FIELD INVESTIGATIONS IN 1 02 1 825 



we found and saw them and let the reader judge for himself as to their 

 significance. 



LOWER CHESTER SECTION IN SAINTE GENEVIEVE COUNTY, MISSOURI 



General statement. — Starting on the west, we will first consider the 

 section in Sainte Genevieve County, Missouri. It is represented in the 

 first column on the left of the accompanying chart of columnar sections. 

 Here we find the typical exposures of the two formations that are most 

 prominent in the controversy, namely, the Sainte Genevieve limestone 

 and the Aux Vases sandstone. It contains also a representative of the 

 Eenault formation, concerning which Professor Weller and I have dif- 

 fered very seriously. The contact between the Sainte Genevieve and the 

 underlying Saint Louis limestone is decidedly unconformable here. Pho- 

 tographs of this unconformity were published by me in 1917. At the 

 same time similar relations between these two formations were described 

 and illustrated as occurring in Sequatchie Valley, in southeastern Ten- 

 nessee; and in the meantime Mr. Butts' work in eastern Kentucky has 

 brought out the fact that this break is no less clearly indicated, also, on 

 the eastern side of the Cincinnati axis. 14 In short, the contact between 

 these two limestones is unconformable, or disconformable, if one happens 

 to prefer this term, at all places where this part of the stratigraphic 

 sequence has been observed, from Sainte Genevieve County, Missouri, on 

 the west to northeastern Kentucky on the east and northern Alabama on 

 the south. Moreover, throughout this wide extent this break is much 

 more generally and more clearly indicated than is any other in the strati- 

 graphic interval between the base of the Sainte Genevieve and the top of 

 the Gasper limestone, which brings us to the top of the Lower Chester or 

 Montesana limestone group of my classification. 



In view of these facts and also because of the practical absence of satis- 

 factory dividing planes in the Montesana limestone in many excellent 

 exposures in the Appalachian region, I may say that my view concerning 

 the most natural and the best indicated boundary between the Meramec 

 and Chester series is as definitely established as it can be done by the 

 physical criteria of the diastrophic method. As I find abundant support 

 for this conclusion among the organic criteria as well, it obviously follows 

 that I can not agree with Weller, who denounces this part of my classifi- 

 cation as "the most serious of Ulrich's mistakes." 15 



But to return to the section in Sainte Genevieve County, Missouri : 

 The lithologic characters of the Sainte Genevieve limestone vary greatly 



14 Charles Butts : The Mississippi formations in eastern Kentucky. Kentucky Geol. 

 Survey (in press). 



15 Op. cit., p. 129. 



LIV— Bull. Geol. Sue. Am.. Vol. 38, 1021 



