How do stromatolites form?

Stromatolites are layered sedimentary formations created mainly by photosynthetic microorganisms like cyanobacteria. These microbes produce adhesive compounds that trap sand and other rocky particles, cementing them into mineralized microbial mats. As these mats build up layer by layer over time, they create the characteristic lamination seen in the rock structures.

What we know

• Stromatolites are formed mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota. [2]
• Microorganisms produce adhesive compounds that cement sand and other rocky materials together to create mineralized microbial mats. [2]
• Microbial mats build up layer by layer, growing gradually over time to generate the characteristic lamination of stromatolites. [2]
• Lichen stromatolites are proposed to form through repeated sequences of rock induration followed by endolithic lichen colonization and weathering. [3] · medium confidence

Still open

• The temporal and environmental significance of different styles of stromatolite lamination remains hard to interpret.

Where to go next

• the bigger pictureWhat are microbial mats?
• how we knowWhat is the Gunflint Chert?
• how it workedHow do cyanobacteria produce oxygen?
• a case in pointHow do endolithic lichens weather rock?
• whenWhen did the earliest life appear on Earth?
• an unexpected connectionHow did ancient rocks help reveal Earth's earliest life?The Gunflint Chert contains biogenic stromatolites with microfossils that were discovered in the 1950s as the earliest known form of life and evidence for photosynthesis at the time.

Sources

• [1]stromatolite (Wikidata Q176739) · CC0 1.0
• [2]Stromatolite · CC BY-SA 4.0
• [3]Lichen stromatolite · CC BY-SA 4.0
• [4]Gunflint chert · CC BY-SA 4.0
• [5]Earth · CC BY-SA 4.0