Figure 4 | Scientific Reports

Figure 4

From: Alteration of rocks by endolithic organisms is one of the pathways for the beginning of soils on Earth

Figure 4

Organic matter at the different hierarchical levels of endolithic system (a) and its chemical composition (b): a1 – exfoliation reveals primary production of OM inside leucogranites at the Larsemann Hills of East Antarctica (photo in plan); a2 – vertical profile of endolithic system inside gneiss at the Thala Hills of East Antarctica with cyanobacteria and lichen dominated organic layers, bleached eluvial and illuvial horizons differentiated by Fe and C content; a3 – cyanobacteria biofilms covering quartz and feldspar grains; a4 – flake-like quartz degradation induced by cyanobacteria biofilm; a5 – weathering pattern on feldspar and quartz around the cyanobacterial biofilm and produced by it, reflected light image of the thin section in dark field, light areas indicate increased reflection of the incident light from highly weathered surfaces; a6 – thin section through cryptic organogenous horizon of endolithic system indicating biofilms penetrating between quarts and feldspar grains, several generations of OM are present including chlorophyll, carotenoids and Fe-containing organo-mineral coatings, reflected light image in bright field; a7,a8 – SEM micrographs (SE-secondary electrons) of cryptic fresh cyanobacterial coatings; a9 – SEM-SE micrographs of mature partly fossilized organo-mineral coatings without clear cellular morphologies. (b) - chemical composition of green and brown OM generations in endolithic system according to the 13C-CPMAS NMR, for integration, chemical shift regions were used as given: alkyl C ((−10) to 45 ppm), O/N-alkyl C (45 to 110 ppm), aryl/olefine C (110 to 160 ppm) and carbonyl/carboxyl/amide C (160 to 220 ppm).

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