Stromatolite fossil dating
Bioherms, biogenic reefs constructed from limestone produced by shelled animals, became prominent by 570 million years ago.During the mid-Triassic, the Jurassic and early Cretaceous periods (roughly 200–100 million years ago), scleractinian corals had become significant components of coral–algal–sponge bioherms.The oldest fossils ever discovered have been found in Greenland, and they appear to have preserved the earliest signs of life of Earth.Dated to around 3.7 billion years ago, the fossils contain evidence of stromatolites - layers of sediment packed together by ancient, water-based bacterial colonies - and could push back the origins of life in the fossil record by 220 million years.Some of these corals may have included zooxanthellae.However, by the mid-Cretaceous, rudist bivalves dominated shallow-water reefs, and scleractinian corals were mainly restricted to deeper shelf-slope environments.The cyanobacteria have been tremendously important in shaping the environment and the course of evolution throughout Earth's history.
With time, the endosymbionts became the eukaryotic chloroplast. Cyanobacteria are quite sophisticated life-forms, which utilize photosynthesis, RNA, and oxidative phosphorylation.The Earth had to cool down from its creation to permit life-forms to exist, that limits us to about 4.2 BYA, or to 4.2–3.5 BYA for simple life to have started Structural coral reefs are forms of ‘biogenic reefs,’ distinct geomorphological structures constructed by living organisms.Biogenic reefs have existed in various forms since approximately 3.5 billion years ago, at which time cyanobacteria began building ).The fossils, which have been cut away from the rocky outcrop and are now under analysis in Australia, contain tiny cones, just 1 to 4 centimetres tall, and the researchers say their structures and internal layering look exactly like other ancient and modern stromatolites."The texture of the surrounding rocks suggests that they were laid down at the bottom of a shallow sea, much as stromatolites are today in places such as the Bahamas and W"And the rocks contain carbonate minerals such as dolomite, which are also common in younger stromatolites."If the team can confirm that these really are the ancient marks of 3.7-billion-year-organisms, it’s going to make life difficult for those tasked with explaining how evolution could have produced such relatively complex organisms so early on in Earth’s lifespan.To have had time to evolve into organisms associated with stromatolites formations, Nutman and his team suggest that life on Earth would have likely originated during the Hadean stage of our planet’s history, which runs from Earth’s formation around 4.65 billion years ago - when debris in orbit around the Sun accumulated into our planet - to around 4 billion years ago."[E]ven when the Hadean ended, a final rain of large asteroids descended on Earth at the beginning of the ensuing Archaean stage, possibly set loose when the giant planets Saturn, Uranus, and Neptune drifted out into the Kuiper belt of asteroids," says Wade."This cataclysm, known as the Late Heavy Bombardment, hit Earth between 3.9 and 3.8 billion years ago."So how did life evolve through all of this chaos?