The Albian-Cenomanian Transition in Central Tunisia: Insights from Jebel Mrhila

Three sections of the Albian-Cenomanian boundary have been studied in Jebel Mrhila of Central Tunisia. The Upper Albian succession directly overlies Aptian dolomites. It exhibits two depositional sequences and belongs to the M. fallax (?) to S. africana zones. The top of the Upper Albian series is eroded by a major discontinuity reflecting a major sea level drop. Deposition resumed in earliest Cenomanian times (N. carcitanense and S. schlueteri subzones) with two sequences of condensed sandy marls and dolomites. Both are capped by phosphate layers which are overlain by thick outer shelf marls (Early Cenomanian). Comparison with other areas suggests that during the Albian-Cenomanian transition, northern Central Tunisia acted as a bypass zone between the emergent southern areas and the northern basinal domain.