NanoSIMS: Insights to biogenicity and syngeneity of Archaean carbonaceous structures

NanoSIMS is a relatively new technology that is being applied to ancient carbonaceous structures to gain insight into their biogenicity and syngeneity. NanoSIMS studies of well preserved organic microfossils from the Neoproterozoic (similar to 0.8Ga) Bitter Springs Formation have established elemental distributions in undisputedly biogenic structures. Results demonstrate that sub-micron scale maps of metabolically important elements (carbon [C], nitrogen [measured as CN ion], and sulfur [S]) can be correlated with kerogenous structures identified by optical microscopy. Spatial distributions of C, CN, and S in individual microfossils are nearly identical, and variations in concentrations of these elements parallel one another. In elemental maps, C, CN, and S appear as globules, aligned to form remnant walls or sheaths of fossiliferous structures. The aligned character and parallel variation of C and CN are the strongest indicators of biogenicity.