422 
GLACIAL GEOLOGY 
in a belt extending for several degrees in the Pre-Cordillera 
in the provinces of ^Mendoza and San Juan. In the latter region 
the section is much more complete than farther to the eastward 
and the Permian tillites rest dicordantly on the Carbonic or 
older rocks. More recently similar deposits have been discovered 
in the Pampean Sierras. 
Many stratigraphic and other details, as well as paleogeographic 
speculations, are given by Keidel, although of course much remains 
to be learned, and the contiguous areas both to the north and 
south are little known. The general sequence of the Permian 
and succeeding deposits in the Pre-Cordillera may be illustrated 
by the section exposed in the La Rioja region, which is as follows: 
I Lias (marine). 
I Unconformity 
f Rhaetic (continental). 
J Unconformity 
] Early Triassic (continental),. 
[ Unconformity 
[ Catuna formation 
I Unconformity 
] Jejenes formation 
(Umango Series) ( Zonda formation 
[ Tontal formation, (glacial). 
The accompanying sketch-map shows the general position of 
these deposits as they are at present known. It may be predicted 
with a good deal of assurance that subsequent exploration in the 
sub-Andean zone will show that the continental Permian extends 
southward in that region into Patagonia, and northward as far 
at least as south-central Bolivia. 
Edward W. Berry 
Climatic Index of Bonneville Lake Beds. Because of the fact 
that they have been thought to furnish undoubtable stratigraphic 
testimony in support of the conception of the duality of the 
Glacial Epoch the lacustral deposits of the Great Salt Lake Basin 
of Utah hold an especial interest. Where best exposed these 
beds occupy a vertical space of about 100 feet; but their total 
thickness is without question considerably greater than this figure. 
The main body of the formation comprises fine, laminated, cal- 
JURASSIC 
Triassic 
Permian 
