Paleogeography and Sedimentation History of the Western Libya Offshore, Central Mediterranean*

The Gabes-Tripoli Basin (G-T Basin) is a Mesozoic-Cenozoic basin which was initiated as a result of widespread, late Triassic-Middle Jurassic extensional movements that developed over a broad zone of strain between the African and European plates. The subsurface analysis of the whole succession within the G-T Basin was carried out to unravel the subsurface aspects of the different depositional sequences and to interpret the overall basin evolution history. The method simply involves the subdivision of the whole sedimentary succession into tectonostratigraphic megasequences, all of which are linked in one way or another to regional tectonic episodes that can be correlated with the Mediterranean basin tectonic history. The sedimentary succession in the G-T Basin ranges in age from Triassic-Recent. It comprises a 10 km-thick succession of pre-rift EarlyMiddle Triassic, nonmarine and marine clastics, syn-rift Late Triassic-Middle Jurassic, predominantly shallow marine carbonates and evaporites and Middle Jurassic-Recent post-rift marine carbonates and clastics. The tectono-stratigraphic units comprise 7 main sequences on the time scale of second order sequences. For most sequences and sequence boundaries, either a eustatic or tectonically enhanced origin can be established. The analysis of the basin-fill history of the G-T Basin from the Triassic until the Holocene reveals that the basin underwent development from a continental sedimentary basin located on Gondwana to an epicratonic rift basin. When extensional movement ceased (Middle Jurassic), the basin subsided thermally and developed as part of a passive continental margin on the North African plate margin. Correlation with the out cropping sequences at Jabel Nafusa reveal the HC potential of the Triassic Azizyiah and Abushaybah play and lead to the identification of a new lithostratigraphic unit, the Late Albian-Cenomanian Jennawen Formation.