240 H. L. FAIRCHILD PLEISTOCENE MARINE SUBMERGENCE 



correlation along considerable distances of shoreline can the true summit 

 plane be confidently predicated. 



In this glaciated area there is, fortiinately, another class of phenomena 

 which is positive as marking the static water summit, even in single occur- 

 rence, namely, the channels and deltas of glacial drainage. The ice- 

 border drainage was ephemeral and it dropped its detritus in the waters 

 that were laving the ice-front and which were then at their maximum 

 altitude. Glacial stream channels and the sand and gravel plains which 

 can be correlated with the debouchure of glacial streams give the approxi- 

 mate marine plane. The writer has not sought these features on the 

 sides of the Connecticut Yalle}^ but they must certainly occur there 

 abundantly. In the Hudson-Champlain Valley they have afforded posi- 

 tive data. 



Naturally the summit-plane phenomena in the broader sections of the 

 valley are relatively weak and inconspicuous, and it is not surprising that 

 in the lower stretch of the Connecticut Valley they have been overlooked. 

 They must be sought with some idea of the proper altitude. 



There are several reasons for the weakness of the summit features. 

 The sealevel waters soon fell away from their summit plane, due to the 

 rising of the land. Of the rate of land uplift we have no idea, but it wa,s 

 doubtless in progress as the ice-sheet was waning. The amount of de- 

 tritus in the grasp of the earliest water was little more than that contrib- 

 uted by streams and glacial outwash. Time was not allowed for the 

 cutting of cliffs and building of bars, except in the most favorable locali- 

 ties. At lower stands of the water detritus was accumulated by the rins- 

 ing down of the upper slopes. 



In the lower part of the Connecticut Valley, with great width and 

 irregular topography of the walls, the shore phenomena are detached and 

 usually weak and inconspicuous. N'aturally they would not be associated 

 in origin or correlated in their altitudes without study directed to that 

 end. A wrong philosophy has prevented the recognition of these scattered 

 features as the products of one high-level water body. 



In the New Hampshire section of the valley the deltas of streams, either 

 land or glacial drainage, are the common features which mark the summit 

 water-level. In the Massachusetts- Connecticut section the stream-built 

 sand plains are not evident, as the smaller ones with good form lie far 

 back on the slopes, while the heavier deposits of the larger streams have 

 been spread out as indefinite plains or left as alluvial flats in the lateral 

 or tributary valleys. 



It should be understand that the marine waters flooded all the valleys 

 of New England to a height correlating* with the plane in the Connecticut 

 Valley, and similar evidence of the standing water will be found in them. 



