GEOLOGY OF SOUTHWESTERN IOWA. 375 



About a mile further northward from F lG - 41. 



Lewis, on section 1, township 75, range JpSSff ^* 



37, the following measurements were , ^l^EiPI^I 5 ' 

 made of strata exposed in the left bank 2 ^^^ ^^=1 < '- 

 of Turkey creek and illustrated by i s ^~~^-^ ~^-tm / 

 Fig. 41. 



Section on Turkey Creek. 



No. 5. Yellowish, calcareous clay, containing small masses of lime- 

 stone, almost entirely composed of Fusulina cylindrica. . 2 feet. 



No. 4. Yellowish, calcareous shale 5 feet. 



No. 3. Limestone with flinty concretions 1% feet. 



No. 2. Yellowish, marly clay, with one thin band of black car- 

 bonaceous shale 4^ feet. 



No. 1. Bluish, compact limestone 1 foot. 



Total 14 feet. 



No. 1 of this section is regarded as equivalent with No. 

 2 of the section on Chapman's branch, and both of these, 

 equivalent with No. 2 of the section near Lewis. 



A number of exposures of strata, belonging within the 

 same vertical range, also occur along the valley of Indian 

 creek, a few miles westward from Lewis. 



In the southern part of the county, in the valley of Sixteen 

 Mile and Seven Mile creeks, there are also considerable expo- 

 sures of Upper coal-measure strata, principally limestone. 

 They are usually small and unimportant, but some seen on 

 section 31, township 74, range 35, were about thirty feet in 

 vertical thickness, yet they were so incompletely exposed in 

 the valley-side that no satisfactory measurement of them was 

 made. They are, however, referred to about the same strati- 

 graphical horizon as that of the strata exposed near Lewis. 

 Thus, all the strata exposed in the county, except the 

 Nishnabotany sandstone, are all referred to the Upper 

 coal-measure formation, and all, apparently, confined to a 

 vertical range of forty feet at most. This range is regarded 

 as about equivalent to the lower half of the limestone strata 

 above No. 3 of the Winterset section, and also includes the 

 horizon of the Nodaway valley coal-bed. 



