Fig. 6

BSE-SEM micrograph (A) and XFM map (B) of the vadose experiment incubated under burial (dark) conditions highlighting the occurrence of an extensive amount of fine-grained secondary minerals and weathered CRD grains held within a sample of biofilm. At high magnification (BSE-SEM), the bladed crystals of the Ca-S–O evaporite (C and D) suggest gypsum (EDS data not shown) and Ca-O-(C) is consistent with calcium carbonate. A high magnification BSE-SEM image highlighted in tile (D), amorphous carbonate precipitates are present in the system, though predominately seen in association with sulphate minerals (D). Small arrows focus on the locations of permineralised bacteria