STRATIGRAPHICAL GEOLOGY 
241 
STRATIGRAPHICAL GEOLOGY 
Scope of Cretacic Sedimentation in Andean Geosyncline. A 
recent preliminary contribution to the Cretacic paleontology of 
the Andean geosyncline by Fritzsche ^ lists ten localities, extending 
from Yaco, Bolivia, to northwestern Argentina, where fossils have 
been found in the so-called Puca Sandstone of Steinmann. 
These collections are especially interesting since a number of 
them contain assemblages indicative of brackish and fresh-water 
conditions. A similar brackish and fresh-water fauna was ob¬ 
tained by Singewald and Berry at the Finca El Molino, in the 
valley of the Rio Tarapaya, about nine miles northwest of Potosi, 
and 5 miles southwest of Miraflores, where the same Cretacic 
beds also contain marine fossils. 
The El Molino fauna comprising myriads of small Cyrenas and 
Ostracod tests, and a sparing representation of Melanoides, Cer- 
ithium, and Planorbis occurs in thin limestone beds intercalated 
in the gypsiferous red-beds so typical of the Puca Sandstone. 
Fritzsche’s comparisons are with European Early Cretacic brack¬ 
ish faunas, especially forms described by Dunker from German 
lagoonal deposits of that age; and he concludes that the age of 
the South American beds is Barremian, and that they are to be 
correlated with the coal-bearing Cretacic beds of Peru. That the 
Puca Sandstone is not Early Cretacic in age or the same age as 
the Peruvian coals is the reason for publishing the present note. 
In the first place the nature of the material does not warrant 
the placing of much reliance on either real or fancied resemblance 
to European fresh- or brackish-water forms, which are in general 
notoriously unreliable. In the second place some of the forms 
such as Hadraxon and Melanoides are scarcely normal in Early 
Cretacic assemblages. In the third place, at the locality near 
1 Centrallblatt f. Min., Geol. & Pal., 1921, No. 9, pp. 272-277, 1921. 
