Institution

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GENERAL LITHOLOGY
CHAPTER iv
THE SEDIMENTS
Sedi ments on the Greater Anti 11 es Outer Ri dge typi cally
consist of texturally homogeneous, terrigenous, abyssal brown,
gray, and reddish lutites which exhibit little or no strati-
fi cati on, al though contacts betw~en zones of di fferent color
can be quite distinct (Fig. 4.1). Distinct layers of coarser
sediment are rare; where present, these normally thin layers
contain relatively high concentrations of carbonate, ash
manganese mi cronodul es. Carboriate is enri ched in di screte
zones, but it is seldom greater than 30% of the total sedi-
ment. Burrow mottling by benthic organisms is very common
throughout
the cores and is especi ally noti ceabl e at the
base of the carbonate-enri ched zones, where carbonate has
been reworked into the adj acent, barren 1 uti te. Manganese
micronodules, rarely exceeding 1-2 mm in size, normally
are scattered in the lutite but sometimes are enriched in
certai n zones. Very fi ne parti cul ate manganese oxi des
commonly create gray-black, weakly laminated zones within
the lutite. Layers of altered ash are infrequently observed
(Fig. 4.1). Data on all cores used in this study are included
in Appendi x I.
Grain size of the sediment from the Greater Antilles
Outer Ridge is quite uniform (Fig.4~2) and consists of an
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