From R. Scott Anderson Laboratory of Paleoecology, NAU
(after methodology developed at the University of
Oregon)
Equipment and materials:
Sodium
hexametaphosphate
Small
beakers for soaking samples
Shower
attachment for faucet
Metal
sediment/soil sieves (0.125 mm and 0.250 mm)
Plastic
water bottle with squirt attachment
Petri
dish with grids
Stereomicroscope
Specimen
cups
Procedure:
1.
Sediment sampling
a. Describe core lithology
b. Slice core into contiguous intervals,
usually 1-cm in length.
c. Take a known volume of sediment from
each sample. We generally use 5-cc
of sample, but can use less if there is lots of
charcoal. Charcoal samples
should be taken from each core interval.
d. Soak each subsample in a solution of
ca. 10% sodium hexametaphosphate and
water in a small beaker for 2 to 5 days to
deflocculate the sediment.
2. Sieving
subsamples
a. Gently wash each subsample through a
set of nested sediment sieves. We
generally
use the two sieves Ð 0.125 mm and 0.250 mm Ð for each sample. Make sure that you nest these two
sieves with the 0.250 mm sieve ON THE TOP.
b. Using the rubber hose in the sink,
gently spray the surface of the top sieve for
2-3
minutes or so, just enough time that the entire subsample is washed
through both sieves.
c.
Separate the
sieves. For each size fraction,
gently wash sediment to one side
of each sieve.
Turn the sieve so that its surface is perpendicular to the
counter top and the sediment is at the bottom (closest
to the counter).
Using a plastic squirt bottle, direct a stream of
water at the charcoal and
sediment, and wash it into a specimen cup. Mark the top of the specimen
cup with the sample name and the size fraction that it
represents.
d. Store the samples in a safe place.
3. Counting
charcoal particles:
a. Under a stereomicroscope at 50X or so,
count all charcoal particles. The
grid rows
help keep track of where you are counting.
b. Keep a running tally of the number of
particles for each size class in your laboratory
notebook.
RSA 1 Sept 2000