GEOLOGY OF SOUTHWESTERN IOWA. 369 



Tlie only exposures of Upper coal-measure strata in the 

 county are found in the valley of the Nishnabotany, or at or 

 near the base of the bluffs that border the Missouri river 

 flood-plain. Xear the exposures of sandstone before men- 

 tioned there is a slight exposure of Upper coal-measure 

 limestone, referable to a horizon nearly corresponding with 

 the coal-bed in the valley of the Xodaway. On section 5, 

 township 71, range 41, two or three small exposures of 

 impure, yellowish limestone and calcareous shales were 

 found, which are referred to about the same horizon. At 

 Glenwood, in the valley of Keg creek, and not far from 

 where it enters the great flood- fig. 38. 



plain, the following section was 

 measured, which is referred to 

 a horizon a few feet below that 

 of the last named exposures. * 



These are all that have yet been 

 observed in Mills county, except 



Q. c 



those important exposures along e, tii^imsl ^imss ^ m '' 

 the base of the Missouri river „?■--"- zzl~ _ l4 - 



bluffs. ^M^^~:^MMimd^ 



Section at Glenwood. 



No. 6. Bluff deposit 15 feet. 



No. 5. Drift 5 feet. 



No. 4. Dark-colored, carbonaceous shale 1 foot. 



No. 3. Compact, dark-cclored limestone 2 feet. 



No. 2. Unexposed 4 feet. 



No. 1. Sandstone, (seen in a well) 2 ' feet. 



The same layers of limestone represented in this section 

 are also exposed together with a few others, about a mile 

 further down the creek in the right valley-side. Going 

 down the valley of the Missouri along the base of the bluffs 

 we find some very extensive and valuable exposures of lime- 

 stone in the face of the bluffs at their base. These exposures 

 are six or eight miles southward from Glenwood and not 



far from the line of the Council Bluffs and St. Joseph 

 47 



