82 PLEISTOCENE OF INDIANA AND MICHIGAN. 



At Monrovia most wells obtain water at about 20 feet in sand underlying till of Wisconsin 

 age. A well sunk by David Miller to a depth of 1 18 feet passed mainly through blue till thought 

 to be Ilhnoian. West of Monrovia in the northwest part of Morgan County is a level tract in 

 which wells 10 to 20 feet commonly penetrate a few feet of surface sand and a sheet of till before 

 entering the water-bearing sand. 



At Stilesville, in southwestern Hendricks County, the drift is 120 to 130 feet thick. The 

 schoolhouse well and the public well enter a hard blue till, probably Ilhnoian drift, at about 

 40 feet. 



Near New Maysville, in Putnam County, several wells have passed at about 20 feet through 

 a buried soil which apparently lies between the Wisconsin and Ilhnoian drifts. With the soil 

 are muck and leaves, showing that the pre-Wisconsin surface was swampy. 



OUTWA8H. 



The Wisconsin drift border in Indiana, like that in Illinois, 1 appears to have had remarkably 

 weak outwash. Thin deposits of fine sand occur along the valley of Little Sand Creek and of 

 northern tributaries of Sand Creek which lead away from the Wisconsin border in southern 

 Bartholomew and Jennings counties. These are probably a glacial outwash, though they may 

 be in part a deposit of the streams in later times. But nothing found along the valleys of the 

 large rivers, the East White and White, seems clearly referable to drainage at the maximum 

 limits of the Wisconsin glaciation. Each valley carries a gravel plain, but much of the gravel 

 has been brought from the moraines which cross the streams farther north. These gravel 

 plains not only head well within the Wisconsin drift border, but they occupy valleys that had 

 been cut down in the vicinity of the Wisconsin border below the level of the base of the Wis- 

 consin drift prior to the deposition of this coarse gravelly material. Mill Creek and Walnut 

 Creek and smaller streams that flow away from this Wisconsin drift border show little or no 

 evidence of vigorous discharge down their valleys. 



In explanation of this apparent weakness of discharge on the ice border Chamberlin 2 

 has suggested that at the culmination of the Wisconsin stage of glaciation arid conditions may 

 have prevailed to such an extent as to favor evaporating rather than melting or liquefying of 

 this marginal portion of the ice sheet, and that evaporation gave place to liquefaction as 

 humidity increased. 



INNER BORDER. 



GENERAL FEATURES. 



For a few miles back from the Wisconsin drift border the surface is generally plane or 

 bears only scattered knolls. It shows, however, two undulating strips and two well-defined 

 eskers that seem worthy of mention. These features are somewhat isolated, though one of the 

 eskers terminates in one of the undulating belts. The undulating belts, though probably 

 formed along the margin of the receding ice sheet, are not attended by definite outwash plains 

 or by other confirmative evidence, and their trend is somewhat out of harmony with neigh- 

 boring bowlder belts. Possibly they were formed submarginally while the ice still covered 

 the district outside. 



Ravines which cut down through the Wisconsin drift, as well as borings which pass 

 through it into the older drift, show it to be relatively thin everywhere near the border. Its 

 thickness is generally less than 30 feet and is often but 10 to 20 feet or less. A buried soil 

 underlies it at depths of 20 to 30 feet at a good many points 15 to 20 miles or more inside as 

 well as along or near the border. The underlying older drift attains great thickness along the 

 lines of old valleys, but on the interfluvial tracts is not much thicker than the Wisconsin drift. 

 The above statements are supported by numerous data obtained from well records. 



The greatly preponderating material of the drift of this region is a till, which is commonly 

 compact and clayey rather than loose textured and sandy, and which is consequently only 

 slowly pervious to water. Strips of sand and gravel which head in moraines to the north and 



i Mon. U. S. Geol. Survey, vol. 38, 1899, p. 208. 



2 Remarks made at the Washington meeting of the Geological Society of America, January, 1903. 



