374 GLACIAL GEAVELS OF MAINE. 



have been found in digging wells. The nearest I have found fossils to a 

 large marine delta is about 4 miles.^ 



4. The deltas here described are all found below the elevation of about 

 230 feet, except those situated farthest northwest, which may have a higher 

 elevation. Up to these levels the beaches are distinctly and incontestibly 

 to be found. 



5. This clay covers the whole of the State up to that elevation — that 

 is, all the broader valleys and such places as would not form projecting 

 headlands of the expanded sea. 



6. The sand and gravel portions of adjacent marine deltas are often 

 confluent or nearly so, proving that they were deposited in the same body 

 of water. In York and Cumberland counties there is a succession of 

 practically confluent delta-plains for about 40 miles. 



Marine delta-plains form part of both the osars — the broad osars and 

 the discontinuous osars — and they form the usual termination of the great 

 plains of reticulated kames. The Katahdin system expands into two deltas 

 deposited in the open sea: first, in the level region west and northwest 

 of Deblois ; second, in the valley of Union River in Aurora. It also 

 expands into a delta in Grreenfield, 30 miles farther nortli, but I am some- 

 what in doubt whether the last named is a glacial marine or a lacustrine 

 delta. In like manner most of the longer gravel systems show from one to 

 thi-ee marine deltas at different distances from the coast. These nmst mark 

 either the retreat of the ice northward or an increase of elevation of the 

 sea, or both causes combined. 



One fact regarding the deltas here denominated "glacial marine" 

 deserves special notice. By far the largest of the delta-plams are found 

 between 170 and 250 feet above the present sea level. The high level deltas 

 cover hundreds of square miles. They prove that the time of most active 

 transportation of glacial sediments coincided with the time when the open 

 sea covered all or nearly all the coast region of the State below the contour 

 of 230 feet. They are so extensive and unmistakable in character, and 

 all along the coast have so nearly the same relative development at 

 that contour that they form an important part of the evidence as to the 



' A leaf of sea-lettuce ( Ulva laetuca) found in the upper clays at Le-wistou. The lower layers of 

 the clays are richly fossiliferous at Lewiston. The marine delta was situated not far north and east 

 ~of Lake Auburn. 



