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LA SALLE 

 LIMESTONE 

 MEMBER 



Most productive zone 

 for collecting conodont 

 assemblages is 

 represented by 

 fissile black shale 



-I FT 



u-2 



unnamed coal 



Fig. 9 - Detailed stratigraphic diagram of the 



beds underlying the La Salle Limestone -* 

 which yield natural conodont assem- 

 blages. The most productive col- 

 lecting zone (diagonal hatching) ex- ° 

 tends from the falls upstream past 

 the haulage road bridge, SE% SE% NW% 7 

 Sec. 6, La Salle County, La Salle 

 Quadrangle. See table 1 for addi- 

 tional information on conodont occur- 

 rences. 



Limestone - gray to greenish 

 gray, dense to crystalline; con- 

 tains small-scale algal struc- 

 tures; brecciated; brachiopods 

 common . 



Shale - greenish gray at top 

 grading downward to dark gray 

 and black, calcareous; weathers 

 light; poorly laminated; 5 to 

 7 inches in thickness . 



Shale - black, weathers dark gray 

 on surface; blocky, pyritic; 

 contains scattered plant remains, 

 as well as linguloid and orbicu- 

 loid brachiopods and fish scales. 

 Productive zone of well pre- 

 served conodont assemblages is 

 2 to 2^2 inches above the base 

 of unit and is about 1 inch thick, 

 Thin layers of gypsum occur at 

 the base of the zone in places, 

 above it in other places. 



Shale - black to dark gray at 

 top grading downward to gray; 

 plant debris and thin coals are 

 common; 1- to 2-inch discon- 

 tinuous limestone bed at bottom. 



Shale - gray to light gray; 

 plant debris common. 



Coal - 1 to 3 inches thick. 



Clay - gray to light gray. 



