WINONA COUNTY. 263 



Loess loam.J 



gerolle was being accumulated along the bluffs under the influence of fresh- 

 ets, thus interjecting coarse materials within the strata of the loam, and 

 also that the loam was then continuously being deposited, it would seem at 

 first glance that the country could not have been under a lake of fresh 

 water, since that would have protected the bluffs from the wash of freshet 

 floods. The conclusion would then be plausible, that the loam must have 

 originated from atmospheric agents, such as wind and rain, according to 

 the theory of Richthofen. But granting that such may have been the origin 

 of these intercalated beds of debris, it is also necessary to admit that they 

 may have been accumulated sub aqua, by the same forces, viz., water and 

 wind, just as the rock shingle from an island or beach is carried along by 

 waves and currents, especially by storms, and is distributed on the bottom 

 of the ocean. This of coarse makes a shallow lake, and not a deep one, 

 necessary for the deposit of the loam. 



One hypothesis for the explanation of these beds of coarse materials 

 within the loam in the valleys is perhaps as good as the other, but when 

 taken in connection with the horizontal lamination of the loam, which is 

 nothing like the oblique and cut-off stratification seen in wind-blown sedi- 

 ments, it seems as if the preponderance is in favor of the old theory of the 

 lake-origin of the loess. 



There is still another point which should not be lost sight of in attrib- 

 uting any cause to these coarse beds, viz., there is some reason for attrib- 

 uting an earlier date to the loam of the uplands, than to the loam of the 

 valleys, the latter being in that case only a redeposited wash from the sur- 

 face of the upland loam, during a period of high water in the Mississippi* 

 when the high terrace of that great valley was being deposited. Such a 

 high-water stage would fill the tributary valleys with the necessary shallow 

 lakes for the action of waves, winds and currents on the foot of the bluffs 

 that should rise above it, and at the same time leave the uplands uncovered 

 and liable to the freshets that are necessary for the production of the coarse 

 material within the loam. Thus both materials' (fine, stratified loam and 

 coarse, unstratified gerolle) would be accumulating simultaneously within 

 the valleys. This will explain the phenomena of the section given, and 

 generally of the main valleys of the county, and yet not require anything 



See the report on Houston county. 



