226 



A. Winsloio — Cambricm in Missouri. 



taining the lead ore at the Doe Run mine, rises to the surface 

 and is exposed in the bluffs of the hills to a thickness of 70 ft. 

 or more. 



This bottom sandstone is encountered in the vicinity of Flat 

 River at depths of about 400 ft. Eastward from that place, 

 however, numerous drill holes put down in late years show that 

 the sandstone rises higher and higher and, about two miles east 

 of Farmington, it is exposed at the surface, on Wolf creek. 

 Thence, in the same direction, towards St. Genevieve, this 

 rock continues to occupy the surface to about the middle of 

 the county. Limestone then comes in again with an eastward 

 dip and is, in turn, succeeded by the overlying Saccharoidal 

 sandstone described by Shumard. According to our views> 

 then, the section along the line A-B, is as follows : 



Fig. 3. — A generalized section across St. Francois and St. Genevieve counties, 

 expressing the results of recent work. 



On comparing this section with fig. 2, on p. 224, it will be 

 seen that the principal difference is that the sandstone, termed 

 ''Second," overlies the limestone to the west in fig. 2, while, 

 in fig. 3, it underlies it. The consequence is that this great 

 body of limestone to the west, in St. Francois and Madison 

 counties, instead of occupying the position of what have been 

 called the Third or Fourth magnesian limestones is more prop- 

 erly in the position of the so-called Second magnesian lime- 

 stone, and the underlying sandstone becomes correspondingly 

 raised in the stratigraphic scale. Further, if the reasons cited 

 for placing the limestones of Madison county in the Cambrian 

 are good, we are of the opinion that all of the great body of 

 limestone described above as occurring in Madison and St. 

 Francois counties belongs to this age and the underlying sand- 

 stone and conglomerates also, as no stratigraphic break can be 

 recognized throughout the section. This would bring the 

 upper limits of the Cambrian to the base of what has been 

 called the Saccharoidal sandstone in Missouri, at least as iden- 

 tified in St. Genevieve county. 



