BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 VOL. 20, PP. 399-408, PLS. 33-37 DECEMBER 24, 1909 



AFTONIAN SANDS AND GEAVELS IN WESTERN IOWA 1 



BY B. SHIMEK 



(Presented by title before the Society December SI, 1908) 



CONTENTS Page 



Introduction 399 



Previously known distribution of Aftonian beds in Iowa 399 



Peat 399 



Sand and gravel 400 



The Aftonian in western Iowa 400 



Previous work in western Iowa 400 



Description of the beds 401 



Gravels containing mammalian fossils 401 



Sands bearing molluscan fossils 402 



Thickness and altitude of beds 403 



Distribution in Harrison and Monona counties 404 



Evidence that the beds are Aftonian 404 



Stratigraphic position 404 



The Aftonian interglacial with mild climate 406 



Tne Aftonian in other counties 407 



Conclusions 407 



Aftonian and Nebraskan — an addendum 408 



Introduction 



The term Aftonian was first applied by Chamberlin 2 to interglacial 

 beds of gravel and peat near Afton Junction, Iowa, under the impression 

 that they were later than the Kansan. The first correct reference of the 

 Aftonian to its place below the Kansan was subsequently made by Cham- 

 berlin 3 after a reexamination of the type locality. 



Previously known Distribution or Aftonian Beds in Iowa 



peat 



Subsequent investigations by members of the staff of the Iowa Geo- 

 logical Survey have shown that the Aftonian is widely distributed in the 

 state. Peat beds belonging to this stage have been reported from Oel- 



1 Received by the Secretary of the Society December 31, 1908. 



2 Geikie : "Great Ice Age," 1894, pp. 773-774 ; Journal of Geology, vol. iii, 1895, p. 271 



3 Journal of Geology, vol. iv, 1896, pp. 873-874. 



XXXV — Bull. Geol. Soc. Am., Vol. 20, 1908 (399) 



