SOUTH AMERICAN GEOLOGY 
207 
ing to W. Kilian) of the Graham Land ammonite faunas, and the 
equally overwhelming affinities of the Peruvian faunas with the 
Late Cretacic faunas of northwestern Africa. We owe much of 
our knowledge of the Andean Cretacic faunas to Steinmann and 
his students, but much caution is necessary in viewing their re¬ 
sults, which have an air of precision and finality which they are 
far from possessing. The sediments are largely dear-water, mas¬ 
sive limestones, with the fossils preserved mostly as casts, hence 
errors of identification are easily possible. From a single outcrop 
and horizon in Peru I obtained a fauna of which out of its tweny- 
two previously known forms five had been recorded from sup¬ 
posed Aptian, six from supposed Albian, six from supposed 
Cenomanian, and nine from supposed Emscherian. This does not 
mean corresponding ranges of the species, but previous errors in 
the identification of species and in the age determinations of the 
strata. 
All of the standard Late Cretacic stages from Cenomanian to 
Santonian have been recorded from the Andes, but the time has 
not yet arrived for attempting a detailed history of the Cretacic 
succession in this region. Some time during Late Cretacic times 
gypsiferous red beds were deposited along a wide belt extending 
from north of Lake Titicaca to northwestern Argentina. These 
red beds contain thin limestone intercalations and fresh- and brack¬ 
ish-water fossils and constitute what Steinmann has called the 
Puca standstone. Fritzsche correlates these red beds with the 
littoral and continental Early Cretacic (?) section of Peru, as¬ 
signing a Barremian age to them because of the resemblance of 
some of the fresh-water and brackish mollusks to forms described 
by Bunker from the Wealden of Germany. At one locality in 
Bolivia I collected a few marine fossils from these red beds, and 
I have specimens collected by others from two additional locali¬ 
ties, which show conclusively that these beds are not of Early 
Cretacic age, but of the same age as the most extensive Late Cre¬ 
tacic fauna of Peru. The exact age of this maximum extent of 
the Late Cretacic sedimentation is uncertain, but it is not older 
than Cenomanian, nor younger than Emscherian. The Puca 
sandstone, therefore, represents shoreward deposits for a distance 
of 500 to 600 miles along the eastern margin of the central part 
7 Centralb. f. Min. Geol. & Pal., No. 9, pp. 272-277, 1921. 
