1897.] DRAKE — THE GEOLOGY OF INDIAN TERRITORY. 407 



PART III. 



Economic Geology. 



The coals of the Indian Territory are at present its most im- 

 portant geologic product. The part of this paper treating of 

 economic geology must therefore be devoted principally to coal. 



Coals of the Choctaw Field. 



Grady Bed. — The outcrops and workable areas of the Grady coal 

 bed are confined to three continuous narrow belts. One belt 

 encircles the Backbone anticline, one the Bokoshe-Milton anticline, 

 and the other lies at the south bases of the Poteau, Cavaniol and Sans 

 Bois mountains. The bed around the Backbone anticline enters the 

 Indian Territory on the north side of the axis east of Pocola, 

 and runs about S. 80° W. At the Territory line the bed is almost 

 horizontal, or dips slightly to the north, as shown in Section No. 5, 

 which was made across the Backbone anticline southeast of Pocola. 



One mile west of Pocola the coal bed dips 15° to 20° to the 

 north ; the coal is three feet and seven inches thick, and has one 

 thin parting of shaly coal nineteen inches from the bottom of the 

 bed. Fire clay underlies the coal and arenaceous clay shale over- 

 lies it. The increased dip of the coal bed to the west from the 

 Territory line is probably due to the decrease in the throw of the 

 fault along the north side of Backbone mountain, so that the strata 

 enter into the anticlinal fold. It is possible that the Poteau river 

 west and north of Pocola runs along a gentle anticline ; if so, the 

 coal bed is deflected down that stream on either side. The dip of 

 the rock west of Pocola, however, does not make this probable. At 

 any rate, a few miles west of Poteau river along the general direc- 

 tion of the coal outcrop, the dip of the rocks shows conclusively that 

 the bed is continued westward from that place. The coal bed has 

 been opened near the Kansas City, Pittsburgh and Gulf Railway at 

 several places on either side of Buck creek prairie and east of 

 Poteau river. This coal is being worked to a very limited extent a 

 half mile east of Poteau river and a half mile south of James fork of 

 Poteau river ; the coal at that place is twenty-eight inches thick, 

 dips 10° S. and is overlain and underlain by black clay shale. The 

 bed increases in thickness towards the west, so that a few miles 

 west of Poteau river it is four feet thick. The Bokoshe- Milton 

 anticlinal fold brings this coal bed up so that its outcrop swings 



