52 GEOLOGY OF ILLINOIS. 



On the lower course of the Bonpass, in the vicinity of Grayville, and 

 in some of the valleys of the smaller streams, stratified clays are found 

 at the lowest levels seen, which may belong to an older deposit than 

 the drift, and a heavy bed of this kind is reported to have been passed 

 through in the boring south-west of Mount Carmel, but as it was over- 

 laid by sandstone, and no rock of this kind is known in this county of 

 more recent age than the Coal Measures, I am inclined to doubt the 

 correctness of the report. However it is by no means improbable that 

 there are old valleys along the Wabash, as well as the Mississippi and 

 Ohio, that were filled originally with Tertiary or Cretaceous deposits, 

 some of which still remain, and are now hidden by the subsequent 

 accumulations of loess and drift. Indications of the existence of such 

 beds have been found on the Ohio as far north as Louisville, and on the 

 Mississippi for more than two hundred miles above St. Louis, the evi- 

 dences being well preserved shark's teeth found at various points within 

 the region specified, some of which are too fragile and delicate to have 

 been transported for long distances by drift agencies without destruc- 

 tion. The reported sandstone above the clay in the boring is most 

 probably a Coal Measure bed, and the reported clay beneath it may be 

 a soft clay shale of the same age, such as is frequently met with in the 

 coal-bearing formations. At Mount Carmel the loess and drift clays 

 are about thirty feet in thickness, which is probably about the average 

 in the vicinity of the river bluffs, while on the uplands, remote from the 

 river, their average thickness is not more than fifteen to twenty feet, 

 and at many points much less. 



In Edwards county the Quaternary beds present the same general 

 character, and are considerably thicker in the bluffs 011 the lower course 

 of the Bonpass than in the central and western portions of the county, 

 where we only find from fen to twenty feet of buff or brownish gravelly 

 clays overlaying the bed rock. Near Grayville the creek banks show 

 outcrops of five to ten feet or more of stratified clays, variously colored, 

 and seemingly derived from the decomposition of the clay shales of the 

 Coal Measures, and above these we find from twenty to thirty feet of 

 loess possibly covering a nucleus of gravelly drift clay. To the north 

 and west the loess is not conspicuous, and in digging wells the bed rock 

 is usually reached after passing through ten or fifteen feet of brown 

 drift clays. 



Coal Measures. 



In the bluffs of the Wabash river, at Mount Carmel, there is an out- 

 crop of saudstone forming the lower portion of the bluff, underlaid by 

 a blue clay shale but partially exposed. 



