Tidal Influnced Eocene Deposits of Dur At Talah (Libya) Compared with Present DayTidal Sediments from the Bay of MT St Michel (France)

Dur At Talah escarpment is located in south central Libya, the southern peripheries of Sirt Basin. The escarpment (height ≈ 130m and length ≈ 150 km.) can generally be considered as the exposed part of Abu Tumayam Trough. The outcrop is built up with marine to deltaic clay, silty clay and various sandstones, it is attributed to the Upper and uppermost Eocene time. Only a few field studies have previously been carried out to this area, those were mainly attracted to its vertebrate fossil-content. For the moment, sedimentology and depositional environment are poorly documented.
Taking into consideration the importance of Dur At Talah escarpment outcrop, at the southern fringes of the large hydrocarbon bearing Sirt Basin, this paper aimed at defining the main facies, encountered in the exposed sequence. Sedimentological investigation suggested that the greatest part of the outcrop, which is the lower and the middle (approx. the lower 100 m.) parts, are strongly tidal dominated. The upper part therefore, appears to show smooth changing from tidal to ‘pure’ fluvial, probably includes mouth bar environments. In order to compare the Libyan tidal facies exposed in this outcrop, to modern ones, several field trips were conducted to the modern “macrotidal” environment of the Bay of Mont St Michel, France. The comparison would contribute to the understanding of the sedimentological sequence encountered in Dur At Talah area. Main results, especially the comparison between fossil and modern environments are presented in this paper.