Dr. Nagy I. Zoltán szerk.: Fragmenta Mineralogica Et Palaentologica 3. 1972. (Budapest, 1972)

Stratigraphy 1. Esna Shale The term Esna Shale was introduced early by BALL (1900) in comparing the shales above the chalk in Kharga Oasis with those exposed in the Nile Valley in the neighbourhood of Esna to which the designation "Esna Shale" has been applied in reports of the Geological Survey. The 3sna Shale is a uniform rock unit which has a wide extention in Egypt. It has been described from widly separated localities as the Parafra Oasis, Kharga Oasis in the West and the eastern extremely of the Sinai Penninsula in the east and in the Nile Valley. Although it shows minor variations in thickness and lithology, its stratigraphie position above the chalk and below the Operculina limestone (Thebes formation) makes it one of the best well established mappable units in the Egyptian Stratigraphie Column. HUMS (1911) and some other authors NAKKADY (1957), YOUSSEP (1957) divided this unit into an "Upper Esna Shale" overlay the Chalk and underlay the Operculina limestone; and the "lower Esna Shale" to the succession of gray laminated shale that underlay the chalk, which described by ZITTEL (1883) as "grünlich und Aschgraue Blätterthone". SAID (196I) replaced the term "Dakhla Shale" to the lower Esna Shale, and the "Esna Shale" to designate the succession of "laminated grean and grey, shaly clays" that overlei the chalk and underlei the Thebes formation or the Parafra limestone.