THE NEBRASKAN ICE INVASION 229 



Kansan ice sheet. The vegetation here, as in the section at Oelwein, is of a 

 boreal or at least a cold-temperate character. 



In Buchanan County, 12 the Kansan till is filled with fragments of wood, 

 which are particularly abundant in the lower part. This wood has been identi- 

 fied as Larix americana, and is referable to the Aftonian Interglacial Stage. 



In Dubuque County, Calvin found these drift relics and remarks, 13 "almost 

 as characteristic are the battered, frayed, and splintered fragments of trees 

 which are distributed promiscuously throughout a thickness of many feet in 

 the lower part of the drift sheet." In Tama County, Savage 14 records the 

 following section, in Otter Creek Township: 



4. Dark-colored soil (loess) 4 feet 



3. Yellow clay with boulders (Kansan) 95 feet 



2. Blue clay with boulders (Kansan) 260 " 



1 . Bed of sand containing numerous pieces of wood 2-3 feet in length, 1 inch in diame- 

 ter, as well as molluscan shells 12 " 



Hard rock x " 



Another section in Toledo Township 15 showed an Aftonian deposit con- 

 taining wood and vegetable remains between Kansan and Nebraskan drift 

 sheets. The mollusks in the above section have not been identified. From a 

 well 20 feet deep, two miles east of Akron, Plymouth County, 16 the bones of 

 Mammut mirificum (now Rliabdobunus mirificus) have been taken; and at Le 

 Mars (same county) a pelvis was secured which probably belongs to the same 

 species. Possibly the tusk found in Grimes pit, at a depth of 40 ft., may be 

 referred to the same horizon (Hay, p. 389). The foot bones of a Megalonyx 

 were also found in the Jensen well, near Akron. From near Af ton Junction a 

 species of Hipparion 11 (now identified by Hay as Neohipparion gratum) was 

 secured. Near Council Bluffs 17 (Henton Station) Camelops kansanus?, Equus 

 laurentius, E. complicatus, and Elephas columbi have been observed. At 

 Sioux City, Woodbury County, the remains of Megalonyx have been found 18 

 and also Equus major {= complicatus) which Todd 19 records from sand beneath 

 the upper (Kansan) till. Hay 17 also finds Equus laurentius from this locality, 

 and records Mylohyus? temerarius 17 from the Anderson gravel pit, at North 

 Riverside, near Sioux City (pag; 227). In Mills County, in sand below drift, 

 a claw phalange of Megalonyx was observed by Todd. Equus complicatus is 

 also reported from Lyons Township. 



12 Calvin, Geol. Iowa, VIII, pp. 240-241, 1898. 



13 An. Rep. Iowa Geol. Surv., X, pp. 463-470. 

 11 Geol. Surv. Iowa, XIII, p. 234. 



15 Op. tit., pp. 231-232. 



16 Calvin, Bull. Geol. Soc. Amer., XX, pp. 355-356. 



" Bull. Geo!. Soc. Amer., XXII, p. 21 1 , Hay, Iowa Geol. Surv., XXIII, p. 149. 



18 Bull. Geol. Soc. Amer., XXII, p. 215. 



19 Proc. Iowa Acad. Sci., VI, p. 126. 



