Geoscience Reference
In-Depth Information
Fragmentation parameters
Probability of fragmentation (%
of particles affected)
Uniformity of fragmentation
(relative size of fragments)
Intensity of fragmentation
(number of derived particles)
Model
Original
particle
Derived particles
Computer representation of the fragmentation
fragmentation
Toward box
no. 1 (clay)
Toward
box no. 2000
(coarse sand)
Fig. 3.14
Model of fragmentation of skeleton grains.
from a given box, dividing them and sorting the fragments obtained
into the boxes corresponding exactly to their dimensions.
The result of such an operation is followed in an equilateral or
right-angled textural triangle. Let us assume that a collection of particles
all of original size 2 mm (2000 ยต m), thus consisting of coarse sand,
is fragmented. These particles will be divided into fine sands, fine
sands into coarse silts, and so on. The point on the textural triangle
representing the status of division of the collection of particles will be
displaced and will trace what we call a trajectory . According to the value
taken by the parameters listed above (Fig. 3.14), the result will resemble
one of the curves shown in Figure 3.15a. From the sand corner, we are
led to the clay corner after a rather marked detour through the silt
corner. Indeed these types of curves closely resemble the granulodynamic
path of certain real profiles. By granulodynamic path we mean the curve
obtained by representing the horizons of a soil in the textural triangle
by points then connecting them by segments of straight lines and adding
an arrow to indicate the direction of weathering, that is toward the top
of the profile (Fig. 3.15b).
Clay
Granulodynamic path in
the right-angled textural
triangle of a real profile;
comparison with a trajectory
representing a simulated
fragmentation.
Clay
a
b
A
Silt
Sand
Trajectories , in the equilateral textural
triangle, resulting from the simulated
fragmentation of a sand; test of various
hypotheses (cf. the parameters indicated
in Fig. 3.14).
Real
profile
B1
B2
C
Simulation
Sand
Silt
Fig. 3.15
Comparison of trajectories and granulodynamic paths.
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