MOWEE COUNTY. 353 



Cretaceous strata -J 



The Cretin-con*. The principal exposures of the Cretaceous are found in 

 the valley of the Cedar river, and in the vicinity of Austin. These less in- 

 durated strata overlie unconformably, with an immense lapse of intervening 

 time not here represented by any rocks, the older rocks of the Silurian. 

 They have been broken up by the glacial forces, and their materials have 

 been forced into the pre-existing cavities and channels of the older strata. 

 They also lie undisturbed in some of these old cavities. Similar apppear- 

 ances have been noted in Iowa by Profs. Hall and Whitney and by W. H. 

 Ban-is.* but in that state they seem not to have been referred to the agency 

 of the Cretaceous ocean. 



With respect to the clay, which is probably the uppermost of the Cre- 

 taceous deposits in the county, it is frequently seen at Austin, and at points 

 below Austin, in the quarries that are opened in the Silurian rocks. A 

 quarry in the left bank of Dobbin's creek, just below the mill of Mr. C- 

 Alderson, opened in the Austin rock, shows the beds everywhere greatly 

 broken. Throughout, the partings and all the interstices are closely filled 

 with this greenish clay. The clay here very rarely has any distinct bed- 

 ding. It varies from green to reddish, or buff', and is accompanied also with 

 considerable clean white sand. These are both lodged in the cavities of 

 the rock in such a manner that they seem to have been jammed into them. 

 They pertain to no particular horizon, and show no definite arrangement. 

 They are disposed everywhere, from the top to the bottom of the bluff, 

 though the sand seems to be more abundant near the bottom. 



At a quarry of Mr. Alderson's, near Austin, the rock was overlain by 

 the following 



Cretaceous clays. 



1. Black sandy loam and soil, 2 to 4 feet. 



2. Band of red and variegated compact clay. - 6 in. to 4 feet. 



3. Yellow ocherous band of clay 6 in. to 4 feet. 



The superposition of these bands of clay is not so regular as indicated 

 by the foregoing section. Occasionally number 3 is broken through, or is 

 wanting, and number 2 lies on the rock, or passes down into its crevices; 

 yet number 3 is generally the first over the rock. They vary in thickness 

 and swell out in shapeless masses, and become very hard when dry. Such 

 hard masses are seen sometimes to embrace bits of angular earthy rock, 



See the second annual report, and the report on Blue Earth county; also, Geology of Iowa, Vol I pp 84 and 130; 

 also, Proceedings of the Davenport Academy of Natural Sciences, Vol. II., p. 264. 



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