Fig. 2.

Box plots of the Sturtian IF redox proxy data. (A) Fe/Al ratios, (B) Mn/Al ratios, (C) Ce anomalies (Ce_n/Ce_n*), and (D) Fe isotope ratios (δ⁵⁶Fe) from the ice-contact, ice-proximal, and ice-distal facies. Note that multiple facies are present in each study area (SI Appendix). (E) Box plots showing the range of Fe isotopic compositions of the Sturtian IFs (this study; n = 81) relative to marine sediments (IFs, shales, carbonates, hydrothermal deposits, Fe sulfides, and Fe oxides; literature data updated from ref. 68; SI Appendix) from 3 time bins: prior to and during the Great Oxidation Event (>2,200 Ma; n = 1118), between the Great Oxidation Event and the Phanerozoic (2,200 to 541 Ma; n = 321), and the Phanerozoic Eon (<541 Ma; n = 252). Boxes represent 50% of the data (the interquartile range); the mean is represented by a black circle and the median by a black line. Outliers (outside the interquartile range) are represented by a gray circle; extreme outliers (greater than double the interquartile range from the median; n = 6) are not shown. Whiskers represent extreme values that are not outliers.