TRANSPORTATION OF DEBRIS BY ICEBERGS 
O. D. VON ENGELN 
Geological Department, Physiography Laboratory, Cornell University 
Introduction.—On the east valley side of the southern end of the 
Cayuga Lake Valley, just to the north of Ithaca, New York, occur 
considerable areas of lake-clay deposits laid down when the waters 
of the lake were ponded to higher levels by the ice barrier of the 
retreating front of the last advance of the continental ice sheet. 
These lake-clay deposits are especially well developed in the zones 
marginal to the outer fronts of the higher-level deltas of streams 
tributary to the Cayuga Valley, and undoubtedly represent, in 
‘such cases, the extension of the bottom-set beds of the delta accumu- 
lations. The particular occurrence to which reference is made in 
this article is found at a level of 840 feet to the south and west of the 
top of a notable delta deposit of Fall Creek, having an average 
elevation of 930 feet (the block diagram, Fig. 1, illustrates the 
geography of the occurrence). Thus the clay may be assumed to 
have been laid down in water having a depth of go feet and removed 
from the nearest point of the steep front of the delta deposit by a 
little less than one-fourth mile. At the time when the delta and 
clay deposits were made the ice barrier must still have existed: 
within the confines of the Cayuga Lake Valley, for the level of the 
delta top indicates that its building must have been coincident with 
the outflow of the lake waters across the north-south divide between 
Cayuga and Seneca Lake valleys, and the overflow of their com- 
bined waters was at a present elevation of goo feet from the south 
end of the Seneca Lake Valley into the Chemung River and thus 
into the Susquehanna. On the other hand, it is unlikely that the 
ice barrier was immediately adjacent to the delta and lake-clay 
deposits, for the nearest point of the north-south divide with a low 
enough elevation to permit of a flow of water from the one lake 
valley to the other is found approximately 15 miles to the north 
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