Ocean ventilation and sedimentation since the glacial maximum at 3 km in the western North Atlantic

Abstract

Stable isotope, sedimentological, and radiocarbon data from cores at ∼3 km water depth on the Blake Ridge, western subtropical North Atlantic, reveal the history of deep water ventilation since the last glacial maximum (LGM). Bulk sediment accumulation rates varied locally by a factor of 2 under the influence of bottom currents in this sediment drift environment, but the sand flux, mostly foraminifera, was nearly identical at a given time. This suggests that the rain rate of foraminifera (mostly planktonic) was constant, that transport of foraminifera was negligible, and that current‐controlled differences in clay and silt transport drive bulk accumulation. In two of the cores, flux peaks in the benthic foraminifera Cibicidoides and Uvigerina peregrina occurred during the Younger Dryas (YD) cold event, and at 18.2, 19.6, 21.1, 25.0, and 28.1 ka. Radiocarbon measurements on those benthic foraminifera show the ventilation age of bottom waters was ∼1000 years during the YD, and for older events it was as great as 2000 years. These results contrast with Holocene ventilation, which was ∼500 years and 700 years at 1500 years and ∼7100 years before present, respectively.