THE CLYDE SEKIES OF SOILS. 17 



While there are very extensive deposits of unquestioned lake sedi- 

 ments within the area of the glacial Lake Saginaw, there are also 

 numerous large areas where the glacial till remains uncovered by 

 glacial lake materials or is so thinly covered that only portions of 

 the present surface, may be confidently ascribed to glacial lake depo- 

 sition. Some of these deposits, because of the large amount of par- 

 tially decayed organic matter in the surface soil and because of their 

 evident previously swampy condition, are more closely related to 

 the soils of the Clyde series than to any other group. Others, not 

 so marked, belong to other soil series. The glacial outwash ma- 

 terials and many of the beach line deposits do not contain sufficient 

 organic matter to give them the characteristic dark color of the 

 Clyde soils. 



Because extensive water-laid glacial moraines are closely asso- 

 ciated with and partly covered by the glacial lake deposits some 

 members of the Clyde series are found to be gravelly or stony in 

 the Saginaw Lake area. 



In general the surface of the Lake Saginaw area is undulating to 

 gently rolling, although considerable areas, extending northeast 

 from Saginaw along the south shore of Saginaw Bay, are very flat 

 and unrelieved. In consequence, a considerable proportion of this 

 glacial lake area is fairly well drained through the deep-cut channels 

 of the larger streams. Other portions, because of level topography 

 and lack of natural stream ways, have remained swampy until 

 recent years. 



Another glacial lake area of limited extent was formed in south- 

 western Michigan, northern Indiana, northeastern Illinois, and 

 southeastern Wisconsin around the southern end of Lake Michigan. 

 This was known as the glacial Lake Chicago. The majority of the 

 deposits within this area do not form soils which are included in the 

 Clyde series. However, in a narrow belt extending along the west- 

 ern shore of Lake Michigan from the vicinity of Racine, Wis., 

 nearly to Chicago, 111., the soils of the Clyde series occupy the greater 

 proportion of the old glacial lake bed. In this area the soils of the 

 Clyde series are found from the shore line of Lake Michigan to alti- 

 tudes of 60 feet above its present level, at which elevation the shore 

 line of the ancient glacial lake stood. This belt of territory ranges 

 from 2 to 5 miles in width. The highest land within it frequently 

 lies near to the present lake shore, declining gently inland for a 

 distance of 1 or 2 miles and then rising rather sharply to the old 

 shore line. At the higher elevations more sandy soils are found, 

 while in the depression the soils of the Clyde series prevail. 

 55812°— Bull. 141—14 3 



