Vol. 67.] DURING THE CRETACEOUS AND EOCENE PERIODS. 131 



VII. Transition from the Cretaceous to the 

 Eocene Period. 



The gradual advance of the Cretaceous sea over the greater part 

 of Egypt having thus been proved in a very convincing manner, 

 we have next to enquire what were the changes which led to the 

 remarkable dissimilarity between the Eocene and the Cretaceous 

 faunas. Egypt has long been regarded as a striking illustration 

 of lithological continuity, when the strata formed during the two 

 periods are compared ; but close study of the two formations reveals 

 some suggestive differences in the relations existing between them 

 in various parts of the country. 



In the South of Egypt the junction between Eocene and Cretaceous 

 appears in two different forms. In the first, or Luxor type, the 

 shales containing a typical fauna of small gasteropoda, pelecypoda, 

 etc. presenting a Danian character, are separated by only a few metres 

 of a white chalk (weathering to a biscuit colour) from more massive 

 Eocene limestones containing large forms of Rhabdocidaris, Linihia, 

 and Lucina thebaica Zittel. 



In many localities these strata are characterized by the presence 

 of Opercidina libyca Schwager, which sometimes forms almost 

 the entire mass of the limestone. In such places the nature of the 

 transition is not very evident, and the marked palaeontological 

 hiatus is not accompanied by very sharp lithological differentiation. 

 In the limestone-plateau north-west of Qena the conditions are 

 remarkably different. There, at the base of the cliff facing Wadi 

 Qena on the west, are a series of fine-grained, well-stratified, chalky 

 limestones containing Perten farafrensis Zitt., Ostrea vesicularis 

 Goldf., Terebratulina sp. C?), 1 and other typical Danian fossils. 

 These pass, so far as can be judged, into limestones of precisely similar 

 lithological character, yet revealing no trace of fossils ; their 

 honeycombing, close-set stratification, and jointing give them the 

 appearance of having been formed under intense current-action 

 rather than of having been deposited in the waters of a quiet sea. 

 These strata are of great thickness, over 100 metres (300 to 400 feet 

 thick), and the typical Nummulites of the Eocene only appear where 

 more massive limestones overlie these softer beds. 



On the north the differences become further emphasized, there 

 being marked unconformity between the Eocene and the Cretaceous 

 strata where these are in contact. A notable and familiar instance 

 is the unconformable junction of the Middle Eocene beds with 

 the Cretaceous at Abu Roash, near the Pyramids, described by 

 Mr. Beadnell. 2 Here the Oarolia Beds of the Upper Moqattam 

 division ot the Middle Eocene rest on the Danian limestones to the 

 west ; while near the Pyramids the Lower Moqattam (Nummulites- 

 gizehensis) Beds occupy this position, suggesting overlap on a 



1 The Terebratulina needs further study. 



2 H. J. L. Beadnell, ' The Cretaceous Region of Abu Roash' 1902, Egypt. 

 Geol. Surv. Report (1900) pp. 14-17 & pis. vii-viii. 



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