geologic recordthe Eoarchean erathem(pronEng|ˌiːoʊɑrˈkiːən, also spelled Eoarchaean) and the Eoarchean era in the geologic timescalecorrespond to one another in the dual system of classification of rock strata laid down beginning 4000 Ma to 3600 Ma (million years ago).
It was formerly officially unnamed and usually referred to as the first part of the Early Archean (now an obsolescent name) together with the later
Paleoarcheanera. It is the first part of the ArchaeanEon, preceded by the "informal" Hadeaneon, during which the Earth was considered to be essentially molten.
International Commission on Stratigraphycurrently does not recognize the lower boundary of the era which they've provisionally placed at 4000 MA [ [http://www.stratigraphy.org/cheu.pdf Recent ICS provisional chart] ] nor that of the preceding Hadean Eon.
The Eoarchean was followed by the
The name comes from two Greek words: "eos" (dawn) and "archios" (ancient). The first supercontinent
Vaalbaraappeared around the end of this period around 3600 ma. Prokaryoteforms may have evolved from protobiontslate in this era.
Also the oldest rock formation on earth the
Isua greenstone beltalso appeared during the Eoarchean around 3.8 Billion years ago.
Notes, links and references
* [http://database.stratigraphy.net/zone_info.php?zone_id=109&zone_type_id=1&zone_theme_id=100&PHPSESSID=b96bd4624e49ce9804f5bbb370a1e4f1 A short fact sheet]
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