Fig. 4
Heterotrophy, community change and 25,28-bisnorgammacerane. a Stratigraphy of the ~750 Ma Chuar Group; b the change observed in the δ13C offset between kerogen and alkanes (noted as Δδ13CA-K; here normalised to kerogen) parallels the c anticorrelative transition that is observed between gammacerane (blue triangles; ND not detected), a molecular fossil derived from tetrahymanol producing ciliates, and 25,28-bisnorgammacerane (25,28-BNG; orange diamonds); and d an increase in eukaryotic-derived cholestane (ng/g TOC; ∑dia + reg; green diamonds) indicating a shift in the composition of the primary producing community36 and the intensity of heterotrophic reworking37
