Fig 8. NanoSIMS isotope enrichment maps of organic layers shown in Fig 7A, revealing the presence of spheroids (TSI: Total secondary ions).

Note that these bodies are generally enriched in C (¹²C) compared to the surrounding areas. Organic matter (¹²C¹⁴N) and sulfur (³²S) are preferentially enriched at the edges, whereas the centers represent carbonate phases. This spatial arrangement of the isotopes is further illustrated in the color-coded overlay maps (¹²C & ¹⁴N; ¹²C & ³²S).