EROSIONAL HISTORY OF DRIFTLESS AREA 81 



bination demonstrates that the surface has been eroded in 

 moi'e than one cycle. 



Objections which might be advanced to the peneplain 

 theory have been expressed by Martini Each objection is 

 now to be considered. 



(1) Doubt is expressed if the various areas of upland 

 surface making up the plain are large enough, flat enough, 

 close enough together, and sufficiently accordant in their 

 levels to wai'rant the conclusion that they are the remnants 

 of a once continuous peneplain. As was brought out in 

 Part I. there is no definite degree of flatness which a sur- 

 face must assume before it can be called a peneplain. Also 

 there are various ways in which such a surface may be 

 made ii-regular in the second cj'cle. It is not believed that 

 the Dodgeville plain was degraded to such extremes that 

 the surface was altogether flat. There were doubtless many 

 gently sloping valley walls as well as vallej' flats. Not all 

 the tributaiy streams far from the main drainage lines had 

 low gradients. And the facts remain that there are some 

 upland surfaces which are essentially flat; that the upland 

 areas are large enough and numerous enough to furnish 

 thousands of acres of farm land which is notably flat ; that 

 the highest recorded slope on the plain is less than 11 feet 

 per mile and the average slope less than 4 feet per mile; 

 and that the Dodgeville plain includes more and larger 

 areas of flat land and is represented by more nearly accord- 

 ant levels than the Kittatinny peneplain of the Appalachian 

 mountains, the Tertiary peneplain of Idaho or the Miocene 

 peneplain of the Sierra Nevadas. 



(2) Martin gives some consideration to the time in- 

 volved in the erosion of the area and concludes that, al- 

 though there has been sufficient time since the late Paleozoic 

 for the formation of a peneplain, there has also been time 

 for the destruction of such a plain. The writer does not 

 see that the time involved furnishes points either in favor 

 of or against the peneplain or cuesta theory. So far as the 

 duration of time is concerned, several peneplains could have 

 been formed and destroyed during the Mesozoic and Ceno- 



1. Martin, Lawrence, Dull. No. ."6, Wis. Gcol. and Xat'l Hist. Surv., pp. 64-68. 



