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The less than 2 ~m (lutite) fraction of all suspended<br />

matter samples taken over the Greater Antilles Outer Ridgè<br />

is composed almost entirely of clay-mineral platelets.<br />

Fel dspar, quartz, and fragments of cal careous nannopl ankton<br />

and biogenous silica constitute less than 5 percent of<br />

this fraction.<br />

In the silt fraction (2-62 ~m) about 30-50 percent of<br />

the sample is layer silicates. Kaolinite is infrequently<br />

re cog n i zed as f rag men t s 0 f hex ago n alp 1 ate s, but the 0 the r<br />

clay minerals cannot be differentiated. Quartz and<br />

plagioclase feldspar are common, constituting 30 percent<br />

of the sample in some instances. The calcareous nanno-<br />

plankton are mostly Gephyrocapsa oceanica and Emiliania<br />

huxleyi, and their abundance is quite variable but may<br />

range up to 10 percent by area. torami n i fe raare very<br />

rarely observed.<br />

Samples taken from V~ma Gap have consistently less<br />

biogenous material and less total suspended matter than<br />

those taken over the Greater Anti lles Outer Ri dge~ and<br />

fl occul ated aggregates appear more commonly.<br />

The bottom sedi meht exami ned wi th the SEM is vi sually<br />

similar in composition to that of the suspended matter.<br />

However, the bottom material appears to contain a larger<br />

p ro p 0 r t ion 0 f mat e ria 1 fin e r t h a nab 0 u to. 4 ~ m (F i g. 7. 4) .<br />

199<br />

It is enti rely possible that a substantial amount of suspended<br />

matter smaller than 0.4 ~m was not trapped on the filters,<br />

,<br />

j<br />

. \ )

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