Revisiting stepwise ocean oxygenation with authigenic barium enrichments in marine mudrocks

Abstract There are current debates around the extent of global ocean oxygenation, particularly from late Neoproterozoic to early Paleozoic, based on analyses various geochemical indices. We present a temporal trend in excess barium (Baexcess) contents marine organic-rich mudrocks (ORMs) provide an independent constraint redox evolution. The absence remarkable Baexcess enrichments Precambrian (>ca. 541 Ma) ORMs suggests limited authigenic Ba formation oxygen- and sulfate-deficient oceans. By contrast, Cambrian, marked by significant enrichments, corresponding substantial increases sulfate reservoir oxygenation level. Analogous modern sediments, Mesozoic Cenozoic exhibit no prominent enrichments. suggest that variations concentrations through time linked secular changes dissolved associated with elevated levels oxygenation. Further, unlike Mo, U, Re abundances, indicate overall level Paleozoic was substantially lower than at present.