FIELD INVESTIGATIONS IN 1 92 1 833 



information regarding the facts that may be found in Johnson and Pope 

 counties, which cover the gently synclinal area between Union and Hardin 

 counties. Formations or parts of formations seem to be present in this 

 intervening area that are wanting in the Mississippi Valley to the west 

 and the Ohio Valley to the east. We know what we have in Kentucky 

 and in the highland rims and in the Appalachian Valley to the south and 

 east of Kentucky and are able to correlate the Chester formations very 

 satisfactorily throughout this great extent; but we do not yet know how 

 to explain all of the difficulties encountered in crossing the southern end 

 of the State of Illinois. 



In considering the Union County section I am fairly well satisfied 

 with the correlations of the beds from the Saint Louis to the top of the 

 siliceous limestone that Mr. Butts and I regard as corresponding to the 

 Yankeetown. Only the 60 feet of mainly limestone beds above this 

 siliceous rock offer any serious difficulties. Professor Weller refers these 

 limestones to the age of the Eenault; and as the Yankeetown overlies 

 the Eenault in their typical exposures, he is obliged to place the Yankee- 

 town zone in some higher position in the section. He does this by cor- 

 relating the Yankeetown with the 5-foot sandstone which rests on these 

 limestones in Union County. I, on the other hand, see no decisive 

 resemblance between either the faunal or the lithologic characters of this 

 questioned part of the Union County section and those of the Eenault as 

 developed in Missouri less than 50 miles to the northwest. This difference 

 between sections in areas so little separated is part of the evidence on 

 which in 1917 I postulated an incompletely separated basin in the Missis- 

 sippi Valley proper that is distinguished from the remainder of the 

 Illinois Chester basin mainly by the Okaw limestone, which is either 

 wanting elsewhere or represented by very different deposits. 



The fauna of Bed IX of the section in Union County, Illinois. — As 

 stated, the questionable 60-foot limestone and shale zone (Bed IX of 

 correlation chart) contains an abundance of well preserved fossils. 

 Pentremites of a few species are very common ; also fenestellid and other 

 Bryozoa. However, judging from our collections, both Lyropora and 

 Archimedes are rare and fewer than one would expect. Then there are 

 three or possibly four species of Talarocrinus, none of which seems to be 

 quite like any of the three or four species of the genus found in the 

 Eenault of Missouri. Two of the four suggest T. inflatus, the type of 

 which came from the Eenault in Monroe County, Illinois, and also T. 

 trijugis, the type of which is from the Upper Ohara in Hardin County. 

 But I am sure that neither is exactly like either of the described species. 



