Abstract

Temporal fluctuations of silt mean particle size and foraminiferal indices were used to examine fluctuations in velocity and position of the axis of the Deep Western Boundary Undercurrent (DWBUC) on the North American continental margin. From 25 to 17 ka the DWBUC axis was 500 m shallower and farther inshore than its present position on the lower rise; current speed was high from 25 to 20 ka and then waned until 17 ka. Between 17 and 7 ka the major axis of the DWBUC shallowed to 4000 m; current speed increased from 17 to 11 ka but slowed from H to 7 ka. Since 7 ka the DWBUC axis has deepened to its modern position at 4900 m. The zone of maximum carbonate dissolution remained below the DWBUC; the most intense dissolution was from 22 to 9 ka and 5 to 2 ka. Highest abundance of Uvigerina and highest percent benthic foraminifera were immediately above the DWBUC from 22 to 7 ka, after which values of both parameters fell to near zero.

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