CRITERIA FOR AQUEO-GLACIAL SEDIMENTATION. 35 
of coarse material followed by a thin layer of fine material. Above the latter 
would come the coarse component of the summer conditions. 
D. The position of the ice front relative to the area of deposition of the 
banded material is of prime importance in the regulation of width of bands. 
Near the place where the glacial stream emerged from the ice no regular banding 
could be expected, even in deep water, on account of the disturbed and varying 
conditions on the bottom, attendant on such swift streams. At places along 
the ice front where quiet water prevailed, however, regular undisturbed deposi- 
tion should go on with resultant regular banding. Glacial boulders should be 
found in the clays in such locations. On account of the greater amount of 
material near the places of emergence of the glacial streams, the banding should 
be thicker in both components than would be the case if the ice had retreated 
toadistance. As the ice retreated, therefore, the banding should become thinner 
and thinner. Conversely, if the ice were advancing the bands should become 
thicker and thicker. 
The texture of the sediment in the coarse and fine components of the band- 
‘ing should vary to some extent, according to the proximity of currents. The 
nearer the stream of supply from the ice the coarser should be the sediment 
deposited. The finest glacial clays, however, have nearly the same size of 
grains, whether the place of deposition is within a mile of the ice front or many 
miles away. It has been noted above that the farther the ice has retreated from 
a given locality the thinner would be the deposits of any year. It does not 
follow, however, that the sediment of the fine component should be very much 
finer far from the ice than within a small distance of the ice, provided the seasonal 
hypothesis is the correct one, in the interpretation of the coarse and fine compo- 
nents of the banding. In the winter time there would be no currents in the 
deep water, and whether the location was one mile or twenty miles from the 
ice front, only the very fine clay lingering in suspension in the water would 
be deposited. The coarse components of the banding when not due to wind 
action should show a finer texture far from the ice than near. In the absence of 
actual data on the nature of currents of water on the bottom in fairly deep water, 
during times when the supply of water to a basin is abundant, it is impossible 
to determine this question satisfactorily. 
E. Depth of water in the area: of deposition would affect the width of 
regular banding. At the beginning of the winter season the water would con- 
tain a great amount of fine clay particles held in suspension. Such particles 
settle with extreme slowness. The finest particles of all would settle last. 
