Abstract
The Upper Cretaceous Aruma Formation in central Saudi Arabia is subdivided into three members. The Khanasir Member at the base is characterized by dasycladecean-rudist biofacies. The middle Hajajah Member is characterized by coral-stromatoporoid biofacies, while the upper Lina shale Member contains few badly preserved molluscs. Fifty macrofossils species have been identified from the studied section, 25 of them belong to gastropods, 17 belong to scleractinian corals, and 8 species belong to bivalves. The identified macrofossils have close affinity to Tethyan faunas and previously known from the Cretaceous rocks in Asia, Africa, and Europe. The most recorded microfacies types are wackestones, packstones, and floatstones with green algae, benthic and rare planktonic foraminifers, ostracods, and corals. The studied section revealed a major Campanian-Maastrichtian marine transgression followed the continental siliciclastics of the Wasia Formation with progressive deepening upward, from a shallow marine lagoonal environment to relatively more open marine conditions.