THE CHESTER SERIES IN ILLINOIS 289 



includes much shale and sandstone. It is, however, the first epoch 

 of calcareous sedimentation in Chester time, and while locally there 

 were considerable accumulations of clastic materials near the shore 

 lines of the period, at a distance from the shore the material 

 deposited was wholly limestone and calcareous shale. The name 

 of the formation has been derived from Renault township, the 

 southernmost township in Monroe County. The belt of outcrop 

 of the formation crosses the whole of Monroe County in a north 

 and south direction, and extends northward across the southwestern 

 portion of St. Clair County and southward across the northwestern 

 corner of Randolph County. The outcrops of this formation along 

 Hickman Creek, in St. Clair County, are the most northerly 

 exposures of any Chester formation. In a southerly direction the 

 formation is exposed west of the Mississippi River across the 

 southeastern corner of Ste. Genevieve County, Missouri, and con- 

 tinues for a short distance into Perry County. 



Throughout the area of outcrop of the Renault in these Missis- 

 sippi River counties, the formation is constituted of a very great 

 variety of sediments, hmestone, sandstone, and shale being repre- 

 sented, with each type of rock exhibiting great variation in its 

 Hthologic characters. In fact, one of the characteristics of the 

 formation in this typical region, is its notable heterogeneity. This 

 great variety in sedimentation is doubtless due to the beds having 

 been laid down in proximity to the shore Kne of that time. 



Beyond the Mississippi River counties, the Renault is known in 

 Union County and from here it outcrops ,in a continuous belt, 

 except where it is interrupted by faulting, acrofes Illinois to Hardin 

 County, and is also known across the Ohio River in Kentucky. 

 In Union County the formation contains a considerable amount of 

 clastic material in its lower part, perhaps including the flaggy 

 sandstone east of Anna, which has already been mentioned as 

 possibly representing the Aux Vases. Besides this sandstone and 

 some overlying, variegated shales there is nearly or quite 100 feet 

 of Hmestone referable to the Renault in the Union County section, 

 and the hmestone continues across the state, but not everywhere 

 with this thickness. In the southeastern part of the state, espe- 

 cially in Hardin County, and also in Crittenden County, Kentucky, 



