REPORT OF THE DIRECTOR I919 57 



Outwash deposits. While vast quantities of the glacial debris 

 brought forward by the Onondaga valley lobe were deposited in the 

 moraine, as the vast bulk of this testifies, still more material was 

 probably carried forward and southward by the waters released at 

 the melting end of the ice and those which flowed along its lateral 

 margins ; for all the valley to the south of the morainic front is deeply 

 filled with stream-sorted gravels, sands and clays, extending up to 

 the levels of the moraine base at its south front and sloping thence 

 gently southward for many miles. Thus was formed a vast outwash 

 plain and a valley train that follows the course of the Tioughnioga 

 river for many miles. 



These deposits were formed by streams overloaded with sediment 

 and during the same period that the moraine was being built up. 

 On leaving the steeper slopes of the morainic front the velocity of 

 such streams was at once appreciably diminished and they could not 

 carry along all the detritus with which they were burdened. Accord- 

 ingly, the coarsest materials, boulders and pebbles, were deposited 

 first, and as the streams spread over their own accumulations, their 

 flow was progressively less deep and more feeble so that successively 

 finer deposits were laid down southward. Again, as their deposits 

 built up their own beds and made these higher than the adjacent areas 

 the streams were constantly shifting their channels to the lower points 

 and building up these areas in turn. Thus eventually there was devel- 

 oped the wide, level plain illustrated by plate 14. 



It must not be conceived that this outwash deposit was necessarily 

 all built up from streams issuing from the ice immediately at the 

 points where the morainic front is now seen. This morainic mass 

 probably continues under the outwash for considerable distances" 

 southward and may indeed be made up of a number of ridges mark- 

 ing earlier halts in this section, as the visible mass marks the last 

 stand. These possible and probable earlier corrugations of morainic 

 material are, however, now all veneered over and buried under out- 

 wash. They must of course have been lower in elevation than the 

 visible morainic mass at Tully, else they could not have been buried 

 completely. But during the existence of each halt an apron of out- 

 wash was deposited along the moraine front, and as a succeeding, 

 more northerly ridge was built up its outwash in turn filled in behind 

 and built up over the deposits of both morainic and outwash material 

 made previously. 



Pitted plain lakes. Such composite and progressive develop- 

 ment of the outwash deposits gives the clue to the origin of the 

 singularly interesting and beautiful lakes, the Tully group and Little 



