Sea-Level and Environmental Change Across the K/Pg Boundary and PETM Event on the Southern Tethyan Margin: Foraminiferal and Sequence-Stratigraphic Evidence from Egypt

Upper Cretaceous–Lower Paleogene successions along the southern Tethyan margin record the combined effects of global environmental perturbations, relative sea-level change, and regional tectonism. This study reconstructs paleoenvironmental and sequence-stratigraphic evolution across Maastrichtian–Ypresian strata in four Esh El-Mellaha sections, northern Eastern Desert, Egypt, using integrated lithostratigraphy, microfacies, benthic foraminiferal assemblages, faunal indices, quantitative paleodepth estimates, and sequence-stratigraphic analysis. The exposed succession comprises the Sudr, Dib, Esna, and Thebes Formations and includes intervals spanning the Cretaceous/Paleogene (K/Pg) boundary and the Paleocene–Eocene Thermal Maximum (PETM). Two major erosional surfaces are recognized: the Sudr/Dib boundary, associated with an incomplete K/Pg transition and a latest Maastrichtian–early Danian hiatus, and the Dib/Esna boundary, related to Late Paleocene erosion/non-deposition during the Selandian–Thanetian interval. Four benthic foraminiferal biofacies indicate deposition mainly in middle-neritic to upper bathyal settings, with pronounced shallowing during Dib Formation deposition. Foraminiferal trophic-oxygen signals indicate contrasting ecological responses, with comparatively oxygenated, low-productivity conditions in the strata bracketing the K/Pg interval and increased organic flux, dysoxia, and opportunistic infaunal taxa during the PETM. Five depositional sequences and five sequence boundaries provide a refined Maastrichtian–Ypresian framework, showing that global eustatic and environmental signals were locally modified by Syrian Arc-related accommodation changes.