CHAPTER V. 

 THE OLDEST DRIFT (KANSAN OR PRE-KANSAN). 



GEJiHERAIi STATEBIENT. 



It was noted by Lewis and Wright, while tracing the drift border 

 across Pennsylvania, that a deposit of drift is present in northwestern Penn- 

 sylvania outside the bulky moraine that they were tracing, a moraine which 

 has proved to be of Wisconsin age. They called this outlying drift a 

 "fringe," and supposed it to be a dependency of the moraine.^ It was also 

 noted by Wright that in eastern Ohio there is an outlying sheet of drift, 

 and this, too, was called a fringe.^ This peculiarity of the drift margin 

 in eastern Ohio had previously been noted by Chamberlin, who raised 

 the question whether the border drift was contemporaneous with or older 

 than the moraine.^ A few years later he investigated the outlying drift of 

 western Pennsylvania and reached the conclusion that it is much older 

 than the moraine "back of it.* The writer's studies have served to bring 

 into clearer recognition the evidence that the outlying drift of western 

 Pennsylvania is far older than the Wisconsin drift. The extent or limits 

 of this drift sheet having been considered in the preceding chapter, we may 

 pass at once to the description of the deposit. 



DESCBIPTIOIS" OF THE DRIFT. 



This old drift generally contains a large number of waterworn peb- 

 bles, with which so little clay is found that well drillers commonly call the 

 deposit gravel. The bedding, however, is very indistinct and the assorting 

 imperfect, so that it seems appropriate to call it a very stony till rather than 



1 Second Geol. Survey Pennsylvania, Report Z, 1884, pp. 45, 170, 171, 177, 179-181, 186, 195, 200-202. 

 ^Op. cit., pp. 206-207; see also Glacial Boundary in Ohio, p. 35. 



2 Am. Jour. Sci., 3d series. Vol. XXIV, 1882, p. 96. 



*Bull. V. S. Geol. Survey No. 58, 1890, pp. 14-15; see also Am. Jour. Sci., 3d series. Vol. XL VII, 

 1894, pp. 272-273. 



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