84 IOWA STUDIES IN NATURAL HISTORY 



the Driftless Area, after analysis, seem almost certainly to 

 be remnants of a peneplain uplifted since its formation and 

 now almost entirely destroyed by the rejuvenated streams. 

 And yet demonstration of the multiple cycle theory does not 

 rest on this evidence alone. It remains to be seen whether 

 there are other indications of more than one cycle and 

 whether there is a combination of evidence which actually 

 proves the case. 



Intermediate Plain (the Lancaster 2)lain) 

 At many places in the Driftless Area there are isolated 

 areas and more or less continuous surfaces, sharply set off 

 from the remnants of the Dodgeville plain, but forming 

 divides several hundred feet above drainage. Though 

 similar in most respects to the summit surfaces, these flat- 

 topped but lower divides occupy a position intermediate 

 between the remnants of the Dodgeville plain and the val- 

 ley bottoms. If the tops of these intermediate divides were 

 projected across the valleys and across the areas where 

 remnants of the Dodgeville plain exist, a plain similar to 

 the Dodgeville plain would be formed, having a general 

 altitude approximately 200 feet lower than the Dodgeville 

 plain. This is the more conspicuous of the two upland 

 plains, and is the one about which most has been written. 

 Various names have been applied to this plain by differ- 

 ent writers. It is Hershey's"^ plain No. 1. Grant and Bur- 

 chard- named it the Lancaster Plain. The writer-' called 

 it the Galena Plain in Jo Daviess County, Illinois. In Iowa 

 it has been called the Lower Plain or Plain No. IP. Ship- 

 ton^ called it the Sparta Plain and Hughes'' assigned to it 

 the name Limeridge Plain. The surface is as well developed 

 in the neighborhood of Lancaster, Wisconsin, as anywhere, 

 and therefore the name assigned by Grant and Burchard 

 is retained for this plain. 



1. Hershey, O. H.. Am. GcoL. Vol. 20, jip. 246-268. 



2. Grant. U. S. and Burchard, E. F., Lancaster-Mineral Point Folio, U. S. Geol. 

 Surv., p. 2. 



3. Trowbridae. A. C, Jour. GeoL, Vol. 21, pp. 739-741. 



4. Howell, J. v., lojca Geol. Surv., Vol. 25, pp. 59-60.' 



5. Shipton, W. T>., Geology of the Sparta Quadrangle, unpublished thesis in library 

 of University of Iowa, p. 57. 



6. Hujihes, U. B.. Geology oj the Richland Center Quadrangle, manuscript in prep- 

 aration. 



