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The Hadean eon was succeeded by the Archean eon, with the Late Heavy Bombardment hypothesized to have occurred at the Hadean-Archean boundary. Hadean rocks are very rare, largely consisting of granular zircons from one locality in Western Australia. [7] Hadean geophysical models remain controversial among geologists: plate tectonics and the ...
No numerical upper age limits were provided, only the younger age limit of ~4.5 Ga for the boundary between the proposed Chaotian and Hadean boundary. The revised proposal in 2012 did not subdivide the proposed Chaotian era (of the Hadean eon) into periods.
In particular, it is sometimes found that the Hadean eon is subdivided into the Cryptic era and Basin Groups 1-9 (which collectively make up the Pre-Nectarian), and the Nectarian and Lower Imbrian. The first lifeforms (self replicating RNA molecules, see RNA world hypothesis ) may have evolved on earth around 4 bya during this era.
The eon's lower boundary or starting point of 4,031±3 million years ago is officially recognized by the International Commission on Stratigraphy, [1] which is the age of the oldest known intact rock formations on Earth. Evidence of rocks from the preceding Hadean Eon are therefore restricted by definition to non-rock and non-terrestrial ...
In the 19th century, the boundary was set at time of appearance of the first abundant animal fossils, but trace fossils of several hundred groups of complex soft-bodied metazoa from the preceding Ediacaran period of the Proterozoic eon, known as the Avalon Explosion, have been identified since the systematic study of those forms started in the ...
Hadean zircon is the oldest-surviving crustal material from the Earth's earliest geological time period, the Hadean eon, about 4 billion years ago. Zircon is a mineral that is commonly used for radiometric dating because it is highly resistant to chemical changes and appears in the form of small crystals or grains in most igneous and metamorphic host rocks.
Quartz-pebble metaconglomerate (Jack Hills Quartzite), the rock type that contains Earth's oldest dated mineral grains (detrital zircon) Detrital zircons with ages greater than 4 billion years old have been found in these rocks, and a 4,404 ± 8 million year old zircon was found at Erawandoo Hill; [4] this is the oldest dated material originating on Earth; the date is in the Cryptic era of the ...
The Eoarchaean's lower boundary or starting point of 4.031 Gya (4031 million years ago) is officially recognized by the International Commission on Stratigraphy. [6] The name comes from two Greek words: eos (dawn) and Archaios (ancient). The first supercontinent candidate Vaalbara appeared around the end of this period at about