322 A. P. COLEMAN 
conformably, a hundred meters or more of sandstone with a west- 
ward dip. 
The two types of deposit just described are as different as pos- 
sible, though both seem to be glacial, but I was unable to determine 
how they are related to one another, since there has been folding, 
faulting, and squeezing during the formation of the mountain 
range, rendering the relationships complicated. 
Before leaving Buenos Aires, Dr. Keidel had referred to two 
tillites, a lower and an upper, corresponding probably to the two 
deposits just described. He mentioned also that near the lower 
tillite Talchir plants had been found, and some distance farther 
south Kharbari plants, giving-a clue to the age of the deposits. He 
has also found tillite to the north of San Juan, reaching in one place 
latitude 28°, and has discovered a striated surface of Devonian 
limestone beneath the tillite. Specimens of the tillite and of the 
glaciated surface are to be seen in the Museum of the Survey on 
Calle Maypu in Buenos Aires. His account of the very interesting 
glacial deposits in the western foothills of the Andes must be 
awaited for details as to their general features and relationships, but 
I am able to confirm his statements as to the glacial character of 
the beds so far as seen by myself. 
CONCLUSIONS 
From the descriptions given it will be seen that there are three 
widely separated regions of known Permo-Carboniferous glaciation 
in South America, the deposits differing much in appearance and 
lithological character, but all showing plainly the effects of ice 
action. The Brazilian tillites are the most widely distributed and 
the least changed. ‘They occur along the dissected edge of a table- 
land rising several hundred meters above sea-level and dip gently 
inland beneath sandstones and trap-sheets of the early Mesozoic. 
One or two diamond-drill cores prove that the tillite extends for 
50 kilometers or more beneath the Triassic beds, but how much 
farther they go in that direction is unknown. There can be no 
doubt that they once reached farther seaward, so that the original 
ice-covered area must have been much greater than the present 
known area of tillite. As marine fossils have been found by 
Oliviera interbedded with the tillite on the Rio Negro in the state 
