Authigenic 10Be/9Be ratios and 10Be-fluxes (230Thxs-normalized) in central Baffin Bay sediments during the last glacial cycle: Paleoenvironmental implications

• Published in: Quaternary science reviews 2016-05, Vol.140, p.142-162
• Main Authors: Simon, Quentin, Thouveny, Nicolas, Bourlès, Didier L., Nuttin, Laurence, Hillaire-Marcel, Claude, St-Onge, Guillaume
• Format: Article
• Language: English
• Subjects: 10Be cosmogenic nuclide; 10Befluxes 230Thxs-normalization; Authigenic 10Be/9Be ratios; Baffin bay; Freshwater flux; Glacial dynamics; Late quaternary; Paleo-denudation rate; Stratigraphic markers
• ISSN: 0277-3791; 1873-457X
• DOI: 10.1016/j.quascirev.2016.03.027

Authigenic 10Be/9Be ratios and 10Be-fluxes reconstructed using the 230Thxs normalization, proxies of the cosmogenic radionuclide 10Be production rate in the atmosphere, have been measured in a sedimentary core from Baffin Bay (North Atlantic) spanning the last 136 ka BP. The normalization applied on the exchangeable (authigenic) 10Be concentrations using the authigenic 9Be isotope and 230Thxs methods yield equivalent results strongly correlated with sedimentological parameters (grain-size and mineralogy). Lower authigenic beryllium (Be) concentrations and 10Be/9Be ratios are associated with coarse-grained carbonate-rich layers, while higher authigenic Be values are related to fine-grained felspar-rich sediments. This variability is due to: i) sediment composition control over beryllium-scavenging efficiency and, ii) glacial history that contributed to modify the 10Be concentration in Baffin Bay by input and boundary scavenging condition changes. Most paleo-denudation rates inferred from the 10Be/9Be ratio vary weakly around 220 ± 76 tons.km−2.yr−1 (0.09 ± 0.03 mm.yr−1) corresponding to relatively steady weathering fluxes over the last glacial cycle except for six brief intervals characterized by sharp increases of the denudation rate. These intervals are related to ice-surging episodes coeval with Heinrich events and the last deglaciation period. An average freshwater flux of 180.6 km3.yr−1 (0.006 Sv), consistent with recent models, has been calculated in order to sustain glacially-derived 10Be inputs into Baffin Bay. It is concluded that in such environments, the authigenic 10Be measured mainly depends on climatic effects related to the glacial dynamics, which masks the 10Be production variation modulated by geomagnetic field changes. Altogether, these results challenge the simple interpretation of 10Be-concentration variation as a proxy of Interglacial/Glacial (interstadial/stadial) cycles in Arctic and sub-Arctic regions. They rather suggest the effect of higher-frequency paleoclimatic changes and local glacial dynamics on 10Be signature. •10Be/9Be ratios and 10Be-fluxes yield equivalent results from glaciomarine sediments.•10Be-systematic variability mainly obeys to glacio-climatic condition changes.•10Be production proxies do not allow to characterize the geomagnetic features in PC16.•Denudation rates are steady except for brief ice surging episodes coeval to H-events.•10Be concentration is controlled by freshwater inputs from regional Ice Sheets.