Impacts of Deep Water Structuring on Seabed Pollution Levels: Evidence from Radiogenic Isotopes (Pb-Sr-Nd) in Surface Sediments Along the Reykjanes Ridge (Southern Iceland)

Significant proportions of debris containing pollutants are present in remote and unknown areas of the deep seabed. Although identified amongst the top threats to marine ecosystem and human health, the mechanisms that particulate materials entered rapidly these deep ocean systems are still matter of debate. This study use depicting radiogenic isotopes (Sr, Nd, Pb) to question the relationship between the seabed sediment contamination levels and ambient stratification in the North Atlantic Ocean. On this basis, we studied sedimentary inputs and related mechanisms from more recent sequences collected at three locations representing different deep-sea hydrodynamics along the Reykjanes Ridge. Sm-Nd concentrations, as well as Sm-Nd-Sr-Pb isotopic compositions, were determined in digested and purified fraction of the sediment cores by Thermal Ionization Mass Spectrometry (TIMS). The Sm-Nd-Sr-Pb data simply reflect the scale of the perturbation of upper part (0-15 cm) of the sequences, which is much more pronounced in east flank than crossing and west bordering ridge areas. The Pb-Pb systematics show that the intensity of water mass mixing modulates degree of contamination and induced the modal transport of detrital components. As consequence of ambient stratification in this region, two major transport processes of pollutant downwards to the sediments are proposed: (i) sediments entrainment in the eastern flank and over ridge axis primarily dominated by vertical flux of particulates controlled by repackage and dislocation by strong mechanical mixing; and (ii) in the west flank, advection of abyssal waters, due to well-stratified mixing layer, provides particulates from the NEADW1 and DSOW

Radiogenic isotope investigation of the St-Robert H5 fall

International audienc

Isotopic and geochemical evidence for differentiation and crustal contamination from granitoids of the Berens river subprovince, Superior province, Canada.

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Pb-Sr-He isotope and trace element geochemistry of the Cape Verde Archipelago

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Heat flow variations in the Grenville Province, Canada

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U-series measurements in Tyrrhenian deposits from mallorca - Further evidence for two last-interglacial high sea levels in the Balearic Islands

The Campo de Tiro type-section for the Tyrrhenian ecostratigraphic beds of the Balearic Islands shows four indurated littoral conglomerates and beach-rocks, unconformably superimposed. The lower two units (1 and 2) are separated by a thin layer of reddish continental silts: both contain a typical Eutyrrhenian fauna, whereas a Neotyrrhenian fauna characterizes the overlying units 3 and 4. Th/U measurements by thermal ionisation mass spectrometry on mollusk shells from these deposits yielded ages of ~135 ka (unit 1), ~ 117 ka (units 2 and 3), and a scatter of ages around ~100 ka (unit 4). The stratigraphic relationships and Th/U data indicate (i) that uranium was uptaken by mollusk shells (but Arca sp.) each time during a relatively short early diagenetic interval before cementation ensured a 'fair' closure of the radioactive system, (ii) two high sea stands characterized the Last Interglacial (Isotopic Substage 5e) of the Balearic Islands area, (iii) the duration of this episode was ~17 ka, and (iv) the change in faunal assemblages and disconformity observed between units 2 and 3 are due to fluctuations in sea level and surface water conditions which occurred during the second high sea level episode of the Last Interglacial

Heat flow, gravity, and structure of the Abitibi belt, Superior Province, Canada: implications for mantle heat flow

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