Boundary in South America. 3 



Laurentia, where recent results indicate a clear separa- 

 tion of Cretaceous and Tertiary sediments and their 

 faunas, both in California to the westward of the Sierra 

 Nevada and Cascade-Range, as well as in the region of 

 the Atlantic and Gulf Coastal Plain. But in carrying 

 on this study in the interior provinces of the ancient 

 continental masses, along the borders of the epiconti- 

 nental Laramie-Sea or in the region of the Patagonian 

 mesetas, extraordinary difficulties are met with on 

 account of the participation of terrestrial faunas. The 

 abundance of facies, the changing and interwedging of 

 terrestrial, lacustrine, brackish, littoral and marine 

 sediments, the migrations of animals and plants, the 

 movements of faunas and floras, afford a spectacle of 

 kaleidoscopic variety. Thus, this period may be charac- 

 terized as a phase of transformations and alterations, of 

 destruction of the past and preparing of a new order of 

 organic and inorganic life. The very complicated prob- 

 lem of correlating the manifold interior formations with 

 the marginal events and the general geological time table, 

 could not be displayed better than by the symposium of 

 the Geological Society of America. 



In South America, Steinmann was the first to point 

 out the existence of an hiatus between Cretaceous and 

 Tertiary sediments. In Chile he determined the Senom 

 ian age of the ammonite and baculite-bearing beds of 

 the Quiriquina Isle, and proved the strata of the Navidad 

 Beds (Piso de Navidad) to be the most ancient marine 

 deposits of that country (Upper Oligocene or Miocene). 5 

 Between these two groups of marine sediments a wide 

 hiatus corresponds to a long continental period with 

 heavy denudation. Recently Briiggen, with special refer- 

 ence to the fauna of Algarrobo (near Valparaiso), has 

 dispelled the last doubts about the existence of this 

 unconformity. 6 



In Patagonia the interpretation of the analogous 

 phenomena is also beset by many difficulties, and both the 

 stratigraphic and paleontologic research require revision. 



In the southern part of Patagonia, Steinmann 7 in 1883 



5 Steinmann, Deeeke und Morieke, Das Alter und die Fauna der Quiri- 

 quina-Schichten in Chile, N. Jahrb. Min., Beil.-Bd., 10, 1896. — Morieke und 

 Steinmann, Die Tertiarbildungen des nordlichen Chile und ihre Fauna, ibid., 

 Beil.-Bd., 10, 1896. 



6 El Cretaceo del Algarrobo i las supuestas relaciones entre las f ormaeiones 

 cretacea i terciaria de Chile. Santiago-Valparaiso, 1915. 



7 Beisenotizen aus Patagonien, N. Jahrb. Min., 2, 255, 1883. 



