Biostratigraphically constrained age assessment and paleoenvironments of the early Miocene syn-rift deposits of the Gulf of Suez eastern margin, Egypt

Abstract

The absence or rarity of some global marker taxa in the semi-restricted Suez rift basin has led to uncertainty with respect to the age of the early syn-rift deposits. To tackle this issue, high-resolution foraminiferal and calcareous nannofossil biostratigraphy was undertaken on sections in the Wadi Baba area at the eastern basin margin. Two planktic foraminiferal bioevents of early Miocene age are recognized: First Occurrences (FOs) of Globigerinoides subquadratus and Trilobatus sicanus. These bioevents define three zones/subzones: MMi2b, MMi2c-MMi3 and MMi4. Calcareous nannofossil analysis provided the basis for the definition of three zones: CNM4 to CNM6 based on FOs of Helicosphaera ampliaperta and Sphenolithus belemnos, and the first common occurrence of S. heteromorphus. Our results assign a new age estimate of late Aquitanian to early Burdigalian (<19.01 Ma) for the Nukhul Formation, and Burdigalian to early Langhian for the Rudeis Formation, with three possible hiatuses.Integration of benthic foraminiferal biofacies, lithofacies and nannofossil paleoecological markers reveals a broad range of paleoenvironments, from shoreface to upper bathyal. The Nukhul Formation was deposited in nearshore, nutrient-rich, well-oxygenated conditions. Deeper water environments of neritic to upper bathyal prevailed during the Rudeis Formation. Comparison with coeval deposits in the offshore area of the basin reveals significant paleoenvironmental variability during the Burdigalian associated with episodic subsidence along basinal faults. Climate-sensitive taxa and oxygen isotope data indicate a prevalence of warm paleoclimatic conditions. Our results suggest the development of a seaway connecting the Gulf of Suez with the Mediterranean during the early Miocene rather than Chattian.