70 IOWA STUDIES IN NATURAL HISTORY 



should be eliminated at once by the statement that what- 

 ever has been the history of the upland surfaces they do 

 constitute cuestas. Martin^ has defined a cuesta as "an up- 

 land with a short, steep descent, or escarpment, on one 

 side, and a long, gentle slope on the other." The three 

 belts containing areas of summit flats answer the definition 

 perfectly, and they are cuestas. The problem remains, 

 however, as to whether their more or less even crests, re- 

 lated as they are to rock structures, could have been de- 

 veloped in a single cycle of erosion. As Martin points out 

 in describing cuestas, "the gentle slope usually corresponds 

 to the inclination or dip of slightly-inclined sedimentary 

 rocks and one resistant layer, as of limestone, may deter- 

 mine the whole dip slope." 



Following this definition and description the character- 

 istics of cuestas which have had a history involving only 

 one erosion cycle are illustrated in Fig. 16. 



Fi^. 16. Diagram illustrating the torograrhy of tl-e nrift'css Area as it s'-r-u'd be 

 if the summit areas are the back slopes of normal cuestas deve'ored in a sing e eye e 

 of erosion. 



There are several points which seem to favor the theory 

 that the upland surfaces included in the Dodgeville plain 

 are merely the tops of cuestas, developed, together with the 

 rest of the topography, in a single cycle of erosion. (1) 

 The belts in which the upland surfaces are considerable are 

 cuestas. (2) The upland surfaces are practically confined 

 in their distribution to the areas of outcrop of resistant 

 rock formations. (3) There are three resistant formations 

 and there are three conspicuous belts containing upland 

 surfaces south of the anticlinal axis. (4) In individual dis- 

 tricts, and in the region as a whole, the upland surfaces 

 have a general southerly slope and the strata dip generally 

 south. However, these arguments are superficial, for their 



1. Martin, Lawrence, Wis. Geol. and Nat'l Hist. Sitn'cij, Bull. 3G, p. 42. 



