THE QASR-AS-SAHABI SUCCESSION AND THE NEOGENE EVOLUTION OF THE SIRTE BASIN (LIBYA)

The Neogene succession in Libya is characterized by three main sedimentary cycles: 1. 1) A Middle Miocene cycle, involving the whole coastal area of Libya, composed of platform limestones in Cyrenaica and Tripolitania and of deeper deposits in the central part of the Sirte Basin; 2. 2) A Tortonian-Messinian cycle, composed of evaporitic, lagoonal and shallow oolitic deposits, well documented paleontologically in Sirtica between 30° and 31° lat. N. and above all near Qasr As Sahabi. These deposits are found westwards as far as A1 Khums, where they unconformably lie on the Cretaceous and older rocks. Northwards, they surround the structural high of Cyrenaica to beyond Benghazi. Along the western margin of Cyrenaica they lie on Middle Miocene limestones, and to the N-NW on the Eocene. They are bounded landwards by a scarp of marine erosion ("Upper Cyrenaica Escarpment") which models a system of normal faults; 3. 3) A cycle composed of presumed Pliocene coastal or brackish deposits covering a paleomorphology cut during the Upper Messinian regression. South of Cyrenaica, the Pliocene transgression extends beyond the Upper Miocene coastline as far as the A1 Jaghbub oasis. Seawards, the Pliocene cycle deposits are cut by another scarp ("Lower Cyrenaica Escarpment"). The interval between this scarp and the sea is covered by a further transgressive cycle of Tyrrhenian age. © 1990.