Abstract :
[en] Mineral assemblage, trace element content and Nd and Pb isotope signatures were analysed on the fine
fraction (<20 mm) of sedimentary records from the Northern Mendeleev Ridge in the Central Arctic
Ocean. Our aimwas to identify the detrital particle provenance and to interpret the changes over the past
w250 ka in the relative contribution of the different source-areas in relation to paleoenvironmental
conditions. The clay mineral assemblage and the Nd and Pb isotope signatures depict systematic changes
over the Late Quaternary. The bulk mineralogy exhibits increases in the relative contribution of carbonate
minerals vs. silicates in interglacial/deglacial intervals. In glacial intervals, the mineral assemblage of the
<20 mm fraction is characterised by an enrichment in kaolinite, counterbalanced by a decrease in illite.
The Nd and Pb isotope signatures of <20 mm fraction are interpreted using a three end-member mixing
model, involving crustal supplies from North America and Canada, from the Siberian margin and some
from volcanic material. A compilation of geochemical signatures of geological terraines surrounding the
Arctic Ocean allowed each end-member to be assigned a representative signature, averaging the signal of
the eroded terraines. The Suspended Particulate Matter (SPM) of the MacKenzie River represents an
average signature of the sedimentary supplies delivered from the North American platform and Canadian
margin. The SPM of the Lena River reflects the mean sedimentary signature of the Siberian platform. The
Okhotsh-Chukotka province from the Eastern border of Siberia is identified as the most probable volcanic
source. Late Quaternary evolution of the estimated relative contribution of the three end-members
confirms that the sediment provenances in the Central Arctic Ocean remain close to the current conditions
during past interglacials/deglacials MIS1e3, MIS5/TII and MIS7/TIII. In contrast, glacial conditions
(MIS4 and MIS6) record minimum supplies from the American margin, associated with increased volcanic
contribution, to the Mendeleev Ridge core location suggesting a different sea-ice circulation
associated with a low sea-level and reduced shelf area.
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