230 LIFE OF THE PLEISTOCENE 



In Washington County, a well section disclosed wood and cones of black 

 spruce (Abies nigra = mar iana) at a depth of 115 feet. 20 Five miles east of 

 Iowa City, Johnson County, 21 a peat bed occurs at a depth of 28 feet, which 

 contains grass, wood and twigs, seeds and other plant remains, besides coleop- 

 terous insects. 



In Linn County,' 22 deep wells have indicated the presence of Aftonian 

 Cy deposits beneath Kansan and Iowan tills. A well section in Township 86 

 ' N. R. VI W., 180 feet above the flood plain of the Wapsipinicon River revealed 

 the strata indicated below. 23 



7. Black soil 6 feet 



6. Yellow clay, almost clear grit (Iowan loess) 20 " 



5. Blue clay, pebbly (Iowan drift) 38 " 



4. Clay, yellow, mixed with sand (Yarmouth) 5 " 



3. Blue clay, with a few feet of muck (Kansan) 152 " 



2. Whitish clay (Aftonian) 2 " 



1. Lime rock 1 " 



Height of section 224 " 



A section near Central City, believed to be in an old channel of the Wap- 

 sipinicon River, gave a better showing of Aftonian. 24 



7. Black soil 4 feet 



6. Yellow clay, pebbly (Iowan drift) 15 " 



5. Yellow sand (Yarmouth) 4 " 



4. Blue clay, changeable from hard to soft every few feet (Kansan) 190 ' : 



3. Sand, fine white (Aftonian) 13 ' 



2. Sand, coarse, with wood (Aftonian) 12 ' 



1. Coarse gravel (Aftonian) 3 ' 



Height of section 237 " 



Similar sections have been noted in other parts of the county. 



A very deep section of Pleistocene strata occurs at Stanwood, in an ancient 

 (preglacial) river valley, in Cedar County. 25 This is indicated below: 



9. Yellow clay (Iowan loess) 20 feet 



8. Blue muck, ashen (Kansan loess) 7 ' 



7. Green, bright hard clay 1 ' 



6. Yellow clay (Loveland) 7 ' 



m Bain, Geol. Iowa, V, pp. 153-154. 



21 Webster, Amer. Nat., XXII, pp. 414-415. 



"Norton, Geol. Iowa, IV, pp. 168-184. 



23 Op. cit.,p. 179. 



,M Op. at., p. 175. 



26 Norton, Geol. Iowa, XI, p. 344. 



