CORRELATION OF TlIK CiKNKltAI. SICCTIONS 183 



the enormous vertioiil nieasurenient of 20,000 feet. Thin ^reat terraiie, 

 composed almosst entirely of shales and sandstones, lies entirely helow 

 the basal horizon of the Des Moines series (Lower Coal Measures) of 

 Missouri, Init is above the Kaskaskia beds. 



The Des Moines series of Missouri api)ears to have its almost exact 

 equivalent in Indian territory in the Cavaniol group and in Arkansas 

 in the Poteau division. 



The Missourian series, up, perhaps, as far as the Plattsmouth lime- 

 stone, corresponds closely with the Poteau division of Indian territory. 



The so-called Permian of Indian territor}^ seems to be the upper part 

 of the Missourian series. The strata above the horizon of the Cottonwood 

 limestone of Kansas are not known definiteh^ to occur within the limits 

 of Indian territor3^ 



FA UNA L COMPARISONS 



I 



As yet no complete faunal studies have been made with the special 

 object in view of careful correlation of the various formations throughout 

 the coal field. What suggestions the fossils have offered are, however, 

 not without interest. This is particularly so when the north and south 

 parts of the field are compared. 



The most important published data on the fossils of the Arkansas Coal 

 Measures are by Smith.^ This author is of the opinion that the Lower 

 Coal Measures and Upper Coal Measures of Arkansas are to be paralleled 

 with the similarly named formations farther north. He concludes that — 



" There is not sufficient reason for classing the Poteau Mountain beds Avith the 

 Permian, but their fauna, as well as stratigraphic position, place them very high 

 in the Coal Measures, since they are like the fauna and position of the Mississippi 

 Valley Upper Coal Measures. Tliese beds derive an additional interest from the 

 fact that on Poteau mountain 1,000 feet of shale, in which no fossils were sought 

 for, lie above the thin layer from which the entire collection was taken." 



The correctness of this conclusion has been questioned.! A careful 

 comparison of the species of fossils that are considered by Smith to 

 belong to the Upper Coal Measures with those from the Upper and 

 Lower Coal Measures of other parts of the Western Interior basin brings 

 out the fact that the Arkansas fauna not only does not necessarily indi- 

 cate for the zone containing it a " very high " position in the more 

 northern Upper Coal Measures, but that it may be and probably is very 

 low. Judging from the fauna alone and as a whole, according to the 

 paleontological standard of its nearest and most closely related district — 



*Proc. Am, Philos. Soc, vol. xxxv, 1896, pp. 213-285. 

 t Journal of Geology, vol. vi, 1898, pp. 356-3G5. 



