Fig. 3: Stable isotope compositions of Hg in all study sections.
From: Recurrent photic zone euxinia limited ocean oxygenation and animal evolution during the Ediacaran
a Δ199Hg vs. δ202Hg and b Δ200Hg vs. Δ199Hg for Weng’an (WA), Taoying (TY), Wuhe (WH), and Yuanjia (YJ) sections. Common Hg sources based on modern samples (average ±1 SD) are also plotted to show their possible contributions to Hg isotope variations of the Doushantuo samples. See Supplementary Fig. S5 and Supplementary Text S3 for details and references for modern data. The “Mesoproterozoic PZE” and “Late Devonian PZE” are the Hg isotope data in sedimentary rocks deposited under photic zone euxinia (PZE) from the Mesoproterozoic Atar and El Mreiti groups16, and from the Late Devonian Chattanooga Shale39, respectively. The black short-dash lines are the linear regressions for all Doushantuo samples (in panel a, slope = −0.10 ± 0.01, R2 = 0.62, P < 0.001; in panel b, 0.10 ± 0.01, R2 = 0.55, P < 0.001). The red dash lines are reference lines of experimental results of dark abiotic oxidation of Hg(0) by thiol compounds (in panel a, slope = −0.12; in panel b, slope = 0.13)46. The error bars are analytical uncertainties defined in the method section.
