Facies evolution and cyclic stacking patterns of the Ypresian Southern Tethyan carbonates: Insights from northern Egypt

Abstract This study aims to enhance the understanding of the paleoenvironmental evolution of Early Eocene Tethyan deposits. It focuses on the facies analysis, stratal cyclicity, and sequence stratigraphy of the Ypresian platform carbonates exposed in the north Eastern Desert of Egypt, which are considered a representative example of the Southern Tethys domain. Nineteen lithofacies types were identified and grouped into six principal facies associations: tidal flat, inner lagoon, inner shoal bar, open lagoon/back-bank, nummulitic-bivalve bank, and open-marine mid- to lower-shallow subtidal associations. These facies associations indicate deposition on a tectonically controlled, tropical-to-subtropical homoclinal ramp system. Paleoecological interpretations were derived primarily from the dominated fossil assemblages. The studied succession is organized into meter-scale, peritidal and subtidal shallowing-upward carbonate cycles, which are further subdivided into six subtypes; among which the dolostone-capped peritidal cycles are the most dominant subtype. Both intrinsic and extrinsic controls governed the stacking pattern of these cycles, reflecting the interplay between auto- and allocyclic processes. The recognized cycles are grouped into four depositional sequences, which are bounded by three tectonically-controlled sequence boundaries. These boundaries are expressed as densely karstified limestone horizons that record periods of subaerial exposure associated with tectonic uplift and pronounced sea-level fall. The succession is further correlated with equivalent successions in Egypt, the broader Tethyan realm, and the global eustatic sea-level curve to evaluate the influence of local/regional tectonics and sea-level fluctuations on ramp evolution. The integrated results suggest that tectonic activity associated with the rejuvenation of the Syrian Arc Orogeny, combined with eustatic sea-level changes and sediment accumulation rates, played a primary role in controlling the facies architecture and depositional evolution of the studied ramp system.