242 ERA NK LE VERE TT 



show a dark blue-black till thickly set with fragments of wood. 

 This occurs at a level lower than the rock surface at Denmark 

 and has a striking similarity to exposures in other parts of the 

 state which are suspected to be pre-Kansan in age. 



Exposures at Davenport, Iowa. — The Illinoian till sheet as 

 above noted is known to overlap the Kansan as far north as 

 Davenport, Iowa. There are excellent exposures of both sheets 

 within the limits of that city and also at points a few miles west 

 near Blue Grass. An exposure in Davenport on Eighth st. 

 between Myrtle and Vine was discovered by Professor J. A. 

 Udden and has been visited by Professor Calvin, Mr. Bain, and 

 the writer, each of whom recognizes the presence of both sheets 

 of drift and also the Yarmouth weathered zone. The surface of 

 the Kansan till sheet has the appearance of slight erosion, for it 

 shows a rise of about 15 feet in a distance of 20 or 30 rods. 

 The Illinoian till sheet rests unconformably upon the eroded 

 Kansan, reaching a lower level at the south end of the exposure 

 than at the north. In making the descent along Eighth st. the 

 following series of beds was found : 



Feet. 

 Loess, ---------- 30 



Weathered zone of reddish brown till (Sangamon), 3 



Unleached brown till (Illinoian), - - - - - 15 



Weathered zone of gummy gray clay (Yarmouth), - 3 



Brown till changing to gray color, 12 to 15 feet (Kansan), 30 



Exposures in Adams county, Illinois. — The most southerly 

 exposures of the Yarmouth weathered zone yet observed are in 

 Adams county, Illinois. In a ravine near Woodville in the north- 

 ern part of the county two sheets of brown till appear which are 

 separated by a gray gummy clay. This clay is thoroughly 

 leached, while the till immediately above it is unleached. The 

 latter has a thickness of only 10 or 12 feet. Another exposure 

 was found at a well in process of excavation on a farm eight 

 miles east of Ouincy. This section is similar to that in the 

 ravine except that the Illinoian till sheet has a thickness of 20 

 feet. Another exposure was found north of Payson near the 



