ORIGINAL PAPER Stratigraphy and depositional environments of the Upper Cretaceous Aruma Formation, Central Saudi Arabia Khaled M. Al-Kahtany 1 & Abdelbaset S. El-Sorogy 1,2 & Mohamed Youssef 1,3 & Hisham A. Gahlan 1 Received: 25 August 2015 /Accepted: 26 January 2016 # Saudi Society for Geosciences 2016 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 macro- fossils 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 mac- rofossils 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. Keywords Stratigraphy . Depositional environments . Upper Cretaceous . Aruma Formation . Central Saudi Arabia Introduction Since the old studies of Steineke and Bramkamp (1952); Steineke et al. (1958); Powers et al. (1966); Powers (1968), (El As’ad 1977, 1983a, b, 1984), and Vaslet et al. (1988), there are no studies dealt with stratigraphy and depositional envi- ronment of the Aruma Formation in central Saudi Arabia. Skelton and El Asa’ad (1992) identified new genus and spe- cies of canaliculated rudist from of the Campanian Khanasir Member of the Upper Cretaceous Aruma Formation in Central Saudi Arabia. Al-Furaih (1984a, 1984b, 1986) studied the Maastrichtian ostracods of Aruma Formation from Wadi al- Atiq. He identified, described, and illustrated one new genus and 15 new species. Studies of Okla ( 1991, 1992, 1994, 1995) were on Cretaceous fossil algae, especially dasycladaceans. He identi- fied new dasycladecean species from surface samples of the Aruma Formation in northeast of Riyadh, Saudi Arabia. Recently, Gameil and El-Sorogy (2015) identified 15 gastro- pod species from the present section, mainly from the Hajajah Member and indicated shallow marine lagoonal and relatively open marine environment. None of the last mentioned studies have dealt with stratig- raphy and depositional environments; therefore, the present work aims to study stratigraphy and to document the deposi- tional environments of the Upper Cretaceous Aruma Formation in Central Saudi Arabia based on microfacies anal- ysis and macrofossils content. Materials and methods A composite section was measured and macrofossils and rock samples were collected from Khashm Bowaibiyat area, Northeast Riyadh (Fig. 1) Gastropods, scleractinian corals, * Khaled M. Al-Kahtany kalgatani@ksu.edu.sa 1 Department of Geology and Geophysics, College of Science, King Saud University, P.O Box: 2455, Riyadh 11451, Saudi Arabia 2 Department of Geology, Faculty of Science, Zagazig University, Zagazig, Egypt 3 Department of Geology, Faculty of Science, South Valley University, Qena, Egypt Arab J Geosci (2016) 9:330 DOI 10.1007/s12517-016-2361-6