INDIAN TERRITORY GEOLOGICAL SECTION 181 



coal fields have been extensively developed and the coal seams traced 

 for long distances. On acconnt of the wide extent of tlie coal beds the 

 various sections in this part of tlie territor}" are readily compared witli 

 one another and with those of the neighboring state on the east. Tliere 

 are three notable seams in the Choctaw field : the Grady (Huntington, 

 of Arkansas), the McAlester, and the jMa3'berr3\ Drake's Cavaniol group 

 embraces the strata between the Grady and Mayberry coals. The maxi- 

 mum distance between these two horizons is estimated by Drake to be 

 5,000 feet, though in his general section it is only about 1,700 feet. 



When we come to compare Chance's section * with that made by Drake, 

 we find that he places the distance between the two coals at a little over 

 8,000 feet, which is certainly excessive, as has already been suggested. f 

 With the exception of the 1,200 feet of shale above the Mayberry or 

 Kavanaugh coal and 200 feet beneath the Grady coal, the whole of the 

 Chance section would belong to the Cavaniol group. 



Stevenson J has paralleled the section made by Chance with Wins- 

 low's section of the Coal Measures of western Arkansas in his yet un- 

 printed report. It seems impossible to reconcile this attempt with the 

 known facts. Winslow states § clearly that the Huntington (Grady) 

 coal is near the base of his Poteau stage. This being the case, his six 

 other stages are all below the base of Chance's section. This feature 

 is shown in plate 19. 



In this connection it may be said that Drake's Poteau group is not 

 the Poteau of the Arkansas geologists. Winslow's Poteau stage, and, pre- 

 sumably, also Branner's, extends upward from the Grady coal horizon 

 to- the beds at the top of Poteau mountain, an horizon near the Mayberr}'- 

 coal. The Poteau formation of Arkansas is, therefore, practically the 

 exact equivalent of Drake's Cavaniol group, while the latter's Poteau 

 lies wholly above the Poteau of Arkansas. 



In regard to the low^er part of the section, it may be stated that what 

 Drake calls the Lower Coal Measures is below the Lower Coal Measures 

 of Missouri and Kansas. The Lower Coal Measures of Indian territory, 

 which are not the Lower Coal Measures of the region farther north, are 

 very thin at the north and are there merged with the basal standstone of 

 the Des Moines series. Southward they rapidly increase in thickness 

 until, beyond the Arkansas river, they have an ascribed measurement 

 ot more than 2,000 feet. In Chance's section of the Choctaw coal field 



♦Trans. Am. Inst. Miu. Eng., vol. xviii, 1890, p. 658. 

 t Journal of Geology, vol. vi, 1898, p. 358. 

 I Trans. New York Acad. Sci., vol. xiv, 1895, p. 52. 

 gibid., p. 51. 



XXVII— Bum,. Geoi,. Soc. Am., Vol. 12. 1900 



