Senonian platform-to-slope evolution in the tectonically-influenced Syrian Arc sedimentary belt: Beni Suef Basin, Egypt

Abstract

The Beni Suef Basin is a rift basin that was formed in the Early Cretaceous in response to the break-up of the Gondwana. The infill consists of a thick Mesozoic–Paleogene succession deposited during two main tectonic phases; the Early Cretaceous syn-rift phase and the Late Cretaceous post-rift phase. The post-rift phase was subsequently subjected to an intense compressional tectonic regime related to late Cretaceous Syrian arc tectonics. Within the basin-fill succession, the Senonian deposits, which are composed of carbonates and mixed siliciclastic/carbonate rocks of the “B” and “A” members of the Abu Roash Formation, was formed as a marine platform developed under fluctuated shelfal conditions. These deposits were overlain by chalk of the Khoman Formation that is interpreted to have formed in an outer shelf–middle slope setting. The Senonian succession is subdivided into two 3rd order depositional sequences (Latest Turonian–Early Coniacian SQ-1 and Coniacian–Santonian SQ-2) and one 2nd order depositional sequence (Campanian–Maastrichtian SQ-3). The depositional history of the Senonian in the Beni Suef Basin is interpreted to have been controlled by variable sedimentation accompanied by progradation and retrogradation of carbonate platform between inner and outer shelf environments during the Coniacian–Santonian, and between inner shelf and upper slope environments during the Campanian–Maastrichtian to the end of Senonian. The changes in depositional environments and relative sea-level fluctuations were a factor of the variations in accommodation and sedimentation likely controlled primarily by the Syrian Arc tectonic pulses, which may also have affected basin development and that of the surrounding areas over the northern Western Desert of Egypt particularly during Senonian.