WISCONSIN DRIFT BORDER. 81 



THICKNESS. 



Average thickness. — In places the border of the Wisconsin drift is reduced to a mere 

 sprinkling of pebbles and bowlders, commingled with the white clay and weathered portion of 

 the Illinoian drift; but commonly it is a sheet 10 to 20 feet thick, the upper 8 or 10 feet of a 

 fresh yellowish brown and the remainder of a yellowish gray or blue-gray. Till forms the 

 greater part of the border of the Wisconsin drift sheet, yet nearly every farm shows sandy or 

 gravelly spots, and many wells that are carried to the bottom of the Wisconsin drift pass 

 through thin beds of sand. 



Sections of wells 1 in the region traversed by the Wisconsin drift border in Indiana show 

 variation in the depth of the glacial deposits but throw little light on the Wisconsin drift as a 

 distinct sheet. Abundant data on this subject may, however, be obtained by examining the 

 bluffs of streams or the sides of excavations. These, as already indicated, show the thickness 

 to be ordinarily but 10 to 20 feet and the bulk of the deposit to be till. 



Well data. — The records of most of the wells along the Wisconsin drift border are not 

 sufficiently definite to fix the line between the Wisconsin and pre-Wisconsin drift. They are, 

 however, of value in showing the total thickness and the variable characteristics of the drift. 



In the head of the reentrant between the Miami and East White River lobes, from the 

 vicinity of Cambridge and Dublin northward, the wells penetrate thick beds of sand and gravel 

 and only minor amounts of till. Southward from these villages the amount of till increases, 

 and in Rush County the border district has only thin beds of sand and gravel between the till 

 sheets. Thus Elrod 2 reports that a well at the planing mill at Glenwood in eastern Rush 

 County penetrated 116 feet of drift, all of which except 24 feet of fine sand from 66 to 90 feet 

 was till. Blue till was entered at 8 feet and continued to the sand, below which there was an 

 indurated blue hardpan, probably Illinoian. At Rushville the wells penetrate 40 to 90 feet of 

 drift, largely blue till, though in some places containing thin beds of sand and gravel. 



Elrod noted the occurrence of a buried soil and peat bed in the vicinity of Milroy in Rush 

 County at a depth of 25 to 30 feet. He gives the following average section for that locality: 3 



Average section of wells at Milroy, Ind. 



Feet. 



Soil 1-2 



Clay, yellow 10 



Clay, blue; replaced in some wells by sand 8-10 



Clay, gray, and hardpan, usually mixed with fragments of chert and pebbles 6-8 



Gravel, sand, or muck, water bearing; two wells yielded fair specimens of peat 3-5 



28-35 

 Wells in Decatur County show no records of especial note, but ravines afford numerous 

 opportunities to compare the Wisconsin drift with the underlying older drift. Copper nuggets 

 have been found along ravines in the vicinity of Milford. It was not definitely settled that 

 they came from the older drift, but it was supposed that they did, as the older drift is known 

 to contain copper in the southeastern counties of Indiana outside the limits of the Wisconsin 

 drift. Should such nuggets be found in the Wisconsin drift of this region they might easily 

 have been derived from the older deposit. 



No well records of especial note were obtained in Shelby County except those in the 

 channels traversing the southwestern part of the county. These show that the gravel is of 

 moderate depth, till being struck not far below the level of the beds of the present streams. 

 The filling of glacial gravel at Edinburg in southeastern Johnson County is shown by the wells 

 to be about 30 to 40 feet. The total depth of drift, as shown by a gas boring, is 115 feet. 



Wells in the vicinity of Morgantown obtain water at. 18 to 20 feet from gravel below the 

 Wisconsin drift, but a gas boring penetrated 175 feet of drift, largely sand and gravel. 



1 See county reports of Indiana Surveys; also Water-Supply Paper U. S. Geol. Survey No. 26, 1S99. 



2 Fourteenth Ann. Kept. Indiana Dept. Geology and Nat. Hist., 1S84, p. 55. 

 s Thirteenth Ann. Rept. Indiana Dept. Geology and Nat. Hist., 1S83, p. 103. 



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