cratones

Cratones are a term used in the study of microbial mats and stromatolites to describe the cohesive, mucilaginous layer produced by cyanobacteria and other microorganisms that binds sediment grains together. In palaeoenvironmental research, cratones are identified as the organic-rich matrix within or beneath stromatolitic laminae and are important for understanding early life and sedimentary diagenesis.

The cratone is rich in extracellular polymeric substances produced by microbes. This matrix traps and binds fine grains, enabling the development of layered micritic textures observed in stromatolites. The layer can host fossilized microbial filaments and preserve geochemical signals, making it useful for interpreting ancient environments.

Modern cratones are observed in shallow, microbially mediated carbonate settings, such as solar- or hypersaline lagoons, saline mats, and some freshwater springs. Fossil cratones appear in ancient stromatolites from the Precambrian to the Paleozoic, providing a key proxy for microbial activity in ancient seas.

The cratone provides structural cohesion to the microbial mat, protects cells from environmental stress, and influences mineral precipitation and diagenetic pathways. Its preservation potential makes cratones valuable for interpreting early Earth environments and potential biosignatures.

See also: Stromatolite, microbialite, extracellular polymeric substances, cyanobacteria, diagenesis.