DETAILS OF STRATIGRAPHY 367 



The close similarity of the fossils from the different Edgewood locali- 

 ties compared in the above table leaves no doubt of the general equiva- 

 lence of the strata from which they came. The oolite bed at Louisiana 

 (Noix oolite member) is equivalent to about the upper two-thirds of the 

 Cyrene member of the Edgewood limestone as developed near Thebes, 

 Illinois, and east of Edgewood, Missouri. 



East of Louisiana the oolite bed becomes thinner, so that where it ap- 

 pears in the Mississippi bluff on the Illinois side of the river, 10 miles 

 east of Louisiana, a thickness of about 3 feet is present. In these more 

 easterly exposures of the bed, in Pike and Calhoun counties, Illinois, the 

 lower part of the oolite present at Louisiana, Missouri, is absent and the 

 bed is overlain by 12 to 16 feet of brown Bowling Green limestone, which 

 is in turn followed by the Sexton Creek (Brassfield) limestone. 



Near the south margin of the area of outcrop of the Alexandrian strata 

 in northeast Illinois, in the east bank of the Kankakee Eiver, 3% miles 

 below Custer Park, there is exposed a bed of iron-stained oolite Sy 2 feet 

 thick, which is thought to be the equivalent of the Noix oolite in Missouri 

 and western Illinois. It rests on Maquoketa shale and is succeeded by 

 6 to 9 feet of brown limestone, resembling the Bowling Green member, 

 which is in turn followed by the Sexton Creek (Brassfield) limestone. 



The oolite development appears to be restricted to the north and east 

 parts of the area of the Edgewood limestone bordering the Mississippi 

 Eiver and to the south side of the area of Alexandrian rocks in north- 

 eastern Illinois. 



The Channahon limestone member. — In the northeast Illinois area the 

 Channahon limestone member of the Edgewood limestone is exposed 

 along the south bank of Des plaines Eiver, about 1 mile southeast of the 

 village of Channahon, in Will County. This limestone also underlies the 

 surficial materials over a limited area on the north side of the river. A 

 section of strata exposed at the former locality is as follows: 



Section of Channahon Limestone near Channahon, Illinois 



Feet In. 



B. Dark gray to brown, rather flne-grained, impure limestone in 



layers 3 to 6 inches thick, containing many fossils 1 <> 



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

 are embedded numerous simple corals, besides Lcptasna rhomboi- 

 dalis, Schuchertella curvistriata, Pterinea elegans, Metapolichas 

 ferrisi, and other fossils l> 6 



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



to the level of the water in the river 5 



In the above section there is no apparenl unconformity between the 

 <liM'erent members, although Hie lithology of the sandstone al the base i^ 



