124 ILLINOIS ACADEMY OF SCIENCE 



Renault with these limestones, when they are the immediately 

 subjacent rocks, is very clear, and in one point in Hickman 

 Creek, about two miles west of Millstadt, in the northern 

 part of the \\'aterloo quadrangle, an important bed of lime- 

 stone conglomerate is present in the base of the formation. 

 At this locality the conglomerate rests directly upon the Ste. 

 Genevieve limestone, and the rounded pebbles in the conglom- 

 erate are mostly from the immediate underl3-ing Ste. Gene- 

 vieve beds. The unconformity of the Renault upon the 

 Brewerville is not so obvious, but it seems to be clearly es- 

 tablished. The arenaceous character of the higher formation, 

 especially towards its western border, sometimes makes it 

 difficult to determine exactly the line of contact between the 

 two formations. In several localities, however, where the 

 Renault is represented by calcareous beds and the Cypress is 

 possessed of its typical, massive, unmistakable characters, 

 there are notable discrepences in the elevation of the con- 

 tact between the two formations within rather short dis- 

 tances, which would indicate an erosion interval preceeding 

 the deposition of the younger formation. Furthermore, in 

 a tributary of Hickman Creek, two and one-half miles north- 

 east of Millstadt. the Renault rests upon the Brewerville with 

 a limestone conglomerate in the base of the formation. 



3. Yankeetown Formation- 

 General characters. The Yankeetown formation, al- 

 though a thin stratum which probably never exceeds and 

 rarely attains 20 feet in thickness, is one of the most per- 

 sistent members in the Chester group of the Randolph-Monroe 

 county area. In all its outcrops where it has been exposed to 

 long weathering, the formation is almost completely silice- 

 ous, the color usually being light bufif or nearly white. 

 Where it has not been subjected to such long weathering, 

 or where it has been encountered in digging wells, it is com- 

 monly, in part at least, composed of highly siliceous lime- 

 stones ; some of the beds are slightly sandy, and locally the 

 formation is partly quartzitic ; where this quartzitic facies is 

 best developed, on Hickman Creek in the northern portion 

 of the ^Vaterlo quadrangle, the color is distinctly red or rose. 

 The bedding of the formation is commonly very irregular and 

 contorted. 



In its geographic distribution the Yankeetown extends 

 from the extreme northern portion of the Waterloo quad- 

 rangle to the Mississippi river bluffs, about two miles below 

 Modoc, near the southeastern corner of the Renault quad- 

 rangle, where it passes beneath the younger formations. The 

 bed is so resistant that in many localities it is well exposed in 

 stream beds where other members of the Chester are en- 



