A palaeoenvironmental reconstruction of the Campanian‒lower Palaeocene succession of the Dakhla Oasis (Western Desert, Egypt): Insights from integrated sequence stratigraphy, macrobenthos, and trace fossil analyses

Abstract

The palaeoenvironments of the Campanian‒lower Palaeocene composite succession in the Dakhla Oasis, Egypt, are interpreted based on the integration of sequence-stratigraphy, macrobenthic associations, and trace fossils. This succession comprises six rock units, corresponding to several transgression-regression cycles. These rock units include the Quseir Formation, the Duwi Formation, and the Mawhoob, Beris, Lower Kharga, and Upper Kharga members of the Dakhla Formation. Six unconformities delineate seven 3rd-order depositional sequences, including the lower‒middle Campanian DS-Q1, the upper Campanian DS-D1 and DS-D2, the lower Maastrichtian DS-Dk1, the upper Maastrichtian DS-Dk2 and DS-Dk3, and the lower Danian DS-Dk4. The invertebrate macrobenthic elements sporadically occurred throughout the studied succession, representing three bivalve associations: the late Campanian Nicaisolopha-Plicatula association, the late Maastrichtian Exogyra overwegi association, and an early Danian Venericardia association. At least 12 ichnotaxa have been identified, representing two ichnoassemblages: the late Campanian Thalassinoides-Psilonichnus and the latest Maastrichtian‒early Danian Rhizocorallium jenense-Tisoa siphonalis, both belonging to the Glossifungites Ichnofacies. Sequences characteristics indicate palaeoenvironments ranging from brackish, littoral, and near-shore to inner and outer neritic settings, reflecting the influence of syn-sedimentary tectonics combined with sea-level fluctuations, which resulted in varied depositional features. The distribution and the trophic structure of the body and trace fossil assemblages confirm the role of several environmental parameters, such as substrate characteristics, bathymetry, water energy, productivity level, sedimentation rates, and oxygen availability, in shaping the occurrence of different elements within these faunal assemblages.