IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 17 



chalk " and the " phosphatic chalk of Ciply ", in Belgium to be of Maestrichtian 

 age. To justify this, he subdivided the Upper Campanian Hoplitoplacenticeras vari 

 Zone of de Grossouvre into a lower zone with Hoplitoplacenticeras vari which he 

 considered to be of Upper Campanian age, and an upper zone with Bostrychoceras 

 polyplocum which he attached to the Maestrichtian. Therefore, he considered the 

 Maestrichtian (in his sense) as comprising two ammonite zones, an upper with 

 Pachydiscus neubergicus ( =Maestrichtian) and a lower with Bostrychoceras poly- 

 plocum (=uppermost Campanian), although the latter species has never been 

 recorded in the type Maestrichtian or in its junior synonym, the Dordonian. 



This downward extension of the Maestrichtian as suggested by Haug was followed 

 by Spath (1926), Laffitte (1934. J 939)> Marie ( I 937. I 943)> Gignoux (1943, 1950), 

 Muller & Schenck (1943) and Mikhailov (1947, 1948) as well as many other authors, 

 and has confused the position of the Campanian-Maestrichtian boundary. 



On the other hand, Cornet & Briart (1874), followed by Umbgrove (1925, 1926), 

 Withers (1935), Bubnoff (1935), Van der Heide (1954), etc. restricted the Maestrich- 

 tian stage to the Maestricht tuff and its equivalents only, but this did not solve the 

 problem of the Campanian-Maestrichtian boundary. To overcome this difficulty, 

 Leriche (1927, 1929), quite justifiably, included in the Maestrichtian, all Upper 

 Cretaceous strata in the type area of Dumont, which are older than the Danian of 

 Desor (1846) and younger than the Senonian of d'Orbigny (1842) and the Campanian 

 of Coquand (1857). This concept, which clearly signifies that no equivalents of the 

 Maestrichtian occur in the type Senonian of d'Orbigny, created a tendency among 

 various authors to regard the Maestrichtian separately from the Senonian. This has 

 been substantiated by the fact that Schijfsma (1946) considered the Foraminifera of 

 the Belemnitella mucronata chalk of the Paris Basin, which represents the upper part 

 of d'Orbigny's Senonian, to be of Middle and Upper Campanian age, and thus he 

 denied the presence of Maestrichtian in the Paris Basin, although Marie (1943) 

 considered the Meudon Chalk to be of Maestrichtian age. 



Visser (1951) studied the Foraminifera of the type " Maestricht tuffaceous chalk ", 

 reviewing previous studies and discussing the various usages of the term Maestricht- 

 ian. She mentioned that while Gignoux (1936-1950), followed by most French 

 stratigraphers, had equated the Maestrichtian with the Belemnitella mucronata Zone, 

 Muller & Schenck (1943) equated it with the B. lanceolata Zone, restricting the 

 mucronata Zone to the Campanian, and Brotzen (1936) considered the mucronata 

 Zone to be younger than the Maestrichtian. On the other hand Schijfsma (1946) 

 considered the B. mucronata Zone to represent both the Upper Campanian and the 

 Maestrichtian, while he considered the Middle Campanian to be represented by a 

 particular horizon in which both B. mucronata and Goniatheutis quadrata occur, and 

 the Lower Campanian to be represented by the G. quadrata Zone only. She also 

 mentioned that while in Belgium and Holland the term Maestrichtian s.s. is generally 

 used to describe both the Maestricht tuffaceous chalk and the Kunrade chalk, the 

 term Maestrichtian s.l. (or the Maestrichtian as understood by French authors) 

 includes the underlying Gulpen chalk as well. Following Schijfsma (1946), she 



