Sedimentology and sequence stratigraphy of shallow and deeper marine Miocene deposits: A case study from the St. Paul and Gebel El‐Zeit blocks, Gulf of Suez, Egypt

• Published in: Basin research Vol. 36; no. 1
• Main Author: El‐Azabi, Mounir H.
• Format: Journal Article
• Language: English
• Published: Oxford Wiley Subscription Services, Inc 01.01.2024
• Subjects: Alluvial fans; Brines; Carbonates; Climate change; Conglomerates; Evaporites; Evolution; facies architecture; facies model; Gulf of Suez rift basin; Lagoons; Miocene; palaeoenvironment; Sabkhas; Sedimentary facies; Sedimentary rocks; Sedimentology; Sequence stratigraphy; Sequencing; Shale; Stratigraphy; Tectonics; Thickness; Tidal flats; Gulf of Suez
• DOI: 10.1111/bre.12836
• ISSN: 0950-091X

Marginal and deeper marine facies typify the Miocene exposures along the western margin of the Gulf of Suez rift basin. The stratigraphic setting of these facies is a subject of debate and confusing at best. Integrative sedimentological and sequence stratigraphic study of successions exposed in the St. Paul and El‐Zeit blocks provides insight into the lateral relationships between the two facies and their evolution, a topic that is not fully understood. The St. Paul block, located at the basin margin, has thin shallow marine facies, while the succession of El‐Zeit block, situated near the basin axis, consists of basal conglomerates, thin shallow marine carbonates, thick deeper marine shale and marginal evaporites. The facies architecture of these successions is interpreted as belonging to two different depositional models: a fan‐delta/lagoon system followed upwards by an alluvial fans/sabkha‐tidal flat system in the St. Paul hangingwall basin, and carbonate–siliciclastic–evaporite systems on the hangingwall dip‐slope ramp of El‐Zeit block. These models may help understanding the sedimentary history of other similar blocks in the rift basin. The studied facies show many striking features such as deposition during tilting of fault block, abrupt facies and thickness variations, coarse clastic shedding, erosion channel filling, onlapping of high standing blocks and evaporite accumulation. These features are the result of major tectonic events that triggered the formation of unconformities at different hierarchical levels during the late early to middle Miocene. These unconformities subdivide the Miocene facies into five depositional sequences separated by basin‐wide erosional boundaries. This division greatly improves the age control of marginal marine facies. It affords new insight into the evolution of marginal marine facies along the western margin of the basin in relation to deeper facies in the basin centre. Facies and thickness changes in these tectonically induced sequences indicate that basin floor irregularities, subsidence rates, climatic changes, variable sediment influx, sea‐level/brine‐level changes and basin isolation/connection to the Mediterranean Sea are also important factors responsible for their evolution. The Miocene facies in the St. Paul and Gebel El‐Zeit display distinct features indicative of rift events, which greatly influenced facies characteristics and stratal architectures. The inferred sequences significantly improve the correlation of the Miocene facies, and enable a better understanding of the complex facies’ variations and their evolution.