Period:PrecambrianAge: 2.4 - 2.2 billion yearsRegion:Michigan, USAThis stromatolite, one of the oldest-known microfossils in the fossil records, was found in Michigan in the United States of America.This stromatolite fossil, some 2.4 billion years old, is a member of the cyanobacteria colonies, the oldest-known micro-organisms of Earth. Examination of stromatolites provides valuable information about the climate, geology, biodiversity and geography of the Earth billions of years in the past. Layers gradually form as calcium carbonate (limestone) builds up on the fibers of growing bacteria. Bacteria initiate this build-up by making photosynthesis using carbon dioxide from the water around.Particles and mineral dissolved in the water are trapped in the adhesive fluid surrounding the bacteria and continue to produce new strata by growing upward.This process is repeated over and over again, and sedimentary layers form. The process is still continuing today.Fossilized stromatolites dating back 3.9 billion years can be found in the sedimentary layers on all continents.
