306 T. E. SAVAGE ALEXANDEIAN ROCKS OF ILLINOIS AND WISCONSIN 



14 miles west of Kankakee. These strata consist of a thickness of 12 to 



15 feet of brown magnesian limestone, in layers 3 to 6 inches thick, that 

 are now known to belong to the Edgewood formation as developed in 

 southwestern Illinois and eastern Missouri. Above the Edgewood lime- 

 stone near Essex are a few feet of brown dolomite that contains silicified 

 shells of a pentameroid described by Foerste 2 as Platymerella manniensis, 

 and which has been considered the basal portion of the Sexton Creek 

 limestone in Illinois. 



Less than 10 miles northeast of the outcrop near Essex and about an 

 equal distance southeast of Wilmington, Illinois, an excellent section of 

 Alexandrian strata is exposed in the north bank of Kankakee River. At 

 this place typical Maquoketa shale is immediately overlain by a bed of 

 reddish-brown iron oolite, 3 or 4 feet thick, which is considered the 

 youngest member of the Maquoketa series in this region. Overlying the 

 iron oolite in apparent unconformity are 4 to 6 feet of brown magnesian 

 limestone belonging to the Edgewood formation. This limestone is suc- 

 ceeded by about 20 feet of hard gray to brown limestone, in layers 6 to 18 

 inches thick, which represent the Sexton Creek limestone as formerly 

 defined. The basal part of this limestone, as elsewhere in Illinois, con- 

 tains many shells of Platymerella manniensis. A zone 15 to 18 feet 

 above the base of the formation also contains numerous fossils, the most 

 significant of which are BJiinopora, near verrucosa; StricJclandinia triple- 

 siana; StricJclandinia, somewhat resembling 8. davidsoni Billings, de- 

 scribed in this paper as 8. pyriformis; another species related to S. salteri 

 Billings, and Triplecia, near insularis var. anticostiensis. 



Fifteen miles north of the exposure on Kankakee River strata corre- 

 sponding to the Edgewood and Sexton Creek limestones are exposed in 

 the banks of Desplaines River, iy 2 to 3 miles south of Channahon, in 

 Will County. A section of the strata as now known in this vicinity is 

 given below : 



Section of Strata exposed 3 Miles south of Channahon 



Edgewood limestone. p ee t 



3. Limestone, gray, crystalline, the lower part containing such typical 

 Edgewood fossils as Lyellia theoesensis, Atrypa prmmarginalis, 

 Dalmanella edgewoodensis, Camarotcechia ? concinna, Rhyncho- 



treta theoesensis, and Whitfleldella ovoides 11 



2. Limestone, brown ; corresponding in part to the limestone formerly 



described in the original Channahon section 10 



Maquoketa shale. 



1. Shale, bluish, plastic 8 



2 Aug. F. Foerste: Bulletin of the Denison University, vol. xiv, no. 6, p. 70, April, 

 1909. 



