Figure 2.

Distribution of elements in the microfossil Polysphaeroides filiformis

(A) Microphotograph (Scale bar = 50 μm) of the studied specimen with a dashed box that corresponds to the selected area where SR-nanoXRF maps were acquired. Red arrows show ICIs within several cells.

(B–I) SR-nanoXRF maps of Br, Ni, Co, Ca, Cu, Fe, Zn, and S, obtained at synchrotron ESRF (pixel: 300 nm, 250 ms/px). (B) shows the enrichment of Br in cell walls. (C and D) show the specific enrichment of Ni and Co, respectively, in ICIs. (C) shows, with red arrows, the same ICIs pointed in (A). (G) shows the enrichment of Fe in P. filiformis and highlights that Fe is mainly present as hotspots in ICIs and not homogeneously such as Ni and Co.

(J) Zoom on a single cell from P. filiformis ((J) in microphotograph (A)). The brown cell contains a black structure (the ICI – red arrow) in the center.

(K and L) SR-nanoXRF maps of Ni and Co in the ICI (red bracket) within the cell (J). Maps in (K) and (L) were also obtained at synchrotron ESRF (pixel: 100 nm, 500 ms/px). Color scales correspond to the number of counts for each map. The darker red corresponds to the higher number of counts and the darker blue is the lower number of counts. For more results, see Figures S5–S7, S10, and S11.