauvagesia sp. and Radiolites sp. These associations have showed a remarkable similarity with those of central-south of Apennines, Italy. Rudists of the Berressef Formation are mostly elevators in growth position. They present cylindrical to elongated cylindrical shapes and they are organized in isolated individuals, bouquets and clusters. The rudist facies A is mostly represented by rudists in growth position. The facies B consisted of bioclastic limestones rich in rudists fragments, which is considered to have been deposited not far from their original palaeoenvironment.