Geology Reference
In-Depth Information
glaciers, before it is deposited and gradually buried and transformed
into rock by diagenetic or lithi
cation processes, as introduced in
Chapter 1
and discussed further in
Chapter 5.
Some weathering pro-
ducts are carried in solution to be deposited directly on the Earth
'
s
fluids to be
deposited as cements in the sediment pile as it is self-compacted.
During transport, detritus is sorted by size and density, largely in
response to the velocity of water
surface, transformed into animal shells or carried by
flow or wind. Sediment deposited
close to its erosion source may have a wide range of grain sizes, as
illustrated in
Figure 3.10;
sediments transported by water or wind tend
to be winnowed to a limited range of grain sizes and are then termed
well-sorted (
Figure 3.11);
the same material would be called poorly-
graded by an earthworks engineer
-
he looks for soils in embankments
to have a wide range of sizes so that a dense degree of compaction can
be achieved. Grains are also abraded and rounded as they are blown by
the wind especially and this is an important engineering characteristic.
Angular sand has an internal friction angle that may be 10 degrees
higher than rounded sand.
