104 ILLINOIS ACADEMY OF SCIENCE. 



gas and oil. The best exposures are in Sweetland Creek, and 

 hence the name, the Sweetland Creek Shale. 



Under the Kinderhook limestone at Burlington in Iowa, there 

 are some 300 feet of shale overlying the Devonian limestone. In 

 this locality this shale has usually been referred to the Kinderhook 

 group. Whether these two shales are different formations, one 

 overlying the other unconformably, or whether they belong to the 

 same formation, is at present an undetermined question. The 

 lower part of the shale at Muscatine was referred to the Che- 

 mung by Prof. Hall long ago, and its fish and crustacean fauna 

 support this view. 



During the progress of some examinations of samples of well 

 drillings in the north and central parts of Illinois, I have found a 

 shale resembling the Sweetland Creek shale in several wells. The 

 identification of this shale with the Sweetland Creek is beheved to 

 be sufficiently certain. It is based upon the similarity in texture 

 and general appearance of both shales, on the presence in both of 

 Sporangites huroncnse, in the presence of certain fossil fragments 

 resembling denticles of annelids, and in the presence in some well 

 samples of a Lingjila. The formation varies in thickness from less 

 than a hundred to 300 feet, owing no doubt to an unconformity. 

 The observations made on the shale in several of the wells are 

 as follows : 



GALESBURG CITY WELL NUMBER 3. 



In the Galesburg city well number 3, made in 1906, there was 

 a light gray shale underlying the coal measures at a depth below 

 the surface of 245 feet. With this shale were some pieces of white 

 chert, evidently from a remnant of the Burlington limestone 

 above. Some more shale was taken from 330 feet below the sur- 

 face. This was labeled "brown shale." It contained Sporangites in 

 abundance, well preserved. When crushed by the drill it no doubt 

 gave a brown color to the shale, that otherwise is gray. The next 

 sample below this was from 380 feet below the surface and con- 

 sisted of a soft shaly limestone, probably Devonian, The shale at 

 this place may be a hundred feet thick. 



THE OLD MONMOUTH CITY WELL. 



In the well drilled in 1887 at 410 North Sixth Street, in the 

 city of Monmouth, a greenish gray shale, no doubt equivalent to 

 the Kinderhook shale at Burlington, in Iowa, extends from 168 to 

 299 feet below the surface. Under this there is a dark gray shale 



