32 1'1'PER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



with the overlying G. wilcoxensis Zone which is here taken to mark the base of the 

 Eocene. Moreover, as mentioned above, the planktonic Foraminifera of the G. 

 velascoensis zone constitute, with those of the underlying Paleocene zones, a contin- 

 uous evolutionary series which unites them as one natural unit. On the other hand, 

 the disappearance of several typical Paleocene forms at the base of the G. wilcoxensis 

 Zone and the appearance of new forms and new evolutionary tendencies, clearly 

 distinguishes this zone from the underlying Paleocene. In the G. wilcoxensis 

 Zone, a tendency towards reduction in the size of test and increase in the surface 

 rugosity and/or the degree of development of the marginal keel in the genus Globoro- 

 talia, is clearly documented. As a result the majority of the planktonic Fora- 

 minifera in this basal Eocene zone have a highly rugose surface and/or a very well 

 developed marginal keel. In this connection, it is worth noting that the rare 

 planktonic forms recorded by Kaasschieter (1961) from the type Ypresian of Belgium, 

 although misidentified, are highly rugose, as are all the forms recorded by Berggren 

 (1960a) from the Ypresian of Denmark and northwestern Germany. Moreover, the 

 planktonic Foraminifera of the G. wilcoxensis Zone clearly correlate it with the basal 

 Eocene of Mexico, the Gulf and Atlantic Coastal Plains of the U.S.A., the Carib- 

 bean region, Denmark, northwestern Germany, southern France, Italy, North Africa, 

 the Middle East, Pakistan-India-Burma region, New Zealand and the U.S.S.R., 

 where similar planktonic foraminiferal assemblages have been recorded. This is 

 substantiated by the fact that in the sections studied, a flood of Nummulites, Oper- 

 culina, Assilina and Discocyclina, amongst numerous typical Eocene forms, is 

 clearly observed in the G. wilcoxensis Zone, while the genus Nummulites, represented 

 by rare specimens of the very primitive form N. deserti de La Harpe, is alone recorded 

 in the uppermost part of the underlying zone. However, a detailed study of the 

 planktonic Foraminifera in the type Lower Eocene is needed before a definite 

 decision on the position of the Palecoene/Lower Eocene boundary can be reached. 



B. The Upper Cretaceous-Lower Tertiary in Egypt 



The classification of the Upper Cretaceous-Lower Tertiary rocks of Egypt was 

 first attempted by Zittel (1883), who considered the fossiliferous marine succession 

 overlying the Nubia sandstone of the Western Desert Oases to belong collectively to 

 the Danian, which he regarded as the youngest stage of the Cretaceous system. As 

 a result, he assigned the underlying unfossiliferous Nubia sandstone to the Upper 

 Senonian, while he considered the nummulitic limestone beds which cap the succes- 

 sion to be of Lower Libyan (Lower Eocene) age. However, he overlooked the 

 succession of shales between the top of his Danian and the base of the nummulitic 

 limestone, which were later recorded by various authors in the Oases and in other 

 parts of Egypt, and were considered by Beadnell (1905) as passage beds between the 

 Cretaceous and the Tertiary systems. Moreover, Zittel advocated the absolute 

 conformity of the Cretaceous-Tertiary succession in southern Egypt, a concept 

 which, as discussed below, was uncritically followed by most stratigraphers and led 

 to great confusion. 



Zittel classified the strata he considered to be Danian in the Western Desert Oases 



