ASGP (2023), vol. 93: 381–409

INTEGRATED MICROFACIES, MACROBENTHOS AND TRACE-FOSSIL ANALYSIS OF THE LOWER‒MIDDLE MIOCENE SUCCESSION OF GEBEL GHARRA, CAIRO-SUEZ DISTRICT, EGYPT

Mona MANDOR (1), Magdy EL HEDENY (1*), Ahmed EL-SABBAGH (1), Emad NAGM (2,3), Abdelaal ABDELAAL (1), Mohamed RASHWAN (4) & Heba MANSOUR (4)

1) Department of Geology, Faculty of Science, Alexandria University, Alexandria 21568, Egypt; e-mail: magdy.elhedeny@alexu.edu.eg
2) Department of Geology, Faculty of Science, Al-Azhar University, Assiut, 71524, Egypt
3) Department of Geology, College of Science, Taibah University, Madinah, 41477, Saudi Arabia
4) Department of Biological and Geological Sciences, Faculty of Education, Alexandria University, Alexandria 14037, Egypt
*) Corresponding author

Mandor, M., El Hedeny, M., El-Sabbagh, A., Nagm, E., Abdelaal, A., Rashwan, M. & Mansour, H., 2023. Integrated microfacies, macrobenthos and trace-fossil analysis of the lower‒middle Miocene succession of Gebel Gharra, Cairo-Suez District, Egypt. Annales Societatis Geologorum Poloniae, 93: 381–409.

Abstract: The palaeoecology and palaeoenvironments of the lower–middle Miocene succession in Gebel Gharra, NW of Suez, Egypt, are interpreted, on the basis of a detailed study of microfacies, trace fossils, and macrofaunal benthic assemblages. This succession consists of a lower siliciclastic part (the Gharra Formation) and a carbonate-dominated upper part (the Geniefa Formation), corresponding to a general transgression-regression cycle. Facies characteristics indicate depositional palaeoenvironments, ranging from supratidal, lagoonal, to shoal settings on an inner ramp that was influenced proximally by clastic input. At least seven ichnotaxa were recorded in the lower Miocene Gharra Formation, representing suites of the Skolithos ichnofacies. Among them, the ichnogenus Polykladichnus is recorded for the first time in Egypt. The macrobenthic taxa identified in 13 statistical samples are grouped into five assemblages (A–E) that are described and interpreted as the remains of communities. The faunal distribution and trophic structure of most of these assemblages confirm the existence of relatively stable and low-stress conditions. However, the trophic structure of the assemblages reflects the influence of particular environmental parameters, the dissolution of aragonitic shells and/or sample-size effects. Environmental parameters, controlling the distribution of trace and/or body fossils, include substrate consistency, bathymetry, water energy, productivity level, rate of sedimentation, salinity, and oxygen availability. The results of integrated lithoand biofacies analysis confirm that the succession studied was deposited in different environmental settings, providing perfect conditions for the occurrence and preservation of trace-fossil and macrobenthos assemblages.

Manuscript received 11 March 2023, accepted 30 June 2023