Cenozoic palaeogeographic development of northern Tunisia, with special reference to the stratigraphic record in the miocene trough

Abstract

Cenozoic deposits are present in five northeast-trending provinces of northern Tunisia, from northwest to southeast: the Numidian belt, the western (Brjaoua) and eastern (Bou Sefra) parts of the Miocene Trough, the Fortuna Basin, and the Eastern Platform. The critical Bou Sefra sequence is an essentially complete fossiliferous Miocene succession. These Cenozoic deposits record six episodes: (1) Widespread Paleocene and Eocene Tethyan transgression flooded the entire region. (2) During Oligocene time the inner part of the northwestern cratonic margin was uplifted and eroded while a pelagic facies filled a northeast-trending precursor of the Fortuna Basin. At the same time a shallow marine facies prevailed to the east, south, and west. (3) Increased Early Miocene deformation in the Fortuna Basin area led to accumulation of thick, conglomeratic deltaic to alluvial sandstone which graded laterally into shallow marine deposits on the Eastern Platform. Neritic sediments also accumulated along much of the Miocene Trough to the west, and later spread eastward over the Fortuna Formation. Farther northwest a thick succession of sandy Numidian turbidites was deposited along the outer continental margin of north Africa. (4) In Middle Miocene time Numidian nappes were emplaced in the northwest while deformation and local uplift within the Miocene Trough was accompanied first by marine marl and mud and then by accumulation of a muddy flyschoid facies that graded into neritic to paralic deposits farther east. (5) During late Miocene time uplift and erosion prevailed in the far northwest while a shallow marine facies in the Miocene Trough was succeeded by evaporite-bearing neritic to paralic deposits before the end of the Miocene Epoch. Neritic to paralic facies dominated the eastern part of the Fortuna Basin area and the Eastern Platform throughout this episode. (6) Intense deformation at the end of Miocene time produced uplifts in the northwest and along the Tunisian Atlas flanked by coarse-grained nonmarine Pliocene deposits, as well as local subsidence and marine basin fill in the Bizerte area in the northeast and on Cap Bon Peninsula to the east.