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<p>The present work aims to study the microfacies, depositional environment, and foraminiferal biostratigraphy of the Upper Miocene Benghazi Formation at the As Sahabi area in Ajdabyiah Trough, eastern Sirt Basin. It has been measured, described, and sampled from the type section at the P53 locality. Seventeen samples have been collected and subjected to both petrographic thin sections analysis and a foraminiferal investigation. Lithologically, the Benghazi Formation in the study area is dominated by carbonates, siliciclastics, and evaporites. The biogenic components of the examined Benghazi Formation consist of microfossils (planktic foraminifera, larger foraminifera, small benthic foraminifera, bryozoans, ostracods&#xa0;and bony fish teeth), whereas the macrofossil content includes bivalves, gastropods, echinoids, barnacles, coral, and coralline red algae (rhodolith algae). Detailed analyses of lithology, paleontology, and petrography of the Benghazi Formation led to the discrimination of eight sedimentary microfacies types forming four shallowing-upward cycles and one deepening-upward cycle. These facies include one type of clastic facies (F1: claystone) and seven types of grain-supported carbonate facies (F2: sandy algal dolomitic packstone, F3: ostracodal pelletal limestone, F4: gypsified bioskeletal limestone, F5: sandy bioclastic floatstone, F6: gypsiferous fossiliferous limestone, F7: sandy foraminiferal-bioclastic packstone, F8: planktic foraminiferal-argillaceous packstone). They have accumulated in a range of depositional environments from continental lacustrine setting to marine inner shelf (open lagoon, restricted lagoon, and shoal) and middle shelf environments. Taxonomically, a total of 49 species belonging to 27 genera of foraminifera were identified. Their stratigraphic distribution allowed the establishment of two successive biozones, the late Tortonian <i>Neogloboquadrina humerosa/Nq. acostaensis </i>concurrent rang Zone and the Tortonian-Messinian <i>Borelis melo melo</i> total rang Zone. This study also discussed the local paleogeographic distribution of the Middle to Late Miocene marker <i>Borelis melo melo</i> from various Libyan sections.</p>

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Microfacies analysis, depositional environment and foraminiferal biostratigraphy of the Upper Miocene Benghazi formation, P53 locality, as Sahabi area, NE Libya

  • 期刊论文

  • 发表日期：

    2025年8月3日

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  • Mohammed F. El Hassi

摘要

The present work aims to study the microfacies, depositional environment, and foraminiferal biostratigraphy of the Upper Miocene Benghazi Formation at the As Sahabi area in Ajdabyiah Trough, eastern Sirt Basin. It has been measured, described, and sampled from the type section at the P53 locality. Seventeen samples have been collected and subjected to both petrographic thin sections analysis and a foraminiferal investigation. Lithologically, the Benghazi Formation in the study area is dominated by carbonates, siliciclastics, and evaporites. The biogenic components of the examined Benghazi Formation consist of microfossils (planktic foraminifera, larger foraminifera, small benthic foraminifera, bryozoans, ostracods and bony fish teeth), whereas the macrofossil content includes bivalves, gastropods, echinoids, barnacles, coral, and coralline red algae (rhodolith algae). Detailed analyses of lithology, paleontology, and petrography of the Benghazi Formation led to the discrimination of eight sedimentary microfacies types forming four shallowing-upward cycles and one deepening-upward cycle. These facies include one type of clastic facies (F1: claystone) and seven types of grain-supported carbonate facies (F2: sandy algal dolomitic packstone, F3: ostracodal pelletal limestone, F4: gypsified bioskeletal limestone, F5: sandy bioclastic floatstone, F6: gypsiferous fossiliferous limestone, F7: sandy foraminiferal-bioclastic packstone, F8: planktic foraminiferal-argillaceous packstone). They have accumulated in a range of depositional environments from continental lacustrine setting to marine inner shelf (open lagoon, restricted lagoon, and shoal) and middle shelf environments. Taxonomically, a total of 49 species belonging to 27 genera of foraminifera were identified. Their stratigraphic distribution allowed the establishment of two successive biozones, the late Tortonian Neogloboquadrina humerosa/Nq. acostaensis concurrent rang Zone and the Tortonian-Messinian Borelis melo melo total rang Zone. This study also discussed the local paleogeographic distribution of the Middle to Late Miocene marker Borelis melo melo from various Libyan sections.