CLASSIFICATION OF UPPER PALASOZOIC ROCKS. 687 
Principal rivers. — Two river systems have cut approximately 
east and west valleys through this plateau, nearly at right angles 
to the trend of its flint ridges. The Smoky Hill and Kansas 
Rivers have cut the valley in the northern part of this range, while 
the Cottonwood River has eroded a similar valley through its 
central part. The great value of these two valleys in determin- 
ing the character and stratigraphic relations of the geologic for- 
mations composing the upper Paleozoic and lower Mesozoic 
rocks of Kansas was early appreciated, consequently these two 
great sections are classics in the literature of the Permian and 
Permo-Carboniferous rocks of Kansas. In a recent article the 
writer has discussed the geology of the Kansas River section, 
particularly from Manhattan to Junction City; identified and 
correlated as far as possible the various beds of that section as 
described by Meek and Hayden, Swallow, and Hay, and given 
lists of fossils which characterize the various divisions of the sec- 
Om INN ORESEME PRIDE [NO ODOSES 1 COMSIGIEr im a Sihonileye 
manner the classic section of the Cottonwood Valley and in addi- 
tion, to define briefly the formations into which the writer has 
divided the upper Paleozoic rocks of Kansas. 
The Cottonwood River valley.— About seven miles below the 
city of Emporia, the Cottonwood River enters the Neosho and 
reaches the Arkansas River near Fort Gibson in the Indian Terri- 
tory ; consequently the Cottonwood River forms a part of the 
great drainage system of the Arkansas. For more than twenty 
miles from its mouth, to a point near Ellinor, the Cottonwood 
River flows through a broad, fertile valley with low hills in the 
distance. But above Ellinor it rapidly narrows, except where 
tributary streams enter it, to a valley one or two miles in width, 
lined on both sides with steep hills which are generally capped 
by a prominent escarpment of massive limestone or flint. This 
type of valley continues westerly as far as the junction of the 
South Cottonwood River with the Cottonwood, two miles west of 
Marion ; and for some forty miles along the main line of the 
*Kansas River section of the Permo-Carboniferous and Permian Rocks of Kansas, 
Bull. Geol. Soc. America, Vol. VI., pp. 29-54. 
