880 DRAKE — THE GEOLOGY OF INDIAN TERRITORY, [Sept. 3, 



FEET. 



5. Clay shale 25 



6. Arenaceous limestone 5 



7. Sandstone 5 



8. Clay shale containing calcareous nodules and 



some fossils 25 



9. Gray clay shale, blackened in places by car- 



bonaceous matter often calcareous and occa- 

 sionally containing thin shaly sandstone 

 strata 300 



Total thickness (approximate) 650 



Bed 4 of the above section forms the bed-rock of Bird creek 

 about twelve miles from Skiatook along the Skiatook-Pawhuska 

 road. From that point to the eastward it gradually rises until it 

 forms bluffs on either side of the creek and farther eastward forms 

 an east-facing escarpment. 



This escarpment was seen about due west of Oologah and two 

 to three miles west of the Osage-Cherokee Nation boundary line. 

 The limestone bed is very massive, gray in color, unevenly tex- 

 tured, rather highly crystalline and contains little ferruginous masses 

 scattered throughout most of the bed. 



Origin of the Sediments of the Coal Measures. — Throughout the 

 Coal Measures the thickness of the sediments gradually decreases 

 northward and westward. The most rapid decrease is toward the 

 north, and the lower beds decrease more rapidly than the higher 

 ones. The Lower Coal Measures decrease from a thickness of 

 about seventeen thousand feet in the southern part of the field to a 

 thickness of five hundred to six hundred feet in the northern part. 

 The Upper Coal Measures across the same field decrease from about 

 seventy-five hundred to twelve hundred feet> 



The Permian beds, so far as they were studied, show very 

 little, if any, decrease in thickness toward the north. This con- 

 tinuous northward thinning of the beds in the central and northern 

 part of the field is shown in PL VIII. The relative proportion in 

 the amount of shales and limestones to sandstones and conglomer- 

 ates gradually increases westward and especially northward. Be- 

 cause of these conditions the sediments are considered to have 

 come from a land area lying to the southeast. 



