34 Kansas Academy of Science. 



The culminations of ice advances have been named from the 

 states in which their deposits have been most prominent or 

 most satisfactorily studied. Each ice sheet, or spread of the 

 ice, left a sheet of unstratified clays, sand and bowlders, called 

 'till," and sometimes marginal moraines and other deposits. 

 The stages recognized, in order of time, are : 



1. Nebraskan, Jersey an, or Albertan. 



2. Kansan. 



3. Illinoisan or lowan. 



4. Wisconsin, with minor subdivisions. 



In the recessional stages, alternating with these, were laid 

 down various water-laid gravels and clays, with peat beds and 

 other organic deposits. 



It should be remembered that similar deposits were form- 

 ing more or less beyond the reach of the ice throughout all Ple- 

 istocene time. 



SIGNIFICANT FACTS. 



Topography. The regioii discussed is a plain about a thou- 

 sand feet in altitude along the Missouri river on the east, and 

 rising to 1,400 to 1,500 feet along the Big Blue. The bedrock 

 consists of alternating shales and limestones of the Pennsyl- 

 vanian on the east, with other strata of the Permian and Cre- 

 taceous showing in patches along the western margin. 



As the prevalent dip of the strata is uniformly of a few de- 

 grees to the northwest, the rise of the general upland surface 

 is by a succession of low, broad, gigantic steps, which have be- 

 come more or less obscured by erosion and the mantle of drift 

 which is thrown over them. The larger streams have cut down 

 valleys 250 to 400 feet deep, and there are few square miles of 

 the upland which are not traversed by watercourses. No ba- 

 sins or lakes occur except on the flood plains of the Missouri 

 and Kansas rivers. 



Limit of the Drift. The southwestern limit of drift bowl- 

 ders and pebbles corresponds approximately to the Big Blue 

 river on the w^est and of Kansas river on the south, or, more 

 accurately, the line enters from Nebraska a few miles west of 

 the Little Blue at an altitude of about 1,400 feet. It runs about 

 that level, following the general contour southward, first a little 

 west of Washington, thence southeast to the Big Blue, three or 

 four miles south of Irving; thence it follows the west side of 

 the Big Blue, declining in altitude until it reaches the vicinity 



