| 초록 | Stromatolites are microbial laminated benthic deposits formed by the trapping and binding of sediments and/or by bio-induced precipitation of minerals. First reported in the early 1800s, stromatolite research has now lasted for almost 200 years. They are the earliest forms of life on Earth and appeared approximately 3.5 billion years ago and still occur on the planet. The relationships between stromatolites and microbes are like that between forests and trees. Modern stromatolites are formed by various organisms, including cyanobacteria, and this is probably also true for ancient stromatolites. A stromatolite itself is therefore not a body fossil, but some fossils of calcified microbes can occur in stromatolites. Stromatolites are a type of microbialite, and can be defined as benthic microbial deposits. Based on their mesostructure (or macrofabric), four major types of microbialites are identified: stromatolite (laminated), thrombolite (clotted), dendrolite (dendritically clotted), and leiolite (aphanitic).
Stromatolite-forming cyanobacteria produced oxygen through photosynthesis and emitted a vast amount of oxygen in the early atmosphere. Stromatolites flourished throughout the Proterozoic but declined in the Neoproterozoic and onwards as atmospheric pCO2 and temperature decreased, resulting in a decrease in the seawater carbonate saturation state as well as cyanobacterial calcification. The Phanerozoic record of stromatolites fluctuated together with several different factors including the abundance of animals, sea-water chemistry, temperature, etc. |
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