Sources of Labrador Sea sediments since the last glacial maximum inferred from Nd-Pb isotopes

Fagel, Nathalie; Innocent, Christophe; Gariépy, Clément; Hillaire‐Marcel, Claude

doi:10.1016/s0016-7037(02)00866-9

Cited by 43 publications

(40 citation statements)

References 62 publications

(97 reference statements)

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“…Foraminifera assemblages and their stable oxygen and carbon isotope compositions implicate the inception of NEADW at 9.5 ka and suggest the presence of the Northwest Atlantic Bottom Water (NWABW) (i.e., NWABW is partly (∼50%) composed of DSOW) at 5.7 ka in the deep Labrador Sea [ Bilodeau et al , 1994]. Similarly, Nd isotopic signatures of the sediment clay‐size fraction do not show any contribution of DSOW off Greenland before 8.5 ka [ Fagel et al , 2002]. The DSOW was thus initiated around 6–8 kyr BP as indicated by 230 Th‐excess data [ Veiga‐Pires and Hillaire‐Marcel , 1998].…”

Section: Introductionmentioning

confidence: 99%

Nd and Pb isotope signatures of the clay‐size fraction of Labrador Sea sediments during the Holocene: Implications for the inception of the modern deep circulation pattern

et al. 2004

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[1] Nd and Pb isotopes were measured on the fine fraction of one sediment core drilled off southern Greenland. This work aims to reconstruct the evolution of deep circulation patterns in the North Atlantic during the Holocene on the basis of sediment supply variations. For the last 12 kyr, three sources have contributed to the sediment mixture: the North American Shield, the Pan-African and Variscan crusts, and the Mid-Atlantic Ridge. Clay isotope signatures indicate two mixtures of sediment sources. The first mixture (12.2-6.5 ka) is composed of material derived from the North American shield and from a ''young'' crustal source. From 6.5 ka onward the mixture is characterized by a young crustal component and by a volcanic component characteristic of the MidAtlantic Ridge. Since the significant decrease in proximal deglacial supplies, the evolution of the relative contributions of the sediment sources suggests major changes in the relative contributions of the deep water masses carried by the Western Boundary Undercurrent over the past 8.4 kyr. The progressive intensification of the Western Boundary Undercurrent was initially associated mainly with the transport of the Northeast Atlantic Deep Water mass until 6.5 ka and with the Denmark Strait Overflow Water thereafter. The establishment of the modern circulation at 3 ka suggests a reduced influence of the Denmark Strait Overflow Water, synchronous with the full appearance of the Labrador Seawater mass. Our isotopic data set emphasizes several changes in the relative contribution of the two major components of North Atlantic Deep Water throughout the Holocene.

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Section: Introductionmentioning

confidence: 99%

Nd and Pb isotope signatures of the clay‐size fraction of Labrador Sea sediments during the Holocene: Implications for the inception of the modern deep circulation pattern

et al. 2004

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“…() and North American Shield (NAS) from Fagel et al . (). Squares: potential local isotope signature [mean gneisses Baie region, Dickin and Higgins (), mean gneisses from Sept‐Îles (SI) and mean gneisses from Natashquan (NT), Dickin ()] and regional signature [Appalachian Pan‐African crust, Fagel et al .…”

Section: Discussionmentioning

confidence: 99%

Geochemical characterization (REE, Nd and Pb isotopes) of atmospheric mineral dust deposited in two maritime peat bogs from the St. Lawrence North Shore (eastern Canada)

Pratte

Vleeschouwer

Garneau

2017

J Quaternary Science

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Dust deposited on two ombrotrophic peat bogs (Baie and IDH bogs) of the St. Lawrence Gulf and Estuary north shore (Quebec) was geochemically characterized using rare earth element (REE) concentrations, Nd and Pb isotopes along with particle grain size. Both cores display similar ɛNd values, which suggests either a common source or sources with similar signatures in both regions. Combining Nd isotope data with REE patterns and particle size allowed for better insights into the source of deposited dust and the inference of past environmental and climatic conditions in both regions. REEs, ɛNd and grain‐size distribution suggest that, over the last 2000 years, the Baie bog received more local dust due to increased local storminess in response to greater regional hydroclimatic variability. The same phenomenon occurred in the IDH bog since 620 cal a BP, i.e. during the Little Ice Age, where hydroclimatic and paleoecological changes have been previously documented. While the dust reconstructions and regional climatic records agree relatively well, the discrepancies between paleodust records highlight the complex and variable structure of late Holocene changes in paleoclimate and more particularly past dust deposition in eastern Canada.

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“…Here, we analyzed the <2 µm size fraction, i.e., the sediment fraction that is least affected by ice rafting and consequently more representative of the suspended particulate load of deep currents (Fagel et al, 2002). Subsampling was at 20 cm intervals (173 samples) in the upper 32 m of the composite sequence (henceforth, all depths corresponds to composite-core depths).…”

Section: Methodsmentioning

confidence: 99%

“…Our aim here is to examine the relative contribution of fine particle supplies in the Labrador Sea by the Western Boundary Under Current (WBUC) during the last four glacial/ interglacial cycles (G/I). Earlier studies allowed us to characterize potential geographical sources of particles from Nd signatures of clay-size sedimentary fractions (Innocent et al, 1997;Fagel et al, 1999Fagel et al, , 2002. Using this approach on cored sediments from the ODP site 646 off southern Greenland, we draw a reconstruction of the past deep circulation changes in the NW Atlantic throughout the last 365 kyr.…”

Section: Introductionmentioning

confidence: 99%

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

Hillaire‐Marcel

2006

Marine Geology

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We present 40 Sm-Nd isotope measurements of the clay-size (<2 µm) 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 -YC) 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 ~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 modern 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.

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Sources of Labrador Sea sediments since the last glacial maximum inferred from Nd-Pb isotopes

Abstract: Pb isotopes have been measured in the clay-size fraction of Late Glacial and Holocene deep-sea sediments recovered from two Labrador

Cited by 43 publications

References 62 publications

Nd and Pb isotope signatures of the clay‐size fraction of Labrador Sea sediments during the Holocene: Implications for the inception of the modern deep circulation pattern

Nd and Pb isotope signatures of the clay‐size fraction of Labrador Sea sediments during the Holocene: Implications for the inception of the modern deep circulation pattern

Geochemical characterization (REE, Nd and Pb isotopes) of atmospheric mineral dust deposited in two maritime peat bogs from the St. Lawrence North Shore (eastern Canada)

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)

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