Cenomanian–Turonian depositional history of a post–Gondwana rift succession in the West Beni Suef Basin, Egypt

Abstract

The structural and stratigraphic evolution of rift basins has been documented globally from modern systems, outcrop and subsurface datasets. Extensive fragmentation and break-up of Gondwana during the Cretaceous created a complex suite of rift basins in the Northern Africa. The Beni Suef rift basin straddles the River Nile and is infilled by a thick Mesozoic–Tertiary succession. Cenomanian–Turonian deposition commenced with the sandstone-dominated Bahariya Formation. Depositional environments transitioned stratigraphically from fluvial-marine to shallow marine and finally to mixed clastic and non-clastic shelfal deposits of the Abu Roash Formation. Sedimentation styles were tectonically controlled showing transgressive-to-regressive depositional cycles developed over the Gondwana rift systems. Cycles were controlled by short-lived, small-scale tectonic oscillations of the platform, resulting in four depositional sequences. Deposition environments in the Cenomanian transitioned from shallow marine to deeper marine shelfal deposits and finally to a coastal environment. During Late Cenomanian–Early Turonian, rapid platform submergence resulted in a transgressive facies succession, topped by deltaic deposits. In the Middle–Upper Turonian, two sequences formed with an intervening short-lived period of lower relative sea level. Relative sea-level oscillations were partly in phase with the global sea-level changes, controlled by local tectonics induced by the fragmentation of Gondwana during the Late Cretaceous.