Reconstruction of environmental features by elemental stratigraphies of Antarctic marine sediments

In the framework of national (PNRA) and international (ESF HOLOCLIP project - Holocene climate variability at high-Southern latitudes: an integrated perspective) projects, several marine cores were retrieved from the Antarctic continental margin, in the Indian sector of the Antarctic Ocean (CB2010 A, George V Basin; WEGA 26PC12, WEGA 17PC02, WEGA 11GC03, Wilkes Basin) and in the Western Ross Sea (cJ5, Joides Basin; c20, Cape Hallett; c43, Wood Bay). By using 210Pb activities measured at the EPOC (Univ. Bordeaux I) and 14C measurements (Univ. Trieste), a tentative age scale was achieved indicating that the temporal frame of the cores spans the last centuries (CB2010 A) to the whole Holocene (cJ5). Here we present the main results achieved from the chemical elemental analysis performed by ICP-AES technique on the above mentioned cores, in order to point out specific environmental features such as oxic and anoxic conditions, bioproductivity, lithogenic content of the sediments. Several major and trace elements were measured (Al, Ba, Be, Ca, Co, Cu, Dy, Eu, Fe, K, La, Mg, Mn, Mo, Na, Ni, Sc, Sr, Ti, V, Y, Yb, Zn), including some Rare Earth Elements and some relevant chemical paleomarkers such as Ba, Mo and Mn. At this purpose, a devoted method for sample mineralization was developed, consisting in an acidic (HF+HNO3+HCl) digestion in microwave oven, aiming to destroy the silicic as well as the organic matrix. Afterwards, the samples were treated with H3BO3, in order to neutralize possible remaining HF, whose presence is not recommended for ICP-AES measurements. The method performances were tested on certified marine sediment materials (MESS-3) showing recoveries always within the certified uncertainty. The obtained elemental stratigraphies allowed pointing out interesting environmental features. As an example, considering the cJ5 core, the trend of the Ba/Al concentration ratio and Baexcess content, still debated markers of paleoproductivity were shown to finely match the one of Fragilariopsis curta relative abundance along the Holocene, suggesting that, once corrected for the crustal contribution, Ba can be used as a specific marker of bioproductivity at this site.