ANDROSCOGGm LAKES-PORTLAND SYSTEM. 22i) 



The transition is quite abrupt, and while the plain is a delta, it is uncertain 

 whether it was deposited in the sea or in a glacial lake. The sedimentary 

 clay continues for about a mile south of Grray Village, and no gravel 

 appears above the clay for about that distance. Then in a low north-and- 

 sonth valley between high hills is found a somewhat discontinuous series of 

 broad hummocks and low ridges, which expands in the western part of 

 Cumberland and the northwestern part of Falmouth into a broad marine 

 delta. A tongue of this plain one-fourth of a mile or somewhat less in 

 breadth extends southward along the eastern base of Black Strap Mountain 

 for nearly 3 miles in Falmouth. The transition between this plain and 

 the marine clay is so abrupt at the sides that it must have been deposited 

 between lateral walls of ice. There is a gradual transition to finer sedi- 

 ments toward the south, and this indicates a delta of some kind. The 

 glacial stream either poured into a bay of the sea that extended back into 

 the ice or i]ito a glacial lake. In the case of this and many similar 

 deposits it will require cross sections of the deltas and the marine clays to 

 determine the stratigraphical relations of the coarser and finer sediments. 

 Such sections are not easily made without excavations for that special 

 purpose, since most of the excavations for road gravel, etc., are purposely 

 made within the mass of eligible gravel and not at the place of transition 

 from the sands to the clays. 



Black Strap Mountain (Mount Independence of the Coast Survey) 

 formed part of an island when the sea was expanded. Along the sides of 

 the "mountain" are numbers of beaches, representing a considerable marine 

 erosion of the till, and these gravels have to be distinguished from glacial 

 gravel The marine clays about its base are deep and sometimes hide 

 masses of the glacial gravel. This makes the region a somewhat difficult 

 one to explore. I have not been able with certainty to trace this series 

 south of the long narrow plain above described. 



There is a small delta at the West Cumberland Fair-ground. It is 

 situated about a mile east of the delta just described, but does not appear 

 to be connected with it. This delta-plain is of rounded fan sliape, and on 

 the margins toward the south, southeast, and southwest the transition from 

 the sand to the marine clay is so gradual as to strongly indicate that it was 

 deposited in the open sea by a small glacial stream that probably was not 

 connected with any other stream. 



