Page 43 - Petrology of Sedimentary Rocks

The times and depths of withdrawals for
particles of any size are given by:

Depth in cm.
T .=
l A l d* (mm)
m’n I500
in which T is the time in minutes, d*is the
square of the particle diameter in mm, and
A is a constant which depends upon viscosity
of the water (a function of temperature),
the force of gravitation, and the density of
the particles. The table giving values of A
for various temperatures and particle densi-
ties is given below.

A values

DENSITY

Clays, Amphi-
Temp. Quartz boles

OC 2.65 3.00 3.35

I6 3.23 3.92 4.60
20 3.57 4.33 5.08
24 3.93 4.76 5.60
28 4.30 5.21 6.21
32 4.68 5.67 6.60

For quartz or clay minerals at 24”C,
these times work out as follows:

Depth @ Mm Tirnes of
cm withdrawal

20 4.0 .0625 20 seconds
20 4.5 .044 I m45s rest ir
I m4~
IO 5.0 .03 I
IO 5.5 .022 I 3m28s These
IO 6.0 .O I56 6m58s times
IO 7.0 .0078 28m counted
IO 8.0 .0039 lh5lm from
IO 9.0 .0020 7h24m t the
5 10.0 .00098 I4h50m restirring
5 II.0 .00049 59h20m I
5 12.0 .00024 237h20m
5 13.0 .OOO I2 949h

(If you use Waddell’s sedimentation formula,
multiply all the “A” values by 0.64 and use
this instead).

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