406 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1908. 



sion when at that stage. The most definite of these comments is, 

 that in the direction of Piicara (to the northwest) the lake reached 

 to Sta. Rosa. He also remarked that Tiahuauaco, which is a ruin 

 of a temple older than the Inca civilization, is 75 feet above the 

 present level of the lake. From this we may judge that since the 

 Indo-humanic period, as recorded by the oldest monuments in the 

 region, the lake has not fallen more than 75 feet. 



In journeying to the departments of Huaucavelica and Ayacucho, 

 Crosnier passed through the valley of Jauja, where he found a for- 

 mation which he considered (1852) to have been formed in an inter- 

 Andean lake about 30 miles long and from 9 to 12 miles wide. The 

 deposits are described as consisting of clays and gravels such as 

 would have been transported by streams. He estimated the thickness 

 at from 600 to 700 feet (200 to 300 meters) . In the basin of Ayacucho 

 he also found a Tertiary deposit consisting of marls and tuffs. No 

 proof as to the age of these beds was given, but they were classed as 

 Tertiary from their general relations. 



In his bulletin on the Mineral Resources of the Provinces of Jauja 

 and Huancayo,** Dueiias (1906) says that the valley of Jauja was in 

 former times the bottom of a great lake, which, by cutting the canyon 

 which is its natural outlet, has gone dry. The lake deposits he con- 

 sidered to be of glaco-fluvial origin. He published two photographs 

 of river terraces cut in these deposits. Dueiias does not refer to the 

 description of the lacustrine formation by Crosnier, with which he 

 no doubt was familiar. The action of glaciers in connection with 

 fluvial action brings in a new factor to explain the origin of the beds. 

 The author has seen a portion of the Jauja Valley, and is inclined 

 to doubt that glaciers contributed directly to form the deposits, al- 

 though products of glacial action were undoubtedly brought in by 

 rivers. If, however, lake beds were all deposited during the glacial 

 period we must refer them to the Pleistocene of the Quaternary and 

 not to the Tertiary, as was done by Crosnier. This is a matter for 

 further study. 



To the northwest of the Titicaca Basin, Dueiias (1907) observed 

 certain deposits in the Department of Cuzco,'' which he says are prob- 

 ably of lacustrine origin. They occur at several localities, differing 

 considerably in character. He mentions beds of tuffs and a stratum 

 of tripoli, in which he reported finding sponge spicules. Because of 

 finding these spicules he says that one might be induced to suppose 

 that in Tertiary times southern Peru was under the Pacific Ocean. 

 This is an unfortunate remark, since it is liable to be perpetuated in 

 the literature by being quoted without questioning whether spicules 



°' Bol. del Cnerpo de Ing. de Minas No. 35. 



^Aspecto Minero del Departmento del Cuzco, Bol. del Cuerpo de Ing. de 

 Minas del Peru No. 53. Enrique I. Duenas, 1907. 



