Stromatolites dating method
In this photo provided by Laure Gauthiez, taken in July 2012, a field team examine rocks in Greenland.Scientists have found what they think is the oldest fossil on Earth, a remnant of life from 3.7 billion years ago when Earth's skies were orange and its oceans green.By the close of the Proterozoic, the abundance of stromatolites decreased markedly, though cyanobacteria continued to leave a fossil record, such as Langiella and Kidstoniella known from the Lower Devonian Rhynie chert. The cyanobacteria have also been tremendously important in shaping the course of evolution and ecological change throughout earth's history. Scientist Olivia Judson provides this good example of what happens to an adult male gorilla in the tropical rainforests of the Congo; "An adult male gorilla— all 330 pounds of him—will be reduced to a pile of bones and hair within 10 days of his death. What scavengers like vultures and hyenas leave behind, flies, ants, worms, and bacteria quickly consume.Scientists had thought it would take at least half a billion years for life to form after the molten Earth started to cool a bit, but this shows it could have happened quicker, he said.
Fossils, by definition, are the remains or traces of organisms that lived at least 10,000 years ago.Stromatolites or stromatoliths are defined (Riding 2007) as layered accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by layers of microorganisms, especially cyanobacteria (commonly known as blue-green algae).Stromatolites provide some of the most ancient records of life on Earth.All life-forms were long assumed to have originated in the Cambrian, and therefore all earlier rocks were grouped together into the Precambrian.Although many varied forms of life evolved and were preserved extensively as rocks, detailed mapping and examination of Precambrian rocks on most continents have revealed that additional primitive life-forms existed as early as about 3.48 billion years ago.
This date marks the end of the Cenozoic Era and the Pleistocene Period on the geologic time scale.