THE KANSAN ICE INVASION 247 



species, however, are terrestrial. The deposits are of three kinds: (1) sands 

 and gravels, (2) muck and old soils, and (3) loess or aeolian sands. The latter 

 is widespread over Iowa and portions of the adjoining states and contains an 

 abundant and varied fauna. To the above may be added the 'Gumbo' or 

 Loveland formation, which, however, is never fossiliferous in the typical 

 deposit. This is a heavy clay and is believed to have "been formed during 

 the melting of the Kansan ice when silt was carried into ice-bound basins, these 

 being located at first on the higher ridges where the thinner ice was the first 

 to melt, and when the ice finally disappeared these masses of silt, often lens- 

 shaped, were spread upon the underlying Kansan drift." 3 



The Loveland has been called loess by many geologists, and its silty charac- 

 ter has been the cause of much of the controversy as to whether the loess was 

 water laid or wind laid. Another deposit formed at a little later stage is the 

 Buchanan gravels, which are widespread in Iowa and other states. Chrono- 

 logically the post-Kansan deposits stand as follows, reading from the lower 

 stratum upward: 



V. Post-Kansan loess 

 IV. Yarmouth soil horizon 

 III. Buchanan gravels 



II. Loveland silt 



I. Kansan drift 



I. THE YARMOUTH SOIL AND WEATHERED ZONE 



The name Yarmouth was given by Leverett 4 to a soil and weathered zone 

 which lies between the overlapping portions of the Kansan and Illinoian drift 

 sheets in eastern Iowa. Old soils and weathered zones occur in parts of Iowa, 

 Illinois, and other states which are believed to be referable to this stage. A 

 typical section, from a well near Yarmouth, Des Moines County, Iowa, show- 

 ing the position of the interglacial deposits, is given below. 5 



7. Soil and loam (Iowan loess) 4 feet 



6. Brownish yellow till (Illinoian) 20 



5. Gray till (Illinoian) 10 



4. Peat bed with twigs and bones (Yarmouth) 15 



3. Gray or ashy sandy clay, containing wood (Yarmouth) 12 



2. Fine sand (Yarmouth) 16 



1. Yellow sandy till with few pebbles (Kansan) 33 



Height of Section 110 " 



3 Shimek, Geol. Iowa, XX, p. 373. See also Kay, Science, N.S., XLIV, p. 637, 1916, for 

 the term "Gumbotill." 



'Illinois Glacial Lobe, p. 119; Proc. Iowa Acad. Sci., V, pp. 81-86. 

 'Leverett, Proc. Iowa Acad. Sci., V, p. 82; 111. Glacial Lobe, p. 42. 



