LoGaN. | | The Upper Cretaceous. 203 
the Arkansas river has cut into and eroded away the Dakota 
rocks, making a great southern bend in the Dakota area. 
There are many small Cretaceous outcrops lying in the great 
Vertiary area south of the Arkansas river that usually occur along 
the streams which have cut through the overlying Tertiary forma- 
tion. Outcrops of the Comanche, a member of the Lower Cretaceous, 
occur along the border of the Red-Beds in the southwestern part of 
the state. 
The width of the lower Cretaceous area is only a few miles in 
extent. The formation extends from near the northern part of 
Barber county along the western border, thence across Comanche 
and Clark counties to Meade county. These outcrops form narrow 
borders along the northern tributaries of the Gimarron in the above- 
named counties. 7 
The outcrops of the Upper Cretaceous are found farther to the 
west. A small Dakota area occurs on the Cimarron river in the 
southwestern part of Morton county. A much larger area is found 
along the Little Cimarron in the northern part of the same county. 
A small area of Dakota occurs on a tributary of the Cimarron in 
the extreme southern part of Stanton county. A similar outcrop is 
found a few miles north on Bear creek in the same county. The 
jargest Dakota exposure occurs on a tributary of Bear creek, in 
the southern part of Hamilton county. The three outcrops last 
named extend into Colorado. They occupy a narrow strip on the 
banks of the streams. 
The Bentén is represented south of the Arkansas by a few small 
onicrops. «A small area occurs in the southern part of Gray county. 
This is entirely isolated from the main body of the Cretaceous, being 
surrounded by the Tertiary formation. A similar outcrop is found 
about midway between Bear creek and the Arkansas river in Ham- 
ilton. Along the Arkansas river from Hartland, in Kearny county, 
bevond the western line of the state into Colorado, the Benton 
outcrops, are aimost continuous. They occupy here, as elsewhere 
in this part of the state, however, but a narrow belt along the banks 
of the river. 
On the northern tributaries of the Arkansas in the same region, 
Niobrara exposures rest conformably on the Benton rocks. No 
