Proc. IODP | Volume 346 doi:10.2204/iodp.proc.346.203.2017 Tada, R., Murray, R.W., Alvarez Zarikian, C.A., and the Expedition 346 Scientists Proceedings of the Integrated Ocean Drilling Program, Volume 346 Abstract Within the south of the marginal sea between Japan and Korea, interstitial water (IW) profiles exhibit a prominent sulfate–meth- ane transition (SMT) in the upper few meters of sediment. As the SMT has become a focus of attention, IW samples were collected at high spatial resolution within shallow sediment at Sites U1426 and U1427 and examined on board the R/V JOIDES Resolution, un- der the auspices of the Integrated Ocean Drilling Program, for a wide range of dissolved species. However, irregularities were noted for the sulfate (SO 4 2– ), Ba, and Fe concentration profiles, each of importance to understanding the SMT. Splits of 134 IW samples, prepared with HNO 3 during the expedition, were there- fore reanalyzed at Rice University for S, Ba, and Fe, with S as a proxy for SO 4 2– . Results of 134 samples included 29 duplicates with low percent difference (0.01%–34.69%, 0.01%–14.90%, and 0.03%–35.19%) and 6 spiked blanks with low percent error rela- tive to stock solution concentration (1.59%, 2.41%, and 4.11%). The shore-based S and Ba profiles have trends similar to those de- termined on ship but with obvious offsets. The remeasured Fe profiles are comparable to those measured on ship, albeit with more data points. Although the IW samples were measured be- tween 95 and 113 days after the expedition, the new results have high data reproducibility, render smooth profiles, and give more expected chemistry across the SMTs. For these three elements, we suggest the new results should replace the shipboard data. Introduction Anaerobic oxidation of methane (AOM) may be a dominant pro- cess in shallow sediment across continental slopes (D’Hondt et al., 2002; Dickens, 2001). During AOM, downward diffusing sul- fate reacts with upward migrating methane as follows (Reeburgh, 1976, Barnes and Goldberg, 1976): CH 4 + SO 4 2– → HCO 3 – + HS – + H 2 O. The microbially mediated reaction (Boetius et al., 2000) typically occurs across a relatively thin and conspicuous geochemical hori- zon (Devol and Ahmed, 1981), generally now referred to as the sulfate–methane transition (SMT). Other than producing bicar- bonate and hydrogen sulfide ions, AOM indirectly affects the Data report: reanalysis of interstitial water barium, iron, and sulfur concentrations at Sites U1426 and U1427 1 Clint Miller 2 and Gerald Dickens 2 Chapter contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Methods and materials . . . . . . . . . . . . . . . . . . . 2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1 Miller, C., and Dickens, G., 2017. Data report: reanalysis of interstitial water barium, iron, and sulfur concentrations at Sites U1426 and U1427. In Tada, R., Murray, R.W., Alvarez Zarikian, C.A., and the Expedition 346 Scientists, Proceedings of the Integrated Ocean Drilling Program, 346: College Station, TX (Integrated Ocean Drilling Program). doi:10.2204/iodp.proc.346.203.2017 2 Department of Earth Sciences, Rice University, Houston, TX, 77005, USA. Correspondence author: clint.m.miller@rice.edu