198 GENERAL GEOLOGY. 



those discovered are referred without doubt to the epoch of 

 the Kinderhook beds, the upper division being regarded as 

 equivalent to No. 3 at Indiantown, and No. 7 at Burlington. 

 Going up the river from Iowa Falls, the upper division 

 becomes somewhat more regularly bedded, and presents the 

 common aspect of magnesian limestone in the weathering of 

 its low cliffs. Still further up, at Alden, the lower division 

 rises again and appears in the banks of the river for a con- 

 siderable distance. 



The next we find of this formation is in the banks of both 

 branches of the Des Moines, in Humboldt county, just above 

 their confluence. At Springvale, on the west branch, there is 

 about fifteen feet in thickness of light gray oolitic limestone 

 exposed. It appears in the banks and bed of the stream for 

 the distance of nearly a mile and then passes from sight both 

 above and below. The rock here is all more or less oolitic 

 and is, without doubt, equivalent to Bed No 6, at Burlington. 



A couple of miles eastward from F g 



these exposures, other strata are 



seen exposed in the banks of the j ' ^^fer^^^^-j 2 ' 

 east branch of the river just above 2 /f^i^^i-A^ V 



the town of Dakota, and are repre- g?^^^_ 

 sented by fig. 

 These strata consist of the following beds : 



No. 4. Gray fragmentary limestone 1 foot. 



No. 3. Marly and sandy clay 2 feet. 



No. 2. Calcareous sandstone, in thin layers 6 feet. 



No. 1. Heavy bedded, yellowish, magnesian limestone 4 feet. 



No positive evidence of the relation of these strata to those 

 found at Springvale, a couple of miles to the westward, was 

 obtained, but they are supposed to belong above those oolitic 

 strata there, and in part equivalent to the upper division at 

 Iowa Falls. 



In the valley of the west branch of the Des Moines, about 

 five miles above Springvale, the Kinderhook limestone again 

 appears, showing a thickness of about fifteen feet. It is 



