Integrated stratigraphy of the middle-upper Eocene Souar Formation (Tunisian dorsal): Implications for the Middle Eocene Climatic Optimum (MECO) in the SW Neo-Tethys

• Published in: Palaeogeography, Palaeoclimatology, Palaeoecology
• Main Authors: Messaoud, Jihede Haj, Thibault, Nicolas, Bomou, Brahimsamba, Adatte, Thierry, Monkenbusch, Johannes, Spangenberg, Jorge E., Aljahdali, Mohammed H., Yaich, Chokri
• Other Authors: The Ali I. Al-Naimi Petroleum Engineering Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia, Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen C., Denmark, Sfax National Engineering School, PB 1178, Soukra Road km 4, Sfax 3038, Tunisia. University of Sfax, Road of the Airport km 0.5, Institute of Earth Sciences (ISTE), University of Lausanne, Geopolis, CH-1015 Lausanne, Switzerland, Institute of Earth Surface Dynamics (IDYST), University of Lausanne, Geopolis, CH-1015 Lausanne, Switzerland, Marine Geology Department, Faculty of Marine Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia, Laboratory of Sediment Dynamics and Environment, Sfax National School of Engineers, PB 1173, 3038, Univ. of Sfax, Tunisia
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier BV 2021
• Subjects: Planktonic foraminifera
• Online Access: http://hdl.handle.net/10754/671171; https://doi.org/10.1016/j.palaeo.2021.110639

Calcareous nannofossil biostratigraphy and carbon-isotope stratigraphy on bulk organics of the middle-upper Eocene Souar Formation (Tunisia) allow for a refined stratigraphy of this interval in the southwestern Neo-Tethys margin. The Souar Formation represents the deepest sedimentary deposits of the central northern Tunisian Basin and was only dated previously by coarse data on planktonic foraminifera. Together with our new data, a correlation is proposed to previous Tunisian records of the Halk El Menzal carbonate platform to the NE and shallow-water deposits of central Tunisia to the SW, which leads us to the erection of a synthetic stratigraphic chart of the middle-upper Eocene in central and northeastern Tunisia. Our results allow for a review of the accurate position of the Lutetian / Bartonian and the Bartonian / Priabonian stage boundaries in Tunisia relative to calcareous nannofossil biohorizons. We apply Bayesian statistics to build our age-depth model which points to a hiatus in the Lutetian (CNE12 Zone) that we relate to the middle Lutetian regressive sequence leading to the Lu-4 M-cycle. Radiolarian-rich sediments and cherts of the late Lutetian and early Bartonian are interpreted as a response to an increase in productivity, tied to the seasonal upwelling of nutrient-rich waters. Correlation to other sections in Tunisia highlights the strong contrast in facies between the carbonate-rich sequences of the edges of the dorsal and the silica-rich deposition in the Souar Formation. This contrast is particularly pronounced in the interval before and across the Middle Eocene Climatic Optimum (MECO) characterized by a maximum of nummulitic carbonate production on the platform and a minimum of carbonate production in the deep basinal parts of the Tunisian dorsal, rather dominated by silica-rich sediments. Funding for this study was ensured through internal funds from the University of Copenhagen allocated to J.H.M. via the double-degree Ph.D. program. T.A. and N.T. also acknowledge the IGN International ...