106 IOWA ACADEMY OF SCIENCES. 



to the driftwood horizon of the elevator well. But there 

 appears also a driftwood bed at 199 feet below the surface, to 

 which the writer cannot as yet give credence. The drift sec- 

 tion is also thicker here than at Lamoni, as the bottom was not 

 reached at 221 feet, whereas at Lamoni the country rock was 

 reached at 200 feet. 



A small tributary of Grand river, known locally as Potter's 

 creek, running east through Burrell township, passes from 

 its source rapidly down through the drift and reaches the upper 

 surface of the Carboniferous rock, near the eastern part of sec- 

 tion 30, Twp. 68 N., R. 26 W., Burrell township, in the imme- 

 diate vicinity of Krucker's quarry. At this point the creek 

 makes a sharp angle and rock is exposed for a distance of 100 

 feet near the water edge. The entire surface exposed is glaci- 

 ated. The striae in general are S; 1*^ W. , varying to as much as 

 S. 4° or 5° W. A few are S. 5° E., or even greater. All these 

 bearings are with reference to the magnetic meridian. The ac- 

 comj^anying plate (Plate viii) well illustrates their character. 

 The bluff rises abruptly from the glaciated rock to a height of 

 forty-five feet. The lower six feet as exposed is blue clay; the 

 upper thirty-nine feet is yellowish clay filled with pebbles and 

 lime. The hill slopes back from the summit of the bluff in a 

 short distance to a height of 110 feet above the strise, while the 

 distance passed down from the well at Lamoni to the glaciated 

 rock is 245 feet. 



The drift from the surface to the forest bed, eighty-five feet 

 in depth, is referred to the Kansan stage. The buried forest 

 bed is an interglacial stage now referred to the Aftonian. 

 During this stage the climate was mild and coniferous forests 

 were in all probability abundant, but went down before the 

 irresistible advance of the Kansan glaciers, and beca me covered 

 with a heavy mantle of drift debris. The drift material below 

 the forest bed is at present referred to the pre-Kansan or 

 Albertan stage. Should the finding of a second horizon of 

 driftwood, as indicated by S. B. Hartshorn's well, be confirmed 

 this stage may be divided. Further developments will be 

 awaited with interest. The glacial stria3 on bed rock may be 

 referred to the advance of the glaciers as they bore southward. 

 The striaB were subsequeatly covered by glacial debris to be 

 exposed by erosion since the final invasion. 



