62 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFERA 



The G. gansseri Zone characterizes the Middle Sharawna marl member as well as 

 the lower part of the Upper Sharawna shale member, and coincides with the Pecten 

 (Chlamys) mayereymari Sub-zone of the macro-fossil classification. Both its 

 planktonic foraminiferal and macrofossil content suggest a Middle Maestrichtian age 

 as indicated above (see pp. 47-49). 



5. The Globotruncana esnehensis Zone. 



This represents the third planktonic foraminiferal zone from the base of the 

 succession upwards, and characterizes the topmost part of the Cretaceous rocks in the 

 Esna-Idfu region. It is distinguished by the flood of Globotruncana esnehensis 

 Nakkady & Osman which is taken as the index fossil of the zone. Its upper part is 

 marked by a distinct break and by a well developed conglomerate which separates 

 it from the overlying basal Tertiary. At this break the genera Globotruncana, 

 Rugoglobigerina, Abathomphalus, Trinitella, Hedbergella, Globigerinelloides, Heter- 

 helix and Pseudotextularia ; all ammonites and mosasaurs, as well as a great number of 

 characteristic Upper Cretaceous species belonging to other groups, disappear 

 completely and abruptly. 



The lower limit of the G. esnehensis Zone is marked by the flood of Globotruncana 

 esnehensis and by a great reduction in the number of individuals of the G. gansseri 

 Zone which all die out completely in its lower part, except G. gansseri gandolfii 

 which continues to the disconformity. The lower limit of this zone is also marked 

 by the disappearance of G. area, G. bahijae, G, conica, and G. sp. and by the first 

 appearance of R. rotundata. 



The G. esnehensis Zone is generally characterized by the presence of Globotruncana 

 aegyptiaca aegyptiaca, G. aegyptiaca duwi, G. arabica, G. contusa contusa, G. contusa 

 patelliformis, G. cf. convexa, G. gagnebini, G. mariei, G. stuarti parva, G. subcircumno- 

 difer, G. havanensis, Abathomphalus intermedia, A. mayaroensis, Hedbergella mon- 

 mouthensis, H. petaloidea, Rugoglobigerina glaessneri, R. loetterli, R. pustulata, R. 

 macrocephala, R. pennyi, R. rotundata and R. rugosa, as well as the rare occurrence 

 oiG.fareedi, members of the G. gansseri group, G. leupoldi, G. lugeoni, G. orientalis, 

 G. sharawnaensis, G. youssefi, and H. hessi hessi at its base. 



The G. esnehensis Zone is equivalent in part to the Abathomphalus mayaroensis 

 Zone which is considered in various parts of the world to represent the uppermost 

 Cretaceous, and is equated with the established uppermost Maestrichtian Belemni- 

 tella casimirovensis Zone. However, although Abathomphalus mayaroensis was 

 recorded in the G. esnehensis Zone, the latter zone could not be named after it, in 

 spite of the advantage of this name in inter-regional correlation, as A. mayaroensis 

 was only recorded as a rare form, while G. esnehensis was found to flood this part of 

 the succession, wherever examined. 



6. The Globorotalia compressa/Globigerina daubjergensis Zone. 



This represents the fourth planktonic foraminiferal zone from the base of the 

 succession upwards. It characterizes the lower part of the Lower Owaina shale mem- 



