Effets des oscillations eustatiques couplées à une tectonique syn-sédimentaire sur la marge sud de la Téthys au Sénonien: exemple du Jebel Mʹrhila, Tunisie centrale

The Senonian deposits that crop out in the Jebel Mʹrhila area of central Tunisia record signs of six third-order eustatic oscillation cycles. These may be totally or partially correlated with the global cycles. According to the planktonic foraminifera and ostracod distributions, the deposits are Late Coniacian–Maastrichtian p.p. in age. Their setting and stacking were simultaneously controlled by relative sea-level changes and local tectonic tensional movements. This local syn-sedimentary tectonic activity affected the palaeogeography of the Jebel Mʹrhila area, creating a stepped submarine topography in which the medial part was uplifted and became emergent after the Late Turonian. During the Senonian, the Jebel Mʹrhila area became integrated with the circa-littoral Tethyan domain where deposits rich in planktonic foraminifera were episodically injected by carbonate and siliciclastic gravity-flow sediments. The latter were re-mobilized from shoals towards adjacent troughs. The Jebel Mʹrhila exposure is a local but a significant example of the Tunisian succession and that of the south Tethyan margin as a whole.