## 4 Results and Discussion
### \(\mu\)-EDXRF Analysis
A first inspection of the \(\mu\)-EDXRF images acquired for the bulk matrix of SP1 revealed that Ca was widespread in the rock body, with two well-visible calcium-filled veins likely originating from stylolites and/or recrystallization bands. A uniform distribution was also observed for Si and Fe, although they were only visible in low amounts, representing the main constituents of the rocky matrix, likely due to the presence of quartz, clay minerals, and iron oxides. A general inspection of the maps reveals evident changes from a uniform distribution in the case of Al, K, and Ti, which appear to be mainly concentrated in specific regions. In particular, both Al and K appear to be clustered in the bottom-left region of the stone, likely due to the presence of mineral deposits and Al-/K-rich inclusions within the bulk matrix. In the case of Ti, a spotty distribution pattern, such as that typically originated by Ti-bearing accessory minerals, can be observed, suggesting localized fractions of rutile and/or anatase (TiO\({}_{2}\)). As far as the external surface of the SP1 sample is concerned (SP1/_surf_), the presence of Ca-poor regions, clearly visible in the SP1/_surf_ Ca distribution map, supports the hypothesis of carbonate leaching due to environmental phenomena and burial conditions. Worthy of note is the Ca-rich cluster clearly visible in the top-central region of the image, corresponding to a white crust upon the SP1 surface, allowing us to attribute the observed surface crusts likely to calcite rather than gypsum. Moreover, Si appears to be uniformly distributed, while Fe follows divergent pathways likely originating from biological activity,with Fe being essential for bacterial growth and biofilm formation. Finally, the obtained distribution for Al reveals a uniform distribution of clay-rich zones, whereas in the case of K and Ti, a clustering in the central part of the image that gradually thins out towards the edge can be observed, suggesting K-bearing clays and detrital heavy minerals localized in the central area of the surface. For comparison, Figure 7 shows the Ca, Si, Fe, Al, K, and Ti \(\upmu\)-EDXRF distribution maps from the bulk matrix (SP2/_bulk_) and over the external surface (SP2/_surf_) of the \"reference\" SP2 sample. As far as the bulk matrix is concerned (SP2/_bulk_), the obtained Ca, K, and Al distribution maps appear to be consistent with a typical limestone, with aluminosilicates spread over the whole cross-section. Interestingly, the observation of two parallel high Ca-rich veins might reflect recrystallized zones, possibly from fluid interaction or weathering. Even in this case, a fine dispersion of clay minerals and iron oxides can be reasonably hypothesized from the distribution maps of Si and Fe. However, the slight enrichments in Fe content might correspond to oxidation rims fostered by recrystallization. Accessory minerals like Ti-bearing phases are minor but consistent with an argillaceous lithology. Concerning the external surface of SP2 (SP2/_surf_), Ca, Si, and Fe appear to be quite widespread across the surface, with minor surface variations reflecting the presence of crusts originating from superficial processes. In particular, the presence of a crust on the right-hand side of the map can be considered to be responsible for the red spot observed in both the Ca and Fe distribution maps. The distributions of Al and K appear to be less finely dispersed compared with previous observations, most likely due to the presence  
Figure 6: \(\upmu\)-EDXRF maps for Ca, Si, Fe, Al, K, and Ti detected in the bulk (cross-section, SP1/_bulk_) and external surface (SP1/_surf_) of SP1. The rainbow color scale relates to the intensity of the main XRF transition line of the corresponding element. of medium-sized aluminosilicates and K-bearing clay aggregates. Interestingly, highly concentrated Ti spots can be clearly distinguished.