Continental shelf drift deposit indicates non-steady state Antarctic bottom water production in the Holocene
May 18, 2001

Authors: Harris, P.T., Brancolini, G., Armand, L., Brusetti, M., Beaman, R.J., Giorgetti, G., Presti, M., Trincardi, F.

Year: 2001

Publication: Marine Geology 179(1-2): 1-8. doi: 10.1016/S0025-3227(01)00183-9


A late Quaternary, current-lain sediment drift deposit over 30 m in thickness has been discovered on the continental shelf of East Antarctica in an 850 m deep glacial trough off George Vth Land. Radiocarbon dating indicates that a period of rapid deposition on the drift (averaging 290 cm/kyr) occurred in the mid-Holocene, between about 3000 and 5000 yr before present (yr BP). Slower deposition rates of around 10 cm/kyr, during the past 0-3000 yr and from 5000 to about 13000 yr BP, coincides with the deposition of bioturbated, ice-rafted debris (IRD) rich, sandy mud under an energetic bottom current regime.

In contrast, the mid-Holocene (3000-5000 yr BP) sediments are fine-grained, laminated to cross-laminated with minimal IRD content, and are contemporaneous with a period of warmer marine conditions with less sea ice production. This pattern suggests that bottom currents were weaker than present day in the mid-Holocene, and that the rate of dense bottom water production was reduced at this time.

This scenario is consistent with the hypothesis on non-steady state rates of Antarctic bottom water production through the Holocene as recently proposed by Broecker and his colleagues.

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