196 
SOUTH AMERICAN GEOLOGY 
and eastern parts of the continent, and of a land-connection with 
Antarctica. Whether the whole interior of South America was a 
single, epicontinental sea, or was more or less broken up, we do 
not know. Certainly, if the present folds were smoothed out the 
Devonic sediments would cover a continuous area of great width, 
for to-day in its tightly folded state it outcrops over an area near¬ 
ly 400 miles in width in Bolivia. 
Structurally we see clearly at this time an Amazonian geosyn¬ 
cline, and an Eastern Andean syncline extending from Latitude 
10° South in Peru southward to the Falkland Islands. Neither 
in Bolivia nor in Argentina is there any evidence of a break be¬ 
tween the Siluric and the Devonic sections and the faunas of the 
latter contain numerous slightly modified holdovers from the form¬ 
er. In Bolivia the sedimentary succession is as follows: 
Upper unfossiliferous sandstones. 
Huamampampa sandstones. 
Conularia beds. 
Fossiliferous sandstones. 
Unfossiliferous sandstones. 
Although all but the middle member are termed sandstones they 
are prevailingly shaly, and shale is the predominating lithologic 
type encountered in crossing the ranges. This succession prob¬ 
ably represents a single cycle of invasion and retreat of the sea, 
with always a near-at-hand source for the almost exclusively ter¬ 
rigenous sediments. In Matto Grosso, Brazil, the chief fossilifer¬ 
ous rock is a hematite, believed to be an altered limestone, which 
may account for the more varied fauna in that area. With the 
exception of the faunas described from northern Brazil (Erere), 
which some authorities regard as indicating Hamilton affinities, 
all of the South American Devonic rocks are, in a boreal sense. 
Early Devonic in age, that is corresponding roughly with the Held- 
erberg-Oriskany-Onondaga strata of eastern North America, and 
with the retreat of the Early Devonic epicontinental sea, early in 
Mid Devonic time, all of South America became dry land, and 
remained so for a very long time, since there are no known marine 
deposits of Late Devonic, Mississippian or early Pennslyvanian 
date anywhere in the southern continent. 
South American geological history is, then, a blank, in so far as 
marine history is concerned, from early Mid Devonic to Mid Car¬ 
bonic times. Continental deposits, with plant fossils which I 
