Fig. 4: EDS profile on the preserved soft tissues of STM10–12 shows they underwent alumino-silicification and slight iron mineralization.

a SEM image (same image as Fig. 2d) with yellow line showing where the EDS profile was taken. b Enlargement and horizontalization of a. The EDS profile was followed along the external layer of glue, the soft tissue layer with preserved fibers, and the sediments below them. c EDS profile showing the chemistry of all features (glue, soft tissues, and sediments) of major elements in counts per second (cps). The layer of glue is highly enriched in carbon (C), followed by low amounts of oxygen (O), silicon (Si) and aluminum (Al). The Si and Al signals seen in the glue are most likely a contaminant from the sediment and/or soft tissues beneath. The Si signal may also come from the glass of the ground-section. The soft tissues (concluded to be part of the original perifollicular membrane) beneath the consolidant show a net drop in C content, but a clear increase in Si, O, and Al. The source of Al in the soft-tissues may come from clay minerals within the sediments below, and it is possible that direct precipitation of authigenic clays onto the tissues occurred shortly after death. The soft-tissues are also enriched in Iron (Fe, blue line) when compared to the sediments. There are also negligible amounts of magnesium (Mg), potassium (K), calcium (Ca), and titanium (Ti) in the sample.