The thallium isotopic composition (ε²⁰⁵Tl) of seawater has been identified as a promising proxy for global oceanic redox conditions due to its close association with Mn oxide burial. Currently the preferred archives for past seawater Tl isotope reconstructions are from anoxic (no oxygen detected) and/or sulfidic (no oxygen detected and free sulfide present) environments that may suffer from basin restriction. Here we conduct a comprehensive modern calibration of authigenic sedimentary ε²⁰⁵Tl with core tops covering a wide range of bottom water oxygenation and sediment compositions. We show that quantitative Tl removal in the reducing porewaters (e.g., Mn reduction) at/near the sediment–water interface could allow the sediments to track the water column ε²⁰⁵Tl. Even if the bottom water is not anoxic, a shallow oxygen penetration depth under high export productivity and/or high sedimentation rates may still allow rapid oxygen consumption and buildup of reducing porewaters conducive for complete Tl removal. Thus, applications of the Tl isotope redox proxy can be greatly expanded beyond the anoxic conditions into places with open-ocean connections and high mass accumulation rates for high-resolution temporal reconstructions. We present a decision tree using the sediment enrichment factors of Mn, Ba, and U to determine whether sediment archives are likely to record the seawater ε²⁰⁵Tl. We additionally provide an estimate of authigenic Tl burial fluxes in environments with quantitative Tl removal, which is roughly double the size of the ‘euxinic/anoxic’ sink in previously published global marine Tl mass balance estimates.

海水的铊同位素组成（ε ²⁰⁵ Tl）由于与氧化锰埋藏密切相关，已被确定为全球海洋氧化还原条件的有希望的代表。目前，过去海水 T1 同位素重建的首选档案来自可能受到盆地限制的缺氧（未检测到氧气）和/或硫化（未检测到氧气且存在游离硫化物）环境。^{在这里，我们对自生沉积物 ε 205} Tl进行了全面的现代校准，其核心顶部覆盖了广泛的底水氧化和沉积物成分。我们表明，在沉积物-水界面处/附近的还原性孔隙水中（例如，Mn 还原）中的定量 Tl 去除可以使沉积物跟踪水柱 ε ²⁰⁵铊。即使底部水不是缺氧的，在高出口生产力和/或高沉降速率下的浅氧渗透深度仍可能允许快速耗氧和减少有利于完全去除 Tl 的孔隙水的积累。因此，Tl 同位素氧化还原代理的应用可以大大扩展到缺氧条件之外，进入具有开阔海洋连接和高质量积累率的地方，以进行高分辨率时间重建。我们提出了一个决策树，使用 Mn、Ba 和 U 的沉积物富集因子来确定沉积物档案是否可能记录海水 ε ²⁰⁵铊。我们还提供了对定量 Tl 去除环境中自生 Tl 埋藏通量的估计，这大约是先前发表的全球海洋 Tl 质量平衡估计中“euxinic/anoxic”汇的大小的两倍。