340 
STRATIGRAPHICAL GEOLOGY 
kaskia division. On this point especial and critical inquiry is 
merited. 
The thickness of the Early Carbonic beds above the Genevieve 
horizon lately proves to be so great as that of the section of the 
same age below it. South of the Missouri River the initial forma¬ 
tion of the closing epoch is widely known as the Aux Vases sand¬ 
stone. 
In former years this sandstone, being a basal sandstone, was 
frequently mistaken for the bottom terrane of the Coal Measures. 
Being so nearly alike in origin it is doubtful whether the two 
formations could ever be distinguished from each other upon litho¬ 
logic features alone. 
There are strong physiographic reasons for believing that the 
Aux Vases sandstone, or its equivalents, may extend as channel 
deposits far beyond its now recognized outcrops. When laid 
down rapid diastrophic movements seem to have been taking place. 
On the other hand, when the Coal Measures were deposited they 
rest by contrast on a smooth peneplained surface. But whether 
or not the Aux Vases equivalents are found to extend north of the 
Missouri River, it is well worth while to bear in mind the pos¬ 
sibility and even the probability of their extension so far 
north as the limits of Iowa. The so-called basal sandstone of the 
Coal Measures should be examined critically with the possibility 
of their Early Carbonic age in mind. Thus, the same question 
bobs up again that 75 years ago so long puzzled geologists. 
The Aux Vases sandstone is, therefore, of especial interest at 
this time. Certain aspects of the original controversy are worthy 
of brief review and consideration as a possible aid in the interpre¬ 
tation of the northern problem. With these features in view the 
following notes are offered. 
When, as a terranal title, Aux Vases Sandstone was first pro¬ 
posed ^ it was intended that it should cover a thick, heavily bedded, 
arenaceous formation, which, in southeastern Missouri and south¬ 
ern Illinois, separated the St. Louis limestone from the Kaskaskia 
limestones. Although previously without geographic designation 
this was not the first recognition of the formation. More than 
half a century before this great sandstone was repeatedly noted 
1 Bull. Geol. Soc. America, Vol. Ill, p. 296, 1892. 
