Stromatolites dating method Secretsexyoung
"The significance of stromatolites is that not only do they provide obvious evidence of ancient life that is visible with the naked eye, but that they are complex ecosystems," said Professor Allen Nutman of the University of Wollongong, and leader of the team.
"This indicates that as long as 3.7 billion years ago microbial life was already diverse.
This definition is, in fact, such a gross oversimplification as be scientifically useless.
The oldest known fossils, in fact, are cyanobacteria from Archaean rocks of western Australia, dated 3.5 billion years old.
Within three weeks, there will be nothing left but a few small bones." A fossil normally preserves only a portion of an organism, usually that portion that was partially mineralized during life, such as bones and teeth.
Trace fossils are the marks left by a living organism, such as feces, footprints or impressions of feathers or leaves.
This diversity shows that life emerged within the first few hundred millions years of Earth's existence, which is in keeping with biologists' calculations showing the great antiquity of life's genetic code." Stromatolites (meaning, "layered rock") are slow-growing rigid structures formed by single-celled cyanobacteria microbes (blue-green algae) that trap sediment on their surfaces.
Over very long periods of time the captured sediment reacts with calcium carbonate in sea water to form limestone, which grows at a rate of around 5 cm per 100 years.
A small piece of stromatolites encodes biological activity perhaps spanning thousands of years.
In broad terms, stromatolites are fossil evidence of the prokaryotic life that remains today, as it has always been, the preponderance of biomass in the biosphere.
For those that subscribe to the theory of the living earth, it is the prokaryotes that maintain the homeostasis of the earth, rendering the biosphere habitable for all other life.
Organisms usually need to be covered by mud, sand, tar or some other sediment as soon as possible or frozen or dessicated (dried out) for fossilization to occur.
Fossils, by definition, are the remains or traces of organisms that lived at least 10,000 years ago.