publications

Article

The role of rudists in micrite production and stabilisation - Example of the Upper Cretaceous rudist formations of Jebel El Kebar, Central Tunisia

Gili Eulàlia , NEGRA Mohamed Hédi, 2004

Courier Forschungsinstitut Senckenberg, 247, 247, 193-205, Avril 2004

Résumé

Campanian rudist limestones outcrop in Jebel el Kebar (Central Tunisia; fig. 1) and constitute planar-convex lensoid bodies laterally changing to intraformational conglomerates. The sedimentary characters of these rudist limestones, such as their structures, textures and composition, rapidly change vertically and laterally. Micritic limestones containing floating entire rudists are frequent and generally form mound-like bodies which may be overlain by rudist-rich packstones. From the micritic to the rudist-rich limestones, rudists show different roles. Within mound-like bodies, most micrites are biodetrital and are derived from the disintegration of rudists. In addition, recumbent rudists, such as Sabinia, which were recently identified, preferentially occupied mound-like bodies ; they, at least, contribute to the entrapment and stabilisation of micrites. Within the rudist-rich limestones, rudists are mainly represented by elevators such as hippuritids and radiolitids. Early lithification, common in all types of rudist limestones (NEGRA 1987, NEGRA