330 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



STRUCTURE OF THE DRIFT. 



The drift of this inner border district, like that forming the moraine, 

 consists largely of typical till, which has a clayey matrix with liberal 

 admixture of pebbles. There are a few gravel knolls and ridges on uplands 

 and also along valleys. Portions of the valley filling present a horizontal 

 bedding in which sandy partings separate till beds or beds of stony clay, 

 but the greater part of the filling, like that on the upland, appears to be 

 typical till without distinct horizontal bedding. 



Wright has given views of two exposures of the till in the valley plain 

 of Fourmile Creek, in Bulletin No. 58, which are here reproduced in PI. 

 XII, A and B. The till represented in the first view is a typical deposit, 

 which is nearly level topped and is banked against the base of a high, rocky 

 bluff that within a mile toward the south rises to 300 feet or more above 

 the creek. The exposure in the second view presents lamination, and in 

 places there is clear evidence of water bedding. The large stones appear 

 to have been dropped by ice into a stream which had only a sluggish cur- 

 rent. The eastern part of Oxford is on a flat-surfaced till plain, along the 

 same creek, whose sui'face stands fully 100 feet below the high rocky bluff 

 on which the rest of the town is situated and nearly 100 feet above the 

 creek bed. 



There is scarcely an exposure of rock along the postglacial valley of 

 Fourmile Creek from the junction of the three forks above Oxford to its 

 mouth. The record of but one well was obtained along this valley. This 

 well is at Brazil Inman's, about 1 mile above the mouth of the creek. It is 

 104 feet deep, and penetrates 90 feet of till, below which it is in sand and 

 gravel. It is reported that "snail shells" and small twigs were pumped out 

 from the sand near the bottom of the well. 



What percentage of drift in the valleys is of the age of the moraine 

 under discussion, and what of the earlier or Illinoian age, can scarcely be 

 determined from the facts at command. The freshness of the exposed por- 

 tion of the drift along Fourmile, Sevenmile, and Indian creeks leads the 

 writer to consider it of the same age as the moraine. The shells and twigs 

 reported above, which were pumped from sands beneatii the till near the 

 mouth of Fourmile Creek, may be of interglacial age, and mark the line 

 between the Wisconsin and the earlier di-ift sheet. The occupancy of Mill 



