Mineralized cells, colonies |
Chemotrophic |
Apparently widely distributed around volcanic particles (silt to sand-sized) in aqueous environments; reduced biomass development in oligotrophic environments, higher in hydrothermal environments; possibly in fluid inclusions in rapidly precipitated cements of the volcanic environments or evaporitic or hydrothermal environments (yet to be identified); possibly in hydrothermal conduits; possibly in cracks in submerged volcanic or other kinds of rock |
By rapid mineralization and occlusion of pore space |
In situ in a rock or in a portion of microfossil-containing rock that has been transported (or ejected) from elsewhere |
Microscopic |
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Concentrations of colonies can form biofilms |
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May form macroscopically visible black layers in rocks due to relatively high C content |
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Phototrophic |
On the surfaces of bedding planes/rocks in the photic zone |
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Possibly macroscopic, certainly microscopic |
Biogenic organics |
May or may not be associated with body fossils or other microbial remains preserved in situ, as described above; generically disseminated in fine-grained, anaerobic sediments, associated with phyllosilicates; trapped in evaporitic or hydrothermal precipitates |
In anaerobic matrices, e.g., fine-grained sediments, mineral cements, or chelated to phyllosilicates |
In situ in a rock or in a portion of carbonaceous rock that has been transported or ejected from elsewhere |
Microscopic but may be macroscopic if the organic components have been hydraulically concentrated or if there was sufficient energy to support a huge biomass, e.g., in the vicinity of hydrothermal activity |
Abiogenic prebiotic organics |
Extraterrestrial organics: endogenous organics to be expected in hydrothermal fluids, present as finely disseminated particulate matter, as precipitates around hydrothermal silica spheres, or in other forms not yet identified; exogenous (meteoritic/IDPs) and endogenous (hydrothermal) may be present as particulate organics or chelated to mineral substrates; both possibly concentrated by hydraulic processes and associated with fine-grained sediments |
In anaerobic matrices, e.g., fine-grained sediments, mineral cements, or chelated to phyllosilicates |
In situ in a rock or in a portion of carbonaceous rock that has been transported or ejected from elsewhere |
Microscopic but may be macroscopic if the organic components have been hydraulically concentrated or if there was sufficient energy to support a huge biomass, e.g., in the vicinity of hydrothermal activity |