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While features of some ancient apparent stromatolites are suggestive of biological activity, others possess features that are more consistent with abiotic (non-biological) precipitation. [17] Finding reliable ways to distinguish between biologically formed and abiotic stromatolites is an active area of research in geology.
The stromatolites found today are almost all carbonate rocks (made of limestone), but these structures are mostly composed of the minerals gypsum and halite (rock salt), Hynek said.
Collenia are stromatolites made up of convex layers flattened in the center, forming columnar colonies. The microorganisms involved were likely photosynthetic bacteria expiring oxygen. The microorganisms involved were likely photosynthetic bacteria expiring oxygen.
Stromatolites are alternating layers of cyanobacteria and sediments. The grain size of sediment portion of stromatolites is affected by the depositional environment. During the Proterozoic, stromatolites' compositions were dominated by micrite and thinly laminated lime mud, with thicknesses no greater than 100 microns. [3]
Most archean stromatolites older than 3.0 Ga are found in Australia or South Africa. Stratiform stromatolites from the Pilbara Craton have been identified in the 3.47 Ga Mount Ada Basalt. [ 59 ] Barberton, South Africa hosts stratiform stromatolites in the 3.46 Hooggenoeg, 3.42 Kromberg and 3.33 Ga Mendon Formations of the Onverwacht Group .
Stromatolites are formed by some microbial mats as the microbes slowly move upwards to avoid being smothered by sediment. Microbial mats may also be referred to as algal mats and bacterial mats. They are a type of biofilm that is large enough to see with the naked eye and robust enough to survive moderate physical stresses.
Stromatolites typically consist of filamentous microfossils. [17] The oldest stromatolites have been dated to approximately 3.5 billion years old. [18] Stromatolites in Barberton have been dated to about 3.3 billion years. Microfossils found in chert extend the Barberton microfossil record back to 3.5 billion years. All three types of ...
Along with standard biological evolution, life and planet co-evolve. Since the best adaptations are those that suit the ecological niche that the organism lives in, the physical and chemical characteristics of the environment drive the evolution of life by natural selection, but the opposite can also be true: with every advent of evolution, the ...