42 ME. J. A. D0I7GLAS OX GEOLOGICAL SECTIONS [April 1914, 



Such a rise of water-level, amounting to over 100 feet, would 

 cause an enormous extension of the lake ; and, if we judge from 

 details of topography, this would have been greatest hi a north- and- 

 south direction. If, then, this extension can be proved to have 

 existed in such comparatively modern times, it is easy to picture an 

 earlier state involving the total submergence of the country now 

 drained by the Desaguadero. 



The presence of a marine fauna in the waters of Lake Titicaea, 

 first discovered by Alexander Agassiz in 1878, has been held by 

 many geologists to furnish strong proof of the elevation of the 

 Andes in recent times. The lake is regarded as having originally 

 been formed by an arm of the sea, which was cut off and raised 

 during the elevation of the Cordillera to its present altitude of over 

 12,500 feet above sea-level. To attempt to solve this question 

 without an extensive biological knowledge of the means by which 

 such organisms are distributed would be entirely out of place here, 

 but since many complications have been introduced by the writings 

 of local investigators, I cannot refrain from passing a brief criticism 

 on one of the most extravagant of these recent theories — that of 

 Lorenzo Sundt. This author considers that the country has under- 

 gone the following changes of level since Cretaceous times : — 



Early Tertiary, (1) a rise from the sea, accompanied by great lateral pressure 



and folding-. , 



Late Tertiary, (2) a depression of 6500 feet. 



(3) a further rise accompanied by folding. 

 Post-Tertiary, (4) a depression below sea-level, with the formation of the 

 gravels of the TJlloma district. 

 (5) a final uplift of 13,500 feet, without lateral pressure or 

 folding. 



Such a theory seems to me to be utterly untenable. 



A wide transgression in Cretaceous times over a large part of the 

 Andes is a recognized fact ; but, so far as I am aware, there is no 

 record of any marine Tertiary deposit anywhere in the Cordillera 

 at a greater altitude than 3000 feet. The extensive horizontal 

 sheets of volcanic ash, etc., of the Mauri Volcanic Series have been 

 shown in the foregoing pages to be of Miocene or Pliocene age, and 

 to contain traces of a terrestrial fauna and flora ; and it is hardly 

 possible to suppose that they have been twice depressed below 

 sea-level, and re-elevated to 13.000 feet, without disturbance of their 

 horizontality. Further, the high-level terrace of Ulloma contains 

 abundant proof of a Pleistocene mammalian fauna, and it is quite 

 inconceivable how Sundt can regard this deposit as of marine 

 origin. 



Proof of recent elevation has also been deduced from the position 

 of Tiahuanacu. It has been urged that the present cold and 

 barren site, at an altitude where corn cannot ripen, would never 

 have been selected as a suitable locality for the support of a thriving- 

 population, and that therefore at the time of its existence the 

 country must have stood at a considerably lower altitude. 



