Jan., 1908.] 



An Esker Group South of Dayton. 



239 



eastward. The fanning of the knoll-endings into the vallev 

 where they meet in an even slope is doubtless the result of slump- 

 ing. Davis-^ gives a clear exposition of conditions when bodies 

 of water are dammed by the ice-front, with the consequent 

 phenomena of sand plains built up by esker streams. The Day- 

 ton area, however, shows no evidence of favorable conditions 

 for the holding of ice-front waters, drainage having a perfectly 

 free course toward the south. Streams emerging from the ice 

 would spread out and quickly drain away. In this particular 

 area such an outwash plain if formed would have been destroyed 

 long ago by the erratic wanderings of the Miami. 



Fig. 5 {f. Carney) Kaine area immediately west of esker No. 2. Camera 

 facing north. Barn rests on a long ridge of kanies. 



Altitude of These Deposits. The elevation of the area above the 

 valley is partly due to the base upon which it rests. This is 

 shown particularly in the kame region, the inside slopes of which 

 are much shorter than the slopes facing the valley, a condition 

 explainable by slumping within the area and erosion around it 

 by the Miami as before stated. 



In this connection it may be suggested tliat possibly gradation 

 has greatly modified the original eskers. At the time of ice- 

 withdrawal these forms, particularly if sub-glacial in genesis, 

 must have been left with little or no vegetative protection. It 

 cannot be determined how long a time was required before plant 

 life secured a good foot-hold, but it is reasonable to suppose that 

 the interval was sufficient to permit considerable weathering even 

 on such narrow forms as eskers. With the eskers in question is 

 it not probable that after the constituting material had assumed 

 its natural angle of repose they may have been considerably 

 lowered by gradational processes? Such processes would also 

 reduce the effect of height by partially filling the trough. • • 



21. W. M. Davis, Bull. Geol. Soc. Am., Vol. I, (1S90), pp. 195-203. 



