GEOLOGICAL PAPERS. 97 



lion in the older formations. The center of the basin or main 

 S}'ncline of the State is not promising for prospectors. It has 

 been sufficiently drilled at an aggregate expense that is astounding, 

 to corroborate the theories just explained. Future drilling should 

 be based on the scientitic investigation which has been outlined 

 here. 



THE CHANNAHOX AND ESSEX LIMESTONES IN 



ILLINOIS.* 



By T. E. Savage, 

 Illinois State Geological Sur\-ey. 

 The Channahon and Essex limestones represent certain early 

 Silurian strata that have a restricted distribution in northern Illi- 

 nois and in the Mississippi valley. Small remnants or outliers 

 of these rocks have been found only in the counties of Will and 

 Kankakee. This paper is based on field studies and fossil collec- 

 tions made by Mr. A. J. Ellis and the writer for the State 

 Geological Sur\-ey. 



THE CHAXXAHOX LIMESTONE. 



The rocks referred to as the Channahon limestone outcrop in 

 the south bank of the Des Plaines River, about one mile southeast 

 of the village of Channahon, in Will Count}-. They also underlie 

 the surficial materials over a limited area on the north side of the 

 river. A section of the strata exposed at the former locality' is 

 as follows : 



Sectiox of Channahon Limestone. Feet. 



3. Dark gray to brown, rather fine-grained, impure limestone in layers 



3-6 inches thick, containing many fossils IH 



2. Dark colored limestone, consisting of a fine-grained matrix in which 

 are imbedded numerous simple corals, besides the fossils 

 Lcptcena rhomboidalis, Schuchertella cun-istriata, Ptcrinca ele- 

 gans, Metapolkhas ferrisi and others 2 J^ 



1. Fine-grained, yellowish-gray, laminated sandstone, without fossils, 

 to the level of the water in the river 5 



In the foregoing section there is no apparent unconformity 

 between the different members, although the htholog}' of the 

 sandstone at the base is markedly different from that of the over- 

 lying limestone, and the nimierous corals occurring in the second 

 member are absent in the upper bed. The contact of the rocks 

 described in the foregoing section with the Maquoketa shale 

 below, or with the Niagara limestone above, cannot be seen at the 

 point where the section was made. However, normal lower 



•Published by permission of the Director of the IlL State Geol. Surrey. 



