2 The American Geologist. January 1902. 
uw 
REVIEW OF RECENT GEOLOGICAL 
LITERATURE. 
The High Plains and their Utilization. Witarp D. Jounson. (Ex- 
tract from the Iwenty-first Annual Report U. S. Geol. Survey, Part 
4, Hydrography ). 
This excellent paper is a thorough-going treatment of the geology, 
climate and economic aspects of the high plains. In the interpretation 
of physiographic forms and the elaboration of the history of the plains, 
the author has also contributed a valuable discussion of certain princi- 
ples of erosion and deposition under conditions of aridity. 
The term “high plains” is used to designate a well defined sub-divi- 
sion of the great plains. The region so styled is a topographic unit 
consisting of an irregular but distinct north-and-south belt in western 
Nebraska, Kansas, Oklahoma and Texas, and eastern Colorado and 
New Mexico. It is literally and by pre-eminence “the plains,” as 
contrasted with the more dissected and more rapidly degrading re- 
gions on its west and east sides. As a climatic unit the region is 
distingushed as sub-humid, being intermediate between the humid 
prairies on the east, where farming without irrigation is practicable, 
and the arid plateau on the west with its characteristic conditions of at- 
mosphere and vegetation. 
The great plateau, sloping from an altitude of five or six thousand 
feet at the foot of the Rocky mountains, nearly to sea level at the Mis- 
sissippi river, is, in the main, a rock structure, and as such is to be 
accounted for by crustal movement; but a thin veneer (maximum 500 
feet), of unconsolidated Tertiary deposits lies upon its western por- 
tion. It is in the deposition and erosion of this superficial mantle that 
the climatic history of Tertiary and Quaternary time in this region is 
recorded. Mr. Johnson does not hesitate to pronounce the plains Ter- 
tiary a fluviatile deposit. ‘That this is so—that the deep silt, sand and 
gravel accumulation is of fluviatile origin—unmistakably appears upon 
detailed examination of its composition and structure.” It is common- 
ly spoken of as the “Tertiary Gravels,” but the great mass of its sub- 
stance is silt. Gravel and sand are prominent, but they do not consti- 
tute broad beds occupying definite horizons. They are, on the contrary, 
arranged in streaks which intersect like the lines of a net, but the 
meshes of this net are drawn out long in an east-west direction. These 
deposits are equally abundant and equally coarse at all depths. “The 
importance of the existence of gravel—even the fact of its existence—at 
all levels. has not been generally recognized.” These gravels are derived 
from the harder crystalline rocks of the eastern slope of the Rocky 
mountains. The pebbles are worn and decrease in size with distance 
from the place of their origin. There is no admixture whatever of 
freshly contributed fragments, such as may be found in beach gravels. 
Mr. Johnson finds absolutely no evidence on which to base the two- 
fold division of the plains Tertiary made by Prof, Hay, into a lower 
“Tertiary Grit” and an upper ‘Plains Marl.” 
EE 
