Fig. 2: Stratigraphy, magnetic susceptibility, and δ⁵⁶Fe isotope geochemistry at Oraparinna.

(Left) Stratigraphic log featuring the key sedimentological facies of BIF. Lower-case letters refer to outcrop photographs (Supplementary Fig. 4). The colors shown, extracted from photographs, are accurate representations of the rock sequence variability. The lower faulted contact is at −12 m (see Supplementary Fig. 5 for additional field data). (Right) Magnetic susceptibility with 2σ uncertainty (black; Supplementary Table 1). δ⁵⁶Fe isotope variability from two sections at Oraparinna: light red is the same section as ours¹⁰, and dark red is the section of ref. ¹⁶ ~6 km along strike (Supplementary Fig. 6); slightly less positive values at our section likely indicate relative proximity to the ice grounding line, consistent with more stratified diamictite than in the section of ref. ¹⁶. Best-fit degree-2 polynomials for each dataset (dashed lines). Note peak values for both trends occur in the middle of the succession. Rock magnetic experiments were performed on samples between 51 and 76 m (Fig. 5 and Supplementary Fig. 10).