Sulfur and Oxygen Isotopic Composition of Dissolved Sulfate in Interstitial Water Sample Residues from IODP Site U1553 on the southern Campbell Plateau

Dissolved sulfate sulfur and oxygen isotope results and carbonate associated sulfate sulfur isotope results from IODP Site U1553 (166°11.4801′E, 52°13.4294′S) located on the Campbell Plateau are presented. Pore water collected during IODP Expedition 378 at Site U1553 in January 2020 were used for this study. These samples were processed using a procedure modified from that in Wotte et al. (2012, doi:10.1016/j.gca.2012.02.013) to extract the sulfate from the aqueous phase. The dissolved sulfate in the pore water was extracted by first adding 10% HCl to acidify the pore water, then the sulfate was removed from solution as barium sulfate using a 10% BaCl2 solution. Sulfur isotopes in dissolved sulfate were analyzed using an EA-Isolink elemental analyzer connected in continuous flow to a MAT253 IRMS and the oxygen isotopes in dissolved sulfate were measured using a thermal conversion elemental analyzer connected in continuous flow to a Delta V IRMS. Analytical precision was measured using repeated measurements of a blind standard with an average 2-sigma of 0.4‰ for sulfur isotopes (IAEA-SO-5) and 0.3‰ for oxygen isotopes (NBS-127). These data were collected to examine the impact of a long-duration (~26-million-year) unconformity has on the fidelity of the carbonate geochemical archive.