The Oligo–Miocene deep-marine siliciclastic succession of the Levant Basin constitutes one of its most stratigraphically and economically significant sequences. This ~4–6 km-thick section was primarily supplied by an ancient sediment-routing system from East Africa to the eastern Mediterranean, which later evolved into the modern Nile River. Over the past ~5 million years, Nile sediments have accumulated close to the river mouth, forming the present arcuate delta. In contrast, during the Oligo–Miocene, East African sediments were transported hundreds of kilometers into the deep Levant and Herodotus basins. Understanding why delta formation was delayed until the Pliocene–Quaternary is key to constraining the processes and boundary conditions that govern delta development.
To investigate the controls on sediment distribution in this deep-marine system, we employ the diffusion-based forward stratigraphic modeling software Dionisos. We first compiled a new Oligo–Miocene thickness map using Israeli offshore datasets, complemented by thickness maps and well data from offshore Lebanon and Egypt. Based on this compilation, we reconstructed the paleobathymetry of the Herodotus–Levant Basin at the beginning of the Oligocene (~34 Ma) by unloading younger sediments and accounting for flexural isostasy and sediment decompaction. This reconstruction was implemented in Dionisos using diffusion coefficients calibrated in a previous study of the ~5 Ma Nile Delta, allowing direct comparison between Oligo–Miocene and Pliocene–Quaternary conditions.
Among the parameters explored, our results highlight basin geometry as a first-order control: During the Oligo–Miocene, the basin was sufficiently deep for sediments to bypass the steep continental margin and accumulate in distal basin settings. Progressive infilling by thick Oligo–Miocene siliciclastics and Messinian evaporites reduced basin gradients, favoring near-shore sediment accumulation and development of the giant Pliocene–Quaternary delta. These results underscore the importance of internal basin dynamics as a key control on conditions favorable for delta formation.