22 upper cretaceous-lower tertiary for aminifer a 



Nature of the Mesozoic-Cainozoic Boundary 



The traditional usage of the Danian as the youngest stage of the Cretaceous 

 system instead of its true position at the base of the Tertiary, has always concealed 

 the nature of the Mesozoic-Cainozoic boundary which in most parts of the world is 

 marked by a distinct stratigraphcial break. 



In addition to the indisputable, major faunal break between the Maestrichtian 

 and the overlying Danian, the latter was found, in various parts of the world, to be 

 separated from the Cretaceous rocks below by physical breaks of varying magnitude. 

 In places, where the Upper Cretaceous-Lower Tertiary succession was described to 

 be conformable throughout, (e.g. Egypt), unconformities and disconformities are 

 being discovered with further detailed examination of the previously described 

 sections (e.g. Farafra, Dakhla and Kharga Oases and the Esna-Idfu region). In 

 places where the lithology on either side of the contact does not permit the detection 

 of the physical break, the abrupt extinction of numerous, diverse representatives of 

 Cretaceous life, and the sudden appearance of new Tertiary forms, clearly mark the 

 Mesozoic-Cainozoic contact. 



Although evident and clearly documented, such a distinct, sharp and world-wide 

 break at the Maestrichtian-Danian boundary, represents one of the most enigmatic 

 problems in the history of the Earth. It is beyond the scope of the present work to 

 try to explain it, but it clearly points to the fact that the life record between the 

 uppermost Maestrichtian and the lowermost Danian, as we know it, is incomplete 

 and may possibly be sought for in the deep oceanic troughs, or in yet undescribed 

 sections, where a complete Cretaceous-Tertiary sequence may be found. Moreover 

 it reflects, as previously mentioned by Jeletzky (1962) " some kind of a radical, 

 world-wide change in the physical regime of our planet ", which may be regarded as a 

 " catastrophe " or a " revolution ", and which still awaits further explanation. 



Stratigraphical Position and Classification of the Paleocene 



Schimper (1874) introduced the term Paleocene to distinguish the lowest part of 

 the Tertiary system, which was then included at the base of the Eocene. He used 

 this term to describe the " Travertin de Sezanne " in the eastern part of the Paris 

 Basin, which he considered on the basis of its floral content to be worthy of distinc- 

 tion from both the younger Eocene and the older Upper Cretaceous series. The 

 conglomerates of " Meudon " and " Cernay " which are characterized by their 

 mammalian fauna were also attached to the Paleocene and were found to mark the 

 limits of a sedimentary cycle which followed the Cretaceous chalk and preceded the 

 " Nummulitic transgression ". 



Thus the Paleocene was generally considered to represent one sedimentary cycle 

 spanning the time between the uppermost Cretaceous and the basal Eocene, although 

 the controversy about the true position of these two boundaries made it difficult to 

 establish the boundaries of the Paleocene series. For example, the so called " piso- 

 litic limestone " of Laversines and Vigny and its equivalents, in the Paris Basin 



