16 THE DESEADO FORMATION OF PATAGONIA 
designated as a Deseado exposure; and it has the same 
general appearance and color which is found in the green 
sands of the Deseado pocket on the Rio Chico. However 
it is conformable interbedded with the underlying and over- 
lying marine beds and I consider it a part of the marine 
series. Above it come more white sandy clays that are 
characteristic of the most of the section. 
Wilckens takes all of this series, from the base of the 
Salamanca, up to the unconformity below the Patagonian, 
and makes of it his St. George Period, a transgression 
epoch, lasting to the end of the Upper Cretaceous. I be- 
lieve it is all marine, and is all a part of the Upper Creta- 
ceous transgression of the sea over Patagonia. However 
the Salamanca is a clear cut deposit and I feel it should 
be retained as a distinct horizon. The overlying light 
colored (white, grey, brown, yellow, or green) sandy clay 
shales represent a deeper water and later facies, which is 
characteristically developed on the Gulf of St. George, 
and may well be distinguished as the St. George epoch or 
series, but I should use the term only in this more limited 
way. It is the same series which Ameghino has plotted as 
the Notostylops beds on his section of the coast of Patago- 
nia. This last it certainly is not. 
The unconformity between these white (or light) sandy 
clays and the Patagonian represents a regression period, 
during which Patagonia was not only above water, but 
extended an unknown distance further to the East. 
It was during this interval of time between the Upper 
Cretaceous and the Lower Miocene (Patagonian) that the 
limited and local land deposits known as Casamayor 
(=Notostylops), the Astraponotus, and the Deseado (= 
Pyrotherium) and probably other beds were laid down. 
In each case the age must be determined for the individual 
bed by its contents mostly; for as far as I know none of 
them overlap anywhere. 
