Publikationsdatum:
2022-05-25
Beschreibung:
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 286 (2009): 546-555, doi:10.1016/j.epsl.2009.07.020.
Beschreibung:
During the Last Glacial Maximum much of North America was covered by the
Laurentide ice sheet. Its melting during termination 1 led to systematic changes in
proglacial lake formation, continental runoff, and possibly North Atlantic Meridional
Overturning Circulation. The accompanying change in chemical weathering rates in
the interior of North America throughout the deglaciation resulted in a pronounced
change in seawater Pb isotope composition in the western North Atlantic Ocean. Here
we present the first high-resolution records of seawater Pb isotope variations of North
Atlantic Deep Water extracted from authigenic Fe-Mn oxyhydroxides in three
sediment cores (51GGC, 1790 m depth; 31GGC, 3410 m depth; 12JPC, 4250 m
depth) from the Blake Ridge off Florida. These data reveal a striking excursion from
relatively unradiogenic 206Pb/204Pb as low as 18.93 towards highly radiogenic Pb
isotope compositions that was initiated during the Bølling-Allerød interstadial and
was most pronounced in both intermediate and deep waters during and after the
Younger Dryas (206Pb/204Pb as high as 19.38 at 8.8 ka in 4250 m). This pattern is
interpreted to be a direct function of increased inflow of continent-derived radiogenic
Pb into the western North Atlantic, supplied through chemical weathering of North
American rocks that had been eroded and freshly exposed during the preceding glacial
cycle. These sediment-derived data are complemented by new laser ablation Pb
isotope data from a ferromanganese crust from the Blake Plateau at 850 m water
depth, which show only small glacial-interglacial Pb isotope variations of the Florida
Current (206Pb/204Pb between 19.07 and 19.16). The lack of change in the Blake
Plateau record at the same time as the radiogenic excursion in the deeper sediments
supports a northern origin of the pulse of radiogenic Pb. After the Younger Dryas, the
deep western North Atlantic has experienced a persistent highly radiogenic Pb supply
that was most pronounced during the first half of the Holocene and still lasts until
today.
Beschreibung:
Funding for this project was provided by grant TH-12 02-2 of ETH Zurich.
Repository-Name:
Woods Hole Open Access Server
Materialart:
Preprint
Format:
application/pdf
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