Fig. 3: Micro-dissolution seams in Sample A.

a XFM map of the Kaiwhata limestone displaying Ca (grey scale) and Fe (red scale). Bedding is horizontal. The white arrow points to a dissolution structure with a thickness of 20 μm arrested by the micro-fossil underneath it. Fossils appear as bright white ellipsoidal objects. The white rectangle marks a zone for which normalised averaged elemental profiles are plotted in (b). b Averaged and normalised profiles of Ca and Fe traverse six dissolution structures with Ca depletion and Fe enrichment (black arrows). The Fe profile is shifted down by −1 for visibility. c Magnified view of the zone for which averaged elemental profiles in (b) were obtained. The white arrows mirror the black ones in (b). The map scale is given in (b). d This magnified view of the Sr map of Sample A demonstrates that the dissolution structures are also zones of Sr depletion and truncate fossil shells (white arrows). This map has a horizontal extent of 0.5 mm, and the yellow arrow serves as location reference to the larger map in (a). The concentration unit is μg cm⁻². The XFM maps used to make this figure are provided in Supplementary Data 1.