Lithofacies and Petroleum Geoheritage of the Upper Jurassic Arab-D Member: Insights from the Eastern North Riyadh UNESCO Global Geopark, Saudi Arabia

The Kimmeridgian Arab Formation (D Member) represents one of the most significant petroleum reservoirs in the world. The Degla section, situated in the eastern part of the North Riyadh UNESCO Global Geopark, offers outstanding natural exposures that preserve a diverse array of carbonate lithofacies and a rich assemblage of trace fossils. This study investigates the vertical facies transitions, depositional environments, and ichnological characteristics of the Arab-D Member, utilizing the Degla outcrops in the Eastern North Riyadh UNESCO Global Geopark as a surface analogue for characterizing the world's largest subsurface reservoir. Detailed sedimentological and petrographic analyses reveal a complex interplay of microbial, skeletal, and evaporitic facies, reflecting the dynamic nature of shallow-marine depositional systems. The results enhance our understanding of reservoir heterogeneity, diagenetic evolution, and the broader significance of the Arab-D succession in terms of petroleum geoheritage.