THE CHESTER SERIES IN ILLINOIS 



285 



shown that very little if anything new in the section can He looked 

 for there. 



In the course of these studies it has been found to be necessary 

 and perfectly practicable to subdivide the Chester series into six- 

 teen distinct formational units, which can be distinguished and 

 mapped with ease. The limestones of the series, with one possible 

 exception, are all continuous across the state, from their first 

 appearance from beneath the Pennsylvanian strata in St. Clair, 

 Monroe, or Randolph counties, on the northwest, to Hardin County 

 at the extreme southeastern part of the belt. The sandstone for- 

 mations, however, are not all continuous across the state; one has 

 its greatest development in the west, thins out, and disappears to 

 the east. Several of them have their great development in the 

 east and become much thinner or disappear entirely in the more 

 western portion of the state. The two uppermost sandstones of 

 the series, however, are present uniformly across the state. 



This entire series of Chester formations in IlHnois may be 

 arranged in three larger groups that possess rather distinct faunal 

 characteristics, and these three divisions may be designated as 

 lower, middle, and upper Chester. The names of these Chester 

 formations, with their arrangement in the larger divisions are as 

 follows : 



Upper Chester Group: 

 16. Kinkaid limestone 

 15. Degonia sandstone 

 14. Clore limestone 

 13. Palestine sandstone 

 12. Menard limestone 

 II. Waltersburg sandstone 

 10. Vienna limestone 

 0. Tar Springs sandstone 



Middle Chester, or Okaw Group: 

 8. Glen Dean limestone 

 7. Hardinsburg sandstone 

 6. Golconda limestone 

 5. Cypress sandstone 



Lower Chester Group: 



4. Paint Creek limestone 



3. Yankeetown formation, and 



Bethel sandstone 

 2. Renault limestone 

 I. Aux Vases sandstone 



In the naming of these units, those formations are designated 

 as Hmestones which include notable limestone beds. In all cases 

 such formations include a considerable amount of shale, in some 



