406 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1908. 
sion when at that stage. The most definite of these comments is, 
that in the direction of Pucara (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. 
Tn his bulletin on the Mineral Resources of the Provinces of Jauja 
and Huancayo,* Duefas (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. Duefias 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, Duefias (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 1s lable to be perpetuated in 
the literature by being quoted without questioning whether spicules 
@ Bol. del Cuerpo de Ing. de Minas No. 35. 
b Aspecto Minero del Departmento del Cuzco, Bol. del Cuerpo de Ing. de 
Minas del Peru No. 53. Enrique I. Duenas, 1907. 
