332 COUNTY AND EEGIONAL GEOLOGY. 



length, except near its confluence with Grand river, and 

 consequently, it presents the usual characters of a drift valley, 

 as do also all the other smaller streams of the county. 



The surface in the immediate vicinity of the larger streams 

 is somewhat broken and partially wooded, but much the 

 greater part, even of the eastern half the county, has that 

 gently undulating character of surface known as rolling 

 prairie. 



Geology. If Union county be divided into four equal parts 

 by east-and-west and north- and- south lines, all the exposures 

 of strata, with a single exception, so far as now known, will be 

 found in the southeastern quarter. That exception is a small 

 exposure in the banks of a creek about two miles northeast 

 from Afton. All these strata belong to the Upper coai- 

 Fig. 22. measure formation, and nearly all 



of them are found in the valley of 

 Grand river. 



On section 36, township 71, range 

 28, just where Twelve Mile creek joins 

 Grand river, the section represented 

 by Fig. 22, was measured. 



Section at the Mouth of Twelve Mile Creek. 



No. 3. Yellowish gray, thin bedded limestone 16 feet. 



No. 2. Compact, grayish limestone, (one layer) 1 foot. 



No. 1. Bluish, concretionary, marly limestone 3 f^et. 



Total 20 feet. 



The base of No. 1 was not seen, nor were any lower strata 

 found exposed there. The water being high at the time of 

 Fig. 23. our visit may, however, have covered 



some others. Going up Grand river 

 r valley, the next exposure of any impor- 

 tance is found in the right bank of the 

 ^' stream on section 14, township 71, range 

 28, at which point the following named strata appear and 

 are illustrated by Fig. 23. 



