UPPER SECONDARY ROCKS. 
257 
CHAPTER XXIIL 
GEOLOGY OF THE UNITED STATES. 
UPPER SECONDARY FORMATIONS. 
{Supermedial Order. Cretaceous, Oolitic, and Sand- 
stone Groups. — De la Beche. Saliferous System.) 
Upper Secondary. — Division. — How Distinguished from Ter- 
tiary. — New Red Sandstone. — What it Includes. — Its Range 
and Extent.— Oolite.— Green Sand. — Equivalent to Cretace- 
ous Group. — Its Fossils, — Its Range and Extent. — Mode of 
its Formation. — General Results. 
The rocks of this formation, we have already 
stated, are divided into four groups, viz. : 
1. Cretaceous or Chalk. I 3. Green Sand. 
2. Oolitic. I 4. New Red Sandstone. 
This group of strata is easily distinguished from 
those of the tertiary, not only by their chemical 
character and greater compactness in their mechan- 
ical structure, but also by a marked difference in 
their organic remains, and by a want of conformity 
in this strata, as they are rarely parallel to those of 
the tertiary, and also exhibit greater evidence of 
having been disturbed and changed from their ori- 
ginal position. The organic remains in this forma- 
tion are also mostly petrified ; in the tertiary they 
generally are not. The first three of the series are 
evidently of marine formation. 
New Red Sandstone. — According to our arrange- 
ment, proceeding upward, we find, next to the mill-- 
stone grit, the new red sandstone^ so called because 
Y2 
