STRATIGRAPHY. 45 
Smaller deposits cap the high plateau northeast of Lake lone and the 
prominent butte east of McGill, and one extends through the elevated 
cross valley southeast of Garrett. 
The materials in the northern part of the area are mainly sands and 
sandstones or conglomerates. Along Little Medicine Bow Creek and 
adjacent slopes there are extensive badlands developed in white, 
gray, and greenish sands and sandy clays, and small outcrops of these 
materials appear in the other areas. Numerous remains of Titano- 
therium and Rhinoceros of Oligocene age occur in them, affording a basis 
for definite correlation with the Chadron formation of the White River 
group. In places near the mountain slopes there are bowlder beds, 
notably on the high terrace east of Lake lone, on the McGill butte, 
and in the southwest corner of T. 26 N., R. 74 W., where there are 
many bowlders of granite and other rocks from a few inches to 6 feet 
in diameter. These coarse deposits appear to overlie the finer ones, 
and in places the latter are underlain by old channels filled with loose 
coarse sandstone. Possibly some of the upper deposits and those at 
the higher levels represent Tertiary beds of later age than Chadron, 
namely, the Brule or upper member of the White River group. 
Possibly also the Arikaree formation is represented here, for its 
deposits extend high on the eastern flanks of the Laramie Mountains. 
^QUATERNARY SYSTEM. 
Extensive deposits of Quaternary age are present in the Laramie 
Basin as alluvium and high-terrace mantles, representing various 
stages of topographic development of the region. A small amount 
of glacial drift also occurs. 
GLACIAL DKIFT. 
A well-developed moraine which appears on North Fork of Little 
Laramie River a short distance north of Centennial is the product of 
an old glacier that once descended from the Medicine Bow Mountains. 
The material consists of till and bowlders of various sizes. The alti- 
tude is about 8,400 feet and the topography is typically morainic, 
with pits some of which are 30 feet deep. The bowlders are of varied 
composition, but a large proportion are made up of quartzite and 
quartzitic conglomerate, probably derived from the Algonkian rocks in 
the upper portion of the Medicine Bow Mountains. The mesa which 
extends from this moraine to the vicinity of Centennial village is also 
covered with these bowlders, as are likewise two small lulls 2 miles 
southeast of Centennial, 
HIGH TERRACES. 
Nearly all the low divide ridges throughout the Laramie Basin are 
covered by deposits of gravel, sand, and loam, many of them from 
30 to 50 feet thick. They are from 20 to 100 feet lugher than the 
