Factors controlling facies distribution during the early Late Cretaceous in the Eastern Desert of Egypt: Paleoenvironmental reconstruction and relationship to sequence stratigraphy

Abstract

In the context of a high-resolution stratigraphic perspective, facies analysis is carried out to interpret the paleoenvironments that prevailed during the Cenomanian–Turonian sedimentation in the Eastern Desert of Egypt. Particular emphasis is placed on the possible reasons for observed changes in the facies distribution. The facies associations indicate that the mixed carbonate and siliciclastic successions were deposited on a long-extended ramp setting with a gentle dip from a proximal position in the south to a distal position in the north. The late Cenomanian transgression covered the study area and formed a shallow fully marine environment, in which the Galala Formation was deposited. The sea-level rose continuously to reach a maximum during the early Turonian, with a deep subtidal setting in which the Maghra El Hadida and Abu Qada formations were deposited at relatively high and low paleo-depths, respectively. Changes in the facies distribution reveal a strong relationship to sea-level fluctuations; each sea-level stage of the studied sequences is characterized by similar facies associations with the same facies arrangements. In addition, at the proximal southern part of the study area, where shallow facies are expected to occur, deep marine facies are instead recorded, which is interpreted here as a tectonic effect of the Syrian arc folding system. Furthermore, the dominant paleoenvironmental perturbations during the Cenomanian–Turonian as represented by major lateral and vertical litho- and biofacies changes also affected the studied facies distribution. Therefore, the Cenomanian–Turonian facies development in northeast Egypt was not only controlled by eustatic sea-level changes as commonly suggested but was also influenced by tectonic and environmental changes.