Sedimentologic and paleotectonic evolution of carbonate platforms on a segmented continental margin: example of the African Tethyan margin during Turonian and Early Senonian times

Abstract

During Turonian and early Senonian times, there were extensive shallow-water carbonate platforms on the northern margin of the African craton (Eastern Algeria, Central Tunisia and adjacent offshore areas), at the edge of the Tethys ocean. The development of these carbonate platforms (mid-Turonian to late Coniacian) was especially controlled by the segmentation of the African (Saharan) margin by extensional fault systems, as evidenced by block-faulting, volcanic activity and halokinetic movements. From the mid-Turonian to early Coniacian times, the carbonate platforms underwent an incipient drowning, indicated both by their sedimentologic evolution (rimmed-shelves to carbonate ramps) and the landward shift of facies belts. A partial drowning of carbonate platforms during late Turonian times was probably induced by climatic and/or oceanographic changes. The late Coniacian is the period of continuation and further extension of deepening events with the widespread development of deep ramp facies. At the Coniacian-Santonian boundary, the sinking of the Saharan margin induced an abrupt increase of subsidence rates and the complete drowning of carbonate platforms, covered by deep-water argillaceous facies. This renewal of tectonic activity at the Coniacian-Santonian boundary is recorded in many areas in North Africa (“Intra-Senonian phase”).