20 UPPER CRETACEOUS-LOWER TERTIARY FORAMINIFER A 



include the Maestrichtian rocks only. On the other hand Munier-Chalmas & de 

 Lapparant (1893) distinguished the Danian from the Maestrichtian, but extended 

 the former upwards in the section to include the Montian as its upper substage and 

 the typical Danian as its lower, including them both in the Cretaceous system. 

 Again, Geikie (1903) considered the Danian to include the Maestrichtian as its 

 lower part and the Montian as its upper, while Denizot (1936) considered the Mae- 

 strichtian to be distinct from the Danian, although he included it as a substage of the 

 latter. 



This arbitrary use of the term Danian, resulted in the fact that the literature is 

 now filled with a considerable amount of wrong and confused information which led 

 to the vagueness and ambiguity of the term, and made it difficult to decide its true 

 stratigraphical position. 



However, de Grossouvre (1897, 1901) considered both the Danian and the Montian 

 as a single unit in the basal Tertiary. He reasoned that as the Danian is devoid of 

 the index fossils which characterise the Cretaceous rocks below, such as the ammon- 

 ites, belemnites, inocerami, trigonias, rudists (Hippurites, Spherolites and Radio- 

 lites), etc., the Cretaceous-Tertiary boundary should be drawn at the base of the 

 Danian. Unfortunately, this valuable remark was received with little enthusiasm, 

 and most stratigraphers continued to use the term Danian in the sense of Desor 

 (1846) and d'Orbigny (1852), as the youngest stage of the Cretaceous system. 



Nevertheless, this logical explanation of the Cretaceous-Tertiary boundary 

 suggested by de Grossouvre, has started, since the early days of this century, to gain 

 the support of a few geologists, e.g. Brunnich-Nielsen (1920), Rosenkrantz (1920), 

 Harder (1922), Kayser (1924), Keller (1946), and Morozova (1939), who clearly 

 demonstrated the Tertiary affinities of the Danian fauna and thus advocated its 

 position at the base of the Tertiary. 



Although faced with strong opposition and neglect at that time, this proposition 

 has recently received overwhelming support by a great number of stratigraphers, 

 e.g. Jeletzky (1951-1962) Bronnimann (1953), Troelson (1957), Loeblich & Tappan 

 (1957a, b), Bolli (19576), Nakkady (1957), Bolli & Cita (1960a, b), Hay (i960), Lys 

 (i960), Reyment (1960a, 6) Burollet & Magnier (i960), Rosenkranz (i960) and 

 Berggren (19606, 1962). These recent studies have shown that the Danian, in its 

 type region and in various parts of the world is separated from the Maestrichtian 

 rocks below by a distinct faunal break which is generally accompanied by a physical 

 break of varying magnitude. The pronounced nature of this break and its world- 

 wide extent clearly mark the Maestrichtian-Danian boundary as the natural bound- 

 ary between the Mesozoic and the Cainozoic eras, and justifies the position of the 

 Danian at the base of the Tertiary system. At the Maestrichtian-Danian boundary, 

 all the Globotruncana, Rugoglobigerina, Trinitella, Plummerita, Abathomphalus, 

 Hedbergella, Globigerinelloides, Schackoina, Pseudotextularia, Pseudognembelina, 

 Gublerina, Planoglobulina, Racemiguembelina, and Heterohelix, among a large number 

 of microfossils ; all the ammonites, the true belemnites (Belemnitellidae), rudists, 



