536 E. RUSSELL LLOYD AND C. J. HARES 



The upper sandstone of this section probably belongs to the 

 Fort Union formation and the remainder to the Cannonball member 

 of the Lance formation. 



Sections similar in general character to those given above are 

 exposed in the bluffs of Heart River and on Cedar Creek. The 

 general appearance of the more sandy rocks is very much like that 

 of the Fox Hills sandstone. The shale is very much like the 

 Pierre. 



A peculiar feature of both the Fox Hills sandstone and the 

 Cannonball member of the Lance is the abundance of round con- 

 cretions commonly known as ''cannonballs." They are formed 

 by cementation of the sandy shale by the deposition of calcium 

 carbonate. These are true septarian nodules with radiating and 

 concentric veins of calcite. The best examples observed are in a 

 railway cut a few miles west of Raleigh, North Dakota. Where 

 the " cannonballs " are exposed by stream erosion they are mostly 

 weathered and broken to pieces. 



The rocks of the Cannonball member weather typically into 

 rounded hills, and in the interstream areas natural rock exposures 

 are very few. In a large part of the area where the member was 

 examined in South Dakota the only evidence that the beds are 

 of marine origin are a few thin beds of nodular fossiliferous lime- 

 stone, the presence of which is shown by the lines of residual 

 bowlders at the borders of level- topped hills. The topography is 

 such, however, that these horizons can be followed for long dis- 

 tances. No definite line could be drawn in the field between the 

 Cannonball marine member and the lower part of the Lance. The 

 contact of the two groups of strata is exposed at only a few places 

 and in all such cases it seems to be impossible to tell where the beds 

 of non-marine origin stop and those of marine origin begin. It 

 follows from the foregoing statement that there is no evidence of 

 unconformity at this horizon. 



The relationship of the Cannonball member with the under- 

 lying lower part of the Lance is well shown in the region northwest 

 of Solen on Cannonball River, North Dakota. In this area the 

 characteristic chaos of badlands, formed by the erosion of the 

 sandstone and shale of the lower part of the Lance, is bordered on 



