92 GEORGE F. KAY AND J. NEWTON PEARCE 



probably genetically related to it. Very likely it is but a phase of 

 that deposit though differing from it in its plasticity, color, and 

 density." In his report on Appanoose County, Iowa, Dr. Bain 

 describes a loess-silt^ on Kansan drift which he considers to have 

 been deposited later than the drift, and which in character and 

 origin seems much like the white clays of Ohio Valley described by 

 Leverett.^ 



In a geological report on Madison County, Iowa, Dr. H. F. 

 Bain and Dr. J. L. Tilton refer to a dark-colored, impervious, 

 unfossiliferous clay on Kansan drift as the lower of two phases of 

 loess in the county. ^ 



The gumbo of Udden. — Mr. J. A. Udden in a report on the 



geology of Pottawattamie County, Iowa, describes in considerable 



detail the gumbo or red clay associated with drift and makes the 



following statement regarding its origin i^ 



It would be premature at the present time to express any opinion as to 

 the origin of this deposit. Probably it is mostly an old loess, which has been 

 clogged up by interstitial deposition of fine ferruginous material through the 

 agency of the ground water. Perhaps it is in part a fluviatile deposit, made 

 at a stage of semi-stagnant drainage, or possibly it is of varied origin, being 

 in some places a surface wash, or a disintegration product derived from an 

 underlying bowlder clay, and at other places a modified upland loess, or a 

 river silt. 



The Dallas formation of Tilton. — ^Dr. J. L. Tilton gave the name 

 Dallas deposits to gumbo and related materials overlying Kansan 

 drift in southern Iowa. He considered the deposits to have been 

 formed during the closing stages of the Kansan glacial epoch.^ 



The gumbo of Arey.— In a report on the geology of Davis 

 County, Iowa, Professor M. F. Arey states that the gumbo which 

 lies on the Kansan drift is perhaps a water deposit.^ 



' H. F. Bain, "Geology of Appanoose County, Iowa," Iowa GeoL.Surv., Vol. V 

 (1895), pp. 407-8. 



2 Frank Leverett, "On the Significance of the White Clays of the Ohio Region," 

 American Geologist, Vol. X (1892), pp. 18-24. 



3 H. F. Bain and J. L. Tilton, " Geology of Madison County, Iowa," Iowa Geol. 

 Surv., Vol. VII (1896), p. 523. 



4 J. A. Udden, "Geology of Pottawattamie County, Iowa," Iowa Geol. Surv., 

 Vol. XI (1900), p. 258. 



s J. L. Tilton, "A Pleistocene Section from Des Moines South to Allerton," Iowa 

 Acad, of Science, Vol. XX (1913), pp. 218-20. 



* M. F. Arey, "Geology of Davis County," Iowa Geol. Surv., Vol. XX (1909), 

 p. sii. 



