DATA AFFECTING SUBMERGENCE THEORY 241 



Many of the streams now tributary to the Connecticut Eiver were, during 

 the postglacial submergence, independent streams, and their detrital con- 

 tributions to the sealevel deposits must be sought at the theoretic eleva- 

 tion and often outside the Connecticut Yalley proper. 'An inspection of 

 Emerson's maps of the Pleistocene, in his two writings above noted, will 

 show the "high delta sands" and "lake-shore beds" miles back from the 

 river and in lateral valleys now having no essential relation to the present 

 Connecticut Eiver. 



GLACIAL DELTAS 



The most easily recognized proofs of the high-level waters, and prob- 

 ably the most frequent, are the small deltas of unmistakable form and 

 structure left hung up on the valley sides. These have been attributed 

 to glacial waters, local ice-border lakes or pondings in side valleys or re- 

 entrants of the valley wall. Such genesis of some deltas is certainly pos- 

 sible and the theory is legitimate. In some cases the composition or 

 partial content of the delta argues for the immediate presence of the 

 glacier. But ice-border lakes on the sides of the open valley must have 

 been rare and the production of definite deltas very doubtful, for the 

 following reasons : The writers seem to agree that the waning ice in the 

 Connecticut Valley was not strongly lobate, and a lobate or tongue form 

 is the more favorable for such pondings. Moreover, such waters with 

 outlet alongside the ice border are' fluctuating in level and ephemeral. 

 To have steady level, a glacial lake required an outlet over land, and 

 such outlet channel should be found in order to confidently postulate a 

 lateral glacial lake. In lateral valleys with northward down-slope glacial 

 lakes occurred, and Emerson shows such in his maps. Any deltas or other 

 shore phenomena at high level on the sides of the open valley or in south- 

 leading valleys should be attributed to the marine level, and confidently 

 so if the altitude is found to coincide with the theoretic marine plane. 



Some deltas deposited in the sealevel waters may have been built near 

 or even against the ice-front, and such might contain unassorted mate- 

 rials. Doubtless some deposits were made by glacial drainage that poured 

 directly from the ice-front or along the ice border, but such deposits are 

 not likely to have good delta form for the reason that such drainage was 

 shifting and commonly subglacial. 



FEATURES OF THE LOWER LEVELS 



As the land slowly lifted out of the sealevel waters the finer detritus 

 was partially rinsed down the steeper slopes, and with the diminishing 

 breadth and depth of the waters the detrital deposits became broader and 

 more continuous. The conspicuous, extended and clayey plains are in- 

 ferior levels. As examples we may note : at Broad Brook, 13 miles north- 



