268 S. WELLER FAUNA OF THE FERN GLEN FORMATION 



3. Yellow and green shales, mostly covered with talus and soil — the 



Maquoketa shale Thickness, 80 feet 



2. Limestone, more impure and somewhat harder and darker colored 



than that below, with the typical Rhynchotrema capax fauna of 



the Richmond Thickness, 1 foot 



1. Highly crystalline, pinkish or light colored Kimmswick limestone, 



with numerous fossils at some horizons Thickness, 100 feet 



Still farther south these beds are exposed in the Mississippi Eiver 

 bluffs in the northern portion of Saint Genevieve county, Missouri, but 

 the writer has had no opportunity to study them in these localities. 



North of Saint Louis these Fern Glen beds have been observed at but 

 a single locality, in the Mississippi Eiver bluff just east of the station at 

 Chautauqua, in Jersey county, Illinois, on the Chicago, Peoria and Saint 

 Louis railroad. At this point the section is as follows : 



7. Typical Burlington limestone with an abundance of chert in 



bands Thickness not measured 



6. Greenish, more or less argillaceous lumestone with chert bands. 



W Thickness, 12 feet 



5. Yellow, apparently magnesian limestone with chert bands. 



Thickness, 4% feet 



4. Greenish limestone with numerous crinoid stems and abundant 



chert in bands from 1 to 4 inches in thickness. Some shaly 

 beds are present and the bed becomes more shaly below. 



Thickness, 13 y 2 feet 



3. Red, calcareous, argillaceous bed, typical of the Fern Glen forma- 



tion Thickness, iy 2 feet 



2. Greenish, shaly limestone with some chert bands Thickness, 3^ feet 



1. Hard, gray, or yellowish, more or less crystalline limestone, with 



occasional chert bands ; heavier bedded below, becoming thinner 



bedded and more cherty above Thickness, lO 1 ^ feet 



Besides the actual exposures of the Fern Glen formation, these beds 

 have been recognized in deep-well sections, both within the area limited 

 by the surface outcrops and also outside of this area. The peculiar 

 lithologic character of the beds, particularly their color, renders the for- 

 mation especially easy of recognition in well sections, and it has been 

 found to be of especial value in the correlation of such sections. The 

 formation is distinctly recognizable in three deep-well sections within the 

 Saint Louis area, in the Asylum well and the Belcher well in Saint 

 Louis, and in the Monks Mound well in Saint Clair county, Illinois, all 

 these sections being within the area limited by the surface outcrops of the 

 formation. At a distance from this region the Fern Glen formation is 

 clearly recognizable in a deep-well section at Chester, Illinois, where it 

 occurs at a depth of 1,656 feet with a thickness of about 30 feet. 



