The present study deals with the sedimentology, mineralogy and geochemistry of the Middle Eocene ironstones of the northeastern part of the Bahariya Depression, Western Desert, Egypt. It also focuses on the microbial role in the precipitation of these ironstones. The ironstone succession rests unconformably on three latertitized Cenomanian paleohighs (e.g. El Gedida, El Harra and Ghorabi mine areas). The ironstone succession is composed of autochthonous/para-autochthonous facies rich in ferruginous ooids, oncoids and skeletal particles. The ironstone facies assemblages are stacked in two...