2 Windh a usen — The Cretaceous- Tertiary 



marize the stratigraphic and paleontologic evidence bear- 

 ing on this important question, as has been done in the 

 Bulletin of the Geological Society of America. 1 



The same difficulty in determining the general rela- 

 tions between the Cretaceous and Tertiary is encountered 

 in three remote localities of the great American Con- 

 tinent. In California, in Chile and in Patagonia there 

 has been said to exist a mixture of faunas at this critical 

 boundary ; but in all these localities there is obvious evi- 

 dence of unconformity and a stratigraphic and paleon- 

 tologic break closing Cretaceous time. On the other 

 hand, the stratigraphy of the marine sediments covering 

 the border of the Brazilian Shield over a large tract 

 between the mouth of the Amazon River and Sergipe, is 

 not yet entirely clear. The fauna of Pirabas (Para) 

 is said to contain both Cretaceous and Tertiary ele- 

 ments ; 2 but according to J. C. Branner the oil-bearing- 

 shales with diatoms and the freshwater-deposits in the 

 Bahia basin and more northward, may be considered as 

 of Eocene age. 3 In a similar way, Hill 4 described from 

 the Antilles sediments with Rudistce and Actceonella, 

 associated according to him with typical fossils of the 

 Eocene. In such cases, where marine Paleocene or 

 Eocene rests upon marine Cretaceous, it may be justifi- 

 able to infer the existence of a gradual transition from 

 Cretaceous to Tertiary. In the Eastern Sahara and in 

 Central Tunesia, where during this critical period the 

 sea always maintained a constant depth, marine Eocene 

 can be observed lying without hiatus upon marine Creta- 

 ceous ; but in this case the appearance of nummulites 

 may be considered as a conventional sign for the neces- 

 sity of stratigraphic division. 



In other cases, where the negative phase which fol- 

 lowed the close of the Senonian Epoch, or its equivalents, 

 was manifested by oscillatory movements, an obvious 

 break separates the Upper Cretaceous from Tertiary 

 sediments of marine character. The finest example illus- 

 trating this phenomenon is found on both borders of 



1 See volume 25, September, 1914. 



2 F. Katzer, Grundziige der Greologie des unteren Amazonasgebietes (des 

 Staates Para in Brasilien), pp. 132 etc., Leipzig, 1903. 



3 The oil-bearing shales of the coast of Brazil. A paper read before the 

 Am. Inst, of Mining Engineers, Canadian Meeting, August 1900, Author's 

 edition. 



4 The geology and physical geography of Jamaica, Bull. Mus. Comp. 

 Zool., Harvard College, vol. 34, 1899. 



