180 C. R. KEYES — A DEPOSITIONAL MEASURE OF UNCONrORMITY 



if Drake's tracings in the field are correct we are able to tell quite closely 

 the relationships which the southeastern sections bear to those north of 

 the territory. 



Drake's correlation is that the Lower Coal Measures of Indian terri- 

 tory are (presumably) equivalent to the formation of the same title 

 farther north. The Cavaniol (Kavanaugli) is paralleled with the Mis- 

 sourian up to the Atchison (Waubaunsee) shales, while the Poteau is 

 made the representative of the latter and the Cottonwood terrane. The 

 exact grounds for this correlation are not clear, though it is inferred to 

 be chiefly the fossils. 



There are cogent reasons for believing that all of the Indian Territory 

 beds are much lower in thestratigraphic scale than Drake has supposed. 

 It has already been shown* that Smith's conclusions f "that Poteau 

 Mountain beds were high up in the Coal Measures,'' probably in part 

 Permian, are not necessarily correct. It was further stated that his de- 

 tailed evidence indicated rather tliat the beds in question were much 

 lower, possibly as far down as the horizon of the Des Moines series. 

 The data presented by Drake, and partly corroborated by personal ex- 

 amination, point to the correctness of the suggestion. 



Where the Cavaniol grouj), as indicated on Drake's map, is extended 

 into Kansas, it falls wholly within the boundaries of the Des Moines 

 series. The eastern limits are the same, if the basal sandstone is con- 

 sidered by itself. The upper or western boundary coincides with the 

 lowermost of the Bethan}' limestones. If the Poteau is rightly traced, 

 it corres})onds, in Indian territor}^ to the Missourian series of Kansas 

 up as far as })()ssibly the Plattsmouth (Oread) limestone, but certainly 

 not liigher. The details of the northern extension of Drake's Poteau 

 are obscure, and it is just possible that the limit is more nearly that of 

 the lola limestone. 



If this is the correct interpretation, and it appears that it is, Drake's 

 Cavaniol grouj) is almost the exact equivalent of the Des Moines series, 

 minus the basal sandstone of the more northern localities, while .his 

 Poteau group is to be paralleled witli the Missourian series below the 

 Plattsmouth limestone. The basal sandstone, placed by Drake in his 

 Lower Coal Measures, would api)ear to belong, toward the north, to 

 what has been regarded as a part of the Des Moines series, and to the 

 south to a lower horizon than any of that series north of the Kansas 

 line. 



In the eastern part of the territory, south of the Arkansas river, the 



♦Journal of Geology, vol. vi, 1898, p. 356. 



t Proc. Am. Philos. Soc, vol. xxxv, 189G, pp. 213-285. 



