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In the last few decades, the development of nontraditional isotope (e.g., Mo, Tl, U) measurements of redox sensitive metals provided information about the redox evolution of Earth’s oceans and atmosphere. Rhenium (Re) isotopes have the potential to fill a critical gap in the isotope proxy toolkit. Currently, there are proxies for ocean-basin-scale oxygenated and anoxic (0 uM O2 with no H2S) conditions, but there is not yet a proxy that can detect when large parts of the oceans were in a low-O2 but not anoxic condition, termed ‘suboxic’ (10 ≥ O2 > 0 uM). Detecting suboxic conditions is particularly important because some aerobic organisms can live in extremely low-O2 waters (down to ~10 nM O2; Stolper et al. 2010), and so it is of great interest to know when large parts of the ocean crossed from anoxic to suboxic conditions. Rhenium concentrations have been used as a paleoredox proxy to track suboxic and anoxic marine redox conditions locally, but do not easily extend globally. Because of the long residence time of Re in the oceans, the Re isotope proxy can likely track changes in the extent of suboxic conditions globally in the ocean. Previous publications provided methods for digesting and purifying Re for δ187Re analysis from different materials (e.g., seawater, basalt, sedimentary rocks, chondrites; Miller et al., 2015, Liu et al., 2017, Dellinger et al., 2019, Dickson et al., 2020). These publications set the foundation for creating a δ187Re ocean mass balance. However, there is as yet no method that specifically targets the authigenic Re in shales, which has the potential to directly capture δ187Re of contemporaneous seawater. Here, we report a novel method for digesting samples that is done in a single step that excludes the use of HF, utilizing the well-established Carius tube (CT) digestion technique. By not using HF, this method does not dissolve the silicate portion of samples, allowing the targeted removal of authigenic Re. We also introduce a two-step column chemistry approach that can be utilized to purify Re from large samples with very low Re concentrations. We are applying this new method to characterize δ187Re in modern euxinic and suboxic settings including the Black Sea and the Benguela margin.