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Ahmed M Muftah
Posters-Accepted Abstracts: J Geol Geosci
As Sahabi areas is one of famous vertebrate African localities situated in northern Africa, at the northern Sirt Basin of Libya. Its scientific value is due to the diverse and high abundance of vertebrate fossil remains. Hence, the dating of the exposed vertebratebearing member â??U1â? of Sahabi Formation in As Sahabi area using micro/macro invertebrates is the primary objective of this work. The data base is quite large including eight profiles and two subsurface shallow drilled wells from As Sahabi. Stratigraphically, the Late Neogene rock units of As Sahabi area are well differentiated and correlated by means of both biofacies and lithofacies changes as much as possible. The youngest â??Quaternaryâ?? rock unit (Formation â??Zâ?) is raised herein to be Formation rather than Member on the basis of the newly recognized unconformity. Whereas, the mineralogical and geochemical analyses are applied to the nonfossiliferous clayey intercalations in Sahabi Formation searching for any datable minerals or microfossil to solve the age enigma of Sahabi Formation, also implemented to understand the source area of the Sahabi clays. The mineralogical and geochemical study of clayey sediments from the vertebrate fossiliferous member of the As Sahabi Formation, using XRD and XRF analyses proved a continental origin from Neogene mega-Lake Chad. Paleontologically, several species have been described and illustrated for the first time from five macrofossils phyla (echinodermata, mollusca, corals, bryozoa and arthropoda) have been described in more detail to a speciation level in As Sahabi area particularly from formation â??Mâ?. Thirty-five foraminiferal species have been documented from As Sahabi area during this study, mostly from the Pre-Sahabi formation â??Mâ?; from which two assemblage biozones are established. Whilst, Sahabi Formation itself yields mainly shallower foraminiferal elements, with very low diversity and bad state of preservation. Seventeen ostracodes species from the pre-Sahabi rock unit (i.e. formation â??Mâ?) in As Sahabi area have been identified. In addition to that the Pre-Sahabi formation â??Mâ? from the subsurface data yielded diagnostic calcareous nannofossils, on which the dating is based. Integrated age of Late Tortonian age is assigned to The Pre-Sahabi Formation â??Mâ? based on the above-mentioned tools. Meanwhile the Sahabi Formation, Member â??Tâ? which is shallow marine deposits is dated as (post-Tortonian - ? Messinian); meanwhile the terrestrial- marginal marine deposits (Member U1, UD, U2 and V) are of Messinian or younger, base on Foraminiferal contents. Formation â??Zâ? is of Quaternary age.