BANDED CLAYS. 27 
parts close by, at the same time. When a glacial stream emerges from the ice, 
even in deep water, the layers deposited are coarser and thicker than farther 
from the ice front, where the speed has diminished and conditions have become 
possible for the recording of seasonal units. The yearly deposit in the case 
of a glacial stream emerging into deep water would have a history somewhat 
as follows: — Commencing in the spring near the place of emergence of the 
glacial stream, gravel or sand would be found, a little farther away finer sand. 
The layer of this finer sand would grow progressively thinner and the texture 
would become finer as the relatively slow stream became more distant from 
the ice. Finally in quiet water nothing but silt and clay would be laid down, 
either at a long distance from the ice or nearer the ice but off to one side in 
quiet embayments. In the winter time the glacial stream, except in times of 
thaws or rains, would be almost extinct. Clay might even be deposited at the 
very place of emergence of the stream. Any clay thus deposited, however, 
would be promptly washed away in the torrents of the succeeding spring and 
summer. In quiet waters a slow settling of the fine clay would be in progress, 
interrupted perhaps by slightly coarser sediment brought down by the water of 
a thaw. The annual deposit, therefore, would have the shape of a wedge with 
the thick part near the ice and the thin part farthest away. In deep water this 
wedge would spread out as a fan having a spread of nearly 180°. If the glacial 
stream was on the west side of the valley, sands or perhaps gravels would be 
deposited there, while on the east side of the valley nothing but silts and clays, 
provided of course quiet water conditions prevailed in the east. The western 
deposit would be built up perhaps fifty times as much in a year as the clay de- 
posits on the east. On account of erosion and redeposition near the ice, in the 
neighborhood of the place where the stream emerged, a small amount only of 
the fine material deposited would remain. Some such conditions must have pre- 
vailed in the lake valley of this region, during the retreatal episode of the glaciers 
of the time. In speaking of the continuity of the clay layers, therefore, it 
should be remembered that toward the glacial stream they become coarser, 
merging into sand or gravel at the ice, and that away from the currents or where 
the currents died out, they would pass into thin units. 
Woodworth, 1905, has given a good description of the nature of deposition 
in the case of a single stream emerging from the ice into shallow water, or on to a 
proglacial delta. He writes: 
“For illustration the simplest case will be taken, that of a glacier discharging its drainage 
by a single stream into the head of a bay or lake on the border of which it has already built a 
