1897.] DRAKE — THE GEOLOGY OF INDIAN TERRITORY. 367 



Grady coal bed. The third division comprises the strata of Black 

 Fork, Rich and Windingstair mountains. 



The highest bed of the Lower Coal Measures is a sandstone 

 about one hundred and fifty feet thick, although varying in thickness 

 from a few inches to three hundred feet. Mr. H. M. Chance calls 

 it the Tobucksy^ sandstone. This bed is especially important because 

 it immediately underlies the Grady coal bed and makes a ridge 



RUmiehi. Ml.. 



Sec. No. 9. Across the Winding Stair and the Kiamichi mountains, south of 

 Hanson creek. 



of considerable prominence almost all along its line of outcrops, 

 so that the coal may be closely located by tracing the outcrop 

 of this sandstone. It has an unusual persistence for a sandstone, 

 outcropping as it does almost regularly over an area of one 

 thousand square miles, and forming an unbroken ridge excepting 

 at a few places where streams have cut across it, from about three 

 miles northwest of Heavener to Hartshorne. This ridge is a very 

 prominent topographic feature rising usually one hundred to three 

 hundred feet above the surrounding country. South and southwest 

 of Heavener and southwest and west of Milton, this bed is thick and 

 makes ridges from one hundred to three hundred feet high. Where 

 it is thick enough to make a prominent topographic feature it is 

 shown so on the sketch map. The following are approximate sec- 

 tions of the upper part of the Lower Coal Measures as they occur 

 in Sees. 8 and 5 ; the sections were made south and southeast of 

 Heavener and across the Backbone anticline. 



SEC. 8. SEC. 5. 



FEET. FEET. 



Sandstone 200 50 



Gray arenaceous clay shale .... 1000 1150 



Massive sandstone 50 250 



Gray arenaceous clay shale 660 600 



Sandstone 30 35 



Clay shale 1^50 500 



1 Trans. Am. Inst. Aliii. Eng.^ Vol. xviii, p. 659. 



