Fig. 2: Typical stylolites.

a Transmitted-light micrograph with crossed polarisers of an oolitic grainstone of the Gudman Oolite²⁵. The serrated, black zones are stylolites, which clearly dissolved the deformed, ellipsoidal ooids (dark-grey grains). This image demonstrates that stylolite tooth amplitude presents a lower-bound estimate to dissolution. The dashed white line traces a concentric primary growth layer of a dissolved ooid. The white arrow denotes the ooid long axis, which extends beyond the lower image margin. The stylolite at the upper tip of the ooid exhibits a maximum amplitude (yellow arrow) that is considerably smaller than the portion of the upper long axis that has been removed by dissolution. This effect is even more pronounced in the larger ooid above the discussed stylolite interface. The green arrow marks the location for the concentration profile shown in (c). b Micro-scale XFM map of the elements Ca (grey scale) and Fe (red scale) of the upper part of the micrograph seen in (a). Saturated colours indicate high element concentrations. Strongly serrated stylolites are characterised by low Ca concentrations (black colours) and high Fe concentrations (bright red colours). The blue arrow marks the position of the concentration profile in (c) and is 250 μm long. c An elemental cross-section across a stylolite shows that Ca is depleted by ~55% while Fe is enriched about 30 times within this stylolite. Here and in all following normalised elemental profiles, error bars are smaller than symbol size and thus not shown.