120 DE. W. F. HUME ON SECULAK OSCILLATION IN EGYPT [Feb. I9II, 



(A) The Cretaceous Strata of Northern Egypt. 



In Egypt the northernmost Cretaceous belt, extending from 

 Southern Sinai through the Gebel Ataqa and Galala Hills to Abu 

 Roash, with a western extension in the Baharia Oasis, is charac- 

 terized by a great development of limestones daring Danian, 

 Senonian, and Turonian times. 



The Cenomanian beds are also highly fossiliferous, but the strata 

 are marls in Sinai and of a more sandy nature in the Baharia Oasis. 

 The unfossiliferous Nubian Sandstone immediately underlies the 

 Cenomanian, and typical sandstones nowhere reappear 

 higher in the section. A typical succession for this Northern 

 type is displayed in the plateau-edge of Gebel Gunna, in Eastern 

 Sinai, as follows : — 



Thickness in metres. 

 (Top.) 1. Ferruginous limestones. Some of these beds contain 

 traces of diademoid sea-urchins, and suggest a parallelism 

 with the Lower Senonian beds near Wadi Qena subsequently 

 described 61 



2. Limestones or green marls containing EchinobHssus humei 



Fourtau, and Cyphosoma aff. rnajus Coq. : the presence of the 

 latter points to these beds being still of Turonian age. 



3. Bivalve-cast limestone. 



4. Ostrea-olisipo?iensis Limestone, associated with Ostrea rouvillei 



Coq. 



5. Green marls containing Periaster oblongus Dune, Tylostoma 



elatius Coq., and Heterodiadema libycum Cott. Also numerous 

 sea-urchins described by Prof. J. W.Gregory 1 3*5 



6. Loose sandstone and marls, containing large specimens of Ostrea, 



olisiponensis Sharpe in abundance 14 



7. White grits of the Nubian Sandstone, calcareous in the upper 



10 metres 200 



The typical Cenomanian beds in this section have not been 

 recognized in the Abu Roash district ; but that area may still be 

 retained in the northern division, owing to the great development 

 of Turonian, Senonian, and Danian limestones. 2 In Baharia, 

 on the other hand, the fossiliferous Cenomanian strata with charac- 

 teristic oysters and sea - urchins are well - developed ; but the 

 Turonian and Senonian formations are not so clearly marked as 

 elsewhere, or lie in regions more difficult of study. 3 



(B) The Cretaceous Strata of the Wadi Qena Area. 



During the season of 1910, a very interesting region was explored 

 at the head of Wadi Qena, in the Eastern Desert of Egypt — the 

 study revealing an unexpected transitional phase, characterized by 

 alternations of sandstones and Upper Cretaceous limestones. 



1 Geol. Mag. dec. 5, vol. iii (1906) pp. 216-27 & pis. x-xi. 



2 H. J. L. Beadnell, Egypt. Geol. Surv. Eeport (1900) pt. ii, « The Creta- 

 ceous Region of Abu Roash,' 1902, in which reference will also be found to 

 the work of other authors in this area. 



3 See J. Ball & H. J. L. Beadnell, Egypt. Geol. Surv. Memoir on Baharia 

 Oasis, 1903. 



