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

• Main Authors: Simon, Q., /Thouveny, Nicolas, Bourles, D. L., Nuttin, L., Hillaire-Marcel, C., St-Onge, G.
• Format: Text
• Language: English
• Published: 2016
• Subjects: Be-10 cosmogenic nuclide; Authigenic Be-10/Be-9 ratios; (10)Befluxes; (230)Thxs-normalization; Baffin bay; Late quaternary; Glacial dynamics; Stratigraphic markers; Paleo-denudation rate; Freshwater flux; Arctique*; Baffin Bay; Baffin; North Atlantic
• Online Access: https://www.documentation.ird.fr/hor/fdi:010066864

Authigenic Be-10/Be-9 ratios and Be-10-fluxes reconstructed using the Th-230(xs), normalization, proxies of the cosmogenic radionuclide Be-10 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) Be-10 concentrations using the authigenic Be-9 isotope and Th-230(xs) methods yield equivalent results strongly correlated with sedimentological parameters (grain-size and mineralogy). Lower authigenic beryllium (Be) concentrations and Be-10/Be-9 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 Be-10 concentration in Baffin Bay by input and boundary scavenging condition changes. Most paleo-denudation rates inferred from the Be-10/Be-9 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 km(3).yr(-1) (0.006 Sv), consistent with recent models, has been calculated in order to sustain glacially-derived Be-10 inputs into Baffin Bay. It is concluded that in such environments, the authigenic Be-10 measured mainly depends on climatic effects related to the glacial dynamics, which masks the Be-10 production variation modulated by geomagnetic field changes. Altogether, these results challenge the simple interpretation of Be-10-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 ...