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 enegetic bottom current regime. In contrast, the mid-Holocene (3000±5000 yr bp) sediments are ®ne-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 that time. This scenario is consistent with the hypothesis of non-steady state rates of Antarctic bottom water production through the Holocene as recently proposed by Broecker and his colleagues.

Continental shelf deposit indicates non-steady state Antarctic bottom water production in the Holocene

Busetti M;
2001

Abstract

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 enegetic bottom current regime. In contrast, the mid-Holocene (3000±5000 yr bp) sediments are ®ne-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 that time. This scenario is consistent with the hypothesis of non-steady state rates of Antarctic bottom water production through the Holocene as recently proposed by Broecker and his colleagues.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.14083/2568
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