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consolidated (A.J. Silva, pers. comm.). Moisture content<br />

in the sediment is generally high and saturated bulk<br />

densities are low in comparison to other abyssal oceanic<br />

areas, also suggesting rapid deposition.<br />

At an average Pleistocene/Holocene sedimentation rate<br />

of 7 cm/1000 yr for the western sector of the Greater<br />

i 15<br />

Antilles Outer Ridge and 3 cm/1000 yr for the eastern sector,<br />

approximately 126 m and 54 m of sediment have accumulated in<br />

these provi nces, respecti vely, si nce the begi nni ng of the<br />

Pleistocene. These rates and thicknesses constrain the<br />

average rates of middle Eocene to Pliocene sedimentation<br />

to values slightly less than those in Table 5.1~<br />

From consi derati ons of depth, remoteness, and sea-floor<br />

morphology, the rates of sediment accumulation (up to<br />

30 cm/1000 yr) on the Greater Antilles Outer Ridge are more<br />

than an order of magni tude hi gher than expected, and only<br />

about 20% of the sediment can be attributed to carbonate<br />

deposition. Normally, a ridge isolated from downslope<br />

sedimentation and below the carbonate compensation depth<br />

would accumulate only pelagic sediment, probably at rates<br />

less than 0.5 cm/1000 years (Arrhenius, 1963). Thus the<br />

observed rapid sedimentation rates are strongly indicative<br />

of deposi ti on of sedi ment from other than normal pelagi c<br />

sources.<br />

i<br />

)

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