688 GEOLOGY AND TOPOGRAPHY OF THE LEAD REGION. 



8. A calcareous band cut by open joints or fissures, into which the materials of Ft- In. 



the layer above have penetrated , 4 



9. Dark olive shales, finely laminated and destitute of fossils 3 4 



10. Nucula bed, similar to the above, 4 to 6 inches 6 



Total thickness exposed 42 6 



A noticeable feature of the two Nucula beds, which are the lowest 

 of the series, is that the floor of each is a thin seam of pyrites of a 

 nodular and crystalline form which rests on the bed below. This 

 was the only metalliferous indication noticed in the formation, and it 

 did not seem to exist in great abundance. 



The beds of Galena limestone which underlie this formation are 

 quite regularly stratified in beds about six inches thick. In the west 

 end of the cut, the beds are perfectly horizontal on a course !N". 55 "W. 

 On a course at right angles to this, the dip was found to be about 50 

 feet per mile on a S. W. course. It is probable, however, that this is 

 only a local dip. 



Nothing of a metallic nature was discovered in the formation, ex- 

 cept a few small seams of marcasite in the lower beds. 



The best localities for obtaining fossils from this formation are on 

 the sides of the mounds, where the water has partly removed the 

 turf and soil, and formed gullies which are filled with broken frag- 

 ments of the different beds. Among these may be mentioned the 

 S. E. qr. of Sec. 22, T. 1, R. 2 E., near what is known as the Gratiot 

 place. The lower beds abound with shells of the Nucula fecunda; 

 the middle ones with Rhynchonella increbescens, Strophomena alter - 

 nata, and stems of Chcetetes. The upper beds contain a few Orthoce- 

 rata, but they are infrequent. 



The lower beds of the Cincinnati group have been exposed in some 

 old diggings in the N". E. qr. of sec. 2, T. 3, R. 1 E., on the road near 

 the Burris place. Specimens of the Nucula, and other shells charac- 

 teristic of the lower beds were here found in great profusion and per- 

 fection. 



