IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 45 



(1956) considered similar phosphate deposits in Kosseir area as a formation and 

 named it " the Duwi formation", nevertheless the present phosphate deposits 

 cannot be assigned to the same formation, as they are comparatively much reduced in 

 thickness. The " Sibaiya phosphate " either represents a dwarfed " Duwi forma- 

 tion " or only corresponds to a part of that formation. Until the two formations are 

 precisely correlated, it is advisable to treat them separately. 



The thick shale succession, which conformably overlies the Sibaiya phosphate 

 formation, and which is conmmoly referred to as the " Esna shales ", was recognized 

 by Ghorab (1956) as a formation which he named the " Esna formation " and divided 

 into three main members from the base upwards as follows : the " Dakhla ash-grey 

 shale member ", the " snow-white Ananchytes ovata chalk member ", and the 

 " Kharga paper shale member ". However, the present study shows that this thick 

 shale succession is actually a group of rock units naturally divided into two distinct 

 formations separated by a marked break and a well developed conglomerate. The 

 lower formation is here named " the Sharawna shale ", with its type section in the 

 Wadi El-Sharawna area, it has a thickness of about 120 m., and is proved to be of 

 Maestrichtian age. It includes three main members, a lower shale, a middle marl and 

 an upper shale member, the top part of which is truncated by a disconformity. 



The upper formation is here named " the Owaina shale ", with its type section in 

 Gebel Owaina, it also has a thickness of about 120 m. and is proved to be of Paleocene 

 age ; it includes two shale members separated by a middle chalk member. Its lower 

 limit is marked by the disconformity and its upper underlies the " Thebes calcareous 

 shale ". 



The uppermost succession of calcerous shale, shaly limestone, and limestone is here 

 assigned to the " Thebes formation ". However, the lower calcareous shale is 

 distinguished from the overlying " Thebes limestone " as a separate member of the 

 same formation and is given the name " Thebes calcareous shale " although it has 

 been wrongly assigned by various authors to the Esna shale. 



These different rock units are summarized in Text-figs. 5 and 8, their fossil content 

 is listed in Text-figs. 16 and 17 and their respective ages are discussed below. The 

 detailed lithostratigraphy of the succession and the lateral variation in the various 

 rock units are discussed elsewhere (El-Naggar in manu.), and the main sections 

 examined are correlated in Text-fig. 7. 



D. Discussion of the Age 



(1) The Nubia Sandstone and Variegated Shale Formation 



The Nubia sandstone and variegated shale could not be assigned a definite age 

 because of its scanty fossil content. However, as the formation is conformably over- 

 lain (in places) by the Sibaiya phosphate formation which is here considered as 

 Upper Campanian, and as the upper part of the Nubia formation contains rare 

 vertebrate remains which are identical to those of the overlying Sibaiya formation, 

 this upper part, at least, should be regarded as only slightly older than the overlying 



