ORIGIN OF THE ANDES 
21 
with the Ouralian stage of Europe, with a subsequent emergence 
lasting through the Permian and Triassic times. There is a north¬ 
ward extension of the Permian tillites of Argentina into Bolivia 
in the Santa Cruz region. In Late Triassic (Noric) times a 
marine invasion may have reached Peru and Colombia from the 
Upper Amazon region and there are some continental Rhaetic 
deposits in Chile. 
Then followed a Jurassic submergence of unknown limits but 
general throughout the Western Range region. According to J. A. 
Douglas this was followed by post-Jurassic uplift and batho- 
lithic intrusion. The latter is probably of a still later age, and 
it is questioned whether there was really any great amount of up¬ 
lift. That there was shallowing in many areas is shown by the 
littoral character of the latest Jurassic beds and the widespread 
Early Cretacic coals of Peru. I believe that there was much 
minor oscillation of the strand throughout Cretacic times, but the 
details are still obscure. Traces of coal-beds, or shallow marine 
faunas, occur in the Andes from the Caribbean Sea to Cape Horn. 
They are especially prominent in the Western Range throughout 
its whole extent; and are known on the Altaplanicie and in the 
Eastern Range of Bolivia, and they are probably present elsewhere. 
The Andean region evidently has been a land area, throughout 
most of its extent, at least, even since the Late Cretacic times, but 
that the major folding of the post-Cretacic strata was not con¬ 
temporaneous with the major uplift that formed the present Andes 
is indicated by such facts as the following: The Miocene dora, 
found in the Tumbez-Payta region of coastal Peru, is identical 
with that of the Amazon basin so that there could have been no 
mountain barrier at that time sufficient to differentiate these two 
districts, or the fossil flora of the same age found to the west of 
the present Western Andes in the Concepcion-Arauco district of 
Chile. At the present time, in northern Peru, the upper limit of 
the tropical zone is at 4500 feet and, according to local topographic 
conditions, it sometimes reaches an altitude of 6,000 feet. From 
this it seems that until after early Miocene times there were no 
mountains in that region with a divide as high as 6,000 feet. 
Moreover, in the Eocene epoch there were marine transgressions 
from both the Atlantic (San Jorge formation of Argentina) and 
11 Quart. Jour. Geol, Stoc. London, Vol lyXXVI, No. 301, 1920. 
