This chapter provides further details on the geological information on the evolution of the Nile River and the geological history of the rock units that make up the Fayoum Nile Delta. Since the Cretaceous Period or before, the rifted Ethiopian Mountain was believed to be the site of the Nile River's origins. Originating from the Ethiopian Mountains, the Nile River carved its way across Sudan and Egypt, spanning from the Cretaceous to the lower Eocene, until it reached the west of Beni Mazar, nearly at latitude 27 50 N (now Minia Governorate). At this place and during the Middle Eocene, the Nile River moved westward and invaded the Fayoum Province and was carved through the Middle Eocene El Gharaq Formation and proceeded northwestwards, depositing the Middle Eocene Gehannam and Qaroun formations, Miocene El Khashab and Moghra formations, creating a fan-shaped delta oriented northwest direction (Fayoum Nile Delta) in the northwestern desert. A prodelta is where the Gehannam and Qaroun formations were deposited. During the Late Eocene time, the sea level declined, and subsequent northward regression resulted in the deposition of the Qasr El Sagha Formation in the delta front setting. In the late phase of the Fayoum Nile Delta, the Qatrani, El Khashab, and Moghra formations were deposited in the delta plain and/or at a riverine subaerial delta setting. The concentration of different vertebrate species at Wadi El Hitan and their absence in the equivalent rock units in the Eastern Desert (Qarara, El Fashn, and Beni Suef formations) and the Western Desert (Hamra Formation, Bahariya Oases) indicate that this region was the site of debouching the water of the Nile River. The concentration of vertebrates at the Fayoum Province in general and Wadi Hitan in particular, west of the Fayoum Province, may be attributed to the enrichment of the River Nile sediments with nutrients, enhancing the growth and recovery of these animals.