I'KODl TTIVI-: ("OAI. SKIMKS 177 



It will be noted that neiirly nine-tenths of the total coal output of 

 the three states mentioned conies from the Cherokee division alone. 

 This is about the proportion that the same terrane may he expected to 

 furnish in the future. l( anything, the Cherokee percentage will in- 

 crease rather than diminish, as the Henrietta coal comes from a single 

 seam, which lies very near the base of the formation. Hence, if we care 

 to take a few feet of this terrane and add it to the Cherokee, we wouUl 

 have practicalh^ 98 per cent of the entire Trans-Mississii)pian out})ut of 

 coal north of Arkansas coming from the lowermost member of the Coal 

 Measures — the Cherokee shales. 



The maximum thickness of the Cherokee shales mav be taken to be 

 about 300 feet. From this measurement the terrane tapers out east- 

 ^vardly to a feather-edge. If the total thickness of the Coal Measures of 

 the region (Des Moines and Missourian series) north of Arkansas ))e 

 taken at 2,000 feet, the basal one-seventh furnished 98 per cent of the 

 whole coal supply, present and future. 



PRODUCTIVE COAL SERIES /xV THE SOUTH 



In considering the coal output of the Arkansas valley the chief pro- 

 ducing strata are, according to Branner, not at the base of the Coal 

 Measures, but some 18,000 feet above. In western Arkansas this pro- 

 ductive terrane of Branner appears to include both the lower and east- 

 ern coal-bearing divisions of Winslow%^ the intermediate barren division, 

 of indefinite delimitation, and the chief coals of the upper or western 

 coal-bearing division. The highest coal horizons of the state were 

 apparently unknown at the time the report was made; at least their 

 real stratigraphical position was not appreciated. 



While some thin coals are known at other levels, the whole coal sup- 

 ply of Arkansas and Indian territor}'- south of the Arkansas river comes 

 from a terrane higher above the Kaskaskia beds of the Mississippian than 

 the whole Carboniferous section of Missouri and Kansas. In both jNIis- 

 souri and Arkansas the correlation of the Kaskaskia beds has been 

 determined with accuracy, so that their exact position is known. 



Geological Sections of the Region, 

 general considerations 



In the accompanying diagram (plate 19) are arranged the general 

 geological sections of the Trans-Mississippian Coal Measures as repre- 



•*Arkansas Geol. Survey, Ann. Kept. 1888, vol. iii, p. 22. 



