Article (Scientific journals)
Glacial/interglacial instabilities of the Western Boundary Under Current during the last 365 kyr from Sm/Nd ratios of the sedimentary clay-size fractions at ODP site 646 (Labrador Sea)
Fagel, Nathalie; Hillaire-Marcel, Claude
2006In Marine Geology, 232 (1-2), p. 87-99
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Keywords :
North Atlantic; Sm-Nd isotopes; deep circulation; Late Quaternary; clay fraction; Labrador Sea
Abstract :
[en] We present 40 Sm-Nd isotope measurements of the clay-size (< 2 mu m) fractions of sediments from the Southern Greenland rise (ODP-646) that span the last 365 kyr. These data track changes in the relative supply of fine particles carried into the deep Labrador Sea by the Western Boundary Under Current (WBUC) back to the fourth glacial-interglacial cycles. Earlier studies revealed three general sources of particles to the core site: (i) Precambrian crustal material from Canada, Greenland, and/or Scandinavia (North American Shield-NAS), (ii) Palaeozoic or younger crustal material from East Greenland, NW Europe, and/or western Scandinavia (Young Crust-YQ and (iii) volcanic material from Iceland and the Mid-Atlantic Ridge (MAR). Clay-size fractions from glacial sediments have the lowest Nd isotopic ratios. Supplies of young crustal particles were similar during glacial oxygen isotope stages (OIS) 2, 6, and 10. In contrast the mean volcanic contributions decreased relative to old craton material from OIS 10 to OIS 6 and then from OIS 6 to OIS 2. The glacial OIS 8 interval displays a mean Sm/Nd ratio similar to those of interglacials OIS 1, 5, and 9. Compared with other interglacials, OIS 7 was marked by a higher YC contribution but a similar similar to 30% MAR supply. The overall NAS contribution dropped by a factor of 2 during each glacial/interglacial transition, with the MAR contribution broadly replacing it during interglacials. To decipher between higher supplies and/or dilution, particle fluxes from each end member were estimated. Glacial NAS fluxes were systematically higher than interglacial fluxes. During the time interval examined, fine particle supplies to the Labrador Sea were strongly controlled by proximal ice-margin erosion and thus echoed the glacial stage intensity. In contrast, the WBUC-carried MAR supplies from the eastern basins did not change significantly throughout the last 365 kyr, except for a marked increase in surface-sediments that suggests unique modem conditions. Distal WBUC-controlled inputs from the Northern and NE North Atlantic seem to have been less variable than proximal supplies linked with glacial erosion rate. (c) 2006 Elsevier B.V All rights reserved.
Disciplines :
Earth sciences & physical geography
Physical, chemical, mathematical & earth Sciences: Multidisciplinary, general & others
Author, co-author :
Fagel, Nathalie  ;  Université de Liège - ULiège > Département de géologie > Géochim. sédiment. - Sédiment. mar. & continent. du quatern.
Hillaire-Marcel, Claude ;  UQAM > GEOTOP
Language :
English
Title :
Glacial/interglacial instabilities of the Western Boundary Under Current during the last 365 kyr from Sm/Nd ratios of the sedimentary clay-size fractions at ODP site 646 (Labrador Sea)
Publication date :
18 October 2006
Journal title :
Marine Geology
ISSN :
0025-3227
eISSN :
1872-6151
Publisher :
Elsevier Science Bv, Amsterdam, Netherlands
Volume :
232
Issue :
1-2
Pages :
87-99
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
CRSNG - Conseil de Recherches en Sciences naturelles et en Génie [CA]
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