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The Archean Eon (IPA: / ɑːr ˈ k iː ə n / ar-KEE-ən, also spelled Archaean or Archæan), in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history, preceded by the Hadean Eon and followed by the Proterozoic. The Archean represents the time period from (million years
These cell-sized prokaryote fossils are seen in the Barberton fossil record in rocks as old as 3.5 billion years. [1] The Barberton Greenstone Belt is an excellent place to study the Archean Earth due to exposed sedimentary and metasedimentary rocks.
Thuchomyces (sometimes mistakenly called “Thucomyces”) is a genus of Archean fossils from the Witwatersrand of South Africa, and is the earliest macroscopic land life known. [1] The generic name derives from thucholite, the carbonaceous material which Thuchomyces is preserved in, and the Ancient Greek word "myces", meaning "fungus".
However, while most scientists accept their biogenicity, abiotic explanations for these fossils cannot be fully discarded due to their hydrothermal depositional environment and debated geochemical evidence. [50] Most archean stromatolites older than 3.0 Ga are found in Australia or
The Isua Greenstone Belt is an Archean greenstone belt in southwestern Greenland, aged between 3.7 and 3.8 billion years. [2] The belt contains variably metamorphosed mafic volcanic and sedimentary rocks, and is the largest exposure of Eoarchaean supracrustal rocks on Earth. [3]
A stromatolite formed by Paleoarchean microbial mats, preserved as a fossil, from Pilbara craton, Western Australia. The geological record from the Paleoarchean era is very limited. Due to deformation and metamorphism, most rocks from the Paleoarchean era cannot provide any useful information.
Some Archean rock formations show macroscopic similarity to modern microbial structures, leading to the inference that these structures represent evidence of ancient life, namely stromatolites. However, others regard these patterns as being the result of natural material deposition or some other abiogenic mechanism.
The Warrawoona Group is a geological unit in Western Australia containing putative fossils of cyanobacteria cells. Dated 3.465 Ga, these microstructures, found in Archean chert, are considered to be the oldest known geological record of life on Earth. [1] [2] [3]