290 STUART WELLER 



there are some shaly beds at the base of or just beneath the Renault 

 which have been called the Shetlerville formation, from Shetler- 

 ville, Hardin County, Illinois. These beds might perhaps be con- 

 sidered as a member of the Renault rather than as a distinct for- 

 mation, but they are characterized by certain faunal elements that 

 are somewhat different from the overlying Renault. There is 

 some reason to believe that the Shetlerville beds are represented 

 in the lower portion of what has been called Renault in Union 

 County, but further detailed field work is necessary to estabUsh 

 such a conclusion. East of Union County all of the beds of the 

 Renault or Renault-Shetlerville interval are limestones and more 

 or less calcareous shales. 



In the region of its typical development in Monroe County, 

 Illinois, the Renault exhibits a maximum thickness of about 

 loo feet, but it varies from this maximum to a minimum of less 

 than 20 feet, and doubtless actually thins out to nothing at all. 

 The exposures of the formation in Ste. Genevieve County, Missouri, 

 vary in thickness from about 46 feet to 75 feet or more, and there 

 may be a maximum thickness of 100 feet in the county. In Union 

 County there is 100 feet or more of Renault, but to the east of this 

 county the formation in combination with the Shetlerville, is some- 

 what less than this, varying from 60 to 80 feet in most sections. 



The Renault formation rests unconformably upon whatever lies 

 beneath it, wherever it has been observed in Illinois and Missouri. 

 In the Mississippi Valley counties it overlaps the Aux Vases sandstone 

 and in many places rests upon the older Ste. Genevieve or even on 

 the St. Louis Hmestone in places. The sub-Renault unconformity is 

 well indicated by the presence of a basal conglomerate at a number 

 of widely separated locahties. The best exhibitions of this con- 

 glomerate are in St. Clair County, Ilhnois, on a tributary of Hick- 

 man Creek three miles northwest of Millstadt, and in Ste. Gene- 

 vieve County, Missouri, about halfway between the mouth of 

 Sahne Creek and St. Marys. In both of these locahties the under- 

 lying formation is the Aux Vases sandstone. The conglomerate is 

 constituted of rounded pebbles of chert with an occasional pebble 

 of igneous rock, ranging in size from two inches in diameter to a 

 fraction of an inch. All through the southern counties of Ilhnois 



