MOWER COUNTY. 355 



Cretaceous strata.] 



also belonging to the Cretaceous. This has already been mentioned at 

 Alderson's mill on Dobbin's creek, but its most interesting appearance is at 

 Sargent's spring. S. W. j sec. 31, Red Rock. It is below the level of the water 

 of a little pool. Pure, soft (?) water boils up over the area of about a square 

 rod, and sometimes over double that area, and can be seen issuing from the 

 ground, bringing with it clean white sand. The bottom of the pool presents 

 a beautiful appearance. The water is as clear as crystal, and the boiling 

 points which appear by reason of the rising white sand, in the midst of the 

 darker sediment, can be minutely inspected at a depth of five or six feet. 

 Running a stick into the agitated sand, it soon strikes a sandrock which is 

 doubtless the source of the boiling sand, and the same bed that furnished 

 that at the quarry in Dobbin's creek. 



There is also a white pebbly conglomerate, which passes into a ferruginous 

 grit, found in the eastern part of the county, that is referred, with some 

 doubt, to the Cretaceous age. This has been mentioned in the report on 

 Fillmore county.* It is seen in the north half of section 13, Frankford, in 

 the north-and-south road. It is here a ferruginous, pebbly conglomerate, 

 presenting a small surface outcrop, overlain by loam. It produces a sandy 

 road, and sandy soils in the adjoining fields for a quarter of a mile next 

 north. Again, at the middle of section 12, in the same township, is an 

 exposure of the same in the road. A perpendicular thickness of about ten 

 feet of bedding seems to be here involved, in a weathered down and half- 

 covered outcrop. This is the highest land between the two creeks. The 

 same rock appears again on the N. E.^ sec. 11, overlying a disintegrating 

 shaly and limy rock like that under the Devonian limestones in Fillmore 

 county, and the same as that seen in the road about a mile and a half north 

 of Grand Meadow. At this place, however, the heavy magnesian beds are 

 not in outcrop. At the S. E. \ sec. 3, in the road running east and west this 

 rusty conglomerate is conspicuous. It is disintegrated so as to make a 

 gravel, as in Fillmore county. 



As already intimated, the age of this conglomerate is not established 

 beyond doubt. The appearances will justify its reference to the Cretaceous, 

 and the occurrence of similar rock in other counties where it is impossible 

 to refer it to the age to which it may belong in Mower and Fillmore coun- 



*See also the reports on Nicollet, Hennepin and Wright counties. Similar conglomerates appear in the Lower 

 Cretaceous in Guthrie county, Iowa. See Qeology of Iowa, 1870, Vol. II., p. 100. 



