40 WILLIS D LEE 
trenched by numerous streams to a sufficient depth to expose 
the shales which are the subject of this paper. 
There is no claim advanced that this vast region has been 
exhaustively studied. My purpose has been to trace the shales 
which underlie the Dakota sandstone, over as wide an area 
as possible. In so doing I have visited the canyons of the 
Apishapa, the Purgatory, the Rio Cimarron, the Canadian, and 
their tributary canyons, as well as the foothills of the mountains 
3 
a Sandstone, massive and quartzitic, somewhat conglomeratic in places. 
QA 
200 feet of varicolored shales with local beds of brittle limestone and lime 
S concretions. A coarse, loose-textured, cross bedded sandstone occurs near 
Nn the top: 
un 
as) 
vo 
f Deep red sandstone. 
3 
[aa 
Fic. 2 (Sec. I). Taken in the Rio Cimarron, 14 miles east of Folsom, N. M. 
where the sedimentary formations are sharply upturned. The 
itinerary is indicated by the dotted lines on the accompanying 
sketch map. 
Rio Cimarron Canyon.—There are two Cimarron rivers in 
New Mexico. The one referred to here, which for distinction I 
shall call the Rio Cimarron, flows eastward near the northern 
border of the territory, and finds its way through Oklahoma and 
Kansas to the Arkansas River. A few miles east of Folsom, 
N. M., the Rio Cimarron cuts through the Dakota sandstone 
and into the Red Beds beneath. The thickness of the Dakota 
was estimated at 200 feet at this point. Below this sandstone 
occurs twenty-five to fifty feet of soft variegated clay-shales, 
underneath which is a*series of gypsum layers inter-stratified 
*I am greatly indebted to Mr. T. A. Pierce for assistance in this work. He has 
taken an active interest in furthering the investigation. 
