Late Campanian-Maastrichtian foraminiferal biostratigraphy and paleoecology at Wadi Tarfa (North Eastern Desert, Egypt)

Abstract

The upper Campanian-Maastrichtian (from Globotruncanella havanensis to Plummerita hantkeninoides zones) foraminiferal assemblages at the Wadi Tarfa section in the Egyptian North Eastern Desert are studied to infer paleoenvironments and relative sea-level changes. The multivariate R-mode hierarchical clustering and the Q-mode Nonmetric Multi-Dimensional Scaling (NMDS) of the benthic foraminiferal dataset have been attempted to quantify the vertical variations in paleobathymetry, oxygenation, and trophic conditions. The inferred foraminiferal-based sea-level curve reveals paleodepth fluctuations ranging from middle neritic to upper bathyal and distinguishes five 3rd order sequences, two in the upper Campanian and three in the Maastrichtian. The development of the inferred relative sea-level curve expresses greater control of the eustasy. Also, the regional impact of the Syrian Arc Orogeny (SAO) subordinately led to amalgamation and repositioning of some sea-level events. The lowermost part (Gl. havanensis Zone) was deposited under stressed, low oxygenated, weakly eutrophic bottom-water conditions. However, well‑oxygenated oligotrophic conditions occurred around the level of the Campanian/Maastrichtian (C/M) boundary, as inferred from the predominance of heavily calcified epibenthic oxic species. We attributed this oligotrophy to the oceanic circulation change and the accompanying climatic cooling experienced at that time. The remainder of the early Maastrichtian through late Maastrichtian experienced an environmental shift toward mesotrophic conditions without considerable oxygenation change. The latest Maastrichtian, however, reveals low-oxic mesotrophic-weakly eutrophic bottom-water conditions, which is likely owed to the Deccan volcanism induced food detritus enrichment.