gPPEE CLAYS. 57 



blue to brownish blue; above that it is bluish gray; otherwise, to the unas- 

 sisted eye, the clay appears nearly the same throughout its whole extent. 

 The absence of marine fossils does not prove the exact height of the ocean, 

 for this clay is pi'actically nonfossiliferous almost to the coast, 200 feet below 

 where the sea has stood, according to the evidence both of fossils and raised 

 beaches. This rarely fossiliferous sheet of clay is the basal clay of the 

 river valleys above 230 feet and the upper layer of the marine clay below 

 that elevation. 



Above the clay which forms the lower stratum of the alluvium of the 

 river valleys, we find in the upper portions of these valleys, overlj-ing 

 the basal clay, a stratum of coarse sand, or sand mixed with gravel and 

 cobbles. This extends across the whole of the valley. As we descend the 

 valley we find at a certain point that the coarse matter becomes finer, and 

 soon passes by horizontal transitions into sand, which spreads far and wide 

 and covers both the fossiliferous and nonfossiliferous clays. In general, the 

 slope of the valley above the point of change from coarser to finer sedi- 

 ments is now not very different from the slope below that point. This 

 rather sudden transition of sediments can easily be explained as due to 

 the checking of the current where the rivers flowed into the sea of that 

 time. Tried by this test, the sea may have stood at 400 or more feet above 

 present sea level in both the Androscoggin and Kennebec valleys. This 

 would imply a greater elevation of the sea in the upper parts of these val- 

 leys than is shown by the beaches near their mouths. There is as yet no 

 fossiliferous evidence of such an elevation of the sea in the upper part of 

 these valleys, and, as suggested elsewhere, if we enlarge our ideas of tlie 

 size of the estuaries and lower parts of the rivers at that time, it is possible 

 to interpret the facts as exhibited in the field consistently with the elevation 

 shown by the fossils and raised beaches — about 230 feet. It is certain that 

 in wide valleys or level plains the upper sands begin to spread laterally over 

 the marine clays at not far above 230 feet. In the valley of the Andros- 

 coggin River these upper sands are well exhibited as delta sands deposited 

 by the river in the sea. They extend all the way from a short distance 

 above Lewiston to the sea at Harpswell, and send out a branch southward 

 through Durham and Pownal to Yarmouth. In the valley of the Kennebec 

 the river delta sands end on the south not far from Waterville. 



