DETAILS OF TIIIO KED VALLEY. 143 



clay of the Red Valley at an angle of 15° or 20°, and niarkinfr closely 

 with its inner margin the edge of the timbered area. It is frequently cut 

 by little ravines or gulches that head back a short distance in the Hills, 

 and from it arise many springs of deliciously cool water. One of these 

 springs near Elk Creek is of such size that the stream to which it gives 

 rise flows through and beyond the foothills. The surface of the limestone 

 is cracked and weather-worn, and is bare of soil for long distances, form- 

 ing a hard and somewhat slip})er3' pavement. 



Near Rapid Creek, immediately above this limestone, the following 

 strata of the Red Bed series were observed: 



Feet. 



6. Claj', red, with some gypsum — 



5. Gypsum, white 8 



4. Clay, with several seams of gypsum near the base 40 



3. Gypsum, white 8 



2. Clay, red, with some gypsum 75-100 



1, Limestone, purple 25 



In the region of Elk Creek and Warren Creek the purple limestone is 

 tilted at a much higher angle than fartlier south, inclining 45° to 60° to 

 the eastward, and the Red Bed valley is corres})ondingly pinched. At the 

 same time it is more broken and scored by the minor drainage. Its greatest 

 constriction is near Crook City,* and beyond that point it opens out through 

 the valley of White wood Creek into the broad valley of the Spearfish find 

 Redwater, where the upper Red Beds find their greatest expanse. From 

 the Spearfish the valley runs westward to Sun Dance Hills, with a width 

 of five to eight miles, and then, bending around the northwestern end of the 

 Hills, is confluent with the Avide expanse near Inyan Kara. 



Figure 22 gives a section from the Cretaceous rampart or foothills to 

 Black Butte, the line running just east of Spearfish Creek. 



The purple limestone all about the north end of the Hills has a low dip, 

 averaging less than 10°, and the exposure of its upper surface is verj' broad, 

 sometimes four or five miles. Its surface is frequently warped and bulged, 

 but it is broken only by erosion. It is not only treeless, but for the most 

 part soilless and grassless. Around the volcanic peaks — Crow, Sun Dance, 



*Oii tJic geolo<;ical map the oiitcropof the Rod Beds is rt'pres<'iited too Itroad at Crook City. The 

 colors for Jura and Cretaceous should have been uiaih; to follow the contours on the west side of the 

 creek. Wherever the text and the map are at variance the former is to be preferred; the coloring of 

 the map was completed after Mr. Newton's death. — Ed. 



