THE KANSAN ICE INVASION 251 



these deposits. Similar deposits, referable to the Yarmouth interval, are 

 reported from Jones, 20 Allamakee, 21 and Howard 22 counties. 



McGee in his classic work 23 on the Pleistocene of northeastern Iowa, records 

 the remains of a once luxuriant flora, some of which may be of Yarmouth age. 

 Much of the material, however, is probably of Peorian age. Logs, sticks, 

 branches, twigs, cones, leaves, stems and roots of grasses, and other plant 

 remains are found in peaty soils, usually at the junction of two drift sheets. 

 From this chaotic material have been identified: Junipetus virgmiana, elm, 

 ash, pine, sumach, hickory, oak, walnut, tamarack, and willow. 



From Emmet County, at Wallingford, fossil wood thot to be Picea alba 

 (= canadensis) is reported by Thomas 23a from glacial drift at a depth of 80 feet. 

 This depth would penetrate the Wisconsin drift and reach the Kansan which 

 apparently underlies the Wisconsin in this part of Iowa. It may, therefore, 

 be referred to the Yarmouth interval, tho it might be of later date. 



The horse, Equus complicatus, is reported from near Sandspring, Delaware 

 County; it was lying on a knoll of Niagara limestone. Hay 24 infers that this 

 may be referable to the Yarmouth stage. 



a. Post-Kansan Loess 



The Kansan drift in Iowa is covered pretty generally (tho not uniformly) 

 with a fine, bluish or whitish loess which is highly fossiliferous. This loess 

 extends beneath the Illinoian drift sheet to the east and beneath the Iowan 

 and Wisconsin drift sheets in the northern part of Iowa. Just how far the 

 deposit may extend thruout the adjoining states is not at present known, but 

 it is believed to be of wide distribution. 



In a recent paper, Alden and Leighton 24a question the distinction between 

 the gray and yellow loess, the two being thot to be the result of loess deposition 

 during but one interval, the post-Iowan or Peorian, the yellow color being due 

 to leaching. Considerable data are given by these authors which seem to 

 support such a conclusion. If this condition should prove true of all of the 

 loess deposits beyond the Wisconsin area, many of the records of fossils herein 

 referred to Yarmouth and Sangamon time would have to be transferred to 

 Peorian time. This conclusion would lead to the recognition of a distinct period 

 during which the loess was deposited, as contended by many early geologists. 



20 Calvin, Geol. Iowa, V, pp. 65-66. 



21 On, Proc. Iowa Acad. Sci., XIV, p. 232. 



22 Calvin, Geol. Iowa, XII, p. 63. 



55 An. Rep. U. S. Geol. Surv., XI, pp. 487, 489. 

 aa Proc. Iowa Acad. Sci., XXIV, pp. 454-455. 

 * Science, N. S., XXX, p. 491. 



243 Iowa Geol. Surv., 26 Ann. Rept., pp. 49-212, 1917; Leighton, Proc. Iowa Acad. Sci., 

 pp. 87-92, 1917. 



