336 F. H. KNOWLTON CRETACEOUS-TERTIARY BOUNDARY 



in drawing the line of separation between the Cretaceous and Tertiary in 

 America?" it is necessary to go back and determine at several critical 

 points what constitutes this standard. 



The Cretaceous and Tertiary systems were worked out in the Anglo- 

 Parisian basin. The type area of the Cretaceous — or Chalk, as it was 

 called until 1822, when d'Halloy introduced the term Cretaceous for it — 

 is in the London basin, and the Tertiary was first worked out near Paris. 

 Geikie says, concerning them, that both in France and in England "the 

 lithologic sequence, being the more obvious, was first established before 

 it was confirmed and extended by a recognition of the value of the evi- 

 dence of organic remains." This statement, that the systems were estab- 

 lished on a physical basis, is abundantly verified by the early writings. 

 As the systems were studied in other regions, conflict of opinions devel- 

 oped as to the position of the Danien and Montien beds, which seem to 

 contain a mixture of Cretaceous and Tertiary forms. Some of the Eu- 

 ropean geologists place these formations in the Cretaceous, others in the 

 Tertiary, while Dollo, Haug, and others assign the Danien to the Creta- 

 ceous and the Montien to the Tertiary. It is significant that, although 

 several fossils of Cretaceous type occur with those of Tertiary type in the 

 Montien, Haug reverts to the original criteria for determining the sepa- 

 ration between the two systems, aild places the Montien in the Tertiary 

 because it lies unconformably on the older rocks. 



In his summary of the Montien, Haug states that it contains, together 

 with Tertian* forms, several. survivors of the Cretaceous faunas, among 

 which are crocodiles, magalosaurs, and other dinosaurs. 



Two things mentioned above are especially significant: (1) The Cre- 

 ceous and Tertiary systems were originally established on a physical basis, 

 and the exact line of separation between them was determined by the 

 structure; (2) after more than a century, during which the several lines 

 of evidence have been tested, the last authoritative word on the European 

 standard is to the effect that the structure is the determining factor in 

 separating them, and that even dinosaurs, that have been appealed to so 

 often as proof of Cretaceous age, did not end with the Cretaceous. 



Probably all American geologists will agree as to the desirability of 

 conforming the American geologic time scale as closely as possible to the 

 European standard, and probably all who have thought sei'iously on the 

 subject will also agree that it is impracticable, perhaps impossible, to do 

 so in all cases. '^I do not hesitate to express the opinion," said the late 

 Dr. C; A. White,^ "that it [the European standard] is not of infallible 



sproc. Amer. Assoc. Adv. Sci., vol. 38, 1889, p. 225. 



