CHAPTER V. 

 THE YARMOUTH SOIL AND WEATHERED ZONE. 



The occurrence of a definite soil and weathered zone between the over- 

 lapping- portions of the Illinoian and Kansan till sheets has been so fully 

 set forth in the discussion of the Illinoian drift border that but few further 

 remarks seem necessary. The name Yarmouth, as above indicated, is from 

 the village in Des Moines County, Iowa, where the evidence of a prolonged 

 interval between the till sheets, now known as Kansan and Illinoian, was 

 first recognized. It remains to be determined whether the occasional 

 instances of soil reported to occur between sheets of till in portions of the 

 Illinoian area east of the limits of the Keewatin ice sheet are to be referred 

 to the Yarmouth interglacial stage. Further light is also necessary to 

 determine whether all instances of buried soils within the region of overlap 

 of Illinoian upon Kansan till are to be referred to the Yarmouth stage. For 

 example, the buried soil in the gas belt west of Letts may prove to be of 

 earlier date than the Yarmouth, though it seems quite probable, as above 

 noted, that it is found in a valley which had been cut in the Kansan drift 

 prior to the Illinoian invasion. 



WEATHERING OF THE BURIED KANSAN DRIFT. 



Among the several evidences of a long interval between the Kansan 

 and Illinoian invasion, that of weathering is the most common and perhaps 

 the most decisive. As shown in the sections given above, there is found to 

 have been a general leaching of the sheet of calcareous Kansan till to a 

 depth of 4 to 6 feet prior to the deposition of the Illinoian sheet of drift. 

 Accompanying the leaching the upper portion of the Kansan drift was 

 weathered to a brown and in places reddish-brown color. The brown color 

 extends much below the limits of the leaching, there being not a few instances 

 in which it extends to a depth of 25 or 30 feet, and it is rarely less than 12 

 to 15 feet. The reddish-brown stain usually extends only to a depth of 2 



119 



