Institution

cannot always be accepted at face value when low sample.
concentrations, such as those of suspended matter, are used.
The five suspended-matter samples collected directly
on silver filters on shipboard were x-rayed under the same
conditions as the bottom-sediment samples (see Chapter iv)
in order to make mineralogical comparisons with the bottom
sediment and to determine whether the suspended matter
may be a source for sediment on the Greater Antilles Outer
Ridge. These samples were not treated before analysis
becaus e 0 f the mi nute q uan ti ti es coll ected. Howeve r,
results of the SEM studies indicate that the effects of
organi c aggregates and amorphous si 1 i ca on the analyses
should be minimal. Calculations of composition (Table 7.2)
were made using the peaks and weighting factors of
Hathaway (1972a). The calculations were based on the
assumption that the entire suspended-matter sample was
com~osed of layer silicates. While not true in the
strictest sense (i.e. the SEM studies indicate that quartz,
plagioclase, and biogenic tests may constitute up to 15%
of the sample~ the assumption is justified because the
quartz and feldspar peaks are virtually unidentifiable in
the x-ray diffractogram.
Re s u 1 ts
Chlorite and kaolinite constitute about 2 parts in 10
of the suspended matter (Table 7.2), as they do in the
c 2 ~m fraction of the underlying sediment (Table 4.1).
207
)
)