Variability of the Earth’s climate - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 99

geological movements, also, where the crust of the earth is broken and the edges
of successive strata are shoved over each other, a species of striation is produced.
Occasionally this deceives the inexperienced or incautious observer. But by due
pains all these resemblances may be detected and eliminated from the problem,
leaving a sucient number of unquestionable phenomena due to true glacial
action.''
Wright (1920) also made the point that deposits left by moving water are
always stratified:
''A second indubitable mark of glacial motion is found in the character of the
deposit left after the retreat of the ice. Ice and water differ so much from each
other in the extent of their fluidity, that there is ordinarily little danger of
confusing the deposits made by them. A simple water deposit is inevitably
stratified. The coarse and fine material cannot be deposited simultaneously in
the same place by water alone. Along the shores of large bodies of water the
deposits of solid material are arranged in successive parallel lines, the material
growing finer and finer as the lines recede from the shore. The force of the waves
is such in shallow water that they move pebbles of considerable size. Indeed,
where the waves strike against the shore itself, vast masses of rock are often
moved by the surf. But, as deeper water is reached, the force of the waves
becomes less and less at the bottom, and so the transported material is
correspondingly fine, until, at the depth of about seventy feet, the force of the
waves is entirely lost; and beyond that line nothing will be deposited but fine
mud, the particles of which are for a long while held in suspension before they
settle.
In the deltas of rivers, also, the sifting power of water may be observed.
Where a mountain-stream first debouches upon a plain, the force of its current is
such as to move large pebbles, or boulders even, two or three feet in diameter.
But, as the current is checked, the particles moved by it become smaller and
smaller until in the head of the bay, or in the broad current of the river which it
enters, only the finest sediment is transported. The difference between the size of
material transported by the same stream when in flood and when at low water is
very great, and is the main agent in producing the familiar phenomena of
stratification. During the time of a flood vast bodies of pebbles, gravel, and sand
are pushed out by the torrent over the head of the bay or delta into which it
pours; while during the lower stages of water only fine material is transported to
the same distance; and this is deposited as a thin film over the previous coarse
deposit. Upon the repetition of the flood another layer of coarser material is
spread over the surface; And so, in successive stages, is built up in 'all the deltas
of our great rivers a series of stratified deposits'. In ordinary circumstances it is
impossible that coarse and fine material should be intermingled in a water deposit
without stratification. Water moving with various degrees of velocity is the most
perfect sieve imaginable; so that a water deposit is of necessity stratified.''