UPPER KENNEBEC VALLEY. 185 



The glacial gravels in Mercer, Norridgewock, Smithfield, Rome, and 

 Belgrade are found in a region diversified by numerous quite high hills, 

 many of them granite knobs. Between these hills are several valleys, 

 forming very low passes from the valley of the Sandy River south and 

 southeast. The courses of the glacial rivers were over a gently rolling 

 surface. 



The length of the series from Mercer to Belgrade is about 10 miles. 



LATE GLACIAL HISTOHY OF THE UPPER KENNEBEC VALLEY. 



When we compare all the facts regarding the Kennebec Valley with 

 those elsewhere recorded regarding the neighboring valleys situated at 

 about the same distance from the sea, viz, the East Branch of the Penob- 

 scot, the Pleasant River, the upper Piscataquis, Dexter, and Main streams, 

 the upper Sebasticook, Carrabassett, and Sandy River valleys, we seem to 

 have ground for the following interpretation of the facts: 



The earlier glacial streams of the upper Kennebec Valley left no sedi- 

 ments (that I have discovered), or they have been buried out of sight. The 

 osar river that flowed from Norridgewock southward dates from a late 

 period, when the ice had already melted so far north that this river flowed 

 into the sea in the northwestern part of Augusta. The northern tributaries 

 of this river must have drained the upper Kennebec Valley, but it is as yet 

 uncertain whether they deposited any gravels during the time in which the 

 river continued to flow south of Norridgewock. The flow of this glacial 

 river south of that place was presently stopped by the retreat of the ice 

 and the advance of the sea up the Kennebec Valley to near Madison 

 Bridge, north of Norridgewock. The Anson-Madison osar probably dates 

 from about the time the sea advanced to Norridgewock. About this time 

 the upper Kennebec osar river began to deposit gravels in that part of its 

 channel lying north of Solon. Later the ice over the bottom of the valley 

 had all melted as far north as Embden or Solon. By this time the osar 

 channel extending nearly from The Forks to Solon had broadened to an 

 osar-plain channel, with reticulations and outliers in various parts of the 

 valley, and the mighty glacial river that poured south from Bingham and 

 Solon formed a frontal plain of gravel and sand which extended a few miles 

 southward and then was continued to the sea as a frontal plain of clay (the 

 underclay of the valley drift of this part of the valley). The character of 



