Boundarxj in South America. 5 



Both 14 in 1896, and described for the first time by Burck- 

 hardt, 15 was supposed to be of Upper Cretaceous age and 

 was even placed in the Cenomanian by Ameghino. Roth 

 believed that this fauna had only a local character and 

 considered the corresponding sediments as marine inter- 

 calations in the "Areniscas Abigarradas," sandstones 

 of continental origin, representing in large parts of 

 Patagonia the negative phase of the Upper Cretaceous. 

 The mistaken assertion that ammonites were present in 

 these sediments (Ameghino) appeared for a long time 

 as another proof of a Cretaceous age. It is true that 

 Wilckens rightly perceived the connection of the Roca 

 Beds (Piso Rocanense, Rocaneano) of the Rio Negro 

 valley with the equivalent formations of Southern Pata- 

 gonia ( Salamanqueano, Sehueneano) and classified all 

 these formations under the general name of his "San 

 Jorge-Formation," but adhered, just as did v. Ihering, 

 to an Upper Cretaceous age of this fauna. 16 



On the basis of a series of observations in the field, the 

 author of this paper showed in 1912-14 that the sediments 

 of the Roca Beds must be regarded as deposits of a wide- 

 spread transgression covering the Upper Cretaceous 

 sandstones (Areniscas Abigarradas) over large areas of 

 Patagonia. 17 In the light of these new observations the 

 Roca Beds cannot be regarded as mere transitory inter- 

 calations in these sandstones, but are rather the witness 

 of the first transgression which, coming from the Atlantic 

 side, spread over the Patagonian Continent, remnant of 

 the older Brazilo-Ethiopian Continent of Mesozoic times. 

 In the sense of the theory of Haug, the folding of the 

 great Andine geosyncline at the western border of this 

 old continent was coordinated with the sinking and 

 breaking down of the corresponding continental area in 



"Apuntes sobre la geologia y paleontologia de los Territories del Eio 

 Negro y Neuquen, Eevista del Museo de La Plata, 9, pp. 141 etc., 1899. 



15 Le gisement supracretacique de Eoca, Eevista del Museo de La Plata, 

 10, pp. 207 etc., 1902. 



18 v. Ihering, however, partly admitted the possibility of correlating the 

 ■San Jorge with the lowest part of the Tertiary, and Wilckens in conversa- 

 tion during the last years was inclined to revise its earlier published views. 



17 A. Windhausen, El yacimiento de Eafaelita de Auea Mahuida, Informes 

 preliminares de la Direction Gral. de Minas etc., vol. 1, Buenos Aires 

 1912. — Contribution al conocimiento geologic© de los Territories del Eio 

 Negro y Neuquen etc., Anales del Ministerio de Agricultura, Section 

 Geologia etc., vol. 10, No. 1, Buenos Aires, 1914. — Einige Ergebnisse zweier 

 Eeisen in den Territorien Eio Negro und Neuquen, N. Jahrb. Min., Beil.-Bd., 

 38, 1914. 



