Ill 



In the Boone chert region of northern Arkansas, there are many 

 alluvial cones, composed almost entirely of fragmentary chert. This 

 chert withstands weathering to a remarkable degree. It readily permits 

 the rainfall to pass through it, thus preventing erosion, and forming an 

 ideal protection for the underlying rocks. 



Also, over this region, there are numerous knobs of the character 

 shown in Fig. 6. These knobs are capped with fragmentary chert, I'estiug 

 upon the magnesian limestone that underlies the Boone chert. The sur- 



F.J. 6 



I'nunding gecgraphy is that shown in Fig. 4. Nearly all the capping 

 material is angular, l)ut close search will often reveal water-worn pebbles. 



The Avriter is of the opinion that the capping material is that of 

 alluvial cones, and that the preservation of the rock beneath from erosion, 

 is due to the protection afforded by the cones. Such knobs are sometimes 

 500 I'eet above the valleys beneath. The small numljer of water-worn 

 pebbles is accounted for in the fact that the debris of the cones was 

 transported Ijut short distances, and there was not time for much round- 

 ing. Besides, the material is liard. and woiUd wear slowly. 



The material of these old cones must not be confounded with the 

 gravel that is common in this region, and which occurs on the hill sides 

 (see Fig. G) often extending up to the height of 2O0 feet or more above 

 the present stream level. This material, unlike that capping the knobs, 

 is all water-worn, mid was left on the inside curve of the streams as they 

 shifted laterally. 



