The δ34S of seawater sulfate reflects processes operating at the nexus of sulfur, carbon, and dioxygen cycles. However, knowledge of past seawater sulfate δ34S values must be derived from proxy materials that are impacted differently by depositional and post-depositional processes. We produced new timeseries estimates for the δ34S value of seawater sulfate by combining 6710 published data from three sedimentary archives–marine barite, evaporites, and carbonate-associated sulfate–with updated age constraints on the deposits. Robust features in the records capture temporal trends in the δ34S value of seawater and its interplay with other Phanerozoic geochemical and stratigraphic trends. However, high-frequency discordances demonstrate that each record is differentially prone to depositional biases and diagenetic overprints. The amount of noise, quantified from the variograms of each record, increases with age for all δ34S proxies, indicating that post-depositional processes obscure detailed knowledge of seawater sulfate’s δ34S value deeper in time.