316 H. p. LITTLE PLEISTOCENE GEOLOGY OF WATERVILLE^, MAINE 



tendency of these marine sands to form dunes in many parts of the State 

 has long been known, Stone calling attention to it in 1886/ It seems 

 likely that when the sand was first exposed by the relative rising of the 

 land it blew into dunes. In plate 16, figure 2, is shown a section in which 

 a very duiielike structure can he observed, which may date from this 

 period. The irregularity of occurrence of the sand may be accounted 

 for by its redistribution through geolian action or by the formation of 

 sand-bars in a rejuvenated area. 



THE YOUNGER GRAVELS 



At times the marine clays or sands are overlain by gravels varying from 

 a few inches to five feet or more in thickness. No good exposures of these 

 were found except at locality 6, illustrated in plate 17, figure 1. They 

 seem to be somewhat dirtier than the lower gravels; otherwise they are 

 very similar. 



Two interpretations seem to me to be possible. One is that they mark 

 a new advance of the ice, such as has been supposed by Clapp and others ; 

 the other possibility is that at the close of the marine epoch the tops 

 of the eskers were brought above water by rising of the land, and that 

 the esker gravels were cut into by the waves and spread out along the 

 shore on top of the clay and sand. This view is strengthened by the 

 fact that in many cases, if *iot in all, the gravels occur on the clays only 

 in the immediate neighborhood of the axis of the esker and are usually 

 lacking on the more level stretches, where the glacial deposits have been 

 more deeply covered by the clay. The frequent mixture of more or less 

 clay with the gravels might be expected under either interpretation. The 

 gravelly nature of the fossiliferous sands at the City Gravel Pit agrees 

 well with the theory of wave erosion as the agency depositing the gravel. 

 This theory is also simpler, as we shall see in the following paragraph 

 that the land must have been rising, relatively, at about this time. In 

 some cases a third and very simple interpretation seems probable. In 

 the railroad cut above Benton the marine clays on one side of the cut 

 seem to be overlain by gravel. On the other side of the cut there is no 

 clay and the gravels rest directly on the slate. My idea is that in this 

 case and in many similar cases glacial gravel which rested on ledge at a 

 level higher than that of the marine clays has by gradual creep worked 

 down the slopes of the ledge and overridden the clays; thus a deposit 

 apparently older than the clays overlies them. This is borne out by the 

 fact that the gravels do not seem to occur on the flats below. To my 



7 Am. Jour. Sci., vol. 31, p. 133. 



