Isotopic signatures of mercury contamination in latest Permian oceans

Sedimentary records from the northwest margin of Pangea and the Tethys show anomalously high Hg levels at the latest Permian extinction boundary. Background delta Hg-202 values are consistent with normal marine conditions but exhibit negative shifts coincident with increased Hg concentrations. Hg isotope mass-independent fractionation (Delta Hg-199) trends are consistent with volcanic input in deep-water marine environments. In contrast, nearshore environments have Delta Hg-199 signatures consistent with enhanced soil and/or biomass input. We hypothesize that the deep-water signature represents an overall global increase in volcanic Hg input and that this isotope signature is overwhelmed in nearshore locations due to Hg from terrestrial sources. High-productivity nearshore regions may have experienced stressed marine ecosystems due to enhanced Hg loading.