Sedimentary evolution of the Miocene syn-rift marginal and deeper marine facies in the Gulf of Suez rift basin, Egypt: A review

Abstract

The Miocene is a crucial epoch in the evolution of the Gulf of Suez basin. Its deposits experienced rapid and distinct spatial and temporal variations in facies and thickness due to deposition in a complex system of fault-bounded sub-basins that were continuously active throughout most of the Miocene. This review addresses the evolution of Miocene facies in the Gulf of Suez, which remains a major challenge, by integrating a detailed stratigraphic and sedimentological study. Two markedly different facies characterize Miocene deposits: marginal and deeper marine facies. Regionally traced unconformities intersect these facies, reflecting the nature of the tectonically active rift basin in which they accumulated. They define seven depositional sequences in the lower and middle Miocene facies exposed along the rift margins. Unconformities and related sea-level falls formed in response to major rift events, although some are associated with eustatic sea-level falls. The latter played an important role during the rift abandonment, when tectonic subsidence was slow. The evolution of Miocene facies reveals three distinct phases of rifting, each showing unique subsidence rate, sedimentation rate, structural relief, depositional systems, and facies architectures. These phases define four depositional stages, including the shallow marine stage, the open marine stage, the transitional stage, and the restriction stage. The first stage displays slow tectonic subsidence and initial marine invasion during the Aquitanian–early Burdigalian (Nukhul Formation). The second stage shows a rapid increase in rates of crustal extension, tectonic subsidence, and sedimentation during the early–late Burdigalian (Rudeis Formation), and a marked uplift of the rift shoulders in the late Burdigalian. The third stage indicates reduced rates of extension, subsidence, and sedimentation during the Langhian (Kareem Formation). The final stage shows a very slow subsidence with periodic water inflows from the Mediterranean during the Serravallian (Belayim Formation), and ends with an uplift in the northernmost Gulf of Suez basin that permanently isolates it from the north during the Tortonian–Messinian (South Gharib and Zeit formations). Facies attributed to the Gharamul and Gemsa formations, and the Sarbut El-Gamal Formation developed simultaneously along the western and eastern rift margins, respectively, during the second, third, and the lower part of the fourth evolutionary stages.