Productivity Proxies in Surface Sediment of the East Antarctic Margin: A Focus on Excess Ba

• Main Authors: Creac'h, Layla, Noble, Taryn L., Chase, Zanna, Townsend, Ashley T., Pérez-Tribouillier, Habacuc, Dietz, Christian
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2024
• Subjects: paleo-productivity; barite; 230Th-normalization; Antarctic margin; Antarctic; The Antarctic; Antarc*; Ice Sheet
• Online Access: https://hdl.handle.net/20.500.11850/688089; https://doi.org/10.3929/ethz-b-000688089

Components such as organic carbon (Corg), carbonate, opal or barite are valuable paleoceanographic proxies, enabling the reconstruction of past changes in carbon cycling under various climate regimes, particularly when 230Th-normalization is used to reconstruct particulate vertical rain rates. However, these components can be affected by poor preservation in the sediment. Barite is generally better preserved compared to other productivity proxies, but its estimates using “excess barium” (xsBa) calculations or Ba/Al ratios may not always be reliable, especially near the continental margin. This study presents a multi-proxy investigation of surface sediments from the East Antarctic margin to assess the robustness of xsBa as a paleo-productivity proxy. 230Th-normalized fluxes of Corg and opal record consistent variations within the sediment, while xsBa appears to be affected by different processes. Results suggest that xsBa may not robustly reflect marine barite in sediment close to the Antarctic Ice Sheet, because (a) the authigenic signal is overprinted by large lithogenic inputs; and (b) other mineral phases (e.g., Fe oxides) may be important Ba carrier phases in the region. 230Th-normalized Ba concentrations in the oxide-free sediment fraction, which was reductively leached to remove Fe-Mn oxides, aligns with the other biogenic fluxes, implying that specific leaching for barite isolation might be required in sediment proximal to the Antarctic Ice Sheet, rather than using the standard “xsBa” calculation or Ba/Al ratios. This study gives new insights into the sedimentary cycle of Ba in East Antarctic sediment and confirms the importance of using multi-proxy records to perform paleo-reconstructions. ISSN:2572-4525 ISSN:2572-4517