56 IOWA ACADEMY OF SCIENGES. 



new set of names applied to the formations, with only vague 

 attempts to indicate their equivalents elsewhere. About the 

 only formation that was correlated with any degree of certainty 

 with the northern section was the Boone chert, which was 

 thought to represent, in part at least, the Burlington limestone. 

 A short time ago* the typical Kaskaskia limestone was recog- 

 nized in northwestern Arkansas, and indications of the St. Louis 

 division near by in Missouri. Farther eastward, on the 

 branches of White river, in the last named state, the Kinder- 

 hook had been determined; so that all four subdivisions of the 

 Mississippian series were at last recognized for this district as 

 clearly as these formations had been farther north. In addi- 

 tion, the productive coal measures (Des Moines series) were 

 found to be present. The relations of these divisions to those 

 of the Arkansas geologists farther south was thus easily deter- 

 mined. 



Up to the beginning of the present year the only part of 

 the Ozark region in which the Carboniferous formations 

 remained uncorrelated with the typical sections was in north- 

 eastern Arkansas, in the Batesville district. Within the past 

 few months Wellerf has announced the results of his work here. 

 He has brought forth abundant evidence to show that the 

 formations in the vicinity of Batesville are capable of the same 

 subdivision and are as clearly defined as in the more typical 

 locality along the Mississippi river. His correlation of the 

 Arkansas formations are given in the table. 



Thus the exact parallelism of the Lower Carboniferous (Mis- 

 sissippian) formations around the whole of the Ozark dome 

 may be regarded as established as essentially similar. Why 

 this is so, and why it should be expected, will be referred to 

 more specifically in another place. 



In Arkansas the Carboniferous above the Mississippian series 

 has also remained without any exact determination as to posi- 

 tion in the general section of the Continental Interior, but in a 

 broad way it has been thought to be equivalent to the combined 

 upper and lower coal measures of Missouri and Kansas, or 

 about what has been more recently called the Des Moines and 

 Missourian series. The alleged enormous thickness of the coal 

 measures of the southern Ozarks — 1,000 J to 2,400§ feet has 



.American Geologist, Vol. XVI, p. ?6. 1895. 

 tTrans. New York Acad. Scl., Vol. XVI, v- 251, 1897. 

 $Wlnslow: Bui. Geol. Soc. America, Vo). II, p. 225, 1891. 

 §Branner: Am. Jour. Scl. (4), Vol. 11, p. 335, 1S96. 



