Extended Data Fig. 6: Sediment analyses.

Samples X1 and X2 come from the red stained area on which the ochre fragments OP1 and OP2, stone slab LS and quartzite cobble QC were found; and samples X3 and X6 were retrieved Layer 6 but at about 2 m far from the stained area (Supplementary Fig. G1). a, XRD spectra clearly showing that hematite is abundant in samples X1 and X2, and that it is not detected in samples X3 and X6. b, Raman spectra. Data of the reference hematite (CIT-2058) with RRUFF ID X050102 come from the RRUFF Project website (https://rruff.info/hematite/display=default/X050102), see also Anthony et al.⁶¹. c, High-temperature magnetic susceptibility measurements. Blue arrows represent the feature of partially-oxidized magnetite; and red arrows, of hematite. d, Magnetic component analysis of coercivity distributions calculated with the IRM-CLG program⁶⁶. Green, purple, blue and red lines indicate the low-coercivity component (IRM_L), middle-coercivity component (IRM_M), high-coercivity component (IRM_H), and the sum of these components (sum), respectively. B_1/2 is the field at which half of the saturation IRM (SIRM) is reached; and the dispersion parameter (DP) represents one standard deviation⁹⁹. B_L1/2, B_M1/2 and B_H1/2 represent B_1/2 of the low-, middle- and high-coercivity component, respectively. DP_L, DP_M and DP_H represent DP of the low-, middle- and high-coercivity component, respectively. The high-coercivity component (IRM_H) with median acquisition field (B_H1/2) of up to 575 mT is interpreted as single domain (SD) hematite, because the SD threshold grain size of hematite is considerably larger than 15 μm, and even up to 100 μm⁶⁸. This kind of hematite grains with high coercivities up to several hundreds of mT is usually of detrital origin^70,100. e, Fe element distribution via Micro-XRF imaging. The yellow arrows point to large (up to 150–200 μm) Fe-rich agglomerates, which probably contain a high proportion of hematite, whose presence is detected by XRD analyses (a), Raman spectroscopy (b) and mineral magnetic measurements (c, d).