56 IOWA STUDIES IN NATURAL HISTORY 



has, however, been disagTeement concerning the number of 

 cycles, and the dates of historical events. Recently, doubt 

 has been expressed that these upland surfaces represent old 

 peneplains, and the belief advanced that all the features 

 of the topography have been formed in a sing^le ei*osional 

 cycled Most of the papers so far published on this sub- 

 ject are the results of work done in small and isolated dis- 

 tricts within the general region. Therefore it is not strange 

 that agreement has not been reached, and that some of the 

 conclusions are incorrect. The writer has seen all of the 

 Driftless Area which lies in Iowa and Illinois and much of 

 that which lies in Wisconsin and Minnesota, and it now 

 seems possible to bring together material from which ac- 

 curate conclusions may be drawn. 



ACKNOWLEDGEMENTS 



The writer wishes to acknowledge, with appreciation, the 

 assistance of several scores of students in the Universities 

 of Iowa and Chicago, who have used the Driftless Area as 

 a field of instruction under his direction in the ten years 

 during which he was actively engaged in teaching and re- 

 search work there. Special mention is made of A. J. Wil- 

 liams, Jesse V. Howell, W. D. Shipton, Urban B. Hughes, 

 Leroy Patton and Paul MacClintock, each of whom has 

 prepared a report on the general geology of some assigned 

 portion of the Driftless area, following detailed field work. 

 Most of these reports have constituted Master's or Doctor's 

 theses. Not all have been published. Mr. Williams and 

 Mr. Howell did their work in the Iowa portion of the 

 region, Mr. Shipton in the Sparta quadrangle of Wisconsin, 

 Mr. Hughes in the Richland Center quadrangle of Wiscon- 

 sin, Mr. Patton chiefly in the southeastern counties of Min- 

 nesota, and Mr. MacClintock along the lower Wisconsin 

 river valley. In all the work special attention was given to 

 stratigraphy and structure and to their relations with 

 physiographic forms. The results have been freely drawn 

 upon in the preparation of Part II of this paper. 



Thanks are also due to R. D. Salisbury, W. C. Alden and 



1. Martin, Lawrence, Wis. Gcol. and Nat'l Hist. Sui'v., Bull. 36, pp. 55-70. 



