HASEMAN, GEOGRAPHICAL DISTRIBUTION IN SOUTH AMERICA 31 



of the Cordillera Oriental of Ecuador or in the southern parts of either 

 Colomhia or Venezuela, i. e., as far south as the headwater of Bio Negro 

 in the Brazil-Guiana highlands. This vaguely indicates a connection be- 

 tween these Archean mountains of eastern Colombia (Cordillera Ori- 

 ental) and the Piano Alto, but inasmuch as this region is practically 

 unknown, too much emphasis must not be placed on such data. 



There is then no positive evidence for either a northern or an eastern 

 extension of the East Andean Sea, but there is some positive evidence for 

 its southern extension. The location of the marine formations, the dip of 

 the surface of the Piano Alto and the character of the sediment carried 

 by southern Andean affluents of the Amazon vaguely indicate the same. 

 The southern extension of Cretaceous deposits from the headwaters of 

 Eio Maranhao south toward Cochabamba is a good example of the south- 

 ern extension of part of this East Andean Sea which finally lost its con- 

 nection with the ocean on account of the Tertiary rise of the Andes. 



In reference to the connection of this East Andean Sea with the ocean, 

 the following points are important : 



1. Stelzner (1873) reported a sandstone containing marine bivalves 

 of ( ?) Tertiary age from Santa Maria, Catamarca of northern Argentina. 



2. Brackenbush has reported marine or brackish water fossils of (?) 

 Cretaceous near the headwaters of Bio Bermejo which flows into the Gran 

 Chaco del Argentina. Melania was the most abundant form found, and 

 it may be that these deposits are fresh water and not marine. 



3. Far to the west of the above regions, there is a great depression in 

 the Andean complex east of the bay of Arica and south of Lake Titicaca, 

 but so far there is no good evidence of a Tertiary sea passing over the top 

 of the Andean complex. 



4. It appears to be obvious from the characteristic fossils of the upper 

 Amazon Valley that a direct and broad connection with the ocean did not 

 exist. If, as the Cretaceous fossils of the Alto Eio Maranhao indicate, the 

 East Andean Sea existed during at least part of the Mesozoic to some 

 time in the middle or late Tertiary, there would have been ample time to 

 evolve this peculiar fauna of Pebas, because the conditions which would 

 have existed in this long, slender inland sea, into which many short rivers 

 carrying sediment flowed, would have been very different from those of 

 Patagonia, la Plata or along the Pacific slope. 



It appears that the fossils of Alto Eio Amazonas are the last of the 

 fauna of the East Andean Sea which became buried in the mud carried 

 by the rivers into this vanishing sea, because the molluscs died with their 

 valves closed and because there are some fresh-water and land molluscs 

 mixed with the marine forms. 



