20 



THE PERMO-CARBONIFEROUS RED BEDS OF 



lo feet, while none exceeded 15 feet. The shales are more heavily bedded. In 43 

 instances these measure more than 5 feet thick, while there were only 23 beds of 

 shale measuring less, than 5 feet. These relations are more fully presented in the 

 following table-: 



" Table showing frequency of different thicknesses of strata as described in the sections noted in 



Clay and Wichita Counties. 



THE WICHITA SHALES. 



"From the observations made in the field it appears that about 73 per cent of 

 the bulk of the shales of the exposed Wichita formation consists of greenish, bluish, 

 or light gray shale, and about 13 per cent consists of alternating layers of red and 

 gray shale, or blotched red and gray shale.* The greater part of this shale is fine 

 in texture, containing very few quartz grains which measure more than one-sixteenth 

 of a millimeter in diameter. 

 The Gray and Blue Shale. 



"The bluish-gray or greenish-gray shales are usually found under the sandstones 

 and limestones. We also find, in similar situations, streaky or blotched mixtures of 

 gray and red shale. 



"The gray or bluish-gray shale frequently contains minute fragments of chitinous, 

 brown, translucent fragments of scales of fishes, which sometimes also are found entire. 

 In some of the blue shales, these fragments are found in large numbers. * * * 



"Where the gray shales are dark they frequently contain minute imbedded 

 shreds of vegetation, and even entire leaves. Bituminous matter is also frequently 

 present in quantity sufficient to produce a bituminous odor when a fragment of 

 the shale is heated in a closed tube. When large concretions occur in this shale, 

 they are usually flat and consist of lime or of carbonate of iron. Small crystals of 

 marcasite also occur. These, as well as the concretions, have often been oxidized, 

 the concretions being more or less completely changed to limonite, and the marcasite 

 appearing as rusty specks in the shale. 

 The Red Shale. 



"The red shale constitutes the greater part of the exposed Wichita formation. 

 The red color is due to the presence of hematitic material. The red tints vary from 

 yellow to light red, dark red, purple, brown, and dark brown. Some of the red 

 shales are highly ferruginous, containing no less than 10 per cent of oxide of iron. 

 These are generally very fine in texture. The usual percentage of ferruginous 

 material is very much less, probably less than 5 per cent. 



"In its texture the red shale is very much like the blue shale, and varies from 

 very fine material to sandy shale. A small part of the shale consists of quartz 

 grains measuring more than one-sixteenth of a milKmeter in diameter. With this 

 ingredient there are usually some scales of mica. The hematitic material is present 

 in a state of extremely fine subdivision. 



» The excess of green and blue shale noted by Udden over that reported by other authors is in part 

 due to the fact that he includes some of the Clear Fork in his Wichita and in part due to the local character 

 of the beds in the area in which he worked. Compare his statement under "Red Shale."— E. C. Case. 



