Figure 3
From: Microbial and diagenetic steps leading to the mineralisation of Great Salt Lake microbialites
Characterisation of the successive mineralisation steps and composition of the mineral phases in a lithifying mat.
(A) CLSM image of photosynthetically active coccoid cyanobacteria (red fluorescence) embedded in extracellular organic matrix (EOM). (B) Representative EDS spectra of the four main mineral phases, each color corresponding to a specific mineral. The location of EDS analyses is indicated by asterisks on the SEM images. (C) CLSM image showing photosynthetically active coccoid cyanobacteria (red) embedded in EOM. The green fluorescence labelling is indicative of binding of Mg by the EOM. (D) SEM image of the same sample as C (CLSM). EOM is completely covered in Mg-Si anhedral, round crystals (orange arrow). (E) Image showing EOM casts of coccoid bacteria, covered by round Mg-Si crystals (Mg-Si phase lithifying mat; orange asterisk; EDS signature Fig. 3B and Supplementary Table S3). (F) CLSM image showing aragonite (bright yellow fluorescence; red arrow; corresponding raman spectrum can be found in Supplementary Fig. S9) nucleating in zone lacking photosynthetically active cyanobacteria. (G,H) SEM images showing aragonite nucleation (Ar; red asterisk locates the EDS spectrum Fig. 3B). Aragonite (AR) precipitates first inside dead coccoid cells, mineralises their wall and expands into the surrounding EOM, partly covered by Mg-Si phase (orange arrow).
